CD274 and neoplasm: Several mechanisms that regulate PD-L1 expression in cancer cells have been described, including the presence of inflammatory mediators like the INF-γ [17] within the tumor microenvironment, the loss of phosphatase and tensin homologue (PTEN) with consequent phosphatidylinositol-3-OH kinase (PI3K) activation [18], and promotion of cancer cell proliferation [19].