Objective:To explore the mechanism of all-transretinoic acid(ATRA) increasing retinoblastoma(RB) sensitivity to vincristine,and the inhibiting effect of vincristine combined with ATRA treatment on the SO-RB50 cell proliferation.Methods:SO-RB50 cells were cultivated by routine culture method.Different concentrations of vincristine or ATRA were added into culture solution.After 48 h.cell counting kit-8 was used to detect the median inhibitory concentration(IC_(50)) of vincristine combined with ATRT treatment to SO-RB50 cells.SO-RB50 cells were divided into drug combination group,vincristine group,ATRA group and control group.Different drugs were added into the culture solution respectively for cell culture based on the IC_(50) value.Cell counting kit-8 was used to detect the cell proliferation every 24-h cultivation.After continuous determination for 6 d,data was processed to draw the cell growth curve.After drug use for 72 h,flow cytometry was used to detect the proportion of different cell cycles of SO-RB50 cells in each group.After drug use for 48 h,annexin V/propidium iodide method was used to detect the SO-RB50 cell apoptosis in each group.Results:The IC_(50) value of vincristine treatment on the SO-RB50 cells was 0.11 μmol/L,and ATRT was 12.84 μmol/L.The cell growth curve in control group rose gradually along with the extended culture time,but after vincristine and ATRA treatment,the cell growth curve was smooth and steady.The cell increment was the least in drug combination group and its cell growth curve was the smoothest.There was significant difference in A_(450) 48 h and 72 h after treatment(F_(grouping)=77.316,P<0.001;F_(time)=86.985,P<0.001).Compared with control group.A_(450) value in drug combination group,vincristine group,ATRA group was significantly lower(P<0.001).Compared with control group,the G_2/M phase cell proportion in vincristine group was significantly increased,while the G_0/G_1 phase cell proportion was significantly decreased:the G_0/G_1 phase cell proportion in ATRA group was significantly increased,while the S phase cell proportion was significantly decreased(F_(G0/G1)=85.878,F_s=56.455,F_(G2/M)=85.878,P<0.001).After 48 h,there was significant difference in SO-RB50 cell apoptosis rate among groups(F=11.312.P<0.05).The apoptosis rate in drug combination group was significantly higher than that of other groups(P<0.001).Condusion:ATRA can increase the sensitivity of SO-RB50 cells to vincristine.Vincristine combined with ATRA treatment can significantly increase the inhibiting effect on SO-RB50 cells,which may be related with promoting cell apoptosis and involving in cell cycle control. Objective: To explore the mechanism of all-transretinoic acid (ATRA) increasing retinoblastoma (RB) sensitivity to vincristine, and the inhibiting effect of vincristine combined with ATRA treatment on the SO-RB50 cell proliferation. Methods: SO-RB50 cells were cultivated by routine culture method. Different concentrations of vincristine or ATRA were added into culture solution. After 48 h. cell counting kit-8 was used to detect the median inhibitory concentration (IC_ (50)) of vincristine combined with ATRT treatment to SO-RB50 cells .SO-RB50 cells were divided into drug combination group, vincristine group, ATRA group and control group. Different drugs were added into the culture solution respectively for cell culture based on the IC_ (50) value. Cell counting kit-8 was used to detect the cell proliferation every 24-h cultivation. After continuous determination for 6 d, data was processed to draw the cell growth curve. After drug use for 72 h, flow cytometry was used to detect the proportion of different Cell cycles of SO-RB50 cells in each group. After drug use for 48 h, annexin V / propidium iodide method was used to detect the SO-RB50 cell apoptosis in each group. Results: The IC 50 value of vincristine treatment on the SO-RB50 cells was 0.11 μmol / L, and ATRT was 12.84 μmol / L. The cell growth curve in control group rose gradually with the extended culture time, but after vincristine and ATRA treatment, the cell growth curve was smooth and steady The cell increment was the least in drug combination group and its cell growth curve was the smoothest.There was significant difference in A_ (450) 48 h and 72 h after treatment (F_ (grouping) = 77.316, P <0.001; F_ (450) value in drug combination group, vincristine group, ATRA group was significantly lower (P <0.001) .Compared with control group, the G2 / M phase cell proportion in vincristine group was significantly increased, while the G_0 / G_1 phase cell proportion was significantly decreased: the G_0 / G_ 1phase cell proportion in ATRA group was significantly increased while the S phase cell proportion was significantly decreased (F_ (G0 / G1) = 85.878, F_s = 56.455, F_ (G2 / M) = 85.878, P <0.001) , there was significant difference in SO-RB50 cell apoptosis rate among groups (F = 11.312.P <0.05). The apoptosis rate in drug combination group was significantly higher than that of other groups (P <0.001) the sensitivity of SO-RB50 cells to vincristine. Vincristine combined with ATRA treatment can significantly increase the inhibiting effect on SO-RB50 cells, which may be related with promoting cell apoptosis and involving in cell cycle control.