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The immune checkpoint ligand PD-L1 and the transmembrane mucin MUC1 are upregulated in triple-negative breast cancer (TNBC), where they contribute to its aggressive pathogenesis. Here, we report that genetic or pharmacological targeting of the oncogenic MUC1 subunit MUC1-C is sufficient to suppress PD-L1 expression in TNBC cells. Mechanistic investigations showed that MUC1-C acted to elevate PD-L1 transcription by recruitment of MYC and NF-κB p65 to the PD-L1 promoter. In an immunocompetent model of TNBC in which Eo771/MUC1-C cells were engrafted into MUC1 transgenic mice, we showed that targeting MUC1-C associated with PD-L1 suppression, increases in tumor-infiltrating CD8+ T cells and tumor cell killing. MUC1 expression in TNBCs also correlated inversely with CD8, CD69, and GZMB, and downregulation of these markers associated with decreased survival. Taken together, our findings show how MUC1 contributes to immune escape in TNBC, and they offer a rationale to target MUC1-C as a novel immunotherapeutic approach for TNBC treatment. Significance: These findings show how upregulation of the transmembrane mucin MUC1 contributes to immune escape in an aggressive form of breast cancer, with potential implications for a novel immunotherapeutic approach. Cancer Res; 78(1); 205–15. ©2017 AACR.

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.

Introduction: MUC1, an O-glycoprotein membrane-bound mucin, is overexpressed in renal clear-cell carcinomas (CRCC) with correlation to two major prognostic factors, Tumor-Node-Metastasis stage and nuclear Fürhman grade. Previously, we have shown that (i) MUC1 was significantly overexpressed in metastatic CRCC vs non-metastatic CRCC and (ii) MUC1 is a target gene of HIF-1 transcription factor which is a part of the hypoxia pathway, the main renal carcinogenetic pathway. Furthermore, CRCC is highly resistant to common systemic chemotherapies. Material and method: To better understand the roles of MUC1 in CRCC, we used two renal cell lines expressing MUC1 (786-O cells) or not (ACHN cells). 786-O cells were stably transfected with shRNA targeting MUC1 while ACHN cells with full-length MUC1. Proliferation, drug resistance, migration and invasion properties were studied in vitro in the different cellular clones using MTS cell proliferation assay, wound healing assay and Boyden chambers coated with Matrigel, respectively. Signaling pathways were screened by proteome profiler and western blot. Results and discussion: We showed that MUC1 expression was associated with increased invasion and migration properties of renal carcinomatous cells and a decrease of cell-cell interactions. MUC1 overexpressing cells (i) expressed higher levels of anti-apoptotic factors and MDR genes involved in chemoresistance processes and (ii) were more resistant to chemotherapeutic drugs. Conclusion: Our results show that MUC1 plays a role in biological properties of renal cancer cells suggesting important function for this mucin in tumour progression and chemo-resistance. Our data confirm its potential as a therapeutic target in this type of cancer. Citation Format: Kelly Gaudelot, Viviane Gnemmi, Audrey Bouillez, Jean-Baptiste Gibier, Mélanie Fanchon, Justine Woszczyk, Brigitte Hémon, Isabelle Van Seuningen, Sébastien Aubert, Michael Perrais. The MUC1 membrane-bound mucin increases tumor cell properties and chemoresistance in renal clear cell carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5047.

MUC1, an O-glycoprotein membrane-bound mucin, is overexpressed in clear-cell carcinomas (cRCC) with correlation to two prognostic factors, tumor-node metastasis stage and nuclear Fürhman grade. Previously (Aubert et al, Cancer Res 2009), we have shown that MUC1 was significantly overexpressed in metastatic cRCC vs non-metastatic cRCC and MUC1 is a target gene of HIF-1 transcription factor which is a part of the hypoxia pathway, the main renal carcinogenetic pathway. To better understand the roles of MUC1 in cRCC, we used two renal cell lines expressing MUC1 (Caki-2) or not (ACHN cells). Caki-2 cells were stably transfected with shRNA targeting MUC1 and ACHN cells with an expressing vector containing MUC1 cDNA. Flow cytometry assay and confocal microscopy showed a homogenous membrane expression of MUC1 but also in the nucleus. In vitro studies underlined MUC1 role in the invasion, migration and anchorage-independent growth. In contrast, MUC1 had no role in proliferation and clonogenicity. Cellular agreggation test showed that MUC1 expression is associated with a decrease of cell-cell interactions. Phospho-JNK and phospho-p38 levels were higher in MUC1 expressing cells. Transcriptomic analysis results performed on 44K Agilent Microarrays suggest that MUC1 is a candidate in chemoresistance. Subcutaneous xenograft will be also performed. Our results show that MUC1 plays a role in biological properties of renal cancer cells suggesting the important function for this mucin in tumor progression and confirms its potential as a therapeutic target in this type of cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2737. doi:10.1158/1538-7445.AM2011-2737

Accumulating data suggest that epithelial mesenchymal transition (EMT) is involved in cancer progression. Sarcomatoid carcinoma represents a high-grade transformation and an EMT-like pattern. Up to 8% of conventional renal cells cancers (cRCC) present with sarcomatoid carcinoma component that portends a worse prognosis. MUC1, a membrane-bound glycoprotein is known to be over-expressed in cRCC with correlation to prognosis. Indeed, we showed that MUC1 overexpression is correlated with a metastatic phenotype using tissue microarray sampling 27 cRCC of same TNM stage. Also, we demonstrated in a series of 15 RCC with sarcomatoid component, the loss of epithelial markers and the acquisition of mesenchymal markers compared to conventional carcinomatous areas. MUC1 was significantly overexpressed along with Snai1, a major actor of EMT, in sarcomatoid component. So, we hypothesized that MUC1 could be regulated by Snai1. Bioinformatic analyses revealed two Snai1 E-boxes at -84/-72 on MUC1 promoter. Cotransfection studies of MUC1 promoter and Snai1 expression vectors in renal cells lines showed an induction of MUC1 transcriptional activity by luciferase assays. Mutagenesis site-directed of both Snai1 E-boxes in renal cells lines induced loss MUC1 transcriptional activity. By chromatin immunoprecipation assay and gel shift analysis we will demonstrate a direct interaction between Snai1 and MUC1 promoter. In conclusion, all these data revealed that MUC1, usually considered as an epithelial marker, is overexpressed during cancer linked EMT process with a direct regulation by Snai1 suggesting that MUC1 plays a role in renal cancer progression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5250. doi:10.1158/1538-7445.AM2011-5250

MUC1, an O-glycoprotein membrane-bound mucin, is overexpressed in renal clear-cell carcinomas (CRCC) with correlation to two major prognostic factors, Tumor-Node-Metastasis stage and nuclear Fürhman grade. Previously (Aubert et al., Cancer Res 2009), we have shown that (i) MUC1 was significantly overexpressed in metastatic CRCC vs non-metastatic CRCC and (ii) MUC1 is a target gene of HIF-1 transcription factor which is a part of the hypoxia pathway, the main renal carcinogenetic pathway. To better understand the roles of MUC1 in CRCC, we used two renal cell lines expressing MUC1 (Caki-2 cells) or not (ACHN cells). Caki-2 cells were stably transfected with shRNA targeting MUC1 and ACHN cells with an expressing vector containing MUC1 cDNA. Proliferation, migration and invasion properties were studied in vitro in the different cellular clones using Boyden chambers coated with Matrigel, wound healing assay and MTS cell proliferation assay, respectively. Our results showed that (i) MUC1 expression was associated with an increase of invasion and migration properties of renal carcinoma cells whereas no effect on proliferation and apoptotic rate was observed and (ii) levels of phospho-JNK were higher in MUC1 expressing cells. Results of (i) transcriptomic analysis on 44K Agilent microarrays, (ii) signaling pathway screening and (iii) subcutaneous xenografts will be presented. Our results show that MUC1 plays a role in biological properties of renal cancer cells suggesting important function for this mucin in tumour progression and confirms its potential as a therapeutic target in this type of cancer. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2457.