Molecular targets in prostate cancer are continually being explored, for which there are currently few therapeutic options. Rapamycin (RPM) is an antifungal macrolide antibiotic isolated from Streptomyces hygroscopicus which can inhibit the G1 to S transition. URGCP (upregulator of cell proliferation) is a novel gene located on chromosome 7p13. We aimed to investigate the role of URGCP gene expression changes in PC3, DU145, and LNCAP cell lines with/out RPM. Average cell viability and cytotoxic effect of rapamycin were investigated at 24 h intervals for three days by using Trypan blue dye exclusion test and XTT assay. Cytotoxic effects of rapamycin in DU145, PC3 and LNCAP cells were detected in time and dose dependent manner with the IC50 doses within the range of 1-100 nM. As the results were evaluated, IC50 doses in the DU145, PC3, and LNCaP cells were detected as 10, 25, and 50 nM, respectively. The mean relative ratios of URGCP gene expression in DU145, LNCAP and PC3 cells were found as -1.48, 6.59 and -13.00, respectively, when compared to rapamycin-free cells. The False Discovery Rate adjusted p value in DU145, LNCAP and PC3 were 1.25 x 10(-5), 2.20 x 10(-8) and 6.20 x 10(-9), respectively. When the URGCP gene expression level is compared between the dose and control group, we found that URGCP gene expression was significantly decreased in dose groups of DU145 and PC3 cells.