Objective:The cell death regulator Gene associated with Retinoid-IFN-induced Mortality 19 (GRIM-19) is an inhibitor of signal transducer and activator of transcription 3 (Stat3). We constructed an eukaryotic expression vector for human GRIM-19, and examined how enforced expression of GRIM-19 regulates apoptosis in PC-3M human prostate cancer cells both in vitro and in vivo.
 Methods:Immunohistochemistry staining to detect the expression of GRIM-19 in normal human prostate tissues and human prostate cancer tissues. A pGRIM-19 recombinant plasmid was constructed. PC-3M cells were transfected with the empty mock plasmid or pGRIM-19 by liposome. Western blot and RT-PCR analyses of GRIM-19 protein and mRNA expression in PC-3M cells were performed at 72 h after transfection. The inhibition effect of pGRIM-19 on PC-3M cells was detected by the MTT experiment. Cell cycle phase distribution was determined by flow cytometry. An Annexin V-CY3 apoptosis detection kit and the TUNEL assay were used for detecting apoptosis in vitro and in vivo. Western blot analyses of Stat3, VEGF,Bcl-2,c-myc,cyclin D1 protein expression were performed on PC-3M cells and tumor tissues.
 Results: The expression level of GRIM-19 was lower in prostate cancer specimens comparing to normal tissues, and the difference was statistically significant (P < 0.001). In addition, GRIM-19 was severely depressed in PC-3M cells. Enforced expression of GRIM-19 in PC-3M cells decreased the expression of Stat3, and its related genes, Bcl-2,c-myc,and cyclin D1. This was accompanied by growth suppression and induction of apoptosis in vitro and in tumors implanted in nude mice.Conclusions: This study demonstrated that enforced expression of GRIM-19 resulted in growth suppression and induction of apoptosis in human prostate cancer cells both in vitro and in vivo. The data thus indicated a tumor suppressor function of GRIM-19 in prostate. GRIM-19 could therefore serve as a potential target for the treatment of prostate cancer.

99th AACR Annual Meeting-- Apr 12-16, 2008; San Diego, CA