Abstract A146: Systematic discovery of immune regulatory mechanisms in tumor cells

Many human cancers are resistant to immunotherapy for reasons that are poorly understood. We used a genome-scale CRISPR/Cas9 screen to identify mechanisms of tumor cell resistance to killing by cytotoxic T-cells, the central effectors of antitumor immunity. Inactivation of >100 genes sensitized mouse B16F10 melanoma cells to killing by T-cells, including Pbrm1, Arid2 and Brd7, which encode components of the PBAF form of the SWI/SNF chromatin remodeling complex. Loss of PBAF function increased tumor cell sensitivity to interferon-γ, resulting in enhanced secretion of chemokines that recruit effector T-cells. Treatment-resistant tumors became responsive to immunotherapy when Pbrm1 was inactivated. In many human cancers, expression of PBRM1 and ARID2 inversely correlated with expression of T-cell cytotoxicity genes, and Pbrm1-deficient murine melanomas were more strongly infiltrated by cytotoxic T-cells. Citation Format: Deng Pan, Aya Kobayashi, Peng Jiang, Guo-Cheng Yuan, X. Shirley Liu, John Doench, Xintao Qiu, Prakash Rao, Henry Long, Myles A. Brown, Kai W. Wucherpfennig, Lucas Ferrari de Andrade, Rong En Tay, Adrienne M. Luoma, Daphne Tsoucas, Klothilda Lim. Systematic discovery of immune regulatory mechanisms in tumor cells [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A146.