ERG rearrangement in local recurrences compared to distant metastases of castration-resistant prostate cancer

ETS-related gene (ERG) expression as a predictor of oncological outcomes in patients with high-grade prostate cancer treated with primary androgen deprivation therapy: a cohort study

OBJECTIVES

To determine whether ETS-related gene (ERG) expression can be used as a biomarker to predict biochemical recurrence and prostate cancer-specific death in patients with high Gleason grade prostate cancer treated with androgen deprivation therapy (ADT) as monotherapy.

METHODS

A multicentre retrospective cohort study identifying 149 patients treated with primary ADT for metastatic or non-metastatic prostate cancer with Gleason score 8-10 between 1999 and 2006. Patients planned for adjuvant radiotherapy at diagnosis were excluded. Age at diagnosis, ethnicity, prostate-specific antigen and Charlson-comorbidity score were recorded. Prostatic tissue acquired at biopsy or transurethral resection surgery was assessed for immunohistochemical expression of ERG. Failure of ADT defined as prostate specific antigen nadir +2. Vital status and death certification data determined using the UK National Cancer Registry. Primary outcome measures were overall survival (OS) and prostate cancer specific survival (CSS). Secondary outcome was biochemical recurrence-free survival (BRFS).

RESULTS

The median OS of our cohort was 60.2 months (CI 52.0 to 68.3). ERG expression observed in 51/149 cases (34%). Multivariate Cox proportional hazards analysis showed no significant association between ERG expression and OS (p=0.41), CSS (p=0.92) and BRFS (p=0.31). Cox regression analysis showed Gleason score (p=0.003) and metastatic status (p<1×10^-5) to be the only significant predictors of prostate CSS.

CONCLUSIONS

No significant association was found between ERG status and any of our outcome measures. Despite a limited sample size, our results suggest that ERG does not appear to be a useful biomarker in predicting response to ADT in patients with high risk prostate cancer.

Nuclear receptor ERRα and transcription factor ERG form a reciprocal loop in the regulation of TMPRSS2:ERG fusion gene in prostate cancer

The TMPRSS2:ERG (T:E) fusion gene is generally believed to be mainly regulated by the activated androgen receptor (AR) signaling in androgen-dependent prostate cancer. However, its persistent expression in castration-resistant and neuroendocrine prostate cancers implies that other transcription factors might also regulate its expression. Here, we showed that up-regulation of nuclear receptor estrogen-related receptor alpha (ERRα) was closely associated with the oncogenic transcription factor ERG expression in prostate cancer, and their increased coexpression patterns were closely associated with high Gleason scores and metastasis in patients. Both ERRα and ERG exhibited a positive expression correlation in a castration-resistant prostate cancer (CRPC) xenograft model VCaP-CRPC. We showed that ERRα could directly transactivate T:E fusion gene in both AR-positive and -negative prostate cancer cells via both ERR-binding element- and AR-binding element-dependent manners. Ectopic T:E expression under ERRα regulation could promote both in vitro invasion and in vivo metastasis capacities of AR-negative prostatic cells. Intriguingly, ERG expressed by the T:E fusion could also transactivate the ERRα (ESRRA) gene. Hereby, ERRα and ERG can synergistically regulate each other and form a reciprocal regulatory loop to promote the advanced growth of prostate cancer. Inhibition of ERRα activity by ERRα inverse agonist could suppress T:E expression in prostate cancer cells, implicating that targeting ERRα could be a potential therapeutic strategy for treating the aggressive T:E-positive prostate cancer.

Pan-Cancer Analysis of the Mediator Complex Transcriptome Identifies CDK19 and CDK8 as Therapeutic Targets in Advanced Prostate Cancer

Purpose: The Mediator complex is a multiprotein assembly, which serves as a hub for diverse signaling pathways to regulate gene expression. Because gene expression is frequently altered in cancer, a systematic understanding of the Mediator complex in malignancies could foster the development of novel targeted therapeutic approaches.Experimental Design: We performed a systematic deconvolution of the Mediator subunit expression profiles across 23 cancer entities (n = 8,568) using data from The Cancer Genome Atlas (TCGA). Prostate cancer-specific findings were validated in two publicly available gene expression cohorts and a large cohort of primary and advanced prostate cancer (n = 622) stained by immunohistochemistry. The role of CDK19 and CDK8 was evaluated by siRNA-mediated gene knockdown and inhibitor treatment in prostate cancer cell lines with functional assays and gene expression analysis by RNAseq.Results: Cluster analysis of TCGA expression data segregated tumor entities, indicating tumor-type-specific Mediator complex compositions. Only prostate cancer was marked by high expression of CDK19 In primary prostate cancer, CDK19 was associated with increased aggressiveness and shorter disease-free survival. During cancer progression, highest levels of CDK19 and of its paralog CDK8 were present in metastases. In vitro, inhibition of CDK19 and CDK8 by knockdown or treatment with a selective CDK8/CDK19 inhibitor significantly decreased migration and invasion.Conclusions: Our analysis revealed distinct transcriptional expression profiles of the Mediator complex across cancer entities indicating differential modes of transcriptional regulation. Moreover, it identified CDK19 and CDK8 to be specifically overexpressed during prostate cancer progression, highlighting their potential as novel therapeutic targets in advanced prostate cancer. Clin Cancer Res; 23(7); 1829-40. ©2016 AACR.

Characterizing the molecular features of ERG-positive tumors in primary and castration resistant prostate cancer

BACKGROUND

The TMPRSS2-ERG gene fusion is detected in approximately half of primary prostate cancers (PCa) yet the prognostic significance remains unclear. We hypothesized that ERG promotes the expression of common genes in primary PCa and metastatic castration-resistant PCa (CRPC), with the objective of identifying ERG-associated pathways, which may promote the transition from primary PCa to CRPC.

METHODS

We constructed tissue microarrays (TMA) from 127 radical prostatectomy specimens, 20 LuCaP patient-derived xenografts (PDX), and 152 CRPC metastases obtained immediately at time of death. Nuclear ERG was assessed by immunohistochemistry (IHC). To characterize the molecular features of ERG-expressing PCa, a subset of IHC confirmed ERG+ or ERG- specimens including 11 radical prostatectomies, 20 LuCaP PDXs, and 45 CRPC metastases underwent gene expression analysis. Genes were ranked based on expression in primary PCa and CRPC. Common genes of interest were targeted for IHC analysis and expression compared with biochemical recurrence (BCR) status.

RESULTS

IHC revealed that 43% of primary PCa, 35% of the LuCaP PDXs, and 18% of the CRPC metastases were ERG+ (12 of 48 patients [25%] had at least one ERG+ metastasis). Based on gene expression data and previous literature, two proteins involved in calcium signaling (NCALD, CACNA1D), a protein involved in inflammation (HLA-DMB), CD3 positive immune cells, and a novel ERG-associated protein, DCLK1 were evaluated in primary PCa and CRPC metastases. In ERG+ primary PCa, a weak association was seen with NCALD and CACNA1D protein expression. HLA-DMB association with ERG was decreased and CD3 cell number association with ERG was changed from positive to negative in CRPC metastases compared to primary PCa. DCLK1 was upregulated at the protein level in unpaired ERG+ primary PCa and CRPC metastases (P = 0.0013 and P < 0.0001, respectively). In primary PCa, ERG status or expression of targeted proteins was not associated with BCR-free survival. However, for primary PCa, ERG+DCLK1+ patients exhibited shorter time to BCR (P = 0.06) compared with ERG+DCLK1- patients.

CONCLUSIONS

This study examined ERG expression in primary PCa and CRPC. We have identified altered levels of inflammatory mediators associated with ERG expression. We determined expression of DCLK1 correlates with ERG expression and may play a role in primary PCa progression to metastatic CPRC. Prostate 76:810-822, 2016. © 2016 Wiley Periodicals, Inc.

Prognostic histopathological and molecular markers on prostate cancer needle-biopsies: a review

Prostate cancer is diverse in clinical presentation, histopathological tumor growth patterns, and survival. Therefore, individual assessment of a tumor's aggressive potential is crucial for clinical decision-making in men with prostate cancer. To date a large number of prognostic markers for prostate cancer have been described, most of them based on radical prostatectomy specimens. However, in order to affect clinical decision-making, validation of respective markers in pretreatment diagnostic needle-biopsies is essential. Here, we discuss established and promising histopathological and molecular parameters in diagnostic needle-biopsies.

Somatic copy number alterations by whole-exome sequencing implicates YWHAZ and PTK2 in castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) is the most aggressive form of prostate cancer (PCa) and remains a significant therapeutic challenge. The key to the development of novel therapeutic targets for CRPC is to decipher the molecular alterations underlying this lethal disease. The aim of our study was to identify therapeutic targets for CRPC by assessing somatic copy number alterations (SCNAs) by whole-exome sequencing on five CRPC/normal paired formalin-fixed paraffin-embedded (FFPE) samples, using the SOLiD4 next-generation sequencing (NGS) platform. Data were validated using fluorescence in situ hybridization (FISH) on a PCa progression cohort. PTK2 and YWHAZ amplification, mRNA and protein expression were determined in selected PCa cell lines. Effects of PTK2 inhibition using TAE226 inhibitor and YWHAZ knock-down on cell proliferation and migration were tested in PC3 cells in vitro. In a larger validation cohort, the amplification frequency of YWHAZ was 3% in localized PCa and 48% in CRPC, whereas PTK2 was amplified in 1% of localized PCa and 35% in CRPC. YWHAZ knock-down and PTK2 inhibition significantly affected cell proliferation and migration in the PC3 cells. Our findings suggest that inhibition of YWHAZ and PTK2 could delay the progression of the disease in CRPC patients harbouring amplification of the latter genes. Furthermore, our validated whole-exome sequencing data show that FFPE tissue could be a promising alternative for SCNA screening using next-generation sequencing technologies.

Prognostic prostate tissue biomarkers of potential clinical use

In prostate biopsies and in prostatectomy specimens, the Gleason score remains the strongest prognosticator of prostate cancer progression, in addition to serum PSA level and DRE findings, in spite of numerous potential biomarkers discovered during the last few decades. Inter- and intratumoural heterogeneity may have limited the employment of tissue biomarkers on prostate biopsies. Nevertheless, the monoclonality of morphologically heterogeneous (Gleason score 7) tumour foci would suggest that genetic biomarkers, arising early in prostate carcinogenesis, may overcome issues related to intratumoural heterogeneity. In spite of the above limitations, a few biomarkers including the proliferation marker Ki-67 and genetic markers such as c-MYC and PTEN have consistently shown their independent prognostic impact both for biochemical recurrence and for clinical outcome parameters such as metastatic disease or prostate-specific mortality. The routine application of biomarkers requiring immunostaining (e.g. Ki-67) has particularly been hindered by the lack of standardized protocols for processing and scoring, while the application of fluorescence in situ hybridization (FISH) technology is considered more labour intensive but better standardized. Future steps to enhance the uptake of prostate tissue biomarkers should be focused on prospective studies, particularly on prostate biopsy specimens, using protocols that are highly standardized for the processing and scoring of the biomarkers. A few recently developed RNA-based test signatures may provide an alternative to FISH or immunohistochemistry-based tests.

ERG rearrangement and protein expression in the progression to castration-resistant prostate cancer

BACKGROUND

Approximately half of the prostate carcinomas are characterized by a chromosomal rearrangement fusing the androgen-regulated gene TMPRSS2 to the oncogenic ETS transcription factor ERG. Aim of this study was to comprehensively analyze the role and impact of the ERG rearrangement and protein expression on the progression to castration-resistant (CR) disease.

METHODS

We used a tissue microarray (TMA) constructed from 114 hormone naive (HN) and 117 CR PCs. We analyzed the ERG rearrangement status by fluorescence in situ hybridization and the expression profiles of ERG, androgen receptor (AR) and the proliferation marker Ki67 by immunohistochemistry.

RESULTS

Nearly half of the PC tissue specimens (HN: 38%, CR: 46%) harbored a TMPRSS2-ERG gene fusion. HN PCs with positive translocation status showed increased tumor cell proliferation (P<0.05). As expected, TMPRSS2-ERG gene fusion was strongly associated with increased ERG protein expression in HN and CR PCs (both P<0.0001). Remarkably, the study revealed a subgroup (26%) of CR PCs with ERG rearrangement but without any detectable ERG protein expression. This subgroup showed significantly lower levels of AR protein expression and androgen-regulated serum PSA (both P<0.05).

CONCLUSIONS

In this study, we identified a subgroup of ERG-rearranged CR PCs without detectable ERG protein expression. Our results suggest that this subgroup could represent CR PCs with a dispensed AR pathway. These tumors might represent a thus far unrecognized subset of patients with AR-independent CR PC who may not benefit from conventional therapy directed against the AR pathway.

ERG protein expression and gene rearrangements are present at lower rates in metastatic and locally advanced castration-resistant prostate cancer compared to localized disease

OBJECTIVE

To compare ERG expression and gene rearrangements rates in metastatic and castration-resistant prostate cancer (CRPC) to localized disease as ERG is the most common genetic event in early prostate cancer (PCa) with potential prognostic and therapeutic implications.

METHODS

We evaluated ERG protein expression in 344 patients with PCa in 3 cohorts including localized, metastatic, and castration-resistant disease using immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH).

RESULTS

ERG protein expression was detected exclusively in the neoplastic epithelium and was found in 6.8% and 46.3% of high-grade prostatic intraepithelial neoplasia (HGPIN) and localized PCa, respectively. In metastatic and locally advanced CRPC, ERG expression was significantly lower, occurring at 36.1% and 37.2%, respectively. In PCa with foamy gland morphology, ERG protein expression was detected in only 18.6% compared with reported rates of about 42%-48% in acinar PCa. Moreover, ERG protein expression and gene rearrangements showed an overall consistency rate of 90.6% (P <.0001). The consistency rate was 100% both in benign glands and HGPIN, and 96.1% in localized PCa. However, it was significantly lower at 76.9% and 85% in node metastatic and CRPC, respectively (P <.0001).

CONCLUSION

ERG protein expression is restricted to neoplastic prostatic epithelium and is present at lower rates in metastatic and CRPC compared to localized PCa. IHC and FISH concordance rates were significantly lower in node metastatic and CRPC compared to localized PCa, which may suggest different biological and therapeutic implications. The lower rate of ERG protein expression in foamy gland PCa may suggest potential differences for this pattern of PCa at the molecular level.