PDCD1 and neoplasm: To explore whether the immune escape of MSH2 KO tumors might be linked to immune checkpoint expression, T cell exhaustion, or myeloid immunosuppressive programs, we quantified PD-1, TIM3, TIGIT, CTLA4 and LAG3 immune checkpoints, as well as their corresponding ligand expression in tumor-infiltrating immune cells using flow cytometry and scRNAseq.