Co-staining of microRNAs and their target proteins by miRNA in situ hybridization and immunohistofluorescence on prostate cancer tissue microarrays.

The co-expression of miRNAs and their target proteins was studied on tissue microarrays from different prostate cancer (PCa) patients. PCa of primary Gleason pattern 4 (GP4), lymph node metastases of GP4, distant metastases, and normal tissue from the transitional and peripheral zones were co-stained by fluorescent miRNA in situ hybridization (miRisH) and protein immunohistofluorescence (IHF). The miRNAs and corresponding target proteins include the pairs miR-145/ERG, miR-143/uPAR, and miR-375/SEC23A. The fluorescence-stained and scanned tissue microarrays (TMAs) were evaluated by experienced uropathologists. The pair miR-145/ERG showed an exclusive staining for miR-145 in the nuclei of stromal cells, both in tumor and normal tissue, and for ERG in the cytoplasm with/without co-expression in the nucleus of tumor cells. The pair miR-143/uPAR revealed a clear distinction between miR-143 in the nuclei of stromal cells and uPAR staining in the cytoplasm of tumor cells. Metastases (lymph node and distant) however, showed tumor cells with cytoplasmic staining for miR-143/uPAR. In normal tissues, beside the nuclei of the stroma cells, gland cells could also express miR-143 and uPAR in the cytoplasm. miR-375 showed particular staining in the nucleoli of GP4 and metastatic samples, suggesting that nucleoli play a special role in sequestering proteins and miRNAs. Combined miRisH/IHF allows for the study of miRNA expression patterns and their target proteins at the single-cell level.

Ets-1 controls breast cancer cell balance between invasion and growth.

Ets-1 overexpression in human breast cancers is associated with invasiveness and poor prognosis. By overexpressing Ets-1 or a dominant negative mutant in MMT breast cancer cells, we previously highlighted the key role of Ets-1 in coordinating multiple invasive features of these cells. Interestingly, we also noticed that Ets-1 decreased the density of breast cancer cells cultured in three-dimensional extracellular matrix gels. The 3D context was instrumental to this phenomenon, as such downregulation was not observed in cells grown on two-dimensional plastic or matrix-coated dishes. Ets-1 overexpression was deleterious to anchorage-independent growth of MMT cells in soft agar, a standard model for in vitro tumorigenicity. The relevance of this mechanism was confirmed in vivo, during primary tumor growth and in a metastatic assay of lung colonization. In these models, Ets-1 was associated with epithelial-to-mesenchymal transition features and modulated the ratio of Ki67-positive cells, while hardly affecting in vivo apoptotic cell death. Finally, siRNA-mediated knockdown of Ets-1 in human breast cancer cell lines also decreased colony growth, both in anchorage-independent assays and 3D extracellular matrix cultures. These in vitro and in vivo observations shed light on an unsuspected facet of Ets-1 in breast tumorigenesis. They show that while promoting malignancy through the acquisition of invasive features, Ets-1 also attenuates breast tumor cell growth and could therefore repress the growth of primary tumors and metastases. This work also demonstrates that 3D models may reveal mechanisms of tumor biology that are cryptic in standard 2D models.

MED15, encoding a subunit of the mediator complex, is overexpressed at high frequency in castration-resistant prostate cancer.

The mediator complex is an evolutionary conserved key regulator of transcription of protein-coding genes and an integrative hub for diverse signaling pathways. In this study, we investigated whether the mediator subunit MED15 is implicated in castration-resistant prostate cancer (CRPC). MED15 expression and copy number/rearrangement status were assessed by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH), respectively on 718 prostate cancer (PCa) specimens and sequenced by Sanger on a subset. Furthermore, SMAD3 phosphorylation, androgen receptor (AR) and proliferation markers were evaluated by IHC. In PCa cells, siRNA/shRNA knockdown of MED15 was followed by proliferation assays with/without dihydrotestosterone (DHT), and treatments with recombinant TGF-ß3. Our results show that MED15 is overexpressed in 76% of distant metastatic CRPC (CRPC(MET) ) and 70% of local-recurrent CRPC (CRPC(LOC) ), in contrast to low frequencies in androgen-sensitive PCa, and no expression in benign prostatic tissue. Furthermore, MED15 overexpression correlates with worse clinical outcome thus defining a highly lethal phenotype. Moreover, TGF-ß signaling activation associates with MED15 overexpression in PCa tissues, and leads to increased expression of MED15 in PCa cells. MED15 knockdown effects phosphorylation and shuttling of p-SMAD3 to the nucleus as well as TGF-ß-enhanced proliferation. In PCa tissues, MED15 overexpression associates with AR overexpression/amplification and correlates with high proliferative activity. MED15 knockdown decreases both androgen-dependent and -independent proliferation in PCa cells. Taken together, these findings implicate MED15 in CRPC, and as MED15 is evolutionary conserved, it is likely to emerge as a lethal phenotype in other therapeutic-resistant diseases, and not restricted to our disease model.

Prognostic significance of phospho-histone H3 in prostate carcinoma.

PURPOSE: Prostate cancer is the second most common cancer in men and the sixth most common cause of death from cancer in men worldwide. Currently, a sufficient pathological distinction between patients requiring further treatment and those for which active surveillance remains an option is still lacking, which leads to the problem of overtreatment. Cell proliferation is routinely assessed by detecting Ki-67 antigen. While Ki-67 is expressed throughout the interphase of proliferating cells, phosphorylation of the chromatin constituent histone H3 occurs only during the late G2 phase and mitosis thus providing a more strict assessment of the mitotic activity. We undertook this study to test whether expression of the recently introduced proliferation marker phospho-histone H3 (pHH3) in prostate carcinoma tissue sections exhibits prognostic significance in comparison with Ki-67. METHODS: Protein expression of pHH3 and Ki-67 was assessed on TMA consisting of paraffin-embedded tissue from men that had undergone radical prostatectomy. The analysis included triplicate tissue cores of a total of 339 tumor foci. Immunohistochemical staining of pHH3 and Ki-67 was performed and analyzed using Definiens imaging software. RESULTS: Prostate cancer tissue exhibited a significantly higher frequency of pHH3-positive cells compared to benign prostate tissue. pHH3 expression was significantly correlated with Ki-67 expression. Furthermore, statistical analysis revealed positive correlation between pHH3 expression and PSA levels at diagnosis and in addition negatively correlated with overall survival. In contrast to Ki-67 staining, pHH3 expression did not correlate with Gleason grade. CONCLUSION: Our data point to a conceivable role of pHH3 as prognostic biomarker in prostate carcinoma.

Somatic copy number alterations by whole-exome sequencing implicates YWHAZ and PTK2 in castration-resistant prostate cancer.

Castration-resistant prostate cancer (CRPC) is the most aggressive form of prostate cancer (PCa) and remains a significant therapeutic challenge. The key to the development of novel therapeutic targets for CRPC is to decipher the molecular alterations underlying this lethal disease. The aim of our study was to identify therapeutic targets for CRPC by assessing somatic copy number alterations (SCNAs) by whole-exome sequencing on five CRPC/normal paired formalin-fixed paraffin-embedded (FFPE) samples, using the SOLiD4 next-generation sequencing (NGS) platform. Data were validated using fluorescence in situ hybridization (FISH) on a PCa progression cohort. PTK2 and YWHAZ amplification, mRNA and protein expression were determined in selected PCa cell lines. Effects of PTK2 inhibition using TAE226 inhibitor and YWHAZ knock-down on cell proliferation and migration were tested in PC3 cells in vitro. In a larger validation cohort, the amplification frequency of YWHAZ was 3% in localized PCa and 48% in CRPC, whereas PTK2 was amplified in 1% of localized PCa and 35% in CRPC. YWHAZ knock-down and PTK2 inhibition significantly affected cell proliferation and migration in the PC3 cells. Our findings suggest that inhibition of YWHAZ and PTK2 could delay the progression of the disease in CRPC patients harbouring amplification of the latter genes. Furthermore, our validated whole-exome sequencing data show that FFPE tissue could be a promising alternative for SCNA screening using next-generation sequencing technologies.

Loss of SLC45A3 protein (prostein) expression in prostate cancer is associated with SLC45A3-ERG gene rearrangement and an unfavorable clinical course.

The majority of prostate cancer harbors recurrent gene fusions involving ETS transcription factors, most commonly ERG. The second most common 5' fusion partner after TMPRSS2 is SLC45A3. The aim of our study was to quantify the protein expression of ERG, TMPRSS2 and SLC45A3 in prostate cancer to assess for diagnostic or prognostic utility. Six hundred and forty consecutive prostate cancer cases in tissue microarray format were immunohistochemically analyzed for ERG, TMPRSS2 and SLC45A3 protein. Resultant protein expression data was correlated to the respective gene rearrangement status and clinico-pathological parameters including PSA follow up times. ERG showed no expression in benign prostate glands. In cancer tissue, ERG protein expression showed a high rate of concordance with an underlying ERG rearrangement (91.5%). SLC45A3 showed a weaker expression in cancer as compared to benign tissue, which was pronounced in cases with SLC45A3-ERG fusion. Importantly, SLC45A3 down regulation was significantly associated with shorter PSA-free survival times. In contrast, TMPRSS2 was neither differentially expressed nor did it show a correlation between protein expression and rearrangement status. This study provides first evidence that the expression of SLC45A3 protein is down regulated through SLC45A3-ERG fusion in prostate cancer. Moreover, these cases may represent a distinct molecular subclass of ERG rearranged prostate cancer with distinct clinical features. This study also confirms that ERG protein expression is predominantly found in prostate carcinomas with ERG gene rearrangement and does not occur in benign glands.

Comparison of p40 (ΔNp63) and p63 expression in prostate tissues--which one is the superior diagnostic marker for basal cells?

AIMS: p63 is one of the standard markers for basal cells of the prostate gland. Recently, it has been suggested that the p63 isoform p40 might be more specific as a basal cell marker. In this study we compare the staining characteristics of p63 and p40 in normal and malignant prostate tissues. METHODS AND RESULTS: A prostatectomy cohort (n = 640) in tissue microarray format was evaluated for p63 (clone 4A4) and for p40 (rabbit polyclonal) immunoreactivity in malignant and normal tissues. Immunoreactivity of basal and secretory cells was evaluated in a semiquantitative manner and compared case-wise. In normal tissues, p40 showed highly similar immunoreactivity compared to p63. The staining patterns were absolutely identical in 88% of cases. Additional cytoplasmic p40 staining in tumour cells occurred in 59.6% of cancer cases. Differences were seen in nuclear staining of carcinomas: 1.4% of carcinomas were p63-positive, whereas 0.6% were p40-positive. CONCLUSIONS: In most cases, p40 stains prostatic basal cells as reliably as p63, with only minor differences. Aberrant staining of tumour cells is seen more rarely than with p63 (clone 4A4), establishing its higher specificity. However, additional cytoplasmic immunoreactivity narrows its eligibility for antibody cocktails (e.g. with alpha-methylacyl-CoA racemase).

Landscape of chromosome number changes in prostate cancer progression.

PURPOSE: Both genetic instability resulting in aneuploidy and increased proliferative activity are common features of tumor development and progression. Cytometric evaluation of tumor ploidy status was recently suggested as a prognostic marker. However, in prostate cancer (PCa), a chromosome-specific evaluation is lacking. With the present study, we sought to identify distinct chromosomal changes to complement cytometric results concerning the diagnosis and prognosis of PCa patients. METHODS: We assessed a cohort of 428 PCa specimens (186 localized PCa, 75 lymph node metastasized PCa, 125 lymph node metastases, 42 hormone-refractory distant metastases) for numerical alterations of all 24 chromosomes by using fluorescence in situ hybridization (FISH). Conducting immunohistochemistry with phosphorylated histone H3 (PHH3) and Ki-67, we quantified the proliferation rate. FISH results were fit in a linear model and tested for predictive power. RESULTS: As expected, we observed a significant increase in aneuploidy with advancing tumor stage. Similarly, an increased expression of the mitotic marker PHH3 was significantly associated with aneuploidy and higher pT-stage. We found aneusomy of chromosomes 4, 6, 20, and X to be indicative of lymph node metastasized PCa. However, with an AUC of 65%, this set of chromosomal changes was poorly suited to distinguish non-metastasized and lymph node metastasized primary tumors. CONCLUSION: Our results provide thorough insight into the so far incompletely elucidated chromosomal landscape of PCa. While overall ploidy status and PHH3 expression in primary tumors indicate advanced disease, a FISH-based test for distinct alterations does not seem to be beneficial for diagnostic or prognostic decisions.

Significance of Gleason grading of low-grade carcinoma of the prostate with therapeutic option of active surveillance.

INTRODUCTION: Active surveillance needs a precise grading diagnosis of a low-grade carcinoma of the prostate (Gleason score (GS) 6) within a small organ-confined tumor. However, how accurate is the gold standard of GS 6 in predicting a small pT2 carcinoma? To answer this question, we have analyzed grading systems in this study. METHODS: Prostatic carcinomas in biopsy and corresponding radical prostatectomy (RP) specimens of 960 patients were graded by the Gleason system in which glandular fusions and nucleolar stage (prominence and location) were considered. RESULTS: Using the modified Gleason grading, a high upgrading rate from the biopsy to RP specimens (GS 6-7) and in even 30% a non-organ-confined growth pattern (pT3) of GS 6 carcinoma in RP was found. When considering glandular fusion and the incorporation of the state of nucleoli within the Gleason grading, the agreement of score 6 between biopsy and RP specimens as well as the prediction of a pT2a tumor increased from about 80 to 90%. CONCLUSION: The combination of Gleason grading and grading of the nuclear and nucleolar features may help to identify patients eligible for active surveillance.

Classifying prostate cancer malignancy by quantitative histomorphometry.

PURPOSE: Prostate cancer is routinely graded according to the Gleason grading scheme. This scheme is predominantly based on the textural appearance of aberrant glandular structures. Gleason grade is difficult to standardize and often leads to discussion due to interrater and intrarater disagreement. Thus, we investigated whether digital image based automated quantitative histomorphometry could be used to achieve a more standardized, reproducible classification outcome. MATERIALS AND METHODS: In a proof of principle study we developed a method to evaluate digitized histological images of single prostate cancer regions in hematoxylin and eosin stained sections. Preprocessed color images were subjected to color deconvolution, followed by the binarization of obtained hematoxylin related image channels. Highlighted neoplastic epithelial gland related objects were morphometrically assessed by a classifier based on 2 calculated quantitative and objective geometric measures, that is inverse solidity and inverse compactness. The procedure was then applied to the prostate cancer probes of 125 patients. Each probe was independently classified for Gleason grade 3, 4 or 5 by an experienced pathologist blinded to image analysis outcome. RESULTS: Together inverse compactness and inverse solidity were adequate discriminatory features for a powerful classifier that distinguished Gleason grade 3 from grade 4/5 histology. The classifier was robust on sensitivity analysis. CONCLUSIONS: Results suggest that quantitative and interpretable measures can be obtained from image based analysis, permitting algorithmic differentiation of prostate Gleason grades. The method must be validated in a large independent series of specimens.