Constitutive expression of bioactivating enzymes in normal human prostate suggests a capability to activate pro-carcinogens to DNA-damaging metabolites

Metabolic Activation of the Cooked Meat Carcinogen 2-Amino-1-Methyl-6-Phenylimidazo[4,5-b]Pyridine in Human Prostate

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), an heterocyclic aromatic amine (HAA) formed in cooked meat, is a rodent and possible human prostate carcinogen. Recently, we identified DNA adducts of PhIP in the genome of prostate cancer patients, but adducts of 2-amino-3, 8-dimethylmidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-9 H-pyrido[2,3-b]indole (AαC), other prominent HAAs formed in cooked meats, were not detected. We have investigated the bioactivation of HAAs by Phase I and II enzymes in the human prostate (LNCaP) cell line using cytotoxicity and DNA adducts as endpoints. PhIP, MeIQx, and 2-amino-3-methylimidazo[4,5-f]quinoline, another HAA found in cooked meats, were poorly bioactivated and not toxic. The synthetic genotoxic N-hydroxylated-HAAs were also assayed in LNCaP cells with Phase II enzyme inhibitors. Notably, 2-hydroxy-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (HONH-PhIP), but not other HONH-HAAs, induced cytotoxicity. Moreover, PhIP-DNA adduct formation was 20-fold greater than adducts formed with other HONH-HAAs. Pretreatment of LNCaP cells with mefenamic acid, a specific inhibitor of sulfotransferase (SULT1A1), decreased PhIP-DNA adducts by 25%, whereas (Z)-5-(2'-hydroxybenzylidene)-2-thioxothiazolidin-4-one and pentachlorophenol, inhibitors of SULTs and N-acetyltransferases (NATs), decreased the PhIP-DNA adduct levels by 75%. NATs in cytosolic fractions of LNCaP cells and human prostate catalyzed DNA binding of HONH-PhIP by up to 100-fold greater levels than for SULT and kinase activities. Recombinant NAT2 is catalytically superior to recombinant NAT1 in the bioactivation of HONH-PhIP; however, the extremely low levels of NAT2 activity in prostate suggest that NAT1 may be the major isoform involved in PhIP-DNA damage. Thus, the high susceptibility of LNCaP cells recapitulates the DNA-damaging effect of HONH-PhIP in rodent and human prostate.

An analysis of benign human prostate offers insights into the mechanism of apocrine secretion and the origin of prostasomes

The structure and function of normal human prostate is still not fully understood. Herein, we concentrate on the different cell types present in normal prostate, describing some previously unreported types and provide evidence that prostasomes are primarily produced by apocrine secretion. Patients (n = 10) undergoing TURP were prospectively consented based on their having a low risk of harbouring CaP. Scanning electron microscopy and transmission electron microscopy was used to characterise cell types and modes of secretion. Zinc levels were determined using Inductively Coupled Plasma Mass Spectrometry. Although merocrine secretory cells were noted, the majority of secretory cells appear to be apocrine; for the first time, we clearly show high-resolution images of the stages of aposome secretion in human prostate. We also report a previously undescribed type of epithelial cell and the first ultrastructural image of wrapping cells in human prostate stroma. The zinc levels in the tissues examined were uniformly high and X-ray microanalysis detected zinc in merocrine cells but not in prostasomes. We conclude that a significant proportion of prostasomes, possibly the majority, are generated via apocrine secretion. This finding provides an explanation as to why so many large proteins, without a signal peptide sequence, are present in the prostatic fluid.

Carcinogens and DNA damage

Humans are variously and continuously exposed to a wide range of different DNA-damaging agents, some of which are classed as carcinogens. DNA damage can arise from exposure to exogenous agents, but damage from endogenous processes is probably far more prevalent. That said, epidemiological studies of migrant populations from regions of low cancer risk to high cancer risk countries point to a role for environmental and/or lifestyle factors playing a pivotal part in cancer aetiology. One might reasonably surmise from this that carcinogens found in our environment or diet are culpable. Exposure to carcinogens is associated with various forms of DNA damage such as single-stand breaks, double-strand breaks, covalently bound chemical DNA adducts, oxidative-induced lesions and DNA-DNA or DNA-protein cross-links. This review predominantly concentrates on DNA damage induced by the following carcinogens: polycyclic aromatic hydrocarbons, heterocyclic aromatic amines, mycotoxins, ultraviolet light, ionising radiation, aristolochic acid, nitrosamines and particulate matter. Additionally, we allude to some of the cancer types where there is molecular epidemiological evidence that these agents are aetiological risk factors. The complex role that carcinogens play in the pathophysiology of cancer development remains obscure, but DNA damage remains pivotal to this process.

The impact of p53 function on the metabolic activation of the carcinogenic air pollutant 3-nitrobenzanthrone and its metabolites 3-aminobenzanthrone and N-hydroxy-3-aminobenzanthrone in human cells

The tumour suppressor p53, encoded by TP53, is a key player in a wide network of signalling pathways. We investigated its role in the bioactivation of the environmental carcinogen 3-nitrobenzanthrone (3-NBA)found in diesel exhaust and its metabolites 3-aminobenzanthrone (3-ABA) and N-hydroxy-3-aminobenzanthrone (N-OH-3-ABA) in a panel of isogenic human colorectal HCT116 cells differing only with respect to their TP53 status [i.e. TP53(+/+), TP53(+/-), TP53(-/-), TP53(R248W/+) or TP53(R248W/-)]. As a measure of metabolic competence, DNA adduct formation was determined using 32P-postlabelling. Wild-type (WT) p53 did not affect the bioactivation of 3-NBA; no difference in DNA adduct formation was observed in TP53(+/+), TP53(+/-) and TP53(-/-) cells. Bioactivation of both metabolites 3-ABA and N-OH-3-ABA on the other hand was WT-TP53 dependent. Lower 3-ABA- and N-OH-3-ABA-DNA adduct levels were found in TP53(+/-) and TP53(-/-) cells compared to TP53(+/+) cells, and p53's impact was attributed to differences in cytochrome P450 (CYP) 1A1 expression for 3-ABA whereas for N-OH-3-ABA, an impact of this tumour suppressor on sulphotransferase (SULT) 1A1/3 expression was detected. Mutant R248W-p53 protein function was similar to or exceeded the ability of WT-p53 in activating 3-NBA and its metabolites, measured as DNA adducts. However, identification of the xenobiotic-metabolising enzyme(s) (XMEs), through which mutant-p53 regulates these responses, proved difficult to decipher. For example, although both mutant cell lines exhibited higher CYP1A1 induction after 3-NBA treatment compared to TP53(+/+) cells, 3-NBA-derived DNA adduct levels were only higher in TP53(R248W/-) cells but not in TP53(R248W/+) cells. Our results show that p53's influence on carcinogen activation depends on the agent studied and thereby on the XMEs that mediate the bioactivation of that particular compound. The phenomenon of p53 regulating CYP1A1 expression in human cells is consistent with other recent findings; however, this is the first study highlighting the impact of p53 on sulphotransferase-mediated (i.e. SULT1A1) carcinogen metabolism in human cells.

Functional role and tobacco smoking effects on methylation of CYP1A1 gene in prostate cancer

Cytochrome P450 (CYP) 1A1 is a phase I enzyme that can activate various compounds into reactive forms and thus, may contribute to carcinogenesis. In this study, we investigated the expression, methylation status, and functional role of CYP1A1 on prostate cancer cells. Increased expression of CYP1A1 was observed in all cancer lines (PC-3, LNCaP, and DU145) compared to BPH-1 (P < 0.05); and was enhanced further by 5-aza-2′-deoxycytidine treatment (P < 0.01). Methylation-specific PCR (MSP) and sequencing of bisulfite-modified DNA of the xenobiotic response element (XRE) enhancer site XRE-1383 indicated promoter methylation as a regulator of CYP1A1 expression. In tissue, microarrays showed higher immunostaining of CYP1A1 in prostate cancer than normal and benign prostatic hyperplasia (BPH; P < 0.001), and methylation analyses in clinical specimens revealed significantly lower methylation levels in cancer compared to BPH at all enhancer sites analyzed (XRE-1383, XRE-983, XRE-895; P < 0.01). Interestingly, smoking affected the XRE-1383 site where the methylation level was much lower in cancer tissues from smokers than non-smokers (P < 0.05). CYP1A1 levels are thus increased in prostate cancer and to determine the functional effect of CYP1A1 on cells, we depleted the gene in LNCaP and DU145 by siRNA. We observe that CYP1A1 knockdown decreased cell proliferation (P < 0.05) and increased apoptosis (P < 0.01) in both cell lines. We analyzed genes affected by CYP1A1 silencing and found that apoptosis-related BCL2 was significantly down-regulated. This study supports an oncogenic role for CYP1A1 in prostate cancer via promoter hypomethylation that is influenced by tobacco smoking, indicating CYP1A1 to be a promising target for prostate cancer treatment.

Altered gene expression profiles in the lungs of benzo[a]pyrene-exposed mice in the presence of lipopolysaccharide-induced pulmonary inflammation

Patients with inflammatory lung diseases are often additionally exposed to polycyclic aromatic hydrocarbons like B[a]P and B[a]P-induced alterations in gene expression in these patients may contribute to the development of lung cancer. Mice were intra-nasally treated with lipopolysaccharide (LPS, 20μg/mouse) to induce pulmonary inflammation and subsequently exposed to B[a]P (0.5mg/mouse) by intratracheal instillation. Gene expression changes were analyzed in mouse lungs by RNA microarrays. Analysis of genes that are known to be involved in the cellular response to B[a]P indicated that LPS significantly inhibited gene expression of various enzymes linked to B[a]P metabolism, which was confirmed by phenotypic analyses of enzyme activity. Ultimately, these changes resulted in higher levels of B[a]P-DNA adducts in the lungs of mice exposed to B[a]P with prior LPS treatment compared to the lungs of mice exposed to B[a]P alone. Using principle component analysis (PCA), we found that of all the genes that were significantly altered in their expression, those that were able to separate the different exposure conditions were predominantly related to immune-response. Moreover, an overall analysis of differentially expressed genes indicated that cell-cell adhesion and cell-cell communication was inhibited in lungs of mice that received both B[a]P and LPS. Our results indicate that pulmonary inflammation increased the genotoxicity of B[a]P via inhibition of both phase I and II metabolism. Therefore, inflammation could be a critical contributor to B[a]P-induced carcinogenesis in humans.

Cancer chemoprevention revisited: Cytochrome P450 family 1B1 as a target in the tumor and the microenvironment

Cancer chemoprevention is the use of synthetic, natural or biological agents to prevent or delay the development or progression of malignancies. Intriguingly, many phytochemicals with anti-inflammatory and anti-angiogenic effects, recently proposed as chemoprevention strategies, are inhibitors of Cytochrome P450 family 1B1 (CYP1B1), an enzyme overexpressed in a wide variety of tumors and associated with angiogenesis. In turn, pro-inflammatory cytokines were reported to boost CYP1B1 expression, suggesting a key role of CYP1B1 in a positive loop of inflammatory angiogenesis. Other well-known pro-tumorigenic activities of CYP1B1 rely on metabolic bioactivation of xenobiotics and steroid hormones into their carcinogenic derivatives. In contrast to initial in vitro observations, in vivo studies demonstrated a protecting role against cancer for the other CYP1 family members (CYP1A1 and CYP1A2), suggesting that the specificity of CYP1 family inhibitors should be carefully taken into account for developing potential chemoprevention strategies. Recent studies also proposed a role of CYP1B1 in multiple cell types found within the tumor microenvironment, including fibroblasts, endothelial and immune cells. Overall, our review of the current literature suggests a positive loop between inflammatory cytokines and CYP1B1, which in turn may play a key role in cancer angiogenesis, acting on both cancer cells and the tumor microenvironment. Strategies aiming at specific CYP1B1 inhibition in multiple cell types may translate into clinical chemoprevention and angioprevention approaches.

Expression of NAD(P)H quinone dehydrogenase 1 (NQO1) is increased in the endometrium of women with endometrial cancer and women with polycystic ovary syndrome

OBJECTIVE

Women with a prior history of polycystic ovary syndrome (PCOS) have an increased risk of endometrial cancer (EC).

AIM

To investigate whether the endometrium of women with PCOS possesses gene expression changes similar to those found in EC.

DESIGN AND METHODS

Patients with EC, PCOS and control women unaffected by either PCOS or EC were recruited into a cross-sectional study at the Nottingham University Hospital, UK. For RNA sequencing, representative individual endometrial biopsies were obtained from women with EC, PCOS and a woman unaffected by PCOS or EC. Expression of a subset of differentially expressed genes identified by RNA sequencing, including NAD(P)H quinone dehydrogenase 1 (NQO1), was validated by quantitative reverse transcriptase PCR validation (n = 76) and in the cancer genome atlas UCEC (uterine corpus endometrioid carcinoma) RNA sequencing data set (n = 381). The expression of NQO1 was validated by immunohistochemistry in EC samples from a separate cohort (n = 91) comprised of consecutive patients who underwent hysterectomy at St Mary's Hospital, Manchester, between 2011 and 2013. A further 6 postmenopausal women with histologically normal endometrium who underwent hysterectomy for genital prolapse were also included. Informed consent and local ethics approval were obtained for the study.

RESULTS

We show for the first that NQO1 expression is significantly increased in the endometrium of women with PCOS and EC. Immunohistochemistry confirms significantly increased NQO1 protein expression in EC relative to nonmalignant endometrial tissue (P < .0001).

CONCLUSIONS

The results obtained here support a previously unrecognized molecular link between PCOS and EC involving NQO1.

Impact of genetic modulation of SULT1A enzymes on DNA adduct formation by aristolochic acids and 3-nitrobenzanthrone

Exposure to aristolochic acid (AA) causes aristolochic acid nephropathy (AAN) and Balkan endemic nephropathy (BEN). Conflicting results have been found for the role of human sulfotransferase 1A1 (SULT1A1) contributing to the metabolic activation of aristolochic acid I (AAI) in vitro. We evaluated the role of human SULT1A1 in AA bioactivation in vivo after treatment of transgenic mice carrying a functional human SULT1A1-SULT1A2 gene cluster (i.e. hSULT1A1/2 mice) and Sult1a1(-/-) mice with AAI and aristolochic acid II (AAII). Both compounds formed characteristic DNA adducts in the intact mouse and in cytosolic incubations in vitro. However, we did not find differences in AAI-/AAII-DNA adduct levels between hSULT1A1/2 and wild-type (WT) mice in all tissues analysed including kidney and liver despite strong enhancement of sulfotransferase activity in both kidney and liver of hSULT1A1/2 mice relative to WT, kidney and liver being major organs involved in AA metabolism. In contrast, DNA adduct formation was strongly increased in hSULT1A1/2 mice compared to WT after treatment with 3-nitrobenzanthrone (3-NBA), another carcinogenic aromatic nitro compound where human SULT1A1/2 is known to contribute to genotoxicity. We found no differences in AAI-/AAII-DNA adduct formation in Sult1a1(-/-) and WT mice in vivo. Using renal and hepatic cytosolic fractions of hSULT1A1/2, Sult1a1(-/-) and WT mice, we investigated AAI-DNA adduct formation in vitro but failed to find a contribution of human SULT1A1/2 or murine Sult1a1 to AAI bioactivation. Our results indicate that sulfo-conjugation catalysed by human SULT1A1 does not play a role in the activation pathways of AAI and AAII in vivo, but is important in 3-NBA bioactivation.

Cytochrome P450 2W1 (CYP2W1) - ready for use as the biomarker and drug target for cancer?

1. This article aims to evaluate the potentials of using cytochrome P450 2W1 (CYP2W1) as a biomarker and a drug target of cancer because of its characteristic cancer-specific expression. 2. Discrepant findings comparing the expression levels of CYP2W1 in cancer and non-cancer samples were reported. In general, the expression followed a developmental pattern. The demethylation status of CpG island and the expression levels of CYP2W1 genes was positively correlated. 3. CYP2W1 was able to activate several procarcinogens, anticancer pro-drugs and to metabolise many endogenous substances including fatty acids and lysophospholipids. 4. CYP2W1 expression level was suggested to serve as an independent prognostic biomarker in colorectal cancer and hepatocellular carcinoma. The correlation of genetic polymorphisms of CYP2W1 and cancer risk was uncertain. 5. Further characterisation of CYP2W1 structure is suggested to link to its functions. More studies are warranted to reveal the true status and the regulation of CYP2W1 expression across normal and cancer tissues. Catalytic activity of CYP2W1 should be tested on a wider spectrum of endogenous and exogenous substances before its use as the drug target. Larger size of clinical samples can be included to verify the potential of CYP2W1 as the prognostic or cancer risk biomarker.

Metabolic activation of 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine and DNA adduct formation depends on p53: Studies in Trp53(+/+),Trp53(+/-) and Trp53(-/-) mice

The expression of the tumor suppressor p53 can influence the bioactivation of, and DNA damage induced by, the environmental carcinogen benzo[a]pyrene, indicating a role for p53 in its cytochrome P450 (CYP)-mediated biotransformation. The carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), which is formed during the cooking of food, is also metabolically activated by CYP enzymes, particularly CYP1A2. We investigated the potential role of p53 in PhIP metabolism in vivo by treating Trp53(+/+), Trp53(+/-) and Trp53(-/-) mice with a single oral dose of 50 mg/kg body weight PhIP. N-(Deoxyguanosin-8-yl)-2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP-C8-dG) levels in DNA, measured by liquid chromatography-tandem mass spectrometry, were significantly lower in liver, colon, forestomach and glandular stomach of Trp53(-/-) mice compared to Trp53(+/+) mice. Lower PhIP-DNA adduct levels in the livers of Trp53(-/-) mice correlated with lower Cyp1a2 enzyme activity (measured by methoxyresorufin-O-demethylase activity) in these animals. Interestingly, PhIP-DNA adduct levels were significantly higher in kidney and bladder of Trp53(-/-) mice compared to Trp53(+/+) mice, which was accompanied by higher sulfotransferase (Sult) 1a1 protein levels and increased Sult1a1 enzyme activity (measured by 2-naphthylsulfate formation from 2-naphthol) in kidneys of these animals. Our study demonstrates a role for p53 in the metabolism of PhIP in vivo, extending previous results on a novel role for p53 in xenobiotic metabolism. Our results also indicate that the impact of p53 on PhIP biotransformation is tissue-dependent and that in addition to Cyp1a enzymes, Sult1a1 can contribute to PhIP-DNA adduct formation.

Pulmonary Inflammation Impacts on CYP1A1-Mediated Respiratory Tract DNA Damage Induced by the Carcinogenic Air Pollutant Benzo[a]pyrene

Pulmonary inflammation can contribute to the development of lung cancer in humans. We investigated whether pulmonary inflammation alters the genotoxicity of polycyclic aromatic hydrocarbons (PAHs) in the lungs of mice and what mechanisms are involved. To model nonallergic acute inflammation, mice were exposed intranasally to lipopolysaccharide (LPS; 20 µg/mouse) and then instilled intratracheally with benzo[a]pyrene (BaP; 0.5 mg/mouse). BaP-DNA adduct levels, measured by (32)P-postlabeling analysis, were approximately 3-fold higher in the lungs of LPS/BaP-treated mice than in mice treated with BaP alone. Pulmonary Cyp1a1 enzyme activity was decreased in LPS/BaP-treated mice relative to BaP-treated mice suggesting that pulmonary inflammation impacted on BaP-induced Cyp1a1 activity in the lung. Our results showed that Cyp1a1 appears to be important for BaP detoxification in vivo and that the decrease of pulmonary Cyp1a1 activity in LPS/BaP-treated mice results in a decrease of pulmonary BaP detoxification, thereby enhancing BaP genotoxicity (ie, DNA adduct formation) in the lung. Because less BaP was detoxified by Cyp1a1 in the lungs of LPS/BaP-treated mice, more BaP circulated via the blood to extrapulmonary tissues relative to mice treated with BaP only. Indeed, we observed higher BaP-DNA adduct levels in livers of LPS/BaP-treated mice compared with BaP-treated mice. Our results indicate that pulmonary inflammation could be a critical determinant in the induction of genotoxicity in the lung by PAHs like BaP. Cyp1a1 appears to be involved in both BaP bioactivation and detoxification although the contribution of other enzymes to BaP-DNA adduct formation in lung and liver under inflammatory conditions remains to be explored.

CYP1B1 polymorphisms and susceptibility to prostate cancer: a meta-analysis

Background

Studies investigating the association between single-nucleotide polymorphisms (SNPs) of the cytochrome P450 1B1 (CYP1B1) and prostate cancer (PCa) risk report conflicting results. To derive a more precise estimation of the relationship between CYP1B1 polymorphisms and PCa risk, a meta-analysis was performed.

Methodology/Principal Findings

A comprehensive literature search was conducted to identify all eligible studies of CYP1B1 polymorphisms and PCa risk. A total of 14 independent studies, including 6380 cases and 5807 controls, were identified. We investigated by meta-analysis the effects of 5 polymorphisms in CYP1B1 L432V (12 studies, 5999 cases, 5438 controls), R48G (6 studies, 1647 cases, 1846 controls), N453S (4 studies, 1407 cases, 1499 controls), −13C/T (4 studies, 1116 cases, 1114 controls), and A119S (4 studies, 1057 cases, 1018 controls). There was no evidence that L432V had significant association with PCa in overall population. After subgroup analyses by ethnicity, we found that L432V was significantly associated with PCa risk in Asians (additive: OR = 2.38, 95%CI = 1.31-4.33, P = 0.004; recessive: OR = 2.11, 95%CI = 1.17–3.79, P = 0.01; dominant: OR = 1.52, 95%CI = 1.14–2.01, P = 0.004; allelic: OR = 1.52, 95%CI = 1.20–1.92, P = 0.0006). When stratified by source of controls, significantly elevated PCa risk was found in all genetic models in population based studies (additive: OR = 1.34, 95%CI = 1.14–1.57, P = 0.0003; recessive: OR = 1.25, 95%CI = 1.09–1.43, P = 0.002; dominant: OR = 1.25, 95%CI = 1.11–1.41, P = 0.0002; allelic: OR = 1.18, 95%CI = 1.09–1.28, P<0.0001). For N453S, there was a significant association between N453S polymorphism and PCa risk in both overall population (dominant: OR = 1.18, 95%CI = 1.00–1.38, P = 0.04) and mixed population (domiant: OR = 1.31, 95%CI = 1.06–1.63, P = 0.01; allelic: OR = 1.27, 95%CI = 1.05–1.54, P = 0.01). For A119S, our analysis suggested that A119S was associated with PCa risk under recessive model in overall population (OR = 1.37, 95%CI = 1.04–1.80, P = 0.03).

Conclusions

The results suggest that L432V, N453S, and A119S polymorphisms of CYP1B1 might be associated with the susceptibility of PCa. Further larger and well-designed multicenter studies are warranted to validate these findings.

Epigenetic influences in the aetiology of cancers arising from breast and prostate: a hypothesised transgenerational evolution in chromatin accessibility

Epidemiological studies have consistently supported the notion that environmental and/or dietary factors play a central role in the aetiology of cancers of the breast and prostate. However, for more than five decades investigators have failed to identify a single cause-and-effect factor, which could be implicated; identification of a causative entity would allow the implementation of an intervention strategy in at-risk populations. This suggests a more complex pathoaetiology for these cancer sites, compared to others. When one examines the increases or decreases in incidence of specific cancers amongst migrant populations, it is notable that disease arising in colon or stomach requires one or at most two generations to exhibit a change in incidence to match that of high-incidence regions, whereas for breast or prostate cancer, at least three generations are required. This generational threshold could suggest a requirement for nonmutation-driven epigenetic alterations in the F0/F1 generations (parental/offspring adopting a more westernized lifestyle), which then predisposes the inherited genome of subsequent generations to mutagenic/genotoxic alterations leading to the development of sporadic cancer in these target sites. As such, individual susceptibility to carcinogen insult would not be based per se on polymorphisms in activating/detoxifying/repair enzymes, but on elevated accessibility of crucial target genes (e.g., oncogenes, tumour suppressor genes) or hotspots therein to mutation events. This could be termed a genomic susceptibility organizational structure (SOS). Several exposures including alcohol and heavy metals are epigens (i.e., modifiers of the epigenome), whereas others are mutagenic/genotoxic, for example, heterocyclic aromatic amines; humans are continuously and variously exposed to mixtures of these agents. Within such a transgenerational multistage model of cancer development, determining the interaction between epigenetic modification to generate a genomic SOS and genotoxic insult will facilitate a new level of understanding in the aetiology of cancer.

NAD(P)H:quinone oxidoreductase 1 (NQO1) P187S polymorphism and prostate cancer risk in Caucasians

NAD(P)H:quinone oxidoreductase 1 (NQO1) catalyses the reduction of quinoid compounds to hydroquinones, preventing the generation of free radicals and reactive oxygen. A “C” to “T” transversion at position 609 of NQO1, leading to a nonsynonymous amino acid change (Pro187Ser, P187S), results in an altered enzyme activity. No NQO1 protein activity was detected in NQO1⁶⁰⁹TT genotype, and low to intermediate activity was detected in NQO1⁶⁰⁹CT genotype compared with ⁶⁰⁹CC genotype. Thus, this polymorphism may result in altered cancer predisposition. For prostate cancer, only sparse data are available. We therefore analyzed the distribution of the NQO1 P187S SNP (single nucleotide polymorphism) in prostate cancer patients and a healthy control group. Allelic variants were determined using RFLP analysis. Overall, 232 patients without any malignancy and 119 consecutive prostate cancer patients were investigated. The genotype distribution in our cohorts followed the Hardy–Weinberg equilibrium in cases and controls. The distribution of the NQO1 codon 187 SNP did not differ significantly between prostate cancer patients and the control group (p = 0.242). There was also no association between the allelic variants and stage or Gleason score of the tumors. The NQO1 P187S SNP was not significantly associated with an increased prostate cancer risk in our cohorts. The SNP has also no influence on histopathological characteristics of the tumors. A combined analysis of all available data from published European studies also showed no significant differences in the genotype distribution between controls and prostate cancer patients. Our data suggest a minor role of the NQO1 nucleotide 609 polymorphism in prostate carcinogenesis.

Polymorphisms in carcinogen metabolism enzymes, fish intake, and risk of prostate cancer

Cooking fish at high temperature can produce potent carcinogens such as heterocyclic amines and polycyclic aromatic hydrocarbons. The effects of these carcinogens may undergo modification by the enzymes responsible for their detoxification and/or activation. In this study, we investigated genetic polymorphisms in nine carcinogen metabolism enzymes and their modifying effects on the association between white or dark fish consumption and prostate cancer (PCA) risk. We genotyped 497 localized and 936 advanced PCA cases and 760 controls from the California Collaborative Case-Control Study of Prostate Cancer. Three polymorphisms, EPHX1 Tyr113His, CYP1B1 Leu432Val and GSTT1 null/present, were associated with localized PCA risk. The PTGS2 765 G/C polymorphism modified the association between white fish consumption and advanced PCA risk (interaction P 5 0.002), with high white fish consumption being positively associated with risk only among carriers of the C allele. This effect modification by PTGS2 genotype was stronger when restricted to consumption of well-done white fish (interaction P 5 0.021). These findings support the hypotheses that changes in white fish brought upon by high-temperature cooking methods, such as carcinogen accumulation and/or fatty acid composition changes, may contribute to prostate carcinogenesis. However, the gene-diet interactions should be interpreted with caution given the limited sample size. Thus, our findings require further validation with additional studies.

Neighborhood socioeconomic status modifies the association between individual smoking status and PAH-DNA adduct levels in prostate tissue

Interactions between smoking and neighborhood-level socioeconomic status (SES) as risk factors for higher polycyclic aromatic hydrocarbon (PAH) DNA adduct levels in prostate tissue were investigated. PAH-DNA adducts were measured by immunohistochemistry with staining intensity measured in optical density units by semiquantitative absorbance image analysis in tumor adjacent tissue from 400 prostatectomy specimens from the Henry Ford Health System in Detroit. For each subject, their U.S. Census tract of residence was classified as being of higher or lower SES using the median value of the distribution of the proportion of tract residents with a high-school education. Generalized estimating equation models were used to assess interactions between neighborhood-level SES and smoking status, adjusting for race, age, education level, tumor volume, primary Gleason grade and prostate specific antigen (PSA) at diagnosis. There was a statistical interaction (P = 0.004) between tract-level SES and smoking status. In lower SES tracts smoking status was not associated with adduct staining, but in higher SES tracts adduct staining intensity was 13% (P = 0.01) higher in ever-smokers as compared to never-smokers. Among never-smokers, living in a lower SES tract was associated with a 25% higher mean staining intensity (P < 0.001). Neighborhood SES modifies the association between individual smoking status and PAH-DNA adduct levels in prostate tissue.

Effect of hepatic cytochrome P450 (P450) oxidoreductase deficiency on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine-DNA adduct formation in P450 reductase conditional null mice

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), formed during the cooking of foods, induces colon cancer in rodents. PhIP is metabolically activated by cytochromes P450 (P450s). To evaluate the role of hepatic P450s in the bioactivation of PhIP, we used Reductase Conditional Null (RCN) mice, in which cytochrome P450 oxidoreductase (POR), the unique electron donor to P450s, can be specifically deleted in hepatocytes by pretreatment with 3-methylcholanthrene (3-MC), resulting in the loss of essentially all hepatic P450 function. RCN mice were treated orally with 50 mg/kg b.wt. PhIP daily for 5 days, with and without 3-MC pretreatment. PhIP-DNA adducts (i.e., N-(deoxyguanosin-8-yl)-2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine [dG-C8-PhIP]), measured by liquid chromatography-tandem mass spectrometry, were highest in colon (1362 adducts/10(8) deoxynucleosides), whereas adduct levels in liver were ∼3.5-fold lower. Whereas no differences in PhIP-DNA adduct levels were found in livers with active POR versus inactivated POR, adduct levels were on average ∼2-fold lower in extrahepatic tissues of mice lacking hepatic POR. Hepatic microsomes from RCN mice with or without 3-MC pretreatment were also incubated with PhIP and DNA in vitro. PhIP-DNA adduct formation was ∼8-fold lower with hepatic microsomes from POR-inactivated mice than with those with active POR. Most of the hepatic microsomal activation of PhIP in vitro was attributable to CYP1A. Our results show that PhIP-DNA adduct formation in colon involves hepatic N-oxidation, circulation of activated metabolites via the bloodstream to extrahepatic tissues, and further activation, resulting in the formation of dG-C8-PhIP. Besides hepatic P450s, PhIP may be metabolically activated mainly by a non-P450 pathway in liver.

Metabolism and biomarkers of heterocyclic aromatic amines in molecular epidemiology studies: lessons learned from aromatic amines

Aromatic amines and heterocyclic aromatic amines (HAAs) are structurally related classes of carcinogens that are formed during the combustion of tobacco or during the high-temperature cooking of meats. Both classes of procarcinogens undergo metabolic activation by N-hydroxylation of the exocyclic amine group to produce a common proposed intermediate, the arylnitrenium ion, which is the critical metabolite implicated in toxicity and DNA damage. However, the biochemistry and chemical properties of these compounds are distinct, and different biomarkers of aromatic amines and HAAs have been developed for human biomonitoring studies. Hemoglobin adducts have been extensively used as biomarkers to monitor occupational and environmental exposures to a number of aromatic amines; however, HAAs do not form hemoglobin adducts at appreciable levels, and other biomarkers have been sought. A number of epidemiologic studies that have investigated dietary consumption of well-done meat in relation to various tumor sites reported a positive association between cancer risk and well-done meat consumption, although some studies have shown no associations between well-done meat and cancer risk. A major limiting factor in most epidemiological studies is the uncertainty in quantitative estimates of chronic exposure to HAAs, and thus, the association of HAAs formed in cooked meat and cancer risk has been difficult to establish. There is a critical need to establish long-term biomarkers of HAAs that can be implemented in molecular epidemioIogy studies. In this review, we highlight and contrast the biochemistry of several prototypical carcinogenic aromatic amines and HAAs to which humans are chronically exposed. The biochemical properties and the impact of polymorphisms of the major xenobiotic-metabolizing enzymes on the biological effects of these chemicals are examined. Lastly, the analytical approaches that have been successfully employed to biomonitor aromatic amines and HAAs, and emerging biomarkers of HAAs that may be implemented in molecular epidemiology studies are discussed.

Estrogen action and prostate cancer

Early work on the hormonal basis of prostate cancer focused on the role of androgens, but more recently estrogens have been implicated as potential agents in the development and progression of prostate cancer. In this article, we review the epidemiological, laboratory and clinical evidence that estrogen may play a causative role in human prostate cancer, as well as rodent and grafted in vivo models. We then review recent literature highlighting potential mechanisms by which estrogen may contribute to prostate cancer, including estrogenic imprinting and epigenetic modifications, direct genotoxicity, hyperprolactinemia, inflammation and immunologic changes, and receptor-mediated actions. We discuss the work performed so far separating the actions of the different known estrogen receptors (ERs), ERα and ERβ, as well as G-protein-coupled receptor 30 and their specific roles in prostate disease. Finally, we predict that future work in this field will involve more investigations into epigenetic changes, experiments using new models of hormonal dysregulation in developing human prostate tissue, and continued delineation of the roles of the different ER subtypes, as well as their downstream signaling pathways that may serve as therapeutic targets.

Elevated oestrogen receptor splice variant ERαΔ5 expression in tumour-adjacent hormone-responsive tissue

Susceptibility to prostate or endometrial cancer is linked with obesity, a state of oestrogen excess. Oestrogen receptor (ER) splice variants may be responsible for the tissue-level of ER activity. Such micro-environmental regulation may modulate cancer initiation and/or progression mechanisms. Real-time reverse transcriptase (RT) polymerase chain reaction (PCR) was used to quantitatively assess the levels of four ER splice variants (ERαΔ3, ERαΔ5, ERβ2 and ERβ5), plus the full-length parent isoforms ERα and ERβ1, in high-risk [tumour-adjacent prostate (n = 10) or endometrial cancer (n = 9)] vs. low-risk [benign prostate (n = 12) or endometrium (n = 9)], as well as a comparison of UK (n = 12) vs. Indian (n = 15) benign prostate. All three tissue groups expressed the ER splice variants at similar levels, apart from ERαΔ5. This splice variant was markedly raised in all of the tumour-adjacent prostate samples compared to benign tissues. Immunofluorescence analysis for ERβ2 in prostate tissue demonstrated that such splice variants are present in comparable, if not greater, amounts as the parent full-length isoform. This small pilot study demonstrates the ubiquitous nature of ER splice variants in these tissue sites and suggests that ERαΔ5 may be involved in progression of prostate adenocarcinoma.

Discrimination of zone-specific spectral signatures in normal human prostate using Raman spectroscopy

The prostate gland is the most common site of pathology in human males. Using the urethra as an anatomical reference point, it can be divided into three distinct zones known as the transition zone (TZ), peripheral zone (PZ) and central zone (CZ). The pathological conditions of benign prostatic hypertrophy and/or prostate adenocarcinoma are highly prevalent in this gland. This preliminary study set out to determine whether biochemical intra-individual differences between normal prostate zones could be identified using Raman spectroscopy with subsequent exploratory analyses. A normal (benign) prostate transverse tissue section perpendicular to the rectal surface and above the verumontanum was obtained in a paraffin-embedded block. A 10-µm-thick slice was floated onto a gold substrate, de-waxed and analysed using Raman spectroscopy (200 epithelial-cell and 140 stromal spectra/zone). Raman spectra were subsequently processed in the 1800-367 cm(-1) spectral region employing principal component analysis (PCA) to determine whether wavenumber-intensity relationships expressed as single points in hyperspace might reveal biochemical differences associated with inter-zone pathological susceptibility. Visualisation of PCA scores plots and their corresponding loadings plots highlighted 781 cm(-1) (cytosine/uracil) and 787 cm(-1) (DNA) as the key discriminating factors segregating PZ from less susceptible TZ and CZ epithelia (P < 0.001). Conversely, 1459 cm(-1) (lipids and proteins) and 1003 cm(-1) (phenylalanine) were identified as the key biochemical factor distinguishing TZ from CZ epithelia (P < 0.05). All stromal zones were discriminated by the protein/lipid region (1459 cm(-1) and 1100 cm(-1)) with DNA/RNA region (781 cm(-1) and 787 cm(-1)) only highlighted between PZ and CZ (P < 0.05). This novel approach identifies biochemical markers that may have aetiological functional roles towards susceptibility of human prostate zones to specific pathological conditions.