Cytolytic activity correlates with the mutational burden and deregulated expression of immune checkpoints in colorectal cancer.

Background: Microsatellite unstable colorectal cancers (MSI+ CRCs) expressing PD-L1, respond to anti-PD-1 or anti-PD-L1 checkpoint blockade, whereas microsatellite-stable tumors do not respond the same. Our aim was to examine how the immune landscape relates to different aspects of the CRC's biology, including neoepitope burden.

Methods: We used TCGA data to stratify patients based on a cytolytic T-cell activity expression index and correlated immune cytolytic activity (CYT) with mutational, structural, and neoepitope features of each tumor sample.