2078

ERG

v-ets avian erythroblastosis virus E26 oncogene homolog;ERG;v-ets avian erythroblastosis virus E26 oncogene homolog

TMPRSS2/ERG fusion|ets-related|transcriptional regulator ERG|transcriptional regulator ERG (transforming protein ERG)|v-ets avian erythroblastosis virus E26 oncogene related|v-ets erythroblastosis virus E26 oncogene homolog|v-ets erythroblastosis virus E2

21q22.3

protein-coding

BACKGROUND: Fusion of the androgen-regulated gene transmembrane protease, serine 2, TMPRSS2, to the v-ets erythroblastosis virus E26 oncogene homolog (avian), ERG, of the erythroblast transformation-specific (ETS) family is the most common genetic alteration in prostate cancer (PCa). OBJECTIVE: To determine whether expression of androgen-regulated TMPRSS2-ERG predicts response to endocrine treatment in hormone-naive, node-positive PCa. DESIGN, SETTING, AND PARTICIPANTS: Eighty-five patients with histologically confirmed, node-positive PCa who were without treatment at the moment of lymph node dissection were analysed. RNA was isolated from the paraffin-embedded lymph node metastases and complementary DNA (cDNA) was made. The quality of cDNA was tested by polymerase chain reaction (PCR) analysis of the expression of the housekeeping gene hydroxymethylbilane synthase, HMBS (formerly PBGD). TMPRSS2-ERG expression was analysed by PCR using a forward primer in TMPRSS2 exon 1 and a reverse primer in ERG exon 4. MEASUREMENTS: The primary end point was time from start of endocrine therapy to the occurrence of three consecutive rises in prostate-specific antigen (PSA) that were at least 2 wk apart and resulted in two 50% increases over the PSA nadir. Secondary end points were time to PSA nadir after start of endocrine treatment and cancer-specific and overall survival. RESULTS AND LIMITATIONS: TMPRSS2-ERG was expressed in 59% of the 71 patients who could be analysed. Median duration of response to endocrine therapy was 20.9 mo versus 24.1 mo for gene fusion-positive versus gene fusion-negative patients (95% confidence intervals: 18.6-23.1 vs 18.9-29.4, p=0.70). Furthermore, no significant differences were seen between the two groups for the secondary end points. CONCLUSIONS: expression of TMPRSS2-ERG is frequent in lymph node metastases of patients with untreated PCa; however, expression of this androgen-regulated fusion gene did not correspond with duration of response to endocrine therapy. Our results suggest that expression of TMPRSS2-ERG is not a candidate marker to select for metastatic PCa patients who will benefit more from endocrine treatment.

OBJECTIVES: To interrogate multifocal prostate cancer (PCa) to determine its predilection for metastasis, using ERG rearrangement as marker of clonality. A hallmark of PCa is that distinct tumor foci may arise independently, which has important biological and clinical implications. Recent studies characterizing ERG-rearranged PCa possessing intrafocal homogeneity but interfocal heterogeneity support this hypothesis. METHODS: We studied 26 patients who underwent prostatectomy and lymphadenectomy with at least 2 distinct PCa foci and 1 lymph node (LN) metastasis. Each focus was assessed for size, Gleason score, ERG rearrangement, and TMPRSS2-ERG transcript. RESULTS: Fifteen of 26 cases exhibited interfocal homogeneity with regard to ERG rearrangement (ie, presence vs absence of ERG rearrangement). ERG rearrangement was present in all foci for 6 and absent in all foci for 9 cases. Two cases revealed interfocal heterogeneity with regard to rearrangement mechanism (ie, rearrangement through insertion or deletion). Eight of 26 cases revealed interfocal heterogeneity with regard to rearrangement status. In all cases with at least 1 ERG rearranged focus, we found the corresponding LN metastasis harboring an ERG rearrangement. Interestingly, in a subset of cases the rearrangement status in the LN did not correspond to size or Gleason score. All but 2 ERG rearranged foci had detectable TMPRSS2-ERG transcript levels. CONCLUSIONS: When multifocal PCa demonstrates both ERG-positive and ERG-negative foci, the positive foci have a greater predilection for metastasis. Larger studies are needed to confirm the potential additional risk an ERG rearranged focus confers on the likelihood of disease progression.

Recent studies have revealed the presence of TMPRSS2-ERG gene fusion in both primary and metastatic prostate cancers. However, the relationship between primary and corresponding metastatic prostate cancers with respect to the status of this gene fusion remains unclear. Using fluorescence in situ hybridization, we evaluated the rearrangement of the ERG gene in the radical prostatectomy specimens and corresponding lymph node metastases from 19 patients with prostate cancer. The mean age of the patients was 61 years, and the median Gleason score in the radical prostatectomy specimens was 7 (4 + 3). Prostate cancer was unifocal in 6 cases and multifocal in 13 cases, including 10 with 2 foci and 3 with 3 foci. In the primary prostate cancers, rearrangement of the ERG gene was observed in 13 cases and associated with deletion of the 5' ERG gene in 8 cases. In the metastases, the ERG rearrangement was present in 10 cases and associated with deletion of the 5' ERG gene in 6 cases. In unifocal prostate cancers, the status of the ERG rearrangement was concordant between the primary prostate cancer and metastasis in 5 of 6 cases. In multifocal prostate cancer, despite a significant interfocal discordance, the status of the ERG rearrangement was concordant between the index (largest) primary tumor focus and metastasis in all 13 cases. Our study demonstrates a close relationship of the TMPRSS2-ERG gene fusion status between primary and metastatic prostate cancer. The concordance of the ERG gene rearrangement status between the index primary tumor focus and metastasis suggests that metastasis most likely arises from the index tumor focus in multifocal prostate cancer.

PURPOSE: We aimed to analyze whether ERG rearrangement in biopsies could be used to assess subsequent cancer diagnosis in high-grade prostatic intraepithelial neoplasia (HGPIN) and the risk of lymph node metastasis in early prostate cancer. EXPERIMENTAL DESIGN: Samples from 523 patients (361 with early prostate cancer and 162 with HGPIN) were collected prospectively. On the basis of the cutoff value established previously, the 162 patients with HGPIN were stratified to two groups: one with an ERG rearrangements rate >/=1.6% (n = 59) and the other with an ERG rearrangements rate <1.6% (n = 103). For the 361 prostate cancer cases undergoing radical prostatectomy, 143 had pelvic lymph node dissection (node-positive, n = 56 and node-negative, n = 87). All ERG rearrangement FISH data were validated with ERG immunohistochemistry. RESULTS: A total of 56 (of 59, 94.9%) HGPIN cases with an ERG rearrangements rate >/=1.6% and 5 (of 103, 4.9%) HGPIN cases with an ERG rearrangements rate <1.6% were diagnosed with prostate cancer during repeat biopsy follow-ups (P < 0.001). There were significant differences in ERG rearrangement rates between lymph node-positive and -negative prostate cancer (P < 0.001). The optimal cutoff value to predict lymph node metastasis by ERG rearrangement was established, being 2.6% with a sensitivity at 80.4% [95% confidence interval (CI), 67.6-89.8] and a specificity at 85.1% (95% CI, 75.8-91.8). ERG protein expression by immunohistochemistry was highly concordant with ERG rearrangement by FISH. CONCLUSIONS: The presence of ERG rearrangement in HGPIN lesions detected on initial biopsy warrants repeat biopsies and measuring ERG rearrangement could be used for assessing the risk of lymph node metastasis in early prostate cancer.

Castration-resistant prostate cancer is the second most common cause of cancer death and results in a median survival of less than 2 years. In prostate cancer, fusions between TMPRSS2 and ERG are common. The ERG rearrangement prevalence in local recurrent castration-resistant prostate cancer compared to distant metastatic prostate cancer is unknown. We investigated the frequency of ERG rearrangement in local recurrent castration-resistant prostate cancer compared to distant metastatic prostate cancer, and assessed for associations between androgen receptor (AR) amplification and ERG rearrangement status. Samples from 134 patients diagnosed with prostate cancer (84 local recurrent castration resistant prostate cancer, 55 distant metastatic prostate cancer) were assessed for their ERG rearrangement and AR amplification status by fluorescence in situ hybridization. Statistical analysis was performed using the chi (2) test. We found that the ERG rearrangement occurs at a significantly lower frequency in distant metastatic prostate cancer (25 %) than in local recurrent castration-resistant prostate cancer (45 %). The AR amplification frequencies were 45 and 35 % in local recurrent castration-resistant prostate cancer and distant metastatic prostate cancer, respectively. The ERG rearrangement occurred at a lower frequency in distant metastatic prostate cancer compared to local recurrent castration-resistant prostate cancer.