Exosomal circ_0032704 confers sorafenib resistance to hepatocellular carcinoma and contributes to cancer malignant progression by modulating the miR‐514a‐3p/PD‐L1 pathway

Abstract Purpose This study aims to explore the role of circ_0032704 in sorafenib‐resistant hepatocellular carcinoma (HCC). Methods The expression of circ_0032704, miR‐514a‐3p, and programmed death‐ligand 1 (PD‐L1) mRNA was detected by quantitative real‐time PCR (qPCR). The expression of multidrug resistant‐related proteins, migration/invasion‐related proteins, exosome‐related proteins, and PD‐L1 protein was detected by western blot. Cell viability was detected by CCK‐8 assay. Cell proliferation, migration, and invasion were assessed by EdU assay, wound healing assay, and transwell assay. The binding between miR‐514a‐3p and circ_0032704 or PD‐L1 was verified by RIP assay, pull‐down assay, and dual‐luciferase reporter assay. Cell‐ or serum‐derived exosomes were isolated and identified by TEM and NTA. Xenograft models were established to determine the effect of circ_0032704 on drug resistance in vivo. Results Circ_0032704 was overexpressed in sorafenib‐resistant HCC tissues and cells. Circ_0032704 knockdown reduced sorafenib resistance in HCC cells and inhibited cell proliferation, migration, and invasion of sorafenib‐resistant HCC cells, while these effects were reversed by PD‐L1 overexpression. We found that circ_0032704 positively regulated PD‐L1 expression via targeting miR‐514a‐3p. Exosomes with circ_0032704 inhibition reduced sorafenib resistance in HCC cells and inhibited cell proliferation, migration, and invasion of sorafenib‐resistant HCC cells. Exosomes with circ_0032704 inhibition also inhibited tumor growth in vivo. The expression of circ_0032704 in exosomes was stable and possessed diagnostic value. Conclusion Circ_0032704 enhanced sorafenib resistance in HCC and promoted the malignant development of sorafenib‐resistant HCC. Circ_0032704 could be transported by exosomes, and exosomal circ_0032704 had diagnostic value.