The influence of dietary and environmental factors on prostate cancer risk

LRP5 competes for SPOP binding to enhance tumorigenesis mediated by Daxx and PD-L1 in prostate cancer

Genetic factors coordinate with environmental factors to drive the pathogenesis of prostate adenocarcinoma (PRAD). SPOP is one of the most mutated genes and LRP5 mediates lipid metabolism that is abnormally altered in PRAD. Here, we investigated the potential cross-talk between SPOP and LRP5 in PRAD. We find a negative correlation between SPOP and LRP5 proteins in PRAD. SPOP knockdown increased LRP5 protein while SPOP overexpression resulted in LRP5 reduction that was fully rescued by proteasome inhibitors. LRP5 intracellular tail has SPOP binding site and the direct interaction between LRP5 and SPOP was confirmed by Co-IP and GST-pulldown. Moreover, LRP5 competed with Daxx for SPOP-mediated degradation, establishing a dynamic balance among SPOP, LRP5 and Daxx. Overexpression of LRP5 tail could shift this balance to enhance Daxx-mediated transcriptional inhibition, and inhibit T cell activity in a co-culture system. Further, we generated human and mouse prostate cancer cell lines expressing SPOP variants (F133V, A227V, R368H). SPOP-F133V and SPOP-A227V have specific effects in up-regulating the protein levels of PD-1 and PD-L1. Consistently, SPOP-F133V and SPOP-A227V show robust inhibitory effects on T cells compared to WT SPOP in co-culture. This is further supported by the mouse syngeneic model showing that SPOP-F133V and SPOP-A227V enhance tumorigenesis of prostate cancer in in-vivo condition. Taken together, our study provides evidence that SPOP-LRP5 crosstalk plays an essential role, and the genetic variants of SPOP differentially modulate the expression and activity of immune checkpoints in prostate cancer.

Metabolism and biomarkers of heterocyclic aromatic amines in humans

Heterocyclic aromatic amines (HAAs) form during the high-temperature cooking of meats, poultry, and fish. Some HAAs also arise during the combustion of tobacco. HAAs are multisite carcinogens in rodents, inducing cancer of the liver, gastrointestinal tract, pancreas, mammary, and prostate glands. HAAs undergo metabolic activation by N-hydroxylation of the exocyclic amine groups to produce the proposed reactive intermediate, the heteroaryl nitrenium ion, which is the critical metabolite implicated in DNA damage and genotoxicity. Humans efficiently convert HAAs to these reactive intermediates, resulting in HAA protein and DNA adduct formation. Some epidemiologic studies have reported an association between frequent consumption of well-done cooked meats and elevated cancer risk of the colorectum, pancreas, and prostate. However, other studies have reported no associations between cooked meat and these cancer sites. A significant limitation in epidemiology studies assessing the role of HAAs and cooked meat in cancer risk is their reliance on food frequency questionnaires (FFQ) to gauge HAA exposure. FFQs are problematic because of limitations in self-reported dietary history accuracy, and estimating HAA intake formed in cooked meats at the parts-per-billion level is challenging. There is a critical need to establish long-lived biomarkers of HAAs for implementation in molecular epidemiology studies designed to assess the role of HAAs in health risk. This review article highlights the mechanisms of HAA formation, mutagenesis and carcinogenesis, the metabolism of several prominent HAAs, and the impact of critical xenobiotic-metabolizing enzymes on biological effects. The analytical approaches that have successfully biomonitored HAAs and their biomarkers for molecular epidemiology studies are presented.

Induction of proliferative and mutagenic activity by benzo(a)pyrene in PC-3 cells via JAK2/STAT3 pathway

Environmental carcinogen benzo(a)pyrene (BaP) is a representative compound of polycyclic aromatic hydrocarbons (PAHs). BaP is strongly associated with prostate carcinogenesis. However, the molecular mechanism of BaP in development of prostate carcinoma remains largely unknown. The aim of this study was to investigate the effect and mechanism of BaP on the development in prostate cancer. PC-3 cells were exposed to different concentrations of BaP for 24, 48, 72 h, respectively. We analyzed the effect of BaP on PC-3 cell viability, cell cycle, DNA strand breaks, mutagenic activity, and migration. The expression of associated regulatory genes and the effect of JAK2/STAT3 signaling were also measured to explore the relationships among BaP metabolism, the JAK2/STAT3 pathway and proliferative activity in PC-3 cells. We observed significant effects on proliferation, DNA strand breaks and mutagenic activity after BaP exposure in PC-3 cells, and inhibitors of CYP1 and the AhR transcription factor α -naphthoflavone (ANF) and CH223191 treatment clearly reduced both cell survival and mutagenesis associated with BaP exposure. Reduction in G0-G1 phase population and elevation in S phase were observed after BaP exposure. Migratory cells for PC-3 were significantly increased. The results were further confirmed by the expression of mRNA levels in the significant increments of Snail, Slug, MMP-9, CYP1A1, CYP1B1, CycilnD1, CDK4 and significant reduction of E-cadherin. Significant enhancements were found in the expression of JAK2, STAT3 after BaP treatment. Additionally, activator IL-6 significantly enhanced the effect of BaP on cell survival, mutagenic activity, Cyclin D1, CDK4, Snail, and JAK2/STAT3 expression in PC-3 cells. Significant reductions in cell survival, mutagenic activity, Cyclin D1, CDK4, Snail, and JAK2/STAT3 expression were found after inhibitor AG490, ANF and CHJ223191 treatment. These findings reveal that BaP enhances the proliferative and mutagenic activity via JAK2-STAT3 pathway in PC-3 cells, and provide the additional evidence to understand the crucial role of BaP in prostate cancer carcinogenesis.

Dietary Carcinogens and DNA Adducts in Prostate Cancer

Prostate cancer (PC) is the most commonly diagnosed non-cutaneous cancer and the second leading cause of cancer-related to death in men. The major risk factors for PC are age, family history, and African American ethnicity. Epidemiological studies have reported large geographical variations in PC incidence and mortality, and thus lifestyle and dietary factors influence PC risk. High fat diet, dairy products, alcohol and red meats, are considered as risk factors for PC. This book chapter provides a comprehensive, literature-based review on dietary factors and their molecular mechanisms of prostate carcinogenesis. A large portion of our knowledge is based on epidemiological studies where dietary factors such as cancer promoting agents, including high-fat, dairy products, alcohol, and cancer-initiating genotoxicants formed in cooked meats have been evaluated for PC risk. However, the precise mechanisms in the etiology of PC development remain uncertain. Additional animal and human cell-based studies are required to further our understandings of risk factors involved in PC etiology. Specific biomarkers of chemical exposures and DNA damage in the prostate can provide evidence of cancer-causing agents in the prostate. Collectively, these studies can improve public health research, nutritional education and chemoprevention strategies.

The Mediterranean Diet Reduces the Risk and Mortality of the Prostate Cancer: A Narrative Review

Prostate cancer is the second most common cancer in the world among men, and is the fifth most common cause of cancer death among men. The aim of our review was to analyze observational and case–control studies to point out the effects of overweight and diets components on the cancer risk, particularly on risk of prostate cancer, and the effect of the Mediterranean diet (MD) on the reduction of risk and mortality of prostate cancer. It is known that incidence and progression of cancer is multifactorial. Cancer of the large bowel, breast, endometrium, and prostate are due also to a high body mass index and to high consumption of high carcinogenic dietary factors, as red and processed meat or saturated fats rich foods, and to a low consumption of vegetables and fruits. Previous meta-analysis suggested that high adherence to diet model based on the traditional MD pattern gives a significant protection from incidence and mortality of cancer of all types. The main component of the MD is olive oil, consumed in high amount by Mediterranean basin populations. In addition, phenolic compounds exert some strong chemo-preventive effects, which are due to several mechanisms, including both antioxidant effects and actions on cancer cell signaling and cell cycle progression and proliferation. The protective effect of the MD against the prostate cancer is also due to the high consumption of tomato sauce. Lycopene is the most relevant functional component in tomatoes; after activating by the cooking of tomato sauce, it exerts antioxidant properties by acting in the modulation of downregulation mechanisms of the inflammatory response. MD, therefore, represents a healthy dietary pattern in the context of a healthy lifestyle habits. In conclusion, our narrative review allows us to reaffirm how nutritional factors play an important role in cancer initiation and development, and how a healthy dietary pattern represented by MD and its components, especially olive oil, could exert a protective role by the development and progression of prostate cancer.

Spatial variations in ambient ultrafine particle concentrations and the risk of incident prostate cancer: A case-control study

BACKGROUND

Diesel exhaust contains large numbers of ultrafine particles (UFPs, <0.1µm) and is a recognized human carcinogen. However, epidemiological studies have yet to evaluate the relationship between UFPs and cancer incidence.

METHODS

We conducted a case-control study of UFPs and incident prostate cancer in Montreal, Canada. Cases were identified from all main Francophone hospitals in the Montreal area between 2005 and 2009. Population controls were identified from provincial electoral lists of French Montreal residents and frequency-matched to cases using 5-year age groups. UFP exposures were estimated using a land use regression model. Exposures were assigned to residential locations at the time of diagnosis/recruitment as well as approximately 10-years earlier to consider potential latency between exposure and disease onset. Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated per interquartile range (IQR) increase in UFPs (approximately 4000 particles/cm³) using logistic regression models adjusting for individual-level and ecological covariates.

RESULTS

Ambient UFP concentrations were associated with an increased risk of prostate cancer (OR=1.10, 95% CI: 1.01, 1.19) in fully adjusted models when exposures were assigned to residences 10-years prior to diagnosis. This risk estimate increased slightly (OR=1.17, 95% CI; 1.01, 1.35) when modeled as a non-linear natural spline function. A smaller increased risk (OR=1.04, 95% CI: 0.97, 1.11) was observed when exposures were assigned to residences at the time of diagnosis.

CONCLUSIONS

Exposure to ambient UFPs may increase the risk of prostate cancer. Future studies are needed to replicate this finding as this is the first study to evaluate this relationship.

Minireview: the molecular and genomic basis for prostate cancer health disparities

Despite more aggressive screening across all demographics and gradual declines in mortality related to prostate cancer (PCa) in the United States, race disparities persist. For African American men (AAM), PCa is more often an aggressive disease showing increased metastases and greater PCa-related mortality compared with European American men. The earliest research points to how distinctions are likely the result of a combination of factors, including ancestry genetics and lifestyle variables. More recent research considers that cancer, although influenced by external forces, is ultimately a disease primarily driven by aberrations observed in the molecular genetics of the tumor. Research studying PCa predominantly from European American men shows that indolent and advanced or metastatic prostate tumors have distinguishing molecular genomic make-ups. Early yet increasing evidence suggests that clinically distinct PCa from AAM also display molecular distinctions. It is reasonable to predict that further study will reveal molecular subtypes and various frequencies for PCa subtypes among diverse patient groups, thereby providing insight as to the genomic lesions and gene signatures that are functionally implicated in carcinogenesis or aggressive PCa in AAM. That knowledge will prove useful in developing strategies to predict who will develop advanced PCa among AAM and will provide the rationale to develop effective individualized treatment strategies to overcome disparities.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-DNA adducts in benign prostate and subsequent risk for prostate cancer

Despite convincing evidence that 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)--a heterocyclic amine generated by cooking meats at high temperatures--is carcinogenic in animal models, it remains unclear whether PhIP exposure leads to increased cancer risk in humans. PhIP-DNA adduct levels were measured in specimens from 534 prostate cancer case-control pairs nested within a historical cohort of men with histopathologically benign prostate specimens. We estimated the overall and race-stratified risk of subsequent prostate cancer associated with higher adduct levels. PhIP-DNA adduct levels in benign prostate were significantly higher in Whites than African Americans (0.274 optical density units (OD) ±0.059 vs. 0.256 OD ±0.054; p<0.0001). Prostate cancer risk for men in the highest quartile of PhIP-DNA adduct levels was modestly increased [odds ratio (OR) = 1.25; 95% confidence interval (CI) = 0.76-2.07]. In subset analyses, the highest risk estimates were observed in White patients diagnosed more than 4 years after cohort entry (OR = 2.74; 95% CI = 1.01-7.42) or under age 65 (OR = 2.80; 95% CI = 0.87-8.97). In Whites, cancer risk associated with high-grade prostatic intraepithelial neoplasia combined with elevated PhIP-DNA adduct levels (OR = 3.89; 95% CI = 1.56-9.73) was greater than risk associated with either factor alone. Overall, elevated levels of PhIP-DNA adducts do not significantly increase prostate cancer risk. However, our data show that White men have higher PhIP-DNA adduct levels in benign prostate tissue than African American men, and suggest that in certain subgroups of White men high PhIP-DNA adduct levels may predispose to an increased risk for prostate cancer.

Red meat and poultry, cooking practices, genetic susceptibility and risk of prostate cancer: results from a multiethnic case-control study

Red meat, processed and unprocessed, has been considered a potential prostate cancer (PCA) risk factor; epidemiological evidence, however, is inconclusive. An association between meat intake and PCA may be due to potent chemical carcinogens that are generated when meats are cooked at high temperatures. We investigated the association between red meat and poultry intake and localized and advanced PCA taking into account cooking practices and polymorphisms in enzymes that metabolize carcinogens that accumulate in cooked meats. We analyzed data for 1096 controls, 717 localized and 1140 advanced cases from the California Collaborative Prostate Cancer Study, a multiethnic, population-based case-control study. We examined nutrient density-adjusted intake of red meat and poultry and tested for effect modification by 12 SNPs and 2 copy number variants in 10 carcinogen metabolism genes: GSTP1, PTGS2, CYP1A2, CYP2E1, EPHX1, CYP1B1, UGT1A6, NAT2, GSTM1 and GSTT1. We observed a positive association between risk of advanced PCA and high intake of red meat cooked at high temperatures (trend P = 0.026), cooked by pan-frying (trend P = 0.035), and cooked until well-done (trend P = 0.013). An inverse association was observed for baked poultry and advanced PCA risk (trend P = 0.023). A gene-by-diet interaction was observed between an SNP in the PTGS2 gene and the estimated levels of meat mutagens (interaction P = 0.008). Our results support a role for carcinogens that accumulate in meats cooked at high temperatures as potential PCA risk factors, and may support a role for heterocyclic amines (HCAs) in PCA etiology.

Elevated polycyclic aromatic hydrocarbon-DNA adducts in benign prostate and risk of prostate cancer in African Americans

Carcinogen-DNA adducts, a marker of DNA damage, are capable of inducing mutations in oncogenes and tumor suppressor genes, resulting in carcinogenesis. We have shown previously that polycyclic aromatic hydrocarbon (PAH)-DNA adduct levels in prostate cancer cases vary by cellular histology and that higher adduct levels are associated with biochemical recurrence. A nested case-control study was conducted in a historical cohort of 6692 men with histopathologically benign prostate specimens. PAH-DNA adduct levels were determined by immunohistochemistry in benign prostate specimens from 536 prostate cancer case-control pairs (59% White and 41% African American). We estimated the overall and race-stratified risk of subsequent prostate cancer associated with higher adduct levels. Prostate cancer risk for men with elevated adduct levels (defined as greater than control group median) was slightly increased [odds ratio (OR) = 1.28, 95% confidence interval (CI) = 0.98-1.67, P = 0.07]. After race stratification, elevated adduct levels were significantly associated with increased risk in African American men (OR = 1.56, CI = 1.00-2.44, *P = 0.05) but not White men (OR = 1.14, CI = 0.82-1.59, P = 0.45). Elevated PAH-DNA adduct levels were significantly associated with 60% increased risk of prostate cancer among cases diagnosed 1-4 years after cohort entry (OR = 1.60, CI = 1.07-2.41) with a greater risk observed in African Americans within the first 4 years of follow-up (OR = 4.71, CI = 1.97-11.26, ***P = 0.0005). Analyses stratified by age or tumor grade revealed no additional significant heterogeneity in risk. Increased prostate cancer risk associated with high PAH-DNA adduct levels in benign prostate was found only in African Americans; risk was greatest within 4 years of follow-up, possibly reflecting a carcinogenic process not yet histologically detectable.

Environmental factors in causing human cancers: emphasis on tumorigenesis

The environment and dietary factors play an essential role in the etiology of cancer. Environmental component is implicated in ~80 % of all cancers; however, the causes for certain cancers are still unknown. The potential players associated with various cancers include chemicals, heavy metals, diet, radiation, and smoking. Lifestyle habits such as smoking and alcohol consumption, exposure to certain chemicals (e.g., polycyclic aromatic hydrocarbons, organochlorines), metals and pesticides also pose risk in causing human cancers. Several studies indicated a strong association of lung cancer with the exposure to tobacco products and asbestos. The contribution of excessive sunlight, radiation, occupational exposure (e.g., painting, coal, and certain metals) is also well established in cancer. Smoking, excessive alcohol intake, consumption of an unhealthy diet, and lack of physical activity can act as risk factors for cancer and also impact the prognosis. Even though the environmental disposition is linked to cancer, the level and duration of carcinogen-exposure and associated cellular and biochemical aspects determine the actual risk. Modulations in metabolism and DNA adduct formation are considered central mechanisms in environmental carcinogenesis. This review describes the major environmental contributors in causing cancer with an emphasis on molecular aspects associated with environmental disposition in carcinogenesis.

Chronic bacterial inflammation induces prostatic intraepithelial neoplasia in mouse prostate

Background:

Although the aetiology of prostate cancer remains unknown, we hypothesised that chronic bacterial insult has a major role in prostate carcinogenesis.

Methods:

Male C3H/HeOuJ mice, infected with phosphate-buffered saline or Escherichia coli bacteria, were killed at 5 days, or at 12 or 26 weeks. Harvested prostate tissues were evaluated for inflammatory responses and immunostained for neoplastic transformation markers.

Results:

All infected mice developed bacterial prostatitis. Control mice had no prostate infections or inflammation. Mice infected for 5 days showed foci of acute inflammation with infiltrating neutrophils and epithelial necrotic debris in the prostatic glandular lumen. All mice infected for 12 weeks had evidence of chronic inflammation with dense inflammatory infiltrates in the stroma. The prostatic epithelium showed varying degrees of atypical hyperplasia with increased epithelial cell layers and cytological atypia. At 26 weeks, the dysplastic changes were more pronounced and mimicked a prostatic intraepithelial neoplasia and high-grade dysplasia. Prostatic glands exhibiting reactive dysplasia had a stronger staining for oxidative DNA damage, increased epithelial cell proliferation, and a decrease in androgen receptor, GSTP1, p27^Kip1, and PTEN expression, when compared with control prostate glands.

Conclusion:

These data demonstrate that chronic inflammation induces focal prostatic glandular atypia and suggest a potential linkage between inflammation and prostatic neoplasia.

Quantification of phase I/II metabolizing enzyme gene expression and polycyclic aromatic hydrocarbon-DNA adduct levels in human prostate

BACKGROUND

Studies of migrant populations suggest that dietary and/or environmental factors play a crucial role in the etiology of prostatic adenocarcinoma (CaP). The human prostate consists of the peripheral zone (PZ), transition zone (TZ), and central zone (CZ); CaP occurs most often in the PZ.

METHODS

To investigate the notion that an underlying differential expression of phase I/II genes, and/or the presence of polycyclic aromatic hydrocarbon (PAH)-DNA adducts might explain the elevated PZ susceptibility, we examined prostate tissues (matched tissue sets consisting of PZ and TZ) from men undergoing radical retropubic prostatectomy for CaP (n = 26) or cystoprostatectomy (n = 1). Quantitative gene expression analysis was employed for cytochrome P450 (CYP) isoforms CYP1A1, CYP1B1, and CYP1A2, as well as N-acetyltransferase 1 and 2 (NAT1 and NAT2) and catechol-O-methyl transferase (COMT).

RESULTS

CYP1B1, NAT1, and COMT were expressed in all tissue sets; levels of CYP1B1 and NAT1 were consistently higher in the PZ compared to TZ. Immunohistochemistry confirmed the presence of CYP1B1 (nuclear-associated and primarily in basal epithelial cells) and NAT1. Normal tissue from 23 of these aforementioned 27 matched tissue sets was analyzed for PAH-DNA adduct levels using antiserum elicited against DNA modified with r7,t8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydro-benzo[a]pyrene (BPDE). PAH-DNA adduct levels were highest in glandular epithelial cells, but a comparison of PZ and TZ showed no significant differences.

CONCLUSION

Although expression of activating and/or detoxifying enzymes may be higher in the PZ, PAH-DNA adduct levels appear to be similar in both zones. Therefore, factors other than PAH-DNA adducts may be responsible for promotion of tumor formation in the human prostate.

Polycyclic aromatic hydrocarbon--DNA adducts in prostate and biochemical recurrence after prostatectomy

PURPOSE

DNA adduct levels may be influenced by metabolic activity, DNA repair capabilities, and genomic integrity, all of which play a role in cancer progression.

EXPERIMENTAL DESIGN

To determine if elevated DNA adducts are a marker for prostate cancer progression, we measured polycyclic aromatic hydrocarbon-DNA adducts by immunohistochemistry in prostate cells of 368 surgical prostate cancer patients treated at the Henry Ford Hospital in Detroit, Michigan, between September 1999 and July 2004. Patients were followed up to 5 years after surgery with relative risk for biochemical recurrence (BCR) estimated with a Cox proportional hazards model that adjusted for standard clinical risk factors.

RESULTS

At 1 year of follow-up, patients with adduct levels above the median in tumor cells [hazard ratio (HR), 2.40; 95% confidence interval (95% CI), 1.10-5.27] and nontumor cells (HR, 3.22; 95% CI, 1.40-7.39) had significant increased risk of BCR, but these HRs decreased to 1.12 (95% CI, 0.68-1.83) and 1.46 (95% CI, 0.89-2.41) in tumor and nontumor cells at 5 years postsurgery. When we restricted our analysis to patients with advanced-stage (III+) disease, those with high adduct levels in either tumor (53.5% versus 30.2%; P = 0.07) or nontumor (55.2% versus 28.6%; P = 0.02) cells had BCR rates almost 2-fold higher. In race-stratified analyses, the greatest risk of BCR associated with high adduct levels (in nontumor cells) was for African American patients younger than 60 years old (HR, 3.79; 95% CI, 1.01-14.30).

CONCLUSIONS

High polycyclic aromatic hydrocarbon-DNA adduct levels in nontumor prostate cells are most strongly associated with BCR between 1 and 2 years after surgery and in patient subsets defined by younger age, advanced tumor stage, and African American race.

Correlations of dietary patterns with prostate health

Both genetic and environmental influences may be involved in etiology of prostate health and prostate cancer. These include ethnic origin, family history, smoking, and diet. Adiposity and excess energy intake are potentially distinct risk factors and positive associations with prostate cancer risk for both were observed among case-control and cohort studies. Some epidemiological studies support an association between dietary fat, particularly saturated or animal fats, and prostate cancer risk. Of these, several suggest reduced risk with low-fat diets high in n-3 fatty acids and increased risk with high-fat diets rich in n-6 fatty acids. Others suggested association with higher meat intake, possibly due to heterocyclic amines and polycyclic aromatic hydrocarbons, produced during grilling or frying. Positive association of prostate cancer risk with dairy intake could involve alpha-methylacyl-CoA racemase activity (required for beta-oxidation of phytanic acid present in dairy products and red meat) or the suppression of vitamin D activity by calcium. Inverse associations were observed with dietary intake of plant foods. These include cereals, soy products, and fruit and vegetable sources of carotenoids. Numerous plant constituents may act synergistically in the prevention and inhibition of prostate disorders. These diet-risk associations may lead to future individualized diet recommendations based upon genetic polymorphisms.

Racial differences in clinical and pathological associations with PhIP-DNA adducts in prostate

African-American men have a higher dietary intake of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), which is the most abundant heterocyclic amine in cooked meats and is carcinogenic in rat prostate through the formation of DNA adducts. To determine the clinical and demographic factors associated with PhIP-DNA adduct levels, the biologically effective dose of PhIP in human prostate, we immunohistochemically measured PhIP-DNA adducts in a study of 162 Caucasian and 102 African-American men who underwent radical prostatectomy for prostate cancer. A strong correlation between PhIP-DNA adduct levels in prostate tumor and adjacent non-tumor cells was observed (rho = 0.62; p < 0.0001); however, non-tumor cells had significantly higher adduct levels compared with tumor (0.167 optical density (OD) units +/- 0.043 vs. 0.104 OD +/- 0.027; p < 0.0001). Race was not associated with PhIP-DNA adduct levels in either tumor or non-tumor cells, but race-specific associations were observed. In prostate tumor and non-tumor cells, tumor volume had the strongest association with PhIP-DNA adducts in Caucasians, whereas in African-Americans prostate volume was most strongly associated with adduct levels in tumor cells and advanced Gleason grade had the strongest association in non-tumor cells. In race interaction models, while the only statistically significant interaction was between African-American race and advanced Gleason grade in non-tumor cells (beta = 0.029; p = 0.02), in tumor cells we observed opposite effects by race (positive for African-Americans, negative for Caucasians) for older age and high PSA levels at diagnosis. In conclusion, while PhIP-DNA adduct levels in prostate cells do not vary significantly by race, our results suggest that PhIP exposure may have stronger effects on prostate tumor differentiation in African-American men.

Associations between smoking, polymorphisms in polycyclic aromatic hydrocarbon (PAH) metabolism and conjugation genes and PAH-DNA adducts in prostate tumors differ by race

Polycyclic aromatic hydrocarbon (PAH)-DNA adducts may induce mutations that contribute to carcinogenesis. We evaluated potential associations between smoking and polymorphisms in PAH metabolism [CYP1A1 Ile 462Val, CYP1B1 Ala 119Ser and Leu 432Val, microsomal epoxide hydrolase (mEH) Tyr 113His and His139Arg, CYP3A4 A(-392)G] and conjugation [glutathione S-transferase (GST) M1 null deletion, GSTP1 Ile 105Val] genes and PAH-DNA adduct levels (measured by immunohistochemistry) in tumor and nontumor prostate cells in 400 prostate cancer cases. Although no statistically significant associations were observed in the total sample, stratification by ethnicity revealed that Caucasian ever smokers compared with nonsmokers had higher adduct levels in tumor cells (mean staining intensity in absorbance units +/- SE, 0.1748 +/- 0.0052 versus 0.1507 +/- 0.0070; P = 0.006), and Caucasians carrying two mEH 139Arg compared with two 139His alleles had lower adducts in tumor (0.1320 +/- 0.0129 versus 0.1714 +/- 0.0059; P = 0.006) and nontumor (0.1856 +/- 0.0184 versus 0.2291 +/- 0.0085; P = 0.03) cells. African Americans with two CYP1B1 432Val compared with two 432Ile alleles had lower adducts in tumor cells (0.1600 +/- 0.0060 versus 0.1970 +/- 0.0153; P = 0.03). After adjusting for smoking status, carrying the putative "high-risk" genotype combination, the faster metabolism of PAH-epoxides to PAH-diol-epoxides (CYP1B1 432Val/Val and mEH 139Arg/Arg) with lower PAH-diol-epoxide conjugation (GSTP1 (105)Ile/Ile), was associated with increased adducts only in Caucasian nontumor cells (0.2363 +/- 0.0132 versus 0.1920 +/- 0.0157; P= 0.05). We present evidence, for the first time in human prostate that the association between smoking and PAH-DNA adducts differs by race and is modified by common genetic variants.

Differential protein expression of peroxiredoxin I and II by benzo(a)pyrene and quercetin treatment in 22Rv1 and PrEC prostate cell lines

Mechanisms of benzo(a)pyrene (BaP)-mediated toxicity and chemopreventative potential of quercetin in prostate cancer are poorly understood. Two-dimensional gel electrophoresis was used to map the differences in protein expression in BaP (1 microM)- and quercetin (5 microM)-treated 22Rv1 human prostate cancer cells. As compared to DMSO, 26 proteins in BaP and 41 proteins in quercetin were found to be differentially expressed (+/-2-fold). Western blots confirmed that BaP increased peroxiredoxin (Prx) Prx I and decreased Prx II in 22Rv1 cells. Similar results were found in PrEC normal prostate epithelial cells. Quercetin (up to 10 microM) upregulated Prx II without altering Prx I levels in 22Rv1 cells whereas in PrEC cells, it did not alter the constitutive protein expression of Prx I or II. The lack of quercetin-mediated changes in Prx expression suggests that quercetin does not interfere with H(2)O(2) levels, and thus may have no deleterious effect in normal prostate cells. Quercetin inhibited both BaP-mediated effects on Prx I and II in 22Rv1 cells. In PrEC cells, quercetin inhibited BaP-mediated upregulation of Prx I and had tendency to neutralize BaP-mediated downregulation of Prx II. Quercetin also inhibited BaP-induced concentrations of reactive oxygen species in both 22Rv1 and PrEC cells. These results suggest that Prx I and II may be involved in BaP-mediated toxicity and the potential chemopreventative mechanisms of quercetin.

Chronic bacterial infection and inflammation incite reactive hyperplasia in a mouse model of chronic prostatitis

BACKGROUND

Chronic inflammation is postulated to contribute to prostate carcinogenesis. We developed a mouse model of chronic prostatitis to test whether infection-induced chronic inflammation would incite reactive changes in prostatic epithelium.

METHODS

Prostate tissues harvested from either phosphate-buffered saline (PBS) or E. coli-infected mice were evaluated for histological changes and immunostained for markers of oxidative stress and epithelial cell proliferation.

RESULTS

As compared to PBS-treated controls, mice infected with E. coli bacteria for 5 days showed foci of uniformly acute inflammation in the glandular lumen and a persistent inflammation at 12 weeks post-inoculation in the stroma. Prostatic glands showing varying degrees of atypical hyperplasia and dysplasia had stronger staining for oxidative DNA damage and increased epithelial cell proliferation than normal prostatic glands.

CONCLUSIONS

These data demonstrate that chronic inflammation induces reactive hyperplasia associated with oxidative stress injury and support the proposed linkage among inflammation, oxidative DNA damage, and prostate carcinogenesis.

A prospective study of meat and meat mutagens and prostate cancer risk

High-temperature cooked meat contains heterocyclic amines, including 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), and polycyclic aromatic hydrocarbons, such as benzo(a)pyrene (BaP). In rodents, a high intake of PhIP induces prostate tumors. We prospectively investigated the association between meat and meat mutagens, specifically PhIP, and prostate cancer risk in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Diet was assessed using a 137-item food frequency questionnaire and a detailed meat-cooking questionnaire linked to a database for BaP and the heterocyclic amines 2-amino-3,8-dimethylimidazo[4,5-b]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx), and PhIP. During follow-up, we ascertained a total of 1,338 prostate cancer cases among 29,361 men; of these, 868 were incident cases (diagnosed after the first year of follow-up) and 520 were advanced cases (stage III or IV or a Gleason score of > or =7). Total, red, or white meat intake was not associated with prostate cancer risk. More than 10 g/d of very well done meat, compared with no consumption, was associated with a 1.4-fold increased risk of prostate cancer [95% confidence interval (95% CI), 1.05-1.92] and a 1.7-fold increased risk (95% CI, 1.19-2.40) of incident disease. Although there was no association with MeIQx and DiMeIQx, the highest quintile of PhIP was associated with a 1.2-fold increased risk of prostate cancer (95% CI, 1.01-1.48) and a 1.3-fold increased risk of incident disease (95% CI, 1.01-1.61). In conclusion, very well done meat was positively associated with prostate cancer risk. In addition, this study lends epidemiologic support to the animal studies, which have implicated PhIP as a prostate carcinogen.

Polycyclic aromatic hydrocarbon-DNA adduct formation in prostate carcinogenesis

The evidence for polycyclic aromatic hydrocarbons (PAH) playing a role in prostate carcinogenesis comes mainly from associations between reported PAH exposures and prostate cancer in epidemiologic studies. Associations between prostate cancer and DNA repair genotypes and phenotypes have also been reported, lending further credence to a PAH-induced carcinogenesis pathway in prostate cancer. Recent work that demonstrates the human prostate has metabolic enzyme activity necessary for PAH activation and will form DNA adducts upon exposure to PAH further supports PAH carcinogenesis. We have demonstrated the presence of PAH-DNA adducts in prostate cancer cases, but further validation of this biomarker as a carcinogenic agent in human prostate is needed.

Cruciferous Vegetables, Genetic Polymorphisms in Glutathione S-Transferases M1 and T1, and Prostate Cancer Risk

Cruciferous vegetables contain anticarcinogenic isothiocyanates (ITCs), particularly the potent sulforaphane, which may decrease risk of prostate cancer through induction of phase II enzymes, including glutathione S-transferases (GSTs). We evaluated this hypothesis in a population-based, case-control study of prostate cancer, including 428 men with incident prostate cancer and 537 community controls. An in-person interview included an extensive food-frequency questionnaire. Genotyping for deletions in GSTM1 and GSTT1 was performed in a subset of men who provided blood. Intakes of cruciferous vegetables and of broccoli, the greatest source of sulforaphane, were associated with decreased prostate cancer risk at all levels above the lowest consumers [adjusted 4th quartile odds ratio (OR)=0.58; 95% confidence interval (CI)=0.38, 0.89, and 0.72 (95% CI=0.49, 1.06)], respectively. In relation to genotypes, there was a nonsignificant increase in risk with the GSTT1 null genotype (OR=1.51; 95% CI=0.98, 2.31) but no effects of GSTM1 genotype. However, men with GSTM1-present genotype and high broccoli intake had the greatest reduction in risk (OR=0.49; 95% CI=0.27, 0.89). Our findings provide evidence that two or more servings per month of cruciferous vegetables may reduce risk of prostate cancer, especially among men with GSTM1-present alleles, and are consistent with a role of dietary ITCs as chemopreventive agents against prostate cancer.

Primary cultures of prostate cells and their ability to activate carcinogens

Differences in the incidence of prostate cancer (CaP) amongst different migrant populations point to causative agents of dietary and/or environmental origin. Prostate tissues were obtained following transurethral resection of the prostate (TURP) or radical retropubic prostatectomy. After surgery, TURP-derived or tumour-adjacent tissue fragments were minced in warm PFMR-4A medium (37 degrees C) and suspensions pipetted into collagen-coated petri dishes. Non-adherent material was removed by washing with fresh medium after 12 h. Adhered cells subsequently reacted positively with monoclonal antibodies to prostate specific antigen (PSA). PSA was also detected in the medium. The genotoxicities of the chemical carcinogens 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (PhIP), its N-hydroxy metabolite (N-OH-PhIP) and benzo[a]pyrene (B[a]P) in adherent cell populations from different donors (n=8) were examined. Cells were treated in suspension for 30 min at 37 degrees C in the presence of the DNA repair inhibitors hydroxyurea (HU) and cytosine arabinoside (ara-C). DNA single-strand breaks were detected in cells by the alkaline single cell-gel electrophoresis ('Comet') assay and quantified by measuring comet tail length (CTL) in microm. All three carcinogens induced dose-related increases in CTLs (P<0.0001) in cells from four donors 24 h post-seeding. However, in cells from a further two donors the genotoxic effects of PhIP, N-OH-PhIP and B[a]P were much less apparent after 48 h than after 24 h in culture. After 96 h in culture, cells from these donors appeared to be resistant to the comet-forming activity of the compounds. However, B[a]P-DNA adducts were still measurable by (32)P-postlabelling for up to 14 days following a 24-h exposure to 50 microM B[a]P in adhered cells from another two donors. This study shows that primary cultures of cells derived from the prostate can activate members of two classes of chemical carcinogens. Further development may provide a robust model system in which to investigate the aetiology of CaP.