The potential role of purine-rich element binding protein (PUR) α as a novel treatment target for hormone-refractory prostate cancer

BACKGROUND. Hormonal therapy for advanced prostate cancer is typically effective at first, but almost all men suffer refractory disease which often is life threatening. The nuclear matrix comprises not only of the structural elements of the nucleus, but is associated with many components of the molecular machinery. Our aim is to find novel targets for the treatment of hormone-refractory prostate cancer (HRPC) by focusing on the composition of the nuclear matrix proteins (NMPs). METHODS. LN96 cells were established at our Institution after long-term culturing of LNCaP cells under androgen deprived conditions. The composition of NMPs of LNCaP cells and LN96 cells were analyzed by two-dimensional (2D) electrophoresis and spots differentially expressed were investigated by mass spectrometry for identification. Among the spots identified, we analyzed the potential functional role of the identified proteins in prostate cancer cells by establishing stable overexpressed cells. RESULTS. We found that purine-rich element binding protein (PUR)alpha was significantly repressed not only in NMPs but also in total protein and mRNA levels of LN96 cells in comparison to LNCaP cells under the same steroid deprived conditions. Moreover, PUR alpha was decreased in its expression both at the protein and mRNA levels in the androgen-independent prostate cancer cell lines, PC3 and DU145 in comparison to LNCaP cells. Stably overexpressing PUR alpha in PC3 and DU145 cells negatively regulates cell proliferation, resulting in decreases in PCNA expression. CONCLUSION. Further dissection of the role of PUR alpha in cell growth regulation may reveal a novel target for HRPC.