A non-synonymous coding change in the CYP19A1 gene Arg264Cys (rs700519) does not affect circulating estradiol, bone structure or fracture

The CYP19A1 rs700519 Polymorphism and Breast Cancer Susceptibility in China: A Case-Control Study and Updated Meta-Analysis

Objective: Breast cancer (BC), the most prevalent cancer in women, has been associated with several genetic factors, including the CYP19A1 rs700519 polymorphism; however, the conclusions have not been consistent. This case-control study and meta-analysis aimed to further assess the relationship between the CYP19A1 rs700519 polymorphism and BC susceptibility. Materials and Methods: We conducted a case-control study to assess the relationship of the CYP19A1 rs700519 polymorphism with the risk and prognosis of BC. Subsequently, we performed a meta-analysis of the case-control studies. Results: In the case-control study, we found a significant negative relationship between the rs700519 AA genotype and risk (χ² = 7.503, p < 0.01) and disease-free survival rates (hazard rate = 0.400, 95% confidence interval [CI] = 0.181-0.883, p < 0.01) of patients with BC, especially in postmenopausal hormone receptor-positive (HR⁺) patients. Nine case-control studies were included in the meta-analysis. The CYP19A1 rs700519 polymorphism was significantly associated with BC susceptibility in the dominant (odds ratio [OR] = 0.95, 95% CI = 0.90-1.00, p = 0.05) and allelic models (OR = 0.84, 95% CI = 0.75-0.93, p < 0.01), but not in the recessive model. Sensitivity analysis revealed that the study results were stable, whereas the funnel plot revealed some publication bias. Conclusions: The CYP19A1 rs700519 polymorphism is related to breast tumorigenesis.

The Impact of Variants in Genes Associated with Estradiol Synthesis on Hormone Levels and Oocyte Retrieval in Patients Who Underwent Controlled Ovarian Hyperstimulation

AIMS

To correlate differences in estradiol levels in serum and follicular fluid with genetic variants and to determine if they play a role in the results following assisted reproductive technology (ART).

PATIENTS AND METHODS

A cross-sectional study was developed at the Ideia Fértil Institute of Reproductive Health. Two hundred two female patients were selected and underwent controlled ovarian hyperstimulation cycles. Patients for this study were chosen based on their male partners' infertility. Genotypes of selected variants of CYP19A1, CYP17A1, HSD17, and COMT were compared to the estradiol measurements from follicular fluid and serum, as well as to the number and maturation status of the oocytes retrieved.

RESULTS

Patients with the variant homozygous genotype AA of CYP19A1 (rs10046) showed increased serum concentrations of estradiol when compared to patients with other genotypes (p = 0.005). The same polymorphism effect was not observed in follicular fluid. This CYP19A1 variant did not affect the number of oocytes recovered nor their maturation level.

CONCLUSION

The CYP19A1 variant is associated with an estradiol imbalance in serum. Other pathways, however, may contribute to the formation of the final estradiol metabolite in follicular fluid as well as its impact on the oocyte maturation.

Variable aromatase inhibitor plasma concentrations do not correlate with circulating estrogen concentrations in post-menopausal breast cancer patients

PURPOSE

The aromatase inhibitors (AI) exemestane (EXE), letrozole (LET), and anastrozole suppress estrogen biosynthesis, and are effective treatments for estrogen receptor (ER)-positive breast cancer. Prior work suggests that anastrozole blood concentrations are associated with the magnitude of estrogen suppression. The objective of this study was to determine whether the magnitude of estrogen suppression, as determined by plasma estradiol (E2) concentrations, in EXE or LET treated patients is associated with plasma AI concentrations.

METHODS

Five hundred post-menopausal women with ER-positive breast cancer were enrolled in the prospective Exemestane and Letrozole Pharmacogenetic (ELPh) Study conducted by the COnsortium on BReast cancer phArmacogomics (COBRA) and randomly assigned to either drug. Estrogen concentrations were measured at baseline and after 3 months of AI treatment and drug concentrations were measured after 1 or 3 months. EXE or LET concentrations were compared with 3-month E2 concentration or the change from baseline to 3 months using several complementary statistical procedures.

RESULTS

Four-hundred patients with on-treatment E2 and AI concentrations were evaluable (EXE n = 200, LET n = 200). Thirty (7.6%) patients (EXE n = 13, LET n = 17) had 3-month E2 concentrations above the lower limit of quantification (LLOQ) (median: 4.75; range: 1.42-63.8 pg/mL). EXE and LET concentrations were not associated with on-treatment E2 concentrations or changes in E2 concentrations from baseline (all p > 0.05).

CONCLUSIONS

Steady-state plasma AI concentrations do not explain variability in E2 suppression in post-menopausal women receiving EXE or LET therapy, in contrast with prior evidence in anastrozole treated patients.

Impact of R264C and R264H polymorphisms in human aromatase function

The cytochrome P450 aromatase is involved in the last step of sex hormones biosynthesis by converting androgens into estrogens. The human enzyme is highly polymorphic and literature data correlate aromatase single nucleotide polymorphisms to the onset of pathologies such as breast cancer and neurodegenerative diseases. The aims of this study were i) to study the influence of the mutations R264C and R264H on the structure-function of the enzyme also upon phosphorylation by selected kinases and ii) to compare the activity of the variants to that of aromatase wild type in two different cell lines. Far-UV circular dichroism spectroscopy, thermal denaturation experiments and CO-binding assay showed that the two polymorphic variants are correctly folded. Steady-state kinetics experiments showed that rArom R264C and R264H exhibit a 1.5 and 3.4 folds lower catalytic efficiency, respectively, when compared to the wild type protein. Since R264 is part of the consensus motif of PKA and PKG1, phosphorylation experiments were performed to study the effect on aromatase function. Phosphorylation by PKA caused a decrease in activity by 36.2%, 49.3% and 27.9% in the wild type, R264C and R264H proteins respectively. Phosphorylation by PKG1 was also found to decrease the activity by 30.3%, 30.5% and 15.4% in the wild type, R264C and R264H proteins respectively. Experiments performed on the three full-length proteins expressed in human MCF-7 breast cancer cells and rat ST14A neuronal cells showed that, depending on the cell line used, the activity of the proteins is different, implicating different cellular mechanisms modulating aromatase activity. This work demonstrate that R264 polymorphism causes an intrinsic alteration of aromatase activity together with a different consensus for phosphorylation by different kinases, indicating that estrogen production can be different when such mutations are present. These findings are significant in understanding the onset and treatment of pathologies in which aromatase has been shown to be involved.

Genetic polymorphisms in estrogen-related genes and the risk of breast cancer among Han Chinese women

Exposure to high levels of estrogen is considered an important risk factor for susceptibility to breast cancer. Common polymorphisms in genes that affect estrogen levels may be associated with breast cancer risk, but no comprehensive study has been performed among Han Chinese women. In the present study, 32 single-nucleotide polymorphisms (SNPs) in estrogen-related genes were genotyped using the MassARRAY IPLEX platform in 1076 Han Chinese women. Genotypic and allelic frequencies were compared between case and control groups. Unconditional logistic regression was used to assess the effects of SNPs on breast cancer risk. Associations were also evaluated for breast cancer subtypes stratified by estrogen receptor (ER) and progesterone receptor (PR) status. Case-control analysis showed a significant relation between heterozygous genotypes of rs700519 and rs2069522 and breast cancer risk (OR = 0.723, 95% CI = 0.541-0.965, p = 0.028 and OR = 1.500, 95% CI = 1.078-2.087, p = 0.016, respectively). Subgroup comparisons revealed that rs2446405 and rs17268974 were related to ER status, and rs130021 was associated with PR status. Our findings suggest that rs700519 and rs2069522 are associated with susceptibility to breast cancer among the Han Chinese population and have a cumulative effect with three other identified SNPs. Further genetic and functional studies are needed to identify additional SNPs, and to elucidate the underlying molecular mechanisms.

DNA methylation within the I.4 promoter region correlates with CYPl19A1 gene expression in human ex vivo mature omental and subcutaneous adipocytes

Background

DNA methylation at specific CpG sites within gene promoter regions is known to regulate transcriptional activity in vitro. In human adipose tissue, basal transcription of the aromatase (CYP19A1) gene is driven primarily by the I.4 promoter however the role of DNA methylation in regulating expression in ex vivo mature adipocytes is unknown. This observational study reports the correlation of DNA methylation within the I.4 promoter region of human mature subcutaneous and omental adipocytes with aromatase expression and body composition measures.

Methods

Omental and subcutaneous adipose tissue were collected from 25 obese subjects undergoing bariatric surgery and the mature adipocyte fraction purified. DNA methylation status of 5 CpG sites within a 550 base pair region encompassing the transcription start site (TSS) of promoter I.4 was determined using pyrosequencing. Relative aromatase and I.4 promoter specific mRNA expression was determined by qRT-PCR and whole body DXA performed in 25 participants.

Results

Site-specific DNA methylation varied from 21 ± 10% to 81 ± 11%. In omental adipocytes percentage methylation at the I.4.1 and I.4.2 CpG sites, but not other nearby sites, was negatively correlated with relative aromatase mRNA expression (R = - 0.52, P = 0.017 and R = - 0.52, P = 0.015). In contrast subcutaneous adipocytes percentage DNA methylation at the I.4.3 and I.4.5 sites were positively correlated with relative aromatase mRNA expression (R = 0.47, P = 0.022 and R = 0.55, P = 0.004). In a small subset of patients DNA methylation at the I.4.5 site was also positively correlated with whole body lean mass, bone mineral content and density.

Conclusions

In conclusion in mature adipocytes, the primary source of estradiol after menopause, increasing DNA methylation was correlated with aromatase mRNA expression and thus estradiol biosynthesis. These findings support a tissue-specific epigenetic regulation of the basal promoter activity in mature adipocytes; the mechanisms influencing this regulation and its physiological role remain to be elucidated.

The sex-specific associations of the aromatase gene with Alzheimer's disease and its interaction with IL10 in the Epistasis Project

Epistasis between interleukin-10 (IL10) and aromatase gene polymorphisms has previously been reported to modify the risk of Alzheimer's disease (AD). However, although the main effects of aromatase variants suggest a sex-specific effect in AD, there has been insufficient power to detect sex-specific epistasis between these genes to date. Here we used the cohort of 1757 AD patients and 6294 controls in the Epistasis Project. We replicated the previously reported main effects of aromatase polymorphisms in AD risk in women, for example, adjusted odds ratio of disease for rs1065778 GG=1.22 (95% confidence interval: 1.01-1.48, P=0.03). We also confirmed a reported epistatic interaction between IL10 rs1800896 and aromatase (CYP19A1) rs1062033, again only in women: adjusted synergy factor=1.94 (1.16-3.25, 0.01). Aromatase, a rate-limiting enzyme in the synthesis of estrogens, is expressed in AD-relevant brain regions ,and is downregulated during the disease. IL-10 is an anti-inflammatory cytokine. Given that estrogens have neuroprotective and anti-inflammatory activities and regulate microglial cytokine production, epistasis is biologically plausible. Diminishing serum estrogen in postmenopausal women, coupled with suboptimal brain estrogen synthesis, may contribute to the inflammatory state, that is a pathological hallmark of AD.