Emodin enhances cisplatin sensitivity in non-small cell lung cancer through Pgp downregulation

Abstract

Cisplatin resistance is one of the main causes of chemotherapy failure and tumor progression in non-small cell lung cancer (NSCLC). Emodin has been demonstrated to induce NSCLC cell apoptosis and act as a potential cancer therapeutic agent. However, whether emodin could affect NSCLC cell sensitivity toward cisplatin remains unclear. The present study aimed to determine the effect of emodin and cisplatin combination on the chemosensitivity of NSCLC cells. A549 and H460 cells were treated with different concentrations of cisplatin and/or emodin. Cell Counting Kit-8, fluorescence microscopy, immunofluorescence assays and flow cytometry were used to determine cell proliferation, drug efflux, DNA damage level and cell apoptosis, respectively. P-glycoprotein (Pgp) and multidrug resistance-associated protein 1 (MRP1) expression was detected by western blotting. The results demonstrated that emodin and cisplatin inhibited the proliferation of A549 and H460 cells. Furthermore, emodin inhibited the drug efflux in A549 and H460 cells in a dose-dependent manner. In addition, emodin enhanced cisplatin-induced apoptosis and DNA damage in A549 and H460 cells. Emodin also decreased Pgp expression in A549 and H460 cells in a dose-dependent manner; however, it had no effect on MRP1 expression. Taken together, the results from the present study demonstrated that emodin can increase A549 and H460 cell sensitivity to cisplatin by inhibiting Pgp expression. Emodin may therefore be considered as an effective adjuvant for cisplatin treatment.

Keywords: P-glycoprotein; chemosensitivity; cisplatin; emodin; non-small cell lung cancer.

Figure 1.

Effects of emodin and cisplatin on A549 and H460 cell proliferation. Cell Counting Kit-8 was used to detect A549 and H460 cell proliferation following treatment with different doses of (A) cisplatin, (B) emodin or (C) cisplatin combined with emodin for 48 h. The data are presented as the means ± standard deviation of three independent experiments. *P<0.05, **P<0.01 and ***P<0.001.

Figure 2.

Effect of emodin on the drug efflux of A549 and H460 cells. Following A549 and H460 cell treatment with different concentrations of emodin for 12 h, cells were stained with 5 µM rhodamine 123 for 30 min and fluorescence microscopy was used to detect drug accumulation levels in (A) A549 and (B) H460 cells. **P<0.01 and ***P<0.001.

Figure 3.

Effect of emodin on cisplatin-induced apoptosis in A549 and H460 cells. Following A549 and H460 cell treatment with different concentrations of emodin and/or cisplatin for 24 h, the blank control group was treated with equal amounts of vehicle (DMSO), and cells were stained with an Annexin V-FITC/PI apoptosis detection kit, and flow cytometry was used to detect the cell apoptosis rate in (A) A549 and (B) H460 cells. **P<0.01 and ***P<0.001.

Figure 4.

Effect of emodin on DNA damage in A549 and H460 cells. Following A549 and H460 cell treatment with different concentrations of emodin and/or cisplatin for 24 h, the blank control group was treated with equal amounts of vehicle (DMSO), immunocytochemical analysis was used to analyze γ-H2A.X foci formation in (A) A549 and (B) H460 cells. *P<0.05 and **P<0.01.

Figure 5.

Effect of emodin on the expression of Pgp and MRP1 in A549 and H460 cells. Following A549 and H460 cell treatment with different concentrations of emodin for 24 h, western blotting was used to detect Pgp and MRP1 expression in (A) A549 and (B) H460 cells. **P<0.01 and ***P<0.001. Pgp, P-glycoprotein; MRP1, multidrug resistance-associated protein 1.