Abstract 3965: Epithelial membrane protein-2 is a novel regulator of immune editing in breast cancer

Cancer immuno-editing is a process that describes the interaction between immune cells and tumor cells. This interaction can result in elimination of a developing tumor, tumor dormancy, or tumor cells that are capable of surviving in an immune-competent host. We have recently uncovered a novel mechanism of immunoediting by the tetraspan protein Epithelial membrane protein or EMP2. We propose that EMP2 serves as a bridge between innate and adaptive immunity via tumor mediated type I interferon expression. Most tumor cells evade the immune system through suppression or ignorance. EMP2 levels promote type I interferon expression which was found to correlate with PDL1 expression in a number of cell lines. Concordantly, in vivo, in multiple breast cancer cell lines, EMP2 promoted tumor growth. In contrast, reduction in EMP2 levels correlated with a reduction in tumor size and a corresponding increase in tumor associated macrophages. Given that tumors with lower levels of EMP2 grow poorly, we hypothesized that targeting EMP2 may provide a therapeutic benefit. Recently, we have developed a panel of novel IgG1 monoclonal antibodies to EMP2 and tested their ability to treat both xenograft and syngeneic mouse models. Our results show that anti-EMP2 IgG1 significantly reduces tumor load in both models in part through the recruitment of M1 macrophages. To explore this observation more fully, experiments using murine syngeneic models were employed. Anti-EMP2 therapy elicits a robust ADCC response, producing an immune infiltrate rich in macrophages, NK cells, and lymphocytes. In addition, we show that CD8 cells show reduced exhaustion in the presence of anti-EMP2 antibodies. Conclusions: EMP2 is a protein upregulated in a number of cancers in women including breast, ovarian, and endometrial tumors. Our work collectively show that EMP2 is a novel immune regulator where its expression creates an immunosuppressive tumor microenvironment. We thus predict that targeting EMP2 may improve therapeutic outcomes for cancers in women. Citation Format: Jessica Tsui, Negin Ashki, Yuling Chang, Deven Patel, Jasmine Sjarif, Madhuri Wadehra. Epithelial membrane protein-2 is a novel regulator of immune editing in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3965. doi:10.1158/1538-7445.AM2017-3965