Fig. 4.

Circ-CPA4 affected intracellular and extracellular PD-L1 in NSCLC cells by targeting let-7 miRNA. Circ-CPA4 positively regulated PD-L1 mRNA levels in a A549, b H1299, c SK-MES-1 and d Calu-3 cells, respectively. e, f Circ-CPA4 positively regulated PD-L1 protein levels in A549 and H1299 cells. g, h Overexpression of circ-CPA4 upregulated PD-L1 protein levels in A549 and H1299 cells by downregulating let-7 miRNA. i Isolation of exosomes containing PD-L1 from the supernatants collected from A549 and H1299 culture system, the exosomes were observed and photographed by electron microscope. j, k Knock-down of circ-CPA4 inhibited exosomal PD-L1 expressions by upregulating let-7 miRNA. Each experiment repeated at least 3 times. *P < 0.05, **P < 0.01, NS means no statistical significance