Abstract P3-05-18: The complex landscape of breast cancer immune evasion and its implications to personalized and combined immunotherapy

Abstract

Abstract Cancer immunotherapy activates the patient's immune system to recognize and kill cancer cells. The efficacy of immunotherapy in human breast cancer (BRCA) is hindered by the poor understanding of the immune system's anti-tumor response and tumor evasive mechanisms, and the lack of optimized treatment regimens for each BRCA patient. There are 6 known evasion mechanisms (M) by which tumors can escape immune surveillance. M1: immunosuppression via interleukin 10 (IL-10) and tumor growth factor beta (TGF-β); M2: induction of tolerance by cytotoxic T-lymphocyte associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1) and its ligands (PD-L1/PD-L2), and interferon gamma (IFN-γ); M3: apoptosis resistance via the expression of anti-apoptotic molecules, namely baculoviral IAP repeat-containing protein 3 (BIRC3), TNF receptor associated factor 1 (TRAF1), and TNF alpha induced protein 3 (TNFAIP3); M4: counterattack via decoy death receptors; M5: impaired antigen presentation by decreasing beta 2 microglobulin (B2M) and human leukocyte antigens A and B expression (HLA-A and HLA-B); and M6: ignorance caused by the absence of a danger signal or an antigen. Yet, which mechanisms or combination of mechanisms BRCA tumors utilize is unknown. Moreover, the currently used biomarkers for the choice of immunotherapy are not ideal, as for example, not all PD-L1+ patients respond to anti-PD-L1 treatment, and certain PD-L1- patients respond. Thus, there is a need for more precise biomarkers. Using the sequential biclustering method on the RNA-sequenced data of BRCA from The Cancer Genome Atlas (TCGA), eighty-one percent of BRCA patients were grouped into 7 different clusters (CL) of immune evasion subtypes. We found that the majority of breast cancer tumors utilize multiple immune evasion mechanisms. Tumors may use from 1 up to 4 combinatorial mechanisms simultaneously. We also identified classifier genes that would help sort patients based on their evasion mechanisms, and guide the choice of immunotherapy. This is especially important since the immune evasion molecules may not be the ideal biomarkers for the best choice of immunotherapy. Moreover, we showed that triple negative breast cancer (TNBC) patients were significantly associated with CL2 (M5). Citation Format: Bou-Dargham MJ, Liu Y, Sang Q-XA, Zhang J. The complex landscape of breast cancer immune evasion and its implications to personalized and combined immunotherapy [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-05-18.