Deleted In Cancer 1 (DICE1): Search for a function in prostate carcinoma (PCa)

15634 Background: Recently, DICE1 gene (MIM 604331 ) was identified to colocalize with the microsatellite marker D13S284 in 13q14.3, a region frequently affected by allelic deletion in PCa. We previously showed that DICE1 mRNA expression is down-regulated in PCa cell lines compared to normal prostate tissue, due to DICE1 promoter hypermethylation; suggesting that DICE1 is a tumor suppressor gene. Methods: Human PCa cell lines PC3 and DU145 were lipo-transfected with mammalian expression plasmids encoding for the full length DICE1 gene or for its N- (APAI construct) and C-terminal (DEAD construct) fragments. The constructs expression was determined by semi-quantitative PCR and quantified by Real-time PCR. Clonogenic formation and apoptotic assays were performed. Results: The PCR analysis showed that the expression of DICE1, APAI and DEAD domains in transfected PC3 and DU145 cell lines was increased 30.6, 75.2 and 27.9 fold in PC3 cells and 4.3, 5 and 2.5 fold in DU145 cells, respectively, compared to non-transfected cells. The function analysis showed that the ectopic expression of DICE1 suppressed clonogenic growth of PC3 and DU145 cell lines. Surprisingly, we showed that like DICE1, DEAD and APAI inhibit the PC3 and DU145 clonogenic growth suggesting that both regions are involved in prostate tumor growth inhibition. The apoptosis assay could not show any DNA fragmentation activity for DICE1. Conclusions: We demonstrated that DICE1 is a tumor suppressor in PCa. DICE1 mRNA expression is down-regulated in PCa cell lines compared to normal prostate tissue and its ectopic expression in PCa cell lines inhibits their capacity to form clonogenic colonies in vitro. The functional analysis could not reveal any role of DICE1 in PCa apoptosis, suggesting that other molecular mechanisms are involved. No significant financial relationships to disclose.