Polymorphisms of the CYP1B1 gene have higher risk for prostate cancer

Multigene Panel Sequencing Identifies a Novel Germline Mutation Profile in Male Breast Cancer Patients

Even though male breast cancer (MBC) risk encompasses both genetic and environmental aetiologies, the primary risk factor is a germline pathogenic variant (PV) or likely pathogenic variant (LPV) in BRCA2, BRCA1 and/or PALB2 genes. To identify new potential MBC-specific predisposition genes, we sequenced a panel of 585 carcinogenesis genes in an MBC cohort without BRCA1/BRCA2/PALB2 PV/LPV. We identified 14 genes carrying rare PVs/LPVs in the MBC population versus noncancer non-Finnish European men, predominantly coding for DNA repair and maintenance of genomic stability proteins. We identified for the first time PVs/LPVs in PRCC (pre-mRNA processing), HOXA9 (transcription regulation), RECQL4 and WRN (maintenance of genomic stability) as well as in genes involved in other cellular processes. To study the specificity of this MBC PV/LPV profile, we examined whether variants in the same genes could be detected in a female breast cancer (FBC) cohort without BRCA1/BRCA2/PALB2 PV/LPV. Only 5/109 women (4.6%) carried a PV/LPV versus 18/85 men (21.2%) on these genes. FBC did not carry any PV/LPV on 11 of these genes. Although 5.9% of the MBC cohort carried PVs/LPVs in PALLD and ERCC2, neither of these genes were altered in our FBC cohort. Our data suggest that in addition to BRCA1/BRCA2/PALB2, other genes involved in DNA repair/maintenance or genomic stability as well as cell adhesion may form a specific MBC PV/LPV signature.

CYP1B1: A Novel Molecular Biomarker Predicts Molecular Subtype, Tumor Microenvironment, and Immune Response in 33 Cancers

BACKGROUND

Cytochrome P450 Family 1 Subfamily B Member 1 (CYP1B1) is a critical metabolic enzyme of melatonin. Although melatonin has been identified to exhibit tumor suppressing activity, the role and mechanism of the clinical and immunological characteristics of CYP1B1 in cancer remain unclear.

METHODS

In this study, RNA expression and clinical data were obtained from The Cancer Genome Atlas (TCGA) across 33 solid tumors. The expression, survival, immune subtype, molecular subtype, tumor mutation burden (TMB), microsatellite instability (MSI), biological pathways, and function in vitro and vivo were evaluated. The predictive value of CYP1B1 in immune cohorts was further explored.

RESULTS

We found the dysregulated expression of CYP1B1 was associated with the clinical stage and tumor grade. Immunological correlation analysis showed CYP1B1 was positively correlated with the infiltration of lymphocyte, immunomodulator, chemokine, receptor, and cancer-associated fibroblasts (CAFs) in most cancer. Meanwhile, CYP1B1 was involved in immune subtype and molecular subtype, and was connected with TMB, MSI, neoantigen, the activation of multiple melatonergic and immune-related pathways, and therapeutic resistance.

CONCLUSIONS

Together, this study comprehensively revealed the role and mechanism of CYP1B1 and explored the significant association between CYP1B1 expression and immune activity. These findings provide a promising predictor and molecular target for clinical immune treatment.

Biological roles of cytochrome P450 1A1, 1A2, and 1B1 enzymes

Human cytochrome P450 enzymes (CYPs) play a critical role in various biological processes and human diseases. CYP1 family members, including CYP1A1, CYP1A2, and CYP1B1, are induced by aryl hydrocarbon receptors (AhRs). The binding of ligands such as polycyclic aromatic hydrocarbons activates the AhRs, which are involved in the metabolism (including oxidation) of various endogenous or exogenous substrates. The ligands that induce CYP1 expression are reported to be carcinogenic xenobiotics. Hence, CYP1 enzymes are correlated with the pathogenesis of cancers. Various endogenous substrates are involved in the metabolism of steroid hormones, eicosanoids, and other biological molecules that mediate the pathogenesis of several human diseases. Additionally, CYP1s metabolize and activate/inactivate therapeutic drugs, especially, anti-cancer agents. As the metabolism of drugs determines their therapeutic efficacy, CYP1s can determine the susceptibility of patients to some drugs. Thus, understanding the role of CYP1s in diseases and establishing novel and efficient therapeutic strategies based on CYP1s have piqued the interest of the scientific community.

Associations of CYP1 polymorphisms with risk of prostate cancer: an updated meta-analysis

Background. The results of previous studies on the association between polymorphisms of CYP1A1 and CYP1B1 and prostate cancer (PCa) susceptibility are inconsistent. The aim of the present study was to conduct a meta-analysis in order to better estimate this association. Methods. A systematic search was carried out on PubMed, Embase, Cochrane Library, and China National Knowledge Infrastructure (CNKI) databases for relevant articles published up to 15 August 2018. Pooled odds ratios (ORs) and 95% confidence intervals were obtained using fixed-effect or random-effect models. Results. A significant association was found between the CYP1A1 rs1048943 polymorphism and PCa in the overall population (B [the minor allele] vs. A [the major allele]: OR = 1.20, 95% confidence interval (CI) = 1.04–1.39, P=0.014; AB vs. AA: OR = 1.24, 95% CI = 1.02–1.51, P=0.029; BB + AB vs. AA: OR = 1.25, 95% CI = 1.04–1.50, P=0.018) and Asian population (B vs. A: OR = 1.32, 95% CI = 1.11–1.56, P=0.001; BB vs. AA: OR = 1.81, 95% CI = 1.20–2.72, P=0.005; AB vs. AA: OR = 1.30, 95% CI = 1.03–1.64, P=0.029; BB + AB vs. AA: OR = 1.38, 95% CI = 1.11–1.73, P=0.004; BB vs. AA + AB: OR = 1.58, 95% CI = 1.08–2.01, P=0.019), but not in the Caucasian population. Moreover, we found that the rs4646903 polymorphism was associated with a significant increase in the risk of PCa in the Asian population (AB vs. AA: OR = 1.43, 95% CI = 1.13–1.80, P=0.003) and Caucasian population (BB vs. AA: OR = 2.12, 95% CI = 1.29–3.49, P=0.003). Conclusion. This meta-analysis revealed a clear association between rs1048943 and rs4646903 polymorphisms of the CYP1A1 gene but not between CYP1B1 rs10012, rs162549, rs1800440, and rs2551188 polymorphisms and the risk of PCa.

Influence of lifestyle choices on risks of CYP1B1 polymorphisms for prostate cancer

Cytochrome P450 1B1 (CYP1B1) converts xenobiotics to carcinogens and how lifestyle choices may interact with CYP1B1 polymorphisms and affect prostate cancer risk was assessed. Blood genomic DNA from a Caucasian population was analysed at polymorphic sites of the 5' untranslated region of CYP1B1 using TaqMan genotyping assays. Overall, drinker status and minor alleles at rs2551188, rs2567206 and rs10175368 were associated with prostate cancer. Linkage was observed between rs2551188, rs2567206, rs2567207 and rs10175368, and the G-C-T-G haplotype (major allele at respective sites) was decreased in cancer. Interestingly when classified by lifestyle factors, no associations of genotypes were found for non-smokers and non-drinkers, whereas on the contrary, minor type at rs2567206 and rs10175368 increased and major G-C-T-G decreased risk for cancer among smokers and drinkers. Interestingly, rs2551188, rs2567206 and rs10175368 minor genotypes correlated with increased tissue CYP1B1 as determined by immunohistochemistry. Further, rs10175368 enhanced luciferase activity and mobility shift show stronger binding of nuclear factor for the minor allele. These results demonstrate smoking and alcohol consumption to modify the risks of CYP1B1 polymorphisms for prostate cancer which may be through rs10175368, and this is of importance in understanding their role in the pathogenesis and as a biomarker for this disease.

A single nucleotide polymorphism in CYP1B1 leads to differential prostate cancer risk and telomere length

BACKGROUND: Cytochrome P450 1B1 (CYP1B1) is a key enzyme in its oestrogen metabolism pathway, giving rise to hydroxylation and conjugation. Functionally relevant genetic variants within CYP1B1 may affect the telomere length and subsequently lead to prostate carcinogenesis.

METHODS: We evaluated 8 CYP1B1 tag single nucleotide polymorphisms (SNPs) in 1015 men with prostate cancer (PCa) and 1052 cancer-free controls, and calculated odds ratios (ORs) and 95% confidence intervals (CIs) to estimate their association with risk of PCa. The influence of CYP1B1 SNPs on the relative telomere lengths was then appraised in peripheral blood leukocytes using real-time PCR.

RESULTS:CYP1B1 rs1056836 variant was associated with decreased risk of PCa [odds ratio (OR): 0.80; 95% confidence interval (CI): 0.68-0.99, P = 0.041]. Longer telomere length showed a significantly higher proportion of the CYP1B1 rs1056836 CG/GG genotypes, compared with that of the CC genotype (OR: 1.60, 95% CI: 1.04-2.45).

CONCLUSION: Our findings suggest that genetic variants within CYP1B1 may confer genetic susceptibility to PCa by altering telomere length.

Genetic variants of the CYP1B1 gene as predictors of biochemical recurrence after radical prostatectomy in localized prostate cancer patients

Clinically localized prostate cancer is curative. Nevertheless many patients suffered from biochemical recurrence (BCR) after radical prostatectomy (RP). Mounting evidence suggest that estrogen and xenobiotic carcinogens play an essential role in progression of prostate cancervia oxidative estrogen metabolism. CYP1B1 is an enzyme involved in the hydroxylation of estrogens, a reaction of key relevance in estrogen metabolism. Given the role of CYP1B1 in the oxidative metabolism of endogenous/exogenous estrogen and compounds, CYP1B1 polymorphisms have the potential to modify its expression and subsequently lead to progression. We hypothesize that genetic variants of the CYP1B1 gene may influence clinical outcome in clinically localized prostate cancer patients. In this cohort study, we genotyped 9 tagging single nucleotide polymorphisms (SNPs) from the CYP1B1 gene in 312 patients treated with RP. For replication, these SNPs were genotyped in an independent cohort of 426 patients. The expression level of CYP1B1 in the adjacent normal prostate tissues was quantified by reverse transcription and real-time polymerase chain reaction. Kaplan-Meier analysis and Cox proportional hazard models were utilized to identify SNPs that correlated with BCR. CYP1B1 rs1056836 was significantly associated with BCR (hazard ratio [HR]: 0.69; 95% confidence interval [CI]: 0.40-0.89, P = 0.002) and relative CYP1B1 mRNA expression. Our findings suggest inherited genetic variation in the CYP1B1 gene may contribute to variable clinical outcomes for patients with clinically localized prostate cancer.

Pharmacogenetics of the Cytochrome P450 Enzyme System: Review of Current Knowledge and Clinical Significance

Genetic variation in drug metabolizing enzymes is an important contributor to interindividual variation in drug disposition and response and is associated with significant clinical consequences. Many commonly used drugs are dependent on the cytochrome P450 monooxygenase enzymes (CYP450) for their metabolism and elimination. At present, more than 57 active human CYP450 genes are known, and the majority of these genes are polymorphic. Despite the large number of CYP450 genes, only the CYP1, CYP2, and CYP3 families of enzymes have a major role in drug metabolism. Approximately 10 CYP450s are responsible for the metabolism of a large number of pharmacologic agents in human beings. The polymorphic forms of the CYP450s are responsible for the development of a significant number of adverse drug reactions and may also contribute to drug response. Genetic polymorphisms have now been identified in the genes encoding all the main CYP450s that contribute to drug and other xenobiotic metabolism, and there are marked interethnic differences in the distribution and frequency of variant alleles. A review of the progress in the pharmacogenetics of P450s that are important for drug metabolism is presented with particular emphasis on the clinical relevance of this research.

Polymorphisms in androgen metabolism genes AR, CYP1B1, CYP19, and SRD5A2and prostate cancer risk and aggressiveness in Bulgarian patients

BACKGROUND/AIM

The aim of our study was to elucidate the role of polymorphisms in AR, CYP1B1, CYP19, and SRD5A2 genes for prostate cancer (PC) development in Bulgarian patients.

MATERIALS AND METHODS

We genotyped 246 PC patients and 261 controls (155 with benign prostate hyperplasia and 107 healthy population controls) using direct sequencing, PCR-RFLP, SSCP, and fragment analysis.

RESULTS

The allele and genotype frequencies of most of the studied variants did not differ significantly between cases and controls. Increased frequencies of the C/C genotype and C allele of rs1056837 in CYP1B1, and genotype 7/8 of the (TTTA)n repeat polymorphism in CYP19, were observed in patients in comparison with controls.The 8/9 and the 7/12 genotypes of (TTTA)n in CYP19 showed suggestive evidence for association with decreased prostate cancer risk and the risk for aggressive disease, respectively. The haplotype analysis revealed 2 CYP1B1 haplotypes associated with PC risk reduction.

CONCLUSION

Some CYP1B1 haplotypes and genotypes of the CYP19 (TTTA)n repeat appeared to be associated with disease risk or aggressiveness in Bulgarian PC patients. In contrast, the SRD5A2 polymorphisms (V89L and (TA)n repeat), the CAG repeat in AR, and the Arg264Cys variant in CYP19A1 are most likely not implicated in prostate carcinogenesis.

Cytochrome P450 in Cancer Susceptibility and Treatment

Cytochrome 450 (CYP450) designates a group of enzymes abundant in smooth endoplasmic reticulum of hepatocytes and epithelial cells of small intestines. The main function of CYP450 is oxidative catalysis of various endogenous and exogenous substances. CYP450 are implicated in phase I metabolism of 80% of drugs currently in use, including anticancer drugs. They are also involved in synthesis of various hormones and influence hormone-related cancers. CYP450 genes are highly polymorphic and their variants play an important role in cancer risk and treatment. Association studies and meta-analyses have been performed to decipher the role of CYP450 polymorphisms in cancer susceptibility. Cancer treatment involves multimodal therapies and evaluation of CYP450 polymorphisms is necessary for pharmacogenetic assessment of anticancer therapy outcomes. In addition, CYP450 inhibitors are being evaluated for improved pharmacokinetics and oral formulation of several anticancer drugs.

Association of CYP1B1 L432V polymorphism with urinary cancer susceptibility: a meta-analysis

BACKGROUND

The Cytochrome P450 1B1 (CYP1B1) is a key P450 enzyme involved in the metabolism of exogenous and endogenous substrates. Previous studies have reported the existence of CYP1B1 L432V missense polymorphism in prostate, bladder and renal cancers. However, the effects of this polymorphism on the risk of these cancers remain conflicting. Therefore, we performed a meta-analysis to assess the association between L432V polymorphism and the susceptibility of urinary cancers.

METHODS

We searched the PubMed database without limits on language for studies exploring the relationship of CYP1B1 L432V polymorphism and urinary cancers. Article search was supplemented by screening the references of retrieved studies manually. Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated to evaluate the strength of these associations. Simultaneously, publication bias was estimated by funnel plot and Begg's test with Stata 11 software.

RESULTS

We observed a significant association between CYP1B1 L432V polymorphism and urinary cancers. The overall OR (95% CI) of CC versus CG was 0.937 (0.881-0.996), the overall OR (95% CI) of CC versus CG+GG was 0.942 (0.890-0.997). Furthermore, we identified reduced risk for CC versus other phenotypes in both prostate and overall urinary cancers, when studies were limited to Caucasian or Asian patients.

CONCLUSIONS

This meta-analysis suggests that the CYP1B1 L432V polymorphism is associated with urinary cancer risk.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/3108829721231527.

The CYP1B1 Leu432Val polymorphism and risk of urinary system cancers

The cytochrome P450 1B1 (CYP1B1) gene plays a key role in the metabolism of various carcinogens. The CYP1B1 Leu432Val polymorphism leads to leucine to valine substitution at codon 432. A lot of studies have shown that the CYP1B1 Leu432Val polymorphism was associated with urinary system cancers, especially prostate cancer. However, the results were still inconclusive. In this meta-analysis, by searching online databases and references of related reviews, we identified 17 eligible studies to assess the relationship between CYP1B1 Leu432Val polymorphism and urinary system cancers, including 7,783 cancer cases and 7,238 controls. By pooling all eligible studies, we found that the CYP1B1 Leu432Val polymorphism was not associated with overall urinary system cancers. However, in subgroup analyses, we found that the variant 432Val allele significantly increased the risk of prostate cancer (Val vs. Leu, odds ratio (OR) = 1.064, 95% confidence interval (CI) 0.981-1.154; Pheterogeneity = 0.002), while no association was found for bladder cancer (Val vs. Leu, OR = 0.942, 95% CI 0.853-1.041; Pheterogeneity = 0.504). No evidence of publication bias was found (Begg's test, P = 0.053; Egger's test, P = 0.073). In conclusion, based on 17 eligible studies, we found that the CYP1B1 Leu432Val polymorphism was associated with an increased risk of prostate cancer, while no association of bladder cancer was observed.

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.

Expression of the aryl hydrocarbon receptor pathway and cyclooxygenase-2 in dog tumors

In humans, the aryl hydrocarbon receptor (AHR) gene battery constitutes a set of contaminant-responsive genes, which have been recently shown to be involved in the regulation of several patho-physiological conditions, including tumorigenesis. As the domestic dog represents a valuable animal model in comparative oncology, mRNA levels of cytochromes P450 1A1, 1A2 and 1B1 (CYP1A1, 1A2 and 1B1), AHR, AHR nuclear translocator (ARNT), AHR repressor (AHRR, whose partial sequence was here obtained) and cyclooxygenase-2 (COX2) were measured in dog control tissues (liver, skin, mammary gland and bone), in 47 mast cell tumors (MCTs), 32 mammary tumors (MTs), 5 osteosarcoma (OSA) and related surgical margins. Target genes were constitutively expressed in the dog, confirming the available human data. Furthermore, their pattern of expression in tumor biopsies was comparable to that already described in a variety of human cancers; in particular, both AHR and COX2 genes were up-regulated and positively correlated, while CYP1A1 and CYP1A2 mRNAs were generally poorly expressed. This work demonstrated for the first time that target mRNAs are expressed in neoplastic tissues of dogs, thereby increasing the knowledge about dog cancer biology and confirming this species as an useful animal model for comparative studies on human oncology.

Prostate cancer risk and aggressiveness associated with the CYP1B1 4326C/G (Leu432Val) polymorphism: a meta-analysis of 2788 cases and 2968 controls

To derive a precise estimation of the associations between the cytochrome P450 1B1 (CYP1B1) 4326C/G variants and prostate cancer (PCa) risk or aggressiveness, a meta-analysis was performed using all eligible published studies. Odds ratios (ORs) with 95% confidence intervals (CIs) were estimated to assess the association in seven literature studies with 2788 cases and 2968 controls. In the overall analysis, no significant association was found between the CYP1B1 4326C/G polymorphism and PCa risk, but ethnicity subgroup analyses and a case-source analysis revealed significant associations. The 4326G allele showed a significant association with increased PCa risk in Asians (OR=1.52, 95% CI: 1.20-1.92), and significant associations were also observed in a heterozygote comparison (OR=1.40, 95% CI: 1.03-1.89), a homozygote comparison (OR=2.38, 95% CI: 1.31-4.33) and in a dominant genetic model (OR=1.52, 95% CI: 1.14-2.01). Moreover, the 4326G allele was also significantly correlated with an increased risk of sporadic PCa (OR=1.13, 95% CI: 1.04-1.24), and significant associations were observed in a heterozygote comparison (OR=1.16, 95% CI: 1.02-1.33), a homozygote comparison (OR=1.24, 95% CI: 1.03-1.49) and a dominant genetic model (OR=1.19, 95% CI: 1.05-1.34). The overall analyses and all subgroup analyses showed no significant association between the 4326C/G polymorphism and PCa aggressiveness. Our meta-analysis showed that CYP1B1 4326G allele is significantly associated with an increased PCa risk in Asians and in sporadic PCa cases.

Primary Congenital Glaucoma and the Involvement of CYP1B1

Primary congenital glaucoma (PCG) is an autosomal recessive disorder in children due to the abnormal development of the trabecular meshwork and the anterior chamber angle. With an onset at birth to early infancy, PCG is highly prevalent in inbred populations and consanguinity is strongly associated with the disease. Gene mapping of PCG-affected families has identified three chromosomal loci, GLC3A, GLC3B and GLC3C, of which, the CYP1B1 gene on GLC3A harbors mutations in PCG. The mutation spectra of CYP1B1 vary widely across different populations but are well structured based on geographic and haplotype backgrounds. Structural and functional studies on CYP1B1 have suggested its potential role in the development and onset of glaucomatous symptoms. A new locus (GLC3D) harboring the LTBP2 gene has been characterized in developmental glaucoma but its role in classical cases of PCG is yet to be understood. In this review, we provide insight into PCG pathogenesis and the potential role of CYP1B1 in the disease phenotype.

Circulating steroid hormones in prostate carcinogenesis. Part 2: Estrogens

The aim of this review is to describe the associations between circulating plasma estrogens and prostate cancer (PCa). We recall the origins of estrogens, which derive from the aromatization of androgens, but also by sulfatase hydrolysis of estrone sulfate (E1-S), the main circulating plasma estrogen. We evoke that the carcinogenic effects of estrogens were demonstrated in the rat and murine prostate when estrogens and androgens were simultaneously administered to them. We also describe estrogen proliferative activity and the genotoxicity of estrogen-hydroxylated metabolites with the formation of DNA adducts. We report published aromatase and CYP1B1 polymorphisms found in men with PCa. We published a bibliography on the relation between PCa and prostate inflammation, as well as the possible role of obesity in the aggressiveness of PCa. In this review, we provide an exhaustive list of assays carried out in subjects at high risk for PCa compared with Caucasians, showing that higher estrogen levels were found in the plasma of these subjects at high risk for PCa. Plasma estrone was the estrogen for which plasma concentration was highest in subjects of African descent. We recall the links observed between plasma estrogens, particularly E1-S, and PCa aggressiveness. Finally, we describe assays for determining hydroxylated estrogens and DNA adducts in the urine of men with PCa. We insist on the importance of the technology employed in estrogen measurement and propose the use of mass spectrometry methods to carry out estrogen assays, in order to decrease variability in the results of plasma estrogen assays.

Toward an automatic method for extracting cancer- and other disease-related point mutations from the biomedical literature

MOTIVATION

A major goal of biomedical research in personalized medicine is to find relationships between mutations and their corresponding disease phenotypes. However, most of the disease-related mutational data are currently buried in the biomedical literature in textual form and lack the necessary structure to allow easy retrieval and visualization. We introduce a high-throughput computational method for the identification of relevant disease mutations in PubMed abstracts applied to prostate (PCa) and breast cancer (BCa) mutations.

RESULTS

We developed the extractor of mutations (EMU) tool to identify mutations and their associated genes. We benchmarked EMU against MutationFinder--a tool to extract point mutations from text. Our results show that both methods achieve comparable performance on two manually curated datasets. We also benchmarked EMU's performance for extracting the complete mutational information and phenotype. Remarkably, we show that one of the steps in our approach, a filter based on sequence analysis, increases the precision for that task from 0.34 to 0.59 (PCa) and from 0.39 to 0.61 (BCa). We also show that this high-throughput approach can be extended to other diseases.

DISCUSSION

Our method improves the current status of disease-mutation databases by significantly increasing the number of annotated mutations. We found 51 and 128 mutations manually verified to be related to PCa and Bca, respectively, that are not currently annotated for these cancer types in the OMIM or Swiss-Prot databases. EMU's retrieval performance represents a 2-fold improvement in the number of annotated mutations for PCa and BCa. We further show that our method can benefit from full-text analysis once there is an increase in Open Access availability of full-text articles.

AVAILABILITY

Freely available at: http://bioinf.umbc.edu/EMU/ftp.

Evaluation of the influence of polymorphic variants CYP1A1 2B, CYP1B1 2, CYP3A4 1B, GSTM1 0, and GSTT1 0 in prostate cancer

BACKGROUND/OBJECTIVE

Genetic polymorphisms in cytochrome P-450 (CYPs) and glutathione S-transferase (GSTs) genes can influence the appearance of tumors by the formation of new enzymes with altered activities. In the present study, 5 polymorphic variants were examined in 154 patients with prostate carcinoma and in 154 controls.

MATERIALS AND METHODS

DNA analysis was carried out through PCR-based methods. The statistical methods used were odds ratio and confidence interval (95% CI), χ(2), Fisher, and Mann-Whitney.

RESULTS

The study showed absence of association for CYP1A1 2B, CYP1B1 2, GSTM1 0, and GSTT1 0. The statistical analysis implied a positive association of variant CYP3A4 1B for prostate cancer. The combined analysis of CYP1A1 2B, CYP1B1 2, and CYP3A4 1B genotypes showed positive association. The analysis of histopathologic parameters detected statistically significant differences for Gleason score and biochemistry recurrence risk. The presence of the GSTT1 0 genotype in red meat consumers increased the risk for this disease.

CONCLUSION

Some polymorphic variants analyzed can influence the development and the progression of prostate cancer.

Frequency of CYP1B1 homozygous genotype 355T/T in prostate cancer families from Poland

A group of 98 families were analyzed for CYP1B1 gene 355T/T homozygous genotype frequency because of prostate cancer history. Molecular investigations were performed using the restriction fragment length polymorphism-PCR method. 355T/T genotype was detected in 14 of the 98 prostate cancer patients (14.3%). Among them, it was found in one man (7.1%) from a family suspected of hereditary prostate cancer (his age at prostate cancer diagnosis was 57 years) and in 13 men (92.9%) originating from families that did not strictly fulfill hereditary prostate cancer criteria (the median age at prostate cancer diagnosis was 60.1 years). Among 14 355T/T genotype-positive families, in 10 (71.4%) other types of cancers, for example, breast, uterus, stomach, colon, ovary, lung, larynx, bladder, pancreas and melanoma other than prostate cancer, were present, and in four (28.6%) only one cancer type, that is, prostate cancer, occurred. In the Polish population, the CYP1B1 355T/T genotype seems to be associated with prostate cancer; the frequency of this genotype was 5.9% higher in prostate cancer patients than in the general population (8.4%). However, it is not associated with prostate cancer family history.

Cytochrome P450 1B1 mRNA untranslated regions interact to inhibit protein translation

CYP1B1 mRNA is expressed constitutively in all normal extrahepatic human tissues, though the protein is usually undetectable. In contrast, CYP1B1 protein is expressed at high levels in tumors. In this study CYP1B1 mRNA and protein expression was measured in a panel of cell lines indicating that CYP1B1 regulation is altered in tumor cell lines in vitro. Interrogation of ONCOMINE revealed that CYP1B1 mRNA is not significantly overexpressed in tumors compared to normal tissues, suggesting CYP1B1 is subject to posttranscriptional control. Analysis of the CYP1B1 mRNA revealed a complex 5' untranslated region (UTR) containing a small upstream open-reading frame (uORF). These features are present in mRNAs subject to translational control so the effect of the 5'UTR was tested using in vitro translation in CHO-K1 cells. The 5'UTR significantly inhibited luciferase reporter gene translation, and mutation of the uORF start codon abolished the inhibitory effect. The 5'UTR also interacted with the microRNA-27b recognition element in the CYP1B1 mRNA 3'UTR to almost completely inhibit translation. CYP1B1 is subject to a high degree of translational control, which may explain the absence of protein expression in normal cells. Alterations in translational control during malignant transformation may help to explain the tumor-specific expression of CYP1B1 protein.

Frequency of common CYP1B1 polymorphic variations in Delhi population of Northern India

Cytochrome P4501B1 (CYP1B1) is an extrahepatic enzyme, important in the activation of procarcinogens. It is expressed in steroidegenic tissues and is active in the metabolism of estradiol. CYP1B1 polymorphisms have been shown to be associated with cancer susceptibility related to environmental toxins and hormone exposure. CYP1B1 is also involved in the metabolism of some clinically relevant anticancer drugs. Polymorphisms in the gene have also been associated in primary open-angle glaucoma (POAG). Their genotypes may also display ethnicity dependent population frequencies. Present study was aimed to determine the frequency of five known CYP1B1 polymorphisms in Delhi population. Frequency of CYP1B1 polymorphisms, CYP1B1*2, CYP1B1*3, CYP1B1*4 and CYP1B1*7 were found to be 39, 48.8, 47.3 and 17.07% respectively in normal, healthy individuals. Arg48Gly and Ala119Ser were found to be completely linked with each other. Analysis of CYP1B1 polymorphisms might help in predicting the risk of cancer as well as susceptibility to POAG. Our results emphasize the need for more such studies in "high risk populations".

CYP1B1 variants are associated with prostate cancer in non-Hispanic and Hispanic Caucasians

Cytochrome P450 1B1 (CYP1B1) is involved in the activation of many carcinogens and in the metabolism of steroid hormones. We compared allele, genotype and haplotype frequencies of six single-nucleotide polymorphisms (SNPs) within CYP1B1 among non-Hispanic Caucasians (496 cases and 498 controls) and Hispanic Caucasians (153 cases and 240 controls). In the Hispanic Caucasians, the GG genotype for rs1056836 decreased the risk for prostate cancer (PCa) when compared with the CC genotype [odds ratio (OR) = 0.31, P = 0.04, 95% confidence interval (CI) = 0.10–0.96]. Among non-Hispanic Caucasian men with more aggressive PCa, the prevalence of several SNPs (rs2567206, rs2551188, rs2617266, rs10012 and rs1056836) was significantly associated with the disease status. A common C-G-C-C-G-A haplotype for rs2567206-rs2551188-rs2617266-rs10012-rs1056836-rs1800440 showed an inverse association with PCa risk in Hispanic Caucasians (OR = 0.19, P = 0.04, 95% CI = 0.04–0.95) and with aggressive disease status (i.e. Gleason score ≥7) in non-Hispanic Caucasian cases (OR = 0.64, P = 0.008, 95% CI = 0.47–0.89). In the non-Hispanic Caucasian cases, a second major haplotype T-A-T-G-C-A was positively associated with the high-grade disease status (OR = 1.77, P = 0.002, 95% CI = 1.24–2.53). Our findings suggest that genetic polymorphisms in CYP1B1 may modify the risk for PCa and support the role of CYP1B1 as a candidate gene for PCa.

Metabolism of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) by human CYP1B1 genetic variants

Human cytochrome P450 1B1 (CYP1B1) plays a critical role in the metabolic activation of a variety of procarcinogens, including 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). The existence of human CYP1B1 missense genetic variants has been demonstrated, but their activities in metabolizing PhIP are unknown. In this study, we expressed 15 naturally occurring CYP1B1 variants (with either single or multiple amino acid substitutions) and determined their activity changes in metabolizing PhIP to its two major metabolites, 2-hydroxyamino-PhIP and 4'-hydroxy-PhIP. Although the PhIP-metabolizing activities of four variants (Ala(119)Ser, Pro(379)Leu, Ala(443)Gly, Arg(48)Gly/Leu(432)Val) were comparable with that of the expressed wild-type CYP1B1, five variants (Trp(57)Cys, Gly(61)Glu, Arg(48)Gly/Ala(119)Ser, Arg(48)Gly/Ala(119)Ser/Leu(432)Val, Arg(48)Gly/Ala(119)Ser/Leu(432)Val/Ala(443)Gly) exhibited more than 2-fold decrease in activity and a reduction in the catalytic efficiency (V(max)/K(m)) for both N- and 4-hydroxylation of PhIP. Six variants (Gly(365)Trp, Glu(387)Lys, Arg(390)His, Pro(437)Leu, Asn(453)Ser, Arg(469)Trp) showed little activity in PhIP metabolism, but the molecular mechanisms involved are apparently different. The microsomal CYP1B1 protein level was significantly decreased for the Trp(365), Lys(387), and His(390) variants and was not detectable for the Ser(453) variant. In contrast, there was no difference between the Trp(469) variant and the wild-type in the microsomal CYP1B1 protein level and P450 content but the Trp(469) variant totally lost its metabolic activity toward PhIP. The Leu(437) variant also had a substantial amount of CYP1B1 protein in the microsomes, but there was a lack of detectable P450 peak and activity. Our results should be useful in selecting appropriate CYP1B1 variants as cancer susceptibility biomarkers for human population studies related to PhIP exposure.

Genetic polymorphisms in cytochrome P4501B1 and susceptibility to head and neck cancer

Cytochrome P4501B1 (CYP1B1), a polycyclic aromatic hydrocarbon (PAH) metabolizing CYP, is genetically polymorphic in humans and may be involved in the individual susceptibility to chemical-induced cancer. In the present study, genotype and haplotype frequencies of four single nucleotide polymorphisms (SNPs) in CYP1B1 that cause amino acid changes (Arg-Gly at codon 48, Ala-Ser at codon 119, Leu-Val at codon 432 and Asn-Ser at codon 453) were studied in 150 cases suffering from head and neck squamous cell carcinoma (HNSCC) and in an equal number of controls. A significant difference was observed for the distribution of variant genotypes of Arg48Gly (CYP1B1*2) and Ala119Ser (CYP1B1*2) polymorphisms of CYP1B1 in cases versus controls. No significant differences were observed for the distribution of variant genotypes-Leu432Val (CYP1B1*3) and Asn453Ser (CYP1B1*4), respectively. When the four SNPs were analyzed using a haplotype approach, SNPs at codon 48 (Arg48Gly) and codon 119 (Ala119Ser) exhibited complete linkage disequilibrium (LD) in all the cases and controls. Significant differences in the distribution of the two haplotypes (G-T-C-A and G-T-G-A) were observed both in the cases and in controls. Furthermore, our data indicates a several fold increase in risk in the cases who use tobacco (cigarette smoking or tobacco chewing) or alcohol with the variant genotypes of CYP1B1 (CYP1B1*2 and CYP1B1*3) suggesting the role of gene-environment interaction in the susceptibility to HNSCC.

Single nucleotide polymorphisms and haplotypes of the genes encoding the CYP1B1 in Korean women: no association with advanced endometriosis

OBJECTIVE

To investigate whether single nucleotide polymorphisms and its haplotypes of gene encoding CYP1B1 are associated with the risk of advanced endometriosis in Korean women.

METHODS

We investigated 221 patients with histopathologically confirmed endometriosis rAFS stage III/IV and 188 control group women who were surgically proven to have no endometriosis. The genetic distribution of four different CYP1B1 polymorphisms at Ala119Ser, Leu432Val, Asp(449)(C>T), Asn453Ser were analyzed by polymerase chain reaction (PCR) and restriction fragment length polymorphism of PCR products. Haplotype analysis was also performed.

RESULTS

We found no overall association between each individual CYP1B1 genotype or haplotype and the risk of endometriosis. Also, the odds ratio of each haplotypes of CYP1B1 showed no association with the risk of endometriosis.

CONCLUSIONS

These results suggest that CYP1B1 genetic polymorphism may not be associated with development of advanced endometriosis in Korean women.

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.

Systematic replication study of reported genetic associations in prostate cancer: Strong support for genetic variation in the androgen pathway

BACKGROUND

Association studies have become a common and popular method to identify genetic variants predisposing to complex diseases. Despite considerable efforts and initial promising findings, the field of prostate cancer genetics is characterized by inconclusive reports and no prostate cancer gene has yet been established.

METHODS

We performed a literature review and identified 79 different polymorphisms reported to influence prostate cancer risk. Of these, 46 were selected and tested for association in a large Swedish population-based case-control prostate cancer population.

RESULTS

We observed significant (P < 0.05) confirmation for six polymorphisms located in five different genes. Three of them coded for key enzymes in the androgen biosynthesis and response pathway; the CAG repeat in the androgen receptor (AR) gene (P = 0.03), one SNP in the CYP17 gene (P = 0.04), two SNPs in the SRD5A2 gene (P = 0.02 and 0.02, respectively), a deletion of the GSTT1 gene (P = 0.006), and one SNP in the MSR1 gene, IVS5-59C > A, (P = 0.009).

CONCLUSIONS

Notwithstanding the difficulties to replicate findings in genetic association studies, our results strongly support the importance of androgen pathway genes in prostate cancer etiology.

Polymorphisms in polycyclic aromatic hydrocarbon metabolism and conjugation genes, interactions with smoking and prostate cancer risk

The relationship between cigarette smoking and prostate cancer remains unclear. Any potential association may depend on the individuals' ability to metabolize and detoxify cigarette carcinogens--such as polycyclic aromatic hydrocarbons. To investigate this, we studied the association between prostate cancer and smoking, as well as the main and modifying effects of functional polymorphisms in genes that metabolize polycyclic aromatic hydrocarbons (CYP1A1 Ile(462)Val, microsomal epoxide hydrolase His(139)Arg) and detoxify reactive derivatives (GSTM1 null deletion, GSTT1 null deletion, GSTP1 Ile(105)Val and Ala(114)Val) using a family-based case-control design (439 prostate cancer cases and 479 brother controls). Within the entire study population, there were no main effects for smoking or any of the polymorphisms. However, the nondeleted GSTM1 allele was inversely associated with prostate cancer [odds ratio (OR), 0.50; 95% confidence interval (95% CI), 0.26-0.94] among men with less aggressive disease (Gleason score < 7 and clinical tumor stage < T2c) and positively associated (OR, 1.68; 95% CI, 1.01-2.79) with prostate cancer in men with more aggressive disease (Gleason score > or = 7 or clinical tumor stage > or = T2c). We also found a statistically significant negative multiplicative interaction between the GSTM1 nondeleted allele and heavy smoking (> 20 pack-years) in the total study population (P = 0.01) and in Caucasians (P = 0.01). Among Caucasians, heavy smoking increased prostate cancer risk nearly 2-fold in those with the GSTM1 null genotype (OR, 1.73; 95% CI, 0.99-3.05) but this increased risk was not observed in heavy smokers who carried the GSTM1 nondeleted allele (OR, 0.95; 95% CI, 0.53-1.71). Our results highlight the importance of considering genetic modifiers of carcinogens when evaluating smoking in prostate cancer.

Role of the aryl hydrocarbon receptor in drug metabolism

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that regulates the transcription of certain key enzymes involved in the metabolism of xenobiotic substances including some drugs. The AhR can be activated by a wide range of classes of compounds (e.g. polycyclic aromatic hydrocarbons, benzimidazoles and flavonoids), and interacts with a number of other proteins, including nuclear hormone receptors such as the oestrogen and androgen receptors. Activation of the AhR antagonises the oestrogen receptor and can lead to modulation of its transcriptional activity; thus, activating the AhR may serve as a target for breast cancer therapy. Disruption of normal signalling by drug interactions with the AhR or downstream components of this pathway could result in adverse effects, such as the bioactivation of procarcinogens or the disruption of normal homeostasis. The cytochrome P450s CYP1A1, -1B1, -1A2 and -2S1 are regulated by the AhR, and they are all involved in the metabolism of endogenous substrates as well as xenobiotics. Polymorphisms in the AhR, or polymorphisms in enzymes regulated by the AhR, may cause variations in response to certain drugs in different individuals; this needs to be taken into consideration when administering drugs that interact with this pathway.

Pharmacogenetics and regulation of human cytochrome P450 1B1: implications in hormone-mediated tumor metabolism and a novel target for therapeutic intervention

Several of the hormone-mediated cancers (breast, endometrial, ovarian, and prostate) represent major cancers in both incidence and mortality rates. The etiology of these cancers is in large part modulated by the hormones estrogen and testosterone. As advanced disease develops, the common treatment for these cancers is chemotherapy. Thus, genes that can alter tissue response to hormones and alter clinical response to chemotherapy are of major interest. The cytochrome P450 1B1 (CYP1B1) may be involved in disease progression and modulate the treatment in the above hormone-mediated cancers. This review will focus on the pharmacogenetics of CYP1B1 in relation to hormone-mediated cancers and provide an assessment of cancer risk based on CYP1B1 polymorphisms and expression. In addition, it will provide a summary of CYP1B1 gene regulation and expression in normal and neoplastic tissue.

Role of Androgen Metabolism Genes CYP1B1, PSA/KLK3, and CYP11 in Prostate Cancer Risk and Aggressiveness

Candidate genes involved with androgen metabolism have been hypothesized to affect the risk of prostate cancer. To further investigate this, we evaluated the relationship between prostate cancer and multiple potentially functional polymorphisms in three genes involved in androgen metabolism: CYP1B1 (two single nucleotide polymorphisms: 355G/T and 4326C/G), prostate-specific antigen (PSA/KLK3 (three single nucleotide polymorphisms: -158A/G, -4643G/A, and -5412C/T), and CYP11alpha [(tttta)(n) repeat], using a moderately large (n = 918) sibling-based case-control population. When looking at all subjects combined, no association was observed between any polymorphism-or their haplotypes-and prostate cancer risk. However, among men with more aggressive prostate cancer, the CYP1B1 355G/T variant was positively associated with disease: carrying one or two T alleles gave odds ratios (OR) of 1.90 [95% confidence interval (95% CI), 1.09-3.31; P = 0.02] and 3.73 (95% CI, 1.39-10.0; P = 0.009), respectively. Similarly, carrying the CYP1B1 355T-4326C haplotype was positively associated with prostate cancer among men with high aggressive disease (P = 0.01). In addition, the PSA -158G/-158G genotype was positively associated with prostate cancer among men with less aggressive disease (OR, 2.71; 95% CI, 1.06-6.94; P = 0.04). Our findings suggest that CYP1B1 and PSA variants may affect the risk of prostate cancer and tumor aggressiveness.

Characterization of common CYP1B1 variants with different capacity for benzo[a]pyrene-7,8-dihydrodiol epoxide formation from benzo[a]pyrene

Cytochrome P450 1B1 (CYP1B1), an extrahepatic enzyme inducible by smoking, is overexpressed in many tumors and catalyzes the metabolic activation of procarcinogens such as polycyclic aromatic hydrocarbons. In human, CYP1B1 is genetically polymorphic and five common missense mutations causing amino acid substitution have been identified. In this study, we have investigated CYP1B1 haplotypes present in a Spanish population and carried out functional analyses of the corresponding enzymes in yeast using benzo[a]pyrene as a substrate. CYP1B1*1, CYP1B1*2, CYP1B1*3, CYP1B1*4, CYP1B1*6, and CYP1B1*7, encoding combinations of the Arg48Gly, Ala119Ser, Leu432Val, Asn453Ser, and Ala443Gly amino acid substitutions, were present at frequencies of 14.3%, 25.5%, 38.8%, 18.1%, 0.4%, and 2.6%, respectively. The variant CYP1B1 forms were heterologously expressed with human reductase in Saccharomyces cerevisiae and kinetic analyses of benzo[a]pyrene metabolism were carried out. CYP1B1.7, having the amino acid substitutions Arg48Gly, Ala119Ser, Leu432Val, and Ala443Gly, exhibited a significantly decreased capacity (P < 0.001) for the formation of (+/-)-benzo[a]pyrene-trans-7,8-dihydrodiol from benzo[a]pyrene as indicated by lower intrinsic clearance (Vmax/Km). A somewhat decreased clearance was observed for CYP1B1.4, whereas no significant differences in kinetic properties among the remaining variant enzymes were observed as compared with CYP1B1.1. Thus, genetic polymorphism in the CYP1B1 gene, as defined by the haplotypes investigated, might cause interindividual differences in susceptibility (e.g., to lung cancer induced by smoking). The results indicate the necessity to make molecular epidemiologic investigations regarding the association of the specific CYP1B1 haplotypes and cancer risk.

A comprehensive analysis of phase I and phase II metabolism gene polymorphisms and risk of colorectal cancer

OBJECTIVES

Sporadic colorectal cancer (CRC) is considered a multifactorial disease where multiple exposures interact with the individual genetic background resulting in risk modulation. We performed an association study aimed to investigate the role of single nucleotide polymorphisms (SNPs) within genes of phase I (CYP1A1, CYP1A2, CYP1B1, CYP2A6, CYP2D6, CYP2E1, CYP2C9, CYP2C19, CYP3A4, ADH2, EPHX1) and phase II of the xenobiotic metabolism (ALDH2, COMT, GSTA2, GSTA4, GSTM1, GSTM3, GSTP1, GSTT2, MTHFR, NAT1, NAT2, NQO1, MnSOD2, SULT1A1, TPMT).

METHODS

We genotyped 377 cases and 326 controls, by use of an oligonucleotide micro-array and the arrayed primer extension technique (APEX).

RESULTS

N-acetyl-transferase 1 'rapid' phenotype and CYP1A2 -164C>A carriers were associated with increased risk of CRC, confirming data reported in previous studies. Interestingly, homozygotes for allele 48G within CYP1B1, a variant with an increased activity towards several substrates including sex hormones, were at increased risk (OR=2.81, 95% CI 1.32-5.99). Moreover, CYP1A1 SNPs T461N and -1738A>C were associated with a reduced risk of cancer (OR=0.52; 95% CI 0.31-0.88 and OR=0.69, 95% CI 0.50-0.94 for carriers, respectively).

CONCLUSIONS

The present data suggest a role for CYP1B1 and CYP1A1 as new candidate genes in the etiology of CRC and confirm the carcinogenic role of aromatic amines metabolism for colorectum.

Immunolocalization of CYP1B1 in normal, human, fetal and adult eyes

CYP1B1 is a cytochrome P450 enzyme implicated in autosomal recessive primary congenital glaucoma (PCG). The mechanism and function of CYP1B1 in the development of the PCG phenotype is unknown. Previously, investigators have reported detection of Cyp1b1 mRNA in the ciliary body and epithelium and neuroepithelium in the developing mouse eye, employing in situ hybridization techniques. Similarly, additional investigators have detected CYP1B1 mRNA in the iris, ciliary body, non-pigmented ciliary epithelial line, cornea, retinal-pigment epithelium, and retina in the human adult eye, using Northern blotting. This study was designed to immunolocalize CYP1B1 protein in the various ocular structures of normal, human fetal and adult eyes. Normal fetal and adult eyes were immunolabeled with a polyclonal antibody against human CYP1B1 using indirect immunofluorescence, and then compared with appropriate controls. The intensity of immunolabeling of the various ocular structures was assessed by qualitative and semi-quantitative techniques. In the anterior segment anti-CYP1B1 immunoreactivity (IR) was detected early in fetal development in the primitive ciliary epithelium. As well, the most intense CYP1B1 IR was in the non-pigmented ciliary epithelium. In addition, CYP1B1 IR was also present in the corneal epithelium and keratocytes, both layers of the iris pigmented epithelium, and retina. However, CYP1B1 IR was absent in the trabecular meshwork in all of the samples. In general, CYP1B1 immunolabeling in the human fetal eyes was more intense when compared to adult eyes. CYP1B1 IR was primarily immunolocalized to the non-pigmented ciliary epithelium and early in fetal development. In addition, CYP1B1 IR was not detected in the trabecular meshwork. These findings suggest that the abnormalities in the development of the trabecular meshwork in PCG may result from diminished or absent metabolism of important endogenous substrates in the ciliary epithelium due to non-functional CYP1B1 enzyme.

Mechanisms of Disease: polymorphisms of androgen regulatory genes in the development of prostate cancer

Androgens are of primary importance in the etiology of prostate cancer, and binding of the androgen dihydrotestosterone to the androgen receptor is thought to stimulate prostate growth. It has been proposed that polymorphisms within key androgen regulatory genes may contribute to an individual's risk of developing prostate cancer. Attributing single polymorphisms to complex, late-onset, chronic diseases such as prostate cancer is probably not feasible, but identification of genes that increase risk will contribute to larger-scale multigenic risk assessment. Here, we review the current status of our knowledge of associations between important androgen regulatory gene polymorphisms and prostate cancer risk.

CYP1A1 and CYP1B1 genotypes, haplotypes, and TCDD-induced gene expression in subjects from Seveso, Italy

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is highly toxic in experimental animals, and is known to induce cytochrome P450 (CYP) gene expression. We investigated the effect of CYP1A1 and CYP1B1 variant genotypes and haplotypes on CYP1A1 and CYP1B1 mRNA expression and ethoxyresorufin-O-deethylase (EROD) activity in lymphocytes from 121 subjects from the Seveso population, Italy, accidentally exposed to TCDD in 1976. The 3'UTR 3801T>C and I462V variants of CYP1A1 were present in 16% and 6% of the subjects, respectively. The frequency of CYP1B1 variants was 85.2% for L432V, 49.6% for R48G and A119S, and 28.7% for N453S. There was complete linkage disequilibrium (LD) among the CYP1B1 variant loci (D'=-1) and high LD among the CYP1A1 loci (D'=0.86). Gene expression measured by RT-PCR did not vary by CYP1B1 genotype in uncultured lymphocytes. However, when lymphocytes were treated in vitro with 10 nM TCDD, CYP1B1 and CYP1A1 mRNA expression was strongly induced and modified by CYP variant alleles. Specifically, the CYP1B1*3 haplotype (L432V) was associated with increased CYP1B1 mRNA expression (P=0.03), following an additive model; the CYP1A1 I462V polymorphism was positively, although not significantly, associated with CYP1A1 expression. The CYP1B1*3 variant may have affected CYP1B1 expression in subjects highly and acutely exposed to dioxin at the time of the accident. Although based on small number of subjects, a slight increase in eczema (P=0.05, n=8) and urticaria (P=0.02, n=2) was observed 20 years after the accident in subjects carrying the CYP1B1*3 allele. Genetic variation in cytochrome P450 induction may identify subjects with variable responsiveness to TCDD and potentially increased risk of disease.

Predictive models for breast cancer susceptibility from multiple single nucleotide polymorphisms

Hereditary predisposition and causative environmental exposures have long been recognized in human malignancies. In most instances, cancer cases occur sporadically, suggesting that environmental influences are critical in determining cancer risk. To test the influence of genetic polymorphisms on breast cancer risk, we have measured 98 single nucleotide polymorphisms (SNPs) distributed over 45 genes of potential relevance to breast cancer etiology in 174 patients and have compared these with matched normal controls. Using machine learning techniques such as support vector machines (SVMs), decision trees, and naïve Bayes, we identified a subset of three SNPs as key discriminators between breast cancer and controls. The SVMs performed maximally among predictive models, achieving 69% predictive power in distinguishing between the two groups, compared with a 50% baseline predictive power obtained from the data after repeated random permutation of class labels (individuals with cancer or controls). However, the simpler naïve Bayes model as well as the decision tree model performed quite similarly to the SVM. The three SNP sites most useful in this model were (a) the +4536T/C site of the aldosterone synthase gene CYP11B2 at amino acid residue 386 Val/Ala (T/C) (rs4541); (b) the +4328C/G site of the aryl hydrocarbon hydroxylase CYP1B1 at amino acid residue 293 Leu/Val (C/G) (rs5292); and (c) the +4449C/T site of the transcription factor BCL6 at amino acid 387 Asp/Asp (rs1056932). No single SNP site on its own could achieve more than 60% in predictive accuracy. We have shown that multiple SNP sites from different genes over distant parts of the genome are better at identifying breast cancer patients than any one SNP alone. As high-throughput technology for SNPs improves and as more SNPs are identified, it is likely that much higher predictive accuracy will be achieved and a useful clinical tool developed.

CYP1B1 expression in prostate is higher in the peripheral than in the transition zone

Prostate cancer (CaP) mostly occurs in the peripheral zone whereas benign prostatic hypertrophy (BPH) occurs in the transition zone. Human prostates (n = 12) were obtained, with ethical approval, from radical retropubic prostatectomies. Following resection, tissue sets consisting of peripheral zone and transition zone were isolated from a lobe pre-operatively identified as negative for CaP. Real-time RT-PCR was employed to quantitatively examine CYP1A1, CYP1A2 and CYP1B1. Quantifiable CYP1A1 expression was observed (in nine out of twelve tissue sets) whilst CYP1A2 mRNA transcripts, although detectable (in six out of twelve tissue sets), were unquantifiable. In ten tissue sets, 2- to 6-fold higher CYP1B1 expression in peripheral zone as compared to transition zone was observed. In the other two, equal CYP1B1 expression levels were observed; retrospective examination identified malignancy in one of the zones. Inter-individual variations (up to 10-fold) in CYP1B1 were also noted. Immunohistochemistry for CYP1B1 showed epithelial and stromal nuclear staining. Since CYP1B1 metabolises hormones and carcinogens our results, if confirmed, suggest that this enzyme may influence susceptibility to CaP.