Publications:
Complete Listing
Biochim Biophys Acta , 2017; 1868(1):117-122; Rajabi H, and Kufe D.
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The MUC1 gene evolved in mammalian species to provide protection of epithelia. The transmembrane MUC1 C-terminal subunit (MUC1-C) signals stress to the interior of the epithelial cell and, when overexpressed as in most carcinomas, functions as an oncoprotein. MUC1-C induces the epithelial-mesenchymal transition (EMT) by activating the inflammatory NF-κB p65 pathway and, in turn, the EMT-transcriptional repressor ZEB1. Emerging evidence has indicated that MUC1-C drives a program integrating the induction of EMT with activation of stem cell traits, epigenetic reprogramming and immune evasion. This mini-review focuses on the potential importance of this MUC1-C program in cancer progression. KEYWORDS: BMI1; DNMTs; EMT; MUC1-C; PD-L1; epigenetics; immune evasion; tumor suppressor genes
MUC1-C integrates PD-L1 induction with repression of immune effectors in non-small cell lung cancer
Oncogene [In press] , Jan 2017 ; Bouillez A, Rajabi H, Jin C, Samur M, Tagde A, Alam M, Hiraki M, Maeda T, Hu X, Adeegbe D, Kharbanda S, Wong K-K and Kufe D.
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[In press]
Targeting MUC1-C inhibits the AKT-S6K1-elF4A pathway regulating TIGAR translation in colorectal cancer
Molecular Cancer Research , Jan 2017 ; 16(33); Ahmad R, Alam M, Hasegawa M, Uchida Y, Al-Obaid O, Kharbanda S, and Kufe D.
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Colorectal cancer is third most common malignancy and is the second most common cause of cancer-related death. The MUC1 heterodimeric protein is aberrantly overexpressed in colorectal cancer and has been linked to poor outcomes in this disease. Here, we investigate the effects of the MUC1-C subunit inhibitor (GO-203), which disrupts MUC1-C homo-oligomerization, on human colorectal cancer cells.
MUC1-C represses the Crumbs complex polarity factor CRB3 and downregulates the Hippo pathway
Molecular Cancer Research , Dec 2016 ; 14(12):1266-1276; Alam M, Bouillez A, Tagde A, Ahmad R, Rajabi H, Maeda T, Hiraki M, Suzuki Y, and Kufe D.
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Apical–basal polarity and epithelial integrity are maintained in part by the Crumbs (CRB) complex. The C-terminal subunit of MUC1 (MUC1-C) is a transmembrane protein that is expressed at the apical border of normal epithelial cells and aberrantly at high levels over the entire surface of their transformed counterparts. However, it is not known whether MUC1-C contributes to this loss of polarity that is characteristic of carcinoma cells. Here it is demonstrated that MUC1-C downregulates expression of the Crumbs complex CRB3 protein in triple-negative breast cancer (TNBC) cells. MUC1-C associates with ZEB1 on the CRB3 promoter and represses CRB3 transcription. Notably, CRB3 activates the core kinase cassette of the Hippo pathway, which includes LATS1 and LATS2. In this context, targeting MUC1-C was associated with increased phosphorylation of LATS1, consistent with activation of the Hippo pathway, which is critical for regulating cell contact, tissue repair, proliferation, and apoptosis. Also shown is that MUC1-C-mediated suppression of CRB3 and the Hippo pathway is associated with dephosphorylation and activation of the oncogenic YAP protein. In turn, MUC1-C interacts with YAP, promotes formation of YAP/b-catenin complexes, and induces the WNT target gene MYC. These data support a previously unrecognized pathway in which targeting MUC1-C in TNBC cells (i) induces CRB3 expression, (ii) activates the CRB3-driven Hippo pathway, (iii) inactivates YAP, and thereby (iv) suppresses YAP/b-catenin–mediated induction of MYC expression. Implications: These findings demonstrate a previously unrecognized role for the MUC1-C oncoprotein in the regulation of polarity and the Hippo pathway in breast cancer.
MUC1-C activates BMI1 in human cancer cells
Oncogene , 2016; Nov 28 [Epub ahead of print]; Hiraki M, Maeda T, Bouillez A, Alam M, Tagde A, Hinohara K, Suzuki Y, Markert T, Miyo T, Komura K, Ahmad R, Rajabi H, and Kufe D.
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B-cell-specific Moloney murine leukemia virus integration site 1 (BMI1) is a component of the polycomb repressive complex 1 (PRC1) complex that is overexpressed in breast and other cancers, and promotes self-renewal of cancer stem-like cells. The oncogenic mucin 1 (MUC1) C-terminal (MUC1-C) subunit is similarly overexpressed in human carcinoma cells and has been linked to their self-renewal. There is no known relationship between MUC1-C and BMI1 in cancer. The present studies demonstrate that MUC1-C drives BMI1 transcription by a MYC-dependent mechanism in breast and other cancer cells. In addition, we show that MUC1-C blocks miR-200c-mediated downregulation of BMI1 expression. The functional significance of this MUC1-C → BMI1 pathway is supported by the demonstration that targeting MUC1-C suppresses BMI1-induced ubiquitylation of H2A and thereby derepresses homeobox HOXC5 and HOXC13 gene expression. Notably, our results further show that MUC1-C binds directly to BMI1 and promotes occupancy of BMI1 on the CDKN2A promoter. In concert with BMI1-induced repression of the p16INK4a tumor suppressor, we found that targeting MUC1-C is associated with induction of p16INK4a expression. In support of these results, analysis of three gene expresssion data sets demonstrated highly significant correlations between MUC1-C and BMI1 in breast cancers. These findings uncover a previously unrecognized role for MUC1-C in driving BMI1 expression and in directly interacting with this stem cell factor, linking MUC1-C with function of the PRC1 in epigenetic gene silencing.
MUC1-C induces DNA methyltransferase 1 and represses tumor suppressor genes in acute myeloid leukemia
Oncotarget , 2016; 7(26):38974-38987; Tagde A, Rajabi H, Stroopinsky D, Gali R, Alam M, Bouillez A, Kharbanda S, Stone R, Avigan D, and Kufe D.
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Aberrant DNA methylation is a hallmark of acute myeloid leukemia (AML); however, the regulation of DNA methyltransferase 1 (DNMT1), which is responsible for maintenance of DNA methylation patterns, has largely remained elusive. MUC1-C is a transmembrane oncoprotein that is aberrantly expressed in AML stem-like cells. The present studies demonstrate that targeting MUC1-C with silencing or a pharmacologic inhibitor GO-203 suppresses DNMT1 expression. In addition, MUC1 expression positively correlates with that of DNMT1 in primary AML cells, particularly the CD34+/CD38- population. The mechanistic basis for this relationship is supported by the demonstration that MUC1-C activates the NF-κB p65 pathway, promotes occupancy of the MUC1-C/NF-κB complex on the DNMT1 promoter and drives DNMT1 transcription. We also show that targeting MUC1-C substantially reduces gene promoter-specific DNA methylation, and derepresses expression of tumor suppressor genes, including CDH1, PTEN and BRCA1. In support of these results, we demonstrate that combining GO-203 with the DNMT1 inhibitor decitabine is highly effective in reducing DNMT1 levels and decreasing AML cell survival. These findings indicate that (i) MUC1-C is an attractive target for the epigentic reprogramming of AML cells, and (ii) targeting MUC1-C in combination with decitabine is a potentially effective clinical approach for the treatment of AML.
DNA methylation by DNMT1 and DNMT3b methyltransferases is driven by the MUC1-C oncoprotein in human carcinoma cells
Oncogene , 2016; 7(26):38974-38987; Tagde A, Rajabi H, Stroopinsky D, Gali R, Alam M, Bouillez A, Kharbanda S, Stone R, Avigan D, and Kufe D.
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Aberrant expression of the DNA methyltransferases (DNMTs) and disruption of DNA methylation patterns are associated with carcinogenesis and cancer cell survival. The oncogenic MUC1-C protein is aberrantly overexpressed in diverse carcinomas; however, there is no known link between MUC1-C and DNA methylation. Our results demonstrate that MUC1-C induces the expression of DNMT1 and DNMT3b, but not DNMT3a, in breast and other carcinoma cell types. We show that MUC1-C occupies the DNMT1 and DNMT3b promoters in complexes with NF-κB p65 and drives DNMT1 and DNMT3b transcription. In this way, MUC1-C controls global DNA methylation as determined by analysis of LINE-1 repeat elements. The results further demonstrate that targeting MUC1-C downregulates DNA methylation of the CDH1 tumor suppressor gene in association with induction of E-cadherin expression. These findings provide compelling evidence that MUC1-C is of functional importance to induction of DNMT1 and DNMT3b and, in turn, changes in DNA methylation patterns in cancer cells.
MUC1-C stabilizes MCL-1 in the oxidative stress response of triple-negative breast cancer cells to BCL-2 inhibitors
Scientific Reports , 2016; 6(Article 26643); Hiraki M, Suzuki Y, Alam M, Hinohara K, Hasegawa M, Jin C, Kharbanda S, and Kufe D.
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Aberrant expression of myeloid cell leukemia-1 (MCL-1) is a major cause of drug resistance in triple-negative breast cancer (TNBC) cells. Mucin 1 (MUC1) is a heterodimeric oncoprotein that is aberrantly overexpressed in most TNBC. The present studies show that targeting the oncogenic MUC1 C-terminal subunit (MUC1-C) in TNBC cells with silencing or pharmacologic inhibition with GO-203 is associated with downregulation of MCL-1 levels. Targeting MUC1-C suppresses the MEK→ERK and PI3K→AKT pathways, and in turn destabilizes MCL-1. The small molecules ABT-737 and ABT-263 target BCL-2, BCL-XL and BCL-w, but not MCL-1. We show that treatment with ABT-737 increases reactive oxygen species and thereby MUC1-C expression. In this way, MUC1-C is upregulated in TNBC cells resistant to ABT-737 or ABT-263. We also demonstrate that MUC1-C is necessary for the resistance-associated increases in MCL-1 levels. Significantly, combining GO-203 with ABT-737 is synergistic in inhibiting survival of parental and drug resistant TNBC cells. These findings indicate that targeting MUC1-C is a potential strategy for reversing MCL-1-mediated resistance in TNBC.
Functional interactions of the cystine/glutamate antiporter, CD44v and MUC1-C oncoprotein in triple-negative breast cancer cells
Oncotarget , 2016; 7(11):11756-11769; Hasegawa M, Takahashi H, Rajabi H, Alam M, Suzuki Y, Yin L, Tagde A, Maeda T, Hiraki M, Sukhatme V, and Kufe D.
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The xCT light chain of the cystine/glutamate transporter (system XC-) is of importance for the survival of triple-negative breast cancer (TNBC) cells. The MUC1-C transmembrane oncoprotein is aberrantly overexpressed in TNBC and, like xCT, has been linked to maintaining glutathione (GSH) levels and redox balance. However, there is no known interaction between MUC1-C and xCT. Here we show that silencing MUC1-C is associated with decreases in xCT expression in TNBC cells. The results demonstrate that MUC1-C forms a complex with xCT and the CD44 variant (CD44v), which interacts with xCT and thereby controls GSH levels. MUC1-C binds directly with CD44v and in turn promotes stability of xCT in the cell membrane. The interaction between MUC1-C and xCT is further supported by the demonstration that targeting xCT with silencing or the inhibitor sulfasalazine suppresses MUC1 gene transcription by increasing histone and DNA methylation on the MUC1 promoter. In terms of the functional significance of the MUC1-C/xCT interaction, we show that MUC1-C protects against treatment with erastin, an inhibitor of XC- and inducer of ferroptosis, a form of non-apoptotic cell death. These findings indicate that targeting this novel MUC1-C/xCT pathway could represent a potential therapeutic approach for promoting TNBC cell death.
Inhibition of MUC1-C suppresses MYC expression and attenuates malignant growth in KRAS mutant lung adenocarcinomas
Cancer Research , 2016; 76(6):1538-1548; Bouillez A, Rajabi H, Pitroda S, Jin C, Alam M, Kharbanda A, Tagde A, Wong K, and Kufe D.
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Dysregulation of MYC expression is a hallmark of cancer, but the development of agents that target MYC has remained challenging. The oncogenic MUC1-C transmembrane protein is, like MYC, aberrantly expressed in diverse human cancers. The present studies demonstrate that MUC1-C induces MYC expression in KRAS mutant non-small cell lung cancer (NSCLC) cells, an effect that can be suppressed by targeting MUC1-C via shRNA silencing, CRISPR editing, or pharmacologic inhibition with GO-203. MUC1-C activated the WNT/β-catenin (CTNNB1) pathway and promoted occupancy of MUC1-C/β-catenin/TCF4 complexes on the MYC promoter. MUC1-C also promoted the recruitment of the p300 histone acetylase (EP300) and, in turn, induced histone H3 acetylation and activation of MYC gene transcription. We also show that targeting MUC1-C decreased the expression of key MYC target genes essential for the growth and survival of NSCLC cells, such as TERT and CDK4. Based on these results, we found that the combination of GO-203 and the BET bromodomain inhibitor JQ1, which targets MYC transcription, synergistically suppressed MYC expression and cell survival in vitro as well as tumor xenograft growth. Furthermore, MUC1 expression significantly correlated with that of MYC and its target genes in human KRAS mutant NSCLC tumors. Taken together, these findings suggest a therapeutic approach for targeting MYC-dependent cancers and provide the framework for the ongoing clinical studies addressing the efficacy of MUC1-C inhibition in solid tumors. Cancer Res; 76(6); 1538-48. ©2016 AACR.
MUC1-C drives MYC in multiple myeloma
Blood , 2016; 127(21):2587-2597; Tagde A, Rajabi H, Bouillez A, Alam M, Gali R, Bailey S, Tai YT, Hideshima T, Anderson K, Avigan D, and Kufe D.
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Multiple myeloma (MM) cell lines and primary tumor cells are addicted to the MYC oncoprotein for survival. Little is known, however, about how MYC expression is upregulated in MM cells. The mucin 1 C-terminal subunit (MUC1-C) is an oncogenic transmembrane protein that is aberrantly expressed in MM cell lines and primary tumor samples. The present studies demonstrate that targeting MUC1-C with silencing by CRISPR/Cas9 editing or with the GO-203 inhibitor is associated with downregulation of MYC mRNA and protein. The results show that MUC1-C occupies the MYC promoter and thereby activates the MYC gene by a β-catenin/TCF4-mediated mechanism. In this way, MUC1-C (i) increases β-catenin occupancy on the MYC promoter, (ii) forms a complex with β-catenin and TCF4, and, in turn, (iii) drives MYC transcription. Analysis of MM cells using qRT-PCR arrays further demonstrated that silencing MUC1-C is associated with downregulation of MYC target genes, including CCND2, hTERT and GCLC. Analysis of microarray datasets further demonstrated that MUC1 levels positively correlate with MYC expression in MM progression and in primary cells from over 800 MM patients. These findings collectively provide convincing evidence that MUC1-C drives MYC expression in MM.
MUC1-C activates the TAK1 inflammatory pathway in colon cancer
Oncogene , 2015; 34(40):5187-5197; Takahashi H, Jin C, Rajabi H, Pitroda S, Alam M, Ahmad R, Raina D, Hasegawa M, Suzuki Y, Tagde A, Bronson RT, Weichselbaum R, and Kufe D.
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The mucin 1 (MUC1) oncoprotein has been linked to the inflammatory response by promoting cytokine-mediated activation of the NF-κB pathway. The TGF-β-activated kinase 1 (TAK1) is an essential effector of proinflammatory NF-κB signaling that also regulates cancer cell survival. The present studies demonstrate that the MUC1-C transmembrane subunit induces TAK1 expression in colon cancer cells. MUC1 also induces TAK1 in a MUC1(+/-)/IL-10(-/-) mouse model of colitis and colon tumorigenesis. We show that MUC1-C promotes NF-κB-mediated activation of TAK1 transcription and, in a positive regulatory loop, MUC1-C contributes to TAK1-induced NF-κB signaling. In this way, MUC1-C binds directly to TAK1 and confers the association of TAK1 with TRAF6, which is necessary for TAK1-mediated activation of NF-κB. Targeting MUC1-C thus suppresses the TAK1NF-κB pathway, downregulates BCL-XL and in turn sensitizes colon cancer cells to MEK inhibition. Analysis of colon cancer databases further indicates that MUC1, TAK1 and TRAF6 are upregulated in tumors associated with decreased survival and that MUC1-C-induced gene expression patterns predict poor outcomes in patients. These results support a model in which MUC1-C-induced TAK1NF-κB signaling contributes to intestinal inflammation and colon cancer progression.
Characterization of the MUC1-C cytoplasmic domain as a cancer target
PLoS One , 2015; 10(8):e0135156; Raina D, Agarwal P, Lee J, Bharti A, McKnight C, Sharma P, Kharbanda S, and Kufe D.
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Mucin 1 (MUC1) is a heterodimeric protein that is aberrantly expressed in diverse human carcinomas and certain hematologic malignancies. The oncogenic MUC1 transmembrane C-terminal subunit (MUC1-C) functions in part by transducing growth and survival signals from cell surface receptors. However, little is known about the structure of the MUC1-C cytoplasmic domain as a potential drug target. Using methods for structural predictions, our results indicate that a highly conserved CQCRRK sequence, which is adjacent to the cell membrane, forms a small pocket that exposes the two cysteine residues for forming disulfide bonds. By contrast, the remainder of the MUC1-C cytoplasmic domain has no apparent structure, consistent with an intrinsically disordered protein. Our studies thus focused on targeting the MUC1 CQCRRK region. The results show that L- and D-amino acid CQCRRK-containing peptides bind directly to the CQC motif. We further show that the D-amino acid peptide, designated GO-203, blocks homodimerization of the MUC1-C cytoplasmic domain in vitro and in transfected cells. Moreover, GO-203 binds directly to endogenous MUC1-C in breast and lung cancer cells. Colocalization studies further demonstrate that GO-203 predominantly binds to MUC1-C at the cell membrane. These findings support the further development of agents that target the MUC1-C cytoplasmic domain CQC motif and thereby MUC1-C function in cancer cells.
Mucin 1 is a potential therapeutic target in cutaneous T-cell lymphoma
Blood , 2015; 126(3):354-362; Jain S, Stroopinsky D, Yin L, Rosenblatt J, Alam M, Bhargava P, Clark RA, Kupper TS, Palmer K, Coll MD, Rajabi H, Pyzer A, Bar-Natan M, Luptakova K, Arnason J, Joyce R, Kufe D, and Avigan D..
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Cutaneous T-cell lymphoma (CTCL) is an aggressive neoplasm with limited treatments for patients with advanced disease. The mucin 1 C-terminal subunit (MUC1-C) oncoprotein plays a critical role in regulating cell proliferation, apoptosis, and protection from cytotoxic injury mediated by reactive oxygen species (ROS). Although CTCL cells exhibit resistance to ROS-induced apoptosis, the expression and functional significance of MUC1 in CTCL have not been previously investigated. Present studies demonstrate that MUC1-C is overexpressed in CTCL cell lines and primary CTCL cells but is absent in resting T cells from healthy donors and B-cell lymphoma cells. We have developed a cell-penetrating peptide that disrupts homodimerization of the MUC1-C subunit necessary for its nuclear translocation and downstream signaling. We show that treatment of CTCL cells with the MUC1-C inhibitor is associated with downregulation of the p53-inducible regulator of glycolysis and apoptosis and decreases in reduced NAD phosphate and glutathione levels. In concert with these results, targeting MUC1-C in CTCL cells increased ROS and, in turn, induced ROS-mediated late apoptosis/necrosis. Targeting MUC1-C in CTCL tumor xenograft models demonstrated significant decreases in disease burden. These findings indicate that MUC1-C maintains redox balance in CTCL cells and is thereby a novel target for the treatment of patients with CTCL.
Intracellular targeting of the oncogenic MUC1-C protein with a novel GO-203 nanoparticle formulation
Clinical Cancer Research , 2015; 21(10):2338-2347; Hasegawa M, Sinha RK, Kumar M, Alam M, Yin L, Raina D, Kharbanda A, Panchamoorthy G, Gupta D, Singh H, Kharbanda S, and Kufe D.
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PURPOSE:
The MUC1-C oncoprotein is an intracellular target that is druggable with cell-penetrating peptide inhibitors. However, development of peptidyl drugs for treating cancer has been a challenge because of unfavorable pharmacokinetic parameters and limited cell-penetrating capabilities.
EXPERIMENTAL DESIGN:
Encapsulation of the MUC1-C inhibitor GO-203 in novel polymeric nanoparticles was studied for effects on intracellular targeting of MUC1-C signaling and function.
RESULTS:
Our results show that loading GO-203 into tetrablock polylactic acid (PLA)-polyethylene glycol (PEG)-polypropylene glycol (PPG)-PEG copolymers is achievable and, notably, is enhanced by increasing PEG chain length. In addition, we found that release of GO-203 from these nanoparticles is controllable over at least 7 days. GO-203/nanoparticle treatment of MUC1-C-positive breast and lung cancer cells in vitro was more active with less frequent dosing than that achieved with nonencapsulated GO-203. Moreover, treatment with GO-203/nanoparticles blocked MUC1-C homodimerization, consistent with on-target effects. GO-203/nanoparticle treatment was also effective in downregulating TIGAR, disrupting redox balance, and inhibiting the self-renewal capacity of cancer cells. Significantly, weekly administration of GO-203/nanoparticles to mice bearing syngeneic or xenograft tumors was associated with regressions that were comparable with those found when dosing on a daily basis with GO-203.
CONCLUSIONS:
These findings thus define an effective approach for (i) sustained administration of GO-203 in polymeric PLA-(PEG-PPG-PEG) nanoparticles to target MUC1-C in cancer cells and (ii) the potential delivery of other anticancer peptide drugs.
Targeting the oncogenic MUC1-C protein inhibits mutant EGFR-mediated signaling and survival in non-small cell lung cancer cells
Clinical Cancer Research , 2014; 20(21):5423-5434; Kharbanda A, Rajabi H, Jin C, Tchaicha J, Kikuchi E, Wong K, and Kufe D.
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PURPOSE:
Non-small cell lung cancers (NSCLC) that express EGF receptor with activating mutations frequently develop resistance to EGFR kinase inhibitors. The mucin 1 (MUC1) heterodimeric protein is aberrantly overexpressed in NSCLC cells and confers a poor prognosis; however, the functional involvement of MUC1 in mutant EGFR signaling is not known.
EXPERIMENTAL DESIGN:
Targeting the oncogenic MUC1 C-terminal subunit (MUC1-C) in NSCLC cells harboring mutant EGFR was studied for effects on signaling, growth, clonogenic survival, and tumorigenicity.
RESULTS:
Stable silencing of MUC1-C in H1975/EGFR(L858R/T790M) cells resulted in downregulation of AKT signaling and inhibition of growth, colony formation, and tumorigenicity. Similar findings were obtained when MUC1-C was silenced in gefitinib-resistant PC9GR cells expressing EGFR(delE746_A750/T790M). The results further show that expression of a MUC1-C(CQC → AQA) mutant, which blocks MUC1-C homodimerization, suppresses EGFR(T790M), AKT and MEK → ERK activation, colony formation, and tumorigenicity. In concert with these results, treatment of H1975 and PC9GR cells with GO-203, a cell-penetrating peptide that blocks MUC1-C homodimerization, resulted in inhibition of EGFR, AKT, and MEK → ERK signaling and in loss of survival. Combination studies of GO-203 and afatinib, an irreversible inhibitor of EGFR, further demonstrate that these agents are synergistic in inhibiting growth of NSCLC cells harboring the activating EGFR(T790M) or EGFR(delE746-A750) mutants.
CONCLUSIONS:
These findings indicate that targeting MUC1-C inhibits mutant EGFR signaling and survival, and thus represents a potential approach alone and in combination for the treatment of NSCLCs resistant to EGFR kinase inhibitors.
MUC1-C confers EMT and KRAS independence in mutant KRAS lung cancer cells
Oncotarget , 2014; 5(19):8893-8905; Kharbanda A, Rajabi H, Jin C, Alam M, Wong K, and Kufe D.
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Non-small cell lung cancers (NSCLCs) that harbor an oncogenic KRAS mutation are often associated with resistance to targeted therapies. The MUC1-C transmembrane protein is aberrantly overexpressed in NSCLCs and confers a poor outcome; however, the functional role for MUC1-C in mutant KRAS NSCLC cells has remained unclear. The present studies demonstrate that silencing MUC1-C in A549/KRAS(G12S) and H460/KRAS(Q61H) NSCLC cells is associated with downregulation of AKT signaling and inhibition of growth. Overexpression of a MUC1-C(CQC→AQA) mutant, which inhibits MUC1-C homodimerization and function, suppressed both AKT and MEK activation. Moreover, treatment with GO-203, an inhibitor of MUC1-C homodimerization, blocked AKT and MEK signaling and decreased cell survival. The results further demonstrate that targeting MUC1-C suppresses expression of the ZEB1 transcriptional repressor by an AKT-mediated mechanism, and in turn induces miR-200c. In concert with these effects on the ZEB1/miR-200c regulatory loop, targeting MUC1-C was associated with reversal of the epithelial-mesenchymal transition (EMT) and inhibition of self-renewal capacity. Loss of MUC1-C function also attenuated KRAS independence and inhibited growth of KRAS mutant NSCLC cells as tumors in mice. These findings support a model in which targeting MUC1-C inhibits mutant KRAS signaling in NSCLC cells and thereby reverses the EMT phenotype and decreases self-renewal.
Targeting the MUC1-C oncoprotein downregulates HER2 activation and abrogates trastuzumab resistance in breast cancer cells
Oncogene , 2014; 33(26):3422-3431; Raina D, Uchida Y, Kharbanda A, Rajabi H, Panchamoorthy G, Jin C, Kharbanda S, Scaltriti M, Baselga J, and Kufe D.
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Patients with HER2-positive breast cancer often exhibit intrinsic or acquired resistance to trastuzumab treatment. The transmembrane mucin 1 (MUC1) oncoprotein is aberrantly overexpressed in breast cancer cells and associates with HER2. The present studies demonstrate that silencing MUC1 C-terminal subunit (MUC1-C) in HER2-overexpressing SKBR3 and BT474 breast cancer cells results in the downregulation of constitutive HER2 activation. Moreover, treatment with the MUC1-C inhibitor, GO-203, was associated with disruption of MUC1-C/HER2 complexes and decreases in tyrosine-phosphorylated HER2 (p-HER2) levels. In studies of trastuzumab-resistant SKBR3R and BT474R cells, we found that the association between MUC1-C and HER2 is markedly increased (∼20-fold) as compared with that in sensitive cells. In addition, silencing MUC1-C in the trastuzumab-resistant cells or treatment with GO-203 decreased p-HER2 and AKT activation. Moreover, targeting MUC1-C was associated with the downregulation of phospho-p27 and cyclin E, which confer trastuzumab resistance. Consistent with these results, targeting MUC1-C inhibited the growth and clonogenic survival of both trastuzumab-resistant cells. Our results further demonstrate that silencing MUC1-C reverses resistance to trastuzumab and that the combination of GO-203 and trastuzumab is highly synergistic. These findings indicate that MUC1-C contributes to constitutive activation of the HER2 pathway and that targeting MUC1-C represents a potential approach to abrogate trastuzumab resistance.
Targeting MUC1-C is synergistic with bortezomib in downregulating TIGAR and inducing ROS-mediated myeloma cell death
Blood , 2014; 123(19):2997-3006; Yin L, Kufe T, Avigan D, and Kufe D.
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The proteosome inhibitor bortezomib (BTZ) induces endoplasmic reticulum and oxidative stress in multiple myeloma (MM) cells. The mucin 1 C-terminal subunit (MUC1-C) oncoprotein is aberrantly expressed in most MM cells, and targeting MUC1-C with GO-203, a cell-penetrating peptide inhibitor of MUC1-C homodimerization, is effective in inducing reactive oxygen species (ROS)-mediated MM cell death. The present results demonstrate that GO-203 and BTZ synergistically downregulate expression of the p53-inducible regulator of glycolysis and apoptosis (TIGAR), which promotes shunting of glucose-6-phosphate into the pentose phosphate pathway to generate reduced glutathione (GSH). In turn, GO-203 blocks BTZ-induced increases in GSH and results in synergistic increases in ROS and MM cell death. The results also demonstrate that GO-203 is effective against BTZ-resistant MM cells. We show that BTZ resistance is associated with BTZ-induced increases in TIGAR and GSH levels, and that GO-203 resensitizes BTZ-resistant cells to BTZ treatment by synergistically downregulating TIGAR and GSH. The GO-203/BTZ combination is thus highly effective in killing BTZ-resistant MM cells. These findings support a model in which targeting MUC1-C is synergistic with BTZ in suppressing TIGAR-mediated regulation of ROS levels and provide an experimental rationale for combining GO-203 with BTZ in certain settings of BTZ resistance.
Targeting the MUC1-C oncoprotein inhibits self-renewal capacity of breast cancer cells
Oncotarget , 2014; 5(9):2622-2634; Alam M, Rajabi H, Ahmad R, Jin C, and Kufe D.
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The capacity of breast cancer cells to form mammospheres in non-adherent serum-free culture is used as a functional characteristic of the self-renewing stem-like cell population. The present studies demonstrate that silencing expression of the MUC1-C oncoprotein inhibits growth of luminal MCF-7 and HER2-overexpressing SKBR3 breast cancer cells as mammospheres. We also show that triple-negative MDA-MB-468 breast cancer cells are dependent on MUC1-C for growth as mammospheres and tumor xenografts. Similar results were obtained when MUC1-C function was inhibited by expression of a MUC1-C(CQC->AQA) mutant. Moreover, treatment with the MUC1-C inhibitor GO-203, a cell penetrating peptide that binds to the MUC1-C cytoplasmic domain and blocks MUC1-C function, confirmed the importance of this target for self-renewal. The mechanistic basis for these findings is supported by the demonstration that MUC1-C activates NF-κB, occupies the IL-8 promoter with NF-κB, and induces IL-8 transcription. MUC1-C also induces NF-κB-dependent expression of the IL-8 receptor, CXCR1. In concert with these results, targeting MUC1-C with GO-203 suppresses IL-8/CXCR1 expression and disrupts the formation of established mammospheres. Our findings indicate that MUC1-C contributes to the self-renewal of breast cancer cells by activating the NF-κB->IL-8/CXCR1 pathway and that targeting MUC1-C represents a potential approach for the treatment of this population.
MUC1-C oncoprotein activates the ZEB1/miR-200c regulatory loop and epithelial-mesenchymal transition
Oncogene , 2014; 33(13):1680-1689; Rajabi H, Alam M, Takahashi H, Kharbanda A, Guha M, Ahmad R, and Kufe D.
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The epithelial-mesenchymal transition (EMT) is activated in cancer cells by ZEB1, a member of the zinc finger/homeodomain family of transcriptional repressors. The mucin 1 (MUC1) heterodimeric protein is aberrantly overexpressed in human carcinoma cells. The present studies in breast cancer cells demonstrate that the oncogenic MUC1-C subunit induces expression of ZEB1 by a NF-κB (nuclear factor kappa B) p65-dependent mechanism. MUC1-C occupies the ZEB1 promoter with NF-κB p65 and thereby promotes ZEB1 transcription. In turn, ZEB1 associates with MUC1-C and the ZEB1/MUC1-C complex contributes to the transcriptional suppression of miR-200c, an inducer of epithelial differentiation. The co-ordinate upregulation of ZEB1 and suppression of miR-200c has been linked to the induction of EMT. In concert with the effects of MUC1-C on ZEB1 and miR-200c, we show that MUC1-C induces EMT and cellular invasion by a ZEB1-mediated mechanism. These findings indicate that (i) MUC1-C activates ZEB1 and suppresses miR-200c with the induction of EMT and (ii) targeting MUC1-C could be an effective approach for the treatment of breast and possibly other types of cancers that develop EMT properties.
MUC1-C oncoprotein promotes FLT3 receptor activation in acute myeloid leukemia cells
Blood , 2014; 123(5):734-742; Liu S, Yin L, Stroopinsky D, Rajabi H, Puissant A, Stegmaier K, Avigan D, Kharbanda S, Kufe D, and Stone R.
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Blasts from approximately one-third of patients with acute myeloid leukemia (AML) harbor activating mutations in the FMS-like tyrosine kinase 3 (FLT3) receptor tyrosine kinase that confer a poor prognosis. The Mucin 1-C-terminal subunit (MUC1-C) oncoprotein is aberrantly expressed in AML blasts and stem cells; however, there is no known interaction between MUC1-C and FLT3. The present studies demonstrate that MUC1-C associates with wild-type and mutant FLT3 in AML cells. Targeting MUC1-C with the cell-penetrating peptide inhibitor GO-203 disrupts MUC1-C/FLT3 complexes and downregulates FLT3 activation. GO-203 treatment of AML cells was also associated with inhibition of the FLT3 downstream effectors AKT, extracellular signal-regulated kinase, and STAT5. The results further show that AML cells with FLT3-activating mutations and resistant to the FLT3 inhibitor midostaurin/PKC412 are sensitive to GO-203-induced growth arrest and death. Moreover, GO-203 increases sensitivity of mutant FLT3 AML cells to FLT3 inhibitor treatment. These results indicate that MUC1-C contributes to FLT3 activation in AML cells and that targeting MUC1-C inhibits the FLT3 signaling pathway. Our findings support the development of MUC1-C inhibitors alone and in combination with agents that target FLT3 for the treatment of wild-type and mutant FLT3 AML.
MUC1-C oncoprotein activates ERK→C/EBPβ signaling and induction of aldehyde dehydrogenase 1A1 in breast cancer cells
J Biological Chemistry , 2013; 288(43):30829-30903; Alam M, Ahmad R, Rajabi H, Kharbanda A, and Kufe D.
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Aldehyde dehydrogenase 1A1 (ALDH1A1) activity is used as a marker of breast cancer stem cells; however, little is known about the regulation of ALDH1A1 expression. Mucin 1 (MUC1) is a heterodimeric protein that is aberrantly overexpressed in most human breast cancers. In studies of breast cancer cells stably silenced for MUC1 or overexpressing the oncogenic MUC1-C subunit, we demonstrate that MUC1-C is sufficient for induction of MEK → ERK signaling and that treatment with a MUC1-C inhibitor suppresses ERK activation. In turn, MUC1-C induces ERK-mediated phosphorylation and activation of the CCAAT/enhancer-binding protein β (C/EBPβ) transcription factor. The results further show that MUC1-C and C/EBPβ form a complex on the ALDH1A1 gene promoter and activate ALDH1A1 gene transcription. MUC1-C-induced up-regulation of ALDH1A1 expression is associated with increases in ALDH activity and is detectable in stem-like cells when expanded as mammospheres. These findings demonstrate that MUC1-C (i) activates a previously unrecognized ERK→C/EBPβ→ALDH1A1 pathway, and (ii) promotes the induction of ALDH activity in breast cancer cells.
MUC1 is a potential target for the treatment of acute myeloid leukemia stem cells
Cancer Research , 2013; 73(17):5569-5579; Stroopinsky D, Rosenblatt J, Ito K, Mills H, Yin L, Rajabi H, Vasir B, Kufe T, Luptakova K, Arnason J, Nardella C, Levine J, Joyce RM, Galinsky I, Reiter Y, Stone R, Pandolfi P, Kufe D, and Avigan D.
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Acute myeloid leukemia (AML) is a malignancy of stem cells with an unlimited capacity for self-renewal. MUC1 is a secreted, oncogenic mucin that is expressed aberrantly in AML blasts, but its potential uses to target AML stem cells have not been explored. Here, we report that MUC1 is highly expressed on AML CD34(+)/lineage(-)/CD38(-) cells as compared with their normal stem cell counterparts. MUC1 expression was not restricted to AML CD34(+) populations as similar results were obtained with leukemic cells from patients with CD34(-) disease. Engraftment of AML stem cell populations that highly express MUC1 (MUC1(high)) led to development of leukemia in NOD-SCID IL2Rgamma(null) (NSG) immunodeficient mice. In contrast, MUC1(low) cell populations established normal hematopoiesis in the NSG model. Functional blockade of the oncogenic MUC1-C subunit with the peptide inhibitor GO-203 depleted established AML in vivo, but did not affect engraftment of normal hematopoietic cells. Our results establish that MUC1 is highly expressed in AML stem cells and they define the MUC1-C subunit as a valid target for their therapeutic eradication.
Oncogenic MUC1-C promotes tamoxifen resistance in human breast cancer
Clinical Cancer Research , 2013; 11(7):714-723; Kharbanda A, Rajabi H, Jin C, Raina D, and Kufe D.
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Tamoxifen resistance of estrogen receptor-positive (ER+) breast cancer cells has been linked in part to activation of receptor tyrosine kinases, such as HER2, and the PI3K-AKT pathway. Mucin 1 (MUC1) is aberrantly overexpressed in about 90% of human breast cancers, and the oncogenic MUC1-C subunit is associated with ERα. The present studies using HER2 overexpressing BT-474 breast cancer cells, which are constitutively resistant to tamoxifen, demonstrate that silencing MUC1-C is associated with (i) downregulation of p-HER2 and (ii) sensitivity to tamoxifen-induced growth inhibition and loss of clonogenic survival. In contrast, overexpression of MUC1-C in tamoxifen-sensitive MCF-7 breast cancer cells resulted in upregulation of p-AKT and tamoxifen resistance. We show that MUC1-C forms complexes with ERα on the estrogen-responsive promoter of Rab31 and that MUC1-C blocks tamoxifen-induced decreases in ERα occupancy. MUC1-C also attenuated tamoxifen-induced decreases in (i) recruitment of the coactivator CREB binding protein, (ii) Rab31 promoter activation, and (iii) Rab31 mRNA and protein levels. The importance of MUC1-C is further supported by the demonstration that targeting MUC1-C with the cell-penetrating peptide inhibitor, GO-203, sensitized tamoxifen-resistant cells to tamoxifen treatment. Moreover, we show that targeting MUC1-C in combination with tamoxifen is highly synergistic in the treatment of tamoxifen-resistant breast cancer cells. Combined, these findings indicate that MUC1-C contributes to tamoxifen resistance.
Targeting the eIF4A RNA helicase blocks translation of the MUC1-C oncoprotein
Oncogene , 2013; 32(17):2179–2188; Jin C, Rajabi H, Rodrigo CM, Porco JA, Jr., and Kufe D.
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The oncogenic MUC1 C-terminal subunit (MUC1-C) subunit is aberrantly overexpressed in most human breast cancers by mechanisms that are not well understood. The present studies demonstrate that stimulation of non-malignant MCF-10A cells with epidermal growth factor (EGF) or heregulin (HRG) results in marked upregulation of MUC1-C translation. Growth factor-induced MUC1-C translation was found to be mediated by PI3KAKT, and not by MEKERK1/2, signaling. We also show that activation of the mammalian target of rapamycin complex 1 (mTORC1)ribosomal protein S6 kinase 1 (S6K1) pathway decreases tumor suppressor programmed cell death protein 4 (PDCD4), an inhibitor of the eIF4A RNA helicase, and contributes to the induction of MUC1-C translation. In concert with these results, treatment of growth factor-stimulated MCF-10A cells with the eIF4A RNA helicase inhibitors, silvestrol and CR-1-31-B, blocked increases in MUC1-C abundance. The functional significance of the increase in MUC1-C translation is supported by the demonstration that MUC1-C, in turn, forms complexes with EGF receptor (EGFR) and promotes EGFR-mediated activation of the PI3KAKT pathway and the induction of growth. Compared with MCF-10A cells, constitutive overexpression of MUC1-C in breast cancer cells was unaffected by EGF stimulation, but was blocked by inhibiting PI3KAKT signaling. The overexpression of MUC1-C in breast cancer cells was also inhibited by blocking eIF4A RNA helicase activity with silvestrol and CR-1-31-B. These findings indicate that EGF-induced MUC1-C expression is mediated by the PI3KAKT pathway and the eIF4A RNA helicase, and that this response promotes EGFR signaling in an autoinductive loop. The findings also indicate that targeting the eIF4A RNA helicase is a novel approach for blocking MUC1-C overexpression in breast cancer cells.
MUC1-C oncoprotein confers androgen-independent growth of human prostate cancer cells
The Prostate , 2012; 72(15):1659-1668; Rajabi H, Ahmad R, Jin C, Joshi M, Guha M, Alam M, Kharbanda S, and Kufe D.
click to see abstract
BACKGROUND:
The mucin 1 (MUC1) heterodimeric oncoprotein is overexpressed in human prostate cancers with aggressive pathologic and clinical features. However, few insights are available regarding the functional role of MUC1 in prostate cancer.
METHODS:
Effects of MUC1-C on androgen receptor (AR) expression were determined by RT-PCR, immunoblotting and AR promoter activation. Coimmunoprecipitations, direct binding assays, and chromatin immunoprecipitation (ChIP) studies were performed to assess the interaction between MUC1-C and AR. Cells were analyzed for invasion, growth in androgen-depleted medium, and sensitivity to MUC1-C inhibitors.
RESULTS:
The present studies in androgen-dependent LNCaP and LAPC4 prostate cancer cells demonstrate that the oncogenic MUC1-C subunit suppresses AR expression. The results show that MUC1-C activates a posttranscriptional mechanism involving miR-135b-mediated downregulation of AR mRNA levels. The results further demonstrate that MUC1-C forms a complex with AR through a direct interaction between the MUC1-C cytoplasmic domain and the AR DNA-binding domain (DBD). In addition, MUC1-C associates with AR in a complex that occupies the PSA promoter. The interaction between MUC1-C and AR is associated with induction of the epithelial-mesenchymal transition (EMT) and increased invasion. MUC1-C also conferred growth in androgen-depleted medium and resistance to bicalutamide treatment. Moreover, expression of MUC1-C resulted in sensitivity to the MUC1-C inhibitor GO-203 with inhibition of growth in vitro. GO-203 treatment also inhibited growth of established tumor xenografts in nude mice.
CONCLUSIONS:
These findings indicate that MUC1-C suppresses AR expression in prostate cancer cells and confers a more aggressive androgen-independent phenotype that is sensitive to MUC1-C inhibition.
Induction of antitumor immunity ex vivo using dendritic cells transduced with fowl pox vector expressing MUC1, CEA, and a triad of costimulatory molecules (rF-PANVAC)
J Immunotherapy , 2012; 35(7):555-569; Vasir B, Zarwan C, Ahmad R, Crawford KD, Rajabi H, Matsuoka K, Rosenblatt J, Wu Z, Mills H, Kufe D, and Avigan D.
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The fowl pox vector expressing the tumor-associated antigens, mucin-1 and carcinoembryonic antigen in the context of costimulatory molecules (rF-PANVAC) has shown promise as a tumor vaccine. However, vaccine-mediated expansion of suppressor T-cell populations may blunt clinical efficacy. We characterized the cellular immune response induced by ex vivo dendritic cells (DCs) transduced with (rF)-PANVAC. Consistent with the functional characteristics of potent antigen-presenting cells, rF-PANVAC-DCs demonstrated strong expression of mucin-1 and carcinoembryonic antigen and costimulatory molecules, CD80, CD86, and CD83; decreased levels of phosphorylated STAT3, and increased levels of Tyk2, Janus kinase 2, and STAT1. rF-PANVAC-DCs stimulated expansion of tumor antigen-specific T cells with potent cytolytic capacity. However, rF-PANVAC-transduced DCs also induced the concurrent expansion of FOXP3 expressing CD4CD25 regulatory T cells (Tregs) that inhibited T-cell activation. Moreover, Tregs expressed high levels of Th2 cytokines [interleukin (IL)-10, IL-4, IL-5, and IL-13] together with phosphorylated STAT3 and STAT6. In contrast, the vaccine-expanded Treg population expressed high levels of Th1 cytokines IL-2 and interferon-γ and the proinflammatory receptor-related orphan receptor γt (RORγt) and IL-17A suggesting that these cells may share effector functions with conventional TH17 T cells. These data suggest that Tregs expanded by rF-PANVAC-DCs, exhibit immunosuppressive properties potentially mediated by Th2 cytokines, but simultaneous expression of Th1 and Th17-associated factors suggests a high degree of plasticity.
Cooperative interaction between the MUC1-C oncoprotein and the Rab31 GTPase in estrogen receptor-positive breast cancer cells
PLoS One , 2012; 7(7):e39432; Jin C, Rajabi H, Pitroda S, Kharbanda A, Li A, Weichselbaum R, and Kufe D.
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Rab31 is a member of the Ras superfamily of small GTPases that has been linked to poor outcomes in patients with breast cancer. The MUC1-C oncoprotein is aberrantly overexpressed in most human breast cancers and also confers a poor prognosis. The present results demonstrate that MUC1-C induces Rab31 expression in estrogen receptor positive (ER+) breast cancer cells. We show that MUC1-C forms a complex with estrogen receptor α (ERα) on the Rab31 promoter and activates Rab31 gene transcription in an estrogen-dependent manner. In turn, Rab31 contributes to the upregulation of MUC1-C abundance in breast cancer cells by attenuating degradation of MUC1-C in lysosomes. Expression of an inactive Rab31(S20N) mutant in nonmalignant breast epithelial cells confirmed that Rab31 regulates MUC1-C expression. The functional significance of the MUC1- C/Rab31 interaction is supported by the demonstration that Rab31 confers the formation of mammospheres by a MUC1-C-dependent mechanism. Analysis of microarray databases further showed that (i) Rab31 is expressed at higher levels in breast cancers as compared to that in normal breast tissues, (ii) MUC1+ and ER+ breast cancers have increased levels of Rab31 expression, and (iii) patients with Rab31-positive breast tumors have a significantly decreased ten-year overall survival as compared to those with Rab31-negative tumors. These findings indicate that MUC1-C and Rab31 function in an autoinductive loop that contributes to overexpression of MUC1-C in breast cancer cells.
The MUC1-C oncoprotein binds to the BH3 domain of the pro-apoptotic BAX protein and blocks BAX function
J Biological Chemistry , 2012; 287(25):20866-20875; Ahmad R, Alam M, Rajabi H, and Kufe D.
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The pro-apoptotic BAX protein contains a BH3 domain that is necessary for its dimerization and for activation of the intrinsic apoptotic pathway. The MUC1 (mucin 1) heterodimeric protein is overexpressed in diverse human carcinomas and blocks apoptosis in the response to stress. In this study, we demonstrate that the oncogenic MUC1-C subunit associates with BAX in human cancer cells. MUC1-C·BAX complexes are detectable in the cytoplasm and mitochondria and are induced by genotoxic and oxidative stress. The association between MUC1-C and BAX is supported by the demonstration that the MUC1-C cytoplasmic domain is sufficient for the interaction with BAX. The results further show that the MUC1-C cytoplasmic domain CQC motif binds directly to the BAX BH3 domain at Cys-62. Consistent with binding to the BAX BH3 domain, MUC1-C blocked BAX dimerization in response to (i) truncated BID in vitro and (ii) treatment of cancer cells with DNA-damaging agents. In concert with these results, MUC1-C attenuated localization of BAX to mitochondria and the release of cytochrome c. These findings indicate that the MUC1-C oncoprotein binds directly to the BAX BH3 domain and thereby blocks BAX function in activating the mitochondrial death pathway.
Targeting cysteine-mediated dimerization of the MUC1-C oncoprotein in human cancer cells
International J of Oncology , 2012; 40(5):1643-1649; Raina D, Ahmad R, Rajabi H, Panchamoorthy G, Kharbanda S, and Kufe D.
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The MUC1 heterodimeric protein is aberrantly overexpressed in diverse human carcinomas and contributes to the malignant phenotype. The MUC1-C transmembrane subunit contains a CQC motif in the cytoplasmic domain that has been implicated in the formation of dimers and in its oncogenic function. The present study demonstrates that MUC1-C forms dimers in human breast and lung cancer cells. MUC1-C dimerization was detectable in the cytoplasm and was independent of MUC1-N, the N-terminal mucin subunit that extends outside the cell. We show that the MUC1-C cytoplasmic domain forms dimers in vitro that are disrupted by reducing agents. Moreover, dimerization of the MUC1-C subunit in cancer cells was blocked by reducing agents and increased by oxidative stress, supporting involvement of the CQC motif in forming disulfide bonds. In support of these observations, mutation of the MUC1-C CQC motif to AQA completely blocked MUC1-C dimerization. Importantly, this study was performed with MUC1-C devoid of fluorescent proteins, such as GFP, CFP and YFP. In this regard, we show that GFP, CFP and YFP themselves form dimers that are readily detectable with cross-linking agents. The present results further demonstrate that a cell-penetrating peptide that targets the MUC1-C CQC cysteines blocks MUC1-C dimerization in cancer cells. These findings provide definitive evidence that: i) the MUC1-C cytoplasmic domain cysteines are necessary and sufficient for MUC1-C dimerization, and ii) these CQC motif cysteines represent an Achilles' heel for targeting MUC1-C function.
MUC1-C oncoprotein induces TCF7L2 transcription factor activation and promotes cyclin D1 expression in human breast cancer cells
J Biological Chemistry , 2012; 287(13):10703-10713; Rajabi H, Ahmad R, Jin C, Kosugi M, Alam M, Joshi M, and Kufe D.
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MUC1 is a heterodimeric glycoprotein that is overexpressed in breast cancers. The present studies demonstrate that the oncogenic MUC1 C-terminal subunit (MUC1-C) associates with the TCF7L2 transcription factor. The MUC1-C cytoplasmic domain (MUC1-CD) binds directly to the TCF7L2 C-terminal region. MUC1-C blocks the interaction between TCF7L2 and the C-terminal-binding protein (CtBP), a suppressor of TCF7L2-mediated transcription. TCF7L2 and MUC1-C form a complex on the cyclin D1 gene promoter and MUC1-C promotes TCF7L2-mediated transcription by the recruitment of β-catenin and p300. Silencing MUC1-C in human breast cancer cells down-regulated activation of the cyclin D1 promoter and decreased cyclin D1 expression. In addition, a MUC1-C inhibitor blocked the interaction with TCF7L2 and suppressed cyclin D1 levels. These findings indicate that the MUC1-C oncoprotein contributes to TCF7L2 activation and thereby promotes cyclin D1 expression in breast cancer cells.
Inhibition of the MUC1-C oncoprotein is synergistic with cytotoxic agents in the treatment of breast cancer cells
Cancer Biology & Therapy , 2013; 14(2):127-134; Uchida Y, Raina D, Kharbanda S, and Kufe D.
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Mucin 1 (MUC1) is a heterodimeric glycoprotein that is aberrantly overexpressed in most human breast cancers. The oncogenic MUC1-C subunit promotes survival and blocks the apoptotic response to genotoxic anticancer agents. In the present studies, human MCF-7 and ZR-75-1 breast cancer cells were treated with the MUC1-C inhibitor, GO-203, a cell-penetrating peptide that blocks MUC1-C homodimerization and thereby its oncogenic function. Treatment with GO-203 was found to promote the apoptotic response of MCF-7 and ZR-75-1 cells to the therapeutic drugs taxol and doxorubicin (DOX). This effect was (1) attenuated by a pan-caspase inhibitor, and (2) mediated, at least in part, by activation of the effector caspase-7 and cleavage of the downstream substrate PARP. Further analysis of the interaction between GO-203 and taxol using isobolograms, which evaluate the nature of the interaction of two drugs, demonstrated that the combination is highly synergistic. These results were supported by combination index (CI) analysis with values of less than 1. GO-203 was also highly synergistic with DOX in studies of both MCF-7 and ZR-75-1 breast cancer cells. These findings indicate that blocking MUC1-C function could be effective in combination with taxol and DOX for the treatment of breast cancer.
Inhibition of the MUC1-C oncoprotein induces multiple myeloma cell death by down-regulating TIGAR expression and depleting NADPH
Blood , 2012; 119(3):810-816; Yin L, Kosugi M, and Kufe D.
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The MUC1-C oncoprotein is aberrantly expressed in most multiple myeloma cells. However, the functional significance of MUC1-C expression in multiple myeloma is not known. The present studies demonstrate that treatment of multiple myeloma cells with a MUC1-C inhibitor is associated with increases in reactive oxygen species (ROS), oxidation of mitochondrial cardiolipin, and loss of the mitochondrial transmembrane potential. The MUC1-C inhibitor-induced increases in ROS were also associated with down-regulation of the p53-inducible regulator of glycolysis and apoptosis (TIGAR). In concert with the decrease in TIGAR expression, which regulates the pentose phosphate pathway, treatment with the MUC1-C inhibitor reduced production of NADPH, and in turn glutathione (GSH) levels. TIGAR protects against oxidative stress-induced apoptosis. The suppression of TIGAR and NADPH levels thus contributed to ROS-mediated late apoptosis/necrosis of multiple myeloma cells. These findings indicate that multiple myeloma cells are dependent on MUC1-C and TIGAR for maintenance of redox balance and that targeting MUC1-C activates a cascade involving TIGAR suppression that contributes to multiple myeloma cell death.
A monoclonal antibody against the oncogenic mucin 1 cytoplasmic domain
Hybridoma , 2011; 30(6):531-535; Panchamoorthy G, Rehan H, Kharbanda A, Ahmad R, and Kufe D.
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Mucin 1 (MUC1) is a heterodimeric protein that is aberrantly overexpressed in diverse human carcinomas and certain hematologic malignancies. The transmembrane MUC1-C subunit confers tumorigenicity and is a target for anti-cancer drug development. In this regard, the MUC1-C cytoplasmic domain interacts with multiple effectors that have been linked to transformation. Here we report on the generation of a mouse monoclonal antibody (MAb) against the human MUC1-C cytoplasmic domain (MUC1-CD). This IgG1 MAb, designated anti-MUC1-CD, reacts with the NYGQLDIFP epitope. We show that anti-MUC1-CD is useful in immunoblotting and immunoprecipitation experiments. In addition, anti-MUC1-CD can be used to detect expression of the MUC1-C subunit in formalin-fixed, paraffin-embedded tissues. The MUC1-C inhibitor has entered Phase I evaluation for patients with refractory solid tumors. The present results indicate that the anti-MUC1-CD antibody could be useful as a biomarker to identify patients with tumors that may be responsive to MUC1-C inhibitors.
MUC1-C oncoprotein regulates glycolysis and pyruvate kinase M2 activity in cancer cells
PLoS One , 2011; 6(11):e28234; Kosugi M, Ahmad R, Alam M, Uchida Y, and Kufe D.
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Aerobic glycolysis in cancer cells is regulated by multiple effectors that include Akt and pyruvate kinase M2 (PKM2). Mucin 1 (MUC1) is a heterodimeric glycoprotein that is aberrantly overexpressed by human breast and other carcinomas. Here we show that transformation of rat fibroblasts by the oncogenic MUC1-C subunit is associated with Akt-mediated increases in glucose uptake and lactate production, consistent with the stimulation of glycolysis. The results also demonstrate that the MUC1-C cytoplasmic domain binds directly to PKM2 at the B- and C-domains. Interaction between the MUC1-C cytoplasmic domain Cys-3 and the PKM2 C-domain Cys-474 was found to stimulate PKM2 activity. Conversely, epidermal growth factor receptor (EGFR)-mediated phosphorylation of the MUC1-C cytoplasmic domain on Tyr-46 conferred binding to PKM2 Lys-433 and inhibited PKM2 activity. In human breast cancer cells, silencing MUC1-C was associated with decreases in glucose uptake and lactate production, confirming involvement of MUC1-C in the regulation of glycolysis. In addition, EGFR-mediated phosphorylation of MUC1-C in breast cancer cells was associated with decreases in PKM2 activity. These findings indicate that the MUC1-C subunit regulates glycolysis and that this response is conferred in part by PKM2. Thus, the overexpression of MUC1-C oncoprotein in diverse human carcinomas could be of importance to the Warburg effect of aerobic glycolysis.
Androgen receptor regulates expression of the MUC1-C oncoprotein in human prostate cancer cells
The Prostate , 2011; 71(12):1299-1308; Rajabi H, Joshi MD, Jin C, Ahmad R, and Kufe D.
click to see abstract
BACKGROUND:
The MUC1 heterodimeric oncoprotein is aberrantly overexpressed in human prostate cancers with more aggressive pathologic and clinical features. However, the signals that regulate MUC1 expression in prostate cancer cells are not well understood.
METHODS:
MUC1 expression was studied in androgen-dependent and -independent prostate cancer cell lines by quantitative RT-PCR, immunoblotting and assessment of MUC1 promoter activation. Chromatin immunoprecipitation (ChIP) studies were performed to assess androgen receptor (AR) occupancy on the MUC1 promoter. Post-transcriptional regulation of MUC1 expression was assessed by miR-125b-mediated effects on activity of the MUC1 3' untranslated region (3'UTR).
RESULTS:
The present studies demonstrate that AR occupies a consensus AR element on the MUC1 promoter in androgen-dependent LNCaP, but not in androgen-independent DU145 and PC3, prostate cancer cells. The results further show that AR downregulates MUC1 gene transcription. Stable introduction of exogenous AR in PC3 (PC3/AR) cells and then silencing of AR confirmed AR-mediated repression of the MUC1 promoter. AR signaling has also been shown to drive miR-125b expression. The present studies further demonstrate that miR-125b suppresses MUC1 translation in LNCaP cells and that an anti-sense miR-125b upregulates expression of MUC1 protein. In addition, stable expression of miR-125b in DU145 cells resulted in decreases in MUC1 levels.
CONCLUSIONS:
These findings demonstrate that AR signaling regulates MUC1 expression by transcriptional and posttranscriptional mechanisms in prostate cancer cells.
Dependence on the MUC1-C oncoprotein in non-small cell lung cancer cells
Molecular Cancer Therapeutics , 2011; 10(5):806-816; Raina D, Kosugi M, Ahmad R, Panchamoorthy G, Rajabi H, Alam M, Shimamura T, Shapiro G, Supko J, Kharbanda S, and Kufe D.
click to see abstract
Non-small cell lung cancer (NSCLC) cells are often associated with constitutive activation of the phosphoinositide 3-kinase (PI3K) → Akt → mTOR pathway. The mucin 1 (MUC1) heterodimeric glycoprotein is aberrantly overexpressed in NSCLC cells and induces gene signatures that are associated with poor survival of NSCLC patients. The present results show that the MUC1 C-terminal subunit (MUC1-C) cytoplasmic domain associates with PI3K p85 in NSCLC cells. We show that inhibition of MUC1-C with cell-penetrating peptides blocks this interaction with PI3K p85 and suppresses constitutive phosphorylation of Akt and its downstream effector, mTOR. In concert with these results, treatment of NSCLC cells with the MUC1-C peptide inhibitor GO-203 was associated with downregulation of PI3K → Akt signaling and inhibition of growth. GO-203 treatment was also associated with increases in reactive oxygen species (ROS) and induction of necrosis by a ROS-dependent mechanism. Moreover, GO-203 treatment of H1975 (EGFR L858R/T790M) and A549 (K-Ras G12S) xenografts growing in nude mice resulted in tumor regressions. These findings indicate that NSCLC cells are dependent on MUC1-C both for activation of the PI3K → Akt pathway and for survival.
MUC1-C oncoprotein suppresses reactive oxygen species-induced terminal differentiation of acute myelogenous leukemia cells
Blood , 2011; 117(18):4863-4870; Yin L, Wu Z, Avigan D, Rosenblatt J, Stone R, Kharbanda S, and Kufe D.
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Acute myeloid leukemia (AML) cells are characterized by unlimited self-renewal and an impaired capacity to undergo terminal differentiation. The MUC1 oncoprotein is aberrantly expressed in AML cells; however, there has been no evidence for involvement of MUC1 in myeloid leukemogenesis. Cell-penetrating peptide inhibitors of the MUC1-C subunit block its oligomerization and thereby oncogenic function. The present results demonstrate that treatment of human MOLM-14 and MV4-11 AML cells with these inhibitors is associated with arrest of growth, induction of late apoptosis/necrosis, and loss of self-renewal capacity. Similar results were obtained with primary blasts from patients with AML. Inhibition of MUC1-C was associated with increases in reactive oxygen species (ROS) and depletion of glutathione. Increases in ROS have been linked to induction of hematopoietic cell differentiation along the myeloid lineage. In this regard, inhibition of MUC1-C was associated with induction of a terminally differentiated myeloid phenotype in AML cell lines and primary blasts by an ROS-dependent mechanism. These findings indicate that MUC1-C function is of importance to AML cell self-renewal and that inhibition of MUC1-C represents a potential therapeutic approach to induce terminal differentiation of AML cells.
Mucin 1 C-terminal subunit oncoprotein is a target for small-molecule inhibitors
Molecular Pharmacology , 2011; 79(5):886-893; Zhou J, Rajabi H, and Kufe D.
click to see abstract
Mucin 1 (MUC1) is a heterodimeric protein that is overexpressed in diverse human carcinomas. The oncogenic function of the MUC1 C-terminal subunit (MUC1-C) subunit is dependent on the formation of dimers through its cytoplasmic domain; however, it is not known whether MUC1-C can be targeted with small-molecule inhibitors. In the present work, an assay using the MUC1-C cytoplasmic domain (MUC1-CD) was established to screen small-molecule libraries for compounds that block its dimerization. Using this approach, the flavone apigenin was identified as an inhibitor of MUC1-CD dimerization in vitro and in cells. By contrast, the structurally related flavone baicalein was ineffective in blocking the formation of MUC1-CD dimers. In concert with these results, apigenin, and not baicalein, blocked the localization of MUC1-C to the nucleus. MUC1-C activates MUC1 gene expression in an autoinductive loop, and apigenin, but not baicalein, treatment was associated with down-regulation of MUC1 mRNA levels and MUC1-C protein. The results also demonstrate that apigenin-induced suppression of MUC1-C expression is associated with apoptotic cell death and loss of clonogenic survival. These findings represent the first demonstration that the MUC1-C cytoplasmic domain is a target for the development of small-molecule inhibitors.
MUC1-C oncoprotein promotes STAT3 activation in an autoinductive regulatory loop
Science Signaling , 2011; 4(ra9); Ahmad R, Rajabi H, Kosugi M, Joshi M, Alam M, Vasir B, Kawano T, Kharbanda S, and Kufe D.
click to see abstract
Signal transducer and activator of transcription 3 (STAT3) is activated in human breast cancer and other malignancies. Mucin 1 (MUC1) is a heterodimeric cell surface glycoprotein that is overexpressed in human carcinomas and, like STAT3, promotes cell survival and induces transformation. We found that in breast cancer cells, the MUC1 carboxyl-terminal receptor subunit (MUC1-C) associates with the gp130-Janus-activated kinase 1 (JAK1)-STAT3 complex. The MUC1-C cytoplasmic domain interacted directly with JAK1 and STAT3, and MUC1-C was necessary for JAK1-mediated STAT3 activation. In turn, MUC1-C and activated STAT3 occupied the promoter of MUC1, and MUC1-C contributed to STAT3-mediated activation of MUC1 transcription. The MUC1-C inhibitor GO-201 blocked the MUC1-C interaction with STAT3, thereby decreasing MUC1-C and STAT3 occupancy on the MUC1 and STAT3 promoters and activation of STAT3 target genes, including MUC1 itself. These findings indicate that MUC1-C promotes STAT3 activation and that MUC1-C and STAT3 function in an autoinductive loop that may play a role in cancer cell survival.
MUC1-C oncoprotein blocks terminal differentiation of chronic myelogenous leukemia cells by a ROS-mediated mechanism
Blood , 2011; 2(1):56-64; Yin L and Kufe D.
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Chronic myelogenous leukemia (CML) inevitably progresses to a blast phase by mechanisms that are not well understood. The MUC1-C oncoprotein is expressed in CML blasts but not chronic phase cells. The present studies demonstrate that treatment of KU812 and K562 CML cells with a cell-penetrating MUC1-C inhibitor, designated GO-203, is associated with increases in reactive oxygen species (ROS) and depletion of glutathione. GO-203 treatment resulted in the complete downregulation of Bcr-Abl expression and induced cell cycle arrest by a ROS-mediated mechanism that was blocked by the antioxidant N-acetylcysteine. Progression of CML to blast crisis has been linked to dysregulation of Wnt/β-catenin signaling and an arrest of differentiation. The present results show that inhibition of MUC1-C induces ROS-mediated suppression of β-catenin expression and induction of a differentiated myeloid phenotype. Our studies also show that GO-203 treatment is associated with ROS-induced decreases in ATP and loss of survival by late apoptosis/necrosis. These findings demonstrate that inhibition of the MUC1-C oncoprotein in CML cells disrupts redox balance and thereby 1) downregulates expression of both Bcr-Abl and β-catenin and 2) induces terminal myeloid differentiation by ROS-mediated mechanisms.
Terminal differentiation of chronic myelogenous leukemia cells is induced by targeting of the MUC1-C oncoprotein
Cancer Biology & Therapy , 2010; 10(5):483-491; Yin L, Ahmad R, Kosugi M, Kawano T, Avigan D, Stone R, Kharbanda S, and Kufe D.
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Chronic myelogenous leukemia (CML) is caused by expression of the Bcr-Abl fusion protein in hematopoietic stem cells. The MUC1-C oncoprotein is expressed in CML blasts and stabilizes Bcr-Abl. The present studies demonstrate that treatment of KU812 and K562 CML cells with GO-201, a cell-penetrating peptide inhibitor of MUC1-C oligomerization, downregulates Bcr-Abl expression and inhibits cell growth. In concert with decreases in Bcr-Abl levels, KU812 and K562 cells responded to GO-201 with induction of a differentiated myeloid phenotype as evidenced by increased expression of CD11b, CD11c and CD14. The results also show that the GO-201-treated cells undergo a late apoptotic/necrotic response, consistent with induction of terminal differentiation. Primary CML blasts expressing MUC1 similarly responded to GO-201 with induction of a more differentiated phenotype and late apoptosis/necrosis. In addition, treatment of KU812 xenografts in nude mice was associated with upregulation of CD11 and tumor regression. These findings indicate that CML blasts respond to targeting of the MUC1-C oncoprotein with induction of terminal differentiation.
Commentary - Oncogenic function of the MUC1 receptor subunit in gene regulation
Oncogene , 2010; 29(42):5663-5666; Kufe D.
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The mucin 1 (MUC1) oncoprotein is overexpressed by diverse human cancers; however, it has remained largely unclear how MUC1 contributes to tumorigenesis. In this issue of Oncogene and in concert with published work, Behrens et al. report that the MUC1 receptor subunit activates genes involved in invasion, angiogenesis and metastasis.
Survival of human multiple myeloma cells is dependent on MUC1 C-terminal transmembrane subunit oncoprotein function
Molecular Pharmacology , 2010; 78(2):166-174; Yin L, Ahmad R, Kosugi M, Kufe T, Vasir B, Avigan D, Kharbanda S, and Kufe D.
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The MUC1 C-terminal transmembrane subunit (MUC1-C) oncoprotein is a direct activator of the canonical nuclear factor-kappaB (NF-kappaB) RelA/p65 pathway and is aberrantly expressed in human multiple myeloma cells. However, it is not known whether multiple myeloma cells are sensitive to the disruption of MUC1-C function for survival. The present studies demonstrate that peptide inhibitors of MUC1-C oligomerization block growth of human multiple myeloma cells in vitro. Inhibition of MUC1-C function also blocked the interaction between MUC1-C and NF-kappaB p65 and activation of the NF-kappaB pathway. In addition, inhibition of MUC1-C in multiple myeloma cells was associated with activation of the intrinsic apoptotic pathway and induction of late apoptosis/necrosis. Primary multiple myeloma cells, but not normal B-cells, were also sensitive to MUC1-C inhibition. Significantly, treatment of established U266 multiple myeloma xenografts growing in nude mice with a lead candidate MUC1-C inhibitor resulted in complete tumor regression and lack of recurrence. These findings indicate that multiple myeloma cells are dependent on intact MUC1-C function for constitutive activation of the canonical NF-kappaB pathway and for their growth and survival.
miR-1226 targets expression of the mucin 1 oncoprotein and induces cell death
International J of Oncology , 2010; 37(1):61-69; Jin C, Rajabi H, and Kufe D.
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The MUC1 oncoprotein is aberrantly overexpressed in human carcinomas and hematologic malignancies. Micro-RNAs (miRNAs) have been implicated in the suppression and induction of oncogenesis. The present studies demonstrate that the MUC1 mRNA 3' untranslated region (3'UTR) contains a highly conserved motif for binding of a novel miRNA, miR-1226, that has no known targets. The results show that miR-1226 is expressed in human breast cancer cell lines and non-malignant mammary epithelial cells. We also show that miR-1226 interacts with the MUC1 mRNA 3'UTR and that miR-1226 downregulates endogenous MUC1 protein levels. Consistent with miR-1226-induced downregulation of MUC1 expression, the results demonstrate that miR-1226 induces i) an increase in reactive oxygen species, ii) loss of the mitochondrial transmembrane potential, and iii) a decrease in cell survival. These findings indicate that expression of the MUC1 oncoprotein is downregulated by miR-1226 and that miR-1226 thereby functions as a tumor suppressor by promoting the induction of cell death.
MUC1-associated proliferation signature predicts outcomes in lung adenocarcinoma patients
BMC Medical Genomics , 2010; 3(16); MacDermed DM, Khodarev NN, Pitroda SP, Edwards DC, Pelizzari CA, Huang L, Kufe DW, and Weichselbaum R.
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BACKGROUND:
MUC1 protein is highly expressed in lung cancer. The cytoplasmic domain of MUC1 (MUC1-CD) induces tumorigenesis and resistance to DNA-damaging agents. We characterized MUC1-CD-induced transcriptional changes and examined their significance in lung cancer patients.
METHODS:
Using DNA microarrays, we identified 254 genes that were differentially expressed in cell lines transformed by MUC1-CD compared to control cell lines. We then examined expression of these genes in 441 lung adenocarcinomas from a publicly available database. We employed statistical analyses independent of clinical outcomes, including hierarchical clustering, Student's t-tests and receiver operating characteristic (ROC) analysis, to select a seven-gene MUC1-associated proliferation signature (MAPS). We demonstrated the prognostic value of MAPS in this database using Kaplan-Meier survival analysis, log-rank tests and Cox models. The MAPS was further validated for prognostic significance in 84 lung adenocarcinoma patients from an independent database.
RESULTS:
MAPS genes were found to be associated with proliferation and cell cycle regulation and included CCNB1, CDC2, CDC20, CDKN3, MAD2L1, PRC1 and RRM2. MAPS expressors (MAPS+) had inferior survival compared to non-expressors (MAPS-). In the initial data set, 5-year survival was 65% (MAPS-) vs. 45% (MAPS+, p < 0.0001). Similarly, in the validation data set, 5-year survival was 57% (MAPS-) vs. 28% (MAPS+, p = 0.005).
CONCLUSIONS:
The MAPS signature, comprised of MUC1-CD-dependent genes involved in the control of cell cycle and proliferation, is associated with poor outcomes in patients with adenocarcinoma of the lung. These data provide potential new prognostic biomarkers and treatment targets for lung adenocarcinoma.
Generation of tumor-specific T lymphocytes using dendritic cell/tumor fusions and anti-CD3/CD28
J Immunotherapy , 2010; 33(2):155-166; Rosenblatt J, Wu Z, Vasir B, Zarwan C, Stone R, Mills H, Friedman T, Konstantinopoulos PA, Spentzos D, Ghebremichael M, Stevenson K, Neuberg D, Levine JD, Joyce R, Tzachanis D, Boussiotis V, Kufe D, and Avigan D.
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Adoptive immunotherapy with tumor-specific T cells represents a promising treatment strategy for patients with malignancy. However, the efficacy of T-cell therapy has been limited by the ability to expand tumor-reactive cells with an activated phenotype that effectively target malignant cells. We have developed an anticancer vaccine in which patient-derived tumor cells are fused with autologous dendritic cells (DCs), such that a wide array of tumor antigens are presented in the context of DC-mediated costimulation. In this study, we demonstrate that DC/tumor fusions induce T cells that react with tumor and are dramatically expanded by subsequent ligation of the CD3/CD28 costimulatory complex. These T cells exhibit a predominantly activated phenotype as manifested by an increase in the percentage of cells expressing CD69 and interferon gamma. In addition, the T cells upregulate granzyme B expression and are highly effective in lysing autologous tumor targets. Targeting of tumor-specific antigen was demonstrated by the expansion of T cells with specificity for the MUC1 tetramer. Stimulation with anti-CD3/CD28 followed by DC/tumor fusions or either agent alone failed to result in a similar expansion of tumor-reactive T cells. Consistent with these findings, spectratyping analysis demonstrates selective expansion of T-cell clones as manifested by considerable skewing of the Vbeta repertoire following sequential stimulation with DC/tumor fusions and anti-CD3/CD28. Gene expression analysis was notable for the upregulation of inflammatory pathways. These findings indicate that stimulation with DC/tumor fusions provides a unique platform for subsequent expansion with anti-CD3/CD28 in adoptive T-cell therapy of cancer.
MUC1-C oncoprotein interacts directly with ATM and promotes the DNA damage response to ionizing radiation
Genes & Cancer , 2010; 1(3):239-250; Huang L, Liao X, Beckett M, Li Y, Khanna KK, Wang Z, Kharbanda S, R W, and Kufe D.
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The ataxia-telangiectasia mutated (ATM) kinase is activated in the cellular response to ionizing radiation (IR) and is of importance to the repair of DNA double strand breaks (DSBs). The MUC1 oncoprotein is aberrantly overexpressed in human breast carcinomas. The present work demonstrates that the MUC1 C-terminal subunit (MUC1-C) constitutively interacts with ATM in human breast cancer cells. We show that the MUC1-C cytoplasmic domain binds directly to ATM HEAT repeats. Our results also demonstrate that the MUC1-C cytoplasmic domain binds to the ATM substrate H2AX. The functional significance of these interactions is supported by the finding that MUC1-C promotes removal of IR-induced nuclear γH2AX foci. MUC1-C also protects against IR-induced chromosomal aberrations. In concert with these results, MUC1-C blocks IR-induced death by promoting repair of potentially lethal DNA damage. These findings indicate that the overexpression of MUC1 can protect against IR-induced DNA DSBs and may represent a physiologic response that has been exploited by malignant cells.
Cooperativity of the MUC1 oncoprotein and STAT1 pathway in poor prognosis human breast cancer
Oncogene , 2010; 29(6):920-929; Khodarev N, Ahmad R, Rajabi H, Pitroda S, Kufe T, McClary C, Joshi MD, MacDermed D, Weichselbaum R, and Kufe D.
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Signal transducer and activator of transcription 1 (STAT1) is activated in the inflammatory response to interferons. The MUC1 oncoprotein is overexpressed in human breast cancers. Analysis of genes differentially expressed in MUC1-transformed cells has identified a network linking MUC1 and STAT1 that is associated with cellular growth and inflammation. The results further show that the MUC1-C subunit associates with STAT1 in cells and the MUC1-C cytoplasmic domain binds directly to the STAT1 DNA-binding domain. The interaction between MUC1-C and STAT1 is inducible by IFNgamma in non-malignant epithelial cells and constitutive in breast cancer cells. Moreover, the MUC1-STAT1 interaction contributes to the activation of STAT1 target genes, including MUC1 itself. Analysis of two independent databases showed that MUC1 and STAT1 are coexpressed in about 15% of primary human breast tumors. Coexpression of MUC1 and the STAT1 pathway was found to be significantly associated with decreased recurrence-free and overall survival. These findings indicate that (i) MUC1 and STAT1 function in an auto-inductive loop, and (ii) activation of both MUC1 and the STAT1 pathway in breast tumors confers a poor prognosis for patients.
Mucin 1 oncoprotein expression is suppressed by the miR-125b oncomir
Genes & Cancer , 2010; 1(1):62-65; Rajabi H, Jin C, Ahmad R, McClary C, and Kufe D.
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The MUC1 oncoprotein is overexpressed in most human breast cancers by mechanisms that are incompletely understood. The microRNA, miR-125b, is downregulated in breast cancer cells. The present studies demonstrate that the MUC1 3'UTR contains a site for binding of the miR-125b seed region. The results show that the MUC1 3'UTR suppresses luciferase expression and that this effect is abrogated by mutation or deletion of the miR-125b binding site. Expression of an anti-sense miR-125b in BT-549 breast cancer cells was associated with induction of MUC1 protein, but not MUC1 mRNA, levels. The anti-sense miR-125b also increased BT-549 cell growth by a MUC1-dependent mechanism. In addition, overexpression of exogenous miR-125b downregulated MUC1 protein, and not MUC1 transcripts, in ZR-75-1 breast cancer cells. Silencing of MUC1 in ZR-75-1 cells with a siRNA has been shown to promote DNA damage-induced apoptosis. In concert with these observations, miR-125b-induced decreases in MUC1 levels increased the apoptotic response of ZR-75-1 cells to cisplatin treatment. These findings indicate that miR-125b suppresses translation of the MUC1 oncoprotein and that miR-125b thereby functions as a tumor suppressor in breast cancer cells.
MUC1 oncoprotein is a druggable target in human prostate cancer cells
Molecular Cancer Therapeutics , 2009; 8(11):3056-3065; Joshi MD, Ahmad R, Raina D, Rajabi H, Bubley G, Kharbanda S, and Kufe D.
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Human prostate cancers are dependent on the androgen receptor for their progression. The MUC1 heterodimeric oncoprotein is aberrantly overexpressed in prostate cancers; however, it is not known if MUC1 is of functional importance to these tumors. To assess dependence on MUC1, we synthesized an inhibitor, designated GO-201, which interacts directly with the MUC1-C subunit at its oligomerization domain. Treatment of MUC1-positive DU145 and PC3 prostate cancer cells with GO-201, and not an altered version, resulted in inhibition of proliferation. GO-201 also induced necrotic cell death that was associated with increases in reactive oxygen species, loss of mitochondrial transmembrane potential, and depletion of ATP. By contrast, GO-201 had no effect against MUC1-negative LNCaP, CWR22Rv1, and MDA-PCa-2b prostate cancer cells. Significantly, GO-201 treatment of DU145 and PC3 xenografts growing in nude mice resulted in complete tumor regression and prolonged lack of recurrence. These findings indicate that certain prostate cancer cells are dependent on MUC1-C for growth and survival and that directly targeting MUC1-C results in their death in vitro and in tumor models.
MUC1-C oncoprotein functions as a direct activator of the nuclear factor-kappaB p65 transcription factor
Cancer Research , 2009; 69:7013-7021; Ahmad R, Raina D, Joshi MD, Kawano T, Kharbanda S, and Kufe D.
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Nuclear factor-kappaB (NF-kappaB) is constitutively activated in diverse human malignancies. The mucin 1 (MUC1) oncoprotein is overexpressed in human carcinomas and, like NF-kappaB, blocks cell death and induces transformation. The present studies show that MUC1 constitutively associates with NF-kappaB p65 in carcinoma cells. The MUC1 COOH-terminal subunit (MUC1-C) cytoplasmic domain binds directly to NF-kappaB p65 and, importantly, blocks the interaction between NF-kappaB p65 and its inhibitor IkappaBalpha. We show that NF-kappaB p65 and MUC1-C constitutively occupy the promoter of the Bcl-xL gene in carcinoma cells and that MUC1-C contributes to NF-kappaB-mediated transcriptional activation. Studies in nonmalignant epithelial cells show that MUC1-C interacts with NF-kappaB in the response to tumor necrosis factor-alpha stimulation. Moreover, tumor necrosis factor-alpha induces the recruitment of NF-kappaB p65-MUC1-C complexes to NF-kappaB target genes, including the promoter of the MUC1 gene itself. We also show that an inhibitor of MUC1-C oligomerization blocks the interaction with NF-kappaB p65 in vitro and in cells. The MUC1-C inhibitor decreases MUC1-C and NF-kappaB p65 promoter occupancy and expression of NF-kappaB target genes. These findings indicate that MUC1-C is a direct activator of NF-kappaB p65 and that an inhibitor of MUC1 function is effective in blocking activation of the NF-kappaB pathway.
Direct targeting of the mucin 1 oncoprotein blocks survival and tumorigenicity of human breast carcinoma cells
Cancer Research , 2009; 69(12):5133–5141; Raina D, Ahmad R, Joshi M, Yin L, Wu Z, Kawano T, Vasir B, Avigan D, Kharbanda S, and Kufe D.
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The mucin 1 (MUC1) oncoprotein is aberrantly overexpressed by approximately 90% of human breast cancers. However, there are no effective agents that directly inhibit MUC1 and induce death of breast cancer cells. We have synthesized a MUC1 inhibitor (called GO-201) that binds to the MUC1 cytoplasmic domain and blocks the formation of MUC1 oligomers in cells. GO-201, and not an altered version, attenuates targeting of MUC1 to the nucleus of human breast cancer cells, disrupts redox balance, and activates the DNA damage response. GO-201 also arrests growth and induces necrotic death. By contrast, the MUC1 inhibitor has no effect on cells null for MUC1 expression or nonmalignant mammary epithelial cells. Administration of GO-201 to nude mice bearing human breast tumor xenografts was associated with loss of tumorigenicity and extensive necrosis, which results in prolonged regression of tumor growth. These findings show that targeting the MUC1 oncoprotein is effective in inducing death of human breast cancer cells in vitro and in tumor models.
MUC1 oncoprotein promotes autophagy in a survival response to glucose deprivation
International J of Oncology , 2009; 34(6):1691-1699; Yin L, Kharbanda S, and Kufe D.
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Tumor cells survive under conditions of nutrient deprivation by mechanisms that are not fully understood. The MUC1 oncoprotein is aberrantly overexpressed by most human carcinomas and blocks oxidative stress-induced death. The present studies show that MUC1 inhibits the induction of necrosis in response to the deprivation of glucose. MUC1 suppressed glucose deprivation-induced increases in reactive oxygen species (ROS) and thereby depletion of ATP and cell death. Cells respond to oxidative stress and energy depletion with the induction of autophagy. Our results demonstrate that MUC1 blocks depletion of ATP and sustains growth of glucose-deprived cells by a mechanism sensitive to the autophagy inhibitor, 3-methyladenine. Silencing expression of ATG7, a protein essential for the formation of autophagic vacuoles, also attenuated the MUC1-sustained increases in ATP and growth in response to glucose deprivation. Moreover, we found that MUC1 stimulates AMPK activation and thereby promotes lysosomal turnover of LC3-II, a marker of starvation-induced autophagic activity. These results indicate that MUC1 suppresses glucose deprivation-induced increases in ROS and thereby promotes ATP production and survival. The findings also indicate that the overexpression of MUC1 as found in human cancers could provide a survival advantage in microenvironments with low glucose levels.
MUC1-induced alterations in a lipid metabolic gene network predict response of human breast cancers to tamoxifen treatment
Proceedings of the National Academy of Sciences USA , 2009; 106(5837-5841; Pitroda S, Khodarev N, Beckett M, Kufe D, and Weichselbaum R.
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The mucin 1 (MUC1) oncoprotein is aberrantly overexpressed in human breast cancers. Although MUC1 modulates the activity of estrogen receptor alpha (ER), there is no information regarding the effects of MUC1 on global gene expression patterns and the potential role of MUC1-induced genes in predicting outcome for breast cancer patients. We have developed an experimental model of MUC1-induced transformation that has identified the activation of genes involved in cholesterol and fatty acid metabolism. A 38-gene set of experimentally derived MUC1-induced genes associated with lipid metabolism was applied to the analysis of ER(+) breast cancer patients treated with tamoxifen. The results obtained from 2 independent databases demonstrate that patients overexpressing MUC1 and the lipid metabolic pathways are at significantly higher risk for death and recurrence/distant metastasis. By contrast, these genes were not predictive in untreated patients. Furthermore, a positive correlation was found between expression of the 38-gene set and the ER signaling pathway. These findings indicate that (i) MUC1 regulates cholesterol and fatty acid metabolism, and (ii) activation of these pathways in ER(+) breast cancers predicts failure to tamoxifen treatment.
MUC1-induced transcriptional programs associated with tumorigenesis predict outcome in breast and lung cancer
Cancer Research , 2009; 69(7):2833-2837; Khodarev NN, Pitroda SP, Beckett MA, MacDermed DM, Huang L, Kufe DW, and Weichselbaum RR.
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The Mucin 1 (MUC1) oncoprotein is aberrantly overexpressed in diverse human malignancies including breast and lung cancer. Although MUC1 modulates the activity of several transcription factors, there is no information regarding the effects of MUC1 on global gene expression patterns and the potential role of MUC1-induced genes in predicting outcome for cancer patients. We have developed an experimental model of MUC1-induced transformation that has identified the activation of gene families involved in oncogenesis, angiogenesis, and extracellular matrix remodeling. A set of experimentally derived MUC1-induced genes associated with tumorigenesis was applied to the analysis of breast and lung adenocarcinoma cancer databases. A 35-gene MUC1-induced tumorigenesis signature predicts significant decreases in both disease-free and overall survival in patients with breast (n=295) and lung (n=442) cancers. The data show that the MUC1 oncoprotein contributes to the regulation of genes that are highly predictive of clinical outcome in breast and lung cancer patients.
MUC1 oncoprotein suppresses activation of the ARF-MDM2-p53 pathway
Cancer Biology & Therapy , 2008; 7:1956-1967; Raina D, Ahmad R, Chen D, Kumar S, Kharbanda S, and Kufe D.
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The MUC1 oncoprotein interacts with the c-Abl tyrosine kinase and blocks nuclear targeting of c-Abl in the apoptotic response to DNA damage. Mutation of the MUC1 cytoplasmic domain at Tyr-60 disrupts the MUC1-c-Abl interaction. The present results demonstrate that the MUC1(Y60F) mutant is a potent inducer of the ARF tumor suppressor. MUC1(Y60F) induces transcription of the ARF locus by a c-Abl-dependent mechanism that promotes CUL-4A-mediated nuclear export of the replication protein Cdc6. The functional significance of these findings is that MUC1(Y60F)-induced ARF expression and thereby inhibition of MDM2 results in the upregulation of p53 and the homeodomain interacting protein kinase 2 (HIPK2) serine/threonine kinase. HIPK2-mediated phosphorylation of p53 on Ser-46 was further associated with a shift from expression of the cell cycle arrest-related p21 gene to the apoptosis-related PUMA gene. We also show that the MUC1(Y60F) mutant functions as dominant negative inhibitor of tumorigenicity. These findings indicate that the oncogenic function of MUC1 is conferred by suppressing activation of the ARF-MDM2-p53 pathway.
MUC1 oncoprotein blocks death receptor-mediated apoptosis by inhibiting recruitment of caspase-8
Cancer Research , 2008; 68:6136-6144; Agata N, Kawano T, Ahmad R, Raina D, Kharbanda S, and Kufe D.
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Stimulation of the death receptor superfamily induces the activation of caspase-8 and thereby the apoptotic response. The MUC1 oncoprotein is aberrantly overexpressed by diverse human malignancies and inhibits stress-induced apoptosis. The present results show that MUC1 blocks activation of caspase-8 and apoptosis in the response of malignant cells to tumor necrosis factor alpha, tumor necrosis factor-related apoptosis-inducing ligand, and Fas ligand. The results show that MUC1 associates constitutively with caspase-8. The MUC1 cytoplasmic domain (MUC1-CD) binds directly to the caspase-8 p18 fragment upstream to the catalytic Cys(360) site. The results also show that MUC1-CD binds to Fas-associated death domain (FADD) at the death effector domain. In nonmalignant epithelial cells, MUC1 interacts with caspase-8 and FADD as an induced response to death receptor stimulation. The functional significance of these interactions is supported by the demonstration that MUC1 competes with caspase-8 for binding to FADD and blocks recruitment of caspase-8 to the death-inducing signaling complex. These findings indicate that MUC1 is of importance to the physiologic regulation of caspase-8 activity and that overexpression of MUC1, as found in human malignancies, could contribute to constitutive inhibition of death receptor signaling pathways.
Fusions of dendritic cells with breast carcinoma stimulate the expansion of regulatory T cells while concomitant exposure to IL-12, CpG oligodeoxynucleotides, and anti-CD3/CD28 promotes the expansion of activated tumor reactive cells
J of Immunology , 2008; 181(1):808-821; Vasir B, Wu Z, Crawford K, Rosenblatt J, Zarwan C, Bissonnette A, Kufe D, and Avigan D.
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Vaccination of patients with dendritic cell (DC)/breast carcinoma fusions stimulated antitumor immune responses in a majority of patients with metastatic disease but only a subset demonstrate evidence of tumor regression. To define the factors that limit vaccine efficacy, we examined the biological characteristics of DC/breast carcinoma fusions as APCs and the nature of the vaccine-mediated T cell response. We demonstrate that fusion of DCs with breast carcinoma cells up-regulates expression of costimulatory and maturation markers and results in high levels of expression of IL-12 consistent with their role as activated APCs. Fusion cells also express the chemokine receptor CCR7, consistent with their ability to migrate to the draining lymph node. However, DC/breast cancer fusions stimulate a mixed T cell response characterized by the expansion of both activated and regulatory T cell populations, the latter of which is characterized by expression of CTLA-4, FOXP3, IL-10, and the suppression of T cell responses. Our results demonstrate that IL-12, IL-18, and TLR 9 agonist CpG oligodeoxynucleotides reduce the level of fusion-mediated regulatory T cell expansion. Our results also demonstrate that sequential stimulation with DC/breast carcinoma fusions and anti-CD3/CD28 results in the marked expansion of activated tumor-specific T cells. These findings suggest that DC/breast carcinoma fusions are effective APCs, but stimulate inhibitory T cells that limit vaccine efficacy. In contrast, exposure to TLR agonists, stimulatory cytokines, and anti-CD3/CD28 enhances vaccine efficacy by limiting the regulatory T cell response and promoting expansion of activated effector cells.
MUC1 oncoprotein promotes growth and survival of human multiple myeloma cells
International J of Oncology , 2008; 33(1):153-159; Kawano T, Ahmad R, Nogi H, Agata N, Anderson K, and Kufe D.
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The MUC1 oncoprotein is aberrantly expressed in human multiple myeloma cells by mechanisms that are not understood. Moreover, the functional role of MUC1 in multiple myeloma is not known. The present studies demonstrate that the MUC1 gene locus is amplified in multiple myeloma cell lines and in primary cells from patients. The KMS28PE multiple myeloma cell line, which was found to have MUC1 gene amplification, was stably silenced for MUC1 using different siRNAs. Silencing MUC1 was associated with a decrease in nuclear beta-catenin levels, consistent with the function of MUC1 in stabilizing beta-catenin. MUC1 is also known to activate the IKKbeta-->NF-kappaB pathway and KMS28PE cells silenced for MUC1 were found to have downregulation of IKKbeta and IkappaBalpha phosphorylation, and decreased nuclear targeting of NF-kappaB p65. The results also demonstrate that MUC1: i) contributes to KMS28PE cell proliferation, and ii) protects against apoptosis and loss of self-renewal in the response to melphalan and dexamethasone. These findings indicate that MUC1 activates the beta-catenin and NF-kappaB pathways in multiple myeloma cells and contributes to their growth and survival.
MUC1 oncoprotein activates the IkappaB kinase beta complex and constitutive NF-kappaB signalling
Nature Cell Biology , 2007; 9:1419-1427; Ahmad R, Raina D, Trivedi V, Ren J, Rajabi H, Kharbanda S, and Kufe D.
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Nuclear factor-kappaB (NF-kappaB) is constitutively activated in diverse human malignancies by mechanisms that are not understood. The MUC1 oncoprotein is aberrantly overexpressed by most human carcinomas and, similarly to NF-kappaB, blocks apoptosis and induces transformation. This study demonstrates that overexpression of MUC1 in human carcinoma cells is associated with constitutive activation of NF-kappaB p65. We show that MUC1 interacts with the high-molecular-weight IkappaB kinase (IKK) complex in vivo and that the MUC1 cytoplasmic domain binds directly to IKKbeta and IKKgamma. Interaction of MUC1 with both IKKbeta and IKKgamma is necessary for IKKbeta activation, resulting in phosphorylation and degradation of IkappaBalpha. Studies in non-malignant epithelial cells show that MUC1 is recruited to the TNF-R1 complex and interacts with IKKbeta-IKKgamma in response to TNFalpha stimulation. TNFalpha-induced recruitment of MUC1 is dependent on TRADD and TRAF2, but not the death-domain kinase RIP1. In addition, MUC1-mediated activation of IKKbeta is dependent on TAK1 and TAB2. These findings indicate that MUC1 is important for physiological activation of IKKbeta and that overexpression of MUC1, as found in human cancers, confers sustained induction of the IKKbeta-NF-kappaB p65 pathway.
MUC1 oncoprotein regulates Bcr-Abl stability and pathogenesis in chronic myelogenous leukemia cells
Cancer Research , 2007; 67(24):11576-11584; Kawano T, Ito M, Raina D, Wu Z, Rosenblatt J, Avigan D, Stone R, and Kufe D.
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Chronic myelogenous leukemia (CML) results from expression of the Bcr-Abl fusion protein in hematopoietic stem cells. The MUC1 heterodimeric protein is aberrantly overexpressed in diverse human carcinomas. The present studies show that MUC1 is expressed in the human K562 and KU812 CML cell lines. The results show that MUC1 associates with Bcr-Abl through a direct interaction between the Bcr N-terminal region and the MUC1 cytoplasmic domain. Stable silencing of MUC1 decreased cytoplasmic Bcr-Abl levels by promoting Bcr-Abl degradation. Silencing MUC1 was also associated with decreases in K562 and KU812 cell self-renewal capacity and with a more differentiated erythroid phenotype. The results further show that silencing MUC1 increases sensitivity of CML cells to imatinib-induced apoptosis. Analysis of primary CML blasts confirmed that, as found with the CML cell lines, MUC1 blocks differentiation and the apoptotic response to imatinib treatment. These findings indicate that MUC1 stabilizes Bcr-Abl and contributes to the pathogenesis of CML cells by promoting self renewal and inhibiting differentiation and apoptosis.
The MUC1 and galectin-3 oncoproteins function in a microRNA-dependent regulatory loop
Molecular Cell , 2007; 27(6):992-1004; Ramasamy S, Duraisamy S, Barbashov S, Kawano T, Kharbanda S, and Kufe D.
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The MUC1 heterodimeric transmembrane glycoprotein is aberrantly overexpressed by diverse human carcinomas. Galectin-3 is a beta-galactoside binding protein that has also been associated with the development of human cancers. The present results demonstrate that MUC1 induces galectin-3 expression by a posttranscriptional mechanism. We show that the MUC1 C-terminal subunit is glycosylated on Asn-36 and that this modification is necessary for upregulation of galectin-3. N-glycosylated MUC1-C increases galectin-3 mRNA levels by suppressing expression of the microRNA miR-322 and thereby stabilizing galectin-3 transcripts. The results show that, in turn, galectin-3 binds to MUC1-C at the glycosylated Asn-36 site. The significance of the MUC1-C-galectin-3 interaction is supported by the demonstration that galectin-3 forms a bridge between MUC1 and the epidermal growth factor receptor (EGFR) and that galectin-3 is essential for EGF-mediated interactions between MUC1 and EGFR. These findings indicate that MUC1 and galectin-3 function as part of a miR-322-dependent regulatory loop.
Nuclear import of the MUC1-C oncoprotein is mediated by nucleoporin Nup62
J Biological Chemistry , 2007; 282(27):19321-19330; Leng Y, Cao C, Ren J, Huang L, Chen D, Ito M, and Kufe D
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The MUC1 heterodimeric transmembrane protein is aberrantly overexpressed by most human carcinomas. The MUC1 C-terminal subunit (MUC1-C) is devoid of a classical nuclear localization signal and is targeted to the nucleus by an unknown mechanism. The present results demonstrate that MUC1-C associates with importin beta and not importin alpha. The results also show that, like importin beta, MUC1-C binds to Nup62 (nucleoporin p62). MUC1-C binds directly to the Nup62 central domain and indirectly to the Nup62 C-terminal alpha-helical coiled-coil domain. We demonstrate that MUC1-C forms oligomers and that oligomerization is necessary for binding to Nup62. The MUC1-C cytoplasmic domain contains a CQC motif that when mutated to AQA abrogates oligomerization and binding to Nup62. Stable expression of MUC1 with the CQC --> AQA mutations was associated with targeting to the cell membrane and cytosol and attenuation of nuclear localization. The results further show that expression of MUC1(CQC-AQA) attenuates MUC1-induced (i) transcriptional coactivation, (ii) anchorage-independent growth, and (iii) tumorigenicity. These findings indicate that the MUC1-C oncoprotein is imported to the nucleus by a pathway involving Nup62.
MUC1 oncoprotein stabilizes and activates estrogen receptor alpha
Molecular Cell , 2006; 21(2):295-305; Wei X, Xu H, and Kufe D.
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The MUC1 protein is aberrantly overexpressed by most human breast carcinomas. We report that the MUC1 C-terminal subunit associates with estrogen receptor alpha (ERalpha) and that this interaction is stimulated by 17beta-estradiol (E2). MUC1 binds directly to the ERalpha DNA binding domain and stabilizes ERalpha by blocking its ubiquitination and degradation. Chromatin immunoprecipitation assays further demonstrate that MUC1 (1) associates with ERalpha complexes on estrogen-responsive promoters, (2) enhances ERalpha promoter occupancy, and (3) increases recruitment of the p160 coactivators SRC-1 and GRIP1. In concert with these results, we show that MUC1 stimulates ERalpha-mediated transcription and contributes to E2-mediated growth and survival of breast cancer cells. These findings provide evidence that MUC1 stabilizes ERalpha and that this oncoprotein is of importance to the activation of ERalpha function.
MUC1 oncoprotein blocks glycogen synthase kinase 3beta-mediated phosphorylation and degradation of beta-catenin
Cancer Research , 2005; 65(22):10413-10422; Huang L, Chen D, Liu D, Yin L, Kharbanda S, and Kufe D.
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Dysregulation of beta-catenin is of importance to the development of diverse human malignancies. The MUC1 oncoprotein is aberrantly overexpressed by most human carcinomas and associates with beta-catenin. However, the functional significance of the MUC1-beta-catenin interaction is not known. Here, we show that MUC1 increases beta-catenin levels in the cytoplasm and nucleus of carcinoma cells. Previous studies have shown that glycogen synthase kinase 3beta (GSK3beta) phosphorylates beta-catenin and thereby targets it for proteosomal degradation. Consistent with the up-regulation of beta-catenin levels, our results show that MUC1 blocks GSK3beta-mediated phosphorylation and degradation of beta-catenin. To further define the interaction between MUC1 and beta-catenin, we identified a serine-rich motif (SRM) in the MUC1 cytoplasmic domain that binds directly to beta-catenin Armadillo repeats. Mutation of the SRM attenuated binding of MUC1 to beta-catenin and MUC1-mediated inhibition of beta-catenin degradation. Importantly, disruption of the MUC1-beta-catenin interaction with the SRM mutant also attenuated MUC1-induced anchorage-dependent and -independent growth and delayed MUC1-mediated tumorigenicity. These findings indicate that MUC1 promotes transformation, at least in part, by blocking GSK3beta-mediated phosphorylation and thereby degradation of beta-catenin.
Human MUC1 oncoprotein regulates p53-responsive gene transcription in the genotoxic stress response
Cancer Cell , 2005; 7:167-178; Wei X, Xu H, and Kufe D.
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The MUC1 oncoprotein is aberrantly overexpressed by most human carcinomas. The present work demonstrates that MUC1 associates with the p53 tumor suppressor, and that this interaction is increased by genotoxic stress. The MUC1 cytoplasmic domain binds directly to p53 regulatory domain. Chromatin immunoprecipitation assays demonstrate that MUC1 coprecipitates with p53 on the p53-responsive elements of the p21 gene promoter and coactivates p21 gene transcription. Conversely, MUC1 attenuates activation of Bax transcription. In concert with these results, MUC1 promotes selection of the p53-dependent growth arrest response and suppresses the p53-dependent apoptotic response to DNA damage. These findings indicate that MUC1 regulates p53-responsive genes and thereby cell fate in the genotoxic stress response.
Human MUC1 carcinoma-associated protein confers resistance to genotoxic anticancer agents
Cancer Cell , 2004; 5(2):163-175; Ren J, Agata N, Chen D, Li Y, Yu W-H, Huang L, Raina D, Chen W, Kharbanda S, and Kufe D.
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The MUC1 transforming protein is overexpressed by most human carcinomas. The present studies demonstrate that the MUC1 C-terminal subunit (MUC1 C-ter) localizes to mitochondria in HCT116/MUC1 colon carcinoma cells and that heregulin stimulates mitochondrial targeting of MUC1 C-ter. We also show that MUC1 attenuates cisplatin-induced (1) release of mitochondrial apoptogenic factors, (2) activation of caspase-3, and (3) induction of apoptosis. Moreover, knockdown of MUC1 expression in A549 lung and ZR-75-1 breast carcinoma cells by MUC1siRNA was associated with increased sensitivity to genotoxic drugs in vitro and in vivo. These findings indicate that MUC1 attenuates the apoptotic response to DNA damage and that this oncoprotein confers resistance to genotoxic anticancer agents.
