This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.The development of novel therapeutic options is an urgent issue for prostate cancer treatment. We recently demonstrated that GSK-3beta suppression eliminates TRAIL resistance in prostate cancer cells, indicating GSK-3beta is a negative regulator of TRAIL-mediated apoptosis in prostate cancer. Moreover, we found that GSK-3beta suppression resulted in a dramatic increase of protein tyrosine phosphatase SHP-2 expression via a transcriptional mechanism. To determine if increased SHP-2 expression is responsible for TRAIL sensitization in prostate-derived epithelial cells, we established several SHP-2 over-expressing prostate cancer cell lines and then evaluated their responsiveness to TRAIL-mediated cell death. Cellular survival was assessed with a MTT-based assay. As expected, parental non-malignant RWPE-1 cells showed a significant higher resistance to TRAIL compared to other two malignant cell lines CWR22Rv1 and LAPC-4. However, a similar enhancing effect was found in all three SHP-2 over-expressing stable lines to TRAIL-induced cell death. Next, we determined if over-expressing SHP-2 enhances the formation of TRAIL-mediated death-inducing signaling complex (DISC) in prostate cancer LAPC-4 cells. DISC precipitation was performed using biotin-tagged recombinant TRAIL (Bio-TRAIL). We found that over-expressing SHP-2 significantly enhanced TRAIL-stimulated recruitment of FADD and caspase-8 to TRAIL receptor DR4. Caspase-8 cleavage (due to activation) was also increased. These results suggest that SHP-2 plays a positive role in enhancing TRAIL-mediated DISC assembly and subsequent apoptotic cell death. Next year, we will determine the effect of knocking down of SHP-2 on TRAIL-mediated apoptosis in prostate cancer cells.
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