Abstract： Objective To study the effect and mechanism of S1PR2 inhibition on epithelial ovarian cancer SKOV3 cell proliferation in vitro and in vivo. Methods(1)A pair of S1PR2 gene small interference RNA(siRNA),namely si-S1PR2,and a pair of negative control siRNA were designed.Western blot methods were used to detect the silence efficiency of the S1PR2 in the si-S1PR2 group,blank control group and negative control group.(2)Study in vitro: the experiment included three groups, namely si-S1PR2 group, blank control group and negative control group. Cell counting kit-8(CCK-8)assay was used to detect the proliferation inhibition rates of the transfected cells. The cell cycles of the transfected cells were measured by flow cytometry. Western blot was used to detect the levels of phosph-extracellular regulated protein kinase 1/2(p-ERK1/2)of the transfected cells.(3)Study in vivo:to establish intraperitoneal transplantation models, 8 mice in each group were intraperitoneally injected with 5×106SKOV3 cells. Phosphate buffered saline(PBS)or JTE-013 were administered into mice twice per week starting on day 7 after the injection of the cancer cells. Twenty-eight days after nude mice intraperitoneal injection with JTE-013 or PBS,the mice were sacrificed and the number and the weight of visible tumors were calculated. Results(1)The results of western blot showed that the relative S1PR2 protein expression levels were 0.24±0.04 in the si-S1PR2 group,which was lower than that in the blank control group(1.10±0.14,P<0.01) and negative control group(1.07 ± 0.13, P<0.01).(2)The results of CCK-8 assay indicated that after transfected for 24, 48 and 72 hours, the proliferation inhibition rate of si-S1PR2 group were respectively (26.6±3.3)%,(35.0±3.4)%,and(34.0±2.8)%,significantly lower than those in the blank control group (all 0;all P<0.01)and negative control group[(1.7±0.9)%,(2.5±0.5)%,and(2.4±1.1)% respectively;all P<0.01].The results of flow cytometry showed that the G0/G1ratio in the si-S1PR2 group[(70.9±2.8)%]was significantly higher than those in the blank control group[(61.7±2.4)%,P<0.01]and negative control group [(62.1 ± 3.3)%, P<0.01]. Western blot showed that the relative expression level of p-ERK1/2 in si-S1PR2 group(0.11±0.03)was significantly lower than those in the blank control group[(0.62±0.09),P<0.01]and negative control group[(0.68±0.09),P<0.01].(3)Twenty-eight days after nude mice intraperitoneal injection with JTE-013 or PBS,the tumor number of the control group and JTE-013 group were respectively 15.4±4.3 and 8.2±3.7,the tumor weight were(0.45±0.12)and(0.21±0.07)g,respectively.The tumor number and weight in the JTE-013 group were significantly less than those in the control group(all P<0.01). Conclusions The growth of ovarian cancer cells could be decreased by S1PR2 inhibition in vitro and in vivo. One of the mechanisms of the growth inhibitory effect is probably that S1PR2 inhibition lower the phosphorylation level of extracellular regulated protein kinase 1/2(ERK1/2)pathway, which prevent the transformation of ovarian cancer cells from phase G1to S.