A. Marije Hoogland

ERG immunohistochemistry is not predictive for PSA recurrence, local recurrence or overall survival after radical prostatectomy for prostate cancer

In prostate cancer genomic rearrangements involving genes encoding ETS transcription factors are commonly present, with androgen-regulated transmembrane protease, serine 2 (TMPRSS2)-v-ets erythroblastosis virus E26 oncogen homologue (ERG) gene fusion occurring in 40–70%. Studies on the predictive value of ERG rearrangement as detected by in-situ hybridization or polymerase chain reaction have resulted in varying outcomes. The objective of this study was to correlate immunohistochemical ERG protein expression with clinico-pathological parameters at radical prostatectomy specimens, and to determine its predictive value for postoperative disease recurrence and progression in a prostate cancer screening cohort. Since androgen receptor is downregulated by ERG in cell lines, we also compared the expression of respective proteins. We selected 481 participants from the European Randomized Study of Screening for Prostate Cancer treated by radical prostatectomy for prostate adenocarcinoma. A tissue microarray was constructed containing representative cores of all prostate cancer specimens as well as 22 xenografts and seven cell lines. Immunohistochemical expression of ERG and androgen receptor was correlated with prostate-specific antigen (PSA), Gleason sum, pT-stage, surgical margins, biochemical recurrence, local recurrence, overall death and disease-specific death. ERG expression was detected in 284 patients (65%). Expression occurred significantly more frequent in patients with PSA ≤10 ng/ml (P=0.024). There was no significant association between ERG and Gleason sum, pT-stage or surgical margin status. PSA (P=0.011), Gleason sum (P=0.003), pT-stage (P=0.001) and surgical margin status (P<0.001) all had independent value for postoperative biochemical recurrence, while positive surgical margin (P=0.021) was the only independent predictor for local recurrence. ERG protein expression did not have prognostic value for the clinical end points in uni- and multivariate analyses. A positive correlation existed between ERG and androgen receptor expression in single tissue cores (P<0.001). In conclusion, immunohistochemical ERG expression has no predictive value for prostate cancer recurrence or progression after radical prostatectomy. Increasing ERG levels are associated with the upregulation of androgen receptor expression in clinical specimens.

Antibody EPR3864 is specific for ERG genomic fusions in prostate cancer: implications for pathological practice

Genomic rearrangements involving genes encoding erythroblast transformation-specific transcription factors are commonly present in prostate cancer. The TMPRSS2–ERG gene fusion that leads to ERG overexpression occurs in ∼70% of prostate cancers. Implementation of fusion gene detection in pathological practice, however, has been hampered by the lack of reliable ERG antibodies. The objective of this study was first to compare ERG immunohistochemistry using the recently described antibody EPR3864 with ERG mRNA by quantitative PCR and, second, to investigate ERG immunohistochemistry in diagnostic prostate cancer needle biopsies. We analyzed 41 primary prostate adenocarcinomas obtained by radical prostatectomy and 83 consecutive prostate cancer needle biopsies. In the prostatectomy specimens, immunohistochemical ERG expression was highly concordant with the ERG mRNA overexpression (sensitivity 100% and specificity 85%). ERG overexpression was due to TMPRSS2–ERG gene fusion in all cases. ERG protein expression was identified in 51/83 adenocarcinomas (61%) on needle biopsies. ERG expression was more frequent in tumors infiltrating ≥2 needle biopsies (P<0.001) or occupying ≥50% of a single biopsy (P=0.018). Expression of ERG also occurred in 11/21 (52%) high-grade prostate intraepithelial neoplasia lesions. In 5/87 (6%) needle biopsies containing benign secretory glands, weak ERG staining was focally observed. In all of these cases, respective glands were adjacent to adenocarcinomas. In conclusion, immunohistochemistry for ERG strongly correlated with ERG mRNA overexpression and was specific for prostate cancer on needle biopsies. Therefore, ERG immunohistochemistry is an important adjunctive tool for pathophysiological studies on ERG gene fusions, and might support the pathological diagnosis of adenocarcinoma in a subset of prostate needle biopsies.

Proteomic Profiling of Exosomes Leads to the Identification of Novel Biomarkers for Prostate Cancer

Background Current markers for prostate cancer, such as PSA lack specificity. Therefore, novel biomarkers are needed. Unfortunately, the complexity of body fluids often hampers biomarker discovery. An attractive alternative approach is the isolation of small vesicles, i.e. exosomes, ∼100 nm, which contain proteins that are specific to the tissue from which they are derived and therefore can be considered as treasure chests for disease-specific biomarker discovery. Materials and Methods Exosomes were isolated from 2 immortalized primary prostate epithelial cells (PNT2C2 and RWPE-1) and 2 PCa cell lines (PC346C and VCaP) by ultracentrifugation. After tryptic digestion, proteomic analyses utilized a nanoLC coupled with an LTQ-Orbitrap operated in tandem MS (MS/MS) mode. Accurate Mass and Time (AMT) tag approach was employed for peptide identification and quantitation. Candidate biomarkers were validated by Western blotting and Immunohistochemistry. Results Proteomic characterization resulted in the identification of 248, 233, 169, and 216 proteins by at least 2 peptides in exosomes from PNT2C2, RWPE-1, PC346C, and VCaP, respectively. Statistical analyses revealed 52 proteins differently abundant between PCa and control cells, 9 of which were more abundant in PCa. Validation by Western blotting confirmed a higher abundance of FASN, XPO1 and PDCD6IP (ALIX) in PCa exosomes. Conclusions Identification of exosomal proteins using high performance LC-FTMS resulted in the discovery of PDCD6IP, FASN, XPO1 and ENO1 as new candidate biomarkers for prostate cancer.

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

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

The role of HOXC6 in prostate cancer development

Homeobox (HOX) genes, which are involved in organ development and homeostasis, have been shown to be involved in normal prostate‐ and PCa development. In this study, we investigate the expression levels of the HOX A–D genes in PCa. The functional relevance and potential of HOX gene as biomarkers are explored.

MET expression during prostate cancer progression

Tyrosine-kinase inhibitors of the hepatocyte growth factor receptor MET are under investigation for the treatment of hormone-refractory prostate cancer (HRPC) metastasis. Analysis of MET protein expression and genetic alterations might contribute to therapeutic stratification of prostate cancer patients. Our objective was to investigate MET on protein, DNA and RNA level in clinical prostate cancer at various stages of progression. Expression of MET was analyzed in hormone-naive primary prostate cancers (N=481), lymph node (N=40) and bone (N=8) metastases, as well as HRPC (N=54) and bone metastases (N=15). MET protein expression was analyzed by immunohistochemistry (D1C2 C-terminal antibody). MET mRNA levels and MET DNA copy numbers were determined by in situ hybridization. None of the hormone-naive primary prostate cancer or lymph node metastases demonstrated MET protein or mRNA expression. In contrast, MET protein was expressed in 12/52 (23%) evaluable HRPC resections. RNA in situ demonstrated cytoplasmic signals in 14/54 (26%) of the HRPC patients, and was associated with MET protein expression (p=0.025, χ2), in absence of MET amplification or polysomy. MET protein expression was present in 7/8 (88%) hormone-naive and 10/15 (67%) HRPC bone metastases, without association of HRPC (p=0.37; χ2), with MET polysomy in 8/13 (61%) evaluable cases. In conclusion, MET was almost exclusively expressed in HRPC and prostate cancer bone metastasis, but was not related to MET amplification or polysomy. Evaluation of MET status could be relevant for therapeutic stratification of late stage prostate cancer.

Gene-expression analysis of gleason grade 3 tumor glands embedded in low- and high-risk prostate cancer.

The Gleason score (GS) of prostate cancer on diagnostic biopsies is an important parameter for therapeutic decision-making. Biopsy GS under-estimates the actual GS at radical prostatectomy in a significant number of patients due to sampling artifact. The aim of this study was to identify markers that are differentially expressed in Gleason grade 3 (GG3) tumor glands embedded in GS 4 + 3 = 7 and GS 3 + 3 = 6 prostate cancer using laser capture microdissection and RNA sequencing. GG3 tumor glands embedded in nine GS 3 + 3 = 6 and nine GS 4 + 3 = 7 prostate cancers were isolated by laser capture microdissection of frozen radical prostatectomy specimens. After RNA amplification and RNA sequencing, differentially expressed genes in both GG3 components were identified by a 2log fold change > 1.0 and p-value < 0.05. We applied immunohistochemistry on a tissue micro-array representing 481 radical prostatectomy samples for further validation on protein level. A total of 501 genes were up-regulated and 421 down-regulated in GG3 glands embedded in GS 4 + 3 = 7 as compared to GS 3 + 3 = 6 prostate cancer. We selected HELLS, ZIC2 and ZIC5 genes for further validation. ZIC5 mRNA was up-regulated 17 fold (p = 8.4E–07), ZIC2 8 fold (p = 1.3E–05) and HELLS 2 fold (p = 0.006) in GG3 glands derived from GS 4 + 3 = 7. HELLS expression of ≥ 1% occurred in 10% GS < 7, 17% GS 7 and 43% GS >7 prostate cancer (p < 0.001). Using a cut-off of ≥ 1%, protein expression of ZIC5 was present in 28% GS < 7, 43% GS 7 and 57% GS > 7 cancer (p < 0.001). ZIC2 was neither associated with GS nor outcome in our validation set. HELLS was independently predictive for biochemical-recurrence after radical prostatectomy (HR 2.3; CI 1.5–3.6; p < 0.01). In conclusion, HELLS and ZIC5 might be promising candidate markers for selection of biopsy GS 6 prostate cancer being at risk for up-grading at prostatectomy.