MicroRNA expression profiles in the progression of prostate cancer--from high-grade prostate intraepithelial neoplasia to metastasis.

INTRODUCTION: Models of the multistep process related to cancer progression have been designed for many cancers including prostate. The aim of this study is to propose a new model including a possible role for recently described micro RNAs in prostate cancer (CaP) progression. METHODS: Sixty-three patients underwent radical prostatectomy to treat localized prostate carcinoma. The specimens of 15 patients were representative of high grade prostate intraepithelial neoplasia (HGPIN). Fourteen specimens represented localized favorable CaP, and 34 unfavorable, mostly non-organ-confined disease. Representing the advanced disease we studied 4 metastatic androgen-independent CaP and 2 cell lines. Micro RNAs were isolated using the mirVana miRNA Isolation kit and cDNA was obtained using the TaqMan miRNA Reverse Transcription kit to the miRNAs: hsa-miR-let7c, hsa-miR-15a, hsa-miR-16, hsa-miR-21, hsa-miR-25, hsa-miR-32, hsa-miR-100, hsa-miR-143, hsa-miR-145, hsa-miR-146a, hsa-miR-191, hsa-miR-199a, hsa-miR-206, and hsa-miR-218. Quantitative RT-PCR was carried out using the ABI 7500 Fast Real-Time PCR System and the TaqMan Universal PCR Master Mix. miRNA expression levels were measured by relative quantification, and fold expression changes were determined by the 2(-ΔΔCT) method. The small nucleolar RNA RNU43 was used as an endogenous control. RESULTS: Except for miR-21 and miR-206, the expression levels of all miRNAs significantly changed during the progression of CaP. Interestingly, there was a significant global loss of miRNA expression between HGPIN and metastasis at 2 important steps. The first was related to the transition from HGPIN to invasive adenocarcinoma, and the second was related to the transition from localized to metastatic adenocarcinomas. CONCLUSION: Through the analysis of 14 miRNAs in 4 groups of prostate lesions, which reproduced the progression of CaP, we showed that there is a global loss of miRNA expression at 2 distinct steps. The first related to the transition between HGPIN and localized invasive carcinoma, and the second associated with the transition from localized to metastatic CaP. The importance of our study is in the identification of possible miRNAs and miRNA-targeted genes involved in the progression of prostate carcinogenesis that may help the development of potential diagnostic or prognostic markers as well as the design of new target therapies.

MicroRNA-100 expression is independently related to biochemical recurrence of prostate cancer.

PURPOSE: Abnormal miRNA expression has emerged as crucial factors in carcinogenesis and is important in the comprehension of prostate cancer behavior. We determined the correlation of miRNA expression profiles with prostate cancer progression. MATERIALS AND METHODS: We studied frozen specimens from 49 patients treated for prostate cancer with radical prostatectomy. We intentionally chose 28 men without and 21 with biochemical recurrence, defined as prostate specific antigen greater than 0.2 ng/ml. The expression of 14 miRNAs was determined by quantitative reverse transcriptase-polymerase chain reaction. All radical prostatectomy specimens were studied in toto to determine tumor volume, Gleason score and 2002 TNM pathological stage. Benign prostate tissue from benign prostatic hyperplasia served as a control. RESULTS: Four miRNAs were related to tumor recurrence. Using the Cox regression test the risk of recurrence was 3.0, 3.3, 2.7 and 3.4 for high levels of miR-100, miR-145, miR-191 and miR-let7c, respectively. When considering statistically significant clinical variables on univariate analysis of biochemical-free survival, prostate specific antigen and tumor volume, results revealed that miR-100 and tumor volume were independently related to tumor recurrence. CONCLUSIONS: A high level of miR-100 is related to biochemical recurrence of localized prostate cancer in patients treated with radical prostatectomy. The role of miR-100 during carcinogenesis must be resolved in future studies to better understand the molecular pathways in which miR-100 is involved. This may open the possibility of using it as a prognostic marker and inspire the development of a target drug.

Change in expression of miR-let7c, miR-100, and miR-218 from high grade localized prostate cancer to metastasis.

OBJECTIVE: MicroRNAs (miRNAs) are small noncoding regulatory RNAs (19-25 nucleotides) that play a major role in regulation of gene expression. They are responsible for the control of fundamental cellular processes that has been reported to be involved in human tumorigenesis. The characterization of miRNA profiles in human tumors is crucial for the understanding of carcinogenesis processes, finding of new tumor markers, and discovering of specific targets for the development of innovative therapies. The aim of this study is to find miRNAs involved in prostate cancer progression comparing the profile of miRNA expressed by localized high grade carcinoma and bone metastasis. MATERIAL AND METHODS: Two groups of tumors where submitted to analyses. The first is characterized by 18 patients who underwent radical prostatectomy for treatment of localized high grade prostate carcinoma (PC) with mean Gleason score 8.6, all staged pT3. The second group is composed of 4 patients with metastatic, androgen-independent prostate carcinoma, and 2 PC cell lines. LNCaP derived from a metastatic PC to a lymph node, and another derived from an obstructive, androgen-independent PC (PcBRA1). Expression analysis of 14 miRNAs was carried out using quantitative RT-PCR. RESULTS: miR-let7c, miR-100, and miR-218 were significantly overexpressed by all localized high GS, pT3 PC in comparison with metastatic carcinoma. (35.065 vs. 0.996 P<0.001), (55.550 vs. 8.314, P=0.010), and (33.549 vs. 2.748, P=0.001), respectively. CONCLUSION: We hypothesize that miR-let7c, miR-100, and miR-218 may be involved in the process of metastasization of PC, and their role as controllers of the expression of RAS, c-myc, Laminin 5 ß3, THAP2, SMARCA5, and BAZ2A should be matter of additional studies.

miRNA analysis of prostate cancer by quantitative real time PCR: comparison between formalin-fixed paraffin embedded and fresh-frozen tissue.

OBJECTIVE: Micro RNA (miRNA) is a class of small noncoding RNA that plays a major role in the regulation of gene expression, which has been related to cancer behavior. The possibility of analyzing miRNA from the archives of pathology laboratories is exciting, as it allows for large retrospective studies. Formalin is the most common fixative used in the surgical pathology routine, and its promotion of nucleic acid degradation is well known. Our aim is to compare miRNA profiles from formalin-fixed paraffin embedded (FFPE) tissues with fresh-frozen prostate cancer tissues. METHODS: The expression of 14 miRNAs was determined by quantitative real time polymerase chain reaction (qRT-PCR) in 5 paired fresh-frozen and FFPE tissues, which were representative of prostate carcinoma. RESULTS: There was a very good correlation of the miRNA expression of miR-let7c and miR-32 between the fresh-frozen and FFPE tissues, with Pearson's correlation coefficients of 0.927 (P = 0.023) and 0.960 (P = 0.010), respectively. For the remaining miRNAs, the correlation was good with Spearman correlation coefficient of 0.638 (P < 0.001). CONCLUSION: Analysis of miRNAs from routinely processed and stored FFPE prostate tissue is feasible for some miRNAs using qRT-PCR. Further studies should be conducted to confirm the reliability of using stock tissues for miRNA expression determination.