Abstract 492: Identification of a novel complex MUC1/CIN85 involved in invasion and migration of breast cancer cells

Abstract

Abstract MUC1 is a transmembrane glycoprotein abnormally expressed in human adenocarcinoma. The extracellular domain of MUC1 contains a variable number of tandem repeats 20aa in length (VNTR region) which is fully glycosylated in normal epithelia and underglycosylated in tumor cells. We recently demonstrated that tumor form of MUC1 increases the accessibility of the VNTR peptide backbone to other proteins thus affecting protein-protein interactions and intracellular signaling. By using MALDI-TOF, we identified CIN85 as one of the proteins that bind the extracellular domain of MUC1. CIN85 is an adaptor protein involved in multiple cellular processes including signal transduction, vesicle-mediated transport, cytoskeleton remodelling, invasion and migration of cancer cells. Structurally, CIN85 contains three SH3 domains, a proline-rich region and a C-terminal coiled-coil region. The SH3 domain of CIN85 recognizes a specific sequence PXXAP that corresponds to the PDTRP sequence in the 20 amino acid tandem repeat in the MUC1 VNTR. Co-immunoprecipitation assay and confocal immunofluorescence confirmed that MUC1 and CIN85 co-localize in MUC1-transfected RMA (mouse T cell lymphoma) and IG10 (mouse ovarian carcinoma) cells and in human breast cancer cells MDA-MB-231 and MDA-MB-435 that express endogenous MUC1 and CIN85. Subcellular protein fractionation revealed that CIN85 and MUC1 co-localize mainly at plasma membrane but also in the cytosol. To better understand the function of CIN85/ MUC1 complex we analyzed their expression by immunohistochemistry and confocal immunofluorescence in human tissue microarray (TMA) composed of 31 breast cancer samples and 5 adjacent normal tissue. Hypoglycosylated MUC1 and CIN85 are over-expressed and co-localize in early and advanced clinical stage of breast cancer. Interestingly, CIN85 and MUC1 were localized to invadopodia-like structures suggesting a potential role in cancer cell invasion. siRNA-mediated silencing of CIN85 and/or MUC1 revealed that MUC1 enhances CIN85-dependent cell invasion and migration of breast cancer cells. In contrast, ectopic expression of MUC1 reduces the motility induced by CIN85. In conclusion, our finding suggest that the novel complex CIN85/MUC1 play a critical role in invadopodia formation and have control on invasive and metastatic potential of breast cancer cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 492. doi:1538-7445.AM2012-492