β-Elemene Prevented Multidrug Resistance of Small Cell Lung Cancer Cell Line H446: Targeting the Autophagy Regulation of MiR-199a-5p is the Mechanism of Cisplatin Resistance.

Abstract

Background Multidrug resistance (MDR) in small cell lung cancer (SCLC) is a clinical dilemma in chemotherapy. A natural compound, β-elemene has been found to inhibit MDR cancers. We hypothesized that β-elemene regulated cisplatin-resistant SCLC by targeting autophagy-related miRNA miR-199a-5p. Methods We assessed the IC50 of multiple chemotherapeutic agents toward SCLC cells H446 and MDR SCLC cells H446/EP with or without β-elemene using CCK-8. We overexpressed (OE) and knocked down (KD) miR-199a-5p in H446 and H446/EP and determined the expression of miR-199a-5p, autophagy-related proteins, and the formation of autophagolysosomes using QPCR, western blotting, and MDC staining respectively. We validate the binding of miR-199a-5p to p62 using the Dual-Luciferase assay. Results β-Elemene decreased drug resistance of H446 to cisplatin, etoposide, paclitexal, epirubicin, irinotecan, and vinorelbine. Cisplatin increased LC3II/LC3I, ATG5, p62, and the formation of autophagolysosomes in H446 cells, but not in H446/EP cells, and these effects were blocked by β-elemene. The OE of miR-199a-5p reduced cisplatin-induced increase of LC3II/LC3I, ATG5, p62, and the formation of autophagolysosomes while the KD of miR-199a-5p did the opposite. the OE of miR-199a-5p reduced the luciferase signal of wild-type p62, but not that of p62 with mutations at the predicted binding site. The effect of β-elemene on cisplatin-induced autophagy was validated in OE-H446 and KD-H446/EP. Conclusions β-Elemene prevented MDR in H446 and it prevents cisplatin resistance of H446 by targeting the autophagy regulation of miR-199a-5p.