CD274 and neoplasm: In tumor cells with ectopic PD-L1 overexpression, CMTM6-mediated PD-L1 regulation predominantly modulates T cell activation in T cell-tumor cell cocultures.39,40 However, in tumor cells expressing only endogenous PD-L1, as tested in this study, CMTM6-mediated CD58 expression becomes the dominant factor.