ERG rearrangement in local recurrences compared to distant metastases of castration-resistant 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 χ (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.

Improved method of detecting the ERG gene rearrangement in prostate cancer using combined dual-color chromogenic and silver in situ hybridization.

The recently detected TMPRSS2-ERG fusion gene was revealed as a recurrent and prevalent prostate cancer (PCa)-specific event, potentially qualifying it for clinical use. To detect this alteration, fluorescence in situ hybridization (FISH) is the method of choice. However, FISH has some disadvantages for widespread adoption in clinical practice. Subsequently, chromogenic in situ hybridization, which uses organic chromogens, and enzymatic metallography silver in situ hybridization have emerged as promising bright-field alternatives. Compared with chromogenic in situ hybridization, silver in situ hybridization signals are very distinct and superior with regard to signal clarity and resolution, but the method excludes multicolor protocols. Based on the ERG break-apart FISH assay, we established a dual-color ERG break-apart assay using combined chromogenic in situ hybridization and silver in situ hybridization (CS-ISH) and compared these results with those obtained by FISH. We assessed 178 PCa and 10 benign specimens for their ERG rearrangement status by applying dual-color FISH and CS-ISH ERG break-apart assays to consecutive sections. We observed a highly significant concordance (97.7%) between FISH- and CS-ISH-based results (Pearson's correlation coefficient = 0.955, P < 0.001). Our findings demonstrate that the ERG rearrangement status can reliably be assessed by CS-ISH. Further, the CS-ISH technique combines the accuracy and precision of FISH with the ease of bright-field microscopy. This tool allows a much broader spectrum of applications in which to study the biological role and clinical use of ERG rearrangements in PCa.

Relevance of cohort design for studying the frequency of the ERG rearrangement in prostate cancer.

AIMS: ERG rearrangements, mostly resulting in TMPRSS2-ERG fusions, are frequent alterations in prostate cancer (PCa), with a frequency ranging from 15% to 78%. As the reason for this variability is unknown, our aim was to investigate the ERG rearrangement frequency with a cohort design. METHODS AND RESULTS: We assessed three well-defined cohorts for ERG rearrangements, using fluorescence in situ hybridization (FISH). The first cohort comprised 119 prostatectomy specimens. The second and third cohorts included incidentally diagnosed PCa [71 cystoprostatectomy specimens, and 105 transurethral resection of the prostate (TURP) specimens]. Seventy of 119 (59%) cases of the prostatectomy cohort harboured ERG rearrangements. Regarding zonal origin, 2/11 (18%) transition zone (TZ) foci and 75/145 (52%) peripheral zone (PZ) foci harboured ERG rearrangements. Within the cystoprostatectomies, 24/71 (34%) cases harboured ERG rearrangements. Regarding zonal origin, 2/9 (22%) TZ foci and 26/86 (30%) PZ foci harboured ERG rearrangements. PCa incidentally identified by TURP harboured ERG rearrangements in 31/105 (29%) cases. CONCLUSIONS: ERG rearrangements occur in TZ PCa, although at a lower frequency than in PZ PCa. We confirmed that approximately half of all prostatectomies harbour ERG rearrangements. However, the frequency in incidentally diagnosed PCa cohorts was significantly lower, even if multifocality was considered. Consequently, zonal origin and cohort design are key for studying the clinical implications of ERG rearrangements.

SOX2 gene amplification and protein overexpression are associated with better outcome in squamous cell lung cancer.

The transcription factor SOX2 (3q26.3-q27) is a key regulator of foregut development and an embryonic stem cell factor cooperating during induction of pluripotency in terminally differentiated somatic cells. Recently, we found SOX2 to be amplified in a subset of squamous cell lung and esophageal cancers. The aim of this study was to explore the prognostic role of SOX2 in a large series of squamous cell carcinomas and adenocarcinomas of the lung. A total of 891 samples from two independent population-based cohorts were assessed by fluorescence in situ hybridization and immunohistochemistry. Furthermore, we assessed for associations between SOX2 amplification/upregulation and clinicopathological features. Similar results were found in the two cohorts. Within squamous cell carcinoma cases, 8% high-level as well as 68 and 65% low-level SOX2 amplifications occurred in the two cohorts, respectively. In adenocarcinomas, no high-level amplification was found and low-level amplification occurred in 6% of the two cohorts. Within squamous cell carcinomas of one cohort, SOX2 amplification was associated with lower tumor grade, while higher levels of SOX2 expression were related to younger age, smaller tumor size, and lower probability of angiolymphatic invasion and metastasis. High SOX2 expression levels proved to be a marker for prolonged overall survival among patients with squamous cell carcinomas. In conclusion, SOX2 amplification and upregulation are frequent events in squamous cell carcinomas of the lung and are associated with indicators of favorable prognosis.

ERG rearrangement in small cell prostatic and lung cancer.

AIMS: Small cell prostatic cancer is a rare but aggressive disease. Currently, its histogenetic origin is unclear and its distinction from metastatic small cell lung cancer is challenging. The aim of our study was to determine whether the ERG rearrangement commonly observed in acinar prostatic cancer can distinguish small cell prostatic cancer from small cell lung cancer samples. METHODS AND RESULTS: We assessed 15 small cell prostatic cancers and 22 small cell lung cancers for ERG rearrangement using fluorescence in situ hybridization. Commonly used and novel immunohistochemical markers (i.e. androgen receptor, calcium activated nucleotidase 1, Golgi phosphoprotein 2, prostate-specific antigen, prostate-specific membrane antigen, CD56, epithelial membrane antigen, thyroid transcription factor 1, chromogranin A, synaptophysin and Ki67) were further studied. ERG rearrangement occurred in 86% of small cell prostatic cancers but in none of the small cell lung cancers and was the best marker to differentiate between both tumours (P < 0.0001). CONCLUSIONS: The ERG rearrangement is commonly observed in small cell prostatic cancer, supporting the hypothesis that ERG rearrangement occurs in aggressive prostatic cancers. Furthermore, the ERG rearrangement is the most significant marker to differentiate between small cell prostatic cancer and small cell lung cancer. Moreover, our data suggest that small cell prostatic cancer is not a tumour entity on its own, but a dedifferentiated variant of common acinar prostatic cancer.

ERG rearrangement is specific to prostate cancer and does not occur in any other common tumor.

Identification of specific somatic gene alterations is crucial for the insight into the development, progression, and clinical behavior of individual cancer types. The recently discovered recurrent ERG rearrangement in prostate cancer might represent a prostate cancer-specific alteration that has not been systematically assessed in tumors other than prostate cancer. Aim of this study was to assess, whether the ERG rearrangement and the distinct deletion site between TMPRSS2 and ERG, both predominantly resulting in a TMPRSS2-ERG fusion, occur in tumors other than prostate cancer. We assessed 54 different tumor types (2942 samples in total) for their ERG rearrangement status by fluorescence in situ hybridization (FISH). To calibrate, we analyzed 285 prostate cancer samples for the ERG rearrangement frequency. Additionally, we interrogated a high-resolution single nucleotide polymorphism (SNP) data set across 3131 cancer specimens (26 tumor types) for copy number alterations. None of the 54 different tumor types assessed by FISH harbored an ERG rearrangement, whereas the prostate cancer samples revealed an ERG rearrangement in 49.5% of cases. Furthermore, within the 26 tumor types assessed for copy number alterations by SNP, the distinct deletion site between TMPRSS2 and ERG (21q22.2-3) was detectable exclusively in prostate cancer. Although Ewing's sarcoma and AML have known rearrangements rarely involving ERG, we hypothesize that the ERG rearrangement as well as the distinct deletion site on 21q22.2-3 between TMPRSS2 and ERG are prostate-cancer-specific genomic alterations. These observations provide further insight into the oncogenesis of prostate cancer and might be critical for the development of ERG rearrangement assessment as a clinical tool.