Objective: To investigate whether the proteasomes inhibitor MG262 exerts its anti-cancer function by inducing apoptosis in human ovarian cancer cells, and whether the extracellular signal regulated kinase (ERK) signaling pathway is involved in the regulation of apoptosis induction.
Method: Human ovarian cancer cell line SKOV3 was incubated with different concentrations of MG262 for 24 and 48 hours. Cell viability was evaluated with 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay at different time points of culturing. Flow cytometry was used to detect cell apoptosis rate. The expression of vascular endothelial growth factor (VEGF) was evaluated with western blot and enzyme-linked immunosorbent assay (ELISA). Western blot was used to detect the expression of phosphorylated ERK (p-ERK).
Results: The viability of SKOV3 cells was decreased by MG262 in a concentration-dependent fashion (P < 0.05). After 24 h incubation with MG262 at 1, 10, 20, 40, 60 and 80 nmol/L, the viability rates of SKOV3 were (94.6 +/- 3.1)%, (92.7 +/- 3.7)%, (89.5 +/- 7.7)%, (84.2 +/- 5.1)%, (82.0 +/- 7.4)% and (76.8 +/- 11.0)% respectively, and after 48 h incubation, those figures were further decreased to (91.3 +/- 10.1)%, (86.8 +/- 4.5)%, (74.6 +/- 4.2)%, (56.8 +/- 2.1)%, (49.3 +/- 4.5)% and (37.4 +/- 5.4)%, respectively (P < 0.05). Apoptosis rate of SKOV3 cells induced by MG262, PD98059 or their combination was (30.7 +/- 4.3)%, (26.8 +/- 8.6)% and (50.3 +/- 10.6)%, respectively, which were significantly different compared with controls (P < 0.05). In contrast to SKOV3 cells, apoptosis rate of 293T cells induced by MG262, PD98059 or their combination was (14.5 +/- 5.3)%, (16.2 +/- 7.5)% and (10.8 +/- 7.3)%, respectively, which were not significantly different compared with controls (P > 0.05). p-ERK expression decreased gradually in a time-dependent manner. And wild-type p53 expression was not significantly different. There was no significant difference between experimental and control 293T cells (P < 0.05). In addition, MG262 down-regulated VEGF secretion and expression in SKOV3 cells (P < 0.05).
Conclusions: Proteasome inhibitors can induce apoptosis and inhibit cell proliferation and angiogenesis through ERK signal pathway in SKOV3 cells.