Reversal Of Drug Resistance By β-elemene In Erlotinib-resistant Human Non-small Cell Lung Cancer A549 Cells(A549/ER): A Preliminary Experimental Study

Background and Objective:β-elemene(β-ELE) is a new anticancer drug extracted from Curcuma zedoaria Roscoe that has been widely used to treat malignant tumors. Recent studies reported that β-ELE can reverse the durg resistance of tumor cells. Up to now, there are no reports about the reversal of erlotinib resistance by β-ELE in human non-small cell lung cancer(NSCLC) cells. Therefore, this study intends to investigate the effects of β-ELE on erlotinib-resistant human NSCLC A549/ER cells in vitro and its possible mechanism. Methods:The sensitivity of A549/ER cells to erlotinib, the cytotoxicity of β-ELE on the growth of A549/ER cells, and the effects of β-ELE on the reversal of drug resistance in A549/ER cells in vitro were determined by MTT assay. Cell apoptosis was assessed by flow cytometry with Annexin V-FITC/PI double staining. Cell cycle phase distribution analysis was analyzed by flow cytometry with PI staining. Intracellular Rhodamine 123(Rh123) fluorescence intensity was detected by flow cytometry, and the expression of P-glycoprotein(P-gp) was detected by Western blot analysis. Results:A549/ER cells had the stable drug-resistance to erlotinib; β-ELE inhibited the proliferation of A549/ER cells in a time- and dose-dependent manner. β-ELE enhanced the sensitivity of A549/ER cells to erlotinib and reversed the drug resistance in A549/ER cells. Non-toxicity doses(15 μg/m L) of β-ELE alone nearly had no effects on cell apoptosis induction and cell cycle arrest. However, it can cause obviously cell apoptosis and G0/G1 phase arrest when 15 μg/m L β-ELE combined with 10 μmol/L erlotinib. The results of Rh123 retention test showed that 15 μg/m L β-ELE can effectively reduce the efflux of Rh123 from A549/ER cells and increase the intracellular accumulation of Rh123. In addition, the results of Western blot analysis demonstrated that 15 μg/m L β-ELE can obviously decrease the expression level of P-glycoprotein. Conclusion:β-ELE can reverse drug resistance in erlotinib-resistant human NSCLC A549/ER cells in vitro, which may involves the decreased expression of P-gp, the inhibition of P-gp dependent drug efflux, and the increased concentration of anticancer drugs in the cells. Based on the preliminary experimental results in this study, we believe that if the reversal of drug resistance by β-ELE in erlotinib-resistant human NSCLC cells can be supported by data from clinical trials, it will exert positive impacts on improving the therapeutic effects towards erlotinib-resistant NSCLC patients.