PPP1R15A and melanoma: Consistent with our in vitro findings, genes associated with the ATF4 (e.g., ATF4, DDIT3, PPP1R15A and CHAC1), ATF6 (e.g., ATF6B, CALR, SEL1L, and EDEM1) and XBP1 (e.g., SSR3 and DELR1) pathways were significantly enriched in melanoma TILs compared with healthy blood T cells (Fig. 2C and Supplementary Fig. 2B).