To understand how the high somatic mutational load caused by the MMR deficiency or the DNA polymerase mutation would affect anti-tumor immunity or pro-tumorigenic network in the tumor microenvironment, we examined the expression profiles of 11 immune-related genes in the 8 tumors, including CD4, CD8, TCRβ (TRB), granzyme A (GZMA), perforin 1 (PRF1), OX40, FOXP3, IL10, TIM3, PD-1 ligand-1 (PD-L1), and PD-1 as shown in a heatmap in Figure 1A. The gene discussed is PRF1; the disease is mismatch repair cancer syndrome 1.