Documento descargado de http://www.elsevier.es el 02/10/2016. Copia para uso personal, se prohíbe la transmisión de este documento por cualquier medio o formato. Actas Urol Esp. 2014;38(6):397---404 Actas Urológicas Españolas www.elsevier.es/actasuro ORIGINAL ARTICLE Effects of resveratrol and other wine polyphenols on the proliferation, apoptosis and androgen receptor expression in LNCaP cells夽 A. Ferruelo a , I. Romero b , P.M. Cabrera b , I. Arance b , G. Andrés b , J.C. Angulo b,∗ a Unidad de Investigación, Fundación para la Investigación Biomédica, Hospital Universitario de Getafe, Madrid, Spain Servicio de Urología, Hospital Universitario de Getafe, Departamento Clínico, Facultad de Ciencias Biomédicas, Universidad Europea de Madrid, Madrid, Spain b Received 10 February 2014; accepted 19 February 2014 Available online 22 May 2014 KEYWORDS Cell proliferation; Apoptosis; Androgen receptor; LNCaP; Resveratrol; Polyphenols Abstract Purpose: To address the effect of resveratrol and other red wine polyphenols on cell proliferation, apoptosis and androgen receptor (AR) expression in human prostate cancer LNCaP cells. Materials and methods: LNCaP cells (5 × 102) were cultured in microtiter plate modules and treated with gallic acid, tannic acid and quercetin (1, 5 and 10 M), rutin and morin (25, 50 and 75 M) and resveratrol (5, 10 and 25 M). To address the extent of proliferation at 24, 48, 72 and 96 h, a colorimetric immunoassay method was used. An activity caspase 3/7 detection assay was used to disclose apoptosis at 24, 48 and 72 h. AR mARN levels were determined by real time RT-PCR. Results: All polyphenols studied significantly inhibited (P < .05) cell proliferation compared to control. However, there were moderate differences between them. Resveratrol was the strongest inhibitor at different times and doses. Also, caspase-3 and caspase-7 activity was significantly higher (P < .05) than control in the presence of all the compounds, but the earlier response was achieved by resveratrol. Resveratrol, quercetin and morin were the only nutrients that significantly inhibited AR mRNA expression. Again resveratrol produced the highest inhibition (90---250 times less than control), followed by morin (67---100 times) and quercetin (55---91 times). 夽 Please cite this article as: Ferruelo A, Romero I, Cabrera PM, Arance I, Andrés G, Angulo JC. Los efectos de resveratrol y otros polifenoles del vino sobre la proliferación, apoptosis y expresión de receptor androgénico en células LNCaP. Actas Urol Esp. 2014;38:397---404. ∗ Corresponding author. E-mail address: javier.angulo@salud.madrid.org (J.C. Angulo). 2173-5786/$ – see front matter © 2014 AEU. Published by Elsevier España, S.L. All rights reserved. Documento descargado de http://www.elsevier.es el 02/10/2016. Copia para uso personal, se prohíbe la transmisión de este documento por cualquier medio o formato. 398 A. Ferruelo et al. Conclusions: All polyphenols studied showed important antiproliferative effects and induced apoptosis when added to LNCaP cells culture. We confirm that resveratrol, morin and quercetin may achieve such effect through reduced expression of AR. The synergistic effects of these compounds and their potential to prevent progression of hormone-dependent prostate cancer merit further study. © 2014 AEU. Published by Elsevier España, S.L. All rights reserved. PALABRAS CLAVE Proliferación celular; Apoptosis; Receptor androgénico; LNCaP; Resveratrol; Polifenoles Los efectos de resveratrol y otros polifenoles del vino sobre la proliferación, apoptosis y expresión de receptor androgénico en células LNCaP Resumen Propósito: Abordar el efecto del resveratrol y otros polifenoles del vino tinto sobre la proliferación celular, la apoptosis y la expresión del receptor androgénico (RA) en células LNCaP de cáncer de próstata humano. Materiales y métodos: Las células LNCaP (5 × 102) se cultivaron en módulos de placas de microtitulación y se trataron con ácido gálico, ácido tánico y quercetina (1, 5 y 10 M), rutina y morina (25, 50 y 75 M) y resveratrol (5, 10 y 25 M). Para abordar el alcance de la proliferación a las 24, 48, 72 y 96 h se utilizó un método de inmunoanálisis colorimétrico. Se utilizó un ensayo de detección de actividad de caspasa 3/7 para revelar la apoptosis a las 24, 48 y 72 h. Se determinaron niveles de ARNm de RA mediante RT-PCR a tiempo real. Resultados: Todos los polifenoles estudiados inhibieron significativamente (p<0,05) la proliferación celular en comparación con el control. Sin embargo, hubo diferencias moderadas entre ellos. El resveratrol fue el inhibidor más fuerte en diferentes momentos y dosis. También la actividad de caspasa-3 y caspasa-7 era significativamente mayor (p<0,05) que el control en la presencia de todos los compuestos, pero la respuesta anterior se logró por el resveratrol. El resveratrol, la quercetina y la morina fueron los únicos nutrientes que inhibían significativamente la expresión de ARNm de RA. Una vez más el resveratrol produjo la inhibición más alta (90-250 veces menor que el control), seguido por morina (67-100 veces) y quercetina (55-91 veces). Conclusiones: Todos los polifenoles estudiados mostraron importantes efectos antiproliferativos y apoptosis inducida cuando se añadieron al cultivo de células LNCaP. Confirmamos que el resveratrol, la morina y la quercetina pueden lograr tal efecto a través de la reducción de expresión de RA. Los efectos sinérgicos de estos compuestos y su potencial para prevenir la progresión del cáncer de próstata hormono-dependiente merecen ser estudiados en profundidad. © 2014 AEU. Publicado por Elsevier España, S.L. Todos los derechos reservados. Introduction Prostate cancer is the most common neoplasm diagnosed in men in industrialized countries.1 Since the introduction of prostate-specific antigen (PSA) screening test in the late 1980s and because of the increasing public awareness with respect to this disease in the early 1990s, the number of new cases has increased dramatically during the last decade.1 Besides PCa screening,2 other possible causes for its increasing incidence are aging of the population, the high consumption of meat and fat and the higher rates of obesity.3 In Mediterranean countries, with a high intake of olive oil, fruits, vegetables and wine, the incidence of prostate cancer is much lower than that in other western countries.4,5 All those food products contain important amounts of phenolic compounds, commonly referred to as polyphenols.6 Flavonoids are the most common polyphenolic compounds present in vegetables. An important effect of flavonoids is their strong antioxidant activity: they are scavengers of oxygen-derived free radicals which are involved in tumor promotion.2 Flavonoids have also shown many biological properties that may account for cancer chemoprevention as apoptosis enhancement, cell growth arrest, inhibition of DNA synthesis, and modulation of signal transduction pathways.7 The authors conducted a previous study that showed that some red wine polyphenols inhibited the proliferation and induced apoptosis in human prostate cancer LNCaP cells cultured in medium containing androgens8 and also in murine bladder cancer cell line MB-49.9 Polyphenols are usually absorbed from the upper gastrointestinal tract, showing an increased uptake at the liver, heart and kidney.10 A regular ingestion of polyphenols is necessary to obtain biologically important concentrations.11 Red wine is a rich source of polyphenolic substances and more than 200 individual phenolic compounds have been identified catechin, quercetin, phenolic acid, and resveratrol being the most important.11,12 On the other hand, evidence has shown that androgens are involved in the development and progression of prostate cancer,13 and their biological effects in the prostate are mediated by the AR, a ligand-activated transcription factor of the nuclear receptor superfamily.14 Most of the molecular Documento descargado de http://www.elsevier.es el 02/10/2016. Copia para uso personal, se prohíbe la transmisión de este documento por cualquier medio o formato. Resveratrol and LNCaP cell mechanisms responsible for the development of recurrent hormone-refractory tumors involve alterations in the function of the AR and its complex signaling pathways.14 Thus, the AR could still play a role in the development of prostatic malignancy and strategies to minimize the AR function are expected to play a beneficial role. We investigate the effect of some red wine polyphenols on cell proliferation, apoptosis, and androgen receptor expression in human prostate cancer LNCaP cells. Materials and methods Cell cultures and treatments The androgen-responsive LNCaP human prostate cancer cell line (American Type Culture Collection, Rockville, MD, USA) was used. This cell line shows functional AR.15 It was maintained in RPMI 1640 (Gibco BRL, Barcelona, Spain) supplemented with 5% heat-inactivated fetal bovine serum (FCS, LINUS, Cultek, Madrid, Spain), 100 U/ml penicillin G, 0.1 mg/ml streptomycin, 50 g/ml gentamicin, and 2 mM l-glutamine (Gibco BRL, Barcelona, Spain). All cells were cultured in a humidified atmosphere of 95% air and 5% CO2 at 37 ◦ C. For the assays, the FCS in the medium was replaced by 5% charcoal-stripped FCS (cFCS, LINUS, Cultek, Madrid, Spain) and the cells were treated with several concentrations of the following polyphenols: tannic acid (1---10 M), gallic acid (1---10 M), quercetin (1---10 M), rutin (25---75 M), morin (25---75 M) and resveratrol (5---25 M) during 24, 48, 72 and 96 h. All compounds were purchased from Sigma---Aldrich (St. Louis, MO, USA) and dissolved in either ethanol (tannic acid, gallic acid, quercetin and resveratrol) or DMSO (rutin and morin) and stored at −20 ◦ C. The final concentrations used for different experiments were prepared by diluting the stock with RPMI before use. Non-treated LNCaP cells in a carrier solvent (0.1% DMSO or ethanol) were used as control. Assay for cell proliferation Cells were subcultured into a 96-well plate with 1 × 103 cells per well in 100 l medium. After overnight incubation, the medium in each well was discarded and replaced by fresh medium with the above-mentioned polyphenols at the indicated concentrations. The medium was changed and the same polyphenol concentration added every 24 h. The results were obtained after 24, 48, 72 and 96 h of incubation. The extent of proliferation was assessed using a colorimetric immunoassay (Cell Proliferation ELISA BrdU, Roche, Barcelona, Spain). This technique is based on the incorporation of the pyridine analog bromodeoxyuride (BrdU) instead of thymidine into the DNA of proliferating cells. This BrdU is detected by immunoassay, by measuring the absorbance at 450 nm in an ELISA microplate auto reader (Bio-Tek Instruments, Winoonski, USA). Absorbance values directly correlate with the amount of DNA synthesis and therefore with the number of proliferating cells. Experiments were repeated a minimum of three times and the results expressed in absorbance units (AU). 399 Caspase-3/7 activity assays The cells were grown in 6-well plates at a density of 1 × 105 cells per well and treated with the highest doses of each polyphenol used in the proliferation study. At 24, 48, 72 and 96 h of treatment, the media was aspirated and the cells were washed once with PBS. Then we added M-PER mammalian protein extraction reagent (Pierce, Rockford, IL, USA) with fresh protease inhibitor cocktail (Boehringer Mannheim, Germany). The cells were gently stirred for 5 min and the lysate was collected in a microfuge tube. The lysate was cleared by centrifugation at 13,000 rpm for 10 min and the supernatant was either used or immediately stored at −80 ◦ C. The protein concentration was determined by BCA Protein Assay using the manufacturer’s protocol (Pierce, Rockford, IL, USA). For apoptosis quantification we used a luminescent assay that measures caspase-3 and -7 activities (Caspase-Glo 3/7 Assay. Promega, Madison, WI, USA). Briefly, the assay provides a proluminescent substrate for caspase 3/7 in a reagent optimized for caspase activity, luciferase activity, and cell lysis. The addition of reagent results in cell lysis, caspase cleavage of the substrate, and generation of a ‘‘glow-type’’ luminescent signal produced by luciferase. Luminescence is proportional to the amount of caspase activity present. For this assay we used 1 g protein for each determination. Androgen receptor real-time RT-PCR RNA was prepared from cell samples using Rneasy (Qiagen, Valencia, CA, USA) according to the manufacturer’s instructions. The RNA was then quantitated using a spectrophotometer (absorbance to 260/280 nm). To analyze the expression of AR by real-time PCR, 1 g of total RNA from each sample was used for first-strand cDNA using random primers and Moloney murine leukemia virus (MMLV) reverse transcriptase (Sigma, St. Louis, MO, USA). All PCR reactions were performed using a fluorescence temperature cycler (iCycler, Bio-Rad Laboratories, Hercules, CA, USA) with 25 l reaction mixture containing 12.5 l Universal PCR Master Mix (Applied Biosystems, Madrid, Spain), 1.25 l of a mix of unlabelled PCR primers (AR or 18S) and Taqman MGB probe (Assays-on-Demand, Applied Biosystems, Madrid, Spain). PCR reactions were cycled according to the manufacturer’s instructions. To determine the relative expression of AR in each sample, the results were normalized to 18S (used as an internal standard) and the comparative CT method was used (User Bulletin #2 (2001), Applied Biosystem, Madrid, Spain). For the comparative CT calculation to be valid, the efficiency of the target amplification should approximately equal the reference amplification. Finally, template dilution was made for AR (range: 0.025---1 ng) and 18S (range: 0.001---0.025 ng) and the PCR efficiency of the target amplification was approximately equal to the reference amplification. Cells were treated with control and the highest concentrations of different polyphenols for 24 and 48 h. At the end of each incubation period, total RNA was reversetranscripted to cDNA and quantitative real-time PCR was Documento descargado de http://www.elsevier.es el 02/10/2016. Copia para uso personal, se prohíbe la transmisión de este documento por cualquier medio o formato. 400 A. Ferruelo et al. b 800 800 Control 700 1µM 700 600 5µM 10µM 600 AU (450-630 nm) AU (540-630 nm) a 500 400 300 Control 25µM 50µM 75µM 500 400 300 200 200 100 100 0 0 24H 48H 72H 96H 24H 800 d Control 800 1µM 700 25µM 600 5µM 10µM 600 50µM 75µM 500 400 300 100 48H 72H 24H 96H Incubation time (h) 48H 96H Incubation time (h) f Control 1µM 5µM 10µM AU (450-630 nm) AU (450-630 nm) 72H 0 24H 600 96H 300 200 700 72H 400 100 800 96H 500 200 0 e 72H Control 700 AU (450-630 nm) AU (450-630 nm) c 48H Incubation time (h) Incubation time (h) 500 400 300 800 5µM 600 10µM 25µM 500 400 300 200 200 100 100 0 Control 700 0 24H 48H 72H 96H 24H Incubation time (h) 48H Incubation time (h) Figure 1 Effect of polyphenols on cell proliferation of human prostate cancer cells (LNCaP) over 96 h of incubation. Cells were treated with different concentrations of polyphenols (M) and proliferation cell determined by the cell proliferation ELISA BrdU assay. (a) Tannic acid, (b) rutin, (c) gallic acid, (d) morin, (e) quercetin and (f) resveratrol. Values are means ± SE of a typical experiment in triplicate. *P < 0.05 and **p < 0.01 vs. control. performed. Values were calculated as mean ± SE of a typical experiment performed in triplicate. and 7 activity were carried out with Student’s unpaired t test. Significance level was reached when p < 0.05. Results Statistical analysis Effect of polyphenols on cell proliferation One-way ANOVA with Dunnett t-test post hoc analysis was used to compare and AR expression analysis between treated and control groups. Comparisons with regard to caspase 3 Fig. 1 shows the effect of different polyphenols on LNCaP cells proliferation. Although all the tested polyphenols Documento descargado de http://www.elsevier.es el 02/10/2016. Copia para uso personal, se prohíbe la transmisión de este documento por cualquier medio o formato. Resveratrol and LNCaP cell 401 a b 250 250 Control 10µM 200 RLU X 1000 RLU X 1000 200 150 100 50 48h 72h c 24h 48h 72h 48h 72h 48h 72h d 160 140 Control 10µM 140 120 RLU X 1000 120 RLU X 1000 100 0 24h 100 80 60 80 60 40 20 20 0 24h 140 120 Control 75µM 100 40 0 48h 72h 24h f Control 10µM 300 Control 25µM 250 100 RLU X 10000 RLU X 1000 150 50 0 e Control 75µM 80 60 40 200 150 100 50 20 0 0 24h 48h 72h 24h Figure 2 Polyphenol-induced apoptotic cell death in LNCaP cells. Cells were treated with the highest concentrations of polyphenols for 24, 48 and 72 h. At the end of the different incubation period, cells were lysated and analyzed for activity of caspase-3 and -7 with the aid of a luminometric assay. (a) Tannic acid, (b) rutin, (c) gallic acid, (d) morin, (e) quercetin and (f) resveratrol. Values are means ± SE of a typical experiment performed in triplicate. *P < 0.05 and **p < 0.01 vs. control. successfully inhibited cell proliferation, there were moderate differences between them. Resveratrol was the strongest inhibitor at different times and doses. Cell proliferation was significantly inhibited by tannic and gallic acid at 5 and 10 M at any incubation time. The weakest effect was produced by quercetin; however, it was able to inhibit cell proliferation at 96 h (as the rest of nutrients). Effect on caspase-3 and caspase-7 activity We added flavonoids at highest concentrations that inhibited proliferation in this study, during 24, 48, and 72 h. The cell lysates were then analyzed for caspase-3/7 activity by means of a luminometric assay (Fig. 2). All the polyphenols tested significantly increased the caspase-3/7 activity. At 24 h, the activity of both enzymes increased and was highest at 72 h after the addition of resveratrol. With the rest of polyphenols, the activity of caspase-3/7 increased at 48 h and it also reached its maximum at 72 h. Effect on androgen receptor expression To determine changes in AR mRNA expression after polyphenol exposure, real time RT-PCR was used. LNCaP cells were exposed to a nutrient concentration known to induce caspase-3/7 activity as revealed in the previous phase of the present study. As shown in Table 1, quercetin, morin and resveratrol were the only nutrients that significantly inhibited AR mRNA expression. Again, resveratrol produced the highest inhibition (90---250 times less than control). Quercetin and morin also produced inhibition, but the lower magnitude (55---91 and 67---100 times, respectively). Discussion Epidemiological studies have demonstrated a considerable geographical variation in the age-adjusted incidence of prostate cancer and environmental agents play a very important role.5,16 Many studies have addressed the relationship between nutrients (some of them included in the present study) and anticancer protection.4,17 Nutritional agents as Documento descargado de http://www.elsevier.es el 02/10/2016. Copia para uso personal, se prohíbe la transmisión de este documento por cualquier medio o formato. 402 A. Ferruelo et al. Table 1 Relative quantification of androgen receptor mARN by real-time RT-PCR in LNCaP cells treated with the highest concentrations of polyphenols for 24 and 48 h. Nutrients 48 h Mean CT RA Mean CT 18S C T10 M75 G10 R75 Q10 RV25 28.4 26.83 32.9 27.53 27.87 32.62 33.4 ± ± ± ± ± ± ± 0.1 0.21 0.1 0.06 0.15 0.15 0.1 25.63 24.47 24.07 23.93 25.7 24.07 24.17 ± ± ± ± ± ± ± 0.21 ± 0.21 0.21 0.15 0.17 0.15 0.1 C T10 M75 G10 R75 Q10 RV25 28.07 27.97 34.2 28.57 28.17 34.53 36.07 ± ± ± ± ± ± ± 0.12 0.06 0.2 0.06 0.06 0.21 0.15 24.8 24.8 24.3 24.93 24.8 24.77 24.7 ± ± ± ± ± ± ± 0.1 0.1 0.2 0.06 0.1 0.15 0.1 CT (AR-18S) CT CT −CT (control) RA levels (2−CT ) 2.77 2.34 8.84 3.57 2.17 8.57 9.23 ± ± ± ± ± ± ± 0.23 0.29 0.23 0.16 0.23 0.22 0.12 0.0 −0.4 6.06 0.83 −0.6 5.8 6.46 ± ± ± ± ± ± ± 0.23 0.29 0.23 0.16 0.23 0.22 0.12 1.0 1.32 0.015 0.58 1.52 0.018 0.011 3.27 3.17 9.9 3.63 3.37 9.77 11.37 ± ± ± ± ± ± ± 0.15 0.12 0.28 0.08 0.12 0.26 0.18 0.0 0.1 6.63 0.36 0.1 6.5 8.1 ± ± ± ± ± ± ± 0.15 0.12 0.28 0.08 0.12 0.26 0.18 1.0 1.07 0.01 0.78 0.94 0.011 0.004 CT ; cycle threshold; C: control; T: tannic acid; M: morin; G: gallic acid; R: rutin; Q: quercetin; RV: resveratrol. soy isoflavones, lycopene, vitamin E, selenium, vitamin D, and other polyphenols have been found to inhibit proliferation or to induce apoptosis in some prostate cancer cell lines. Grapes and wine are known natural sources of dietary polyphenols, and tannins as tannic and gallic acid, both present in red wine, have also been found to have antiinitiating and antipromoting properties.18 In a previous study the authors demonstrated the inhibitory effect of some of the mentioned polyphenols on the proliferation of LNCaP cells.8 In our study we focussed on six polyphenols (quercetin, rutin, morin, resveratrol, gallic acid and tannic acid) that are invariably present in red wine, an important constituent of Mediterranean diet. We have demonstrated a growth inhibition of LNCaP cells at different concentrations and time of exposure to those nutrients. Resveratrol, tannic and gallic acid were the most successful inhibitors of the growth of LNCaP cells, while quercetin, rutin and morin required higher concentrations and longer exposure times to inhibit cell proliferation. Our findings were consistent with reports available in the literature.19,20 Suppression of cell proliferation through alterations in division and apoptosis has been documented as well.21 Caspase-3/7 ultimately appears to function downstream in the apoptosis pathway and is associated with the cleavage of many critical cellular substrates. In our experiment we found an increase in the activity of both enzymes in LNCaP cells after exposure to the studied polyphenols. This finding supports apoptosis as a major mechanism of polyphenol-induced antiproliferative effects in our study.8,20 On the other hand, we used a real-time RT-PCR method for relative quantification of AR gene expression. We observed a reduced expression of AR mRNA in LNCaP cells induced by the flavonoids rutin and morin and the phytoalexin resveratrol at 24 and 48 h after exposure. Other studies have demonstrated the inhibition capacity of resveratrol and quercetin over AR mRNA expression, but not by the flavonoid morin.22 LNCaP cells are known to be androgen sensitive and proliferate in response to AR activation, and down-regulation of the AR protein using antisense knockdown produced an inhibition of growth and an increase of the apoptosis rate.23 This could indicate that the effects of resveratrol, quercetin and morin could be, at least in part, mediated by regulation of the expression of the AR gene. On the other hand, such hypothesis is not likely to be valid for the other studied nutrients. Androgens are involved in the development and progression of prostatic neoplasia and AR is the essential mediator for the androgen action. This nuclear receptor is activated by its ligands, testosterone and 5␣-dihydrotestosterone, and consequent dissociation by the heat shock proteins. The activation process includes recruitment of coactivators. Finally, activation of AR upregulates the transcription of genes containing androgen-response elements in their promoters. So, the suppression of androgen signaling is a therapeutic target for prostate cancer. Resveratrol inhibits the function of the androgen receptor and also modulates AR transcriptional activity,24 but this is not the only nutrient to downregulate expression of androgen synthesizing genes as revealed by studies conducted with pomegranate and green tea polyphenols in LNCaP-AR, LNCaP 104-S, LNCaP R1Ad and LNCaP 104-R1 cells.25,26 Apart from the reduction of AR gene expression, cell cycle arrest and promotion of apoptosis, many other mechanisms are likely to mediate the action of polyphenols on prostate cancer cell lines. Resveratrol, quercetin and other nutrients have also been reported to inhibit the hedgehog cascade and GLI-1 expression and suppress the in vitro growth of androgen-dependent LNCaP and androgenindependent AI PC3 cell lines.27 According to the National Cancer Institute, about 400 compounds are considered potentially chemopreventive agents.28 Data regarding the accumulated evidence of polyphenolic substances and flavonoids limiting presentation and or progression of prostate cancer in humans Documento descargado de http://www.elsevier.es el 02/10/2016. Copia para uso personal, se prohíbe la transmisión de este documento por cualquier medio o formato. Resveratrol and LNCaP cell are very scarce, although resveratrol, epigallocatechin3-gallate, curcumin, genistein, and quercetin are under clinical evaluation.29 Preclinical investigations have established the anticarcinogenic effects induced by some dietary compounds using TRAMP and PTEN knockdown transgenic mouse models of prostate cancer and also the potential to reverse treatment resistance.30---32 In conclusion, the polyphenols studied have important antiproliferative effects and can induce apoptosis when added to LNCaP cells in culture. Resveratrol appears to be the most potent of these compounds and one of the mechanisms involved in the effect of this substance is mediated through a reduced expression of the androgen receptor. Very likely the effect of resveratrol is synergistic with that of other polyphenols, such as morin and quercetin. The results presented provide a rationale to more deeply study the in vivo effects of these nutrients. Possibly, with the aid of animal and epidemiological studies, more firm recommendations about the intake of these substances as chemopreventive agents could be made in the future. Funding This work was funded by the Beca Fundación para la Investigación en Urología (FIU) of the Spanish Urological Association. Conflict of interest The authors declare that they have no conflict of interest. References 1. Siegel R, Ma J, Zou Z, Jemal A. Cancer statistics, 2014. CA: Cancer J Clin. 2014;64:9---29. 2. Potosky AL, Miller BA, Albertsen PC, Kramer BS. The role of increasing detection in the rising incidence of prostate cancer. J Am Med Assoc. 1995;273:548---52. 3. Fradet Y, Meyer F, Bairati I, Shadmani R, Moore L. Dietary fat and prostate cancer progression and survival. Eur Urol. 1999;35:388---91. 4. Block G, Patterson B, Subar A. Fruit, vegetables and cancer prevention: a review of the epidemiological evidence. Nutr Cancer. 1992;18:1---29. 5. 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