IFNG and neoplasm: While PD-L1 upregulation in response to IFNγ expression and T-cell infiltration in the tumor immune microenvironment is a strong, positive biomarker for anti-PD1 monocolonal antibody responsiveness, a subset of tumors upregulate PD-L1 intrinsically in the absence of infiltrating immune cells and these tumors tend to be associated with both worse prognosis and resistance to anti-PD1 monotherapy [70].