Variants in estrogen-biosynthesis genes CYP17 and CYP19 and breast cancer risk: a family-based genetic association study

The CYP19A1 (TTTA)n Repeat Polymorphism May Affect the Prostate Cancer Risk: Evidence from a Meta-Analysis

Abnormal aromatase (CYP19A1) expression may participate in prostate cancer (PCa) carcinogenesis. However, the results of studies on the CYP19A1 gene polymorphisms and PCa are conflicting. This meta-analysis aimed to systematically evaluate the associations between the CYP19A1 Arg264Cys polymorphism and the (TTTA)n repeat polymorphism and PCa. Electronic databases (PubMed, EmBase, ScienceDirect, and Cochrane Library) were comprehensively searched to identify eligible studies. The strength of the association between the Arg264Cys polymorphism and PCa was assessed by pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) in allelic, dominant, recessive, homozygous, and heterozygous genetic models. To analyze the impact of the (TTTA)n repeat polymorphism, we sequentially took the N-repeat allele (where N equals 7,8,10,11,12, and 13) as the minor allele and the sum of all the other alleles as the major allele. The ORs and 95% CIs were calculated in the allelic model; this analysis was performed individually for each repeat number. Pooled estimates of nine studies addressing the Arg264Cys polymorphism indicated that this polymorphism was not associated with PCa risk in the overall population or in the Caucasian or Asian subgroups. The 8-repeat allele in the (TTTA)n repeat polymorphism increased PCa risk in the overall population (OR = 1.34, 95% CI = 1.14-1.58, p = .001) and in the subgroup with population-based (PB) controls (OR = 1.41, 95% CI = 1.13-1.74, p = .002) as well as in the subgroup using capillary electrophoresis to identify this polymorphism (OR = 1.34, 95% CI = 1.09-1.65, p = .006).The meta-analysis indicated that the CYP19A1 (TTTA)n repeat polymorphism, but not the Arg264Cys polymorphism, may affect PCa risk.

Association between single nucleotide polymorphism of the CYP19A1 and ESR2 genes and endometriosis

PURPOSE

Endometriosis is a frequent gynaecological condition, both in Poland and in the world. The development of this disease is supported by hormonal, immunological and environmental factors. During the recent years, a particular attention has been focused on the genetic polymorphisms which may be of particular significance for the increased incidence rates of endometriosis. According to literature data, Oestrogen Receptor 2 (ESR2) and Cytochrome P450 Family 19 Subfamily A Member 1 (CYP19A1) genes may be accounted to the potential risk factors of infertility associated with endometriosis. The reported research was aimed to evaluate the association between single nucleotide polymorphisms (SNPs) rs17179740 of ESR2 and rs2899470 of CYP19A1 genes and the incidence of endometriosis.

METHODS

The study material included blood specimens, collected from patients (n = 200) with endometriosis. Blood samples from age-matched, endometriosis-free women (n = 200) served as control. The High-Resolution Melter (HRM) technique was applied for polymorphism analysis.

RESULTS

Regarding rs2899470 polymorphism TT homozygotes was significantly more prevalent among the patients with endometriosis than in the controls (OR 2.19; p = 0.04). In case of rs17179740, GG homozygotes, as well as AG-AA genotypes, were significantly more prevalent among the endometriosis patients (OR 2.48, p = 0.04 and OR 2.36, p = 0.04, respectively).

CONCLUSION

Summing up, the investigated polymorphisms of ESR2 and CYP19A1 gene are associated with the observed incidence of endometriosis.

The Genetic Background of Endometriosis: Can ESR2 and CYP19A1 Genes Be a Potential Risk Factor for Its Development?

Endometriosis is defined as the presence of endometrial foci, localized beyond their primary site, i.e., the uterine cavity. The etiology of this disease is rather complex. Its development is supported by hormonal, immunological, and environmental factors. During recent years, particular attention has been focused on the genetic mechanisms that may be of particular significance for the increased incidence rates of endometriosis. According to most recent studies, ESR2 and CYP19A1 genes may account for the potential risk factors of infertility associated with endometriosis. The paper presents a thorough review of the latest reports and data concerning the genetic background of the risk for endometriosis development.

Epidemiology of estrogen and dementia in women with Down syndrome

Several lines of investigation have shown a protective role for estrogen in Alzheimer's disease through a number of biological actions. This review examines studies of the role of estrogen-related factors in age at onset and risk for Alzheimer's disease in women with Down syndrome, a population at high risk for early onset of dementia. The studies are consistent in showing that early age at menopause and that low levels of endogenous bioavailable estradiol in postmenopausal women with Down syndrome are associated with earlier age at onset and overall risk for dementia. Polymorphisms in genes associated with estrogen receptor activity and in genes for estrogen biosynthesis affecting endogenous estrogen are related to age at onset and cumulative incidence of dementia, and may serve as biomarkers of risk. To date, no clinical trials of estrogen or hormone replacement therapy (ERT/HRT) have been published for women with Down syndrome. While findings from clinical trials of ERT or HRT for dementia have generally been negative among women in the neurotypical population, the short interval between menopause and onset of cognitive decline, together with a more positive balance between potential benefits and risks, suggests an opportunity to evaluate the efficacy of ERT/HRT for delaying or preventing dementia in this high risk population, although questions concerning the optimal formulation and timing of the hormone therapy are not yet resolved.

Association between CYP17 T-34C rs743572 and breast cancer risk

Association between CYP17 T-34C (rs743572) polymorphism and breast cancer (BC) risk was controversial. In order to derive a more definitive conclusion, we performed this meta-analysis. We searched in the databases of PubMed, EMBASE and Cochrane for eligible publications. Pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) were used to assess the strength of association between CYP17 T-34C polymorphism and breast cancer risk. Forty-nine studies involving 2,7104 cases and 3,4218 control subjects were included in this meta-analysis. In overall, no significant association between CYP17 T-34C polymorphism and breast cancer susceptibility was found among general populations. In the stratified analysis by ethnicity and source, significant associations were still not detected in all genetic models; besides, limiting the analysis to studies with controls in agreement with HWE, we also observed no association between CYP17 T-34C polymorphism and breast cancer risk. For premenopausal women, we didn't detect an association between rs743572 and breast cancer risk; however, among postmenopausal women, we observed that the association was statistically significant under the allele contrast genetic model (OR = 1.10, 95% CI = 1.03-1.17, P = 0.003), but not in other four models. In conclusion, rs743572 may increase breast cancer risk in postmenopausal individuals, but not in premenopausal folks and general populations.

[Gender Obesity Report--Influence of obesity on Reproduction and Pregnancy]

Obesity influences reproduction in men and women at all ages. The increasing prevalence of obesity is associated with rising numbers of reproductive disorders in both sexes. Obesity influences menstrual cycle and ovulation irregularities, increases pregnancy complications and complication rates in assisted reproductive technologies in women and in men obesity is associated with lower semen parameters. Weight loss through lifestyle changes or bariatric surgery has positive effects on hormonal parameters and fertility in both men and women.

Variants in CYP17 and CYP19 cytochrome P450 genes are associated with onset of Alzheimer's disease in women with down syndrome

CYP17 and CYP19 are involved in the peripheral synthesis of estrogens, and polymorphisms in CYP17 and CYP19 have been associated with increased risk of estrogen-related disorders. Women with Down syndrome (DS) have early onset and high risk for Alzheimer's disease (AD). We conducted a prospective community-based cohort study to examine the relationship between SNPs in CYP17 and CYP19 and cumulative incidence of AD, hormone levels and sex hormone binding globulin in women with DS. Two hundred and thirty-five women with DS, 31 to 67 years of age and nondemented at initial examination, were assessed for cognitive and functional abilities, behavioral/psychiatric conditions, and health status at 14-20 month intervals over five assessment cycles. We genotyped these individuals for single-nucleotide polymorphisms (SNPs) in CYP17 and CYP19. Four SNPs in CYP17 were associated with a two and one half-fold increased risk of AD, independent of APOE genotype. Four SNPs in CYP19 were associated with a two-fold increased risk of AD, although three were significant only in those without an APOE ε4 allele. Further, carrying high risk alleles in both CYP17 and CYP19 was associated with an almost four-fold increased risk of AD (OR = 3.8, 95% CI, 1.6-9.5) and elevated sex hormone binding globulin in postmenopausal women. The main effect of the CYP17 and CYP19 variants was to decrease the age at onset. These findings suggest that genes contributing to estrogen bioavailability influence risk of AD in women with DS.

MspA1 polymorphism of the CYP17 gene in breast cysts

OBJECTIVE

To study the prevalence of breast cysts in several age groups of the general female population and their association with the MspAI polymorphism of the gene CYP17.

RESULTS

In 204 ultrasound tests, cysts were present in 22% of the studied population. The epidemiological-clinical profile of these women was Caucasian, aged 41-50 years, regular menstrual cycles, multiparous and complaining of mastalgia. The genetic distribution of polymorphisms of the gene displayed Hardy-Weinberg equilibrium and the wild homozygous phenotype was observed in 36.4% of the case group and in 37.6% of the control groups; the heterozygous phenotype was observed in 50% of the study group and 46.3% of control group and a mutated homozygous phenotype was seen in 13.6% of the study group and 16.1% of the controls. There was no statistically significant difference between the groups (p = 0.92).

CONCLUSION

The prevalence and most of the epidemiological profile of breast cysts were in agreement with the literature. There was no statistically significant difference among the genotypic groups (wild homozygous, heterozygous and mutated homozygous), despite a slightly increased frequency of the mutated genotype in the control group. This difference indicates a trend of the MspAI polymorphism of the gene CYP17 to act as a protective factor against the development of breast cysts.

Aromatase activity and bone loss in men

Aromatase is a specific component of the cytochrome P450 enzyme system responsible for the transformation of androgen precursors into estrogens. This enzyme is encoded by the CYP19A1 gene located at chromosome 15q21.2, that is, expressed in ovary and testis, but also in many extraglandular sites such as the placenta, brain, adipose tissue, and bone. The activity of aromatase regulates the concentrations of estrogens with endocrine, paracrine, and autocrine effects on target issues including bone. Importantly, extraglandular aromatization of circulating androgen precursors is the major source of estrogen in men. Clinical and experimental evidences clearly indicate that aromatase activity and estrogen production are necessary for longitudinal bone growth, the attainment of peak bone mass, pubertal growth spurt, epiphyseal closure, and normal bone remodeling in young individuals. Moreover, with aging, individual differences in aromatase activity may significantly affect bone loss and fracture risk in men.

The association of aromatase (CYP19) gene variants with sperm concentration and motility

The irreversible transformation of androgens into oestrogens is catalysed by cytochrome P450 aromatase. In the present study, we explored the contribution of the (TTTA)(n) polymorphism in the aromatase gene (CYP19) to sperm concentration and motility. Ninety normozoospermic and 60 oligospermic men were examined during infertility examinations. DNA was extracted from spermatozoa, and the CYP19 (TTTA)(n) polymorphism was genotyped by PCR. Genotype analysis revealed six CYP19 (TTTA)(n) alleles with 7-12 repeats. The allelic distribution of the CYP19 (TTTA)(n) polymorphism differed between normozoospermic and oligospermic men (P<0.01). Oligospermic men less frequently had long CYP19 alleles than did normozoospermic men (25 and 37.8%, respectively; P<0.02). The higher frequency of short CYP19 alleles in oligospermic men compared to normozoospermic men (43.3 and 28.3%, respectively; P<0.01) was primarily due to the distribution of the CYP19 (TTTA)(7) allele. The CYP19 (TTTA)(7) allele was associated with lower sperm concentration in normozoospermic men (P<0.01) and in the total study population (P<0.01); it was also associated with lower sperm motility in normozoospermic men (P<0.05) and in the total study population (P<0.01). In conclusion, the CYP19 (TTTA)(7) allele probably impairs aromatase activity, which in turn alters aromatase and oestrogen levels in the testis, leading to decreased sperm concentration and motility. These findings support the significance of cytochrome P450 aromatase in human spermatogenesis and consequently in semen quality.

Aromatase activity and bone loss

Aromatase is a specific component of the cytochrome P450 enzyme system that is responsible for the transformation of C19 androgen precursors into C18 estrogenic compounds. This enzyme is encoded by the CYP19A1 gene located at chromosome 15q21.2, that is expressed in ovary and testis not only but also in many extraglandular sites such as the placenta, brain, adipose tissue, and bone. The regulation of the level and activity of aromatase determines the levels of estrogens that have endocrine, paracrine, and autocrine effects on target issues including bone. Importantly, extraglandular aromatization of circulating androgen precursors is the major source of estrogen not only in men (since only 15% of circulating estradiol is released directly by the testis) but also in women after the menopause. Several lines of clinical and experimental evidence now clearly indicate that aromatase activity and estrogen production are necessary for longitudinal bone growth, attainment of peak bone mass, the pubertal growth spurt, epiphyseal closure, and normal bone remodeling in young individuals. Moreover, with aging, individual differences in aromatase activity and thus in estrogen levels may significantly affect bone loss and fracture risk in both genders.

Association of aromatase (TTTAn) repeat polymorphism length and the relationship between obesity and decreased sperm concentration

BACKGROUND

Obesity in men is associated with low sperm count, however, this finding is inconsistent. Here, we describe length of the short tandem repeat aromatase (CYP19A1) polymorphism and its relationship to increased weight and sperm count.

METHODS

A cohort of 215 men was recruited from the community and BMI, hormone levels and sperm parameters were determined at enrollment. Men (196) were genotyped for length of the tetranucleotide TTTA repeats polymorphism (TTTA(n)), defined as short (S ≤ 7 repeats) or long (L > 7 repeats). Genotypes were categorized using allele combinations as 'low repeats' = S-S, or 'high repeats' = S-L/L-L. Weight and sperm parameters were examined in relation to size of TTTA(n) repeat.

RESULTS

Mean (±SD) age was 29.8 ± 8.6 years and mean BMI was 25.6 ± 4.6 kg/m(2). Men with high repeats had higher estradiol (E(2)) levels (98.0 ± 33.36 pmol/l) than men with low repeats (85.9 ± 26.61 pmol/l; P= 0.026). Lower FSH levels tended to be present in men with high repeats versus men with low repeats (P= 0.052). After stratification by genotype, a negative correlation between BMI and sperm count (Pearson's coefficient = 0.406) was seen only among men with high repeats (P= 0.019). Only men with high repeats exhibited increased E(2) with increased weight. A decrease in testosterone: E(2) ratio with increasing BMI was more pronounced in men with high versus low, repeats (R(2) = 0.436 versus 0.281).

CONCLUSIONS

Higher TTTA repeat numbers (>7 repeats) in the aromatase gene are associated with a negative relationship between obesity and sperm count. The effect of obesity on E(2) and sperm count appears to be absent in men with low (≤7) repeats.

Novel pathway analysis of genomic polymorphism-cancer risk interaction in the Breast Cancer Prevention Trial

PURPOSE

Tamoxifen was approved for breast cancer risk reduction in high-risk women based on the National Surgical Adjuvant Breast and Bowel Project's Breast Cancer Prevention Trial (P-1:BCPT), which showed 50% fewer breast cancers with tamoxifen versus placebo, supporting tamoxifen's efficacy in preventing breast cancer. Poor metabolizing CYP2D6 variants are currently the subject of intensive scrutiny regarding their impact on clinical outcomes in the adjuvant setting. Our study extends to variants in a wider spectrum of tamoxifen-metabolizing genes and applies to the prevention setting.

METHODS

Our case-only study, nested within P-1:BCPT, explored associations of polymorphisms in estrogen/tamoxifen-metabolizing genes with responsiveness to preventive tamoxifen. Thirty-nine candidate polymorphisms in 17 candidate genes were genotyped in 249 P-1:BCPT cases.

RESULTS

CVP2D6_C1111T, individually and within a CYP2D6 haplotype, showed borderline significant association with treatment arm. Path analysis of the entire tamoxifen pathway gene network showed that the tamoxifen pathway model was consistent with the pattern of observed genotype variability within the placebo-arm dataset. However, correlation of variations in genes in the tamoxifen arm differed significantly from the predictions of the tamoxifen pathway model. Strong correlations between allelic variation in the tamoxifen pathway at CYP1A1-CYP3A4, CYP3A4-CYP2C9, and CYP2C9-SULT1A2, in addition to CYP2D6 and its adjacent genes, were seen in the placebo-arm but not the tamoxifen-arm. In conclusion, beyond reinforcing a role for CYP2D6 in tamoxifen response, our pathway analysis strongly suggests that specific combinations of allelic variants in other genes make major contributions to the tamoxifen-resistance phenotype.

Lack of association between CYP17 MspA1 polymorphism and breast cancer risk: a meta-analysis of 22,090 cases and 28,498 controls

Epidemiological studies have evaluated the association between CYP17 MspA1 polymorphism and breast cancer risk. However, the results remain conflicting rather than conclusive. 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 35 studies including 22,090 cases and 28,498 controls were identified. Genotype distributions of CYP17 in the controls of all studies were in agreement with Hardy-Weinberg equilibrium (HWE) except for three studies. When all 35 studies were pooled into the meta-analysis, there was no evidence for significant association between CYP17 MspA1 polymorphism and breast cancer risk (for A1/A2 vs. A1/A1: OR = 1.00, 95% CI = 0.96-1.04; for A2/A2 vs. A1/A1: OR = 1.03, 95% CI = 0.97-1.08; for dominant model: OR = 1.01, 95% CI = 0.97-1.05; for recessive model: OR = 1.03, 95% CI = 0.98-1.08). In the subgroup analyses by ethnicity, menopausal status and source of controls, 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 CYP17 MspA1 polymorphism is not associated with increased breast cancer risk.

No association between CYP17 T-34C polymorphism and breast cancer risk: a meta-analysis involving 58,814 subjects

Breast cancer is one of the most common malignant tumors worldwide. To date, many articles have evaluated the association between Cytochrome P450c17 (CYP17) T-34C polymorphism and breast cancer risk. However, the results remain inconclusive. In order to derive a more precise estimation of the association, a meta-analysis was performed in this study. By searching Medline, ISI Web of Knowledge, Cochrane, ScienceDirect, EBSCO, CNKI, and SinoMed databases, 43 studies including 26,008 cases and 32,806 controls were collected for CYP17 T-34C polymorphism. Crude ORs with 95% CIs were used to assess the strength of association between CYP17 T-34C polymorphism and breast cancer risk. The pooled ORs were performed for codominant model, dominant model, and recessive model, respectively. Overall, no significant associations between CYP17 T-34C polymorphism and breast cancer susceptibility were found for TT versus CC (OR = 0.96; 95% CI: 0.89-1.05), TC versus CC (OR = 0.97; 95% CI: 0.89-1.06), TT + TC versus CC (OR = 0.97; 95% CI: 0.89-1.05) and TT versus TC + CC (OR = 0.98; 95% CI: 0.93-1.03). In the stratified analysis by ethnicity, menopausal status, and sources of controls, significant associations were still not detected in all genetic models. In conclusion, this meta-analysis strongly suggests that CYP17 T-34C polymorphism is not associated with breast cancer risk.

An aromatase polymorphism modulates the relationship between weight and estradiol levels in obese men

OBJECTIVE

To describe the influence of the TTTA aromatase polymorphism (TTTAn) on the relation between obesity and plasma estradiol (E(2)) in obese men.

DESIGN

A 2-year cohort study.

SETTING

Clinical research center.

PATIENT(S)

Severely obese men (31 who had had gastric bypass surgery and 118 controls).

INTERVENTION(S)

Men were genotyped for the TTTAn CYP19A1 polymorphism. Anthropomorphic measures, plasma E(2), and other hormonal levels were determined at baseline and 2-year follow-up.

MAIN OUTCOMES MEASURE(S)

Relationships between weight and changes in weight and plasma E(2) were examined in relation to the TTTAn polymorphism.

RESULT(S)

The mean age was 46.5 ± 10.82 years, and mean body mass index was 47.1 ± 8.46 kg/m(2). The most common repeats were 7 and 11. TTTAn number did not correlate with plasma E(2) in the univariate analysis. When patients were stratified per weight group, the correlation between plasma E(2) and weight was seen only among men with a higher TTTA repeat at baseline and 2 years. Similarly, only men with higher TTTA exhibited reduced E(2) levels after weight loss.

CONCLUSION(S)

A higher TTTA repeat is associated with a strengthened relationship between obesity and E(2). The well-established effect of increased weight on plasma E(2) appears to be absent in men with low TTTA numbers.

Two estrogen-related variants in CYP19A1 and endometrial cancer risk: a pooled analysis in the Epidemiology of Endometrial Cancer Consortium

Common variants in CYP19A1 (the A alleles of rs749292 and rs727479) have been associated with a 10% to 20% increase in circulating estrogen levels in postmenopausal women. We hypothesized that the presence of one or both A alleles in these single nucleotide polymorphisms (SNP) is associated with increased endometrial cancer risk. We tested this hypothesis in a large pooled analysis of 4,998 endometrial cancer cases and 8,285 controls from 10 studies in the Epidemiology of Endometrial Cancer Consortium. The majority of women (>66%) were whites, with smaller proportions of other races and ethnic groups (blacks, Asians, and Latinas) also included in this pooled analysis. Unconditional logistic regression was used to model the association between SNPs/haplotypes and endometrial cancer risk. Carrying the A allele of either of these SNPs was associated with an increased risk of endometrial cancer, with pooled odds ratios per allele of 1.14, 95% confidence interval of 1.09-1.21, and P = 7.1 x 10(-7) for rs749292, and odds ratio per allele of 1.08, 95% confidence interval of 1.02-1.14, and P = 0.009 for rs727479. For rs749292, these associations were generally stronger among women age >or=55 years. For both SNPs, risk increased with increasing body mass index, and for rs727479, this pattern seemed stronger among women age >or=55 years (P interaction = 0.007). The combination of A alleles in the two SNPs, either by direct count or by haplotype analysis, did not increase risk above that observed for the individual SNPs. Our study provides evidence that CYP19A1 genetic variation influences susceptibility to endometrial cancer, particularly among older and obese women.

Genetic variation in CYP19A1 and risk of breast cancer and fibrocystic breast conditions among women in Shanghai, China

CYP19A1 encodes for aromatase, which irreversibly converts androgens to estrogens; variation in this gene may affect individual susceptibility to breast cancer and other sex hormone-dependent outcomes. In a case-control study nested within a breast self-examination trial conducted in China, we examined whether CYP19A1 polymorphisms (rs1870049, rs1004982, rs28566535, rs936306, rs11636639, rs767199, rs4775936, rs11575899, rs10046, and rs4646) were associated with risk of breast cancer and fibrocystic breast conditions. Cases were diagnosed with breast cancer (n = 614) or fibrocystic breast conditions (n = 465) during 1989 to 2000. Controls were free of breast disease during the same period (n = 879). Presence of proliferative changes within the extratumoral tissue of women with breast cancer and the lesions of women with fibrocystic conditions only was assessed. None of the polymorphisms were associated with overall risk of breast cancer or fibrocystic breast conditions. Differences in breast cancer risk, however, were observed by proliferation status. The risk of breast cancer with (but not without) proliferative fibrocystic conditions was increased among women homozygous for the minor allele of rs1004982 (C), rs28566535 (C), rs936306 (T), and rs4775936 (C) relative to those homozygous for the major allele [age-adjusted odds ratios (95% confidence intervals), 2.19 (1.24-3.85), 2.20 (1.27-3.82), 1.94 (1.13-3.30), and 1.95 (1.07-3.58), respectively]. Also, haplotypes inferred using all polymorphisms were not associated with overall risk of either outcome, although some block-specific haplotypes were associated with an increased risk of breast cancer with concurrent proliferative fibrocystic conditions. Our findings suggest that CYP19A1 variation may enhance breast cancer development in some women, but further confirmation is warranted.

Polymorphisms in the CYP19A1 (aromatase) gene and endometrial cancer risk in Chinese women

Aromatase, encoded by the CYP19A1 gene, is a key enzyme in estradiol biosynthesis, which catalyzes the conversion of androstenedione and testosterone to estrone and estradiol, respectively. Given the critical role of estrogen in the development of endometrial cancer risk, we evaluated genetic polymorphisms of the CYP19A1 gene, including rs1065779, rs700519, rs28566535, rs752760, and rs1870050, in association with endometrial cancer in a population-based case-control study conducted in Shanghai, China. Genotypes of 1,040 incident endometrial cancer cases and 1,031 frequency-matched controls were included in the study. We applied a logistic regression model to derive adjusted odds ratios (OR) and their 95% confidence intervals (95% CI). Six common haplotypes with a frequency >or=5% were estimated; the highest frequency haplotype was GCACA (27.8% in cases and 26.2% in controls). We observed an inverse association between CYP19A1 haplotype TCATC and endometrial cancer in our population (OR, 0.76; 95% CI, 0.62-0.92). An inverse association was found between endometrial cancer and single nucleotide polymorphism rs1870050 in the promoter region with ORs of 0.81 (95% CI, 0.68-0.97) and 0.58 (95% CI, 0.42-0.80) for the AC and CC genotypes, respectively. We observed a multiplicative interaction between single nucleotide polymorphism rs700519 and body mass index among postmenopausal women (P = 0.01), with stronger associations between rs700519 genotypes and endometrial cancer risk among heavier (body mass index, >or=25) postmenopausal women. In summary, our data show that polymorphisms in the CYP19A1 gene may contribute to endometrial carcinogenesis.

A CYP19 (aromatase) polymorphism is associated with increased premenopausal breast cancer risk

Due to the established association between estrogen levels and breast cancer risk, polymorphic variation in genes regulating estrogen levels is thought to be related to breast cancer risk. Aromatase, the protein product of the CYP19 gene, is involved in the production of endogenous estrogens via androgen conversion. We examined whether polymorphic variation in CYP19 associated with increased breast cancer risk in a population based case-control study. We examined two single nucleotide polymorphisms (SNP), rs1008805 (A/G) and rs730154 (C/T), which have been shown to tag SNPs within two different haplotype blocks in CYP19. Among premenopausal women, the presence of at least one G allele at rs1008805 was significantly associated with an increase in the risk of breast cancer (OR = 1.72 [95% CI, 1.20-2.49]), especially with estrogen and progesterone receptor negative breast cancer (OR = 3.89 [1.74-8.70] and OR = 2.52 [1.26-5.05], respectively). No association was observed among postmenopausal women (OR = 1.06 [0.82-1.36]). There was no significant association between rs730154 and breast cancer, regardless of menopausal status. Our results suggest that premenopausal women carrying the G allele at CYP19 rs1008805 have increased risk of breast cancer. The finding supports the potential role of variation in estrogen biosynthesis genes in premenopausal breast cancer risk.

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.

Role of CYP17 and CYP19 polymorphisms in idiopathic recurrent miscarriages among South Indian women

Recent reports suggest the relevance of gene polymorphisms in predicting reproductive outcome. The present study was aimed at investigating the relationship between the 5' UTR polymorphism of CYP17, a tetranucleotide repeat and a trinucleotide deletion polymorphism in CYP19. A case-control-based study approach was used, which included 143 cases and 88 controls from the South Indian population. A PCR-sequencing based genotyping was used to ascertain the status of the individual. The A1, A2 allele frequencies of CYP17 among the cases were 72 and 28% while among the controls were 68 and 32% respectively (OR 1.21, 95% CI: 0.63-2.32). The 7/7 repeat of CYP19 was the predominant one with a distribution frequency of 55% in the cases and 58% in the controls. The deletion was observed in 39% of the cases and 36% of the controls (OR 1.14, 95% CI: 0.62-2.10). Minor genotypes when taken together represented at a higher frequency in cases than those in controls (13 against 2%, P-value: 0.006). No statistically significant association exists between the CYP17 and CYP19 trinucleotide deletion polymorphisms and the risk of idiopathic recurrent miscarriages among women from South India. However, larger repeat numbers of the tetra nucleotide (except the common 7/11 genotype) showed significant association at 95% level.

Genetic Polymorphisms of the CYP19A1 Gene and Breast Cancer Survival

The CYP19A1 protein (aromatase) plays a critical role in estrogen biosynthesis and thus may be related to the progression of breast cancer. We examined the association between CYP19A1 genetic polymorphisms and breast cancer survival in a cohort of 1,136 patients who were recruited as part of a population-based case-control study in Shanghai, China from 1996 to 1998 and who has donated a DNA sample to the study. Patients were followed for cancer recurrence and mortality through July 2005. Nineteen haplotype tagging single-nucleotide polymorphisms (SNP) in the CYP19A1 gene were evaluated. For each of the five SNPs located in haplotype block 2, patients homozygous for the minor alleles had a reduced 5-year disease-free survival rate compared with those carrying the major allele. The age-adjusted hazard ratios (HR) and 95% confidence intervals (95% CI) were 1.5 (1.1-2.1), 2.1 (1.2-3.6), 1.5 (1.1-2.0), 1.4 (1.0-2.0), and 1.4 (1.0-2.0) for hCV1664178, rs12900137, rs730154, rs936306, and rs1902586, respectively. Haplotype analyses showed that the haplotype CCCTA (all minor alleles of the five SNPs in block 2) was associated with decreased disease-free survival (HR, 1.9; 95% CI, 1.1-3.3). The nonsynonymous SNP, rs700519 (Arg264Cys), located in haplotype block 4, was also associated with breast cancer survival. The age-adjusted HR for the Cys/Cys (T/T) genotype was 2.2 (95% CI, 1.2-4.1) for overall survival and 2.1 (95% CI, 1.1-3.9) for disease-free survival, compared with those carrying the Arg (C) allele. These results suggest that polymorphisms in the CYP19A1 gene may have effects on breast cancer prognosis.

Variants in estrogen metabolism and biosynthesis genes and urinary estrogen metabolites in women with a family history of breast cancer

We examined associations between polymorphisms in genes related to estrogen metabolism (CYP1B1 codon 432G --> C rs#1056836, CYP1B1 codon 453A --> G rs#1800440, COMT codon 158G --> A rs#4680) and biosynthesis (CYP17 T --> C promoter rs#743572, CYP19 exon 4 TTTA repeat) and urinary estrogen metabolites (2-hydroxyestrogens (2-OHE), 16alpha-hydroxyestrone (16alpha-OHE1), and their ratio) in a pilot study of 64 pre- and post-menopausal women with a family history of breast cancer. Women were participants in the Metropolitan New York Registry of Breast Cancer Families, one of six international sites of the National Cancer Institute's Breast Cancer Family Registry. We used linear regression to examine the effects of genetic variants on log-transformed urinary estrogen metabolites. After adjusting for menopausal status, BMI, and age, carriers of the CYP1B1 codon 453G variant allele had 31.0% lower levels of 2-OHE (P-value = 0.05) and 40.2% lower levels of 16alpha-OHE1 (P = 0.01). Results were similar after restricting the analyses to pre-menopausal women (n = 41). Consistent with other studies, among pre-menopausal women, carriers of the COMT codon 158A variant allele had increased 2-OHE levels (P = 0.03) and an increased 2-OHE/16alpha-OHE1 ratio (P = 0.04); carriers of the CYP17 C promoter variant allele had increased 2-OHE levels (P = 0.08). To our knowledge this is the first report showing associations between the CYP1B1 codon 453G variant allele and urinary 2-OHE and 16alpha-OHE1 metabolites. Further larger studies should be conducted to confirm these results. Future identification of individuals with genetic polymorphisms that affect estrogen metabolism and biosynthesis may help characterize women at higher breast cancer risk and could guide breast cancer prevention strategies for those individuals.

CYP17 gene polymorphism in relation to breast cancer risk: a case-control study

Introduction

The c.1-34T>C 5' promoter region polymorphism in cytochrome P450c17 (CYP17), a key enzyme in the biosynthesis of estrogen, has been associated with breast cancer risk, but most previous studies have been relatively small.

Methods

We genotyped 1,544 incident cases of primary breast cancer and 1,502 population controls, all postmenopausal Swedish women, for the CYP17 c.1-34T>C polymorphism and calculated odds ratios (ORs) and 95% confidence intervals (CIs) from logistic regression models.

Results

No overall association was found between CYP17 c.1-34T>C and breast cancer risk, OR 1.0 (95% CI 0.8–1.3) for the A2/A2 (CC) carriers compared to the A1/A1 (TT) carriers, regardless of histopathology. We detected an interaction between CYP17 c.1-34T>C and age at menarche (P = 0.026) but regarded that as a chance finding as no dose-response pattern was evident. Other breast cancer risk factors, including menopausal hormone use and diabetes mellitus, did not modify the overall results.

Conclusion

It is unlikely that CYP17 c.1-34T>C has a role in breast cancer etiology, overall or in combination with established non-genetic breast cancer risk factors.

Covariate adjustment in family-based association studies

Family-based tests of association between a candidate locus and a disease evaluate how often a variant allele at the locus is transmitted from parents to offspring. These tests assume that in the absence of association, an affected offspring is equally likely to have inherited either one of the two homologous alleles carried by a parent. However, transmission distortion was documented in families in which the offspring are unselected for phenotype. Moreover, if offspring genotypes are associated with a risk factor for the disease, transmission distortion to affected offspring can occur in the absence of a causal relation between gene and disease risk. We discuss the appropriateness of adjusting for established risk factors when evaluating association in family-based studies. We present methods for adjusting the transmission/disequilibrium test for risk factors when warranted, and we apply them to data on CYP19 (aromatase) genotypes in nuclear families with multiple cases of breast cancer. Simulations show that when genotypes are correlated with risk factors, the unadjusted test statistics have inflated size, while the adjusted ones do not. The covariate-adjusted tests are less powerful than the unadjusted ones, suggesting the need to check the relationship between genotypes and known risk factors to verify that adjustment is needed. The adjusted tests are most useful for data containing a large proportion of families that lack disease-discordant sibships, i.e., data for which multiple logistic regression of matched sibships would have little power. Software for performing the covariate-adjusted tests is available at http://www.stanford.edu/dept/HRP/epidemiology/COVTDT.