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

Influence of N-acetyltransferase 2 polymorphisms and clinical variables on liver function profile of tuberculosis patients

BACKGROUND

Single nucleotide polymorphisms (SNPs) in the N-acetyltransferase 2 (NAT2) gene as well as several other clinical factors can contribute to the elevation of liver function test values in tuberculosis (TB) patients receiving antitubercular therapy (ATT).

RESEARCH DESIGN AND METHODS

A prospective study involving dynamic monitoring of the liver function tests among 130 TB patients from baseline to 98 days post ATT initiation was undertaken to assess the influence of pharmacogenomic and clinical variables on the elevation of liver function test values. Genomic DNA was extracted from serum samples for the assessment of NAT2 SNPs. Further, within this study population, we conducted a case control study to identify the odds of developing ATT-induced drug-induced liver injury (DILI) based on NAT2 SNPs, genotype and phenotype, and clinical variables.

RESULTS

NAT2 slow acetylators had higher mean [90%CI] liver function test values for 8-28 days post ATT and higher odds of developing DILI (OR: 2.73, 90%CI: 1.05-7.09) than intermediate acetylators/rapid acetylators.

CONCLUSION

The current study findings provide evidence for closer monitoring among TB patients with specific NAT2 SNPs, genotype and phenotype, and clinical variables, particularly between the period of more than a week to one-month post ATT initiation for better treatment outcomes.

Progesterone Receptor Gene Polymorphisms and Breast Cancer Risk

The objective of this systematic review was to investigate the association between polymorphisms in the progesterone receptor gene (PGR) and breast cancer risk. A search of PubMed, Scopus, and Web of Science databases was performed in November 2021. Study characteristics, minor allele frequencies, genotype frequencies, and odds ratios were extracted. Forty studies met the eligibility criteria and included 75 032 cases and 89 425 controls. Of the 84 PGR polymorphisms reported, 7 variants were associated with breast cancer risk in at least 1 study. These polymorphisms included an Alu insertion (intron 7) and rs1042838 (Val660Leu), also known as PROGINS. Other variants found to be associated with breast cancer risk included rs3740753 (Ser344Thr), rs10895068 (+331G/A), rs590688 (intron 2), rs1824128 (intron 3), and rs10895054 (intron 6). Increased risk of breast cancer was associated with rs1042838 (Val660Leu) in 2 studies, rs1824128 (intron 3) in 1 study, and rs10895054 (intron 6) in 1 study. The variant rs3740753 (Ser344Thr) was associated with decreased risk of breast cancer in 1 study. Mixed results were reported for rs590688 (intron 2), rs10895068 (+331G/A), and the Alu insertion. In a pooled analysis, the Alu insertion, rs1042838 (Val660Leu), rs3740753 (Ser344Thr), and rs10895068 (+331G/A) were not associated with breast cancer risk. Factors reported to contribute to differences in breast cancer risk associated with PGR polymorphisms included age, ethnicity, obesity, and postmenopausal hormone therapy use. PGR polymorphisms may have a small contribution to breast cancer risk in certain populations, but this is not conclusive with studies finding no association in larger, mixed populations.

Association of the PROGINS PgR polymorphism with susceptibility to female reproductive cancer: A meta-analysis of 30 studies

Aims

The progesterone response of the nuclear progesterone receptor plays an important role in the female reproductive system. Changes in the function of the progesterone receptor gene may increase the risk of reproductive cancer. The present study performed a meta-analysis to examine whether the progesterone receptor gene PROGINS polymorphism was a susceptibility factor for female reproductive cancer.

Materials and methods

We searched the PubMed, Cochrane Library, Web of Science and EMBASE databases for literature on PROGINS polymorphisms and female reproductive cancer published before September 2020. We evaluated the risk using odds ratios [ORs] and 95% confidence intervals via fixed effects models and random-effects models, which were calculated for all five genetic models. We grouped the analyses by race, cancer, and HWE.

Results

Thirty studies comprised of 25405 controls and 19253 female reproductive cancer cases were included in this meta-analysis. We observed that the Alu insertion polymorphism and the V660L polymorphism were significantly associated with female reproductive cancer in the allele and dominant genetic models. The allele genetic model and (Alu-insertion polymorphism: OR = 1.22, 95% CI = 1.02–1.45; V660L polymorphism: OR = 1.02, 95% CI = 1.00–1.13) dominant genetic model (Alu-insertion polymorphism: OR = 1.27, 95% CI = 1.03–1.58; V660L polymorphism: OR = 1.10, 95% CI = 1.011.19) demonstrated a significantly increased risk of female reproductive cancer. A subgroup analysis according to ethnicity found that the Alu insertion was associated with female reproductive cancer incidence in white (Allele model: OR = 1.21, 95% CI = 1.00–1.45; Heterozygous model: OR = 3.44, 95% CI = 1.30–9.09) and Asian (Dominant model: OR = 3.12, 95% CI = 1.25–7.79) populations, but the association disappeared for African and mixed racial groups. However, the V660L polymorphism was significantly associated with female reproductive cancer in the African (Allele model: OR = 2.52, 95% CI = 1.14–5.56; Heterozygous model: OR = 2.83, 95% CI = 1.26–6.35) and mixed racial groups (Dominant model: OR = 1.28, 95% CI = 1.01–1.62). Subgroup analysis by cancer showed that the PROGINS polymorphism increased the risk of cancer in the allele model, dominant mode and heterozygous model, but the confidence interval for this result spanned 1 and was not statistically significant. This sensitivity was verified in studies with HWE greater than 0.5.

Conclusion

Our meta-analysis showed that the progesterone receptor gene Alu insertion and the V660L polymorphism contained in the PROGINS polymorphism were susceptibility factors for female reproductive cancer.

UGT1A1 Gene Polymorphism Contributes as a Risk Factor for Lung Cancer: A Pilot Study with Patients from the Amazon

Lung cancer is one of the most frequent neoplasms in the world. Because it is a complex disease, its formation occurs in several stages, stemming from interactions between environmental risk factors, such as smoking, and individual genetic susceptibility. Our objective was to investigate associations between a UGT1A1 gene polymorphism (rs8175347) and lung cancer risk in an Amazonian population. This is a pilot study, case-controlled study, which included 276 individuals with cancer and without cancer. The samples were analyzed for polymorphisms of the UGT1A1 gene (rs8175347) and genotyped in PCR, followed by fragment analysis in which we applied a previously developed set of informative ancestral markers. We used logistic regression to identify differences in allelic and genotypic frequencies between individuals. Individuals with the TA7 allele have an increased chance of developing lung adenocarcinoma (p = 0.035; OR: 2.57), as well as those with related genotypes of reduced or low enzymatic activity: TA6/7, TA5/7, and TA7/7 (p = 0.048; OR: 8.41). Individuals with homozygous TA7/7 have an increased chance of developing squamous cell carcinoma of the lung (p = 0.015; OR: 4.08). Polymorphism in the UGT1A1 gene (rs8175347) may contribute as a risk factor for adenocarcinoma and lung squamous cell carcinoma in the population of the Amazon region.

Estrogen Receptor 1 Gene (ESR1) rs2234693 Polymorphism and Breast Cancer Risk in Saudi Women

Objective:

The present study aimed to determine the role of ESR1 gene rs2234693 T/C polymorphism (PvuII) in the susceptibility to breast cancer and to assess the association of this polymorphism within presence or absence of estrogen, progesterone receptors, human epidermal growth factor receptor 2 (HER2) and with premenopausal and postmenopausal age in Saudi women.

Methods:

The study was a retrospective case-control study. In this study, 137 breast cancer and 98 normal breast paraffin embedded tissues were included. DNA was extracted and ESR1 gene rs2234693 T/C polymorphism was genotyped by PCR-RFLP. Genetic association tests were performed.

Results:

The results showed no significant difference in distribution of rs2234693 T/C alleles and genotypes frequencies. Odd ratios (95% CI) were 1.15 (0.8-1.66) and 1.06 (0.5-1.98) and p values were 0.51 and 0.87, respectively. The genotypes and alleles frequencies within different hormonal receptors groups and ages of menopause showed no signification association (odd ratios were less or close to 1 and p values > 0.05).

Conclusion:

ESR1 gene rs2234693 T/C polymorphism was not associated with susceptibility to breast cancer and different menopausal, hormone receptors, and HER2 status in breast cancer patients. Further analysis using larger sample size will be needed to assess the association of different polymorphisms within the gene and risk of breast cancer.

Circulating unmetabolized folic acid and 5-methyltetrahydrofolate and risk of breast cancer: a nested case-control study

BACKGROUND/OBJECTIVES

Folates found in natural foods are thought to protect against cancer. However, folic acid (FA), a synthetic form of folate used in supplements and fortified foods, may increase breast cancer risk if present in unmetabolized form (UMFA) in the circulation. This study examined the associations of serum UMFA and 5-methyltetrahydrofolate (5-mTHF), the predominant form of circulating folate, with breast cancer risk.

SUBJECTS/METHODS

We conducted a nested case-control study in a prospective cohort. In total, 553 cases of invasive breast cancer, diagnosed before mandatory FA fortification of grain in the US in 1998, were individually-matched to 1059 controls. Serum UMFA and 5-mTHF were measured using liquid chromatography-tandem mass spectrometry in stored serum samples, and 5-mTHF was corrected for storage degradation.

RESULTS

Serum UMFA was not associated with breast cancer risk: the percentage of women with detectable levels of UMFA was similar in cases and controls (18% and 20%, respectively; p = 0.46). Two tag-SNPs in the promoter region of the FA-metabolizing gene were also not associated with risk. There was a marginally significant inverse association of 5-mTHF_corrected with breast cancer risk (odds ratio for the highest vs. lowest quintile = 0.69, 95% CI = 0.49 to 0.97; p_trend = 0.08).

CONCLUSIONS

Circulating UMFA was not associated with breast cancer risk. These results apply to countries without mandatory FA food fortification. Studies are needed in countries with mandatory fortification, where levels of UMFA are much higher than in our study.

Drug-metabolizing enzymes: role in drug resistance in cancer

Although continuous researches are going on for the discovery of new chemotherapeutic agents, resistance to these anticancer agents has made it really difficult to reach the fruitful results. There are many causes for this resistance that are being studied by the researchers across the world, but still, success is far because there are several factors that are going along unattended or have been studied less. Drug-metabolizing enzymes (DMEs) are one of these factors, on which less study has been conducted. DMEs include Phase I and Phase II enzymes. Cytochrome P450s (CYPs) are major Phase I enzymes while glutathione-S-transferases (GSTs), UDP-glucuronosyltransferases (UGTs), dihydropyrimidine dehydrogenases are the major enzymes belonging to the Phase II enzymes. These enzymes play an important role in detoxification of the xenobiotics as well as the metabolism of drugs, depending upon the tissue in which they are expressed. When present in tumorous tissues, they cause resistance by metabolizing the drugs and rendering them inactive. In this review, the role of these various enzymes in anticancer drug metabolism and the possibilities for overcoming the resistance have been discussed.

The UDP-Glycosyltransferase (UGT) Superfamily: New Members, New Functions, and Novel Paradigms

UDP-glycosyltransferases (UGTs) catalyze the covalent addition of sugars to a broad range of lipophilic molecules. This biotransformation plays a critical role in elimination of a broad range of exogenous chemicals and by-products of endogenous metabolism, and also controls the levels and distribution of many endogenous signaling molecules. In mammals, the superfamily comprises four families: UGT1, UGT2, UGT3, and UGT8. UGT1 and UGT2 enzymes have important roles in pharmacology and toxicology including contributing to interindividual differences in drug disposition as well as to cancer risk. These UGTs are highly expressed in organs of detoxification (e.g., liver, kidney, intestine) and can be induced by pathways that sense demand for detoxification and for modulation of endobiotic signaling molecules. The functions of the UGT3 and UGT8 family enzymes have only been characterized relatively recently; these enzymes show different UDP-sugar preferences to that of UGT1 and UGT2 enzymes, and to date, their contributions to drug metabolism appear to be relatively minor. This review summarizes and provides critical analysis of the current state of research into all four families of UGT enzymes. Key areas discussed include the roles of UGTs in drug metabolism, cancer risk, and regulation of signaling, as well as the transcriptional and posttranscriptional control of UGT expression and function. The latter part of this review provides an in-depth analysis of the known and predicted functions of UGT3 and UGT8 enzymes, focused on their likely roles in modulation of levels of endogenous signaling pathways.

A New Genetic Risk Score to Predict the Outcome of Locally Advanced or Metastatic Breast Cancer Patients Treated With First-Line Exemestane: Results From a Prospective Study

INTRODUCTION

Approximately 50% of locally advanced or metastatic breast cancer (MBC) patients treated with first-line exemestane do not show objective response and currently there are no reliable biomarkers to predict the outcome of patients using this therapy. The constitutive genetic background might be responsible for differences in the outcome of exemestane-treated patients. We designed a prospective study to investigate the role of germ line polymorphisms as biomarkers of survival.

PATIENTS AND METHODS

Three hundred two locally advanced or MBC patients treated with first-line exemestane were genotyped for 74 germ line polymorphisms in 39 candidate genes involved in drug activity, hormone balance, DNA replication and repair, and cell signaling pathways. Associations with progression-free survival (PFS) and overall survival (OS) were tested with multivariate Cox regression. Bootstrap resampling was used as an internal assessment of results reproducibility.

RESULTS

Cytochrome P450 19A1-rs10046TC/CC, solute carrier organic anion transporter 1B1-rs4149056TT, adenosine triphosphate binding cassette subfamily G member 2-rs2046134GG, fibroblast growth factor receptor-4-rs351855TT, and X-ray repair cross complementing 3-rs861539TT were significantly associated with PFS and then combined into a risk score (0-1, 2, 3, or 4-6 risk points). Patients with the highest risk score (4-6 risk points) compared with ones with the lowest score (0-1 risk points) had a median PFS of 10 months versus 26.3 months (adjusted hazard ratio [AdjHR], 3.12 [95% confidence interval (CI), 2.18-4.48]; P < .001) and a median OS of 38.9 months versus 63.0 months (AdjHR, 2.41 [95% CI, 1.22-4.79], P = .012), respectively.

CONCLUSION

In this study we defined a score including 5 polymorphisms to stratify patients for PFS and OS. This score, if validated, might be translated to personalize locally advanced or MBC patient treatment and management.

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.

Progesterone Receptor (PGR) Gene Variants Associated with Breast Cancer and Associated Features: a Case-Control Study

Insofar as altered estrogen receptor-progesterone receptor (PR) expression contribute to breast cancer pathogenesis, previous studies examined the association of genetic variation in PR gene (PGR) with breast cancer, but with mixed outcome. We evaluated the association between PGR variants, and breast cancer and associated features. A retrospective case-control study involving 183 female breast cancer patients, and 222 control women. PGR genotyping was done by real-time PCR. Minor allele frequencies of rs1042838, rs590688, and rs10895068 PGR gene polymorphisms were significantly higher in breast cancer patients compared to controls. Patients carrying rs1042838 G/T, rs590688 C/C, and rs10895068 G/A genotypes had higher risk of breast cancer, while carriage of rs3740753 G/G genotype was associated with marginal reduction in breast cancer risk. In addition, carriage of rs1042839, rs3740753, and rs10895068 minor allele was associated with Her2 status, while rs3740753 and rs10895068 were associated with effective hormone replacement therapy. Furthermore, carriage of rs10895068 minor allele in breast cancer women were also associated with age at first pregnancy, hormone receptor (RH) status, and previous use of oral contraceptives. PGR haploview analysis documented moderate-strong linkage disequilibrium (non-random association of alleles at different loci) between 7 of the 8 tested PGR SNPs, thus allowing construction of 7-locus PGR haplotypes. Two haplotypes, ATGCCGA and GTGCCGA, both containing rs590688, were positively associated with breast cancer, thus assigning a breast cancer-susceptible nature to these haplotypes. PGR rs1042838, rs590688, and rs10895068, and ATGCCGA and GTGCCGA haplotypes are related with increased breast cancer susceptibility in Tunisian women.

Association of three single nucleotide polymorphisms of ESR1with breast cancer susceptibility: a meta-analysis

Expression of estrogen receptors is correlated with breast cancer risk, but inconsistent results have been reported. To clarify potential estrogen receptor (ESR)-related breast cancer risk, we analyzed genetic variants of ESR1 in association with breast cancer susceptibility. We performed a meta-analysis to investigate the association between rs2234693, rs1801132, and rs2046210 (single nucleotide polymorphisms of ESR1 ), and breast cancer risk. Our analysis included 44 case-control studies. For rs2234693, the CC genotype had a higher risk of breast cancer compared to the TT or CT genotype. For rs2046210, the AA, GA, or GA+ GG genotype had a much higher risk compared to the GG genotype. No significant association was found for the rs1801132 polymorphism with breast cancer risk. This meta-analysis demonstrates association between the rs2234693 and rs2046210 polymorphisms of ESR1 and breast cancer risk. The correlation strength between rs2234693 and breast cancer susceptibility differs in subgroup assessment by ethnicity.

Bisphenol-A glucuronidation in human liver and breast: identification of UDP-glucuronosyltransferases (UGTs) and influence of genetic polymorphisms

1. Bisphenol-A is a ubiquitous environmental contaminant that is primarily metabolized by glucuronidation and associated with various human diseases including breast cancer. Here we identified UDP-glucuronosyltransferases (UGTs) and genetic polymorphisms responsible for interindividual variability in bisphenol-A glucuronidation in human liver and breast. 2. Hepatic UGTs showing the highest bisphenol-A glucuronidation activity included UGT2B15 and UGT1A9. Relative activity factor normalization indicated that UGT2B15 contributes >80% of activity at bisphenol-A concentrations under 5 μM, while UGT1A9 contributes up to 50% of activity at higher concentrations. 3. Bisphenol-A glucuronidation by liver microsomes (46 donors) ranged from 0.25 to 4.3 nmoles/min/mg protein. Two-fold higher glucuronidation (p = 0.018) was observed in UGT1A9 *22/*22 livers compared with *1/*1 and *1/*22 livers. However, no associations were observed for UGT2B15*2 or UGT1A1*28 genotypes. 4. Bisphenol-A glucuronidation by breast microsomes (15 donors) ranged from <0.2 to 56 fmoles/min/mg protein. Breast mRNA expression of UGTs capable of glucuronidating bisphenol-A was highest for UGT1A1, followed by UGT2B4, UGT1A9, UGT1A10, UGT2B7 and UGT2B15. Bisphenol-A glucuronidation was over 10-fold lower in breast tissues with the UGT1A1*28 allele compared with tissues without this allele (p = 0.006). 5. UGT2B15 and UGT1A9 contribute to glucuronidation variability in liver, while UGT1A1 is important in breast.

Genotyping of Single Nucleotide Polymorphisms in DNA Isolated from Serum Using Sequenom MassARRAY Technology

Background

Large epidemiologic studies have the potential to make valuable contributions to the assessment of gene-environment interactions because they prospectively collected detailed exposure data. Some of these studies, however, have only serum or plasma samples as a low quantity source of DNA.

Methods

We examined whether DNA isolated from serum can be used to reliably and accurately genotype single nucleotide polymorphisms (SNPs) using Sequenom multiplex SNP genotyping technology. We genotyped 81 SNPs using samples from 158 participants in the NYU Women’s Health Study. Each participant had DNA from serum and at least one paired DNA sample isolated from a high quality source of DNA, i.e. clots and/or cell precipitates, for comparison.

Results

We observed that 60 of the 81 SNPs (74%) had high call frequencies (≥95%) using DNA from serum, only slightly lower than the 85% of SNPs with high call frequencies in DNA from clots or cell precipitates. Of the 57 SNPs with high call frequencies for serum, clot, and cell precipitate DNA, 54 (95%) had highly concordant (>98%) genotype calls across all three sample types. High purity was not a critical factor to successful genotyping.

Conclusions

Our results suggest that this multiplex SNP genotyping method can be used reliably on DNA from serum in large-scale epidemiologic studies.

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.

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.

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.

Inherited disorders of bilirubin transport and conjugation: new insights into molecular mechanisms and consequences

Inherited disorders of bilirubin metabolism might reduce bilirubin uptake by hepatocytes, bilirubin conjugation, or secretion of bilirubin into bile. Reductions in uptake could increase levels of unconjugated or conjugated bilirubin (Rotor syndrome). Defects in bilirubin conjugation could increase levels of unconjugated bilirubin; the effects can be benign and frequent (Gilbert syndrome) or rare but severe, increasing the risk of bilirubin encephalopathy (Crigler-Najjar syndrome). Impairment of bilirubin secretion leads to accumulation of conjugated bilirubin (Dubin-Johnson syndrome). We review the genetic causes and pathophysiology of disorders of bilirubin transport and conjugation as well as clinical and therapeutic aspects. We also discuss the possible mechanisms by which hyperbilirubinemia protects against cardiovascular disease and the metabolic syndrome and the effects of specific genetic variants on drug metabolism and cancer development.