Catechol-O-Methyltransferase (COMT) gene polymorphism and breast cancer risk in young women

Influence of catechol-O-methyltransferase enzyme gene polymorphism on alcohol and tobacco consumption in North Indian treatment seeking population

BACKGROUND

The co-occurrence of alcohol and tobacco dependence is frequently witnessed in treatment settings. It is a challenge for clinicians to treat such patients due to their powerful biological association.

AIM

The study is aimed to assess the relationship of Catechol-O-methyltransferase (COMT) Val158Met polymorphism with substance intake among individuals who are dependent on both alcohol and tobacco.

MATERIALS AND METHODS

A cross-sectional study involving patients coming to the outpatient department was planned. Brief information on their sociodemographic and substance use profile was recorded. Genotyping of COMT Val158Met was carried out using established polymerase chain reaction-restriction fragment length polymorphism method. The COMT genotyping was classified based on the presence or absence of Met allele using the dominant model. Descriptive statistics, Chi-square test, Mann-Whitney test, and Binary logistic regression analysis were performed to analyze the data.

RESULTS

The study included 104 alcohol and nicotine co-dependent subjects. More than eighty percent of the participants were educated above secondary level, married, and employed. The allele frequencies of met and Val were found to be 0.23 and 0.77, respectively. Forty percent of the participants reported tobacco-related health problems. The odds of consuming alcohol and nicotine were four times high among Met allele carriers. While the Fagerström test for nicotine dependence and heaviness of smoking index scores were up to four and eight times higher among met allele (odds ratio 4.3 and 8.9, respectively).

CONCLUSION

Patients carrying Met allele are reported to consume higher amounts of alcohol and tobacco and were likely to score high among measures of nicotine dependence. Thus met allele carriers needs additional attention for a successful treatment outcome.

The association of genetic polymorphisms with neuroconnectivity in breast cancer patients

Genetic polymorphisms in select genes, including APOE (apolipoprotein E), COMT (Catechol-O-Methyltransferase), MDR1 (multi-drug resistance 1), BDNF (brain derived neurotrophic factor), and GST (glutathione-S-transferase), have been associated with vulnerability to cognitive impairment. In this study, we evaluated the relationship of these genetic variants to measures of brain health in patients with breast cancer, including neurocognitive testing and functional connectome analysis. Women with breast cancer (n = 83) and female healthy controls (n = 53) were evaluated. They underwent resting-state functional MRI scans and neurocognitive testing. Polymerase chain reaction (PCR) was performed on saliva samples to identify single nucleotide polymorphisms (SNPs) in candidate genes: APOE, COMT, MDR1, BDNF, and GST. Breast cancer patients treated with chemotherapy had slower processing speed (p = 0.04) and poorer reported executive function (p < 0.0001) than healthy controls. Those chemotherapy-treated patients that were APOE e4 carriers had significantly slower processing speed. A greater number of risk-related alleles was associated with poorer connectivity in the regions of the left cuneus and left calcarine. While breast cancer patients that are APOE e4 carriers may have a select vulnerability to processing speed impairments, other risk-related alleles were not found to influence cognitive test performance in this population. Conversely, regions of impaired functional connectivity appeared to be related to risk-related genetic polymorphisms in breast cancer patients. This suggests that a cancer patient’s SNPs in candidate genes may influence the risk of neurotoxicity. Further study evaluating the impact of genotype on biomarkers of brain health in cancer survivors is warranted.

Neural anomalies during vigilance in schizophrenia: Diagnostic specificity and genetic associations

Impaired vigilance is a core cognitive deficit in schizophrenia and may serve as an endophenotype (i.e., mark genetic liability). We used a continuous performance task with perceptually degraded stimuli in schizophrenia patients (N = 48), bipolar disorder patients (N = 26), first-degree biological relatives of schizophrenia patients (N = 55) and bipolar disorder patients (N = 28), as well as healthy controls (N = 68) to clarify whether previously reported vigilance deficits and abnormal neural functions were indicative of genetic liability for schizophrenia as opposed to a generalized liability for severe psychopathology. We also examined variation in the Catechol-O-methyltransferase gene to evaluate whether brain responses were related to genetic variation associated with higher-order cognition. Relatives of schizophrenia patients had an increased rate of misidentification of nontarget stimuli as targets when they were perceptually similar, suggestive of difficulties with contour perception. Larger early visual responses (i.e., N1) were associated with better task performance in patients with schizophrenia consistent with enhanced N1 responses reflecting beneficial neural compensation. Additionally, reduced N2 augmentation to target stimuli was specific to schizophrenia. Both patients with schizophrenia and first-degree relatives displayed reduced late cognitive responses (P3b) that predicted worse performance. First-degree relatives of bipolar patients exhibited performance deficits, and displayed aberrant neural responses that were milder than individuals with liability for schizophrenia and dependent on sex. Variation in the Catechol-O-methyltransferase gene was differentially associated with P3b in schizophrenia and bipolar groups. Poor vigilance in schizophrenia is specifically predicted by a failure to enhance early visual responses, weak augmentation of mid-latency brain responses to targets, and limited engagement of late cognitive responses that may be tied to genetic variation associated with prefrontal dopaminergic availability. Experimental results illustrate specific neural functions that distinguish schizophrenia from bipolar disorder and provides evidence for a putative endophenotype that differentiates genetic liability for schizophrenia from severe mental illness more broadly.

Cancer Biology and Prevention in Diabetes

The available evidence suggests a complex relationship between diabetes and cancer. Epidemiological data suggest a positive correlation, however, in certain types of cancer, a more complex picture emerges, such as in some site-specific cancers being specific to type I diabetes but not to type II diabetes. Reports share common and differential mechanisms which affect the relationship between diabetes and cancer. We discuss the use of antidiabetic drugs in a wide range of cancer therapy and cancer therapeutics in the development of hyperglycemia, especially antineoplastic drugs which often induce hyperglycemia by targeting insulin/IGF-1 signaling. Similarly, dipeptidyl peptidase 4 (DPP-4), a well-known target in type II diabetes mellitus, has differential effects on cancer types. Past studies suggest a protective role of DPP-4 inhibitors, but recent studies show that DPP-4 inhibition induces cancer metastasis. Moreover, molecular pathological mechanisms of cancer in diabetes are currently largely unclear. The cancer-causing mechanisms in diabetes have been shown to be complex, including excessive ROS-formation, destruction of essential biomolecules, chronic inflammation, and impaired healing phenomena, collectively leading to carcinogenesis in diabetic conditions. Diabetes-associated epithelial-to-mesenchymal transition (EMT) and endothelial-to-mesenchymal transition (EndMT) contribute to cancer-associated fibroblast (CAF) formation in tumors, allowing the epithelium and endothelium to enable tumor cell extravasation. In this review, we discuss the risk of cancer associated with anti-diabetic therapies, including DPP-4 inhibitors and SGLT2 inhibitors, and the role of catechol-o-methyltransferase (COMT), AMPK, and cell-specific glucocorticoid receptors in cancer biology. We explore possible mechanistic links between diabetes and cancer biology and discuss new therapeutic approaches.

COMT and Alpha-Tocopherol Effects in Cancer Prevention: Gene-Supplement Interactions in Two Randomized Clinical Trials

BACKGROUND

Vitamins are among the most frequently used supplements (48% of US adults). However, little is known about contributions of genetic variation to their efficacy and safety. Multiple pathways link catechol-O-methyltransferase (COMT) to the vitamin E supplement, alpha-tocopherol, and cancer.

METHODS

Here we determined if COMT exerted pharmacogenetic effects on cancer prevention in two randomized trials of alpha-tocopherol supplementation. Pharmacogenetic effects of common COMT rs4680 (val158met), which encodes a nonsynonymous valine-to-methionine substitution, were examined in the trial plus a 10-year post-trial follow-up (overall) period of The Women's Genome Health Study (WGHS, N = 23 294), a 10-year alpha-tocopherol and aspirin trial with 10 years post-trial follow-up. Results were validated in a case/control (N = 2396/2235) subset of the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study (ATBC, N = 29 133). The primary outcome was total cancers. Rates of cancer types prevalent in women (colorectal, breast, lung, uterine, and lymphoma/leukemia) were also examined. All statistical tests were two-sided.

RESULTS

Random-effects meta-analysis of rs4680 genotype strata, in WGHS and ATBC overall periods, revealed differential alpha-tocopherol effects compared with placebo: met/met (hazard ratio [HR] = 0.88; 95% confidence interval [CI] = 0.80 to 0.97; P = .01), val/met (HR = 0.99; 95% CI = 0.92 to 1.06; P = .74), and val/val (HR = 1.18; 95% CI = 1.06 to 1.31; P = .002) with a statistically significant COMT by alpha-tocopherol interaction (Pinteraction <.001). Timing of effects differed, with stronger effects in WGHS trial and ATBC post-trial.

CONCLUSION

Pharmacogenetic analysis of COMT and cancer prevention in two large randomized trials revealed statistically significant COMT by alpha-tocopherol interaction, such that alpha-tocopherol was beneficial among rs4680 met-allele (28.0%), but not val-allele (22.8%) homozygotes. These effects indicate the need for additional studies of genetic variation as a determinant of the benefits and possible harms of over-the-counter supplements, like alpha-tocopherol, used for health promotion.

The Val158Met polymorphism in COMT gene and cancer risk: role of endogenous and exogenous catechols

Catechol-O-methyltransferase, COMT, is an important phase II enzyme catalyzing the transfer of a methyl-group from S-adenosylmethionine to a catechol-containing substrate molecule. A genetic variant Val158Met in the COMT gene leads to a several-fold decrease in the enzymatic activity giving rise to the accumulation of potentially carcinogenic endogenous catechol estrogens and their reactive intermediates and increasing thus the risk of tumorigenesis. However, numerous association studies between the COMT genotype and susceptibility to various malignancies have shown inconsistent and controversial findings indicating that additional gene-gene and gene-environment interactions might be crucial in modulating the physiological role of the COMT. In this review article, the important contribution of dietary catechol-containing flavonoids to modification of the relationships between the COMT genotype and cancer risk is discussed. Whereas, the diverse anticancer activities of common phytochemicals, such as green tea polyphenols, quercetin, fisetin or luteolin, can be markedly changed (both decreased or increased) by the COMT-mediated O-methylation of these exogenous substrates, flavonoids can also behave as potent inhibitors of the COMT enzyme slowing detoxification of endogenous catechol estrogens. Such a many-featured functioning of the COMT and its complex regulation by several different genetic and environmental factors, including plant-based food ingredients, emphasizes the necessity to further stratify the association studies between the COMT genotype and tumor risk by consumption of catechol-containing dietary flavonoids. Currently, it can be only speculated that some of the possible associations might be masked by the regular intake of specific food polyphenols, taking effect in certain communities or populations.

Association between the COMT Val158Met polymorphism and risk of cancer: evidence from 99 case-control studies

Catechol-O-methyltransferase (COMT) plays a central role in DNA repair and estrogen-induced carcinogenesis. Many recent epidemiologic studies have investigated the association between the COMT Val158Met polymorphism and cancer risk, but the results are inconclusive. In this study, we performed a meta-analysis to investigate the association between cancer susceptibility and COMT Val158Met in different genetic models. Overall, no significant associations were found between COMT Val158Met polymorphism and cancer risk (homozygote model: odds ratio [OR] =1.05, 95% confidence interval [CI] = [0.98, 1.13]; heterozygote model: OR =1.01, 95% CI = [0.98, 1.04]; dominant model: OR =1.02, 95% CI [0.97, 1.06], and recessive model: OR =1.03, 95% CI [0.97, 1.09]). In the subgroup analysis of cancer type, COMT Val158Met was significantly associated with increased risks of bladder cancer in recessive model, and esophageal cancer in homozygote model, heterozygote model, and dominant model. Subgroup analyses based on ethnicities, COMT Val158Met was significantly associated with increased risk of cancer in homozygote and recessive model among Asians. In addition, homozygote, recessive, and dominant models were significantly associated with increased cancer risk in the subgroup of allele-specific polymerase chain reaction genotyping. Significant associations were not observed when data were stratified by the source of the controls. In summary, this meta-analysis suggested that COMT Val158Met polymorphism might not be a risk factor for overall cancer risk, but it might be involved in cancer development at least in some ethnic groups (Asian) or some specific cancer types (bladder and esophageal cell cancer). Further evaluations of more preclinical and epidemiological studies are required.

Catechol-O-methyltransferase inhibits colorectal cancer cell proliferation and invasion

BACKGROUND AND AIMS

Catechol-O-methyltransferase (COMT) has been reported as an important molecule in various types of cancers. The biological function of COMT in colorectal cancer (CRC) has not yet been fully investigated.

METHODS

We constructed a transient transfection of a CRC cell lines to up- and downregulate COMT expression level and tested the proliferative, invasion ability in vitro. We also constructed a stable transduced CRC cell line and conducted tumor-forming capacity experiment in mouse xenograft model in vivo.

RESULTS

In vitro experiment showed that COMT inhibited the cell proliferation by regulating p-Akt, PTEN and inhibited G1 to S phase transition by regulating p53, p27, and cyclinD1. COMT inhibited invasion by regulating E-cadherin. In vivo experiment showed decreased tumor growth in COMT overexpressing cell line.

CONCLUSIONS

COMT has tumor-suppressive functions for CRC cell lines in vitro and in vivo experiments.

The catechol-o-methyltransferase Val158 Met polymorphism modulates organization of regional cerebral blood flow response to working memory in adults

This study examined the effect of catechol-o-methyltransferase (COMT) Val(158)Met genotypes on the co-activation of brain areas involved in cognition during a working memory (WM) task. The pattern of concomitant region of interest (ROI) activation during WM performance varied by genotype: Val/Val showing the least and Met/Met the most covariance. There were no differences of performance on the WM task between the COMT genotypes. However, relatively better performance was associated with less concomitance of dorsolateral prefrontal cortex (DLPFC) and cingulate cortex for Val/Val, but more concomitance of DLPFC with AH for Met/Met. Within genotypes WM performance was significantly correlated with rCBF to the amygdala/hippocampus (AH) for Val/Val (r = 0.44, p = 0.009), to the parietal lobe for Val/Met (r = 0.29, p = 0.03), and to the thalamus for Met/Met (r = 0.32, p = 0.04). Different genotypes showed different regional specificity and concomitant activation patterns suggesting that varying dopamine availability induces different brain processing pathways to achieve similar WM performance.

Association of COMT Val158Met polymorphism and breast cancer risk: an updated meta-analysis

BACKGROUND

Catechol-O-methyltransferase (COMT) is one of the most important enzymes involved in estrogen metabolism and its functional genetic polymorphisms may be associated with breast cancer (BC) risk. Many epidemiological studies have been conducted to explore the association between the COMT Val158Met polymorphism and breast cancer risk. However, the results remain inconclusive. In order to derive a more precise estimation of this relationship, a large meta-analysis was performed in this study.

METHODS

Systematic searches of the PubMed, Embase and Cochrane Library were performed. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to estimate the strength of the association.

RESULTS

A total of 56 studies including 34,358 breast cancer cases and 45,429 controls were included. Overall, no significant associations between the COMT Val158Met polymorphism and breast cancer risk were found for LL versus HH, HL versus HH, LL versus HL, recessive model LL versus HL+HH, and dominant model LL+HL versus HH. In subgroup analysis by ethnicity, source of controls, and menopausal status, there was still no significant association detected in any of the genetic models.

CONCLUSION

Our meta-analysis results suggest that the COMT Val158Met polymorphism may not contribute to breast cancer susceptibility.

VIRTUAL SLIDES

The virtual slides(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs4806123577708417.

Catechol-O-methyltransferase Val 108/158 Met polymorphism and breast cancer risk: a case control study in Syria

BACKGROUND

Catechol-O-methyltransferase (COMT) inactivates catechol estrogens by methylation and thus may play a protective role against mutations induced by estrogen metabolites. In this study we investigated the relationship between the Vall58Met polymorphism in the COMT gene and breast cancer risk in a population-based case control study in Syria.

METHODS

We examined 135 breast cancer patients and 107 healthy controls in North Syria to determine the association between the functional genetic Val158Met polymorphism in the COMT gene and female breast cancer risk.

RESULTS

There was no significant overall association between the COMT genotype and individual susceptibility to breast cancer.

CONCLUSIONS

Our data suggest that there may be no overall association between the COMT genotype and breast cancer.

Lack of association between catechol-O-methyltransferase Val108/158Met polymorphism and breast cancer risk: a meta-analysis of 25,627 cases and 34,222 controls

Epidemiological studies have evaluated the association between catechol-O-methyltransferase (COMT) Val108/158Met polymorphism and breast cancer risk. However, the results remain conflicting rather than conclusive. In order to derive a more precise estimation of the relationship, we performed this meta-analysis. Systematic searches of the PubMed and Medline databases were performed. A total of 41 studies including 25,627 cases and 34,222 controls were identified. Genotype distributions of COMT in the controls of all studies were in agreement with the Hardy-Weinberg equilibrium (HWE) except for three studies. When all 41 studies were pooled into the meta-analysis, there was no evidence for significant association between COMT Val108/158Met polymorphism and breast cancer risk (for Val/Met vs. Val/Val: OR = 0.99, 95% CI = 0.93-1.04; for Met/Met vs. Val/Val: OR = 0.96, 95% CI = 0.88-1.04; for dominant model: OR = 0.97, 95% CI = 0.92-1.03; for recessive model: OR = 0.97, 95% CI = 0.90-1.04). In the subgroup analyses by ethnicity, menopausal status, no significant associations were found in all genetic models. When sensitivity analyses were performed by excluding HWE-violating studies, all the results were not materially altered. In summary, the meta-analysis strongly suggests that COMT Val108/158Met polymorphism is not associated with increased breast cancer risk.

Genetic and disorder-specific aspects of resting state EEG abnormalities in schizophrenia

We evaluated whether abnormal frequency composition of the resting state electroencephalogram (EEG) in schizophrenia was associated with genetic liability for the disorder by studying first-degree biological relatives of schizophrenia patients. The study included a data-driven method for defining EEG frequency components and determined the specificity of resting state EEG frequency abnormalities by assessing schizophrenia patients, bipolar disorder patients, and relatives of both patient groups. Schizophrenia patients and their relatives, but not bipolar patients or their relatives, exhibited increased high-frequency activity (beta) providing evidence for disturbances in resting state brain activity being specific to genetic liability for schizophrenia. Schizophrenia patients exhibited augmented low-frequency EEG activity (delta, theta), while bipolar disorder patients and the 2 groups of relatives generally failed to manifest similar low-frequency EEG abnormalities. The Val(158)Met polymorphism for the catechol-O-methyl transferase (COMT) gene was most strongly associated with delta and theta activity in schizophrenia patients. Met homozygote schizophrenia patients exhibited augmented activity for the 2 low-frequency bands compared with control subjects. Excessive high-frequency EEG activity over frontal brain regions may serve as an endophenotype that reflects cortical expression of genetic vulnerability for schizophrenia. Low-frequency resting state EEG anomalies in schizophrenia may relate to disorder-specific pathophysiology in schizophrenia and the influence of the COMT gene on tonic dopamanergic function.

Anhedonia as a phenotype for the Val158Met COMT polymorphism in relatives of patients with schizophrenia

The Val(158)Met polymorphism of the catechol-O-methyltransferase (COMT) gene has been associated with aspects of schizophrenia that are possibly related to the disorder's pathogenesis. The present study investigated the Val(158)Met polymorphism in relation to anhedonia--a construct central to negative schizotypy. Anhedonia and other schizotypal characteristics were assessed in relatives of patients with schizophrenia, relatives of patients with bipolar disorder, and nonpsychiatric controls using the Chapman schizotypy scales and the Schizotypal Personality Questionnaire. Compared with controls, relatives of individuals with schizophrenia had elevated scores on Chapman scales for social anhedonia and physical anhedonia, while relatives of patients with bipolar disorder exhibited only increased scores on the Social Anhedonia Scale. As a group, relatives of patients with schizophrenia who were homozygous for the val allele of the COMT polymorphism showed the highest elevations in self-reported social and physical anhedonia. Associations with the COMT polymorphism were absent in relatives of patients with bipolar disorder and control participants. Findings suggest that anhedonia is manifest in individuals who carry genetic liability for schizophrenia and is associated with the Val(158)Met polymorphism of the COMT gene.

Differential association of the COMT Val158Met polymorphism with clinical phenotypes in schizophrenia and bipolar disorder

Schizophrenia and bipolar disorder, although diagnostically separate, likely share elements of their genetic etiology. This study assessed whether the COMT Val158Met polymorphism has shared or specific associations with clinical phenotypes evident in schizophrenia and bipolar disorder. Schizophrenia and bipolar patients completed a clinical assessment encompassing premorbid functioning and current and lifetime symptomatology. Multivariate analyses yielded a three-way interaction of diagnosis, COMT genotype for lifetime symptomatology. The COMT Val allele was associated with greater positive symptomatology in schizophrenia, whereas Met homozygosity was associated with greater positive symptomatology in bipolar disorder. Findings support the COMT Val158Met polymorphism conferring vulnerability for different clinical phenotypes in schizophrenia and bipolar disorder. Lifetime symptomatology may be particularly useful in determining the relationship between genes and clinical phenotypes across mental disorders.

Sex steroid-related candidate genes in psychiatric disorders

Sex steroids readily pass the blood-brain barrier, and receptors for them are abundant in brain areas important for the regulation of emotions, cognition and behaviour. Animal experiments have revealed both important early effects of these hormones on brain development and their ongoing influence on brain morphology and neurotransmission in the adult organism. The important effects of sex steroids on human behaviour are illustrated by, for example, the effect of reduced levels of these hormones on sexual drive and conditions such as premenstrual dysphoric disorder, perimenopausal dysphoria, postpartum depression, postpartum psychosis, dysphoria induced by oral contraceptives or hormonal replacement therapy and anabolic steroid-induced aggression. The fact that men and women (as groups) differ with respect to the prevalence of several psychiatric disorders, certain aspects of cognitive function and certain personality traits may possibly also reflect an influence of sex steroids on human behaviour. The heritability of most behavioural traits, including personality, cognitive abilities and susceptibility to psychiatric illness, is considerable, but as yet, only few genes of definite importance in this context have been identified. Given the important role of sex steroids for brain function, it is unfortunate that relatively few studies so far have addressed the possible influence of sex steroid-related genes on interindividual differences with respect to personality, cognition and susceptibility to psychiatric disorders. To facilitate further research in this area, this review provides information on several such genes and summarizes what is currently known with respect to their possible influence on brain function.

On the sulfation and methylation of catecholestrogens in human mammary epithelial cells and breast cancer cells

Prolonged exposure to high level of estrogen is a known risk factor for breast carcinogenesis. In cells, estrogens, in particular estrone (E1) and 17 beta-estradiol (E2), can be converted to catecholestrogens (CEs) which may be oxidized to form CE-semiquinones and CE-quinones that are capable of binding to DNA to induce mutations, followed by carcinogenesis. Whether the body is equipped with protective mechanisms against potentially harmful CEs, therefore, is an important issue. The present study was designed to examine the role of sulfation in the metabolism of CEs. MCF-7 breast cancer cells and MCF 10A human mammary epithelial cells were metabolically labeled with [35S]sulfate in the presence of individual CEs. Analysis of the labeling media showed the generation and release of exclusively [35S]sulfated 2-methoxy-E1 or [35S]sulfated 2- or 4-methoxy-E2 by cells labeled in the presence of 2-OH-E1 or 2- or 4-OH-E2. Whereas both [35S]sulfated 4-methoxy-E1 and [35S]sulfated 4-OH-E1 were detected in the labeling media of cells labeled in the presence of 4-OH-E1. These results indicated a concerted action of catechol-O-methyltransferase (COMT) and the cytosolic sulfotransferase (SULT) enzyme(s) in the metabolism of CEs. Enzymatic assays revealed that, five (SULT1A1, SULT1A2, SULT1A3, SULT1C4, and SULT1E1) of eleven known human SULTs tested could use CEs and methoxyestrogens (MEs) as substrates, with SULT1E1 displaying the strongest sulfating activity.

Divergent backward masking performance in schizophrenia and bipolar disorder: association with COMT

Schizophrenia has been reliably associated with impairments in backward masking performance, while bipolar disorder has less consistently been tied to such a deficit. To examine the genetic determinants of visual perception abnormalities in schizophrenia and bipolar disorder, this study evaluated the diagnostic specificity of backward masking performance deficits and whether masking deficits were associated with catechol-O-methyl transferase (COMT) genotype. A location-based backward masking task, which equated participants on the perceptual intensity of stimuli, was completed by 41 schizophrenia outpatients, 28 bipolar outpatients, and 43 nonpsychiatric controls. COMT genotype data were available for 39 schizophrenia outpatients, 28 bipolar outpatients, and 20 nonpsychiatric controls. Schizophrenia patients demonstrated impaired backward masking performance compared to controls and bipolar patients. A group by COMT genotype interaction was detected with schizophrenia Met homozygotes performing more poorly than control and bipolar Met homozygotes, and worse than Val homozygote and heterozygote schizophrenia patients. This study provides novel evidence for differential effects of the COMT gene on neural systems underlying visual perception in schizophrenia and bipolar disorder. The COMT Met allele may be associated with deficits in schizophrenia that are unrelated to neural systems supporting sustained attention or working memory.

The Val158Met polymorphism of the catechol-O-methyltransferase gene is not associated with the risk of sporadic or latent prostate cancer in Japanese men

AIM

Since catechol estrogens possess carcinogenetic potential, their detoxification may lead to reduced risk of carcinogenesis. Catechol-O-methyltransferase (COMT) catalyzes the O-methylation of catechol estrogens. The enzymatic activity of COMT has been shown to be governed by a functional single-nucleotide polymorphism represented by a G-to-A transition at codon 158, that results in a valine to methionine substitution; this variant form is associated with an up to 4-fold decrease in enzymatic activity. We attempted to investigate whether the Val158Met polymorphism of COMT was associated with the risk of prostate cancer.

METHODS

We analysed genomic DNA samples from 324 sporadic prostate cancer patients; 342 controls who had died from causes unrelated to cancer; and 95 Japanese men who were diagnosed as latent prostate cancer by autopsy. The genotyping method we used was a TaqMan assay.

RESULTS

Age adjusted odds ratios for sporadic prostate cancer susceptibility were 1.047 (95% CI: 0.630-1.741) for the G/A genotype and 0.858 (95% CI: 0.407-1.804) for the A/A genotype, as compared with those for the G/G genotype. There was no significant association between this polymorphism and latent prostate cancer susceptibility either.

CONCLUSIONS

Our results suggested that the Val158Met polymorphism of COMT was not associated with the risk of sporadic or latent prostate cancer in Japanese men.

Genetic and epigenetic biomarkers in cancer : improving diagnosis, risk assessment, and disease stratification

Gene expression patterns change during the initiation, progression, and development of cancer, as a result of both genetic and epigenetic mechanisms. Genetic changes arise due to irreversible changes in the nucleotide sequence, whereas epigenetic changes occur due to changes in chromatin conformation, histone acetylation, and methylation of the CpG islands located primarily in the promoter region of a gene. Both genetic and epigenetic markers can potentially be utilized to identify different stages of tumor development. Several such markers exhibit high sensitivity and specificity for different tumor types and can be assayed in biofluids and other specimens collected by noninvasive technologies. In spite of the availability of large numbers of diagnostic markers, only a few have been clinically validated so far. The current status and the challenges in the field of genetic and epigenetic markers in cancer diagnosis, risk assessment, and disease stratification are discussed.

Catechol-O-methyltransferase haplotypes and breast cancer among women on Long Island, New York

The gene encoding catechol-O-methyltransferase (COMT), critical to the inactivation of reactive catechol estrogens, has several single nucleotide polymorphisms (SNPs) that influence enzyme activity. A 3-SNP haplotype (IVS1+255 C>T; Ex4-12 G>A; 3'UTR-521 A>G), which has been shown to reduce COMT expression in the human brain, has been identified. To evaluate the influence of genetic variation of COMT on breast cancer risk, these 3-SNPs were genotyped in 1052 cases and 1098 controls. We estimated the associations between breast cancer and individual SNPs, as well as, multilocus haplotypes. We also examined surrogates of hormone exposure as potential modifiers of the putatively functional Ex4-12 SNP-breast cancer association. Odds ratios (OR) and 95% confidence intervals (CI) were based on age-adjusted unconditional logistic regression models. We found no association between the individual SNPs alone and breast cancer. When examining the association between breast cancer and the 3-SNP haplotypes, we observed a 19% increase in risk associated with each copy of the TGG haplotype (OR=1.19, 95% CI 0.96-1.49), relative to the common TAA haplotype, which was statistically significant when assuming a dominant model (OR=1.32, 95% CI 1.05-1.67, p-value=0.02). In this report of COMT haplotypes and breast cancer, we found some evidence that additional genetic variability beyond the Ex4-12 G>A SNP contributes to risk of breast cancer among a small subgroup of women; however, these results need to be replicated in additional studies.

Multilocus Genotypes Spanning Estrogen Metabolism Associated with Breast Cancer and Fibroadenoma

We investigated inherited polymorphic variation in genes spanning estrogen metabolism (10 SNPs [single nucleotide polymorphism]) to distinguish multilocus genotypes associated with breast cancer (n = 393), benign breast lesions (n = 154), and low risk (n = 1936). Three latent classification GoM extreme type groups represented the data: (a) fibroadenoma, and infrequent SRD5A2 and VDR alleles; (b) postmenopausal breast cancer, and infrequent CYP1A1-1 and CYP1A1-2 alleles (both over-represented infrequent alleles for CYP17, CYP19-3, and COMT); and (c) women at intrinsically low risk. Carriage of the respective multilocus genotypes increased risk 25-fold. We conclude that GoM latent classification may be useful to identify genetic risk sets and estimate risk for individuals.

Departure from multiplicative interaction for catechol-O-methyltransferase genotype and active/passive exposure to tobacco smoke among women with breast cancer

BACKGROUND

Women with homozygous polymorphic alleles of catechol-O-methyltransferase (COMT-LL) metabolize 2-hydroxylated estradiol, a suspected anticarcinogenic metabolite of estrogen, at a four-fold lower rate than women with no polymorphic alleles (COMT-HH) or heterozygous women (COMT-HL). We hypothesized that COMT-LL women exposed actively or passively to tobacco smoke would have higher exposure to 2-hydroxylated estradiol than never-active/never passive exposed women, and should therefore have a lower risk of breast cancer than women exposed to tobacco smoke or with higher COMT activity.

METHODS

We used a case-only design to evaluate departure from multiplicative interaction between COMT genotype and smoking status. We identified 502 cases of invasive incident breast cancer and characterized COMT genotype. Information on tobacco use and other potential breast cancer risk factors were obtained by structured interviews.

RESULTS

We observed moderate departure from multiplicative interaction for COMT-HL genotype and history of ever-active smoking (adjusted odds ratio [aOR] = 1.6, 95% confidence interval [CI]: 0.7, 3.8) and more pronounced departure for women who smoked 40 or more years (aOR = 2.3, 95% CI: 0.8, 7.0). We observed considerable departure from multiplicative interaction for COMT-HL genotype and history of ever-passive smoking (aOR = 2.0, 95% CI: 0.8, 5.2) or for having lived with a smoker after age 20 (aOR = 2.8, 95% CI: 0.8, 10).

CONCLUSION

With greater control over potential misclassification errors and a large case-only population, we found evidence to support an interaction between COMT genotype and tobacco smoke exposure in breast cancer etiology.

Genetic determination of susceptibility to estrogen-induced mammary cancer in the ACI rat: mapping of Emca1 and Emca2 to chromosomes 5 and 18

Hormonal, genetic, and environmental factors play major roles in the complex etiology of breast cancer. When treated continuously with 17beta-estradiol (E2), the ACI rat exhibits a genetically conferred propensity to develop mammary cancer. The susceptibility of the ACI rat to E2-induced mammary cancer appears to segregate as an incompletely dominant trait in crosses to the resistant Copenhagen (COP) strain. In both (ACI x COP)F(2) and (COP x ACI)F(2) populations, we find strong evidence for a major genetic determinant of susceptibility to E2-induced mammary cancer on distal rat chromosome 5. Our data are most consistent with a model in which the ACI allele of this locus, termed Emca1 (estrogen-induced mammary cancer 1), acts in an incompletely dominant manner to increase both tumor incidence and tumor multiplicity as well as to reduce tumor latency in these populations. We also find evidence suggestive of a second locus, Emca2, on chromosome 18 in the (ACI x COP)F(2) population. The ACI allele of Emca2 acts in a dominant manner to increase incidence and decrease latency. Together, Emca1 and Emca2 act independently to modify susceptibility to E2-induced mammary cancer.

Cytochrome P450 1B1 and catechol-O-methyltransferase genetic polymorphisms and breast cancer risk in Chinese women: results from the shanghai breast cancer study and a meta-analysis

Cytochrome P450 1B1 (CYP1B1) and catechol-O-methyltransferase (COMT) are important estrogen-metabolizing enzymes and, thus, genetic polymorphisms of these enzymes may affect breast cancer risk. A population-based case-control study was conducted to assess the association of breast cancer risk with CYP1B1 and COMT polymorphisms. A meta-analysis was done to summarize the findings from this and previous studies. Included in this study were 1,135 incident breast cancer cases diagnosed from August 1996 through March 1998 among female residents of Shanghai and 1,235 randomly selected, age frequency-matched controls from the same general population. The common alleles of the CYP1B1 gene were Arg (79.97%) in codon 48, Ala (80.53%) in codon 119, and Leu (86.57%) in codon 432. The Val allele accounted for 72.46% of the total alleles identified in codon 108/158 of the COMT gene. No overall associations of breast cancer risk were found with any of the single nucleotide polymorphisms described above. This finding was supported by a meta-analysis of all previous published studies. No gene-gene interactions were observed between CYP1B1 and COMT genotypes. The associations of breast cancer risk with factors related to endogenous estrogen exposure, such as years of menstruation and body mass index, were not significantly modified by the CYP1B1 and COMT genotypes. We observed, however, that women who carried one copy of the variant allele in CYP1B1 codons 48 or 119 were less likely to have estrogen receptor-positive breast cancer than those who carried two copies of the corresponding wild-type alleles. The results from this study were consistent with those from most previous studies, indicating no major associations of breast cancer risk with CYP1B1 and COMT polymorphisms.

No association of estrogen receptor α and cytochrome P450c17α polymorphisms with age at menopause in a Dutch cohort

BACKGROUND

Age at menopause is under strong genetic control. So far, genetic variations of only one gene, the PvuII polymorphism of the estrogen receptor alpha (ERalpha) gene, have been shown to be associated with age at onset of menopause. This study aims to investigate whether PvuII, XbaI and B-variant polymorphisms of the ERalpha gene, and the MspAI polymorphism of the cytochrome P450c17alpha (CYP17) gene are associated with age at menopause in a Dutch cohort.

METHODS

DNA was isolated from urine samples of 385 Caucasian women with natural menopause and the genotypes of the four polymorphisms were determined. A questionnaire was used for background characteristics. The genotypes of PvuII, XbaI, MspAI were obtained by PCR restriction fragment length polymorphism analysis. The B-variant was determined with an allele-specific oligonucleotide hybridization method. Two-sided t-tests were performed to assess the association between the four polymorphisms and menopausal age. The PvuII and XbaI polymorphisms were analysed separately as well as in a combined score.

RESULTS

The results show that none of the polymorphisms independently, nor the combined genotypes for PvuII and XbaI, were associated with age at natural menopause.

CONCLUSION

No evidence was found for a relationship between common variants of the ERalpha gene and the CYP17 gene with age at natural menopause.

Catechol-O-methyltransferase Val 108/158 Met polymorphism in premenopausal breast cancer patients

There is compelling evidence to suggest that catecholestrogens may play a role in the development of breast cancer. Particularly, inactivation of catecholestrogens may prevent the genesis and arrest the development of breast cancer. Catechol-O-methyltransferase (COMT) is polymorphic and responsible for the detoxification of catecholestrogens. In the present study, we examined what role COMT gene polymorphisms may play in the development of breast cancer in a case-control study of 130 sporadic unrelated premenopausal Turkish breast cancer patients with 233 unrelated healthy controls. The frequency of COMT-L allele was more significantly represented in the breast cancer cases (48.08%) than in the controls (38.20%). The genotype frequencies of COMT-HH, HL and LL were 25.4, 53.1 and 21.5% in the breast cancer subjects and 26.6, 62.7 and 10.7% in the controls respectively. In conclusion, the COMT-L allele and COMT-LL genotype are genetic risk factors for sporadic breast cancer in premenopausal Turkish women.

A family-based genetic association study of variants in estrogen-metabolism genes COMT and CYP1B1 and breast cancer risk

In this paper, we report findings from a family-based association study examining the association between polymorphisms in two key estrogen-metabolism genes CYP1B1 (codon 432 G --> C and codon 453 A --> G variants) and COMT (codon 158 G --> A variant) and female breast cancer. We conducted the study among 280 nuclear families containing one or more daughters with breast cancer with a total of 1124 family members (702 with available constitutional DNA and questionnaire data and 421 without). These nuclear families were selected from breast cancer families participating in the Metropolitan New York Registry (MNYR) - one of the six centers of NCI's Breast Cooperative Family Registry. We used likelihood-based statistical methods to examine the allelic associations. We found none of the variant alleles of the CYP1B1 and COMT genes to be associated with breast cancer in these families. This was consistent with results from matched case-control analyses using all available sib-ships in these families. However, we found that parental carrier status of the CYP1B1 codon 453 variant G allele and the COMT codon 158 variant A allele was associated with breast cancer risk in daughters (independent of the daughters' own genotype). In conclusion, findings from this family-based study indicate that a woman's own CYP1B1 or COMT genotypes are not associated with her breast cancer risk. Although the study found that parental carrier status of certain CYP1B1 or COMT genotypes might be associated with daughter's breast cancer risk, the biological basis as well as independent confirmation of this finding need to be investigated in future larger family-based studies before making meaningful inferences.

An evolutionary perspective on single-nucleotide polymorphism screening in molecular cancer epidemiology

Given that there are millions of single-nucleotide polymorphisms (SNPs) in the entire human genome, a major difficulty faced by scientists in planning costly population-based genotyping is to choose target SNPs that are most likely to affect phenotypic functions and ultimately contribute to disease development. Although it is widely accepted that sequences with important functionality tend to be less variable across species because of selective pressure, to what extent evolutionary conservation is mirrored by epidemiological outcome has never been demonstrated. In this study, we surveyed odds ratios detected for 46 SNPs in 39 different cancer-related genes from 166 molecular epidemiological studies. The conservation levels of amino acid that these SNPs affected were calculated as a tolerance index by comparing sequences from different species. Our results provide evidence of a significant relationship between the detected odds ratios associated with cancer risk and the conservation levels of the SNP-affected amino acids (P = 0.002; R(2) = 0.06). Tolerance indices were further calculated for 355 nonsynonymous SNPs identified in 90 human DNA repair genes, of which 103 caused amino acid changes in very conserved positions. Our findings support the concept that SNPs altering the conserved amino acids are more likely to be associated with cancer susceptibility. Using such a molecular evolutionary approach may hold great promise for prioritizing SNPs to be genotyped in future molecular epidemiological studies.

Estrogen-metabolizing gene polymorphisms in the assessment of breast carcinoma risk and fibroadenoma risk in Caucasian women

BACKGROUND

Genes encoding enzymes involved in estrogen metabolism are held to be candidate genes for associations with breast disease. In these candidate genes, no critical combination of single-nucleotide polymorphisms (SNPs) for assessing breast carcinoma risk has been reported to date.

METHODS

In a large case-control study, the authors investigated 10 estrogen-metabolizing SNPs in 396 patients with breast carcinoma, 154 patients with fibroadenoma, and 1936 healthy control patients without breast carcinoma in their personal history. The following 10 SNPs were analyzed using sequencing-on-chip technology via a solid-phase polymerase chain reaction assay performed on oligonucleotide microarrays: catechol-O-methyltransferase Val158Met G-->A, 17-beta-hydroxysteroid dehydrogenase type 1 vIV A-->C, cytochrome P-450 (CYP) family 17 A2 allele T-->C, CYP1A1-1 MspI restriction fragment length polymorphism (RFLP) T-->C, CYP1A1-2 Ile462Val A-->G, CYP19-1 Trp39Arg T-->C, CYP19-2 Arg264Cys C-->T, CYP19-3 Cys1558Thr C-->T, steroid-5-alpha reductase type 2 Val89Leu G-->C, and vitamin D receptor BsmI RFLP. A total of 21,350 genotypes were evaluated. Associations and two-way interaction models were calculated using stepwise logistic regression.

RESULTS

In a multiple model, CYP1A1-1 (P = 0.004) and CYP1A1-2 (P = 0.03) were found to be associated with significantly decreased and increased risks of breast carcinoma, respectively. When two-way interactions involving investigated SNPs were ascertained, no significant interactions among polymorphisms were noted. Comparison of patients with fibroadenoma with control patients revealed significantly increased and decreased risks of fibroadenoma when the mutant alleles of CYP17 (P = 0.02) and CYP1A1-1 (P = 0.04), respectively, were present.

CONCLUSIONS

The authors obtained the first SNP data indicating that CYP17 and CYP1A1-1 play a role in the pathogenesis of fibroadenoma. Although the authors were not able to develop interaction models involving SNPs, they did provide evidence that CYP1A1 is a low-penetrance susceptibility gene with respect to breast carcinoma in a large series of Caucasian women.

Polymorphisms of estrogen synthesizing and metabolizing genes and breast cancer risk in Japanese women

Recent success of chemoprevention with tamoxifen has opened a new era wherein prevention of breast cancer is much more emphasized than treatment of established breast cancer. Since tamoxifen has been shown to reduce the risk of estrogen receptor (ER)-positive, but not ER-negative, breast cancer in the chemoprevention trial (P-1), it seems to be important to develop risk factors for ER-positive breast cancer in order to select the candidates for chemoprevention more appropriately. Estrogens, the major risk factors for breast cancer, are speculated to affect breast cancer risk through ER, thus, genetic polymorphisms of the genes involved in the estrogens biosynthesis and metabolism are expected as risk factors for ER-positive breast cancer. Significance of polymorphisms of the genes involved in estrogens biosynthesis (CYP17, CYP19) and metabolism (CYP1A1, CYP1B1, COMT) in modulating the susceptibility to breast cancer is reviewed. The ethnic difference of the variant allele frequencies between Caucasian women and Asian women is also discussed.

Molecular epidemiology of sporadic breast cancer. The role of polymorphic genes involved in oestrogen biosynthesis and metabolism

The major known risk factors for female breast cancer are associated with prolonged exposure to increased levels of oestrogen. The predominant theory relates to effects of oestrogen on cell growth. Enhanced cell proliferation, induced either by endogenous or exogenous oestrogens, increases the number of cell divisions and thereby the possibility for mutation. However, current evidence also supports a role for oxidative metabolites, in particular catechol oestrogens, in the initiation of breast cancer. As observed in drug and chemical metabolism, there is considerable interindividual variability (polymorphism) in the conjugation pathways of both oestrogen and catechol oestrogens. These person-to-person differences, which are attributed to polymorphisms in the genes encoding for the respective enzymes, might define subpopulations of women with higher lifetime exposure to hormone-dependent growth promotion, or to cellular damage from particular oestrogens and/or oestrogen metabolites. Such variation could explain a portion of the cancer susceptibility associated with reproductive effects and hormone exposure. In this paper the potential role of polymorphic genes encoding for enzymes involved in oestrogen biosynthesis (CYP17, CYP19, and 17beta-HSD) and conversion of the oestrogen metabolites and their by-products (COMT, CYP1A1, CYP1B1, GSTM1, GSTM3, GSTP1, GSTT1 and MnSOD) in modulating individual susceptibility to breast cancer are reviewed. Although some of these low-penetrance genes appeared as good candidates for risk factors in the etiology of sporadic breast cancer, better designed and considerably larger studies than the majority of the studies conducted so far are evidently needed before any firm conclusions can be drawn.

Genotoxic metabolites of estradiol in breast: potential mechanism of estradiol induced carcinogenesis

Long term exposure to estradiol increases the risk of breast cancer in a variety of animal species, as well as in women. The mechanisms responsible for this effect have not been firmly established. The prevailing theory proposes that estrogens increase the rate of cell proliferation by stimulating estrogen receptor-mediated transcription and thereby the number of errors occurring during DNA replication. An alternative hypothesis proposes that estradiol can be metabolized to quinone derivatives which can react with DNA and then remove bases from DNA through a process called depurination. Error prone DNA repair then results in point mutations. We postulate that these two processes, increased cell proliferation and genotoxic metabolite formation, act in an additive or synergistic fashion to induce cancer. If correct, aromatase inhibitors would block both processes whereas anti-estrogens would only inhibit receptor-mediated effects. Accordingly, aromatase inhibitors would be more effective in preventing breast cancer than use of anti-estrogens. Our studies initially demonstrated that catechol estrogen (CE) quinone metabolites are formed in MCF-7 human breast cancer cells in culture. Measurement of estrogen metabolites and conjugates involved utilization of an HPLC separation coupled with an electrochemical detector. We then utilized an animal model that allows dissociation of estrogen receptor-mediated function from that of the effects of estradiol metabolites. Wnt-1 transgenic mice harboring a knock-out of ERalpha provides a means of examining the effect of estrogen deprivation in the absence of the ER in animals with a high incidence of breast tumors. ERbeta was shown to be absent in the breast tissue of these animals by RNase protection assay. In the breast tissue of these estrogen receptor alpha knock-out (ERKO)/Wnt-1 transgenic mice, we demonstrated formation of genotoxic estradiol metabolites. The ERKO/Wnt-1 breast extracts contained picomole amounts of the 4-catechol estrogens, but not their methoxy conjugates nor the 2-CE or their methoxy conjugates. The 4-CE conjugates with glutathione or its hydrolytic products (cysteine and N-acetylcysteine) were detected in picomole amounts in both tumors and hyperplastic mammary tissue, demonstrating the formation of CE-3,4-quinones. These results are consistent with the hypothesis that mammary tumor development is primarily initiated by metabolism of estrogens to 4-CE and, then, to CE-3,4-quinones, which may react with DNA to induce oncogenic mutations. The next set of experiments examined the incidence of tumors formed in Wnt-1 transgenic mice bearing wild type ERalpha (ER+/+), the heterozygous combination of genes (ER+/ER-) or ERalpha knock-out (ER-/-). To assess the effect of estrogens in the absence of ER, half of the animals were oophorectomized on day 15 and the other half were sham operated. Castration reduced the incidence of breast tumors in all animal groups and demonstrated the dependence of tumor formation upon estrogens. A trend toward reduction in tumor number (not statistically significant at this interim analysis) occurred in the absence of functional ER since the number of tumors was markedly reduced in ERKO animals which were castrated early in life. In aggregate, our results support the concept that metabolites of estradiol may act in concert with ER mediated mechanisms to induce breast cancer.

Catechol estrogen 4-hydroxyequilenin is a substrate and an inhibitor of catechol-O-methyltransferase

Redox and/or electrophilic metabolites formed during estrogen metabolism may play a role in estrogen carcinogenesis. 4-Hydroxyequilenin (4-OHEN) is the major phase I catechol metabolite of the equine estrogens equilenin and equilin, which are components of the most widely prescribed estrogen replacement formulation, Premarin. Previously, we have found that 4-OHEN rapidly autoxidized to an o-quinone in vitro and caused toxic effects such as the inactivation of human detoxification enzymes. 4-OHEN has also been shown to be a substrate for catechol-O-methyltransferase (COMT) in human breast cancer cells. In the present study, we demonstrated that 4-OHEN was not only a substrate of recombinant human soluble COMT in vitro with a K(m) of 2.4 microM and k(cat) of 6.0 min(-)(1) but it also inhibited its own methylation by COMT at higher concentrations in the presence of the reducing agent dithiothreitol. In addition, 4-OHEN was found to be an irreversible inhibitor of COMT-catalyzed methylation of the endogenous catechol estrogen 4-hydroxyestradiol with a K(i) of 26.0 microM and a k(2) of 1.62 x 10(-)(2) s(-)(1). 4-OHEN in vitro not only caused the formation of intermolecular disulfide bonds as demonstrated by gel electrophoresis, but electrospray ionization mass spectrometry and matrix-assisted laser desorption ionization time-of-flight mass spectrometry also showed that 4-OHEN alkylated multiple residues of COMT. Peptide mapping experiments further indicated that Cys33 in recombinant human soluble COMT was the residue most likely modified by 4-OHEN in vitro. These data suggest that inhibition of COMT methylation by 4-OHEN might reduce endogenous catechol estrogen clearance in vivo and further enhance toxicity.

[Pharmacogenomics in gynecology. Replies to the Zurich Discussion Panel]

Leider besteht für diesen Artikel keine Zusammenfassung. Als Einstieg stellen wir den Textanfang zur Verfügung. Mehr als ein Jahrzehnt dauert bereits die wissenschaftliche Auseinandersetzung zwischen deutschen und österreichischen Endokrinologen bzw. Biochemikern, ob eine individuelle Hormonersatztherapie (HRT) sinnvoll ist und wie sie konkret aussehen soll. Dieses Thema wird nicht nur durch rezente Untersuchungen [1] aktualisiert, die klar belegen, dass die behandelten Frauen zu einem hohen Prozentsatz mit ihrer HRT unzufrieden sind und sie – vor allem wegen hyperöstrogenämischen Symptomen – nach relativ kurzer Zeit wieder beenden, sondern auch durch die HERS [2] und die Studie der Nurses’ Health Initiative [3], die sich von ihrem Design durch eine völlig unreflektierte Hormonverordnung auszeichnen. Die dabei vor allem gleich am Beginn auftretenden kardiovaskulären Probleme deuten bereits auf eine genetische Risikodisposition hin, in die stereotyp hineinsubstituiert wurde.

[Remarks of the Zurich Discussion Panel on the gene test]

Leider besteht für diesen Artikel keine Zusammenfassung. Als Einstieg stellen wir den Textanfang zur Verfügung. Seit einiger Zeit wird ein Gentest angeboten, mit dem sich angeblich das individuelle Risiko für z.B. Herz-/Kreislauferkrankungen, Thrombosen, Osteoporose, Mammakarzinom oder Schwangerschaftskomplikationen durch die Analyse von 18 genetischen Parametern bzw. deren Polymorphismen erkennen lässt. Anhand der Ergebnisse dieses Tests soll es dann möglich sein, für jede Frau die optimale Hormonsubstitution festzulegen und die individuellen Krankheitsrisiken durch geeignete Massnahmen zu minimieren. Nach der Veröffentlichung einer kurzen Stellungnahme zu diesem Gentest im Addendum der jüngsten Empfehlungen des Zürcher Gesprächskreises zur Hormonsubstitution in ‘Frauenarzt’ 2/2002 gingen verschiedene Kommentare ein. Der Zürcher Gesprächskreis sieht sich deshalb veranlasst, zum Thema Polymorphismen eine ausführliche Stellungnahme abzugeben.

Characterization of human soluble high and low activity catechol-O-methyltransferase catalyzed catechol estrogen methylation

The major detoxification pathway of the carcinogenic catechol estrogens is methylation by catechol- -methyltransferase (COMT). It has been hypothesized that the enzyme encoded by the low-activity allele (COMT(L) ) has a lower catalytic activity for catechol estrogen methylation than that encoded by the high activity allele (COMT(H) ). We expressed and purified human soluble (S)-COMT(H) and S-COMT(L) in and characterized the methylation of 2- and 4-hydroxyestradiol (2- and 4-OH-E2). There were no differences between the kinetic parameters for COMT(H) and COMT(L). The kinetic parameters for S-adenosylmethionine (SAM), the methyl donor in these reactions, also did not differ for COMT(H) and COMT(L). S-adenosylhomocysteine, the demethylated SAM metabolite, inhibited methylation of the catechol estrogens in a non-competitive manner similarly for COMT(H) and COMT(L). Each COMT substrate tested inhibited the methylation of other substrates in a mixed competitive and non-competitive fashion similarly for COMT(H) and COMT(L). Furthermore, in cytosolic fractions of COMT(HH)(MCF-10A and ZR-75-1) and COMT(LL)(MCF-7 and T47D) human breast epithelial cell lines, no differences were detected between the kinetic parameters of COMT with respect to 2- and 4-OH-E2 methylation; nor were COMT protein levels associated with the COMT genotype. These data suggest that the decreased COMT enzymatic activity that has been detected in human tissue in association with the COMT(L) allele is not reflected by differences in the affinity or capacity of COMT(H) and COMT(L) for catechol estrogen methylation. These results raise the question of what accounts for the difference in COMT activity associated with the COMT(HH) and COMT(LL) genotypes in human tissue.

Catecholestrogen sulfation: possible role in carcinogenesis

A growing body of evidence supports the hypothesis that estrogens can be carcinogens as a result of their conversion to genotoxins after biotransformation to form the catecholestrogens (CEs) 2-hydroxyestrone (2-OHE1), 2-hydroxyestradiol (2-OHE2), 4-hydroxyestrone (4-OHE1) and 4-hydroxyestradiol (4-OHE2). CEs can then undergo further metabolism to form quinones that interact with DNA to form either stable or depurinating adducts. These events could potentially be interrupted by the sulfate conjugation of both the parent estrogens and/or the CEs. We set out to determine whether CEs can serve as substrates for sulfate conjugation, and-if so-which of the growing family of human sulfotransferase (SULT) isoforms are capable of catalyzing those reactions. We determined apparent K(m) values for 10 recombinant human SULT isoforms, as well as the three most common allozymes for SULT1A1 and SULT1A2, with 2-OHE1, 2-OHE2, 4-OHE1, and 4-OHE2, and with the endogenous estrogens, estrone (E1) and 17beta-estradiol (E2), as substrates. With the exception of SULT1B1, SULT1C1, and SULT4A1, all of the human SULTs studied catalyzed the sulfate conjugation of CEs. SULT1E1 had the lowest apparent K(m) values, 0.31, 0.18, 0.27, and 0.22 microM for 4-OHE1, 4-OHE2, 2-OHE1, and 2-OHE2, respectively. These results demonstrate that SULTs can catalyze the sulfate conjugation of CEs, and they raise the possibility that individual variation in this pathway for estrogen and CE metabolism as a result of common genetic polymorphisms could represent a risk factor for estrogen-dependent carcinogenesis.