Effect of a heat shock protein 90-specific inhibitor on the proliferation and apoptosis induced by VEGF-C in cervical cancer cells

Abstract

The aim of the present study was to investigate the effect of heat shock protein 90 (Hsp90)-specific inhibitor geldanamycin (GA) on the proliferation and apoptosis induced by vascular endothelial growth factor-C (VEGF-C) in cervical cancer cells. HeLa cells (1×10⁶/ml) in the logarithmic growth phase were incubated without serum for 24 h. The cells were pretreated with kinase insert domain receptor antibody (KDR)-Ab (20 μg/ml), phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 (3 μmol/l), mitogen-activated protein kinase (MAPK) inhibitor PD98059 (30 μmol/l) or Hsp90-specific inhibitor GA (10 μmol/l) for 30 min, and then treated with VEGF-C (50 ng/μl) for a further 24 h. The cells were harvested for MTT analysis, annexin V-FITC/propidium iodide double staining for early apoptosis and SDS-PAGE and western blot analysis in order to determine Hsp90, B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax) and cyclin D1 expression. Treatment with VEGF-C alone induced Hsp90 protein expression in HeLa cells at all time-points. Hsp90 expression was increased 3.31-fold in VEGF-C treated HeLa cells, and this increase was attenuated in the treatment groups (2.17-, 1.69-, 1.82-fold in VEGF-C + KDR-Ab, VEGF-C + PD98059 and VEGF-C + LY294002, respectively). The proliferation of the VEGF-C-treated HeLa cells was increased ~2.13-fold, while that of the VEGF-C + GA-treated HeLa cells decreased 0.87-fold (P<0.05). Even low concentrations of GA (0.02 μmol/l) were found to inhibit the Bcl-2 and cyclin D1 protein expression induced by VEGF-C. Therefore, the results indicate that the Hsp90-specific inhibitor GA has a critical role in the proliferation and apoptosis induced by VEGF-C in cervical cancer cells.

Keywords: apoptosis; cervical cancer; heat shock protein 90; proliferation; vascular endothelial growth factor-C.

Figure 1

Western blot analysis results of Hsp90 protein expression bands induced by VEGF-C at different times in HeLa cells. Lane 1: Control; Lane 2: VEGF-C (50 ng/μl) 3 h; Lane 3: VEGF-C (50 ng/μl) 6 h; Lane 4: VEGF-C (50 ng/μl) 12 h; Lane 5: VEGF-C (50 ng/μl) 24 h. Hsp90, heat shock protein 90; VEGF-C, vascular endothelial growth factor-C.

Figure 2

Western blot analysis results of Hsp90 protein expression bands induced by VEGF-C in the presence or absence of various inhibitors in HeLa cells. Lane 1: Control; Lane 2: VEGF-C + KDR-Ab; Lane 3: VEGF-C + PD98059; Lane 4: VEGF-C + LY294002; Lane 5: VEGF-C + GA. Hsp90, heat shock protein 90; GA, geldanamycin; VEGF-C, vascular endothelial growth factor-C.

Figure 3

Western blot analysis results of Bcl-2, Bax and cyclin D protein expression bands in HeLa cells. Lane 1: Control; Lane 2: VEGF-C; Lane 3: VEGF-C + GA; Lane 4: GA. Bcl-2, B-cell lymphoma 2; Bax, Bcl-2-associated X protein; GA, geldanamycin; VEGF-C, vascular endothelial growth factor-C.