CPA4 and non-small cell lung carcinoma: The Real-Time qPCR results showed that PD-L1 mRNA levels were increased by overexpressing circ-CPA4 and decreased by knocking down circ-CPA4 in NSCLC cells (A549, H1299, SK-MES-1 and Calu-3) (Fig. 4a-d), which were validated by the Western Blot assay at translational level in A549 and H1299 cells (Fig. 4e, f).