Inactivation of AR/TMPRSS2-ERG/Wnt signaling networks attenuates the aggressive behavior of prostate cancer cells

The development of prostate cancer and its progression to castrate-resistant prostate cancer (CRPC) after antiandrogen ablation therapy are driven by persistent biological activity of androgen receptor (AR) signaling. Moreover, studies have shown that more than 50% of human prostate cancers overexpress ERG (v-ets avian erythroblastosis virus E26 oncogene related gene) due to AR-regulated TMPRSS2-ERG fusion gene. However, the reported roles of TMPRSS2-ERG fusion in cancer progression are not clear. In this study, we investigated the signal transduction in the AR/TMPRSS2-ERG/Wnt signaling network for studying the aggressive behavior of prostate cancer cells and further assessed the effects of BR-DIM and CDF [natural agents-derived synthetic formulation and analogue of 3,3'-diindolylmethane (DIM) and curcumin, respectively, with improved bioavailability] on the regulation of AR/TMPRSS2-ERG/Wnt signaling. We found that activation of AR resulted in the induction of ERG expression through TMPRSS2-ERG fusion. Moreover, we found that ERG overexpression and nuclear translocation activated the activity of Wnt signaling. Furthermore, forced overexpression of ERG promoted invasive capacity of prostate cancer cells. More important, we found that BR-DIM and CDF inhibited the signal transduction in the AR/TMPRSS2-ERG/Wnt signaling network, leading to the inactivation of Wnt signaling consistent with inhibition of prostate cancer cell invasion. In addition, BR-DIM and CDF inhibited proliferation of prostate cancer cells and induced apoptotic cell death. On the basis of our findings, we conclude that because BR-DIM and CDF downregulate multiple signaling pathways including AR/TMPRSS2-ERG/Wnt signaling, these agents could be useful for designing novel strategies for the prevention and/or treatment of prostate cancer.     

跨膜丝氨酸蛋白酶2-Ets融合基因与前列腺癌的关系

在前列腺癌中存在跨膜丝氨酸蛋白酶2(TNPRSS2)与Ets相关基因(Ets related-gene, ERG)、Ets变异体基因(Ets variant,ETV)1、4、5基因形成的融合基因,以TMPRSS2-ERG的发生率最高.截止目前共检测到20多种TMPRSS2-ERG转录产物,编码9种蛋白质.缺失是融合的主要机制.融合基因有助于前列腺癌的诊断、指导临床用药,且融合亚型、拷贝数及转录亚型均与疾病的预后相关.因此,除了血清前列腺特异抗原(PSA)、Gleason评分外,TMPRSS2-ERG融合基因有望成为另一个预后因子.     

Characterization of TMPRSS2-ERG fusion high-grade prostatic intraepithelial neoplasia and potential clinical implications

PURPOSE: More than 1,300,000 prostate needle biopsies are done annually in the United States with up to 16% incidence of isolated high-grade prostatic intraepithelial neoplasia (HGPIN). HGPIN has low predictive value for identifying prostate cancer on subsequent needle biopsies in prostate-specific antigen-screened populations. In contemporary series, prostate cancer is detected in approximately 20% of repeat biopsies following a diagnosis of HGPIN. Further, discrete histologic subtypes of HGPIN with clinical implication in management have not been characterized. The TMPRSS2-ERG gene fusion that has recently been described in prostate cancer has also been shown to occur in a subset of HGPIN. This may have significant clinical implications given that TMPRSS2-ERG fusion prostate cancer is associated with a more aggressive clinical course. EXPERIMENTAL DESIGN: In this study, we assessed a series of HGPIN lesions and paired prostate cancer for the presence of TMPRSS2-ERG gene fusion. RESULTS: Fusion-positive HGPIN was observed in 16% of the 143 number of lesions, and in all instances, the matching cancer shared the same fusion pattern. Sixty percent of TMPRSS2-ERG fusion prostate cancer had fusion-negative HGPIN. CONCLUSIONS: Given the more aggressive nature of TMPRSS2-ERG prostate cancer, the findings of this study raise the possibility that gene fusion-positive HGPIN lesions are harbingers of more aggressive disease. To date, pathologic, molecular, and clinical variables do not help stratify which men with HGPIN are at increased risk for a cancer diagnosis. Our results suggest that the detection of isolated TMPRSS2-ERG fusion HGPIN would improve the positive predictive value of finding TMPRSS2-ERG fusion prostate cancer in subsequent biopsies.     

Duplication of the fusion of TMPRSS2 to ERG sequences identifies fatal human prostate cancer

New predictive markers for managing prostate cancer are urgently required because of the highly variable natural history of this disease. At the time of diagnosis, Gleason score provides the gold standard for assessing the aggressiveness of prostate cancer. However, the recent discovery of TMPRSS2 fusions to the ERG gene in prostate cancer raises the possibility of using alterations at the ERG locus as additional mechanism-based prognostic indicators. Fluorescence in situ hybridization (FISH) assays were used to assess ERG gene status in a cohort of 445 prostate cancers from patients who had been conservatively managed. The FISH assays detected separation of 5' (labelled green) and 3' (labelled red) ERG sequences, which is a consequence of the TMPRSS2-ERG fusion, and additionally identify interstitial deletion of genomic sequences between the tandemly located TMPRSS2 and ERG gene sequences on chromosome 21. Cancers lacking ERG alterations exhibited favourable cause-specific survival (90% survival at 8 years). We identify a novel category of prostate cancers, characterized by duplication of the fusion of TMPRSS2 to ERG sequences together with interstitial deletion of sequences 5' to ERG (called '2+Edel'), which by comparison exhibited extremely poor cause-specific survival (hazard ratio=6.10, 95% confidence ratio=3.33-11.15, P<0.001, 25% survival at 8 years). In multivariate analysis, '2+Edel' provided significant prognostic information (P=0.003) in addition to that provided by Gleason score and prostate-specific antigen level at diagnosis. Other individual categories of ERG alteration were associated with intermediate or good prognosis. We conclude that determination of ERG gene status, including duplication of the fusion of TMPRSS2 to ERG sequences in 2+Edel, allows stratification of prostate cancer into distinct survival categories.     

ERG oncogene modulates prostaglandin signaling in prostate cancer cells

Androgen dependent induction of the ETS related gene (ERG) expression in more than half of all prostate cancers results from gene fusions involving regulatory sequence of androgen regulated genes (i.e. TMPRSS2, SLC45A3 and NDRG1) and protein coding sequence of the ERG. Emerging studies in experimental models underscore the functions of ERG in prostate tumorigenesis. However, biological and biochemical functions of ERG in prostate cancer (CaP) remain to be elucidated. This study suggests that ERG activation plays a role in prostaglandin signaling because knockdown of ERG expression in TMPRSS2-ERG fusion containing CaP cells leads to altered levels of the 15-hydroxy-prostaglandin dehydrogenase (HPGD), a tumor suppressor and prostaglandin catabolizing enzyme, and prostaglandin E2 (PGE2) . We demonstrate that HPGD expression is regulated by the binding of the ERG protein to the core promoter of this gene. Moreover, prostaglandin E2 dependent cell growth and urokinase-type plasminogen activator (uPA) expression are also affected by ERG knockdown. Together, these data imply that the ERG oncoprotein in CaP cells positively influence prostaglandin mediated signaling, which may contribute to tumor progression.