NOS1 expression promotes proliferation in OVCAR3 cells. L-NAME inhibited proliferation of OVCAR3 cells as determined by (A) MTT and (B) colony formation assays. *P<0.05 vs. control. The shRNA assay revealed that the levels of mRNA (C and D) protein expression of NOS1 were markedly decreased compared with the corresponding control in OVCAR3 cells. *P<0.05. NOS1 knockdown inhibited proliferation of OVCAR3 cells as determined by (E) MTT and (F) colony formation assays. Bars represent the mean ± standard deviation of three independent tests. *P<0.05. sh, short hairpin; CON, control; NOS, nitric oxide synthase; OD, optical density; L-NAME, NG-nitro-L-arginine methyl ester.