While the exact mechanisms of how PD-L1 is upregulated in cancer cells remain unclear, previous evidence suggests that the transcription factor YY1[78], phosphatases Src homology region 2 domain-containing phosphatase-1 and 2 (SHP 1/2)[77], and cyclin-dependent kinases 4 and 6 (CDK 4/6)[79] all regulate PD-L1 expression in some way. This evidence concerns the gene CD274 and cancer.