CD274 and cancer: Previous data suggested that circ-CPA4 [34] and PD-L1 [22] served as oncogenes, while let-7 miRNA acted as tumor suppressor [28] in cancer development, and there existed potential regulating mechanisms among circ-CPA4, let-7 miRNA and PD-L1 in cancer cells [29, 34], which were validated in this study in NSCLC cells.