CD8A and melanoma: Such an effect has been observed in various syngeneic mouse tumor models such as colon carcinoma, melanoma, or mammary carcinoma, which demonstrated that radiation increased infiltration of tumors with CD8+ T-cells, induced IFN-γ expression in these cells, with IFN-γ then causing PD-L1 expression on tumor cells, ultimately leading to CD8+ T-cell exhaustion.