The Role Of Prostate Cancer Fusion Gene TMPRSS2-ERG In Cisplatin-induced Cell Death

Prostate cancer (PCa) is the most common malignancy for men. Recently, gene fusion between TMPRSS2and several members of the ETS family had been discovered in PCa, in which the TMPRSS2-ERG fusion is the predominant type of Pca. Studies have shown that TMPRSS2-ERG gene fusion associated with tumor cell invasion and proliferation in PCa, but few studies have investigated its function on cell death.Objctive:To investigate whether TMPRSS2-ERG is involved in the regulation of cisplatin-induced cell death, and study the underlying mechanism.Methods:1. DU145cells were transiently transfected with A ERG that express the TMPRSS2-ERG fusion gene. After cisplatin exposure, cell death was detected by FACS after double staining with Annexin-V PE and7-AAD.2. TMPRSS2-ERG was inhibited by siRNA in VcaP cells. After cisplatin exposure, cell death was detected by FACS.3. The expression of yH2AX protein was detected by Western-blot to investigate the role of TMPRSS2-ERG fusion gene in DNA damage; the expression of apoptosis related gene was examined by quantitative PCR and the results were verified by Chromatin immunoprecipitation (ChIP). Results:1. Over-expression of TMPRSS2-ERG in DU145inhibited cisplatin-induced cell death, with death rate of14.67±2.69%and30.59±3.28%. for control cells.2. Knockdown TMPSS2-ERG by siRNA in prostate cancer cell line VcaP increased the apoptosis rate from13.59±2.82%to21.35±3.33%.3. Western-blot results showed that over-expression of ΔERG in293cells down-regulated the level of yH2AX protein by1.8fold, suggested that the fusion gene may protect cells from DNA damage.4. Expression levels of apoptosis related gene ATF-5was uprgulated by2.5-fold in ΔERG overexpressing cells as detected by q-PCR. Chromatin immunoprecipitation (ChIP) results showed that TMPRSS2-ERG can bind to ATF-5gene promoter region to enhance the expression of ATF-5.Conclusions:1. TMPRSS2-ERG fusion gene can inhbit cisplatin-induced cell death.2. TMPRSS2-ERG fusion gene may reduce cell death by inhibiting DNA damage. In addition, the fusion gene can bind to the promoter region of ATF-5to enhance the expression of ATF-5, an indirect inhibitor of apoptosis.