Analysis of Argonaute Complex Bound mRNAs in DU145 Prostate Carcinoma Cells Reveals New miRNA Target Genes.

Posttranscriptional gene regulation by microRNAs (miRNAs) contributes to the induction and maintenance of prostate carcinoma (PCa). To identify mRNAs enriched or removed from Ago2-containing RISC complexes, these complexes were immunoprecipitated from normal prostate fibroblasts (PNFs) and the PCa line DU145 and the bound mRNAs were quantified by microarray. The analysis of Ago complexes derived from PNFs or DU145 confirmed the enrichment or depletion of a variety of mRNAs already known from the literature to be deregulated. Novel potential targets were analyzed by luciferase assays with miRNAs known to be deregulated in PCa. We demonstrate that the mRNAs of the death effector domain-containing protein (DEDD), the tumor necrosis factor receptor superfamily, member 10b protein (TNFRSF10B), the tumor protein p53 inducible nuclear protein 1 (TP53INP1), and the secreted protein, acidic, cysteine-rich (SPARC; osteonectin) are regulated by miRNAs miR-148a, miR-20a, miR-24, and miR-29a/b, respectively. Therefore, these miRNAs represent potential targets for therapy. Surprisingly, overexpression of miR-24 induced focus formation and proliferation of DU145 cells, while miR-29b reduced proliferation. The study confirms genes deregulated in PCa by virtue of their presence/absence in the Ago2-complex. In conjunction with the already published miRNA profiles of PCa, the data can be used to identify miRNA-regulated mRNAs.

Neuroendocrine Cells of the Prostate Derive from the Neural Crest.

The histogenesis of prostatic neuroendocrine cells is controversial: a stem cell hypothesis with a urogenital sinus-derived progeny of all prostatic epithelial cells is opposed by a dual origin hypothesis, favoring the derivation of neuroendocrine cells from the neural crest, with the secretory and basal cells being of urogenital sinus origin. A computer-assisted 3D reconstruction was used to analyze the distribution of chromogranin A immunoreactive cells in serial sections of human fetal prostate specimens (gestation weeks 18 and 25). Immunohistochemical double labeling studies with YFP and serotonin antisera combined with electron microscopy were carried out on double-transgenic Wnt1-Cre/ROSA26-YFP mice showing stable YFP expression in all neural crest-derived cell populations despite loss of Wnt1 expression. 3D reconstruction of the distribution pattern of neuroendocrine cells in the human fetal prostate indicates a migration of paraganglionic cells passing the stroma and reaching the prostate ducts. Double-transgenic mice showed 55% double labeling of periurethral neuroendocrine cells expressing both serotonin and YFP, whereas single serotonin labeling was observed in 36% and exclusive YFP labeling in 9%. The results favor the assumption of a major fraction of neural crest-derived neuroendocrine cells in both the human and murine prostates.

Normal Fertility Requires the Expression of Carbonic Anhydrases II and IV in Sperm.

HCO3 (-) is a key factor in the regulation of sperm motility. High concentrations of HCO3 (-) in the female genital tract induce an increase in sperm beat frequency, which speeds progress of the sperm through the female reproductive tract. Carbonic anhydrases (CA), which catalyze the reversible hydration of CO2 to HCO3 (-), represent potential candidates in the regulation of the HCO3 (-) homeostasis in sperm and the composition of the male and female genital tract fluids. We show that two CA isoforms, CAII and CAIV, are distributed along the epididymal epithelium and appear with the onset of puberty. Expression analyses reveal an up-regulation of CAII and CAIV in the different epididymal sections of the knockout lines. In sperm, we find that CAII is located in the principal piece, whereas CAIV is present in the plasma membrane of the entire sperm tail. CAII and CAIV single knockout animals display an imbalanced HCO3 (-) homeostasis, resulting in substantially reduced sperm motility, swimming speed, and HCO3 (-)-enhanced beat frequency. The CA activity remaining in the sperm of CAII- and CAIV-null mutants is 35% and 68% of that found in WT mice. Sperm of the double knockout mutant mice show responses to stimulus by HCO3 (-) or CO2 that were delayed in onset and reduced in magnitude. In comparison with sperm from CAII and CAIV double knockout animals, pharmacological loss of CAIV in sperm from CAII knockout animals, show an even lower response to HCO3 (-). These results suggest that CAII and CAIV are required for optimal fertilization.

Comparative microRNA profiling of prostate carcinomas with increasing tumor stage by deep sequencing.

UNLABELLED: MicroRNAs (miRNA) posttranscriptionally regulate gene expression and are important in tumorigenesis. Previous deep sequencing identified the miRNA profile of prostate carcinoma versus nonmalignant prostate tissue. Here, we generated miRNA expression profiles of prostate carcinoma by deep sequencing, with increasing tumor stage relative to corresponding nonmalignant and healthy prostate tissue, and detected clearly changed miRNA expression patterns. The miRNA profiles of the healthy and nonmalignant tissues were consistent with our previous findings, indicating a high fidelity of the method employed. In the tumors, quantitative real-time PCR (qRT-PCR) analysis of 40 paired samples of prostate carcinoma versus normal tissue revealed significant upregulation of miR-20a, miR-148a, miR-200b, and miR-375 and downregulation of miR-143 and miR-145. Hereby, miR-375 increased from normal to organ-confined tumors (pT2 pN0), slightly decreased in tumors with extracapsular growth (pT3 pN0), but was then expressed again at higher levels in lymph node metastasizing (pN1) tumors. The sequencing data for miR-375 were confirmed by Northern blotting and qRT-PCR. The regulation for other selected miRNAs could, however, not be confirmed by qRT-PCR in individual tumor stages. MiR-200b, in addition to miR-200c and miR-375 reduced the expression of SEC23A. Interestingly, miR-375, found by sequencing in pT2 upregulated by us and others in tumor versus normal tissue, and miR-15a, found by sequencing in pT2 and pT3 and in the metastasizing tumors, target the phosphatases PHLPP1 and PHLPP2, respectively. PHLPP1 and PHLPP2 dephosphorylate members of the AKT family of signal transducers, thereby inhibiting cell growth. Coexpression of miR-15a and miR-375 resulted in downregulation of PHLPP1/2 and strongly increased prostate carcinoma cell growth. IMPLICATIONS: These genomic data reveal relevant miRNAs in prostate cancer that may have biomarker and therapeutic potential.

The proto-oncogene ERG is a target of microRNA miR-145 in prostate cancer.

Prostate cancer is a leading cause of cancer mortality in men. One of the distinct characteristics of prostate cancer is over-expression of the ERG proto-oncogene. The TMPRSS2-ERG gene fusion, the most common gene fusion, is found in approximately 50% of prostate cancer cases. We show that certain microRNAs are extensively deregulated in prostate cancer cell lines and primary clinical cancer samples. MicroRNAs are capable of modulating post-transcriptional gene expression via inhibition of protein synthesis. Independent target prediction methods have indicated that the 3' untranslated region of the ERG mRNA is a potential target of miR-145. miR-145 is consistently down-regulated in prostate cancer. Here we show that the ERG 3' untranslated region is a regulative target of miR-145 in vitro. Ectopic expression of miR-145 led to a reduction in expression of the ERG protein. We analyzed 26 prostate cancer samples and corresponding normal tissue. ERG protein expression was found to be elevated in the tumor samples, together with increased expression of several ERG isoforms. We identified ERG proteins of 35 and 24 kDa, which may represent unknown ERG splice variants. Analyses of miR-145 and ERG mRNA expression revealed a general down-regulation of miR-145 irrespective of the presence or absence of translocations involving ERG. This observation indicates that down-regulation of miR-145 may contribute to the increased expression of most ERG splice variants sharing the miR-145 target sequence in their 3' untranslated region.

Identification of ZNF217, hnRNP-K, VEGF-A and IPO7 as targets for microRNAs that are downregulated in prostate carcinoma.

In primary prostate cancer (PCa), a major cause of cancer-related death in men, the expression of various microRNAs (miRNAs) is deregulated. We previously detected several miRNAs, for example, miR-24 and miR-22, as significantly downregulated in PCa (Szczyrba et al., Mol Cancer Res 2010;8:529-38). An in silico search predicted that zinc finger protein 217 (ZNF217) and importin 7 (IPO7) were potential target genes of these miRNAs. Additionally, for two genes that are deregulated in PCa (heterogeneous nuclear ribonucleoprotein K, hnRNP-K, and vascular endothelial growth factor A, VEGF-A), we identified two regulatory miRNAs, miR-205 and miR-29b. The regulation of the 3'-untranslated regions of the four genes by their respective miRNAs was confirmed by luciferase assays. As expected, the upregulation of ZNF217, hnRNP-K, VEGF-A and IPO7 could be verified at the protein level in the PCa cell lines LNCaP and DU145. ZNF217 and IPO7, which had not yet been studied in PCa, were analyzed in more detail. ZNF217 mRNA is overexpressed in primary PCa samples, and this overexpression translates to an elevated protein level. However, IPO7 was upregulated at the protein level alone. The inhibition of ZNF217 and IPO7 by siRNA resulted in reduced proliferation of the PCa cell lines. ZNF217 could thus be identified as an oncogene that is overexpressed in PCa and affects the growth of PCa cell lines, whereas the function of IPO7 remains to be elucidated in greater detail.

MicroRNA profiles of prostate carcinoma detected by multiplatform microRNA screening.

MicroRNAs (miRNAs) are small RNA molecules that regulate gene expression via posttranscriptional inhibition of protein synthesis. They play a vital role in tumorigenesis. To characterize the diagnostic potential of miRNAs in prostate cancer, a leading cause of cancer mortality, we performed screening of miRNA expression profiles. We used commercially available microarrays to establish miRNA expression profiles from a cohort of 20 cancer samples. The expression of selected miRNAs was analyzed by quantitative real-time PCR and the identity of miRNA expressing cells was determined by miRNA in situ hybridization. We identified 25 miRNAs that showed a significant differential expression in cancer samples. The comparison with previously published data generated by deep sequencing of cDNA libraries of small RNA molecules revealed a concordance rate of 47% among miRNAs identified with both techniques. The differential expression of miRNAs miR-375, miR-143 and miR-145 was validated by quantitative PCR. MiRNA in situ hybridization revealed that the differential expression is cancer-cell associated. A combination of three miRNAs correctly classified tissue samples with an accuracy of 77.6% with an area under the receiver-operator characteristic curve of 0.810. Our data extend the knowledge about the deregulation of miRNAs in prostate cancer. The differential expression of several miRNAs is highly consistent using independent cohorts of tumor samples, different tissue preservation methods and different experimental methods. Our results indicate that combinations of miRNAs are promising biomarkers for the diagnosis of prostate cancer.

Downregulation of Sec23A protein by miRNA-375 in prostate carcinoma.

Prostate carcinoma (CaP) is a leading cause of cancer-related death in men. We have previously determined the microRNA (miRNA) profile of primary CaP in comparison with nontumor prostate tissue. miRNAs are small, noncoding RNAs that inhibit protein synthesis on a posttranscriptional level by binding to the 3'-untranslated region (3'-UTR) of their target genes. In primary CaP tissue, we have previously found by miRNA sequencing that miR-375 and miR-200c were upregulated 9.1- and 4.5-fold, respectively. A computational analysis predicted the 3'-UTR of the SEC23A gene as a potential target for both miR-375 and miR-200c. Here, we show that the 3'-UTR of SEC23A mRNA is indeed a target for miR-375 and miR-200c and that both miRNAs downregulate Sec23A protein expression when ectopically expressed in human 293T cells. In primary samples of CaP, we found a direct correlation between reduction of SEC23A mRNA and overexpression of miR-375 but not of miR-200c. The reduced levels of Sec23A protein were inversely correlated to the increased amount of miR-375 in the LNCaP and DU145 CaP cell lines when compared with normal prostate fibroblasts. In primary CaP, we also detected decreased amounts of Sec23A protein when compared with corresponding normal prostate tissue. Ectopically overexpressed Sec23A in LNCaP and DU145 CaP cells significantly reduced the growth properties, indicating that Sec23A might play a role in the induction or growth of prostate carcinoma. Sec23A overexpression reduced cell growth but did not induce apoptosis, whereas inhibition of Sec23A stimulated cell proliferation.

The microRNA profile of prostate carcinoma obtained by deep sequencing.

Prostate cancer is a leading cause of tumor mortality. To characterize the underlying molecular mechanisms, we have compared the microRNA (miRNA) profile of primary prostate cancers and noncancer prostate tissues using deep sequencing. MiRNAs are small noncoding RNAs of 21 to 25 nucleotides that regulate gene expression through the inhibition of protein synthesis. We find that 33 miRNAs were upregulated or downregulated >1.5-fold. The deregulation of selected miRNAs was confirmed by both Northern blotting and quantitative reverse transcription-PCR in established prostate cancer cell lines and clinical tissue samples. A computational search indicated the 3'-untranslated region (UTR) of the mRNA for myosin VI (MYO6) as a potential target for both miR-143 and miR-145, the expression of which was reduced in the tumor tissues. Upregulation of myosin VI in prostate cancer was previously shown by immunohistochemistry. The level of MYO6 mRNA was significantly induced in all primary tumor tissues compared with the nontumor tissue from the same patient. This finding was matched to the upregulation of myosin VI in established prostate cancer cell lines. In luciferase reporter analysis, we find a significant negative regulatory effect on the MYO6 3'UTR by both miR-143 and miR-145. Mutation of the potential binding sites for miR-143 and miR-145 in the MYO6 3'UTR resulted in a loss of responsiveness to the corresponding miRNA. Our data indicate that miR-143 and miR-145 are involved in the regulation of MYO6 expression and possibly in the development of prostate cancer.