The SWI/SNF canonical BAF complex and c-Myc cooperate to promote early fate decisions in CD8+ T cells

Abstract The identification of mechanisms to promote the generation of memory T cells (TMEM) has important implications for vaccination and anti-cancer immunotherapy. Using a CRISPR-based screen for negative regulators of TMEM generation in vivo, we discovered many components of the mammalian canonical SWItch/Sucrose Non-Fermentable (SWI/SNF) complex, also called canonical Brg1/Brg-associated factor (cBAF). cBAF is essential for the differentiation of activated, naïve CD8+ T cells into T effector (TEFF) cells, and loss of cBAF promotes TMEM formation of CD8+ T cells in vivo upon infection with Listeria monocytogenes and influenza A virus (IAV). During the first division of activated CD8+ T cells, we found that cBAF and c-Myc frequently co-assort asymmetrically to the two daughter cells. Daughter cells with high c-Myc are enriched for cBAF expression and display a cell fate trajectory towards TEFF cells, while those with low c-Myc have reduced cBAF, and preferentially differentiate towards TMEM cells. Moreover, the cBAF complex and c-Myc physically interact, and act in concert to establish the chromatin landscape in activated CD8+ T cells. Treatment of naïve CD8+ T cells with an inhibitor of cBAF during the first 48 hours of activation, prior to the generation of chimeric antigen receptor T (CAR-T) cells, markedly improves anti-cancer immunity in a solid tumor model. Our results establish cBAF as a key negative determinant of TMEM cell fate and suggest that manipulation of cBAF early in T cell differentiation can improve adoptive immunotherapy for cancer treatment. Supported by AI123322