CD274 and neoplasm: However, when combined with xCT inhibition and anti-PD-1/PD-L1 antibody, SAS enhanced the binding of transcription factors IRF4 and EGR1 to PD-L1 promoter, increased PD-L1 mRNA and protein levels, increased tumor ExoPD-L1 level, and reduced CD8+ T cell activity (47).