ERG Immunohistochemistry Research Articles

Abstract 1961: Discovery and validation of prostate cancer biomarkers of biochemical recurrence in low-risk prostate cancer patients

Abstract Introduction: Prostate cancer (CaP) is predominantly indolent disease with a small fraction of patients undergoing metastatic progression. Therefore, it is critical to identify prognostic markers for the early detection of an aggressive subtype. We hypothesized that tissue specimens from early-stage, low risk CaP may harbor predictive prognostic signatures for disease progression after radical prostatectomy. Previously, we had systematically evaluated and optimized the NanoString platform for CaP gene expression analysis in formalin fixed paraffin embedded (FFPE) whole mounted prostate specimens. The goal of the study is to validate the CPDR findings on the differential mRNA expression of candidate markers from patients with BCR (biochemical recurrence) and non-BCR in an independent cohort. Methods: This is a retrospective case cohort study based on 78 tumor-normal paired (N=156) archived whole mounted FFPE prostate samples received from biobank at UTHSCSA. We performed an optimized NanoString analysis of 203-CaP probe set to evaluate the association of markers with BCR outcome in a racially diverse patient population comprising of 21.6% AA and 78.38% CA men. The cohort comprised of 28 patients with BCR, and 50 patients with no BCR (based on a minimum of 5 years of follow-up). ERG gene expression was validated by immunohistochemistry (IHC) assay using CPDR ERG-MAb (9FY). Normalized nCounter gene expression data was analyzed using the NanoString nSolver (v 4.0) platform. Fisher exact and Wilcoxon-Mann-Whitney tests were used for categorical and continuous variables respectively. Results: We found 96.1% (73/76) concordance between ERG IHC and NanoString datasets, which provides strong QC and validation for NanoString data. ERG positive tumors had strong expression of both TMPRSS2-ERG fusion and several other ERG splice forms. Additionally, the prostate epithelial cell markers PSA, MSMB and PAP had the highest signals in all samples reflecting the prostate epithelial origin of the specimens. Differential gene expression analysis showed that a total of 37 genes were found to be significantly (P adj <0.05) different across tumors and normal. Established CaP genes like AMACR, PCA3, OR51E2, ERG, HOXC6, DLX1, CACNA1D and PSGR were most highly over-expressed in tumors compared to matched normal while GSTP1, CAV1, PAP and MSMB were significantly downregulated in tumors compared to adjacent normal prostate epithelia. Race stratified analysis in this randomly selected patient cohort showed that AA men were found to be significantly younger (median age: 56 years AA vs. 63 years CA; p 0.01) and had higher frequency of BCR events (p 0.004) than CA men. Data analysis for disease outcome across AA and CA men is ongoing. Conclusions: We confirmed that NanoString approach is useful for evaluation of prognostic biomarker candidates in prostate cancer using FFPE specimens. Citation Format: Indu Kohaar, Kaitlyn Bejar, Denise Young, Yingjie Song, Jiji Jiang, Jacob Kagan, Sudhir Srivastava, Javier Hernandez, Gregory Chesnut, Isabell A. Sesterhenn, Robin J. Leach, Gyorgy Petrovics. Discovery and validation of prostate cancer biomarkers of biochemical recurrence in low-risk prostate cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1961.

Gene fusion characterisation of rare aggressive prostate cancer variants-adenosquamous carcinoma, pleomorphic giant-cell carcinoma, and sarcomatoid carcinoma: an analysis of 19 cases.

To evaluate the molecular underpinnings of the rare aggressive prostate cancer variants adenosquamous carcinoma, pleomorphic giant-cell carcinoma, and sarcomatoid carcinoma. We retrieved 19 tumours with one or more variant(s), and performed ERG immunohistochemistry, a next-generation sequencing assay targeting recurrent gene fusions, and fluorescence in-situ hybridisation (FISH) for ERG and BRAF. Divergent differentiation included: sarcomatoid carcinoma (n=10), adenosquamous carcinoma (n=7), and pleomorphic giant-cell carcinoma (n=7). Five patients had more than one variant. Four had variants only in metastases. ERG rearrangement was detected in nine (47%, seven via sequencing, showing TMPRSS2-ERG fusions and one GRHL2-ERG fusion, and two via FISH, showing rearrangement via deletion). ERG was immunohistochemically positive in the adenocarcinoma in eight of nine (89%) patients, but was immunohistochemically positive in the variant in only five of nine patients (56%, typically decreased). One patient had a false-positive ERG immunohistochemical result in the sarcomatoid component despite a negative FISH result. Two (11%) harboured BRAF fusions (FAM131A-BRAF and SND1-BRAF). ERG fusions are present in these rare prostate cancer variants with a frequency close to that in conventional prostate cancer (9/19, 47%). ERG immunohistochemistry usually detects rearrangement in the adenocarcinoma, but is less sensitive for the variant histology, with weak to negative staining. Adenosquamous and sarcomatoid variants can, particularly, occur together. Molecular assessment may be an additional tool in selected cases to confirm the prostatic origin of unusual tumours. The presence of two BRAF rearrangements suggests that this gene fusion may be enriched in this setting, as RAF kinase fusions have been previously reported in 1-2% of prostate cancers.

Detecting FLI1 Fusion by Immunohistochemistry (IHC) Stain in Prostatic Adenocarcinoma

Abstract Objectives The most common genetic alterations in prostate cancer are fusions of ERG and other members of the E26 transformation-specific (ETS) family of transcription factors, including ETV1, ETV4, and FLI1. Analyzing TCGA data, we found that similar to ERG fusion, FLI1 fusion-associated FLI1 mRNA level increases. ERG IHC stain has been a surrogate test for ERG fusion. Therefore, we hypothesize that FLI IHC stain could also be used to detect FLI1 fusion in prostate cancer. Methods In total, 111 primary prostate adenocarcinoma (>10% by volume) cases from our institute were selected for tissue microarray (TMA) construction. The regular full section slides and TMA slides were subject to IHC stain of ERG and FLI1 (Santa Cruz, SC-113). The criteria for positive FLI1 are (1) nuclear staining; (2) only in tumor cells, not in nontumor cells; and (3) FLI1-positive cells should be negative for ERG IHC staining. Results For prostate TMA slides, ~50% of cases were positive for ERG; ~30% of cases were weakly positive for FLI1. However, all of the FLI1 weakly positive cases were positive for ERG as well possibly due to cross-reactivity between ERG and FLI1, which was demonstrated in other studies. Conclusion Overall, we conclude that the cross-reactivity between FL1 and ERG precluded the detection of FLI1 fusion in prostatic adenocarcinoma under current conditions. We are in the process of selecting some cases to detect FLI1 fusion by next-generation sequencing (NGS) and FISH.

Abstract 1568: Clinical implications of tmprss2-erg fusion and tumor location in prostate cancer

Abstract Introduction: There is limited data on the impact of race on tumor location and TMPRSS2-ERG (ERG) gene fusion status in Prostate Cancer (PCa). African American men (AAM) often lack the ERG fusion and are likely to experience poor outcomes. Nonetheless, the extent to which ERG status, race, and tumor location impacts PCa outcomes remains unclear. Methods: This multi-institutional study included a retrospective cohort of 495 AAM and 422 European American men (EAM) who received prostatectomy at Moffitt Cancer Center (MCC) and University of Pennsylvania Health system (UPHS). To assess the race-dependent variation in ERG protein expression and its association with tumor location and PCa pathology, ERG antibody staining on 4 micron sections of FFPE blocks were carried out on all samples. ERG expression was categorized as ERGpos and ERGneg by two pathologists. Additionally, the staining pattern of ERG was analyzed within ERGpos tumors. A review of anatomic location of the dominant tumor lesions was performed and analyzed using methods of categorical analysis and logistic regression. Alpha value of < 0.05 was considered as statistically significant. Results: In all samples, analysis of ERG immunohistochemistry (IHC) yielded 39.7% ERGpos and 60.6% ERGneg. Variability in histopathologic expression of ERG was significant between races with AAM being more likely to lack TMPRSS2-ERG fusion (ERGneg) compared to EAM, (62% vs 38%, p < 0.001). Lack of ERG fusion was also associated with anatomically distinct tumor location with 72.1% of anteriorly located tumors having ERGneg staining, while only 27.9% were ERGpos, (p < 0.001). Among ERGpos patients, AAM (65.2%) showed significant heterogeneous expression of ERG compared to EAM (31.8%). Furthermore, ERGneg status was associated with higher pretreatment PSA. In a multivariate logistic regression model adjusted for tumor location and race, ERGneg tumors were more likely to have Gleason Score 4+3=7 (Grade Group 3) or higher compared with ERGpos tumors, Odds ratio 2.07, 95% CI 1.20 - 3.56, p = 0.008. Conclusions: The absence of TMPRSS2-ERG fusion is associated with higher grade disease and is a strong predictor for anatomic tumor location within the prostate gland. The clinical implications of ERGneg tumors among AAM and its association with anteriorly located tumors can be vital in addressing disparities in PCa. Citation Format: Kosj Yamoah, Shivanshu Awasthi, Priti Lal, Arash O. Naghavi, Shelly Mahajan, Jong Y. Park, Rob Rounbehler, Travis Gerke, Anders Berglund, Julio PowSang, Jasreman Dhillon, Timothy R. Rebbeck. Clinical implications of tmprss2-erg fusion and tumor location in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1568.

Utility of ERG Immunohistochemistry for Evaluation of Lymphovascular Invasion in Testicular Germ Cell Tumors: A Retrospective Pilot Study.

Lymphovascular invasion (LVI) of testicular germ cell tumors (GCT) is an important stage-determining variable in the evaluation of radical orchiectomy specimens. ERG endothelial cell expression, as detected by immunohistochemistry (IHC), robustly highlights lymphovascular spaces, and thus, we sought to assess the utility of ERG IHC for evaluation of GCT LVI. Hematoxylin and eosin (H&E) slides from a retrospective cohort of 25 GCT radical orchiectomy specimens (emanating from a parent cohort of 159 radical orchiectomy GCT cases identified between 2003 and 2013) were reviewed, and sections with foci of positive or equivocal LVI were identified. ERG IHC was performed on sections off the surface of corresponding paraffin tissue blocks. All foci were then rescored as positive, equivocal, or negative for LVI based on ERG endothelial cell expression. Twenty-three and 13 foci were positive or equivocal for LVI by H&E staining, respectively. Among the H&E positive LVI foci, 20 (87%) were ERG IHC positive, whereas of the H&E equivocal LVI foci, 5 (38%) were ERG IHC positive, 3 (23%) were ERG IHC negative, and 2 (15%) were ERG IHC equivocal; all other foci were lost for evaluation. Overall, ERG IHC helped resolve the LVI status of 61% of foci deemed equivocal for LVI by H&E staining only. Although ERG IHC is useful in confirming definitive LVI status in a subset of GCT cases, the overall clinical impact of ERG IHC is limited for H&E equivocal LVI foci in this specific retrospective patient cohort. Overall, in carefully selected clinical scenarios, these data suggest a supportive role for ERG IHC in evaluation of GCT LVI in radical orchiectomy specimens.

Molecular characterization of longitudinally tracked prostate cancer foci in men on active surveillance for low-risk disease.

56 Background: The biological trajectory of Gleason score 6 (GS6) prostate cancer (PCa) in men on active surveillance (AS) is unknown. We herein evaluate the potential for high grade PCa to arise clonally from GS 6 disease and determine the capacity of tissue-based biomarkers to predict grade progression. Methods: Men on AS with GS6 PCa who underwent magnetic resonance imaging/ultrasound (MRI/US) fusion biopsy on two occasions from 2012 through 2017 were enrolled. Tumor foci were tracked and re-sampled using the MRI/US fusion biopsy platform. ERG immunohistochemistry (IHC) and DNA/RNA next generation sequencing (NGS) were performed on formalin-fixed paraffin-embedded (FFPE) initial and repeat biopsy specimens to assess tumor clonality and evaluate candidate molecular markers of PCa grade progression. Results: Sixty-seven men of median age 64 years (IQR 59-69) and PSA 4.9 ng/ml (IQR 3.3-6.4) underwent repeat sampling of a single tracked tumor focus using MRI/US fusion biopsy. The median interval to repeat biopsy was 11 months (IQR 6-13). On repeat biopsy, 31 (46%) men progressed to high-grade (GS≥7) disease (n = 24, GS 3+4 = 7; n = 7, GS ≥4+3 = 7). Among the 67 subjects, ERG IHC status was concordant between initial and repeat biopsy in 64 (96%). Of 134 total specimens obtained (67 initial + 67 repeat biopsies), ERG status determined by NGS was concordant with ERG status by IHC in 132 (99%). Comparing the initial biopsy specimens in men who did versus did not undergo grade progression on follow up biopsy, derived cell cycle progression (CCP) scores (median 57.3 vs. 44.0, p = 0.11) and genomic prostate scores (GPS; median 73.8 vs. 64.4, p = 0.15) were not significantly different. Similarly, expression of FOLH1, PCAT4, SCHLAP1, and SPINK1 on initial biopsy did not significantly differ among men who did and did not undergo grade progression. Conclusions: Use of MRI/US fusion biopsy facilitated resampling of the same clonal focus of cancer over time, with high concordance of ERG status determined by both IHC and NGS. Derived genomic classifiers and candidate individual gene expression markers measured on initial biopsy tissue were not significantly different between patients who progressed and those who did not.

Intrafocal heterogeneity of ERG protein expression and gene fusion pattern in prostate cancer.

Prostate cancer is considered to be highly heterogeneous, with various morphologic features and biologic behaviors. The TMPRSS2-ERG gene fusion is the most frequently observed genetic aberration in prostate cancer. The aim of this study was to elucidate the intrafocal heterogeneity of ERG gene fusion status. ERG immunohistochemistry (IHC) was performed in samples from 168 prostate cancer patients who had undergone radical prostatectomy, and 40 cases showing ERG-positive IHC staining were selected for tissue microarray (TMA) construction. Two to six representative cores were selected from each tumor focus. In the cases with heterogeneous ERG IHC staining intensity, the areas showing different intensities were separately selected. Using the TMA blocks, IHC and fluorescence in situ hybridization (FISH) were conducted to evaluate the heterogeneity of ERG protein expression and ERG fusion gene patterns, respectively, in a single tumor focus. Heterogeneity of ERG IHC staining was defined as the simultaneous presence of negative and positive cores in the same tumor focus. Heterogeneity of ERG FISH was defined by the presence of cores with positive and negative FISH signals or cores with break-apart and interstitial deletion FISH signals in the same tumor focus. A total of 202 TMA cores were isolated from 40 ERG-positive cases. Of the 202 total cores, 19 were negative for ERG IHC staining, and 46 showed 1+, 52 showed 2+, and 85 showed 3+ ERG staining intensity. Eleven cores were negative for ERG FISH signal, 119 cores showed ERG break-apart FISH signals, and the remaining 72 cores revealed interstitial deletion. Intrafocal heterogeneity of ERG IHC staining was found in 20% (8/40) of cases, and intrafocal heterogeneity of ERG gene fusion pattern was found in 32.5% (13/40) of cases. In summary, this study showed significantly frequent intrafocal heterogeneity of ERG protein expression, gene fusion status and fusion pattern. This heterogeneity can be caused by the development of subclones during cancer progression or the intermingling of different tumors.

Effect of pathologic revision and Ki67 and ERG immunohistochemistry on predicting radical prostatectomy outcome in men initially on active surveillance

To investigate if pathologic biopsy reevaluation and implementation of immunohistochemical biomarkers could improve prediction of radical prostatectomy outcome in men initially on active surveillance. Biopsy specimens from diagnosis until switching to radical prostatectomy in men initially on active surveillance in the Dutch part of the Prostate cancer Research International Active Surveillance (PRIAS) study were collected and revised by a single pathologist. Original and revised biopsy Gleason score were compared and correlated with radical prostatectomy Gleason score. Biopsy specimens were immunohistochemically stained for Ki67 and ERG. Predictive ability of clinical characteristics and biomarkers on Gleason ≥7 or ≥pT3 on radical prostatectomy was tested using logistic regression and ROC curve analysis. A total of 150 biopsies in 95 men were revised. In 13% of diagnostic or second-to-last biopsies and 20% of the last biopsies on active surveillance revision of Gleason score resulted in change of recommendation (ie, active treatment or active surveillance). Concordance with Gleason score on radical prostatectomy was however similar for both the revised and original Gleason on biopsy. Ki67 and ERG were not statistically significant predictors of Gleason ≥7 or ≥pT3 on radical prostatectomy. Although interobserver differences in pathology reporting on biopsy could result in a change of management strategy in approximately 13-20% of men on active surveillance, both pathological revision and tested biomarkers (Ki67 and ERG) did not improve prediction of outcome on radical prostatectomy. Undersampling of most aggressive tumor remains the main focus in order to increase accurate grading at time of treatment decision making.

Comprehensive Determination of Prostate Tumor ETS Gene Status in Clinical Samples Using the CLIA Decipher Assay

ETS family gene fusions are common in prostate cancer and molecularly define a tumor subset. ERG is the most commonly rearranged, leading to its overexpression, followed by ETV1, ETV4, and ETV5, and these alterations are generally mutually exclusive. We validated the Decipher prostate cancer assay to detect ETS alterations in a Clinical Laboratory Improvement Amendments-accredited laboratory. Benchmarking against ERG immunohistochemistry and ETV1/4/5 RNA in situ hybridization, we examined the accuracy, precision, and reproducibility of gene expression ETS models using formalin-fixed, paraffin-embedded samples. The m-ERG model achieved an area under curve of 95%, with 93% sensitivity and 98% specificity to predict ERG immunohistochemistry status. The m-ETV1, -ETV4, and -ETV5 models achieved areas under curve of 98%, 88%, and 99%, respectively. The models had 100% robustness for ETS status, and scores were highly correlated across sample replicates. Models predicted 41.5% of a prospective radical prostatectomy cohort (n=4036) to be ERG+, 6.3% ETV1+, 1% ETV4+, and 0.4% ETV5+. Of prostate tumor biopsy samples (n=509), 41.2% were ERG+, 8.6% ETV1+, 0.4% ETV4+, and none ETV5+. Higher Decipher risk status tumors were more likely to be ETS+ (ERG or ETV1/4/5)in the radical prostatectomy and the biopsy cohorts (P<0.05). These results support the utility of microarray-based ETS status prediction models for molecular classification of prostate tumors.

Inside the USCAP Journals

Inside the USCAP Journals

Abstract 1763: Body size and incidence of TMPRSS2:ERG fusion-positive and fusion-negative prostate cancer

Abstract Background: Evidence suggests that genetic, lifestyle, and hormonal factors are differentially associated with the incidence of TMPRSS2:ERG fusion-positive and fusion-negative tumors, suggesting that these molecular subtypes have distinct etiologies. There is scant literature on whether anthropometrics are differentially associated the risk of developing fusion-positive and fusion-negative prostate cancer. Methods: We examined the associations between adult height, recalled BMI at age 21, and updating BMI over time with risk of prostate cancer defined by TMPRSS2:ERG subtype using a prospective cohort of 49,372 men from the Health Professionals Follow-up Study. Tumor TMPRSS2:ERG status was assessed by ERG immunohistochemistry on tissue microarrays constructed from radical prostatectomy of the prostate specimens. We utilized multivariable competing risks models to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for risk of fusion-positive disease and, separately, fusion-negative disease. Results: During 23 years of follow-up, we identified 5,847 total prostate cancer cases. Among them, 2,402 were treated with RP, of whom 913 (15.6% of all cases) were assayed for ERG status. Height (per 5 inches) was positively associated with the risk of developing ERG-positive prostate cancer (HR = 1.24, 95% CI 1.03-1.50), but not associated with ERG-negative disease (HR = 0.98, 95% CI = 0.82-1.18, Pheterogenity = 0.07). Updated BMI (per 5 kg/m2) was inversely associated with the risk of developing ERG-positive disease (HR = 0.86, 95% CI = 0.74-1.00), but not associated with ERG-negative disease (HR = 1.03, 95% CI = 0.90-1.18, Pheterogenity = 0.07). BMI at age 21 was not differentially associated with the risk of developing ERG-positive or ERG-negative disease. Conclusion: Our results suggest that height and obesity are differentially associated with the risk of developing fusion-positive and fusion-negative prostate cancer. Citation Format: Thomas Ahearn, Rebecca E. Graff, Andreas Pettersson, Claire Pernar, Sarah C. Markt, Kathryn M. Wilson, Michelangelo Fiorentino, Massimo Loda, Edward L. Giovannucci, Lorelei A. Mucci. Body size and incidence of TMPRSS2:ERG fusion-positive and fusion-negative prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1763.

Pre-diagnostic circulating sex hormone levels and risk of prostate cancer by ERG tumour protein expression.

Background:Experimental studies have shown androgen receptor stimulation to facilitate formation of the TMPRSS2:ERG gene fusion in prostate cell lines. No study has tested whether higher pre-diagnostic circulating sex hormone levels in men increase risk of developing TMPRSS2:ERG-positive prostate cancer specifically.Methods:We conducted a nested case–control study of 200 prostate cancer cases and 1057 controls from the Physicians' Health Study and Health Professionals Follow-up Study. We examined associations between pre-diagnostic circulating levels of total testosterone, free testosterone, DHT, androstanediol glucuronide, estradiol, and SHBG and risk of prostate cancer by TMPRSS2:ERG status. TMPRSS2:ERG was estimated by ERG immunohistochemistry. We used multivariable unconditional polytomous logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for risk of ERG-positive (n=94) and, separately, ERG-negative (n=106) disease.Results:Free testosterone was significantly associated with the risk of ERG-positive prostate cancer (OR: 1.37, 95% CI: 1.05–1.77), but not ERG-negative prostate cancer (OR: 1.09, 95% CI: 0.86–1.38) (Pdiff=0.17). None of the remaining hormones evaluated showed clear differential associations with ERG-positive vs ERG-negative disease.Conclusions:These findings provide some suggestive evidence that higher pre-diagnostic free testosterone levels are associated with an increased risk of developing TMPRSS2:ERG-positive prostate cancer.

Pre-diagnostic circulating sex hormone levels and risk of prostate cancer by TMPRSS2:ERG status.

93 Background: Experimental studies have shown that androgen receptor stimulation can facilitate formation of the TMPRSS2:ERG gene fusion in prostate cell lines. No study has tested whether higher pre-diagnostic circulating sex hormone levels in men increase the risk of developing TMPRSS2:ERG positive prostate cancer specifically. Methods: We conducted a nested case-control study of 200 prostate cancer cases and 1,057 controls from the Physicians’ Health Study and Health Professionals Follow-up Study. We examined associations between pre-diagnostic circulating levels of total testosterone, free testosterone, DHT, androstanediol glucuronide, estradiol, and SHBG and risk of prostate cancer by TMPRSS2:ERG status. TMPRSS2:ERG was assessed by ERG immunohistochemistry. We used multivariable unconditional polytomous logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for risk of fusion-positive (n = 94) and, separately, fusion-negative (n = 106) disease. Results: Free testosterone was significantly associated with the risk of ERG-positive prostate cancer (OR: 1.37, 95% CI: 1.05-1.77), but not ERG-negative prostate cancer (OR: 1.09, 95% CI: 0.86-1.38) (p-diff: 0.17). None of the remaining hormones evaluated showed clear differential associations with ERG-positive versus ERG-negative disease. Conclusions: These findings provide some suggestive evidence that higher pre-diagnostic free testosterone levels are associated with an increased risk of developing TMPRSS2:ERG positive prostate cancer but are not associated with prostate cancer that lacks TMPRSS2:ERG.

ERG Expression in Prostate Needle Biopsy: Potential Diagnostic and Prognostic Implications.

To investigate the prognostic and diagnostic value of ERG immunohistochemistry (IHC) in prostate needle biopsy when combined with AMACR-CK5/6. ERG IHC was assessed in 119 consecutive prostate needle biopsies where the dual-stain AMACR-CK5/6 IHC was ordered and in 16 cases with a Gleason score (GS) ≥7. IHC results were evaluated in prostate carcinoma (PCA), high-grade prostatic intraepithelial neoplasia (HGPIN), HGPIN with adjacent atypical glands (PINATYP), atypical/suspicious (ASAP) foci, and benign PCA mimickers. GS, HGPIN, extraprostatic extension, perineural invasion, bilateralism of PCA, largest percent of core, and the overall percent of tissue involved by PCA were recorded. ERG was detected in 36% of PCA, 27% of HGPIN, 13% of ATYP/PINATYP, and none of benign mimickers. ERG-positive HGPIN was strongly associated with ERG-positive PCA in the same core compared with ERG-negative HGPIN (P<0.0001). Positive ERG expression in PCA was inversely related to GS and showed trends toward association with higher volume and bilateral disease. ERG was more specific for PCA than AMACR (0.87 vs. 0.23), but less sensitive (0.36 vs. 0.95). In conclusion, ERG IHC is of limited additional diagnostic value when added to AMACR and CK5/6. ERG expression is inversely related to GS and is associated with bilateral involvement and higher PCA tumor volume. ERG-positive HGPIN is strongly associated with the presence of PCA in the same core. Studies investigating the prognostic value of ERG in HGPIN should be implemented to address whether patients with ERG-positive HGPIN are at increased risk for subsequent PCA development.

Abstract 2016: Evaluation of prostate cancer biomarkers and therapeutic targets in FFPE specimens using the NanoString platform

Abstract Introduction: Identification of prognostic indicators of disease progression is one of the highest priorities in prostate cancer (CaP) research. The majority of CaP tissue specimens available for biomarker discovery and validation are formalin fixed paraffin embedded (FFPE) specimens. The RNA quality of these tissues for traditional gene expression analysis approaches is not adequate, especially of cases with long term- follow up necessary for prognostic marker studies. We systematically evaluated and optimized the NanoString platform for CaP gene expression analysis in FFPE whole mounted prostate specimens with up to 15 years follow up. Methods: NanoString readouts were compared between a series of input total RNA prepared through different tissue dissection methods. We then performed NanoString analysis of 151-CaP probe set on 63 archived CaP samples to evaluate this modified protocol. ERG gene expression was validated by immunohistochemistry (IHC) assay using CPDR ERG-MAb (9FY). Results: We have performed NanoString analysis of CPDR designed 151- CaP gene panel on whole-mounted prostate tissue specimens using our optimized protocol. The prostate epithelial cell markers KLK3, MSMB and PAP had the highest signals in all samples reflecting the prostate epithelial origin of the specimens. Established CaP specific genes, such as AMACR, PCA3 and PSGR were most highly over-expressed in tumors compared to matched benign prostate epithelium. ERG positive tumors had strong expression of both TMPRSS2-ERG fusion probes and probes for several ERG splice forms (ERG 1,2,3 and 8), with no signals in the matched benign samples. The ERG gene expression status was consistent with blinded ERG IHC results. Conclusions: The feasibility of NanoString profiling in archived whole mounted FFPE prostate specimens was demonstrated. This approach is well suited for a medium throughput evaluation and validation of prognostic biomarker and therapeutic target candidates in CaP. Citation Format: Jocelyn Lee, Wusheng Yan, Denise Young, Yingjie Song, Yongmei Chen, Shilpa Katta, Ahmed Mohamed, Lakshmi Ravindranath, Alagarsamy Srinivasan, Jennifer Cullen, Jacob Kagan, Sudhir Srivastava, Albert Dobi, Inger Rosner, David G. McLeod, Isabell A. Sesterhenn, Shiv Srivastava, Gyorgy Petrovics. Evaluation of prostate cancer biomarkers and therapeutic targets in FFPE specimens using the NanoString platform. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2016. doi:10.1158/1538-7445.AM2015-2016

Association of ERG and TMPRSS2-ERG with grade, stage, and prognosis of prostate cancer is dependent on their expression levels.

There is controversy in the literature on the role of the fusion TMPRSS2-ERG in the pathogenesis and progression of prostate cancer. The quantitative differences in TMPRSS2-ERG fusion expression have received very limited attention in the literature. We have quantitatively analyzed the mRNA levels of TMPRSS2-ERG, ERG, PTEN, and AR (n = 83), as well as ERG immunostaining (n = 78) in a series of prostate tumors. Among the TMPRSS2-ERG cases (n = 57), high fusion levels were associated with GS ≥8 (P = 0.025). ERG mRNA overexpression was associated with GS ≥8 (P = 0.047), and with stage T3-T4 tumors (P = 0.032). Among the ERG overexpressing cases (n = 54), higher expression levels were found in 92.3% of GS ≥8 tumors (P = 0.02). ERG immunostaining, regardless of staining intensity, was also associated with high stage (P = 0.05). There was a statistical association between ERG immunostaining and PSA progression-free survival (Log Rank test, P = 0.048). Decreased PTEN expression was associated with TMPRSS2-ERG (P = 0.01), ERG mRNA overexpression (P = 0.003) and ERG immunostaining (P = 0.007). Furthermore, decreased PTEN expression, alone (P = 0.041) and also combined with TMPRSS2-ERG (P = 0.04) or with ERG overexpression (P = 0.04) was associated with GS ≥7 tumors. Although more studies are needed to further clarify their role, our findings emphasize that the expression levels of the TMPRSS2-ERG fusion and ERG mRNA, rather than their mere presence, are related to a more aggressive phenotype, have an effect on prognosis and could be molecular markers of progression for prostate cancer. Furthermore, ERG immunohistochemistry could be also a potentially useful prognostic factor.

Determination of Optimum Formalin Fixation Duration for Prostate Needle Biopsies for Immunohistochemistry and Quantum Dot FISH Analysis.

Prostate biopsy is the key clinical specimen for disease diagnosis. However, various conditions used during biopsy processing for histologic analysis may affect the performance of diagnostic tests, such as hematoxylin and eosin (H&E) staining, immunohistochemistry (IHC), or in situ hybridization (ISH). One such condition that may affect diagnostic test performance is fixation duration in 10% neutral buffered formalin (NBF). For example, prostate needle biopsies are often <1 mm in diameter and thus overfixed. It is important to understand the impact of tissue fixation duration on diagnostic test performance to enable optimized assay procedures. This study was designed to study the effect of 10% NBF fixation duration of prostate needle biopsy on multiplexed quantum dot (QD) ISH assay of ERG and PTEN, 2 genes commonly altered in prostate cancer. The samples were also evaluated for H&E staining and ERG and PTEN IHC. H&E staining and ERG and PTEN IHC were acceptable for all the durations of fixation tested. For QD ISH, we observed good signals with biopsy samples fixed from 4 to 120 hours. Biopsy specimens fixed between 8 and 72 hours gave the best signal as scored by the study pathologist. In a separate cohort of 18 routinely processed prostate biopsy cores, all cores were stained successfully with the QD ISH assay, and results were 100% concordant to ERG and PTEN IHC. We conclude that 8 to 72 hours duration of fixation for prostate needle biopsies in 10% NBF results in optimal QD ISH assay performance.

MP66-06 OPTIMIZATION OF NANOSTRING PLATFORM FOR EVALUATION OF PROSTATE CANCER BIOMARKERS AND THERAPEUTIC TARGETS IN FFPE SPECIMENS

INTRODUCTION AND OBJECTIVES: Identification of prognostic indicators of disease progression is one of the highest priorities in prostate cancer (CaP) research. The majority of CaP tissue specimens available for biomarker discovery and validation are formalin fixed paraffin embedded (FFPE) specimens. The RNA quality of these tissues for traditional gene expression analysis approaches is not adequate, especially of cases with long termfollow up necessary for prognostic marker studies. We systematically evaluated and optimized the NanoString platform for CaP gene expression analysis in FFPE whole mounted prostate specimens with up to 15 years follow up. METHODS: NanoString readouts were compared between a series of input total RNA prepared through different tissue dissection methods. We then performed NanoString analysis of 151-CaP probe set on 63 archived CaP samples to evaluate this modified protocol. ERG gene expression was validated by immunohistochemistry (IHC) assay using CPDR ERG-MAb (9FY). RESULTS: We have performed NanoString analysis of CPDR designed 151CaP gene panel on whole-mounted prostate tissue specimens using our optimized protocol. The prostate epithelial cell markers KLK3, MSMB and PAP had the highest signals in all samples reflecting the prostate epithelial origin of the specimens. Established CaP specific genes, such as AMACR, PCA3 and PSGR were most highly over-expressed in tumors compared to matched benign prostate epithelium. ERG positive tumors had strong expression of both TMPRSS2-ERG fusion probes and probes for several ERG splice forms (ERG 1,2,3 and 8), with no signals in the matched benign samples. The ERG gene expression status was consistent with blinded ERG IHC results. CONCLUSIONS: The feasibility of NanoString profiling in archived whole mounted FFPE prostate specimens was demonstrated. This approach is well suited for a medium throughput evaluation and validation of prognostic biomarker and therapeutic target candidates in CaP.

Frequent discordance between ERG gene rearrangement and ERG protein expression in a rapid autopsy cohort of patients with lethal, metastatic, castration-resistant prostate cancer.

ERG rearrangements in localized prostate cancer can be detected with high sensitivity and specificity by immunohistochemistry (IHC). However, recent data suggest that ERG IHC may be less sensitive for ERG rearrangements in castration-resistant prostate cancer (CRPC). Thus, we sought to examine ERG protein expression in a cohort of rapid autopsy patients with lethal metastatic CRPC (mCRPC). A tissue microarray (TMA) of tumor sites from these patients was evaluated for ERG, prostate-specific antigen (PSA), and androgen receptor (AR) expression by IHC and correlated with ERG rearrangement status by fluorescent in situ hybridization (FISH). IHC was scored as the product of tumor cell staining intensity (0-3) and percentage of cells positive (0-100) (overall product score range = 0-300). All 16 (100%) ERG rearrangement negative (ERG(neg) ) patients were also negative for ERG tumor cell expression (i.e., IHC product score = 0). Of the 10 ERG rearrangement positive (ERG(pos) ) patients, two (20%) were completely negative for ERG tumor cell expression, while eight (80%) had weak ERG expression (median IHC product score = 5-110). Of these eight ERG(pos) patients, five (63%) had at least one tumor site without any detectable ERG expression. For a given ERG(pos) patient, ERG expression varied both between and within tumor sites; AR and PSA expression also varied between tumor sites, and there was no significant correlation between ERG and AR or PSA expression. These data reveal frequent discordance between ERG IHC and ERG FISH in ERG(pos) patients from this unique cohort of heavily treated lethal mCRPC.

Utility of ERG Versus AMACR Expression in Diagnosis of Minimal Adenocarcinoma of the Prostate in Needle Biopsy Tissue

Adenocarcinoma of the prostate measuring <1 mm in needle core tissue can present a diagnostic challenge. The α-methylacyl-CoA racemase (AMACR) immunostain, a marker of neoplastic prostatic epithelial cells, may be used to evaluate these limited tumor cases, in needle biopsy, with a reported sensitivity ranging to a low of 80%. The use of the ERG immunostain in evaluating prostate cancer is becoming more common, but the utility of this marker in direct comparison with AMACR has not been examined. The purpose of our study was to investigate whether the ERG immunostain adds diagnostic value to AMACR expression in evaluating untreated prostate cancer foci measuring <1 mm in core needle biopsy. We identified 129 blocks from 113 patients with continuous tumor foci measuring <1 mm on core needle biopsy. ERG and AMACR immunostaining analyses were performed on serial sections from the blocks, and expression was assessed by intensity and proportion scores assigned to each stain. Sixty-five of the selected blocks from 63 patients retained tumor foci measuring <1 mm after obtaining deeper sections. Of these 65 tumor foci, 36 were positive for AMACR alone, 28 were positive for AMACR and ERG, and 1 was positive for ERG alone. AMACR had a sensitivity of 99%, and ERG had a sensitivity of 45%. Most cases displayed strong AMACR expression, and only 7 of 65 foci (11%) exhibited weak or negative AMACR expression. Of these 7 foci with weak or negative AMACR expression, only 2 foci were ERG positive. This is the first study to our knowledge that examines the diagnostic utility of ERG expression in comparison with AMACR expression in minimal usual acinar adenocarcinoma of the prostate in core needle biopsy. Our findings suggest that AMACR should be the first-line positive marker for confirmation of a diagnosis of minimal adenocarcinoma of the prostate, when needed. ERG immunohistochemistry is potentially indicated only in uncommon cases of minimal adenocarcinoma when AMACR staining is negative or weak, and in these cases ERG is informative in only a minority (29%) of cases. Evidence-based utilization of diagnostic markers, without their routine overutilization, such as ERG expression in minimal adenocarcinoma, that do not provide added diagnostic value in most cases, is an important principle in application of immunohistochemistry in this era of cost-consciousness.