Deleted in cancer 1: Search for a function in prostate cancer
e16095 Background: Deleted In Cancer 1 (DICE1/INTS6) gene was recently identified to colocalize with the microsatellite marker D13S284 in 13q14.3, a region frequently affected by allelic deletion in many solid tumors including prostate cancer (PrCa). DICE1 missense mutations have been previously detected in PrCa cell line LNCap, and reduced DICE1 expression appears to be associated with CpG promoter hypermethylation in PrCa cells. DICE1 is a highly conserved nuclear protein suggesting its involvement in DNA repair, transcription, or RNA splicing. In mouse, the DICE1 homologue interferes with the response to insulin-like growth factor 1 and suppresses anchorage-independent growth of transformed mouse cells. The totality of these results suggests that DICE1 is a tumor suppressor gene and insist on the need to better characterize DICE1 function in PrCa. Methods: Expression of DICE1 was evaluated by Northern Blot in PrCa cell lines LNCap, DU145, PC3, PC3ml and CPTX1532 and compared to expression level in normal prostate cell line NPTX1532. DICE1 growth inhibitory effects were analyzed by colony formation assay on PC3 and DU145 cells transfected with DICE1 expression plasmid or control vector. Apoptosis was assessed by visualization of genomic DNA fragmentation on agarose gel. PCR arrays (SABiosciences) were used to identify specific signaling pathways modulated in response to DICE1 expression. Results: Markedly decreased DICE1 mRNA levels were detected in PrCa cell lines LNCap, DU145, PC3 and PC3ml as well as CPTX1532 as compared to NPTX1532, a cell line derived from normal prostate tissue. Ectopic expression of DICE1 cDNA in DU145 and PC3 cells substantially suppressed their ability to form colonies in vitro. This growth inhibition was not due to immediate induction of apoptosis suggesting growth suppression by other pathways. Expression profiling identified multiple pathways, such as Wnt, Hedgehog, PI-3 Kinase, NFκB and Insulin pathways, regulated in response to ectopic DICE1 expression. Furthermore, various transcription factors including Fos, Jun, CEBPA and PPAR-γ were up-regulated in response to DICE1. Conclusions: These results clearly illustrate the growth inhibitory ability of DICE1 in PrCa. Expression profiling links DICE1 function to growth factor signaling and cell-cell communication. No significant financial relationships to disclose.