Genome-wide linkage analysis of TMPRSS2-ERG fusion in familial prostate cancer

Acquired copy number variation in prostate tumours: a review of common somatic copy number alterations, how they are formed and their clinical utility

Prostate cancer is one of the most commonly diagnosed cancers in men and unfortunately, disease will progress in up to a third of patients despite primary treatment. Currently, there is a significant lack of prognostic tests that accurately predict disease course; however, the acquisition of somatic chromosomal variation in the form of DNA copy number variants may help understand disease progression. Notably, studies have found that a higher burden of somatic copy number alterations (SCNA) correlates with more aggressive disease, recurrence after surgery and metastasis. Here we will review the literature surrounding SCNA formation, including the roles of key tumour suppressors and oncogenes (PTEN, BRCA2, NKX3.1, ERG and AR), and their potential to inform diagnostic and prognostic clinical testing to improve predictive value. Ultimately, SCNAs, or inherited germline alterations that predispose to SCNAs, could have significant clinical utility in diagnostic and prognostic tests, in addition to guiding therapeutic selection.

Characterization of stage-specific tumor progression in TMPRSS2-ERG (fusion)-driven and non-fusion-driven prostate cancer in GEM models

In the present study, we performed a comparative stage-specific pathological and molecular marker evaluation of TMPRSS2-ERG fusion and PTEN loss-driven (TMPRSS2-ERG. Pten^flox/flox ) versus non-fusion-driven prostate tumorigenesis (Hi-Myc) in mice. Anterior, ventral, and dorsolateral prostates were collected from mice at different ages (or time points post-Cre induction). Results indicated that growth and progression of prostatic intraepithelial lesions to adenocarcinoma stages occurred in both mice models albeit at different rates. In the TMPRSS2-ERG. Pten^flox/flox mice, the initiation of tumorigenesis was slow, but subsequent progression through different stages became increasingly faster. Adenocarcinoma stage was reached early on; however, no high-grade undifferentiated tumors were observed. Conversely, in the Hi-Myc^+/- mice, tumorigenesis initiation was rapid; however, progression through different stages was relatively slower and it took a while to reach the more aggressive phenotype stage. Nevertheless, at the advanced stages in the Hi-Myc^+/- mice, high-grade undifferentiated tumors were observed compared to the later stage tumors observed in the fusion-driven TMPRSS2-ERG. Pten^flox/flox mice. These results were corroborated by the stage specific-pattern in the molecular expression of proliferation markers (PCNA and c-Myc); androgen receptor (AR); fusion-resultant overexpression of ERG; Prostein (SLC45-A3); and angiogenesis marker (CD-31). Importantly, there was a significant increase in immune cell infiltrations, which increased with the stage of tumorigenesis, in the TMPRSS2-ERG fusion-positive tumors relative to fusion negative tumors. Together, these findings are both novel and highly significant in establishing a working preclinical model for evaluating the efficacy of interventions during different stages of tumorigenesis in TMPRSS2-ERG fusion-driven PCa.

Analysis of a large prostate cancer family identifies novel and recurrent gene fusion events providing evidence for inherited predisposition

There is strong interest in the characterisation of gene fusions and their use to enhance clinical practices in prostate cancer (PrCa). Significantly, ~50% of prostate tumours harbour a gene fusion. Inherited factors are thought to predispose to these events but, to date, only one study has investigated gene fusions in a familial context. Here, we examined the prevalence and diversity of gene fusions in 14 tumours from a single large PrCa family, PcTas9, using the TruSight® RNA Fusion Panel and Sanger sequencing validation. These fusions were then explored in The Cancer Genome Atlas (TCGA) PrCa data set (n = 494). Overall, 64.3% of PcTas9 tumours harboured a gene fusion, including known erythroblast transformation-specific (ETS) fusions involving ERG and ETV1, and two novel gene fusions, C19orf48:ETV4 and RYBP:FOXP1. Although 3' ETS genes were overexpressed in PcTas9 and TCGA tumour samples, 3' fusion of FOXP1 did not appear to alter its expression. In addition, PcTas9 fusion carriers were more likely to have lower-grade disease than noncarriers (p = 0.02). Likewise, TCGA tumours with high-grade disease were less likely to harbour fusions (p = 0.03). Our study further implicates an inherited predisposition to PrCa gene fusion events, which are associated with less aggressive tumours. This knowledge could lead to clinical strategies to predict men at risk for fusion-positive PrCa and, thus, identify patients who are more or less at risk of aggressive disease and/or responsive to particular therapies.

Family history of prostate cancer and the incidence of ERG- and phosphatase and tensin homolog-defined prostate cancer

Family history is among the strongest known risk factors for prostate cancer (PCa). Emerging data suggest molecular subtypes of PCa, including two somatic genetic aberrations: fusions of androgen-regulated promoters with ERG and, separately, phosphatase and tensin homolog (PTEN) loss. We examined associations between family history and incidence of these subtypes in 44,126 men from the prospective Health Professionals Follow-up Study. ERG and PTEN status were assessed by immunohistochemistry. Multivariable competing risks models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for associations between self-reported family history of PCa and molecular subtypes of disease. Thirteen percent of men had a positive family history of PCa at baseline. During a median follow-up of 18.5 years, 5,511 PCa cases were diagnosed. Among them, 888 were assayed for ERG status (47% ERG-positive) and 715 were assayed for PTEN loss (14% PTEN null). Family history was more strongly associated with risk of ERG-negative (HR: 2.15; 95% CI: 1.71-2.70) than ERG-positive (HR: 1.49; 95% CI: 1.13-1.95) disease (p_{heterogeneity} : 0.04). The strongest difference was among men with an affected father (HR_ERG-negative : 2.09; 95% CI: 1.64-2.66; HR_ERG-positive : 1.30; 95% CI: 0.96-1.76; p_{heterogeneity} : 0.01). Family history of PCa was positively associated with both PTEN null (HR: 2.10; 95% CI: 1.26-3.49) and PTEN intact (HR: 1.72; 95% CI: 1.39-2.13) PCa (p_{heterogeneity} : 0.47). Our results indicate that PCa family history may be positively associated with PCa in all ERG and PTEN subtypes, suggesting a role of genetic susceptibility in their development. It is possible that ERG-negative disease could be especially associated with positive family history.

Association of germline genetic variants with TMPRSS2-ERG fusion status in prostate cancer

Introduction: Oncogenic activation of ERG resulting from TMPRSS2-ERG gene fusion is a key molecular genetic alteration in prostate cancer (CaP). The frequency of ERG fusion is variable by race; however, there are limited data available on germline polymorphisms associating with ERG fusion status. The goal of this study is to identify the inherited risk variants associating with ERG status of CaP.

Materials and Methods: SNP genotyping was performed on the Illumina platform using Infinium Oncoarray SNP chip on blood derived genomic DNA samples from 400 patients treated by radical prostatectomy at a single military institution. ERG status was determined in whole mounted prostate specimens by immuno-histochemistry (IHC) for ERG protein expression. Data analysis approaches included association analyses based on EMMAX and imputation by IMPUTE2. Imputed SNPs were validated by ddPCR.

Results: SNP genotyping analysis using imputation identified rs34349373 (p 4.68 × 10^-8) and rs2055272 (p 5.62 × 10^-8) in TBC1D22B to be significantly associated with ERG fusion status in index tumor and non-index tumor foci. Imputed SNP rs2055272 was further experimentally validated by ddPCR with 98.04% (100/102) concordance. Initial discovery analysis based on SNPs on Oncoarray SNP chip, showed significant (p 10^-5) association for SNPs (rs6698333, rs1889877, rs3798999, rs10215144, rs3818136, rs9380660 and rs1792695) with ERG fusion status. The study also replicated two previously known ERG fusion associated SNPs (rs11704416 in chromsome 22; rs16901979 in chromosome 8).

Conclusions: This study identified SNPs associated with ERG status of CaP.

Impact: The findings may contribute towards defining the underlying genetics of ERG positive and ERG negative CaP patients.

Disparities in prostate cancer incidence and mortality rates: Solvable or not?

Prostate cancer (PCa) is recognized as a disease possessing not only great variation in its geographic and racial distribution but also tremendous variation in its potential to cause morbidity and death and it, therefore, ought not to be considered a homogenous disease entity. Morbidity and death from PCa are disproportionately higher in men of African ancestry (MAA) who are generally observed to have more aggressive disease and worse outcomes following treatment compared to men of European ancestry (MEA). The higher rates of PCa among MAA relative to MEA appear to be multifactorial and related to inherent differences in biological aggressiveness; a continued lack of awareness of the disease and methods of prevention; a lower prevalence of screen-detected PCa; comparatively lower access to quality healthcare as well as systemic and institutionalized disparities in the administration of optimal care to MAA in developed countries such as the United States of America where high-quality care is available. Even when access to quality healthcare is assured in equal access settings, it appears that MAA still have worse outcomes after PCa treatment stage-for-stage and grade-for-grade compared to MEA, suggesting that, inherent racial, ethnic and biological differences are paramount in predicting poor outcomes. This review has explored the different contributing factors to the current disparities in PCa incidence and mortality rates with emphasis on the incongruence in how research has been conducted in understanding the disease towards developing therapies.

Predictive significance of TMRPSS2-ERG fusion in prostate cancer: a meta-analysis

Background

Prostate cancer is a major malignancy in males. TMPRSS2-ERG is a high-frequency fusion gene expressed in prostate cancer and plays a vital role in carcinogenesis. Recent studies showed that TMPRSS2-ERG is a potential predictive biomarker for prostate cancer. However, the predictive value of TMPRSS2-ERG fusion is yet unclear.

Methods

A total of 76 relevant articles, published from 2015 to 2017, were obtained from PubMed, Web of Science, EMBASE, Scopus, the Cochrane Library, and CNKI databases to investigate the predictive significance of TMPRSS2-ERG fusion in prostate cancer. Pooled odds ratio (ORs) with 95% confidence intervals (CIs) were calculated to estimate the correlation between TMPRSS2-ERG fusion gene and tumor features.

Results

The pooled or stratified analysis showed that the TMPRSS2-ERG fusion gene had a highly predictive potential. First, TMPRSS2-ERG fusion was associated with T-stage at diagnosis (T3–4 vs. T1–2 OR: 1.40; 95% CI 1.33–1.48) and metastasis (M1 vs. M0 OR: 1.35; 95% CI 1.02–1.78) but not with biochemical recurrence or prostate cancer-specific mortality. Furthermore, the subgroup analysis found that the TMPRSS2-ERG fusion gene was correlated with Gleason (G) scores, and the fusion was common in prostate cancer with G ≤ 7. Additionally, the meta-analysis demonstrated that the fusion was likely to occur in young patients (> 65 vs. ≤ 65 OR: 0.68; 95% CI 0.52–0.89), in patients with high PSA levels (> 10 vs. ≤ 10 OR: 1.30; 95% CI 1.21–1.38), and in patients with peripheral involvement (positive vs. negative OR: 1.17; 95% CI 1.08–1.28), while not associated with tumor volume. Finally, the subgroup analysis of different fusion types demonstrated that the deletion-type fusion was significantly associated with the malignant degree of prostate cancer (pooled OR: 5.67; 95% CI 2.85–11.28). Moreover, the deletion-type was common in Africa patients, followed by Caucasian patients, and no significant difference was observed in the incidence of different fusion types in the Asian population.

Conclusions

The meta-analysis findings suggested that the TMPRSS2-ERG fusion gene might be a predictive marker for prostate cancer patients, and might be valuable for assessing the characteristics of prostate cancer for individualized treatment and prognosis evaluation.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0672-2) contains supplementary material, which is available to authorized users.

Status of TMPRSS2-ERG fusion in prostate cancer patients from India: correlation with clinico-pathological details and TMPRSS2 Met160Val polymorphism

Background

Prostate cancer (PCa) shows considerable clinical heterogeneity that has been primarily attributed to variable molecular alterations. TMPRSS2-ERG fusion is one such molecular subtype that has been associated with predominantly poor prognosis. More recently, a single nucleotide polymorphism (SNP) in the TMPRSS2 gene rs12329760 C>T (Met160Val) has been shown to positively correlate with the fusion status and also to be associated with increased risk for PCa. The aim of the present study is to determine the frequency of TMPRSS2-ERG fusion and association of rs12329760 in Indian PCa patients with fusion status.

Methods

TMPRSS2-ERG fusion by fluorescence in situ hybridization was determined in 102 of 150 PCa biopsy-proven cases. Genotyping for rs12329760 was performed on the entire cohort of 150 cases by Sanger sequencing.

Results

TMPRSS2-ERG fusion was seen in 27 of 102 (26%) cases. Fusion-positive patterns in this study showed fusion by translocation in nine of 27 cases (33.5%), by deletion in six of 27 (22%) cases, and by insertion in 12 of 27 cases (44.5%). No association of the fusion status with Gleason Score, pattern, or perineural invasion was seen. The TMPRSS2 SNP rs12329760 'T' allele was prevalent with a frequency of 0.27 in the PCa patients. The SNP was significantly associated with fusion [odds ratio (OR) = 2.176, 95% confidence interval (CI) = 1.012-4.684, P = 0.04], more specifically fusion by deletion (P = 0.04).

Conclusion

The results provided here determine the frequency of TMPRSS2-ERG fusions (26%) in a fairly large cohort of Indian PCa cases and also the association of rs12329760 SNP with TMPRSS2-ERG fusion. No association with other clinico-pathological features was observed. Future studies with clinical outcomes are warranted in this population.

Clinical Utility and Biologic Implications of Phosphatase and Tensin Homolog (PTEN) and ETS-related Gene (ERG) in Prostate Cancer

Phosphatase and tensin homolog (PTEN) and ETS-related gene (ERG) mutations are commonly found in prostate cancer. Although mouse studies have demonstrated that PTEN and ERG cooperatively interact during tumorigenesis, human studies examining these genes have been inconclusive. A systematic PubMed search including original articles assessing the pathogenesis of PTEN and ERG in prostate cancer was performed. Studies examining ERG's prognostic significance have conflicting results. Studies examining PTEN and ERG simultaneously found these genes are likely to occur together, but cooperative tumorigenesis functions have not been conclusively established. PTEN mutations are associated with a range of prognostic features. However, the practical clinical utility of this information remains to be determined.

Inherited determinants of early recurrent somatic mutations in prostate cancer

Prostate cancer is a highly heritable molecularly and clinically heterogeneous disease. To discover germline events involved in prostate cancer predisposition, we develop a computational approach to nominate heritable facilitators of somatic genomic events in the context of the androgen receptor signaling. Here, we use a ranking score and benign prostate transcriptomes to identify a non-coding polymorphic regulatory element at 7p14.3 that associates with DNA repair and hormone-regulated transcript levels and with an early recurrent prostate cancer-specific somatic mutation in the Speckle-Type POZ protein (SPOP) gene. The locus shows allele-specific activity that is concomitantly modulated by androgen receptor and by CCAAT/enhancer-binding protein (C/EBP) beta (CEBPB). Deletion of this locus via CRISPR-Cas9 leads to deregulation of the genes predicted to interact with the 7p14.3 locus by Hi-C chromosome conformation capture data. This study suggests that a polymorphism at 7p14.3 may predispose to SPOP mutant prostate cancer subclass through a hormone-dependent DNA damage response.

Prostate cancer is a heterogeneous disease, and many cases show somatic mutations of SPOP. Here, the authors show that a non-coding polymorphic regulatory element at 7p14.3 may predispose to SPOP mutant prostate cancer subclass through a hormone dependent DNA damage response.

Prostate cancer risk regions at 8q24 and 17q24 are differentially associated with somatic TMPRSS2:ERG fusion status

Molecular and epidemiological differences have been described between TMPRSS2:ERG fusion-positive and fusion-negative prostate cancer (PrCa). Assuming two molecularly distinct subtypes, we have examined 27 common PrCa risk variants, previously identified in genome-wide association studies, for subtype specific associations in a total of 1221 TMPRSS2:ERG phenotyped PrCa cases. In meta-analyses of a discovery set of 552 cases with TMPRSS2:ERG data and 7650 unaffected men from five centers we have found support for the hypothesis that several common risk variants are associated with one particular subtype rather than with PrCa in general. Risk variants were analyzed in case-case comparisons (296 TMPRSS2:ERG fusion-positive versus 256 fusion-negative cases) and an independent set of 669 cases with TMPRSS2:ERG data was established to replicate the top five candidates. Significant differences (P < 0.00185) between the two subtypes were observed for rs16901979 (8q24) and rs1859962 (17q24), which were enriched in TMPRSS2:ERG fusion-negative (OR = 0.53, P = 0.0007) and TMPRSS2:ERG fusion-positive PrCa (OR = 1.30, P = 0.0016), respectively. Expression quantitative trait locus analysis was performed to investigate mechanistic links between risk variants, fusion status and target gene mRNA levels. For rs1859962 at 17q24, genotype dependent expression was observed for the candidate target gene SOX9 in TMPRSS2:ERG fusion-positive PrCa, which was not evident in TMPRSS2:ERG negative tumors. The present study established evidence for the first two common PrCa risk variants differentially associated with TMPRSS2:ERG fusion status. TMPRSS2:ERG phenotyping of larger studies is required to determine comprehensive sets of variants with subtype-specific roles in PrCa.

Association of Prostate Cancer Risk Variants with TMPRSS2:ERG Status: Evidence for Distinct Molecular Subtypes

BACKGROUND

Numerous genetic variants have been confirmed as prostate cancer risk factors. These variants may confer susceptibility to the development of specific molecular alterations during tumor initiation and progression. The TMPRSS2:ERG gene fusion occurs in roughly 50% of prostate cancers. Genetic risk variants may influence the development of this fusion. We sought to determine whether prostate cancer risk variants are differentially associated with TMPRSS2:ERG fusion-positive and negative cancer.

METHODS

In the Health Professionals Follow-up Study and Physicians' Health Study Tumor Cohort, we evaluated the associations of 39 prostate cancer risk SNPs with TMPRSS2:ERG fusion status, measured by ERG protein expression. Logistic regression was performed to generate OR and 95% confidence intervals. The primary outcome was ERG(+) (n = 227) versus ERG(-) (n = 260) prostate cancer. A secondary outcome was ERG(+) or ERG(-) cancer versus controls without cancer.

RESULTS

Six of 39 SNPs were significantly associated (P < 0.05) with ERG(+) versus ERG(-) disease. Three SNPs were exclusively associated with the risk of ERG(+), one with risk of ERG(-), and two with associations trending in opposite directions for ERG(+) and ERG(-) Only two significant SNPs would be expected by chance.

CONCLUSIONS

Prostate cancer genetic risk variants are differentially associated with the development of ERG(+) and ERG(-) prostate cancer.

IMPACT

Our findings suggest the molecular process of prostate carcinogenesis may be distinct for men with different underlying genetic predisposition. When examining risk factors for prostate cancer, the integration of molecular subtypes may enhance understanding of the etiology of this disease. Cancer Epidemiol Biomarkers Prev; 25(5); 745-9. ©2016 AACR.

ERG rearrangement as a novel marker for predicting the extra-prostatic extension of clinically localised prostate cancer

Currently, there are no well-established preoperative clinicopathological parameters for predicting extra-prostatic extension (EPE) in patients with clinically localised prostate cancer (PCa). The transmembrane protease serine 2 (TMPRSS2)-ETS-related gene (ERG) fusion gene is a specific biomarker of PCa and is considered a prognostic predictor. The aim of the present study was to assess the value of this marker for predicting EPE in patients with clinically localised PCa. In total, 306 PCa patients with clinically localised disease, including 220 patients (71.9%) with organ-confined disease and 86 EPE cases (28.1%), were included in the study. Receiver operating characteristic curves and logistic regression were employed to establish the optimal cut-off value and to investigate whether ERG rearrangement was an independent predictor for the EPE of clinically localised PCa. A leave-one-out cross-validation (LOOCV) model was implemented to validate the predictive power of ERG rearrangement. An increase in ERG rearrangements was identified to be associate'd with EPE, and the optimal cut-off for predicting EPE was determined to be 2.25%, with a sensitivity of 70.24% [95% confidence interval (CI), 62.6-78.9%], a specificity of 80.43% (95% CI, 75.4-85.1%), and an area under the curve (AUC) of 0.781 (95% CI, 0.730-0.826). In the LOOCV model, ERG rearrangement also demonstrated good performance for predicting EPE (sensitivity, 76.923%; specificity, 71.429%; 95% CI for AUC, 0.724-0.958). In addition, a high Gleason score (≥7) and a cT2c classification upon biopsy were independent factors for EPE.

ERG oncoprotein expression in prostate carcinoma patients of different ethnicities

Overexpression of the erythroblast transformation-specific-related gene (ERG) oncoprotein due to transmembrane protease, serine 2 (TMPRSS2)-ERG fusion, the most prevalent genomic alteration in prostate cancer (CaP), is more frequently observed among Caucasian patients compared to patients of African or Asian descent. To the best of our knowledge, this is the first study to investigate the prevalence of ERG alterations in a multiethnic cohort of CaP patients. A total of 191 formalin-fixed paraffin-embedded sections of transrectal ultrasound-guided prostate biopsy specimens, collected from 120 patients treated at the Sime Darby Medical Centre, Subang Jaya, Malaysia, were analyzed for ERG protein expression by immunohistochemistry using the anti-ERG monoclonal antibody 9FY as a surrogate for the detection of ERG fusion events. The overall frequency of ERG protein expression in the population evaluated in this study was 39.2%. Although seemingly similar to rates reported in other Asian communities, the expression of ERG was distinct amongst different ethnic groups (P=0.004). Malaysian Indian (MI) patients exhibited exceedingly high expression of ERG in their tumors, almost doubling that of Malaysian Chinese (MC) patients, whereas ERG expression was very low amongst Malay patients (12.5%). When collectively analyzing data, we observed a significant correlation between younger patients and higher ERG expression (P=0.04). The prevalence of ERG expression was significantly different amongst CaP patients of different ethnicities. The higher number of ERG-expressing tumors among MI patients suggested that the TMPRSS2-ERG fusion may be particularly important in the pathogenesis of CaP amongst this group of patients. Furthermore, the more frequent expression of ERG among the younger patients analyzed suggested an involvement of ERG in the early onset of CaP. The results of this study underline the value of using ERG status to better understand the differences in the etiology of CaP initiation and progression between ethnic groups.

The TMPRSS2:ERG rearrangement, ERG expression, and prostate cancer outcomes: a cohort study and meta-analysis

BACKGROUND

Whether the genomic rearrangement transmembrane protease, serine 2 (TMPRSS2):v-ets erythroblastosis virus E26 oncogene homolog (ERG) has prognostic value in prostate cancer is unclear.

METHODS

Among men with prostate cancer in the prospective Physicians' Health and Health Professionals Follow-Up Studies, we identified rearrangement status by immunohistochemical assessment of ERG protein expression. We used Cox models to examine associations of ERG overexpression with biochemical recurrence and lethal disease (distant metastases or cancer-specific mortality). In a meta-analysis including 47 additional studies, we used random-effects models to estimate associations between rearrangement status and outcomes.

RESULTS

The cohort consisted of 1,180 men treated with radical prostatectomy between 1983 and 2005. During a median follow-up of 12.6 years, 266 men experienced recurrence and 85 men developed lethal disease. We found no significant association between ERG overexpression and biochemical recurrence [hazard ratio (HR), 0.99; 95% confidence interval (CI), 0.78-1.26] or lethal disease (HR, 0.93; 95% CI, 0.61-1.43). The meta-analysis of prostatectomy series included 5,074 men followed for biochemical recurrence (1,623 events), and 2,049 men followed for lethal disease (131 events). TMPRSS2:ERG was associated with stage at diagnosis [risk ratio (RR)(≥T3 vs. T2), 1.23; 95% CI, 1.16-1.30) but not with biochemical recurrence (RR, 1.00; 95% CI, 0.86-1.17) or lethal disease (RR, 0.99; 95% CI, 0.47-2.09).

CONCLUSIONS

These results suggest that TMPRSS2:ERG, or ERG overexpression, is associated with tumor stage but does not strongly predict recurrence or mortality among men treated with radical prostatectomy.

IMPACT

This is the largest prospective cohort study to examine associations of ERG overexpression and lethal prostate cancer among men treated with radical prostatectomy.

TMPRSS2-ERG Fusion Gene Expression in Prostate Tumor Cells and Its Clinical and Biological Significance in Prostate Cancer Progression

TMPRSS2-Ets gene fusions were identified in prostate cancers where the promoter of transmembrane protease, serine 2 (TMPRSS2) fused with coding sequence of the erythroblastosis virus E26 (Ets) gene family members. TMPRSS2 is an androgen responsive transmembrane serine protease. Ets family members are oncogenic transcription factors that contain a highly conserved Ets DNA binding domain and an N-terminal regulatory domain.Fusion of these gene results in androgen dependent transcription of Ets factor in prostate tumor cells. The ERG is the most common fusion partner with TMPRSS2 promoter in prostate cancer patients. The high prevalence of these gene fusions, in particular TMPRSS2-ERG, makes them attractive as potential diagnostic and prognostic indicators, as well as making them a potential target for tailored therapies.This review focuses on the clinical and biological significance of TMPRSS2-ERG fusions and their role in PC development and progression.

[The progress of TMPRSS2-ETS gene fusions and their mechanism in prostate cancer]

The gene fusions between transmembrane protease serine 2 (TMPRSS2) and E26 (ETS) transcription factors are present in over 50% of patients with prostate cancer. TMPRSS2-ERG is the most common gene fusion type. The ERG overexpression induced by TMPRSS2-ERG gene fusion contributes to the development of prostate cancer. Both androgen receptor binding and genotoxic stress induce chromosomal proximity and TMPRSS2-ETS gene fusions. TMPRSS2-ERG gene fusion functions as a biomarker for prostate cancer, which can be easily detected in urine. This review focuses on the characteristics, oncogenic and rearranged mechanism, and clinical application of TMPRSS2-ETS gene fusions.

ETS family-associated gene fusions in Japanese prostate cancer: analysis of 194 radical prostatectomy samples

The incidence and clinical significance of the TMPRSS2:ERG gene fusion in prostate cancer has been investigated with contradictory results. It is now common knowledge that significant variability in gene alterations exists according to ethnic background in various kinds of cancer. In this study, we evaluated gene fusions involving the ETS gene family in Japanese prostate cancer. Total RNA from 194 formalin-fixed and paraffin-embedded prostate cancer samples obtained by radical prostatectomy was subjected to reverse-transcriptase polymerase chain reaction to detect the common TMPRSS2:ERG T1-E4 and T1-E5 fusion transcripts and five other non-TMPRSS2:ERG fusion transcripts. We identified 54 TMPRSS2:ERG-positive cases (54/194, 28%) and two HNRPA2B1:ETV1-positive cases (2/194, 1%). The SLC45A3-ELK4 transcript, a fusion transcript without structural gene rearrangement, was detectable in five cases (5/194, 3%). The frequencies of both TMPRSS2:ERG- and non-TMPRSS2:ERG-positive cases were lower than those reported for European, North American or Brazilian patients. Internodular heterogeneity of TMPRSS2:ERG was observed in 5 out of 11 multifocal cases (45%); a frequency similar to that found in European and North American cases. We found a positive correlation between the TMPRSS2:ERG fusion and a Gleason score of ≤7 and patient age, but found no relationship with pT stage or plasma prostate-specific antigen concentration. To exclude the possibility that Japanese prostate cancer displays novel TMPRSS2:ERG transcript variants or has unique 5' fusion partners for the ETS genes, we performed 5' RACE using fresh-frozen prostate cancer samples. We identified only the normal 5' cDNA ends for ERG, ETV1 and ETV5 in fusion-negative cases. Because we identified a relatively low frequency of TMPRSS2:ERG and other fusions, further evaluation is required before this promising molecular marker should be introduced into the management of Japanese prostate cancer patients.

Markers for detection of prostate cancer

Early detection of prostate cancer is problematic, not just because of uncertainly whether a diagnosis will benefit an individual patient, but also as a result of the imprecise and invasive nature of establishing a diagnosis by biopsy. Despite its low sensitivity and specificity for identifying patients harbouring prostate cancer, serum prostate specific antigen (PSA) has become established as the most reliable and widely-used diagnostic marker for this condition. In its wake, many other markers have been described and evaluated. This review focuses on the supporting evidence for the most prominent of these for detection and also for predicting outcome in prostate cancer.

ETS gene fusions in prostate cancer

Chromosomal rearrangements that result in high level expression of ETS gene family members are common events in human prostate cancer. Most frequently, the androgen-activated gene TMPRSS2 is found fused to the ERG gene. Fusions involving ETV1, ETV4 and ETV5 occur less frequently but exhibit greater variability in fusion structure with 12 unique 5' fusion partners identified so far. ETS gene rearrangement seems to be a key event in driving prostate neoplastic development: the rearrangement occurs as an early event and continues to be expressed in metastatic and castration-resistant disease. However, ETS alterations seem insufficient on their own to induce cancer formation. No consistent associations are seen between the presence of ETS alteration and clinical outcome, with the possible exception that duplication of rearranged ERG, reflecting aneuploidy, is associated with poor outcome. Thus, factors other than ERG gene status may be the major determinants of poor clinical outcome. Expression signatures of prostate cancers containing the TMPRSS2-ERG fusion suggest involvement of beta-estradiol signaling, and reveal higher levels of expression of HDAC1 and ion channel genes when compared to cancers that lack the rearrangement. These observations suggest new therapeutic possibilities for patients harboring ETS gene fusions.

Prostate cancer genes associated with TMPRSS2-ERG gene fusion and prognostic of biochemical recurrence in multiple cohorts

Background:

Recent studies have indicated that prostate cancer patients with the TMPRSS2–ERG gene fusion have a higher risk of recurrence. To identify markers associated with TMPRSS2–ERG fusion and prognostic of biochemical recurrence, we analysed a cohort of 139 men with prostate cancer for 502 molecular markers.

Methods:

RNA from radical prostatectomy tumour specimens was analysed using cDNA-mediated, annealing, selection, extension and ligation (DASL) to determine mRNAs associated with TMPRSS2–ERG T1/E4 fusion and prognostic of biochemical recurrence. Differentially expressed mRNAs in T1/E4-positive tumours were determined using significance analysis of microarrays (false discovery rate (FDR) <5%). Univariate and multivariate Cox regression determined genes, gene signatures and clinical factors prognostic of recurrence (P-value <0.05, log–rank test). Analysis of two prostate microarray studies (GSE1065 and GSE8402) validated the findings.

Results:

In the 139 patients from this study and from a 455-patient Swedish cohort, 15 genes in common were differentially regulated in T1/E4 fusion-positive tumours (FDR <0.05). The most significant mRNAs in both cohorts coded ERG. Nine genes were found prognostic of recurrence in this study and in a 596-patient Minnesota cohort. A molecular recurrence score was significant in prognosticating recurrence (P-value 0.000167) and remained significant in multivariate analysis of a mixed clinical model considering Gleason score and TMPRSS2–ERG fusion status.

Conclusions:

TMPRSS2–ERG T1/E4 fusion-positive tumours had differentially regulated mRNAs observed in multiple studies, the most significant one coded for ERG. Several mRNAs were consistently associated with biochemical recurrence and have potential clinical utility but will require further validation for successful translation.

Predisposition for TMPRSS2-ERG fusion in prostate cancer by variants in DNA repair genes

The somatic fusion of TMPRSS2 to ETS oncogenes is a common event in prostate cancer (PCa). We hypothesized that defects in DNA repair may lead to an increase of chromosomal rearrangements and thus to the occurrence of ETS oncogene fusion. We have previously conducted a genome-wide linkage analysis in TMPRSS2-ERG fusion-positive PCa families, revealing potential susceptibility loci on chromosomes 5q14, 9q21, 10q26, 11q24, 12q15, 13q12, 18q, and Xq27. In the present study, nine candidate genes from these regions were selected from the context of DNA repair and screened for mutations in TMPRSS2-ERG fusion-positive families. Thirteen nonsynonymous variants, 5 of which had a minor allele frequency of <0.05, were genotyped in 210 familial cases, 47 of which with a known TMPRSS2-ERG status, 329 sporadic cases, and 512 controls. Significant association of TMPRSS2-ERG fusion-positive PCa was found with rare variants in the genes for POLI [variant F532S: P = 0.0011; odds ratios (OR), 4.62; 95% confidence interval (95% CI), 1.84-11.56] and ESCO1 (variant N191S: P = 0.0034; OR, 4.27; 95% CI, 1.62-11.28). Additional findings, regardless of TMPRSS2-ERG status, were the overrepresentation of a rare BRCA2 variant (V2728I: P = 0.03; OR, 6.16; 95% CI, 1.19-32.00) in familial PCa and of a common allele of RMI1 (variant N455S: P = 0.02; OR, 1.33; 95% CI, 1.04-1.70) in unselected PCa cases. The DNA repair genes POLI and ESCO1 are proposed as susceptibility genes for TMPRSS2-ERG fusion-positive PCa that warrant further investigation.

ETS gene fusions in prostate cancer: from discovery to daily clinical practice

CONTEXT

In 2005, fusions between the androgen-regulated transmembrane protease serine 2 gene, TMPRSS2, and E twenty-six (ETS) transcription factors were discovered in prostate cancer.

OBJECTIVE

To review advances in our understanding of ETS gene fusions, focusing on challenges affecting translation to clinical application.

EVIDENCE ACQUISITION

The PubMed database was searched for reports on ETS fusions in prostate cancer.

EVIDENCE SYNTHESIS

Since the discovery of ETS fusions, novel 5' and 3' fusion partners and multiple splice isoforms have been reported. The most common fusion, TMPRSS2:ERG, is present in approximately 50% of prostate-specific antigen (PSA)-screened localized prostate cancers and in 15-35% of population-based cohorts. ETS fusions can be detected noninvasively in the urine of men with prostate cancer, with a specificity rate in PSA-screened cohorts of >90%. Reports from untreated population-based cohorts suggest an association between ETS fusions and cancer-specific death and metastatic spread. In retrospective prostatectomy cohorts, conflicting results have been published regarding associations between ETS fusions and cancer aggressiveness. In addition to serving as a potential biomarker, tissue and functional studies suggest a specific role for ETS fusions in the transition to carcinoma. Finally, recent results suggest that the 5' and 3' ends of ETS fusions as well as downstream targets may be targeted therapeutically.

CONCLUSIONS

Recent studies suggest that the first clinical applications of ETS fusions are likely to be in noninvasive detection of prostate cancer and in aiding with difficult diagnostic cases. Additional studies are needed to clarify the association between gene fusions and cancer aggressiveness, particularly those studies that take into account the multifocal and heterogeneous nature of localized prostate cancer. Multiple promising strategies have been identified to potentially target ETS fusions. Together, these results suggest that ETS fusions will affect multiple aspects of prostate cancer diagnosis and management.