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. Mol Cancer Res; 8(4); 529–38. ©2010 AACR.

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 miRNAin situhybridization. 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 miRNAsmiR‐375,miR‐143andmiR‐145was validated by quantitative PCR. MiRNAin situhybridization 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.

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. Mol Cancer Res; 9(6); 791–800. ©2011 AACR.

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.

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. Mol Cancer Res; 12(2); 250–63. ©2013 AACR.