Progression of human breast cancers to the metastatic state is linked to genotypes of catechol-O-methyltransferase

Genetic Polymorphisms as Predictors of Survival in Breast Cancer: Future Lessons in Historical Data

Introduction

Breast cancer is the most common cancer among women worldwide and one of the main causes of death in the female sex. Genetic polymorphisms in the mu-opioid receptor (OPRM1) and catechol-o-methyltransferase (COMT) genes have been shown to increase breast cancer risk. Variants in these genes may carry a prognostic impact in breast cancer. Long follow-up intervals are critical to adequately analyze prognosis in diseases with prolonged survival times and late relapses.

Objective

To analyze the impact of genetic polymorphisms on the survival of a cohort of breast cancer patients with very long follow-up.

Methods

This was a retrospective study of patients treated at Portuguese Oncology Institute of Porto (IPO Porto), a Portuguese comprehensive cancer center, with invasive carcinoma of the breast with very long follow-up, with analysis of genetic polymorphisms OPMR1 rs1799971 (AA vs. G allele) and COMT rs4680 (CC vs T allele) on biological samples. Statistical analysis of survival was performed using the Kaplan-Meier method, log-rank test, and Cox regression method.

Results

A total of 143 patients with invasive breast cancer were included, with a median follow-up of 21.5 years. There was a statistically significant difference in overall survival (OS) at 30 years according to the OPMR1 polymorphism, with lower survival in patients with the AA genotype (p<0.05). The difference in OS according to the COMT polymorphism was also statistically significant, with worse survival in patients with genotype T allele (p<0.05). The genetic variants were not associated with patient age, stage at diagnosis, or tumor grade.

Discussion

The genetic polymorphisms of OPRM1 and COMT affected the overall survival of breast cancer patients, in concordance with previous research. Further investigation is needed in order to clarify the prognostic impact of these genetic alterations on breast cancer.

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.

No association between germline variation in catechol-O-methyltransferase and colorectal cancer survival in postmenopausal women

OBJECTIVE

Sex steroid hormones play a role in colorectal cancer (CRC) development, but little is known about their influence on tumor progression and metastasis. Because catechol-O-methyltransferase (COMT; 22q11.21) activity is an important component of estrogen-mediated carcinogenesis, we hypothesized that germline variation in COMT may be associated with CRC survival.

METHODS

We identified 10 single nucleotide polymorphisms that tagged variation across two isoforms of COMT in 2,458 women with CRC from the Nurses' Health Study, Postmenopausal Hormones Supplementary Study to the Colon Cancer Family Registry, VITamins And Lifestyle Study, and Women's Health Initiative. All four studies participated in the Genetics and Epidemiology of Colorectal Cancer Consortium.

RESULTS

During a median follow-up of 7 years across all studies, there were 799 deaths, including 566 deaths from CRC. Based on multiple comparisons, no associations between single nucleotide polymorphisms and CRC-specific or overall survival reached statistical significance, including the well-characterized Val108/158Met polymorphism (rs4680; CRC-specific survival: hazard ratio per minor allele, 1.04; 95% CI, 0.92-1.17; overall survival: hazard ratio per minor allele, 1.01; 95% CI, 0.90-1.14).

CONCLUSIONS

In this large study of women with CRC, we find no evidence that common inherited variation in COMT is associated with survival time after diagnosis.

Chemical reaction of soybean flavonoids with DNA: a computational study using the implicit solvent model

Genistein, daidzein, glycitein and quercetin are flavonoids present in soybean and other vegetables in high amounts. These flavonoids can be metabolically converted to more active forms, which may react with guanine in the DNA to form complexes and can lead to DNA depurination. We assumed two ultimate carcinogen forms of each of these flavonoids, diol epoxide form and diketone form. Density functional theory (DFT) and Hartree-Fock (HF) methods were used to study the reaction thermodynamics between active forms of flavonoids and DNA guanine. Solvent reaction field method of Tomasi and co-workers and the Langevin dipoles method of Florian and Warshel were used to calculate the hydration free energies. Activation free energy for each reaction was estimated using the linear free energy relation. Our calculations show that diol epoxide forms of flavonoids are more reactive than the corresponding diketone forms and are hence more likely flavonoid ultimate carcinogens. Genistein, daidzein and glycitein show comparable reactivity while quercetin is less reactive toward DNA.

Inhibition of catechol-Omicron-methyltransferase activity in human breast cancer cells enhances the biological effect of the green tea polyphenol (-)-EGCG

Tea is one of the most popular beverages in the world and has been studied extensively as a health-promoting beverage that may act to prevent a number of chronic diseases and cancers. (-)-Epigallocatechin gallate [(-)-EGCG], a major component in green tea, is unstable under physiological conditions and methylation of (-)-EGCG by catechol-Omicron-methyltransferase (COMT) is a modification that reduces the biological activity of (-)-EGCG. In the current study, we hypothesized that suppression of COMT activity in human breast cancer cells could increase the proteasome-inhibitory potency of (-)-EGCG and therefore enhance its tumor cell growth-inhibitory activity. We first determined the COMT genotype and basal levels of COMT activity in various human breast cancer cell lines. Furthermore, when breast cancer MDA-MB-231 cells containing high COMT activity were tested, the diminished COMT activity apparently increased the effectiveness of (-)-EGCG via augmented proteasome inhibition and apoptosis induction. This study supplements the previous findings that methylated (-)-EGCG is less bioactive and supports the notion that COMT inhibition may increase the anti-cancer properties of tea polyphenols and the combination may serve as a novel approach or supplemental treatment for breast cancer chemotherapy.

Epistatic and functional interactions of catechol-o-methyltransferase (COMT) and AKT1 on neuregulin1-ErbB signaling in cell models

Background

Neuregulin1 (NRG1)-ErbB signaling has been implicated in the pathogenesis of cancer and schizophrenia. We have previously reported that NRG1-stimulated migration of B lymphoblasts is PI3K-AKT1dependent and impaired in patients with schizophrenia and significantly linked to the catechol-o-methyltransferase (COMT) Val108/158Met functional polymorphism.

Methodology/Principal Findings

We have now examined AKT1 activation in NRG1-stimulated B lymphoblasts and other cell models and explored a functional relationship between COMT and AKT1. NRG1-induced AKT1 phosphorylation was significantly diminished in Val carriers compared to Met carriers in both normal subjects and in patients. Further, there was a significant epistatic interaction between a putatively functional coding SNP in AKT1 (rs1130233) and COMT Val108/158Met genotype on AKT1 phosphorylation. NRG1 induced translocation of AKT1 to the plasma membrane also was impaired in Val carriers, while PIP₃ levels were not decreased. Interestingly, the level of COMT enzyme activity was inversely correlated with the cells' ability to synthesize phosphatidylserine (PS), a factor that attracts the pleckstrin homology domain (PHD) of AKT1 to the cell membrane. Transfection of SH-SY5Y cells with a COMT Val construct increased COMT activity and significantly decreased PS levels as well as NRG1-induced AKT1 phosphorylation and migration. Administration of S-adenosylmethionine (SAM) rescued all of these deficits. These data suggest that AKT1 function is influenced by COMT enzyme activity through competition with PS synthesis for SAM, which in turn dictates AKT1-dependent cellular responses to NRG1-mediated signaling.

Conclusion/Significance

Our findings implicate genetic and functional interactions between COMT and AKT1 and may provide novel insights into pathogenesis of schizophrenia and other ErbB-associated human diseases such as cancer.

Common germline polymorphisms in COMT, CYP19A1, ESR1, PGR, SULT1E1 and STS and survival after a diagnosis of breast cancer

Although preliminary evidence suggests that germline variation in genes involved in steroid hormone metabolism may alter breast cancer prognosis, this has not been systematically evaluated. We examined associations between germline polymorphisms in 6 genes involved in the steroid hormone metabolism and signaling pathway (COMT, CYP19A1, ESR1, PGR, SULT1E1, STS) and survival among women with breast cancer participating in SEARCH, a population-based case-control study. Blood samples from up to 4,470 women were genotyped for 4 possible functional SNPs in CYP19A1 and 106 SNPs tagging the common variation in the remainder of the genes. The genotypes of each polymorphism were tested for association with survival after breast cancer diagnosis using Cox regression analysis. Significant evidence of an association was observed for a COMT polymorphism (rs4818 p = 0.016) under the codominant model. This SNP appeared to fit a dominant model better (HR = 0.80 95% CI: 0.69-0.95, p = 0.009); however, the result was only marginally significant after permutation analysis adjustment for multiple hypothesis tests (p = 0.047). To further evaluate this finding, somatic expression microarray data from 8 publicly available datasets were used to test the association between survival and tumor COMT gene expression; no statistically significant associations were observed. A correlated SNP in COMT, rs4860, has recently been associated with breast cancer prognosis in Chinese women in a dominant model. These results suggest that COMT rs4818, or a variant it tags, is associated with breast cancer prognosis. Further study of COMT and its putative association with breast cancer prognosis is warranted.

Influence of Catechol-O-Methyltransferase (COMT) Genotypes on the Prognosis of Canine Mammary Tumors

Catechol-O-methyltransferase (COMT) is an important enzyme involved in inactivation of catechol estrogens, which are metabolites with carcinogenic properties. Some investigations in human breast cancer associate a genetic polymorphism in the COMT gene (COMT val158met) with an increased risk and poor clinical progression of the disease. In dogs, there are 2 recognized single nucleotide polymorphisms in the COMT gene (COMTG216A and COMTG482A); however, their influence on the outcome of mammary neoplasms has never been investigated. The purpose of this study is to investigate the influence of COMT in the clinical progression of canine mammary tumors, namely in recurrence, metastasis and survival by testing 2 SNPs (G216A and G482A), and 2 genotypes of the COMT gene. A case series was conducted analyzing genomic DNA samples by polymerase chain reaction-restriction fragment length polymorphism from 80 bitches with mammary tumors. Animals were submitted to an active follow-up study for a period of 24 months after surgery. We observed that bitches carrying both genetic variations simultaneously are more likely to develop recurrence of mammary lesions. Our results demonstrate a possible role for COMT genotypes in the outcome of mammary neoplasms in the dog. Identifying a genetic factor predictive of recurrence may be useful in selecting the most effective surgical approach for canine mammary neoplasms.

Do single nucleotide polymorphisms in xenobiotic metabolizing genes determine breast cancer susceptibility and treatment outcomes?

SNPs in CYP1A1, CYP2A1, CYP2B6, CYP2C, CYP2D6, CYP3A, GSTM1, GSTT1, GSTP1, SULT1A1, SULT1A2, UGT, and MTHFR are associated with breast cancer susceptibility; however, lack of such associations are also reported in some populations. The contradictory findings are explained on the basis of ethnic variation among populations and due to lack of proper sample size, detailed genotype-phenotype combinations and validation of gene expression studies at protein level. In this review, SNPs in these genes that have tremendous potential in identification of susceptible individuals, development of preventive strategies, treatment outcomes and their limitations are discussed.

Catechol-O-methyltransferase: effects of the val108met polymorphism on protein turnover in human cells

A single nucleotide polymorphism in the human COMT (catechol-O-methyltransferase) gene has been associated with increased risk for breast cancer and several CNS diseases and disorders. The G to A polymorphism causes a valine (val) to methionine (met) substitution at codon 108 soluble - (S)/158 membrane - (MB)-COMT, generating alleles encoding high and low-activity forms of the enzyme, COMT H and COMT L, respectively. Tissues and cells with a COMT LL genotype have decreased COMT activity compared to COMT HH cells. Previously, we reported that the decreased activity was due to decreased amounts of S-COMT L protein in human hepatocytes. In this study, we investigated the role of S-COMT protein synthesis and turnover as determinates of reduced COMT protein in COMT LL compared to COMT HH cells. No association between S-COMT protein synthesis and COMT genotype was detected. Using a pulse-chase protocol, the half-life of S-COMT H was determined to be 4.7 days, which was considerably longer than expected from the half-lives of other phase 2 enzyme proteins. The half-life of S-COMT L compared to S-COMT H protein was significantly shorter at 3.0 days, but the difference was affected by the medium used during the chase period. These results suggest that increased turnover may contribute to reduced COMT activity in cells and tissues from COMT LL individuals. Subtle differences appear to be able to affect the stability of the S-COMT L protein, and this may contribute to the differences observed in epidemiological studies on the association of this polymorphism with breast cancer risk.

Neuregulin-1 regulates cell adhesion via an ErbB2/phosphoinositide-3 kinase/Akt-dependent pathway: potential implications for schizophrenia and cancer

Background

Neuregulin-1 (NRG1) is a putative schizophrenia susceptibility gene involved extensively in central nervous system development as well as cancer invasion and metastasis. Using a B lymphoblast cell model, we previously demonstrated impairment in NRG1α-mediated migration in cells derived from patients with schizophrenia as well as effects of risk alleles in NRG1 and catechol-O-methyltransferase (COMT), a second gene implicated both in schizophrenia susceptibility and in cancer.

Methodology/Principal Findings

Here, we examine cell adhesion, an essential component process of cell motility, using an integrin-mediated cell adhesion assay based on an interaction between ICAM-1 and the CD11a/CD18 integrin heterodimer expressed on lymphoblasts. In our assay, NRG1α induces lymphoblasts to assume varying levels of adhesion characterized by time-dependent fluctuations in the firmness of attachment. The maximum range of variation in adhesion over sixty minutes correlates strongly with NRG1α-induced migration (r² = 0.61). NRG1α-induced adhesion variation is blocked by erbB2, PI3K, and Akt inhibitors, but not by PLC, ROCK, MLCK, or MEK inhibitors, implicating the erbB2/PI3K/Akt1 signaling pathway in NRG1-stimulated, integrin-mediated cell adhesion. In cell lines from 20 patients with schizophrenia and 20 normal controls, cells from patients show a significant deficiency in the range of NRG1α-induced adhesion (p = 0.0002). In contrast, the response of patient-derived cells to phorbol myristate acetate is unimpaired. The COMT Val108/158Met genotype demonstrates a strong trend towards predicting the range of the NRG1α-induced adhesion response with risk homozygotes having decreased variation in cell adhesion even in normal subjects (p = 0.063).

Conclusion/Significance

Our findings suggest that a mechanism of the NRG1 genetic association with schizophrenia may involve the molecular biology of cell adhesion.

Neuregulin1-induced cell migration is impaired in schizophrenia: association with neuregulin1 and catechol-o-methyltransferase gene polymorphisms

Neuregulin1 (NRG1), a candidate susceptibility gene for schizophrenia, plays a critical role in neuronal migration and central nervous system development. However, its relation to schizophrenia pathogenesis is unknown. Here we show that B lymphoblasts migrate to NRG1 through the ErbB-signaling system as observed in neuronal cells. We assessed NRG1-induced cell migration in B lymphoblasts from patients with schizophrenia and found that NRG1-induced migration is significantly decreased compared with control individuals in two independent cohorts. This impaired migration is related at least in part to reduced AKT phosphorylation in the patients. Moreover, the magnitude of NRG1-induced migration is associated with polymorphisms of the NRG1 and catechol-o-methyltransferase genes and with an epistatic interaction of these genes. This study demonstrates that the migratory response of schizophrenia-derived cells to NRG1 is impaired and is associated with genetic variations in more than one schizophrenia susceptibility gene, providing a novel insight into potential neurodevelopmental mechanisms of schizophrenia.

A multigenic study on breast cancer risk associated with genetic polymorphisms of ER Alpha, COMT and CYP19 gene in BRCA1/BRCA2 negative Shanghai women with early onset breast cancer or affected relatives

High penetrance genes such as BRCA1 or BRCA2 account for only a small proportion of familial breast cancer in Chinese population. Estrogen has been proposed to participate in the proliferation and carcinogenesis of breast cancer. To investigate the association between genetic polymorphisms in genes encoding estrogen metabolizing, estrogen biosynthesizing enzyme and estrogen receptor and the breast cancer risk in BRCA1/BRCA2 negative Shanghai women, we conducted a case-control study including 114 cases with early-onset breast cancer or affected relatives and 121 healthy controls. The genotypes of estrogen receptor alpha (ERalpha), aromatase (CYP19), and catechol-O-methyltransferase (COMT) genes were analyzed by direct DNA-sequencing. Compared with H/H genotype of COMT Val158Met, COMT Val158Met L/L genotype was associated with a nonsignificantly elevated risk of breast cancer (OR: 3.72; 95% CI: 0.99-13.96, P=0.051). There was no statistically significant difference in genotype frequency of the ERalpha PvuII, ERalpha XbaI and CYP19 Arg264Cys polymorphism between controls and cases. When stratified by menopausal status, COMT Val158Met L/L (OR: 11.94; 95% CI: 1.48-96.03, P=0.02) and ERalpha PvuII P/p genotypes (OR: 2.67; 95% CI: 1.01-7.05, P=0.048) were associated with a significantly elevated risk of breast cancer in premenopausal women, and there was a association between ERalpha XbaI x/x genotype and the nonsignificantly increased risk of breast cancer in premenopausal women (OR: 6.88; 95% CI: 0.80-59.15, P=0.079). The multigenic analysis showed maybe these high risk genotypes had combined effect on breast cancer risk. Our findings suggest that polymorphism of genes involving estrogen-metabolizing pathway, estrogen- biosynthesizing pathway and estrogen receptor pathway may play an important role in the etiology of BRCA1/2 negative breast cancer with hereditary predisposing factors.

Genetic polymorphisms in estrogen-metabolizing genes and breast cancer survival

BACKGROUND

Estrogen plays a central role in the development and progression of breast cancer. The estrogen's effects are at least partially regulated by estrogen-metabolizing enzymes. The objective of the study is to investigate associations of breast cancer survival with genetic polymorphisms in several genes involved in estrogen metabolism (CYP1A1, CYP1A2, CYP1B1, COMT, and AhR).

METHODS

A cohort of 1140 patients aged between 25 and 64 years at the time of diagnosis for primary breast cancer during 1996-1998 were included in the study. Patients were followed for cancer recurrence and mortality through July 2005.

RESULTS

Associations were observed at rs4680 (Met158Val) in the COMT gene and rs4646903 (CYP1A1*2A) in the CYP1A1 gene. The adjusted hazard ratio for the rs4680 AA genotype (low enzyme activity genotype) was 1.6 (95% confidence interval, 1.1-2.4) compared with the GG genotype for disease-free survival. Adjusted hazard ratios for the rs4646903 CC genotype were 1.6 (95% confidence interval, 1.2-2.2) for disease-free survival and 1.4 (95% confidence interval, 1.0-2.1) for overall survival compared with the TT genotype. No apparent association was found for any of the other six single nucleotide polymorphisms evaluated in the AhR, CYP1A1, CYP1A2, and CYP1B1 genes.

CONCLUSION

Results from this study suggest that rs4680 in the COMT gene and rs4646903 in the CYP1A1 gene may be genetic markers for breast cancer prognosis in Chinese women.

Catechol-O-methyltransferase gene polymorphisms in benign prostatic hyperplasia and sporadic prostate cancer

Various carcinogenic metabolites, including catechol estrogens, play a role in malignant transformation. An enzyme that is capable of neutralizing the genotoxic effects of these compounds is catechol-O-methyltransferase (COMT). A variant form of this enzyme has been shown to reduce its activity by up to 4-fold; thus, we hypothesize that single nucleotide polymorphisms of the COMT gene can be a risk factor for benign prostatic hyperplasia (BPH) and prostate cancer. To test this hypothesis, the genetic distribution of three different COMT polymorphisms at codon 62 (C-->T), codon 72 (G-->T), and codon 158 (G-->A) were analyzed in 131 normal healthy subjects, 134 BPH, and 178 sporadic prostate cancer samples from a Japanese population. Results of these experiments show that the variant genotype at codon 62 (P = 0.060) and codon 158 (P = 0.047) are risk factors for prostate cancer but not BPH when compared with normal controls. Odds ratio (OR) and 95% confidence interval (95% CI) for cancer were 3.24 and 1.38 to 7.61, respectively, for codon 62 T/T genotype when compared with wild type. At codon 158, the A/A variant for cancer had an OR of 3.00 with a 95% CI of 1.38 to 6.54 compared with wild type. Codons 62 and 158 were in linkage disequilibrium (LD), and when compared with the C-G haplotype, other types (C-A, T-G, T-A) were observed to be associated with prostate cancer (P = 0.040) but not BPH. Codon 72 on the other hand, was not in LD with either codon 62 or 158. The homozygous variant on codon 72 was rare in this Japanese population, and the heterozygous G/T at this codon was not associated with either prostate cancer or BPH. When evaluating the risk of COMT polymorphisms with stage or grade of cancer, no associations were observed for any of the genotypes with the exception of a tendency (P = 0.096) for the variant A allele on codon 158 to be correlated with higher stages (> or = T3) of cancer. This is the first report that shows the polymorphisms of COMT to be associated with sporadic prostatic carcinogenesis. These results are important in understanding the role of COMT polymorphisms in the pathogenesis of prostate cancer.

Multilocus analysis of SNP and metabolic data within a given pathway

BACKGROUND

Complex traits, which are under the influence of multiple and possibly interacting genes, have become a subject of new statistical methodological research. One of the greatest challenges facing human geneticists is the identification and characterization of susceptibility genes for common multifactorial diseases and their association to different quantitative phenotypic traits.

RESULTS

Two types of data from the same metabolic pathway were used in the analysis: categorical measurements of 18 SNPs; and quantitative measurements of plasma levels of several steroids and their precursors. Using the combinatorial partitioning method we tested various thresholds for each metabolic trait and each individual SNP locus. One SNP in CYP19, 3UTR, two SNPs in CYP1B1 (R48G and A119S) and one in CYP1A1 (T461N) were significantly differently distributed between the high and low level metabolic groups. The leave one out cross validation method showed that 6 SNPs in concert make 65% correct prediction of phenotype. Further we used pattern recognition, computing the p-value by Monte Carlo simulation to identify sets of SNPs and physiological characteristics such as age and weight that contribute to a given metabolic level. Since the SNPs detected by both methods reside either in the same gene (CYP1B1) or in 3 different genes in immediate vicinity on chromosome 15 (CYP19, CYP11 and CYP1A1) we investigated the possibility that they form intragenic and intergenic haplotypes, which may jointly account for a higher activity in the pathway. We identified such haplotypes associated with metabolic levels.

CONCLUSION

The methods reported here may enable to study multiple low-penetrance genetic factors that together determine various quantitative phenotypic traits. Our preliminary data suggest that several genes coding for proteins involved in a common pathway, that happen to be located on common chromosomal areas and may form intragenic haplotypes, together account for a higher activity of the whole pathway.

Estrogen-metabolizing gene polymorphisms and lipid levels in women with different hormonal status

Endogenous and exogenous sex steroid hormones have multiple effects on lipid and lipoprotein metabolism. It is also known that estrogen has antiatherogenic actions, therefore we considered examining whether there was any association between polymorphisms in estrogen-metabolizing genes and lipid levels in women. We investigated the association between variants in genes related to estrogen biosynthesis (CYP19-TTTA(n)) and estrogen catabolism (CYP1A1*2A, CYP1A1*2C, CYP1A2-Asn516Asn, CYP3A4*1B, and COMT-Val158Met) with serum lipid levels in a cross-sectional study with 472 Brazilian women of European descent. They were divided into three subgroups according to their hormonal status: premenopausal women (n=187), postmenopausal women exposed to hormonal replacement therapy (HRT) (n=118), and postmenopausal women unexposed to HRT (n=167). The postmenopausal women receiving HRT who were carriers of the CYP3A4*1B variant showed lower low-density lipoprotein cholesterol levels than wild-type homozygotes. Premenopausal women homozygous for the CYP1A1*2C allele had higher high-density lipoprotein cholesterol levels than heterozygotes. While the CYP1A1*2C variant probably has a higher catalytic activity, the functional implications of the CYP3A4 polymorphism are still uncertain. These data are the first attempt to associate estrogen metabolism genes to lipid levels in women.

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.

Catechol-O-methyltransferase low activity genotype (COMTLL) is associated with low levels of COMT protein in human hepatocytes

A single nucleotide polymorphism in the COMT (catechol-O-methyltransferase) gene that alters the amino acid sequence at codon 108 of S-COMT from val to met (val108met polymorphism) has been associated with a number of diseases and neuropsychiatric disorders. Several studies have shown that the met108 allele (COMTL) is associated with three to four-fold lower levels of COMT activity, compared to the val108 allele (COMTH), in extracts of human erythrocytes, liver and kidney tissue. We hypothesized that the differences in COMT activity observed in these studies were due to differing levels of COMT protein in cells and tissues with varying COMT genotypes. In order to address this, we obtained hepatocytes from 31 Caucasian female donors and determined their COMT genotype, COMT activity and COMT protein levels. We found that both cytosolic COMT activity and cytosolic COMT protein levels are lower in hepatocytes from COMTLL individuals, and that COMT activity levels correlate with COMT protein levels. Therefore, lower COMT activity seen in tissues and cells with the COMTLL genotype is likely due to lower COMT protein levels compared with tissues and cells from COMTHH individuals.

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.

Identification of alternatively spliced mRNA variants related to cancers by genome-wide ESTs alignment

Several databases have been published to predict alternative splicing of mRNAs by analysing the exon linkage relationship by alignment of expressed sequence tags (ESTs) to the genome sequence; however, little effort has been made to investigate the relationship between cancers and alternative splicing. We developed a program, Alternative Splicing Assembler (ASA), to look for splicing variants of human gene transcripts by genome-wide ESTs alignment. Using ASA, we constructed the biosino alternative splicing database (BASD), which predicted splicing variants for reference sequences from the reference sequence database (RefSeq) and presented them in both graph and text formats. EST clusters that differ from the reference sequences in at least one splicing site were counted as splicing variants. Of 4322 genes screened, 3490 (81%) were observed with at least one alternative splicing variants. To discover the variants associated with cancers, tissue sources of EST sequences were extracted from the UniLib database and ESTs from the same tissue type were counted. These were regarded as the indicators for gene expression level. Using Fisher's exact test, alternative splicing variants, of which EST counts were significantly different between cancer tissues and their counterpart normal tissues, were identified. It was predicted that 2149 variants, or 383 variants after Bonferroni correction, of 26 812 variants were likely tumor-associated. By reverse transcription-PCR, 11 of 13 novel alternative splicing variants and eight of nine variants' tissue specificity were confirmed in hepatocellular carcinoma and in lung cancer. The possible involvement of alternative splicing in cancer is discussed.

Proteomic phenotyping: metastatic and invasive breast cancer

The adriamycin resistant breast cancer cell line (MCF-7/ADR) is a subject of ongoing debate concerning its origin and or source. Previous studies in our laboratory showed that MCF-7/ADR has a unique cytosolic protein expression pattern when compared to that of the parental MCF-7 cell line and other drug resistant MCF-7 cell lines. Protein expression patterns obtained using two-dimensional gel electrophoresis and mass spectrometry indicated that this MCF-7/ADR cell line shares some similarities with the metastatic breast cancer cell lines MDA-MB. Further comparisons with available two-dimensional gel electrophoresis maps in the literature indicate that MCF-7/ADR has a protein expression signature even closer to of the ductal infiltrating breast carcinoma cell line 8701. These observations suggest that MCF-7/ADR cells might have originated in a selection of ductal infiltrating carcinoma cells, which were present among the original MCF-7 cell population. These ductal infiltrating carcinoma cells may possess an intrinsic adriamycin resistance phenotype.

Oxidative inhibition of human soluble catechol-O-methyltransferase

A common polymorphism in the human gene for catechol-O-methyltransferase results in replacement of Val-108 by Met in the soluble form of the protein (s-COMT) and has been linked to breast cancer and neuropsychiatric disorders. The 108M and 108V variants are reported to differ in their thermal stability, with 108M COMT losing catalytic activity more rapidly. Because human s-COMT contains seven cysteine residues and includes CXXC and CXXS motifs that are associated with thiol-disulfide redox reactions, we examined the effects of reducing and oxidizing conditions on the enzyme. In the absence of a reductant 108M s-COMT lost activity more rapidly than 108V, whereas in the presence of 4 mm dithiothreitol (DTT) we found no significant differences in the stability of the two variants at 37 degrees C. DTT also restored most of the activity that was lost upon incubation at 37 degrees C in the absence of DTT. Mass spectrometry showed that cysteines 188 and 191 formed an intramolecular disulfide bond when s-COMT was incubated with oxidized glutathione, whereas cysteines 69, 95, 157, and 173 formed protein-glutathione adducts. Replacing Cys-95 by serine protected 108M s-COMT against inactivation in the absence of a reductant; C33S and Cys-188 mutations had little effect, and C69S was destabilizing. The sequences surrounding the reactive cysteine residues of human s-COMT and other proteins that form glutathione adducts at identified sites all include Pro and/or Gly and most include a hydrogen-bonding residue, suggesting that glutathiolation at conserved sites plays a physiologically important role.

Chemical Reactivity as a Tool To Study Carcinogenicity: Reaction between Estradiol and Estrone 3,4-Quinones Ultimate Carcinogens and Guanine

In this article we study the chemical reactions between guanine and two ultimate carcinogens, the 3,4-quinone forms of the estrogens estrone (E1) and estradiol (E2). DNA was truncated to guanine, i.e. no deoxyribose moiety was included. Due to a complex reaction that involves proton transfer via water molecules we applied linear free energy relationships rather than computation of the transition state and activation energies. The minima corresponding to reactants and products were obtained on the B3LYP/6-31G(d) level. The effects of hydration were considered using the solvent reaction field of Tomasi and co-workers and the Langevin dipoles model of Florian and Warshel. No significant difference in reaction free energy for the reaction involving estrone and estradiol metabolites was found, despite the fact that for the two substances different carcinogenic activities were reported. Differences in carcinogenicity may be therefore attributed to other types of interactions or reactions such as (i) specific interactions of the carbonyl or hydroxyl group with DNA giving rise to different activation free energies for the reactions, (ii) the reaction of depurination and subsequent effects on the DNA, (iii) enzymatic or nonenzymatic oxidation steps (P450, aromatase, peroxidases, O2) and detoxification reactions (catechol-O-methyl transferase, S-transferase), or (iv) binding of the hormone to its nuclear receptors.

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.

A multigene test for the risk of sporadic breast carcinoma

BACKGROUND

Although the identification of the BRCA1 and BRCA2 genes have been of great interest, these genes account for less than 5% of all breast carcinoma cases. The remaining cases are sporadic. Reanalysis of a large twin study suggested that genetic factors may play a significant role in sporadic breast and other carcinomas. Sporadic breast carcinoma is polygenically inherited. Multiple genes are likely to have an additive effect, each gene accounting for a fraction of the variance. One factor that may have an impact on the development of hormonally responsive breast tumors is the duration of exposure of the breast to estrogen. Therefore, one of the demographic risk factors for breast carcinoma is an early age of onset of menarche. The current study was based on the hypothesis that genes that play a role in demographic risk factors may be breast carcinoma risk genes in their own right. The authors hypothesized that six genes relevant to the timing of the onset of menarche and related risk factors might be candidate genes for breast carcinoma. These were the leptin gene (LEP), the leptin receptor gene (LEPR), the catechol-0-methyltransferase gene (COMT), the dopamine D(2) receptor gene (DRD2), the estrogen 1 receptor gene (ESR1), and the androgen receptor gene (AR).

METHODS

The authors examined 67 women with postmenopausal sporadic breast carcinoma and 145 gender and race-matched controls.

RESULTS

Five of these genes accounted for a significant percent of the variance (r(2)) of breast carcinoma. The following r(2) and P values were calculated: LEP: 0.073, P < or = 0.0001; LEPR: 0.064, P < or = 0.0002; COMT: 0.073, P < or = 0.0001; AR: 0.040, P < or = 0.0035; and DRD2: 0.018, P < or = 0.05. When evaluated in a multivariate regression analysis, they accounted collectively for 24% of the variance of breast carcinoma (P < or = 0.0001). These genes accounted for 40% of the variance (P < or = 0.00001) in a subset of age-matched cases. Individual gene scores were added to form a breast carcinoma risk score (BCRS) that ranged from 0 to 17. When the BCRS was evaluated in a receiver operator characteristic plot, the area under the curve was 0.80 for the full set and 0.869 for the age-matched set. The relative breast carcinoma risk for the different BCRS scores ranged from 0.10 to 11.9.

CONCLUSIONS

These results demonstrate a potentially powerful method of evaluating the additive effect of multiple breast carcinoma risk genes to form a potentially clinically useful assessment of women's risk for sporadic breast carcinoma.

Genetic modelling of the estrogen metabolism as a risk factor of hormone-dependent disorders

Estradiol is a pleiotropic hormone, involved in the etiology of a wide variety of diseases. Over the last decade individual genetic variability of the estradiol metabolism has been described as a significant contributor to disease susceptibility with variations depending on ethnic background. Among others, genetic variations of genes encoding cytochrome P450 (CYP) enzymes play an important role in this regard. Mutant alleles of the CYP 1A1 gene are major modulators of lung cancer risk among smokers, mediate gender differences in lung cancer susceptibility, and have been associated with an elevated risk for developing breast, prostate, colorectal, and oral squamous cell cancer. Variants of the CYP 1B1 gene modulate the risk for developing prostate, ovarian, lung, and breast cancer. Also, mutations in the CYP 1B1 gene are the major genetic determinant of congenital glaucoma. Mutant CYP 17 alleles are associated with serum and plasma levels of steroid hormones, use of hormone replacement therapy, and the development of endometrial, prostate, and breast cancer. Available data indicate that the protective effect against breast cancer of a later age at menarche is limited to wild-type CYP 17 allele carriers. Among women with the polycystic ovary syndrome, carriage of mutant CYP 17 alleles is sufficient to aggravate the clinical presentation of the disease. Molecular variants of the CYP 19 gene are associated with an increased risk for developing breast cancer, advanced breast cancer stages, and tumor aromatase production. Carriage of a mutant catechol-O-methyltransferase allele is associated with breast cancer, neurologic disorders such as Parkinson's disease, and modulates behavior among patients with schizophrenia, alcoholics and the general population. In summary, the available evidence points to genes that encode estrogen-metabolizing enzymes as strong hereditary determinants of the susceptibility to benign as well as malignant conditions.

Combined COMT and GST genotypes and hormone replacement therapy associated breast cancer risk

Our previous studies suggested that both COMT and GST genotypes might modify individual breast cancer risk. Here, we extended the studies to examine the potential combined effect of these genotypes in susceptibility to breast cancer. Our study population consisted of 483 Finnish breast cancer cases and 482 population control subjects. The odds ratios (ORs) and (95%) confidence intervals (CIs) were calculated by unconditional logistic regression adjusting for known or suspected confounding factors. No significant increase in the overall breast cancer risk was seen for any combinations of the studied genotypes. However, a substantially increased risk of breast cancer was seen for women who had used hormone replacement therapy (HRT) and simultaneously carried the COMT-L allele containing genotypes and either the GSTP1 Ile/Ile genotype (OR 4.10, 95% CI 1.24-13.6) or the GSTT1 null genotype (OR 4.19, 95% CI 1.30-13.5). These associations appeared to be mainly attributable to long-term users of HRT; the respective ORs were 7.00 (95% CI 1.21-40.6) and 8.36 (95% CI 1.44-49.0) among the users of HRT of more than 30 months. In addition, the combination of COMT-L allele containing genotypes with the GSTM1 null genotype posed a remarkably increased risk (OR 9.10, 95% CI 1.84-45.0) of breast cancer in this study group. These results suggest that the use of HRT could substantially increase the risk of breast cancer among women with specific combinations of the at-risk genotypes of COMT and GST genes.

Three loci modify growth of a transgene-induced mammary tumor: suppression of proliferation associated with decreased microvessel density

In earlier studies it was observed that the genetic background significantly affected the phenotype of a transgene-induced mammary tumor. Tumors arising in an (I/LnJ x PyMT) F1 hybrid background appeared earlier than in the FVB/N-TgN(MMTV-PyVT)(634Mul) parent, but accumulated less tumor mass, indicating a net decrease in tumor growth. Quantitative genetic mapping in a backcross identified three loci that were associated with the decreased proliferative capacity of the I/LnJ F1 tumors. Molecular analysis of the tumors suggests that these loci may act by restricting the tumor's ability to recruit microvessels. The three loci, designated Mmtg1-3, are unlinked to the angiogenic genes Fgf2, Flt1, Flk4, Flk1, Vegf, and Vegfc, as well as the precursors of the endogenous antiangiogenic molecules angiostatin and endostatin. The Mmtg loci may therefore provide novel targets for antiangiogenic therapeutic strategies.

Magnifying endoscopic observation of the gastric mucosa, particularly in patients with atrophic gastritis

The gastric mucosal surface was observed using the magnifying fibergastroscope (FGS-ML), and the fine gastric mucosal patterns, which were even smaller than one unit of gastric area, were examined at a magnification of about 30. For simplicification, we classified these patterns by magnifying endoscopy in the following ways; FP, FIP, FSP, SP and MP, modifying Yoshii's classification under the dissecting microscope. The FIP, which was found to have round and long elliptical gastric pits, is a new addition to our endoscopic classification. The relationship between the FIP and the intermediate zone was evaluated by superficial and histological studies of surgical and biopsy specimens. The width of the band of FIP seems to be related to the severity of atrophic gastritis. Also, the transformation of FP to FIP was assessed by comparing specimens taken from the resected and residual parts of the stomach, respectively. Moreover, it appears that severe gastritis occurs in the gastric mucosa which shows a FIP. Therefore, we consider that the FIP indicates the position of the atrophic border.