Inhibitory effect of all trans retinoic acid with vincristine on the proliferation of retinoblastoma cells

Drug resistance is the main cause of failure after chemotherapy of retinoblastoma(RB), and how to improve the sensitivity of RB cells to chemotherapic drug become an urgent issue.All trans retinoic acid (ATRA) can inhibit the growth of tumor cells.However, whether ATRA increases the sensitivity of RB cells to chemotherapic drug is unclear.

This study aimed to investigate the inhibitory effect of ATRA with vincristine on the proliferation of SO-RB50 cells.

SO-RB50 cells were cultured routinely.Different concentrations of ATRA or vincristine were added into the medium for 48 hours for the determination of IC₅₀ by cell counting kit-8(CCK-8) method.Cultured cells were divided into normal control group, ATRA group, vincristine group and combined drug group.The cells were treated by ATRA or vincristine with the dose of IC₅₀, and the proliferation of the cells was detected every day at the 24-hour interval for 6 consecutive days.The percentage of the cells in different cell cycles was analyzed 72 hours after treatment using flow cytometry.Cell apoptosis rate was detected and calculated 48 hours after treatment by annexin V/propidium iodide(PI) method.

The IC₅₀ of ATRA was approximately 12.84 μmol/L, and that of vincristine was 0.11 μg/ml.The growth curve of SO-RB50 cells was gradually raised as the lapse of time, but the curves were relatively low in the ATRA group, vincristine group and combined drug group, with the lowest curve in the combined drug group.The proliferation values of the cells (A₄₅₀) were 1.078±0.022, 0.611±0.038, 0.596±0.031 and 0.483±0.030 in 48 hours after treatment, and those in 72 hours were 1.380±0.021, 0.799±0.016, 0.668±0.041 and 0.532±0.033 in normal control group, ATRA group, vincristine group and combined drug group, showing significant differences among the groups and various time points (F_group=1 115.207, P=0.000; F_time =257.781, P=0.000). The A₄₅₀ values of the ATRA group, vincristine group and combined drug group were significantly lower than those of normal control group (all at P<0.05). The percentage of the cells in different cell cycles was changed after 72 hours’ treatment and the differences were statistically significant (F_G0/G1=130.565, F_S=57.435; F_G2/M=114.290, P<0.05). Compared with the normal control group, the percentage of G₀/G₁ phase cells was increased and S phase cells was decreased significantly in ATRA group, the percentage of G₀/G₁ phase cells was decreased and G₂/M phase cells was increased significantly in vincristine group(P<0.05). The apoptotic rate of the cells was (7.17±0.18) %, (27.34±1.36)%, (27.49±2.45)% and (34.50±1.84) % in normal control group, ATRA group, vincristine group and combined drug group, with a significant difference among the groups (F=147.555, P<0.05), and the apoptotic rate in the combined drug group was remarkedly lower than that of normal control group, ATRA group and vincristine group (all at P=0.000).

ATRA can improve the sensitivity of SO-RB50 cells to chemotherapeutic drug.The combined application of ATRA and vincristine enhance the inhibitory effect on the cells probably by regulating cell cycle and inducing apoptosis.