Prostate-derived circulating microRNAs add prognostic value to prostate cancer risk calculators.

Prostate cancer is the second leading cause of malignancy-related deaths among American men. Active surveillance is a safe option for many men with less aggressive disease, yet definitively determining low-risk cancer is challenging with biopsy alone. Herein, we sought to identify prostate-derived microRNAs in patient sera and serum extracellular vesicles, and determine if those microRNAs improve upon the current clinical risk calculators for prostate cancer prognosis before and after biopsy. Prostate-derived intracellular and extracellular vesicle-contained microRNAs were identified by small RNA sequencing of prostate cancer patient explants and primary cells. Abundant microRNAs were included in a custom microRNA PCR panel that was queried in whole serum and serum extracellular vesicles from a diverse cohort of men diagnosed with prostate cancer. The levels of these circulating microRNAs significantly differed between indolent and aggressive disease and improved the area under the curve for pretreatment nomograms of prostate cancer disease risk. The microRNAs within the extracellular vesicles had improved prognostic value compared to the microRNAs in the whole serum. In summary, quantifying microRNAs circulating in extracellular vesicles is a clinically feasible assay that may provide additional information for assessing prostate cancer risk stratification.

Hormonal and genotoxic estrogen-androgen carcinogenesis in the NBL rat prostate: A role for aromatase.

BACKGROUND: Androgens are generally thought to cause prostate cancer, but the data from animal studies suggest that they must be aromatized to estrogen and act in concert with genotoxic estrogen metabolites. The objective of this study was to determine whether treatment with testosterone (T) combined with a nonestrogenic estrogen metabolite and a nongenotoxic estrogenic compound would all be necessary and sufficient for the induction of a high incidence of prostate cancer in the susceptible NBL rat strain. METHODS: NBL rats were treated with low-dose testosterone via slow-release Silastic implants and with the marginally estrogenic genotoxic catechol estrogen 4-hydroxyestradiol (4OH-E2) and the nongenotoxic estrogen 2-fluoroestradiol (2F-E2) and in one experiment the aromatase inhibitor letrozole via custom-made slow-release pellets. Animals were euthanized 52 weeks after implantation and their pituitaries and prostate complexes weighed and fixed in formalin. Hematoxylin and eosin (H&E)-stained step sections were prepared and examined microscopically for proliferative lesions. RESULTS: Animals treated with 2F-E2, with or without the other compounds, had enlarged pituitaries demonstrating its estrogenicity. Animals treated with T, with or without the other compounds, had enlarged prostates consistent with its androgenicity. Rats treated with T plus 2F-E2 and 4OH-E2 developed a high incidence of prostatic cancer (89%), while, surprisingly, rats treated with T plus only 2F-E2 also had a high incidence of prostate cancer (95%) contradicting our initial hypothesis. To test whether the formation of E2 from T by aromatase could lead to estrogen genotoxicity and prostate carcinogenesis we then rats treated with T and 2F-E2 also with letrozole and found that it reduced prostate cancer incidence by about 50%. CONCLUSIONS: These findings indicate that long-term treatment with a nongenotoxic estrogen (2F-E2) and T as well as uninhibited prostatic aromatase activity generating genotoxic E2 are all required for induction of a high incidence of prostatic adenocarcinomas in NBL rats. These and previous data indicate that androgen receptor-mediated action, estrogen receptor mediation, and estrogen genotoxicity are all required and sufficient for hormonal carcinogenesis in the NBL rat prostate. Interference with the estrogen genotoxicity is a potential approach to prostate cancer chemoprevention.

Effects of perinatal exposure to bisphenol A on induction of prostate cancer in Sprague Dawley rats by MNU and testosterone.

Perinatal and neonatal exposure to bisphenol A (BPA) has been linked to enhancement of prostate carcinogenesis in rats induced by combined treatment with estradiol and testosterone, but human data are lacking. This study aimed to determine the effects of perinatal BPA exposure on induction of prostate cancer in rats by sequential treatment with N-methyl-N-nitrosamine (MNU) and continuous low dose administration of testosterone. Pregnant Sprague Dawley rats were exposed to BPA administered by subcutaneous Alzet minipumps at doses of 2.5 or 25 µg/kg body weight/day from gestational day 9 until postnatal day 28 when pups were weaned providing exposure of offspring in utero and via the mother's milk. At 10-12 weeks of age, one male offspring per litter was treated with an intraperitoneal injection of MNU after hormonal stimulation of prostatic cell proliferation followed two weeks later by subcutaneous insertion of Silastic implants containing testosterone until the termination of the study 57-58 weeks after MNU injection. The perinatal BPA exposure did not significantly affect the incidence of prostate carcinomas which was slightly lower in exposed rats (33-23 %) than in control animals (40 %). Carcinomas in all accessory sex glands combined were also insignificantly less frequent in exposed (46-48 %) than in control rats (60 %). The incidence of malignant tumors at any site in the body was significantly lower in exposed rats (81-65 %) than in controls (93 %). In conclusion, perinatal BPA exposure did not significantly modify prostate cancer induction by MNU plus testosterone in rats, unlike the enhancement of prostate carcinogenesis induced by treatments involving estradiol administration. Which of the two models of prostate carcinogenesis is more relevant for the human situation is unclear at present.

Prostate-derived circulating microRNAs add prognostic value to prostate cancer risk calculators.

Prostate cancer is the second leading cause of malignancy-related deaths among American men. Active surveillance is a safe option for many men with less aggressive disease, yet definitively determining low-risk cancer is challenging with biopsy alone. Herein, we sought to identify prostate-derived microRNAs in patient sera and serum extracellular vesicles, and determine if those microRNAs improve upon the current clinical risk calculators for prostate cancer prognosis before and after biopsy. Prostate-derived intracellular and extracellular vesicle-contained microRNAs were identified by small RNA sequencing of prostate cancer patient explants and primary cells. Abundant microRNAs were included in a custom microRNA PCR panel that was queried in whole serum and serum extracellular vesicles from a diverse cohort of men diagnosed with prostate cancer. The levels of these circulating microRNAs significantly differed between indolent and aggressive disease and improved the area under the curve for pretreatment nomograms of prostate cancer disease risk. The microRNAs within the extracellular vesicles were the most informative and improved the AUC to 0.739 compared to the existing nomogram alone, which has an AUC of 0.561. The microRNAs in the whole serum improved it to AUC 0.675. In summary, quantifying microRNAs circulating in extracellular vesicles is a clinically feasible assay that may provide additional information for assessing prostate cancer risk stratification.

Effect of Dietary Methylseleninic Acid and Se-Methylselenocysteine on Carcinogen-Induced, Androgen-Promoted Prostate Carcinogenesis in Rats.

Selenomethionine (SeMet) did not prevent prostate cancer in the SELECT trial and in two hormone-driven rat models. However, we have shown that daily oral bolus administration of next-generation selenium forms, methylseleninic acid (MSeA) and Se-methylselenocysteine (MSeC) at 3 mg Se/kg body weight, inhibits prostate carcinogenesis in the TRAMP and pten-deficient mouse models and In Vivo growth of human prostate cancer cells. Here, we determined whether these Se forms prevent prostate cancer in a chemically induced-androgen promoted carcinogenesis rat model in which SeMet was not preventive. WU rats were treated with methylnitrosourea, and one week later, slow-release testosterone implants when they were randomized to groups fed AIN-93M diet supplemented with 3 ppm selenium as MSeA or MSeC or control diet. Mean survival, tumor incidence in all accessory sex glands combined (dorsolateral and anterior prostate plus seminal vesicle) and the incidence of tumors confined to dorsolateral and/or anterior prostate were not statistically significantly different among the groups. Thus, MSeA and MSeC feeding was not preventive in this model. The contrast with the inhibitory effects of MSeA and MSeC in mouse models may be due to differences in carcinogenic mechanisms, selenium dosage, delivery mode, and pharmacokinetics or fundamental rat-mouse differences in selenium metabolism.

The MNU Plus Testosterone Rat Model of Prostate Carcinogenesis.

Animal models of prostate cancer are essential to identify chemopreventive treatments against this major male malignancy. The N-methyl-N-nitrosourea (MNU) plus testosterone rat model of prostate carcinogenesis is a reliable animal model that recapitulates human prostate cancer in many respects and has been used extensively in chemoprevention studies with good predictive value for the results of human clinical trials. The objective of this article is to describe the induction protocol of this model, demonstrate its robustness and reproducibility over time and across rat strains, provide diagnostic criteria for the identification of prostate lesions, and present the current tumor induction protocol so that others can use this model in a reliable manner. The majority of accessory sex gland tumors in this model are adenocarcinomas originating in the anterior and dorsolateral prostate that metastasize to lungs and abdominal structures. The rat strain used is of critical importance, with the commercially available Wistar WU and Fischer F344 strains yielding the highest tumor incidences. Low dose, long-term testosterone treatment is essential for a high tumor incidence, but in advanced stage, large adenocarcinomas do not appear to be androgen dependent. This rat model is a robust and reproducible prostate cancer animal model of human prostate cancer.

Impact of 18-Month Soy Protein Supplementation on Steroid Hormones and Serum Biomarkers of Angiogenesis, Apoptosis, and the Growth Hormone/IGF-1 Axis: Results of a Randomized, Placebo-Controlled Trial in Males Following Prostatectomy.

Many studies have addressed the effects of dietary supplementation with soy protein on cancer risk and mortality, but there are only few randomized studies with soy in males. We used serum samples from a two-year trial of soy protein isolate supplementation in middle-aged to older males at risk of recurrence of prostate cancer after radical prostatectomy to determine soy effects on steroid hormones involved in prostate cancer (testosterone, SHBG, and estradiol) and explore the effects on biomarkers of the growth hormone/IGF-1 axis, apoptosis, and angiogenesis. Compared with a casein-based placebo, 18 mo, of consumption of 19.2 g/day of whole soy protein isolate containing 24 mg genistein-reduced circulating testosterone and SHBG, but not free testosterone, and did not affect serum concentrations of estradiol, VEGF, IGF-1, IGFBP-3, IGF-1/IGFBP-3 ratio, soluble Fas, Fas-ligand, and sFas/Fas-ligand ratio. Thus, soy protein supplementation for 18 mo, affected the androgen axis, but the effects on other cancer biomarkers remain to be more definitively determined. The study was registered at clinicaltrials.gov (NCT00765479).

Erratum: Vitamin D sufficiency enhances differentiation of patient-derived prostate epithelial organoids.

[This corrects the article DOI: 10.1016/j.isci.2020.101974.].

Soy protein supplementation in men following radical prostatectomy: a 2-year randomized, placebo-controlled clinical trial.

BACKGROUND: Many studies have addressed effects of dietary supplementation with soy protein, but most have been inconsistent and few have been long-term studies in men. OBJECTIVES: This study was a secondary analysis of body weight, blood pressure, thyroid hormones, iron status, and clinical chemistry in a 2-y trial of soy protein supplementation in middle-aged to older men. METHODS: Data were analyzed as secondary outcomes of a randomized controlled trial of dietary supplementation with 20 g/d soy protein isolate, providing 41 mg/d total isoflavones and 23 mg/d genistein, in 44- to 75-y-old men who were at risk of cancer recurrence following prostatectomy randomized to soy (n = 50) or a casein-based placebo (n  = 43). Weight, blood pressure, and blood samples were collected at baseline, every 2 mo in year 1, and every 3 mo in year 2. RESULTS: Compared with casein, soy supplementation did not affect body weight, blood pressure, serum total cholesterol, calcium, phosphorus, and thyroid hormones. Serum ferritin concentrations doubled over 2 y in both groups (117-129%), whereas hemoglobin and hematocrit increased slightly. In an exploratory subgroup analysis of soy group data, weight increased in subjects producing equol but not in nonproducers. Blood pressure was reduced in nonequol producers but not in producers. Other endpoints were not affected by equol production status. CONCLUSIONS: Soy protein supplementation for 2 y compared with a casein-based placebo did not affect body weight, blood pressure, serum total cholesterol, iron status parameters, calcium, phosphorus, and thyroid hormones. Exploratory analysis suggests that equol production status of subjects on soy may modify effects of soy on body weight and possibly blood pressure. This trial was registered at clinicaltrials.gov as NCT00765479.

Vitamin D sufficiency enhances differentiation of patient-derived prostate epithelial organoids.

Vitamin D is an essential steroid hormone that regulates systemic calcium homeostasis and cell fate decisions. The prostate gland is hormonally regulated, requiring steroids for proliferation and differentiation of secretory luminal cells. Vitamin D deficiency is associated with an increased risk of lethal prostate cancer, which exhibits a dedifferentiated pathology, linking vitamin D sufficiency to epithelial differentiation. To determine vitamin D regulation of prostatic epithelial differentiation, patient-derived benign prostate epithelial organoids were grown in vitamin D-deficient or -sufficient conditions. Organoids were assessed by phenotype and single-cell RNA sequencing. Mechanistic validation demonstrated that vitamin D sufficiency promoted organoid growth and accelerated differentiation by inhibiting canonical Wnt activity and suppressing Wnt family member DKK3. Wnt and DKK3 were also reduced by vitamin D in prostate tissue explants by spatial transcriptomics. Wnt dysregulation is a known contributor to aggressive prostate cancer, thus findings further link vitamin D deficiency to lethal disease.

Computer-Aided Diagnosis in Multiparametric MRI of the Prostate: An Open-Access Online Tool for Lesion Classification with High Accuracy.

Computer-aided diagnosis (CADx) approaches could help to objectify reporting on prostate mpMRI, but their use in many cases is hampered due to common-built algorithms that are not publicly available. The aim of this study was to develop an open-access CADx algorithm with high accuracy for classification of suspicious lesions in mpMRI of the prostate. This retrospective study was approved by the local ethics commission, with waiver of informed consent. A total of 124 patients with 195 reported lesions were included. All patients received mpMRI of the prostate between 2014 and 2017, and transrectal ultrasound (TRUS)-guided and targeted biopsy within a time period of 30 days. Histopathology of the biopsy cores served as a standard of reference. Acquired imaging parameters included the size of the lesion, signal intensity (T2w images), diffusion restriction, prostate volume, and several dynamic parameters along with the clinical parameters patient age and serum PSA level. Inter-reader agreement of the imaging parameters was assessed by calculating intraclass correlation coefficients. The dataset was stratified into a train set and test set (156 and 39 lesions in 100 and 24 patients, respectively). Using the above parameters, a CADx based on an Extreme Gradient Boosting algorithm was developed on the train set, and tested on the test set. Performance optimization was focused on maximizing the area under the Receiver Operating Characteristic curve (ROCAUC). The algorithm was made publicly available on the internet. The CADx reached an ROCAUC of 0.908 during training, and 0.913 during testing (p = 0.93). Additionally, established rule-in and rule-out criteria allowed classifying 35.8% of the malignant and 49.4% of the benign lesions with error rates of <2%. All imaging parameters featured excellent inter-reader agreement. This study presents an open-access CADx for classification of suspicious lesions in mpMRI of the prostate with high accuracy. Applying the provided rule-in and rule-out criteria might facilitate to further stratify the management of patients at risk.

Effects of Black Raspberries and Their Constituents on Rat Prostate Carcinogenesis and Human Prostate Cancer Cell Growth In Vitro.

Prostate cancer patients often use dietary supplements, such as black raspberries, which are a rich source of compounds with antioxidant and anticancer activity, particularly on gastrointestinal cancers. Feeding black raspberries inhibited mammary cancer induction in rats and growth of cancer cells in nude mice, indicating systemic bioavailability of bioactive compounds. We tested whether feeding black raspberries and its constituents would inhibit prostate cancer development. However, we did not find preventive effects in two rat prostate carcinogenesis models, even though the berry anthocyanin metabolite protocatechuic acid was detectable in their prostates. Black raspberry extract, the anthocyanin cyanidin-3-rutinoside and protocatechuic acid did not inhibit prostate cancer cell growth in vitro, but ellagic acid and its urolithin A metabolite did at high concentrations. Prostate cancer cell migration was not affected by these agents nor was growth in soft agar, except that ellagic acid reduced colony formation at physiological concentrations and protocatechuic acid at high concentrations. Low bioavailability of bioactive berry compounds and metabolites may limit exposure of tissues such as the prostate, since we found that cyanidin-3-rutinoside was not bioavailable to prostate cancer cells, but its aglycone cyanidin was and inhibited their growth. Thus, black raspberries are unlikely to prevent prostate cancer.

Effects of Black Raspberries and Their Ellagic Acid and Anthocyanin Constituents on Taxane Chemotherapy of Castration-Resistant Prostate Cancer Cells.

Cancer patients often use dietary supplements while on therapy, but little is known about interactions of supplements with cancer chemotherapy. Black raspberries (BRB) have anti-cancer effects, but have not been evaluated for interference with chemotherapy for castrate-resistant prostate cancer (CRPC). Here we studied whether BRB and some of their constituents interact with docetaxel and cabazitaxel on CRPC cells in culture and implanted into nude mice. Ellagic acid increased, but BRB extract inhibited, microtubule assembly. Ellagic acid decreased tubulin polymerization by cabazitaxel and bound to tubulin. Ellagic acid, its metabolite urolithin A, BRB extract, and the anthocyanin metabolite protocatechuic acid (PCA) did not alter cytotoxicity of taxanes. Ellagic acid inhibited drug efflux in CRPC cells, but BRB extract and PCA did not. None of these compounds altered CYP3A4 activity. Although dietary ellagic acid did not alter the tumor growth inhibition by docetaxel of xenografted 22Rv1 cells, ellagic acid has the potential to interfere with taxane chemotherapy by reducing tubulin polymerization while inhibiting P-glycoprotein drug efflux. These data are cause for concern of consuming ellagic acid during treatment for CRPC and indicate need for further research, but BRB consumption appears safe.

Lack of combination effects of soy isoflavones and taxane chemotherapy of castration-resistant prostate cancer.

BACKGROUND: Patients with cancer, including prostate cancer, often use dietary supplements, such as soy or isoflavones, before, during, or after therapy. There is little information about possible interactions between supplements and cancer chemotherapy. There are some reports suggesting enhancement by genistein of taxane chemotherapy for castrate-resistant prostate cancer (CRPC). METHODS: We investigated whether physiologically attainable concentrations of soy isoflavones (≤10 µM) interact with taxanes on growth inhibition of CRPC cells in vitro and in vivo in nude mice exposed via the diet, on microtubule disassembly in vitro, and on P-glycoprotein-mediated drug efflux in 22Rv1 cells and CYP3A4 activity in microsomes. RESULTS: Genistein, daidzein, and equol did not affect growth of VCaP, 22Rv1, C4-2, and PC-3 CRPC cells or growth inhibition of these cells by docetaxel and cabazitaxel. These isoflavones did not inhibit microtubule disassembly in vitro or inhibit the microtubule effects of taxanes and genistein did not bind substantially to microtubules. Genistein considerably inhibited P-glycoprotein-mediated drug efflux in 22Rv1 cells and CYP3A4 activity in microsomes. However, dietary supplementation with genistein at 250 and 500 ppm did not affect the tumor growth inhibiting effect of docetaxel on 22Rv1 cells xenografted in nude mice. CONCLUSIONS: Our results with relevant cell models and clinically achievable concentrations of soy isoflavones do not support the notion that genistein or other soy isoflavones can enhance the effects of taxane chemotherapy in CRPC cell and xenograft models. Yet, the inhibitory effects of genistein on drug efflux in 22Rv1 cells and on microsomal CYP3A4 activity raise the possibility that genistein can affect taxane effects on CRPC cells in other circumstances than those we studied, which merits further research.

A Novel l-Asparaginase with low l-Glutaminase Coactivity Is Highly Efficacious against Both T- and B-cell Acute Lymphoblastic Leukemias In Vivo.

Acute lymphoblastic leukemia (ALL) is the most common type of pediatric cancer, although about 4 of every 10 cases occur in adults. The enzyme drug l-asparaginase serves as a cornerstone of ALL therapy and exploits the asparagine dependency of ALL cells. In addition to hydrolyzing the amino acid l-asparagine, all FDA-approved l-asparaginases also have significant l-glutaminase coactivity. Since several reports suggest that l-glutamine depletion correlates with many of the side effects of these drugs, enzyme variants with reduced l-glutaminase coactivity might be clinically beneficial if their antileukemic activity would be preserved. Here we show that novel low l-glutaminase variants developed on the backbone of the FDA-approved Erwinia chrysanthemi l-asparaginase were highly efficacious against both T- and B-cell ALL, while displaying reduced acute toxicity features. These results support the development of a new generation of safer l-asparaginases without l-glutaminase activity for the treatment of human ALL.Significance: A new l-asparaginase-based therapy is less toxic compared with FDA-approved high l-glutaminase enzymes Cancer Res; 78(6); 1549-60. ©2018 AACR.

Flaxseed suppressed prostatic epithelial proliferation in a rat model of benign prostatic hyperplasia.

Benign prostatic hyperplasia (BPH), a disease occurring frequently among elderly males, is a slow progressive enlargement of the fibromuscular and epithelial structures of the prostate gland. Dietary factors may influence the prostate and exert an influence on prostatic growth and disease. The current study was undertaken to investigate the protective effect of dietary flaxseed supplementation against testosterone-induced prostatic hyperplasia in male rats. Forty male Wistar rats were divided into 5 groups: (1) untreated control; (2) treatment with testosterone propionate (TP) to induce prostate enlargement; (3) TP-treated group fed a diet containing 5% milled flaxseed; (4) TP-treated group fed a diet containing 10% milled flaxseed; and (5) TP-treated group fed a diet containing 20 ppm finasteride. Treatment with TP significantly increased the absolute and relative weights of different prostatic lobes, serum testosterone (T), and testosterone/estradiol ratio, as well as prostatic vascular endothelial growth factor (VEGF) expression, RNA synthesis per cell, and epithelial cell proliferation, detected as Ki67 labeling. Histopathological examination did not reveal marked differences in acinar morphology in ventral prostate, whereas morphometric analysis showed significantly increased epithelial cell height. Co-administration of flaxseed or finasteride with TP significantly reduced prostatic VEFG, epithelial cell proliferation, and RNA/DNA ratio, along with a significant increase in serum T and testosterone/estradiol ratio compared with TP-only-treated rats. Our results indicate that flaxseed, similar to the 5α-reductase inhibitor finasteride, blocked TP-induced prostate enlargement in a rat model of BPH, likely through suppression of prostatic VEFG and cellular proliferation.

L-selenomethionine does not protect against testosterone plus 17ß-estradiol-induced oxidative stress and preneoplastic lesions in the prostate of NBL rats.

Previous animal studies examining dietary selenium effects on prostatic carcinogenesis did not show preventive benefit, including 1 study in a rat model involving testosterone (T) and estradiol (E2)-induced prostatic oxidative stress. Here, we examined modulation of T + E2-induced prostatic oxidative stress, dysplasia, and inflammation by L-selenomethionine at 1.5 or 3.0 mg selenium/kg in NIH-07 diet in Noble (Nbl)/Crl rats treated with T + E2 for 16 wk. Hormone treatment increased immunohistochemical staining for 8-hydroxydeoxyguanosine (8-OHdG) in the prostatic sites of T + E2-induced preneoplasia (P < 0.05), but selenomethionine did not attenuate 8-OHdG staining and dysplasia in the lateral prostate. Glutathione-peroxidase activity (P < 0.05) and mRNA expression were induced by T + E2 (P < 0.0001) but not changed by selenomethionine. Selenomethionine did not cause significant responses in expression and activity of glutathione-peroxidase and MnSOD, except for a reduction of MnSOD protein expression in the lateral prostate (P < 0.01). The absence of reduction of oxidative stress and dysplasia and the minimal effects on antioxidant enzymes caused by selenomethionine are consistent with the null effects observed in selenium supplementation animal studies and clinical trials. Significant (P < 0.01) opposite apoptosis/cell proliferation balance responses to selenomethionine and to T + E2 occurred in the lateral and dorsal prostate, explaining why T + E2 induces lesions selectively in the lateral lobe of NBL rats.

Effect of soy protein isolate supplementation on biochemical recurrence of prostate cancer after radical prostatectomy: a randomized trial.

IMPORTANCE: Soy consumption has been suggested to reduce risk or recurrence of prostate cancer, but this has not been tested in a randomized trial with prostate cancer as the end point. OBJECTIVE: To determine whether daily consumption of a soy protein isolate supplement for 2 years reduces the rate of biochemical recurrence of prostate cancer after radical prostatectomy or delays such recurrence. DESIGN, SETTING, AND PARTICIPANTS: Randomized, double-blind trial conducted from July 1997 to May 2010 at 7 US centers comparing daily consumption of a soy protein supplement vs placebo in 177 men at high risk of recurrence after radical prostatectomy for prostate cancer. Supplement intervention was started within 4 months after surgery and continued for up to 2 years, with prostate-specific antigen (PSA) measurements made at 2-month intervals in the first year and every 3 months thereafter. INTERVENTION: Participants were randomized to receive a daily serving of a beverage powder containing 20 g of protein in the form of either soy protein isolate (n=87) or, as placebo, calcium caseinate (n=90). MAIN OUTCOMES AND MEASURES: Biochemical recurrence rate of prostate cancer (defined as development of a PSA level of ≥0.07 ng/mL) over the first 2 years following randomization and time to recurrence. RESULTS: The trial was stopped early for lack of treatment effects at a planned interim analysis with 81 evaluable participants in the intervention group and 78 in the placebo group. Overall, 28.3% of participants developed biochemical recurrence within 2 years of entering the trial (close to the a priori predicted recurrence rate of 30%). Among these, 22 (27.2%) occurred in the intervention group and 23 (29.5%) in the placebo group. The resulting hazard ratio for active treatment was 0.96 (95% CI, 0.53-1.72; log-rank P = .89). Adherence was greater than 90% and there were no apparent adverse events related to supplementation. CONCLUSION AND RELEVANCE: Daily consumption of a beverage powder supplement containing soy protein isolate for 2 years following radical prostatectomy did not reduce biochemical recurrence of prostate cancer in men at high risk of PSA failure. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00765479.

Characterization of soy-based changes in Wnt-frizzled signaling in prostate cancer.

BACKGROUND: A soy-based diet has been associated with a decreased risk of prostate cancer through its anti-androgenic effects. Because the Wnt/beta catenin pathway has been associated with aggressive prostate cancer, we have sought to further evaluate this pathway with respect to soy protein and prostate cancer. MATERIALS AND METHODS: Previously we have treated rat and human prostate cancer cell lines with soy protein isolates or purified genistein and used gene expression profiling and cross species analysis to identify genes with similar expression changes. One pathway that was identified included the Wnt/beta-cantenin pathway. Here the initial data are evaluated and extended with immunohistochemistry in human prostate cancer, and Western blotting, small interfering ribonucleic acid (siRNA) inhibition and bromodeoxyuridine (BrDU) labeling in prostate cancer cell lines. RESULTS: The Wnt/beta-catenin pathway is modulated by both soy protein isolates and genistein in the genomic results. Immunohistochemistry demonstrated staining of Wnt pathway component molecules, in particular frizzled 3, glycogen synthase kinase 3 (GSK-3), and beta-catenin, in prostate tumors. Western blotting noted increased GSK3 and decreased expression of beta-catenin in soy treated prostate cancer PC3 cells. Supporting this finding, siRNA blocking of GSK3 accelerated growth whereas inhibition of frizzled 3 suppressed growth based on growth curves and BrDU labeling. CONCLUSION: Soy protein appears to regulate prostate cancer via the Wnt/beta-catenin pathway. These data demonstrate that the effect of soy protein effect on prostate cancer may occur through the frizzled 3 receptor with activation of GSK3 leading to increased degradation of beta-catenin and cell growth.