CD274 and lung cancer: Subsequently, our findings further showed that down-regulated CircCHST15 regulated distribution of T cell subtypes and inhibited the expression of PD-L1 in the tumor tissues, thus, we speculated that the effect of CircCHST15 on lung cancer might be associated with the immune system, as PD-L1 has critical functions in the immune response and immune escape in different cancers (19–22).