Genetic polymorphisms of cytochrome P450 19 and 1B1, alcohol use,and breast cancer risk in Korean women

A case-control study was performed to assess the potential influence of CYP19 Arg(264)Cys and CYP1B1 Leu(432)Val polymorphisms on breast cancer risk in a series of Korean breast cancer patients and controls. The results suggest that the CYP19 Arg(264)Cys polymorphism modifies breast cancer risk (OR=1.5, 95% CI=1.1-2.2), especially in association with alcohol consumption (P for interaction=0.04), whereas the CYP1B1 Leu(432)Val polymorphism appears to play no role here.     

Polymorphisms in the CYP1B1 gene are associated with increased risk of prostate cancer

CYP1B1 has been evaluated as a candidate gene for various cancers because of its function in activating environmental procarcinogens and catalysing the conversion of oestrogens to genotoxic catechol oestrogens. To test the hypothesis that genetic polymorphisms in the CYP1B1 gene may associate with the risk for prostate cancer (CaP), we compared the allele, genotype, and haplotype frequencies of 13 single nucleotide polymorphisms (SNPs) of CYP1B1 among 159 hereditary prostate cancer (HPC) probands, 245 sporadic CaP cases, and 222 unaffected men. When each of the SNPs was analysed separately, marginally significant differences were observed for allele frequencies between sporadic cases and controls for three consecutive SNPs (-1001C/T, -263G/A, and -13C/T, P=0.04-0.07). Similarly, marginally significant differences between sporadic cases and controls in the frequency of variant allele carriers were observed for five consecutive SNPs (-1001C/T, -263G/A, -13C/T, +142C/G, and +355G/T, P=0.02-0.08). Interestingly, when the combination of these five SNPs was analysed using a haplotype approach, a larger difference was found (P=0.009). One frequent haplotype (C-G-C-C-G of -1001C/T, -263G/A, -13C/T, +142C/G, and +355G/T) was associated with an increased risk for CaP, while the other frequent haplotype (T-A-T-G-T) was associated with a decreased risk for CaP. These findings suggest that genetic polymorphisms in CYP1B1 may modify the risk for CaP.     

Molecular epidemiological study of non-small-cell lung cancer from an environmentally polluted region of Poland.

The p53 mutation spectrum can generate hypotheses linking carcinogen exposure to human cancer. Although it is well-documented that tobacco smoking is a major cause of lung cancer, the contribution of air pollution is less well-established. We determined the molecular and immunohistochemical changes (p53 gene mutations, p53 protein accumulation and WAF1 protein expression) and genetic polymorphisms of GSTM1, CYP1A1 and CYP2D6 genes in a case series of non-small-cell lung cancers from Silesia. This region of southern Poland is highly industrialized with considerable environmental pollution. More than 50% of lung cancers (90/164) contained p53 mutations and 75% showed the combined alteration of the p53 gene and protein accumulation. Males occupationally exposed to coal-derived substances showed a relatively high frequency of squamous and large-cell carcinomas, relatively frequent mutations in codon 298 of p53 and a low frequency of p53 immunohistochemically positive tumours. Codon 298 GAG-->TAG mutations have rarely been found in lung cancers in other populations. We found no correlation between WAF1 protein expression and mutations in the p53 gene or p53 protein accumulation. No statistically significant relationship was found between p53 mutations and GSTM1, CYP1A1, CYP2D6 genotypes. Never smokers with lung cancers from Silesia had a higher frequency of G:C-->T:A transversions than previously reported of the p53 mutation spectrum in never smokers (6/15 vs 4/34; P = 0.06 by chi2). These data are a tentative indication that occupational and environmental exposure to polycyclic aromatic hydrocarbons, such as benzo(a)pyrene, in polluted air contributes to the molecular pathogenesis of lung cancer in never smokers.     

CYP1B1 expression is induced by docetaxel: effect on cell viability and drug resistance

The cytochrome P450 CYP1B1 is consistently overexpressed in tumour cells as compared to their normal counterparts, but its precise role in drug resistance is yet to be defined. It has been reported that transfection of CYP1B1 results in increased resistance to docetaxel in V79 cells (McFadyen et al, 2001). In this study, we analysed changes in expression of CYP1B1 mRNA associated with pulse selection of MCF-7 cells with docetaxel. Docetaxel-selected MCF-7 cells (MCF-7 Txt), which showed increased resistance to this drug as compared to parental MCF-7 cells, showed a noteworthy increase in CYP1B1 mRNA expression, paralleled by increased ethoxyresorufin-O-deethylase (EROD) activity levels. This effect was not observed in cisplatin- or adriamycin-selected MCF-7 cells, or in docetaxel-selected colon, lung or pancreatic carcinoma cells. Short-term treatment with docetaxel induced CYP1B1 mRNA expression in MDA 453 and BT-20 breast carcinoma cells, but not in MCF-7 cells. Transfection of MCF-7 Txt cells with CYP1B1 siRNA did not significantly affect docetaxel-induced toxicity, but it decreased cell survival in the absence of drug. Preincubation of docetaxel with recombinant CYP1B1 did not affect drug toxicity in A549 cells. These results suggest that CYP1B1 does not directly inactivate docetaxel, but rather might promote cell survival in MCF-7 Txt cells, providing an explanation for its association with drug resistance.     

Androgen receptor genotypes predict response to endocrine treatment in breast cancer patients

Background:

The androgen receptor (AR) is frequently expressed in breast cancers. The AR genotype may affect disease-free survival and response to endocrine therapy.

Methods:

In all, 634 women undergoing breast cancer surgery between 2002 and 2008 were followed until 30 June 2010. Six haplotype-tagging single-nucleotide polymorphisms in the AR, and the resulting AR diplotypes, were examined in relation to breast cancer patient characteristics, tumour characteristics, disease-free survival, and response to endocrine treatment.

Results:

Five common AR diplotypes were found. Seventeen rare variants were combined into a composite group. The resulting six AR diplotype groups were clustered into two subgroups, groups A (n=128) and B (n=499), with three diplotypes in each. Patients in group B had larger total breast volume (P=0.024), higher body mass index (BMI) (P=0.050), more axillary lymph node involvement (P_trend=0.020), and higher histological grade (P_trend=0.031). There were 59 breast cancer events in the 569 patients with invasive cancers and no preoperative treatment. Patients in group B also had shorter disease-free survival (P=0.037) than patients in group A. Among patients in group B with oestrogen receptor α positive tumours, tamoxifen (TAM) treatment was associated with longer disease-free survival (P=0.008), while treatment with aromatase inhibitors (AIs) was not (P=0.94). Response to endocrine treatment could not be predicted based on BMI, suggesting that the effect of AR diplotypes went beyond that of a higher BMI.

Conclusion:

A marker for a group of patients who responded to TAM, but not to AIs, was identified. If this finding is confirmed, AR genotyping may provide useful information for selection of endocrine treatment of breast cancer patients.     

Association of CYP2E1 gene polymorphism with predisposition to cancer development

We summarize research results on association of cytochrome P450 2E1 (CYP2E1) genetic polymorphisms with the development of ecologically determined cancers. Cytochrome P450 monooxygenase enzyme system is involved in metabolic activation of procarcinogens, which is an important stage during normal cell transformation into a malignant one. Studies of association between CYP2E1 gene polymorphisms and the risk of cancer development are of particular interest, since the enzyme participates in bio-transformation of numerous procarcinogens. We place special emphasis on characterization of known CYP2E1 polymorphisms and analysis of their role in pathogenesis of various cancer types. Results obtained provide evidence on association of CYP2E1 genetic polymorphisms both with increased and decreased risk of development of malignant tumors. Ethnic and geographic peculiarities were also identified for frequencies of CYP2E1 variants distribution.     

Low expression of bcl-2 in Brca1-associated breast cancers

Little data are available concerning the molecular mechanisms of action of Brca1 and Brca2 in breast oncogenesis. Recent experimental results suggest that Brca1 plays a role in the regulation of apoptosis. In order to determine whether the analysis of human tumours would provide data supporting this hypothesis, we have assessed the expression of the antiapoptotic bcl-2 and of the proapoptotic p53 genes in Brca1 - and Brca2 -associated breast carcinomas. The levels of expression of these genes were compared to those observed in controls and to the mitotic and the apoptotic indexes. Our series were composed of 16 cases of breast carcinoma in women with a germline Brca1 gene mutation, and of four cases with Brca2 mutation. A group of 39 patients aged under 36 years and for whom the search for Brca1 gene mutations was negative, and a group of 36 cases of sporadic cancers without data on their Brca status were used as controls. Immunohistochemistry was used to detect p53 and bcl-2 gene products. Mitotic and apoptotic indexes were higher in Brca1 -associated tumours than in controls. No significant difference in p53 immunostaining was observed between the four groups of patients. In contrast, the rate of bcl-2 -positive tumours was lower (31%) in Brca1 -carcinomas than in carcinomas without Brca1 mutation (90%) (P< 10(-3)). A strong Bcl-2 expression was found in the four cases of Brca2 -associated carcinomas. No significant correlation was observed between p53 and Bcl-2 immunostainings, either in cases or in controls. The association between Brca1 status and Bcl-2 expression remained significant after adjustment for the oestrogen receptor status. Our study shows that a low expression of bcl-2 characterises most Brca1 -associated breast carcinomas, a biological trait which seems not to be shared by Brca2 -associated tumours nor to be related to oestrogen receptor and/or p53 status. bcl-2 might thus be one of the target genes involved in the oncogenesis related to Brca1 and its down-regulation may account for the increased apoptosis and the high proliferative rate observed in Brca1 -associated carcinomas.     

Oestrogen receptor beta and neoadjuvant therapy with tamoxifen: prediction of response and effects of treatment

In order to elucidate the relative importance of oestrogen receptor (ER)alpha, ERbeta and an ERbeta variant (ERbeta2/betacx) in the response of breast cancers to tamoxifen, tumour levels of each receptor were assessed in 36 patients before and after 3 months of neoadjuvant treatment with tamoxifen (20 mg daily). All patients were postmenopausal women presenting with large ERalpha-positive breast cancers. Clinical response to treatment was assessed by tumour volume changes as determined from sequential ultrasounds and pathological response by comparison of the tumour morphology before and after treatment. Of 33 cases, 23 (70%) were classified as having a clinical response and 16 (48%) as having a response pathologically. All tumours stained positively for ERalpha and ERbeta and 15 out of 33 (45%) for ERbeta2/betacx. There were no significant differences in quantitative expression of any receptor between tumours that subsequently responded and that did not, whether response was assessed clinically or pathologically. Tamoxifen treatment was associated with a decrease in ERalpha, but an increase was the most frequent change (17 out of 33) in ERbeta, and no consistent change was evident in staining of the ERbeta2/betacx variant. In summary, ERbeta1 and ERbeta2/betacx variant protein are detected in ERalpha-positive breast tumours but their expression is not associated with a response to tamoxifen. Differential changes in ERalpha and ERbeta were seen with treatment.     

Interactions between genetic polymorphism of cytochrome P450-1B1, sulfotransferase 1A1, catechol-o-methyltransferase and tobacco exposure in breast cancer risk

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.     

The cancer preventative agent resveratrol is converted to the anticancer agent piceatannol by the cytochrome P450 enzyme CYP1B1

Resveratrol is a cancer preventative agent that is found in red wine. Piceatannol is a closely related stilbene that has antileukaemic activity and is also a tyrosine kinase inhibitor. Piceatannol differs from resveratrol by having an additional aromatic hydroxy group. The enzyme CYP1B1 is overexpressed in a wide variety of human tumours and catalyses aromatic hydroxylation reactions. We report here that the cancer preventative agent resveratrol undergoes metabolism by the cytochrome P450 enzyme CYP1B1 to give a metabolite which has been identified as the known antileukaemic agent piceatannol. The metabolite was identified by high performance liquid chromatography analysis using fluorescence detection and the identity of the metabolite was further confirmed by derivatisation followed by gas chromatography-mass spectrometry studies using authentic piceatannol for comparison. This observation provides a novel explanation for the cancer preventative properties of resveratrol. It demonstrates that a natural dietary cancer preventative agent can be converted to a compound with known anticancer activity by an enzyme that is found in human tumours. Importantly this result gives insight into the functional role of CYP1B1 and provides evidence for the concept that CYP1B1 in tumours may be functioning as a growth suppressor enzyme.     

The CYP1B1_1358_GG genotype is associated with estrogen receptor-negative breast cancer

Cytochrome P450 1B1 (CYP1B1) is a major enzyme in the initial catabolic step of estradiol (E2) metabolism and belongs to the multitude of genes regulated by the estrogen receptor alpha (ERalpha). The common non-synonymous polymorphisms CYP1B1_1358_A>G and CYP1B1_1294_C>G increase CYP1B1 enzymatic activity. Given a relationship between CYP1B1 and breast tumor E2 level as well as E2 level and breast tumor ERalpha expression it is of interest to know whether CYP1B1 polymorphisms have an impact on the ERalpha status of breast cancer. We genotyped the GENICA population-based breast cancer case-control collection (1,021 cases, 1,015 controls) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and investigated in cases the association between genotypes and tumor ERalpha status (739 ERalpha positive cases; 212 ERalpha negative cases) by logistic regression. We observed a significant association between the homozygous variant CYP1B1_1358_GG genotype and negative ERalpha status (P = 0.005; OR 2.82, 95% CI: 1.37-5.82) with a highly significant Ptrend for CYP1B1_1358_A>G and negative ERalpha status (P = 0.003). We also observed an association of CYP1B1_1358_GG and negative PR status (P = 0.015; OR 2.36, 95% CI: 1.18-4.70) and a Ptrend of 0.111 for CYP1B1_1358_A>G and negative progesterone receptor (PR) status. We conclude that the CYP1B1_1358_A>G polymorphism has an impact on ERalpha status in breast cancer in that the CYP1B1_1358_GG genotype known to encode higher CYP1B1 activity is associated with ERalpha negativity.     

Association of genetic polymorphisms in CYP19 and CYP1A1 with the oestrogen receptor-positive breast cancer risk

Since tamoxifen has been shown to reduce the risk of oestrogen receptor (ER)-positive, but not ER-negative, breast cancers in a chemoprevention trial (P-1), it is important to develop assays to assess risk factors for ER-positive breast cancer in order to appropriately select candidates for chemoprevention with tamoxifen. Thus, the significance of genetic polymorphisms of genes involved in oestrogen biosynthesis (CYP19) and metabolism (CYP1A1) as a risk factor for ER-positive breast cancers was evaluated. A case-control study was conducted with 257 breast cancer patients and 191 healthy female controls. Two polymorphisms, CYP19 (TTTA repeats) in intron 4 and CYP1A1 6235C/T in the 3' non-coding region, and their association with the breast cancer risk after adjustment for the other epidemiological risk factors were examined. CYP19 (TTTA)7(-3bp) allele carriers showed a significantly (P<0.05) increased risk of ER-positive breast cancers (Odds Ratio (OR)=1.72, 95% Confidence Interval (CI) 1.10-2.69), but not ER-negative breast cancers. CYP1A1 6235C allele carriers showed a non-significant (P=0.06) trend towards a decreased risk of ER-positive breast cancers (OR=0.65, 95% CI 0.42-1.02), but not ER-negative breast cancers. The combination of these two polymorphisms was found to be more useful in the assessment of the ER-positive breast cancer risk (OR=3.00, 95% CI=1.56-5.74) than the CYP19 (TTTA)7(-3bp) polymorphism alone. The combination of CYP19 (TTTA)7(-3bp) and CYP1A1 6235C/T polymorphisms is associated with an ER-positive, but not ER-negative, breast cancer risk, and, thus, would be useful in the selection of candidates for chemoprevention with tamoxifen.