Livin-alpha promotes cell proliferation by regulating G1-S cell cycle transition in prostate cancer.

摘要

BACKGROUND: Prostate cancer is the third most common cancer and the second leading cause of cancer death for males in US. Livin has recently been described as a cancer-associated member of inhibitor of apoptosis proteins family, highly expressed in prostate cancer. Livin gene encodes two splicing variants, termed Livin-alpha and Livin-beta. We hypothesized that deregulation of proliferation could be due in part to Livin expression. METHODS: Pathological analysis of Livin was performed in 20 prostate cancer tissues and 5 benign prostatic hyperplasia tissues. The expression of Livin isoforms was also investigated by Western blot in prostate cancer cell lines LNCaP and PC3. The role of Livin-alpha in vitro was further studied. Using Livin-alpha knockdown and overexpression models, cell cycle analysis, Ki-67 immunocytostaining, and MTT assay were performed respectively. RESULTS: Livin expression positive ratio was shown to be 5.4%, 23.6%, 52.4%, 73.4% in benign prostatic hyperplasia, low, medium, and high grade of prostate cancer respectively, and Livin was positively correlated with clinical pathological grades of prostate cancer. Livin-alpha was expressed in both LNCaP and PC3; meanwhile; Livin-beta was only detected in the PC3. Livin-alpha siRNA not only resulted in G(1)-S cell cycle arrest, but also strongly correlated with the descended proliferation index and survival rate in LNCaP. In comparison, overexpression of Livin-alpha resulted in an accelerated S phase entry combined with elevated proliferation index and survival in LNCaP. CONCLUSIONS: Livin-alpha may promote cell proliferation by regulating G(1)-S cell cycle transition and possibly play an important part in initiation of prostate cancer.