After having demonstrated in a previous study that RM1 prostate cancer cells express both leptin and insulin receptors [7], in the present study we show that high insulin concentrations (1600nmol / L) are able to trigger a significant increase in RM1 cell proliferation rate in the first 12h after incubation, when compared with lower concentrations (0 and 200 nmol/L) previously tested by us [40]. This evidence concerns the gene LEP and prostate carcinoma.