CD8A and neoplasm: CircCHST15 was found to be targeting miR-155-5p and miR-194-5p to down-regulate their expression, and the down-regulated miRNA further inhibits PD-L1 expression in tumor tissues, At the same time, circCHST15 decreased CD8+ T cells in the blood and tumors of mice and increased Treg cells in mice tumors.