CD274 and neoplasm: Also, PD-1/PD-L1 pathway activation may negatively regulate the Th1 cytokine family (e.g., IFN-γ, IL-12) to promote immune response and positively regulate the Th2 cytokine family (e.g., IL-10, TGF-β) to suppress the immune response, thus leading to immune suppression of the tumor microenvironment (12).