miR-21 modulates paclitaxel sensitivity and hypoxia-inducible factor-1α expression in human ovarian cancer cells

Abstract

Drug resistance is a major problem encountered in the treatment of ovarian cancer. Previous studies have demonstrated that in several types of cancer the overexpression of the multidrug resistance 1 (MDR1) gene is mainly associated with drug resistance. The present study aimed to investigate the role of miR-21 in the development of drug resistance in ovarian cancer cells. The expression levels of miR-21 in the ovarian cancer A2780 and A2780/taxol cell lines were detected by stem-loop real-time PCR. A2780 and A2780/taxol cells were transfected with mimics or inhibitors of miR-21 or negative control RNA. The expression levels of P-glycoprotein (P-gp) and hypoxia-inducible factor-1α (HIF-1α) proteins were assessed by western blot analysis. Drug sensitivity was analyzed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The expression levels of miR-21 and P-gp were upregulated to a greater extent in the paclitaxel-resistant ovarian cancer A2780/taxol cell line compared with the parental A2780 cell line. Transfection of A2780/taxol cells with inhibitors of miR-21 decreased the expression levels of the P-gp and HIF-1α proteins, and increased the sensitivity of the A2780/taxol cells to paclitaxel. The expression levels of P-gp were additionally increased; however, the sensitivity of the miR-21 mimic-treated A2780 cells to paclitaxel was decreased. miR-21 may be involved in the development of drug resistance and the regulation of MDR1/P-gp expression, at least in part, by targeting HIF-1α in ovarian cancer cells.

Keywords: hypoxia-inducible factor-1α; miR-21; ovarian cancer; paclitaxel resistance.

Figure 1

Expression levels of P-gp and miR-21 in A2780 and A2780/taxol cells. (A) P-gp protein levels in A2780 and A2780/taxol cells. (B) miR-21 levels in A2780 and A2780/taxol cells. ^*P<0.05 vs. A2780 cells. P-gp, P-glycoprotein.

Figure 2

miR-21 modulates sensitivity to paclitaxel. (A) miR-21 levels in A2780 cells transfected with miR-21 mimics. (B) Paclitaxel sensitivity of A2780 cells transfected with miR-21 mimics or NC RNA. (C) miR-21 levels in A2780/taxol cells transfected with miR-21 inhibitors. (D) Paclitaxel sensitivity of A2780/taxol cells transfected with miR-21 inhibitors or NC RNA. ^*P<0.05 vs. NC group. NC, negative control.

Figure 3

Effect of miR-21 on the expression levels of MDR1/P-gp. (A and B) P-gp protein levels in A2780 cells transfected with miR-21 mimics. (C and D) P-gp protein levels in A2780/taxol cells transfected with miR-21 inhibitors. ^*P<0.05 vs. NC group. P-gp, P-glycoprotein; MDR1, multidrug resistance gene 1.

Figure 4

HIF-1α is regulated by miR-21. (A and B) HIF-1α protein levels in A2780 cells transfected with miR-21 mimics. (C and D) HIF-1α protein levels in A2780/taxol cells transfected with miR-21 inhibitors. ^*P<0.05 vs. NC group. HIF-1α, hypoxia-inducible factor-1α.

Figure 5

HIF-1α is important in paclitaxel resistance. (A and B) HIF-1α protein levels in A2780/taxol cells transfected with siHIF-1α or NC RNA. (C and D) P-gp protein levels in A2780/taxol cells transfected with siHIF-1α or NC RNA. (E) Paclitaxel sensitivity of A2780/taxol cells transfected with siHIF-1α or NC RNA. ^*P<0.05 vs. NC group. HIF-1α, hypoxia-inducible factor-1α; NC, negative control; siHIF-1α, small interfering hypoxia-inducible factor-1α.