KRAS and melanoma: The observation of constitutive PD-L1 expression in the KRAS G13D but not in the NRAS Q61K melanoma model is further consistent with findings of elevated PD-L1 levels in tumors with activating KRAS mutations and with studies demonstrating elevated PD-L1 expression in non-small-cell lung cancers with activating EGFR mutations and/or overexpression of EGFR [28,29,30,31,32].