CD274 and neoplasm: While IFN-γ is a canonical inducer of PD-L1, previous studies show that bacterial products, including heat-killed S. aureus, can stimulate IFN-γ-producing lymphocytes [43,44,45,46,47]., and that microbial components can upregulate tumor PD-L1 in vivo [48,49,50,51,52].