PDCD1 and colorectal cancer: Equally, Germano and his team also used CRISPR-Cas9 to construct B2M KO MMRd colorectal cancer cell lines (MC38-MMRd-B2M-/-and CT26-MMRd-B2M-/-) (74), subcutaneously inoculated the cells into C57BL/6 mice, and administered anti-PD-1 and anti CTLA-4 antibodies and found that B2M-deficient loaded mice treated with ICIs showed significant tumor regression and that in CD8+ T-cell depleted mice, ICIs remained efficacious against MMRd B2M-deficient tumors.