Low-dose fractionated radiation reverses cisplatin resistance in ovarian cancer cells via PI3K/AKT/GSK-3β signaling

Objective To investigate whether low-dose fractionated radiation(LDFRT) could enhance cisplatin sensitivity in drug-resistant human ovarian cancer cells SKOV3/DDP, and to further explore the underlying mechanism.Methods SKOV3/DDP ovarian cancer cells were divided into three groups as follows: control, LDFRT, and conventional-dose radiation groups. Cells from all three groups were treated with different concentrations of cisplatin(0, 1.25, 2.5, 5, 10, and 20 μg/m L) for 48 h. The proliferation inhibition rate was investigated using the cell counting kit 8(CCK8). The rate of apoptosis was determined by flow cytometry(FCM). Protein levels of AKT, P-AKT, GSK-3β, P-GSK-3β, P21, cyclin D1, and P27 were examined by Western blotting. Results As expected, LDFRT significantly reduced the half-maximal inhibitory concentration(IC50) of cisplatin and promoted apoptosis in SKOV3/DDP cells. Moreover, in the LDFRT group, protein levels of P-AKT, P-GSK-3β, and cyclin D1 were markedly decreased, those of P21 and P27 were greatly increased, and total AKT and GSK-3β levels showed no significant difference compared to those in both the control and conventional-dose radiation groups.Conclusion LDFRT sensitizes resistant SKOV3/DDP ovarian cancer cells to cisplatin through inactivation of PI3 K/AKT/GSK-3β signaling.

Effect of low dose fractionated radiation on reversing cisplatin resistance in ovarian carcinoma via VEGF and mTOR

Objective To investigate the mechanism of low-dose fractionated radiation on reversing cisplatin resistance in ovarian carcinoma via vascular endothelial growth factor(VEGF) and mammalian target of rapamycin(mTOR) in vivo.Methods Human cisplatin-resistant ovarian carcinoma cells(SKOV3/DDP) were injected into nude mice to establish ovarian cancer xenografts. The mice were randomly divided into three groups: a control group, a low-dose fractionated radiation(LDRFT) group, and a conventional-dose radiation group. Each group was exposed to 0 cGy, 50 cGy, and 200 cGy radiation, respectively, for 4 weeks, up to a total of 8.0 Gy. Mice in the LDFRT group were irradiated twice daily with 6 hour intermissions on day 1 and 2 of every week for a total of 4 weeks. Conventional-dose group mice were given a single 200 cGy radiation dose on the first day each week for a total of 4 weeks. Maximum horizontal and vertical diameters of the tumors were measured every other day and used to create a tumor growth curve. After 4 weeks of irradiation, we dissected the tumor tissue and calculated the tumor inhibition rate. RT-PCR detected the expression of VEGF and m TOR, and Western blots detected the expression of corresponding proteins.Results Both LDRFT and conventional-dose radiation inhibited the growth of tumor cells, and growth of tumors in the two radiation groups compared with growth in the control group were significantly different(P < 0.05). The rate of tumor inhibition in the LDFRT group(37.5603%) was lower than in the conventionaldose group(47.4446%), but there was no significant difference(P 0.05). Compared with the other two groups, the m RNA expression of VEGF was significantly lower in the LDFRT group(P < 0.05), but there was no obvious difference between the conventional-dose and control groups. There was no obvious difference in the m RNA expression of m TOR among the three groups, but the expression of the protein p-m TOR was lower in the LDFRT group(P < 0.05), as confirmed by Western blotting.Conclusion LDFRT is as effective at inhibiting the growth of tumor cells as conventional-dose radiation. In addition, LDFRT could deregulate the expression of VEGF and p-m TOR, and may therefore play a vital role in reversing cisplatin resistance in ovarian cancer.