Prostate cancer is the most common male-specific form of cancer in the U.K. Current treatments for the aggressive disease by androgen-deprivation therapy gives a rapid initial response, but the disease ultimately progresses into an androgen-independent state for which there are no effective treatments. α-Methylacyl-CoA racemase (AMACR, P504S) is an enzyme which is involved in metabolism of branched-chain fatty acids and the pharmacological activation of some NSAID drugs, such as Ibuprofen and most other ‘profens’. AMACR is over-expressed in prostate cancer and some other cancers, including colon and breast cancers. Reduction of AMACR protein levels inhibits proliferation of prostate cancer cells and restores the requirement for androgens for growth. Although the exact role of AMACR in prostate cancer progression is currently unknown, several other experiments show that AMACR is functionally important for prostate cancer proliferation, validating it as a drug target. There is no convenient high-throughput assay for AMACR and as a result only a few inhibitors have been reported to date. This thesis reports a study on whether other reactions can be catalysed by AMACR. 2-Methyl-3-enoyl-CoA esters are good substrates of AMACR but do not undergo double bond migration, while 2-methyl-2-enoyl-CoA esters are not converted to products. Acyl-CoA esters that contain a fluorine atom at carbon-3 undergo a fluoride elimination reaction to give 2-methyl-2-enoyl-CoA esters. This elimination reaction was investigated for use in the development of a high-throughput assay. A fluorescent binding assay, which can be adapted for the screening of large libraries of compounds, was developed and several known and novel inhibitors were tested. Finally, metabolism of mandelic acid was investigated. It was shown that chiral inversion of mandelic acid in humans proceeds via a different pathway to Ibuprofen and related drugs, in contrast with previous reports.

Alpha-methyacyl-CoA racemase (AMACR) is a critical peroxisomal and mitochondrial enzyme, encodes a key enzyme in the catabolism of long-chain fatty acid thus is indispensable in the £]-oxidation of fatty acid to generate biological energy. AMACR stands in many organs with only very low expression level and its overexpression is exclusively in neoplastic conditions. Recently, AMACR overexpresison has been discerned to relevant to tumor progression of prostate, gastric, and colon cancers, and its overexpression has now been introduced in pathological differential diagnosis of prostate carcinoma from non-malignant mimickers. By using 89 gallbladder carcinoma (GBCA) samples for AMACR immunostaining we found AMACR overexpression is frequently discerned in GBCA. It not only significantly correlates with numerous adverse clinicopathologic factors but also manifests a significant independent predictor of worse outcome in GBCA patients. In multivariate comparison, higher tumor stage represented the strongest prognosticator (p = 0.0101), followed by old patient age (p = 0.0378). Moreover, AMACR overexpression also identified patients at around 2-fold higher risk of disease-specific death (p = 0.0452). By Western blot analyses, we found AMACR expression in the metastatic cells, RCB1129, was apparently more abundant than that in its primary lesion RCB1130. By XTT analyses, the viability of both RCB1129 and RCB1130 cells were significantly decreased by AMACR inhibitor. The RCB1129 cell line, with more abundant AMACR protein expression, was more resistant to AMACR inhibitor treatment than RCB1130 cell line at various drug concentrations. Our data suggest AMACR is a prognostic marker that can serve as a promising therapeutic target in gallbladder cancer.

Levels of the enzyme α-methylacyl-CoA racemase (AMACR) are increased ca. 9-fold in prostate cancer cells. AMACR is a very promising novel drug target as reducing AMACR levels converts castrate-resistant prostate cancer cells to androgen-dependent cells which will respond to androgen-deprivation. Despite the importance of AMACR in prostate and other cancers, there are very limited numbers of AMACR inhibitors described to-date. This is mainly due to the absence of a high-throughput assay for the screening of inhibitors against AMACR. The active-site residues and catalytic mechanism of human AMACR are still unknown, which make the rational design of drugs targeting AMACR very difficult. A range of novel potential inhibitors were synthesised using a rational drug design approach to explore the structure-activity relationship (SAR) on the side-chains of AMACR inhibitors. Their potencies were assessed using the fluoride elimination assay based on 1H and 19F NMR. Potency, mode of binding and kinetic parameters of these inhibitors were assessed using the multi-well colorimetric assay, which is the first AMACR high-throughput continuous assay reported to-date. A site-directed mutagenesis study was carried out to identify the active-site residues and catalytic mechanism of human AMACR. His-122, Asp-152, Met-184 and Glu-237 were identified as potential active-site residues, so the cDNA was mutated and expressed. The activity of wild-type and mutant AMACR enzymes were assessed using the deuterium wash-in, fluoride elimination and multi-well colorimetric assays. Results from these assays showed that human AMACR does not operate using a ‘two-base’ mechanism. Instead, it operates using a ‘one-base’ mechanism, most likely via water molecules acting as intermediaries within the hydrogen-bondings network in the active site. The knowledge obtained from this research informs rational drug design for this castrate-resistant prostate cancer target.

Orientador: Athanase Billis / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas / Made available in DSpace on 2018-11-07T16:10:17Z (GMT). No. of bitstreams: 1 Worschech_Adriana_M.pdf: 2136837 bytes, checksum: e169d43b81c649e3dde44c36f7a96278 (MD5) Previous issue date: 2008 / Resumo: A atrofia parcial (AP) é uma lesão benigna que mais freqüentemente imita adenocarcinoma, particularmente a variante parcial. AP ocorre com maior freqüência no lobo posterior ou zona periférica e ganhou importância maior com o uso das biópsias por agulha na detecção do carcinoma prostático. A atrofia parcial e a hiperplasia pós-atrófica (atrofia hiperplásica) são as lesões benignas que mais freqüentemente são confundidas com adenocarcinoma. Uma das razões que contribuem para dificultar o diagnóstico da atrofia parcial está relacionada com a ausência de células basais em alguns ácinos. Mais recentemente a aplicação da molécula de AMACR (alfa-metilacil Co-enzima A racemase) como marcador de células neoplásicas através de imunoistoquímica tem auxiliado no diagnóstico diferencial com o adenocarcinoma. Entretanto, sua aplicação na rotina diagnóstica ainda não está estabelecida. A imunoexpressão da AMACR pode causar algumas dúvidas em sua interpretação. Na literatura existem poucos estudos que relatam a expressão da AMACR em atrofia parcial. Avaliamos através da imunoistoquímica a expressão da AMACR e do 34ßE12 (citoqueratina de alto peso molecular) através do coquetel P504S+34ßE12 em material proveniente de 74 biópsias por agulha de próstata correspondendo a 61 pacientes. Foram analisados um total de 1198 ácinos prostáticos (324 ácinos com adenocarcinoma, 213 ácinos normais, 190 ácinos com atrofia parcial, 298 ácinos com hiperplasia pós-atrófica, 139 ácinos com atrofia simples e 34 ácinos com atrofia esclerosante). Nos ácinos com adenocarcinoma a intensidade da marcação da AMACR foi forte em 251/324 (77.5%) e fraca 73/324 (22.5%). Não houveram casos negativos. Nos ácinos normais observou-se marcação para a AMACR forte em 13/213 (6.1%), fraca em 33/213 (15.5%) e negativa em 167/213 (78.4%). A atrofia parcial apresentou marcação para a AMACR fraca em 47/190 (24.7%) e negativa em 143/190 (75.3%). Não houve marcação forte em nenhum dos casos de atrofia parcial. Os ácinos normais mostraram expressão para AMACR negativo, fraco e forte onde os valores foram respectivamente 167/213 (78,4%), 33/213 (15,5%) e 13/213 (6,1%). A atrofia parcial mostrou-se negativa, e fraca para imunoexpressão da AMACR em 143/190 (75,3%) e 47/190 (24,7%) respectivamente. Não foi observada forte positividade em atrofia parcial, no entanto, a fraca positividade observada em cerca de 25% dos ácinos pode causar dificuldade para a interpretação correta no diagnóstico diferencial de câncer e atrofia parcial. A AMACR foi negativa em todos os ácinos da atrofia simples, hiperplásica (ou hiperplasia pós-atrófica) e esclerosante, por conseguinte, sem qualquer ajuda no diagnóstico diferencial de adenocar-cinoma. A distribuição das células basais, observadas na atrofia simples, hiperplásica e esclerosante foram descontínuas e as células do compartimento secretor mostraram imunoexpressão aberrante de 34ßE12 sugerindo um fenótipo intermédio. Analisando-se os estes resultados conclui-se que o diagnóstico diferencial do adenocarcinoma com atrofia parcial deve ser feito com cautela considerando-se que a expressão da AMACR, apesar de fraca em nosso estudo, pode ocorrer em cerca de 25% dos ácinos. Soma-se a este achado o fato de que em 23.2% dos ácinos de atrofia parcial as células basais estão ausentes. Estes dados impõem cautela no difícil diagnóstico diferencial de pequenos focos "suspeitos, mas não diagnósticos de adenocarcinoma da próstata", sendo que, em alguns casos, os critérios puramente morfológicos poderão ser os únicos na identificação da lesão. / Abstract: Prostatic atrophy (PA) is the benign lesion that most frequently mimicks adenocarcinoma particularly the partial variant. PA occurs more frequently in the peripheral zone and gained greater importance with the use of needle biopsies in detecting cancer of the prostate. Partial atrophy and post-atrophic hyperplasia (hyperplastic atrophy) are the benign lesions that most often are confused with adenocarcinoma. One of the reasons that contribute to make the diagnosis of partial atrophy difficult is related to the absence of basal cell in some acini. More recently the application of AMACR (alpha-metilacil Co-enzyme A racemase) as a marker of malignant cells through immunohistochemistry has helped in the differential diagnosis with prostate cancer. However, its application in routine diagnosis is not yet established. The immunoexpression of AMACR may cause some doubt in interpretation. In literature there are few studies that reported the expression of AMACR in partial atrophy. We evaluated by immunohistochemistry the expression of AMACR and 34ßE12 (cytokeratin high-molecular weight) using the cocktail P504S +34ßE12 in 74 needle prostatic biopsies corresponding to 61 patients. We analyzed a total of 1198 prostate acini (324 acini with adenocarcinoma, 213 normal acini, 190 acini with partial atrophy, 298 acini with post-atrophic hyperplasia, 139 acini with simple atrophy and 34 acini with sclerosing atrophy). In adenocarcinoma acini the staining of AMACR was strong in 251/324 (77.5%) and weak in 73/324 (22.5%). There were no negative acini. In normal acini AMACR was strong in 13/213 (6.1%), weak in 33/213 (15.5%) and negative in 167/213 (78.4%). In partial atrophy, acini showed weak AMACR in 47/190 (24.7%) and were negative in 143/190 (75.3%). There was no strong staining in partial atrophy. The immunoexpression of AMACR was negative in all variants of complete atrophy: simple atrophy, hyperplastic atrophy and sclerosing atrophy. Normal acini showed negative, weak, or strong expression in 167/213 (78.4%), 33/213 (15.5%), and 13/213 (6.1%) acini, respectively. Partial atrophy showed negative, and weak expression in 143/190 (75.3%), and 47/190(24.7%) acini, respectively. No strong positivity was seen in partial atrophy, however, the weak positivity seen in approximately 25% of the acini may be a pitfall for the correct interpretation in the differential diagnosis of cancer and partial atrophy. AMACR was negative in all acini of simple, postatrophic hyperplasia and sclerosing atrophy, therefore, with no help in the differential diagnosis of adenocarcinoma. The distribution of basal cells in simple, postatrophic hyperplasia and sclerotic atrophy was discontinuous and the cells of the secretory compartment showed aberrant expression of 34ßE12 suggesting an intermediate phenotype. Analyzing these results it is concluded that the differential diagnosis of prostate cancer with partial atrophy must be done carefully considering that the expression of AMACR, although weak in our study, can occur in about 25% of the acini. Furthermore, in 23.2% acini of partial atrophy the basal cells are absent. In some cases the microscopic identification of partial atrophy will rely only on morphologic criteria. / Mestrado / Ciencias Biomedicas / Mestre em Ciências Médicas

Currently, many patients with early-stage localized prostate cancer (PrCa) (D’Amico: low risk or low-intermediate risk) do not receive immediate therapy but are monitored within systematic AS programs. Prospective trials showed rates of stage reclassification and progression to the treatment of 20–40% over 2–5 years. However, in certain patients, PrCa progresses rapidly to an advanced stage that requires combined modality therapies, which carry increased risk for toxicity and poor outcomes. There is a need to identify biomarkers that can predict the risk for disease progression in this population. Research showed that dysregulation of metabolism is an important hallmark of cancer progression. Here, we pursued a pilot investigation of enzymes of de novo lipogenesis [ATP-citrate lyase (ACLY), Acetyl-CoA Carboxylase (ACC)], lipid oxidation [a-Methylacyl-CoA Racemase (AMACR)], glucose uptake [facilitative glucose transporter 1 (GLUT1)], and folate – glutamate metabolism (PSMA: prostate-specific membrane antigen) as potential biomarkers of PrCa progression in AS patients. With ethics approval from the Hamilton Integrated Research Ethics Board (HiREB), 40 AS patients were accrued prospectively from the Niagara Health System PrCa diagnostic program clinics and were asked to donate their biopsy tissue. 28 patients progressed on repeat biopsies at 12 or 24 months after initial diagnosis and were included in the “Progressed” group, and 12 did not who were included in the “Non-Progressed” group. Baseline diagnostic prostate core biopsy tissues of both groups were evaluated with H&E and immunohistochemistry (IHC) staining for ACLY, ACC, GLUT1, AMACR and PSMA expression (quantified by H-score). H-scores were evaluated in benign and malignant components (epithelial cells) and were compared between the two groups of patients. We observed statistically significant increased GLUT1 expression in malignant epithelial cells of the progressed group compared to the non-progressed group. Also, we found statistically significant increased PSMA expression in the benign epithelial cells of the progressed group compared to the non-progressed group. Further, our results demonstrated a statistically significant increase in ACLY and ACC expression in malignant epithelial cells compared to benign epithelial cells in the progressed group, while AMACR was detected solely in the malignant component. Overall, the results of this pilot study are consistent with the notion of induction of glycolytic metabolism, de novo lipogenesis and increased PSMA expression associated with the risk for PrCa progression. The levels of expression of PSMA within benign epithelial cells and GLUT1 within malignant epithelial cells may have value as predictive markers of risk for PrCa progression in AS patients. Future studies should investigate this concept systematically in larger AS cohorts. / Thesis / Master of Science (MSc) / Currently, many patients with localized prostate cancer do not receive immediate therapy and are monitored within systematic active surveillance (AS) programs. The main aim of AS management is to prevent overtreatment and treatment-related complications in patients who would otherwise have a good quality of life despite dealing with prostate cancer. However, many of these patients, especially those with low intermediate-risk prostate cancer have a significant risk for disease progression and metastasis. Additionally, there is a lack of promising tissue biomarkers to predict the risk for progression in AS patients at the time of initial diagnosis. Research showed that metabolism dysregulation is an essential hallmark of cancer progression, including prostate cancer. In this pilot study, we examined whether the expression of enzymes involved in lipid, glucose and protein metabolism could have value as biomarkers of risk for prostate cancer progression in patients managed with AS. The expression of five metabolic enzymes (ACLY, ACC, GLUT1, AMACR and PSMA) was examined in tumor and benign regions of diagnostic biopsies of the prostate obtained from men managed with AS. Our early results suggest that the expression of enzymes of protein (PSMA) and glucose (GLUT1) metabolism may have value as biomarkers of risk for prostate cancer progression and should be investigated further in systematic studies.

Background: Recent evidence suggests that the prostate cancer (PCa)-specific up-regulation of certain genes such as AMACR, EZH2, PSGR, PSMA and TRPM8 could be associated with an aberrant expression of non-coding microRNAs (miRNA). Methods: In silico analyses were used to search for miRNAs being putative regulators of PCa-associated genes. The expression of nine selected miRNAs (hsa-miR-101, -138, -186, -224, -26a, -26b, -374a, -410, -660) as well as of the aforementioned PCa-associated genes was analyzed by quantitative PCR using 50 malignant (Tu) and matched non-malignant (Tf) tissue samples from prostatectomy specimens as well as 30 samples from patients with benign prostatic hyperplasia (BPH). Then, correlations between paired miRNA and target gene expression levels were analyzed. Furthermore, the effect of exogenously administered miR-26a on selected target genes was determined by quantitative PCR and Western Blot in various PCa cell lines. A luciferase reporter assay was used for target validation. Results: The expression of all selected miRNAs was decreased in PCa tissue samples compared to either control group (Tu vs Tf: -1.35 to -5.61-fold; Tu vs BPH: -1.17 to -5.49-fold). The down-regulation of most miRNAs inversely correlated with an up-regulation of their putative target genes with Spearman correlation coefficients ranging from -0.107 to -0.551. MiR-186 showed a significantly diminished expression in patients with non-organ confined PCa and initial metastases. Furthermore, over-expression of miR-26a reduced the mRNA and protein expression of its potential target gene AMACR in vitro. Using the luciferase reporter assay AMACR was validated as new target for miR-26a. Conclusions: The findings of this study indicate that the expression of specific miRNAs is decreased in PCa and inversely correlates with the up-regulation of their putative target genes. Consequently, miRNAs could contribute to oncogenesis and progression of PCa via an altered miRNA-target gene-interaction.

<p>The natural history of localized prostate cancer is not fully understood. In most patients the tumor will never progress to a lethal disease, while a subset of patients will ultimately die of the disease. Efficient tools to separate indolent from lethal disease is currently lacking which means that many patients will be offered treatment without any benefit, but still be at risk of experiencing treatment related side effects.</p><p>The aims of these studies were to get more insight into the natural history of untreated localized prostate cancer, to assess the prognostic value of established clinical parameters such as Gleason score, nuclear grade and tumor volume and, moreover, some new prognostic markers Ki-67, AMACR and MUC-1. We also aimed to study time trends in the detection of incidental tumors in Sweden.</p><p>Patients with localized disease (n=223) and no initial treatment were followed for 21 years. Most patients had a favorable outcome. However, a subset of patients developed lethal disease even beyond 15 years of follow-up and these patients define the group that may benefit most from treatment with curative intent. Patients with poorly differentiated tumors experienced a 9 time higher risk of dying in prostate cancer.</p><p>The studies on prognostic markers are based on a cohort of patients (n=253) with incidental prostate cancer detected by transurethral resection for presumed benign hyperplasia. All patients were left without initial treatment. Gleason grade, nuclear grade and tumor volume turned all out to be independent prognostic factors. MUC-1, AMACR and Ki-67 also carried prognostic information. However, after adjustment for Gleason grade, nuclear grade and tumor volume only MUC-1 and AMACR remained as statistically significant prognostic factors. When tested for sensitivity and specificity they all failed and, consequently, they seem to be of less value in daily practice for cancelling an individual patient regarding the choice of treatment.</p><p>Time trends in incidental prostate tumors in Sweden were analyzed in a cohort of patients with prostate tumors detected by transurethral resection (TUR-P). Through linkage of the national registration number (NRN) with several registers, e.g. the Swedish Cancer Registry, the National Inpatient registry and the Cause of Death Registry we identified, during the period 1970 through 2003, in total 23288 patients with incidental prostate cancer, who constituted the study group. As comparison group we choose all patients diagnosed with prostate cancer between 1970-2003 excluding those with incidental cancer, in total 112204 patients. Our result confirms earlier findings that there has been a dramatic change over time in incidence of incidental prostate cancers in Sweden, which parallels the introduction of prostate specific antigen. We also found that the cumulative incidence of prostate cancer death is high in the incidental group, opposing earlier findings that incidental tumours are a non-lethal disease.</p> / issn 1642-4063

The natural history of localized prostate cancer is not fully understood. In most patients the tumor will never progress to a lethal disease, while a subset of patients will ultimately die of the disease. Efficient tools to separate indolent from lethal disease is currently lacking which means that many patients will be offered treatment without any benefit, but still be at risk of experiencing treatment related side effects. The aims of these studies were to get more insight into the natural history of untreated localized prostate cancer, to assess the prognostic value of established clinical parameters such as Gleason score, nuclear grade and tumor volume and, moreover, some new prognostic markers Ki-67, AMACR and MUC-1. We also aimed to study time trends in the detection of incidental tumors in Sweden. Patients with localized disease (n=223) and no initial treatment were followed for 21 years. Most patients had a favorable outcome. However, a subset of patients developed lethal disease even beyond 15 years of follow-up and these patients define the group that may benefit most from treatment with curative intent. Patients with poorly differentiated tumors experienced a 9 time higher risk of dying in prostate cancer. The studies on prognostic markers are based on a cohort of patients (n=253) with incidental prostate cancer detected by transurethral resection for presumed benign hyperplasia. All patients were left without initial treatment. Gleason grade, nuclear grade and tumor volume turned all out to be independent prognostic factors. MUC-1, AMACR and Ki-67 also carried prognostic information. However, after adjustment for Gleason grade, nuclear grade and tumor volume only MUC-1 and AMACR remained as statistically significant prognostic factors. When tested for sensitivity and specificity they all failed and, consequently, they seem to be of less value in daily practice for cancelling an individual patient regarding the choice of treatment. Time trends in incidental prostate tumors in Sweden were analyzed in a cohort of patients with prostate tumors detected by transurethral resection (TUR-P). Through linkage of the national registration number (NRN) with several registers, e.g. the Swedish Cancer Registry, the National Inpatient registry and the Cause of Death Registry we identified, during the period 1970 through 2003, in total 23288 patients with incidental prostate cancer, who constituted the study group. As comparison group we choose all patients diagnosed with prostate cancer between 1970-2003 excluding those with incidental cancer, in total 112204 patients. Our result confirms earlier findings that there has been a dramatic change over time in incidence of incidental prostate cancers in Sweden, which parallels the introduction of prostate specific antigen. We also found that the cumulative incidence of prostate cancer death is high in the incidental group, opposing earlier findings that incidental tumours are a non-lethal disease.

>Magister Scientiae - MSc / Prostate cancer, commonly referred to as adenocarcinoma of the prostate, is the leading cause of cancer death in men in 46 countries, and it was estimated that by the end of 2018 there would approximately be 1.3 million new cases of prostate cancer worldwide. Currently, the Food and Drug Administration (FDA) approved biomarker for prostate cancer disease diagnostics Prostate Specific Antigen (PSA) is not specific to the disease itself but extends to other cases such as Benign Prostate Hyperplasia (BPH) a condition in which the prostate grows uncontrollably. This biomarker is then detected in blood samples via conventional methods which require a qualified individual to operate and are often time consuming. Examples of these methods are spectrophotometry and High Performance Liquid Chromatography (HPLC). Hence, a more efficient biomarker and method of detection is needed for prostate cancer disease diagnostics, as early detection of the disease means early treatment, which could ultimately save lives. Currently, an emerging biomarker for prostate cancer known as Alpha-Methyl CoA Racemase (AMACR) has shown to be more specific to the disease with advantages such as being a non-invasive biomarker. AMACR has been reported to be present in urine, and thus may be detected via a non-invasive method. This study proposed an economical, non-invasive electrochemical biosensor for the rapid detection of AMACR based on mercaptosuccinic acid capped tungsten telluride (MSA-WTe3) quantum dots (QDs). Nanomaterial has shown promise in terms of increasing the sensitivity and specificity of sensors. MSA-WTe3 QDs was successfully synthesized using easy, inexpensive method and was studied by various techniques such as High Resolution Transmission Electron Microscopy (HR-TEM) where the size was confirmed to be within the nanometer scale and was reported to be 2.65 nm with a good crystallinity. X-ray diffraction (XRD) confirmed the structural properties and chemical composition of the QDs and it is reported that the QDs are rich in both tellurium and tungsten and comprise of a hexagonal structure. Scanning Electron Microscopy (SEM) confirmed the successful immobilization of aptamer sequence specific to AMACR onto the electrode surface by showing a distinct conformational change when aptamers were introduced to the QDs under study. This study reports the successful detection of AMACR using an MSA-WTe3 QDs based aptasensor immobilized onto a screen printed glassy carbon electrode, with a detection limit of 0.35651 ng/mL and a limit of quantification calculated to be 1.08033 ng/mL.

Background: Recent evidence suggests that the prostate cancer (PCa)-specific up-regulation of certain genes such as AMACR, EZH2, PSGR, PSMA and TRPM8 could be associated with an aberrant expression of non-coding microRNAs (miRNA). Methods: In silico analyses were used to search for miRNAs being putative regulators of PCa-associated genes. The expression of nine selected miRNAs (hsa-miR-101, -138, -186, -224, -26a, -26b, -374a, -410, -660) as well as of the aforementioned PCa-associated genes was analyzed by quantitative PCR using 50 malignant (Tu) and matched non-malignant (Tf) tissue samples from prostatectomy specimens as well as 30 samples from patients with benign prostatic hyperplasia (BPH). Then, correlations between paired miRNA and target gene expression levels were analyzed. Furthermore, the effect of exogenously administered miR-26a on selected target genes was determined by quantitative PCR and Western Blot in various PCa cell lines. A luciferase reporter assay was used for target validation. Results: The expression of all selected miRNAs was decreased in PCa tissue samples compared to either control group (Tu vs Tf: -1.35 to -5.61-fold; Tu vs BPH: -1.17 to -5.49-fold). The down-regulation of most miRNAs inversely correlated with an up-regulation of their putative target genes with Spearman correlation coefficients ranging from -0.107 to -0.551. MiR-186 showed a significantly diminished expression in patients with non-organ confined PCa and initial metastases. Furthermore, over-expression of miR-26a reduced the mRNA and protein expression of its potential target gene AMACR in vitro. Using the luciferase reporter assay AMACR was validated as new target for miR-26a. Conclusions: The findings of this study indicate that the expression of specific miRNAs is decreased in PCa and inversely correlates with the up-regulation of their putative target genes. Consequently, miRNAs could contribute to oncogenesis and progression of PCa via an altered miRNA-target gene-interaction.