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

Association of CYP19A1 single-nucleotide polymorphism with digit ratio (2D:4D) in a sample of men and women from Ningxia (China)

OBJECTIVES

2D:4D is an anthropometric indicator that may reflect the level of intrauterine sexual hormone exposure before birth. The aromatase gene (CYP19A1) mainly encodes cytochrome P450 aromatase, a key enzyme that catalyzes the conversion of androgens to estrogens in vivo and affects the development of 2D:4D. Studying the association between six single-nucleotide polymorphisms (SNPs) in CYP19A1 and digit ratios in the normal population of China will provide some basis for the biological basis of digit ratio development and promote the practical application of digit ratios.

METHODS

In this study, six SNPs (rs10046, rs2414095, rs4646, rs4775936, rs749292 and rs936306) in CYP19A1 were tested in 1949 students (692 males and 1247 females) by TaqMan SNP genotyping in Ningxia, China. The digit ratios (right and left 2D:4D and right-left 2D:4D [D_r-l]) of all participants were collected using a photographic record.

RESULTS

The frequencies of the genotypes rs2414095 (P < 0.05), rs10046 (P < 0.01) and rs4775936 (P < 0.05) in the CYP19A1 gene and their allele frequencies were significantly different between the Hui and Han populations, and the frequency of the rs2414095 genotype (P < 0.05) was significantly different between males and females in Ningxia, China. There was a sex difference in right and left 2D:4D and in D_r-l. There was no significant association between the six SNPs of the CYP19A1 gene and right and left 2D:4D, although rs4775936 showed a lower 2D:4D ratio in allele T than in allele C, in both male and female subjects. For D_r-l we found that rs4775936 associated with increased D_r-l in females (t₇₈₇ = -2.441, P < 0.05).

CONCLUSIONS

We found the different frequencies of rs10046, rs2414095 and rs4775936 between Hui and Han populations in China. There was an association between rs4775936 and D_r-l. We discuss the implications of this association for links between D_r-l and rs4775936 and prenatal sex steroids and for susceptibility to breast cancer.

Elevated Aromatase (CYP19A1) Expression Is Associated with a Poor Survival of Patients with Estrogen Receptor Positive Breast Cancer

Genetic variants in CYP19A1, the gene encoding aromatase, have been reported to be associated with circulating estrogen concentrations, a key risk factor for breast cancer. The mechanism underlying this association is still unclear; it has been suggested that some of these variants may alter the expression and/or activity of aromatase. Here we analyzed the expression of intra-tumoral CYP19A1 messenger RNA (mRNA) and the genotypes of rs10046, a well-characterized single nucleotide polymorphism in CYP19A1, in 138 breast cancer patients and 15 breast cancer cell lines. The genotype TT was detected in 36 patients and six cell lines, genotype CT in 55 patients and five cell lines, and genotype CC in 28 patients and four cell lines. We found no evidence for a significant association of CYP19A1 levels with rs10046 genotypes, although expression tended to be higher in tumors and cell lines with the homozygous risk genotype TT. We also found no evidence for a significant association of rs10046 genotypes with breast cancer prognosis. In contrast, high CYP19A1 expression was highly significantly associated with a poor overall, disease-free, and metastasis-free survival in estrogen receptor-positive but not negative breast cancer patients. Moreover, CYP19A1 mRNA was significantly elevated in postmenopausal patients and in patients older than 50 years, and a trend towards a positive correlation with ER status and ESR1 mRNA expression was observed. These findings highlight the key role of aromatase in estrogen receptor-positive breast cancer biology.

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.

CYP19A1 polymorphisms and clinical outcomes in postmenopausal women with hormone receptor-positive breast cancer in the BIG 1-98 trial

To determine whether CYP19A1 polymorphisms are associated with abnormal activity of aromatase and with musculoskeletal and bone side effects of aromatase inhibitors. DNA was isolated from tumor specimens of 4861 postmenopausal women with hormone receptor-positive breast cancer enrolled in the BIG 1-98 trial to receive tamoxifen and/or letrozole for 5 years. Tumors were genotyped for six CYP19A1 polymorphisms using PCR-based methods. Associations with breast cancer-free interval (BCFI), distant recurrence-free interval (DRFI), musculoskeletal and bone adverse events (AEs) were assessed using Cox proportional hazards models. All statistical tests were two-sided. No association between the CYP19A1 genotypes and BCFI or DRFI was observed overall. A reduced risk of a breast cancer event for tamoxifen-treated patients with rs700518 variants was observed (BCFI CC/TC vs. TT: HR 0.53, 95 % CI 0.34-0.82, interaction P = 0.08), but not observed for letrozole-treated patients. There was an increased risk of musculoskeletal AEs for patients with rs700518 variants CC/TC versus TT (HR 1.22, 95 % CI 1.03-1.45, P = 0.02), regardless of treatment. Tamoxifen-treated patients with rs4646 variants had a reduced risk of bone AEs (AA/CA vs. CC: HR 0.76, 95 % CI 0.59-0.98), whereas an increase of minor allele (C) of rs10046 was associated with an increased risk of bone AEs (HR 1.28, 95 % CI 1.07-1.52). rs936308 variants were associated with a reduced risk of bone AEs in letrozole-treated patients (GG/GC vs. CC: HR 0.73, 95 % CI 0.54-0.99), different from in tamoxifen-treated patients (GG/GC vs. CC: HR 1.32, 95 % CI 0.92-1.90, interaction P = 0.01). CYP19A1 rs700518 variants showed associations with BCFI, DRFI, in tamoxifen treated patients and musculoskeletal AEs regardless of treatment. SNPs rs4646, rs10046, and rs936308 were associated with bone AEs.

Role of cytochrome P450 genes in breast cancer etiology and treatment: effects on estrogen biosynthesis, metabolism, and response to endocrine therapy

PURPOSE

The cytochrome P450 (CYP) genes are oxygenases involved in estrogen biosynthesis and metabolism, generation of DNA damaging procarcinogens, and response to anti-estrogen therapies. Since lifetime estrogen exposure is an established risk factor for breast cancer, determining the role of CYP genes in breast cancer etiology may provide critical information for understanding tumorigenesis and response to treatment.

METHODS

This review summarizes literature available in PubMed published between 1993 and 2013 that focuses on studies evaluating the effects of DNA variants in CYP genes on estrogen synthesis, metabolism, and generation of procarcinogens in addition to response to anti-estrogen therapies.

RESULTS

Evaluation of DNA variants in estrogen metabolism genes was largely inconclusive. Meta-analyses of data from CYP19A1 support an association between the number of (TTTA) n repeats in intron 4 and breast cancer risk, but the biological mechanism for this relationship is unknown. Associations between single nucleotide polymorphism in CYP1B1 and DNA damage caused by procarcinogenic estrogen metabolites were ambiguous. Variants in CYP2D6 are associated with altered metabolism tamoxifen; however, current data do not support widespread clinical testing. The effect of variants in CYP19A1 in response to aromatase inhibitors is also questionable.

CONCLUSION

Evaluation of DNA variants in CYP genes involved with estrogen metabolism or treatment response has been inconclusive, reflecting small samples sizes, tumor heterogeneity, and differences between populations. Better-powered studies that account for genetic backgrounds and tumor phenotypes are thus necessary.

Associations between CYP19A1 polymorphisms, Native American ancestry, and breast cancer risk and mortality: the Breast Cancer Health Disparities Study

The cytochrome p450 family 19 gene (CYP19A1) encodes for aromatase, which catalyzes the final step in estrogen biosynthesis and conversion of androgens to estrogens. Genetic variation in CYP19A1 is linked to higher circulating estrogen levels and increased aromatase expression. Using data from the Breast Cancer Health Disparities Study, a consortium of three population-based case-control studies in the United States (n = 3,030 non-Hispanic Whites; n = 2,893 Hispanic/Native Americans (H/NA) and Mexico (n = 1,810), we examined influence of 25 CYP19A1 tagging single-nucleotide polymorphisms (SNPs) on breast cancer risk and mortality, considering NA ancestry. Odds ratios (ORs) and 95 % confidence intervals (CIs) and hazard ratios estimated breast cancer risk and mortality. After multiple comparison adjustment, none of the SNPs were significantly associated with breast cancer risk or mortality. Two SNPs remained significantly associated with increased breast cancer risk in women of moderate to high NA ancestry (≥29 %): rs700518, ORGG 1.36, 95 % CI 1.11-1.67 and rs11856927, ORGG 1.35, 95 % CI 1.05-1.72. A significant interaction was observed for rs2470144 and menopausal status (p adj = 0.03); risk was increased in postmenopausal (ORAA 1.22, 95 % CI 1.05-1.14), but not premenopausal (ORAA 0.78, 95 % CI 0.64-0.95) women. The absence of an overall association with CYP19A1 and breast cancer risk is similar to previous literature. However, this analysis provides support that variation in CYP19A1 may influence breast cancer risk differently in women with moderate to high NA ancestry. Additional research is warranted to investigate the how variation in an estrogen-regulating gene contributes to racial/ethnic disparities in breast cancer.

Analysis of the rs10046 polymorphism of aromatase (CYP19) in premenopausal onset of human breast cancer

The CYP19 gene encodes aromatase, an enzyme catalyzing the conversion of androgens to estrogens. Studies analyzing associations between single nucleotide polymorphisms in CYP19 and breast cancer risk have shown inconsistent results. The rs10046 polymorphism is located in the 3′ untranslated region of the CYP19 gene, but the influence of this polymorphism on breast cancer risk is unclear. In this study, we investigated the impact of rs10046 SNP on breast cancer risk, age at onset and association with clinical characteristics in an Austrian population of 274 breast cancer patients and 253 controls. The results show that a significantly increased fraction of patients with the TT genotype of rs10046 develop breast cancer under the age of 50 (41.8% of TT patients, compared to 26.6% of C carriers; p = 0.018, Chi-square test). No rs10046 genotypes were significantly associated with increased breast cancer risk or patient characteristics other than age at onset. These results suggest that the rs10046 polymorphism in the CYP19 gene may have an effect on breast cancer susceptibility at an age under 50 in the investigated population.

Genetic variants in hormone-related genes and risk of breast cancer

Sex hormones play a key role in the development of breast cancer. Certain polymorphic variants (SNPs and repeat polymorphisms) in hormone-related genes are associated with sex hormone levels. However, the relationship observed between these genetic variants and breast cancer risk has been inconsistent. We conducted a case-control study nested within two prospective cohorts to assess the relationship between specific genetic variants in hormone-related genes and breast cancer risk. In total, 1164 cases and 2111 individually-matched controls were included in the study. We did not observe an association between potential functional genetic polymorphisms in the estrogen pathway, SHBG rs6259, ESR1 rs2234693, CYP19 rs10046 and rs4775936, and UGT1A1 rs8175347, or the progesterone pathway, PGR rs1042838, with the risk of breast cancer. Our results suggest that these genetic variants do not have a strong effect on breast cancer risk.

Associations between aromatase CYP19 rs10046 polymorphism and breast cancer risk: from a case-control to a meta-analysis of 20,098 subjects

Lifetime exposure to estrogen is a factor that plays an important role in the pathogenesis and progression of breast cancer. Genetic variants in genes of the biosynthesis and metabolism of estrogen have been associated with breast cancer risk. Among them, the CYP19 gene encodes for aromatase, the enzyme that catalyzes the conversion of androgens to estrogens. The rs10046 polymorphism on the CYP19 gene has been related to levels of circulating estradiol and to the estradiol/testosterone ratio. To date, epidemiological studies of rs10046 have been performed in different populations with contradictory results. In the present study, we have conducted a case-control analysis (522 cases and 1221 controls) in a Spanish population. Furthermore, we have performed a meta-analysis including 20,098 subjects (7,998 cases and 12,100 controls) to summarize the data available for rs10046 and breast cancer risk. An odds ratio (OR) with a 95% confidence interval (CI) was applied to assess the association. The results of our case-control study show an association between the carriers of at least one C allele (dominant model) and breast cancer risk (OR = 1.29, 95% CI 1.01-1.66, p-value = 0.038). The meta-analysis shows no significant association with breast cancer risk in any of the genetic models tested. The analysis by ethnic subgroups also failed to produce associations. The evaluation of heterogeneity, influence analysis, and publication bias confirms the reliability of the analysis. We can conclude that the rs10046 polymorphism on CYP19 by itself does not constitute breast cancer risk. We cannot, however, reject the possibility that it could contribute (interact), together with other genetic variants, to modify the circulating levels of estradiol.

Functional variable number of tandem repeats variation in the promoter of proto-oncogene PTTG1IP is associated with risk of estrogen receptor-positive breast cancer

Genetic polymorphisms in the signalling pathway of estrogen receptor (ER) could modify the risk of breast cancer. A variable number of tandem repeats (VNTR) polymorphism in the promoter of PTTG1IP, pituitary tumor transforming gene binding factor targeted by estrogen receptor α (ERα) in endocrine neoplasia, has been shown to be functional, but its relevance to cancer etiology was unknown. We investigated its association with breast cancer risk by genotyping in 658 patients and 866 controls and further analysed its differential interaction with ERα. We found nine types of alleles ranging from 2 to 9 and 11 repeats that form 29 distinct genotypes and 11 different biallelic repeat numbers. Subjects who carry the six-repeats allele (odds ratio [OR], 1.45; 95% confidence interval [CI], 1.17-1.79), long alleles (≥6 repeats) (OR, 1.55; 95% CI, 1.17-2.05) or a high dose of biallelic repeats (OR, 1.38; 95% CI, 1.07-1.77) were at significantly increased risk of cancer. In stratification analysis, these associations consistently manifested in ER-positive breast cancer: in ER positive, PR-positive subtype, genotypes with the six-repeats allele (OR, 1.42; 95% CI, 1.06-1.90), long alleles (OR, 1.77; 95% CI, 1.17-2.67) or a high dose of biallelic repeats (OR, 1.67; 95% CI, 1.19-2.33) were associated with cancer risk; in ER positive, HER2-negative subtype, they were susceptible factors with the ORs being 1.46 (95% CI, 1.06-2.02), 2.06 (95% CI, 1.28-3.32) and 1.85 (95% CI, 1.26-2.71), respectively. Furthermore, functional analysis revealed that an increase in the number of tandem repeats enhances the binding affinity of ERα. The present study provides the first epidemiological evidence that functional regulatory variants of PTTG1IP were associated with the risk of ER-positive breast cancer, further supporting its relevance as one proto-oncogene in breast cancer.

Polymorphisms of CYP19A1 and response to aromatase inhibitors in metastatic breast cancer patients

Single nucleotide polymorphisms (SNPs) in the gene encoding aromatase (CYP19A1) have been associated with differential benefit from letrozole treatment in metastatic breast cancer (mBC) patients, but validation is lacking. The aim was to investigate whether polymorphic variation of CYP19A1 and enzymes involved in estrogen and aromatase inhibitors (AIs) metabolism are associated with efficacy of AIs. 308 Women with estrogen-receptor-positive metastatic mBC treated with a third-generation AI were identified retrospectively. DNA was extracted from archival formalin-fixed paraffin embedded tumors and genotyped for 71 variants in 16 candidate genes, including CYP19A1. Time to treatment failure (TTF) was significantly improved in patients carrying the minor (T) allele of rs4775936 when compared to patients with the reference allele [HR = 0.79 per T allele (0.66-0.95); P = 0.012]. Patients with >7 TTTA repeats on either allele of CYP19A1 intron 4 had a lower risk of failure than those with a smaller repeat size [HR = 0.84 per >7 TTTA repeats (0.7-0.99); P = 0.04]. However, importantly in multivariate analysis, adjusting for the number of disease sites; disease-free interval from diagnosis to first recurrence, grade at diagnosis and first recurrence type neither variant maintained independent predictive significance. None of the 56 SNPs analyzed as an exploratory set showed significant association with TTF. Variants in CYP19A1 or other selected genes associated with AI metabolism were not independently associated with improved AI efficacy and emphasize the importance in pharmacogenetic studies of considering genetic biomarkers in the context of relevant prognostic factors.

Bone mineral density and prediction of non-osteoporotic disease

It is widely recognized that bone mineral density (BMD) is one of the best predictors of osteoporotic fractures. Sex hormone status clearly affects bone either directly or indirectly and a longer estrogen exposure appears to be a major determinant of postmenopausal BMD. Accordingly, several studies have led to the hypothesis that BMD might represent a marker of the accumulated lifetime exposure of estrogen and therefore be used as a predictor factor of the risk of other postmenopausal conditions such as breast cancer or cardiovascular diseases (CVD). With regard to the risk of breast cancer, there is evidence that different surrogate markers of lifetime exposure to estrogen are associated with an increased risk for breast cancer. Most of these markers are the opposite of those for the risk of fracture. Furthermore, several studies have also reported that women with higher BMD have an increased risk of breast cancer compared to women with lower BMD. On the other hand, postmenopausal women with osteoporosis are at increased risk for acute cardiovascular events and mortality independently of age and cardiovascular risk factors. BMD has been shown to inversely correlate with surrogate markers of CVD including aortic calcifications and atherosclerosis. The underlying mechanisms of such a relationship are not fully understood. Several plausible molecular links are serum lipids, pro-inflammatory cytokines or the RANK/RANK ligand/osteoprotegerin system. Interestingly, all of these factors are modulated by estrogens. It could thus be hypothesized that the intensity of postmenopausal estrogen deficiency could be also the common pathogenic factor between atherosclerosis and osteoporosis.

Serum estradiol should be monitored not only during the peri-menopausal period but also the post-menopausal period at the time of aromatase inhibitor administration

BACKGROUND

Aromatase inhibitor (AI) therapy is being extensively used as postoperative adjuvant therapy in patients with hormone receptor-positive postmenopausal breast cancer. On the other hand, it has been reported that ovarian function was restored when AI was administered to patients who had undergone chemical menopause with chemotherapy or tamoxifen. However, there have been no reports of comprehensive monitoring of estradiol (E2) in breast cancer patients with ordinary menopause who were being administered AI.

PATIENTS AND METHODS

Beginning in March 2008, regular monitoring of the serum levels of E2, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) was performed for 66 postmenopausal breast cancer patients who had been started on AI therapy. For this study, we chose anastrozole as the AI. The assays of those hormones were outsourced to a commercial clinical laboratory.

RESULTS

In 4 of the 66 patients the serum E2 level was decreased at 3 months but had then increased at 6 months, while in 2 other patients E2 was decreased at both 3 and 6 months but had increased at 9 months.

CONCLUSION

The results indicate that, in some breast cancer patients with ordinary menopause, E2 rebounds following AI therapy. In the future, E2 monitoring should be performed for a larger number of patients being administered AI therapy.

TRIAL REGISTRATION

Our trial registration number is 19-11-1211.