Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0006142 (breast cancer)
 160,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cytochrome P450 (CYP)1A1 and CYP1B1, which are under the regulatory control of the aryl hydrocarbon (Ah) receptor (AhR), catalyze the metabolic activation of numerous procarcinogens and the hydroxylation of 17beta-estradiol (E2) at the C-2 and C-4 positions, respectively. There is evidence of cross-talk between estrogen receptor alpha (ERalpha)- and AhR-mediated signaling in breast and endometrial cells. To further examine these interactions, we investigated the short- and long-term effects of E2 exposure on Ah responsiveness in MCF-7 human breast cancer cells. Short-term exposure to 1 nM E2 elevated the ratio of the 4- to 2-hydroxylation pathways of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced E2 metabolism and the ratio of the induced CYP1B1 to CYP1A1 mRNA levels, as determined by real-time PCR. Cells maintained long-term (9-12 months) in low-E2 medium progressively lost Ah responsiveness, as indicated by diminished rates of TCDD-induced E2 metabolism and ethoxyresorufin O-deethylase activity, and the reduced expression of the CYP1A1 and CYP1B1 mRNAs and proteins levels. These E2-deprived cells showed elevated levels of ERalpha mRNA, depressed levels of AhR mRNA, and unchanged levels of the AhR nuclear translocator mRNA. Transient transfection studies using a CYP1B1-promoter-luciferase reporter construct showed that reduced CYP1B1 promoter activity in E2-deprived cells could be restored by co-transfection with an AhR expression construct, indicating that AhR expression was limiting in these cells. The reduced Ah responsiveness of E2-deprived cells was reversed by culture for four passages in medium supplemented with 1 nM E2; ERalpha and AhR mRNAs returned to near-normal levels and the inducibility of the CYP1A1 and CYP1B1 mRNAs, proteins, and E2 metabolic activities by TCDD was restored. These studies indicate that the continued presence of estrogen is required to maintain high levels of AhR expression and inducibility of the procarcinogen-bioactivating enzymes, CYP1A1 and CYP1B1, in MCF-7 cells.
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PMID:Estrogen regulates Ah responsiveness in MCF-7 breast cancer cells. 1297 67

An increased risk of developing endometrial cancer is observed in breast cancer patients treated with tamoxifen (TAM) and in healthy women undergoing TAM chemoprevention therapy. TAM-DNA adducts were detected in the endometrium of women taking TAM (Shibutani, S., et al. (2000) Carcinogenesis 21, 1461-1467) and are formed primarily through O-sulfonation of alpha-hydroxytamoxifen (alpha-OHTAM). To explore the genotoxicic mechanisms of TAM, TAM was incubated with one of multiple human cytochrome P450 enzymes, i.e., P450 1A1, 1A2, 1B1, 2A6, 2B6, 2C8, 2C9, 2C18, 2C19, 2D6, 2E1, 3A4, 3A5, 3A7, 4A11, 4F2, 4F3A, or 4F3B, in a NADPH regenerating system, and the metabolites were identified using HPLC/UV analysis with authentic standards. Among the 18 human P450 enzymes, P450 3A4 generated a significant amount of alpha-OHTAM. When some rat P450 enzymes were examined, P450 3A2 also catalyzed alpha-hydroxylation of TAM. Similarly, human P450 3A4 and rat P450 3A1 and 3A2 converted toremifene (TOR, a chlorinated TAM analogue) to alpha-hydroxytoremifene (alpha-OHTOR). The formation of alpha-OHTAM and alpha-OHTOR by these P450 enzymes was confirmed by tandem mass spectroscopy. Only the P450 3A subfamily enzymes are able to alpha-hydroxylate TAM and TOR. Although the formation of alpha-OHTOR by these enzymes was much higher than that of alpha-OHTAM, TOR is known to be much less genotoxic than TAM. The results support our proposed mechanism that the lower genotoxicity of TOR is due to limited O-sulfonation of alpha-OHTOR by hydroxysteroid sulfotransferases, resulting in the poor formation of DNA adducts (Shibutani, S., et al. (2001) Cancer Res. 61, 3925-3931).
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PMID:Alpha-hydroxylation of tamoxifen and toremifene by human and rat cytochrome P450 3A subfamily enzymes. 1297 2

Genetic polymorphisms of enzymes involved in the metabolism of xenobiotics and estrogens might play a role in breast carcinogenesis related to environmental exposures. In a case-only study on 282 women with breast cancer, we studied the interaction effects (ORi) between smoking habits and the gene polymorphisms of Cytochrome P450 1B1 (Val432Leu CYP1B1), Phenol-sulfotransferase 1A1 (Arg213His SULT1A1) and Catechol-O-methyltransferase (Val158Met COMT). The smokers carrying the Val CYP1B1 allele associated with a high hydroxylation activity had a higher risk of breast cancer than never smokers with the Leu/Leu genotype (ORi=2.32, 95%CI: 1.00-5.38). Also, the smokers carrying the His SULT1A1 allele associated with a low sulfation activity had a 2-fold excess risk compared to never smokers carrying Arg/Arg SULT1A1 common genotype (ORi= 2.55, 95%CI: 1.21-5.36). The His SULT1A1 allele increased the risk only in premenopausal patients. The Met COMT allele with a lower methylation activity than Val COMT did not modify the risk among smokers. The excess risk due to joint effect could result from a higher exposure to activated tobacco-compounds for women homo/heterozygous for the Val CYP1B1 allele. Also, a lower sulfation of the tobacco carcinogens among women with His SULT1A1 could increase exposure to genotoxic compounds. Alternatively, the Val CYP1B1 or His SULT1A1 allele with modified ability to metabolize estrogens could increase the level of genotoxic catechol estrogen (i.e., 4-hydroxy-estradiol) among smokers. Our study showed that gene polymorphisms of CYP1B1 and SULT1A1 induce an individual susceptibility to breast cancer among current smokers.
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PMID:Interactions between genetic polymorphism of cytochrome P450-1B1, sulfotransferase 1A1, catechol-o-methyltransferase and tobacco exposure in breast cancer risk. 1452 Jul 6

The aryl hydrocarbon receptor (AhR), when activated by exogenous ligands such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), regulates expression of several phase I and phase II enzymes and is also involved in the regulation of cell proliferation. Several studies suggest that endogenous AhR ligand(s) may exist. One putative endogenous ligand is indirubin, which was recently identified in human urine and bovine serum. We determined the effect of indirubin in MCF-7 breast cancer cells on induction of the activities of cytochromes P450 (CYP) 1A1 and 1B1, as measured by estradiol and ethoxyresorufin metabolism, and on induction of the CYP1A1 and CYP1B1 mRNAs. With 4-hr exposure, the effects of indirubin and TCDD at 10nM on CYP activity were comparable, but the effects of indirubin, unlike those of TCDD, were transitory. Indirubin-induced ethoxyresorufin-O-deethylase activity was maximal by 6-9 hr post-exposure and had disappeared by 24 hr, whereas TCDD-induced activities remained elevated for at least 72 hr. The effects of indirubin on CYP mRNA induction were maximal at 3 hr. Indirubin was metabolized by microsomes containing cDNA-expressed human CYP1A1 or CYP1B1. The potency of indirubin was comparable to that of TCDD in a CYP1B1-promoter-driven luciferase assay, when MCF-7 cells were co-exposed to the AhR ligands together with the CYP inhibitor, ellipticine. Thus, if indirubin is an endogenous AhR ligand, then AhR-mediated signaling by indirubin is likely to be transient and tightly controlled by the ability of indirubin to induce CYP1A1 and CYP1B1, and hence its own metabolism.
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PMID:Transient induction of cytochromes P450 1A1 and 1B1 in MCF-7 human breast cancer cells by indirubin. 1463 89

The P450 family of proteins has more than 1000 representatives, which despite sometimes relatively low sequence identity have a surprisingly high level of structural similarity. This fact makes this family of proteins ideal candidate for various types of modeling based on protein structure prediction. A number of P450 proteins, including CYPs 1A1, 1A2, 1B1, 3A4, 11B2, 17, and 19, play a role in the metabolism of estrogen. Inhibitors of these proteins could be very promising drugs for hormonal treatment of postmenopausal breast cancer. Population studies have yielded a significant amount of data describing the relationship between single nucleotide polymorphisms (SNP) in DNA and cancer risk related to these proteins. A combination of SNP analysis with protein structure prediction can be a very useful strategy in investigations of structure-functional relations of P450 proteins and structure-based drug design. Here we will demonstrate how protein structure prediction combined with genetic SNP analysis can be useful for potential drug design and possibly, individual treatment of breast cancer.
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PMID:SNP analysis combined with protein structure prediction defines structure-functional relationships in cancer related cytochrome P450 estrogen metabolism. 1503 1

Uridine diphospho-glucuronosyltransferase 1A1 (UGT1A1) is involved in catalyzing estrogen, the hormone that plays a central role in the etiology of breast cancer. A common polymorphism [A(TA)6TAA (allele *1) to A(TA)7TAA change (allele *28)] in the TATA-box of the promoter region of the UGT1A1 gene has been reported to be associated with a reduced transcription of this gene. We investigated the association of this polymorphism with the risk of breast cancer among 1047 breast cancer cases and 1083 community controls in the Shanghai Breast Cancer Study, a population-based case-control study. Approximately same proportion of cases (12.5%) and controls (13.0%) carried the variant allele *28 in the Chinese population (p = 0.32). When stratified by age, carrying the *28 allele was associated with an increased risk of breast cancer among women aged less than 40 years (odds ratio [OR] = 1.7; 95% CI = 1.0-2.7) but not among women 40 years old and over (OR = 0.8; 0.7-1.1). Only a few women were homozygous for the *28 allele, precluding a detailed gene-dose association analysis. Additional analyses showed that, the elevated risk associated with the UGT1A1 *28 allele among young women was primarily seen in women who had a later menarche, short menstrual years, absence of family history of breast cancer, low waist-to-hip ratio, or low body-mass index. These results suggested that the *28 allele in the UGT1A1 gene may be associated with an increased risk for breast cancer among Chinese women under age 40. No significant associations were observed with *28 allele and breast cancer risk by estrogen receptor/progesterone receptor status.
Breast Cancer Res Treat 2004 Jun
PMID:Genetic polymorphisms in uridine diphospho-glucuronosyltransferase 1A1 (UGT1A1) and risk of breast cancer. 1511 62

The position of the nitro group determines the relative carcinogenic activities of mono-nitropyrene isomers (mono-NPs) in the rat mammary gland. To determine whether the results obtained in rodents treated with these environmental pollutants can be applicable to humans, we examined their metabolic activation in primary cultures of human breast cells derived from reduction mammoplasty, as well as in the cultured human breast cancer cell line MCF-7 and the immortalized human mammary epithelial cell line MCF-10A. Primary cultures as well as cell lines were competent in metabolizing all three isomers via both ring oxidation and nitro reduction pathways. Qualitatively similar metabolic patterns were observed but quantitative differences were evident. On the basis of cochromatography with synthetic standards in two HPLC systems, metabolites of 1-NP were identified as 1-OH-Py, 3-, 6-, and 8-OH-1-NP and 1-AP. In the case of 2-NP, 6-OH-2-NP and 2-AP were identified. 4-NP was metabolized to 9,10-DHD-4-NP, Py-4,5-Q, 9,10-Q-4-NP, 9/10-OH-4-NP, 6/ 8-OH-4-NP, and 4-AP. Varying degrees of sulfate and glucuronide conjugation of mono-NP metabolites were detected. In MCF-7 cells, we found that 1-, 2-, and 4-NP bind to DNA at levels of 68, 17, and 132 pmol/mg DNA, respectively. Following HPLC analysis of the DNA hydrolysates, we detected multiple DNA adducts including those derived from nitro reduction of 2- and 4-NP; however, none was detected in the case of 1-NP. To determine the P450 enzymes responsible for the metabolic activation of these carcinogens, we incubated [(3)H]mono-NPs with recombinant human P450 1A1 or 1B1. Metabolites identified were primarily derived from ring oxidation; both P450s 1A1 and 1B1 yielded similar metabolic profiles. This is the first report demonstrating that human breast (target organ) cells, immortalized human mammary epithelial cell line MCF-10A, and breast cancer cell line MCF-7 are capable of activating mono-NPs to metabolites that can damage DNA.
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PMID:Human cytochromes P450 1A1 and 1B1 catalyze ring oxidation but not nitroreduction of environmental pollutant mononitropyrene isomers in primary cultures of human breast cells and cultured MCF-10A and MCF-7 cell lines. 1531 Feb 39

Estrogens and their oxidative metabolites, the catechol estrogens, have been implicated in the development of breast cancer; yet, relatively little is known about estrogen metabolism in the breast. To determine how the parent hormone, 17 beta-estradiol (E(2)), is metabolized, we used recombinant, purified phase I enzymes, cytochrome P450 (CYP) 1A1 and 1B1, with the phase II enzymes catechol-O-methyltransferase (COMT) and glutathione S-transferase P1 (GSTP1), all of which are expressed in breast tissue. We employed both gas and liquid chromatography with mass spectrometry to measure E(2), the catechol estrogens 2-hydroxyestradiol (2-OHE(2)) and 4-hydroxyestradiol (4-OHE(2)), as well as methoxyestrogens and estrogen-GSH conjugates. The oxidation of E(2) to 2-OHE(2) and 4-OHE(2) was exclusively regulated by CYP1A1 and 1B1, regardless of the presence or concentration of COMT and GSTP1. COMT generated two products, 2-methoxyestradiol and 2-hydroxy-3-methoxyestradiol, from 2-OHE(2) but only one product, 4-methoxyestradiol, from 4-OHE(2). Similarly, GSTP1 yielded two conjugates, 2-OHE(2)-1-SG and 2-OHE(2)-4-SG, from the corresponding quinone 2-hydroxyestradiol-quinone and one conjugate, 4-OHE(2)-2-SG, from 4-hydroxyestradiol-quinone. Using the experimental data, we developed a multicompartment kinetic model for the oxidative metabolism of the parent hormone E(2), which revealed significant differences in rate constants for its C-2 and C-4 metabolites. The results demonstrated a tightly regulated interaction of phase I and phase II enzymes, in which the latter decreased the concentration of catechol estrogens and estrogen quinones, thereby reducing the potential of these oxidative estrogen metabolites to induce DNA damage.
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PMID:In vitro model of mammary estrogen metabolism: structural and kinetic differences between catechol estrogens 2- and 4-hydroxyestradiol. 1537 60

Phortress (the dihydrochloride salt of the lysylamide prodrug of 2-(4-amino-3-methylphenyl)-5-fluoro-benzothiazole (5F 203)) is an experimental antitumor agent with potent and selective activity against human-derived carcinomas of breast, ovarian and renal origin. UK clinical trials of Phortress are scheduled to begin in 2004. The mechanism of action of Phortress is distinct from all classes of chemotherapeutic agents currently in the clinic, and involves metabolic activation by cytochrome P450 (CYP) 1A1 to electrophilic species, which generate DNA adducts in sensitive tumors only. In the present study, the antitumor efficacy of Phortress has been compared with that of doxorubicin (Dox) in nine human-derived mammary carcinoma xenograft models, cultivated subcutaneously in the flanks of nude mice. In addition, cyp1a1 mRNA expression was measured in tumors of control and treated animals. Phortress compared favorably with Dox: significant activity, independent of estrogen receptor (ER) status, was established in 7/9 xenografts; in one xenograft model, Phortress elicited superior antitumor activity; no model demonstrated complete resistance to Phortress. In accordance with this observation, all xenografts available for examination (8) displayed clear induction of cyp1a1 expression upon treatment of mice with Phortress whereas Dox failed to induce cyp1a1 expression in all models. Prolonged viability of tumor fragments, recovered for treatment ex vivo could not be sustained; thus correlations between tumor cells' response to Phortress and cyp1a1 or cyp1b1 inducibility following 5F 203 treatment could not be determined with confidence.
Breast Cancer Res Treat 2004 Sep
PMID:The experimental antitumor agents Phortress and doxorubicin are equiactive against human-derived breast carcinoma xenograft models. 1537 55

Estrogen has been suggested to trigger breast cancer development via an initiating mechanism involving its metabolite, catechol estrogen (CE). To examine this hypothesis, we carried out a multigenic case-control study of 469 incident breast cancer patients and 740 healthy controls to define the role of important genes involved in the different metabolic steps that protect against the potentially harmful effects of CE metabolism. We studied the 3 genes involved in CE detoxification by conjugation reactions involving methylation (catechol-O-methyltransferase, COMT), sulfation (sulfotransferase 1A1, SULT1A1), or glucuronidation (UDP-glucuronosyltransferase 1A1, UGT1A1), one (manganese superoxide dismutase, MnSOD) involved in protection against reactive oxidative species-mediated oxidation during the conversion of CE-semiquinone (CE-SQ) to CE-quinone (CE-Q), and 2 of the glutathione S-transferase superfamily, GSTM1 and GSTT1, involved in CE-Q metabolism. Support for this hypothesis came from the observations that (i) there was a trend toward an increased risk of breast cancer in women harboring a greater number of putative high-risk genotypes of these genes (p < 0.05); (ii) this association was stronger and more significant in those women who were more susceptible to estrogen [no history of pregnancy or older (> or =26 years) at first full-term pregnancy (FFTP)]; and (iii) the risks associated with having one or more high-risk genotypes were not the same in women having experienced different menarche-to-FFTP intervals, being more significant in women having been exposed to estrogen for a longer period (> or =12 years) before FFTP. Furthermore, because CE-Q can attack DNA, leading to the formation of double-strand breaks (DSB), we examined whether the relationship between cancer risk and the genotypic polymorphism of CE-metabolizing genes was modified by the genotypes of DSB repair genes, and found that a joint effect of CE-metabolizing genes and one of the two DSB repair pathways, the homologous recombination pathway, was significantly associated with breast cancer development. Based on comprehensive CE metabolizing gene profiles, our study provides support to the hypotheses that breast cancer can be initiated by estrogen exposure and that increased estrogen exposure confers a higher risk of breast cancer by causing DSB to DNA.
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PMID:Breast cancer risk associated with genotype polymorphism of the catechol estrogen-metabolizing genes: a multigenic study on cancer susceptibility. 1545 71


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