A single-nucleotide polymorphism in the aromatase gene is associated with the efficacy of the aromatase inhibitor letrozole in advanced breast carcinoma

SNP of Aromatase Predict Long-term Survival and Aromatase Inhibitor Toxicity in Patients with Early Breast Cancer: A Biomarker Analysis of the GIM4 and GIM5 Trials

PURPOSE

In estrogen receptor-positive (ER+) breast cancer, single-nucleotide polymorphisms (SNP) in the aromatase gene might affect aromatase inhibitors (AI) metabolism and efficacy. Here, we assessed the impact of SNP on prognosis and toxicity of patients receiving adjuvant letrozole.

EXPERIMENTAL DESIGN

We enrolled 886 postmenopausal patients in the study. They were treated with letrozole for 2 to 5 years after taking tamoxifen for 2 to 6 years, continuing until they completed 5 to 10 years of therapy. Germline DNA was genotyped for SNP rs4646, rs10046, rs749292, and rs727479. Log-rank test and Cox model were used for disease-free survival (DFS) and overall survival (OS). Cumulative incidence (CI) of breast cancer metastasis was assessed through competing risk analysis, with contralateral breast cancer, second malignancies and non-breast cancer death as competing events. CI of skeletal and cardiovascular events were assessed using DFS events as competing events. Subdistribution HR (sHR) with 95% confidence intervals were calculated through Fine-Gray method.

RESULTS

No SNP was associated with DFS. Variants rs10046 [sHR 2.03, (1.04-2.94)], rs749292 [sHR 2.11, (1.12-3.94)], and rs727479 [sHR 2.62, (1.17-5.83)] were associated with breast cancer metastasis. Three groups were identified on the basis of the number of these variants (0, 1, >1). Variant-based groups were associated with breast cancer metastasis (10-year CI 2.5%, 7.6%, 10.7%, P = 0.035) and OS (10-year estimates 96.5%, 93.0%, 89.6%, P = 0.030). Co-occurrence of rs10046 and rs749292 was negatively associated with 10-year CI of skeletal events (3.2% vs. 10%, P = 0.033). A similar association emerged between rs727479 and cardiovascular events (0.3% vs. 2.1%, P = 0.026).

CONCLUSIONS

SNP of aromatase gene predict risk of metastasis and AI-related toxicity in ER+ early breast cancer, opening an opportunity for better treatment individualization.

Pharmacogenetics of Breast Cancer Treatments: A Sub-Saharan Africa Perspective

Breast cancer is the most frequent cause of cancer death in low- and middle-income countries, in particular among sub-Saharan African women, where response to available anticancer treatment therapy is often limited by the recurrent breast tumours and metastasis, ultimately resulting in decreased overall survival rate. This can also be attributed to African genomes that contain more variation than those from other parts of the world. The purpose of this review is to summarize published evidence on pharmacogenetic and pharmacokinetic aspects related to specific available treatments and the known genetic variabilities associated with metabolism and/or transport of breast cancer drugs, and treatment outcomes when possible. The emphasis is on the African genetic variation and focuses on the genes with the highest strength of evidence, with a close look on CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP3A4/5, CYP19A1, UGT1A4, UGT2B7, UGT2B15, SLC22A16, SLC38A7, FcγR, DPYD, ABCB1, and SULT1A1, which are the genes known to play major roles in the metabolism and/or elimination of the respective anti-breast cancer drugs given to the patients. The genetic variability of their metabolism could be associated with different metabolic phenotypes that may cause reduced patients’ adherence because of toxicity or sub-therapeutic doses. Finally, this knowledge enhances possible personalized treatment approaches, with the possibility of improving survival outcomes in patients with breast cancer.

Clinical application of aromatase inhibitors to treat male infertility

BACKGROUND

Infertility affects 15% of men and contributes to nearly half of all cases of infertility. Infertile men usually have impaired spermatogenesis, presenting as azoospermia or various degrees of asthenospermia and oligozoospermia. Spermatogenesis is a complex and coordinated process, which is under precise modulation by the hypothalamic-pituitary-gonadal (HPG) axis. An aberrant hormone profile, especially an imbalance between testosterone (T) and estradiol (E2), plays an essential role in male infertility. In the male, E2 is produced mainly from the conversion of T by the aromatase enzyme. Theoretically, reducing an abnormally elevated T:E2 ratio using aromatase inhibitors (AIs) could restore the balance between T and E2 and optimize the HPG axis to support spermatogenesis. For decades, AIs have been used to treat male infertility empirically. However, owing to the lack of large-scale randomized controlled studies and basic research, the treatment efficacy and safety of AIs in male infertility remain controversial. Therefore, there is a need to summarize the clinical trials and relevant basic research on the application of AIs in the treatment of male infertility.

OBJECTIVE AND RATIONALE

In this narrative review, we summarized the application of AIs in the treatment of male infertility, including the pharmacological mechanisms involved, clinical trials focused on patients with different types of infertility, factors affecting treatment efficacy and the side-effects.

SEARCH METHODS

A literature search was performed using MEDLINE/PubMed and EMBASE, focusing on publications in the past four decades concerning the use of AIs for treating male infertility. The search terms included AI, male infertility, letrozole, anastrozole, testolactone, azoospermia, oligozoospermia, aromatase polymorphisms, obesity and antiestrogens, in various combinations.

OUTCOMES

Clinical studies demonstrate that AIs, especially nonsteroidal letrozole and anastrozole, could significantly inhibit the production of E2 and its negative feedback on the HPG axis, resulting in increased T and FSH production as well as improved semen parameters in infertile men. Large-scale surveys suggest that obesity may result in symptoms of hypogonadism in both fertile and infertile males, such as decreased semen quality and attenuated sexual function, which can be improved by AIs treatment. Polymorphisms of the aromatase gene CYP19A1, including single nucleotide polymorphisms and tetranucleotide TTTA repeats polymorphism (TTTAn), also influence hormone profiles, semen quality and treatment efficacy of AIs in male hypogonadotropic hypogonadism and infertility. The side-effects of AIs in treating male infertility are various, but most are mild and well tolerated.

WIDER IMPLICATIONS

The application of AIs in treating male infertility has been off-label and empirical for decades. This narrative review has summarized the target patients, dose, treatment duration and side-effects of AIs. Polymorphisms of CYP19A1 that may affect AIs treatment efficacy were also summarized, but a full understanding of the mechanisms involved in AIs action requires further study.

The Prognostic Impact of Intratumoral Aryl Hydrocarbon Receptor in Primary Breast Cancer Depends on the Type of Endocrine Therapy: A Population-Based Cohort Study

The aryl hydrocarbon receptor (AhR) is a master regulator of multiple pathways involved in breast cancer, and influences the estrogen receptor alpha (ER) and aromatase/CYP19A1. The purpose of this study was to elucidate the interplay between intratumoral levels of AhR and aromatase, patient characteristics (including AhR and CYP19A1 genotypes), clinicopathological features, and prognosis in breast cancer patients receiving adjuvant treatments. A prospective cohort of 1116 patients with primary breast cancer in Sweden, included 2002-2012, was followed until June 30th 2019 (median 8.7 years). Tumor-specific AhR (n=920) and aromatase levels (n=816) were evaluated on tissue microarrays using immunohistochemistry. Associations between cytoplasmatic (AhRcyt) and nuclear (AhRnuc) AhR levels, intratumoral aromatase, clinicopathological features, and prognosis in different treatment groups were analyzed. Low AhRcyt levels (n=183) and positive intratumoral aromatase (n=69) were associated with estrogen receptor (ER)- status and more aggressive tumors. Genotypes were not associated with their respective protein levels. The functional AhR Arg554Lys GG genotype was associated with recurrence-free survival in switch-therapy (sequential tamoxifen/aromatase inhibitors (AI) or AI/tamoxifen) treated patients (HRadj 0.42; 95% CI 0.22-0.83). High AhRcyt levels were associated with longer recurrence-free survival during the first 10 years of follow-up among tamoxifen-only treated patients (HRadj 0.40; 95% CI 0.23-0.71) compared to low AhRcyt levels, whereas an almost inverse association was seen in patients with switch-therapy (P interaction=0.023). Intratumoral aromatase had little prognostic impact. These findings warrant confirmation in an independent cohort, preferably in a randomized clinical trial comparing different endocrine regimens. They might also guide the selection of breast cancer patients for clinical trials with selective AhR modulators.

Polymorphisms of T- cell leukemia 1A gene loci are not related to the development of adjuvant letrozole-induced adverse events in breast cancer

Letrozole, an aromatase inhibitor (AI), is the first-line adjuvant drug for treating hormone receptor-positive (HR+) breast cancer in postmenopausal women. However, harmful adverse events (AEs) and significant differences in drug response among individuals remain a significant problem in clinical application. Current evidence suggests that the observed individual variation in the treatment outcomes of AI is conferred by genetic variants. Hence, in this study, we examined the association of TCL1A gene polymorphisms with letrozole-induced AEs. The study subjects were postmenopausal HR+ breast cancer patients who were receiving adjuvant letrozole. Genomic DNA was isolated by a routine standard phenol-chloroform method. In total, 198 South Indian patients were genotyped for four single nucleotide polymorphisms (SNPs) in the TCL1A gene loci by the TaqMan allelic discrimination assay using the RT-PCR system. We used the odds ratio and 95% confidence interval to assess the genetic association. Musculoskeletal (MS) AEs and vasomotor symptoms (VMSs) are the most common side effects observed in the study cohort. Among 198 patients, 81 experienced musculoskeletal toxicity, reporting MS-AEs, 57 had VMSs, and 33 of them had both. The most frequently identified polymorphic variants in the patient series were rs11849538 (G), with an allele frequency of about 27.3%, followed by rs7158782-G (27.3%), rs7159713-G (25.8%), and rs2369049-G (22.5%). The genetic association analysis indicated no significant difference in the proportion of TCL1A gene variants between patients with and without AEs on either MS-AEs or VMSs. Though we observed high LD in all patient groups, the inferred haplotypes displayed a non-significant association with letrozole-induced specific AEs. However, the SNP functionality analysis by RegulomeDB provided a 2b rank score for rs7158782, suggesting a potential biological function. Our findings suggest that TCL1A gene polymorphisms may not play any role in the prediction of letrozole-induced AEs in South Indian HR+ breast cancer patients.

Association of CYP19A1 gene variations with adjuvant letrozole-induced adverse events in South Indian postmenopausal breast cancer cohort expressing hormone-receptor positivity

PURPOSE

Musculoskeletal adverse events (MS-AEs) and vasomotor symptoms (VMSs) are the major side-effects of newer generation non-steroidal aromatase inhibitor (AI), letrozole. Single-nucleotide polymorphisms (SNPs) in CYP19A1 gene coding for the enzyme aromatase are related to AI treatment-associated adverse drug reactions. Therefore, we aimed to determine whether SNPs in the CYP19A1 gene are associated with adjuvant letrozole-induced 'specific' AEs in postmenopausal hormone receptor-positive (HR+) breast cancer patients.

METHODS

Genomic DNA was isolated from 198 HR+ breast cancer patients by the phenol-chloroform method, and eleven SNPs in the CYP19A1 gene were genotyped by TaqMan genotyping assays on the qRT-PCR system. Toxicity was assessed according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0, and the data were analyzed using SPSS v19.0 and Haploview v4.2 statistical software.

RESULTS

Subjects carrying the genetic variants of CYP19A1 gene SNP rs700519 had significantly higher odds (OR 2.33; 95% CI [1.29-4.20], P = 0.0057) of MS-AEs under dominant statistical effect. The frequency of the two distinct haplotypes that include the variant allele 'T' at rs700519 locus, H5-GCTATCTGGCG (P = 0.042) and H11-GCTATTGCACG (P = 0.013) were significantly higher in patients with musculoskeletal toxicity than in those without MS-AEs and thus predisposing to MS-AEs. Similarly, H6-GCCAGCTGGCG (P = 0.037) haplotype exhibited higher frequencies in patients presented with VMSs. However, no such association was observed between CYP19A1 genotypes and VMSs.

CONCLUSIONS

To the best of our knowledge, this is the first study assessing the impact of CYP19A1 genetic variations with adjuvant letrozole treatment-associated AEs in Indian women. Genetic variations in the CYP19A1 gene is associated with letrozole-induced AEs and warrants further investigation in larger cohorts to validate this finding.

Association of CYP gene polymorphisms with breast cancer risk and prognostic factors in the Jordanian population

Background

Single nucleotide polymorphisms (SNPs) in several CYP genes have been associated with altered breast cancer (BC) risk in different populations. Despite this, there is a dearth of information on the roles of these SNPs in Jordanian BC patients. Therefore, this study aims to determine if there is any single nucleotide polymorphism (SNP) within CYP19A1, CYP2C19, CYP2C9, CYP1B1, CYP3A4, and CYP1A2 genes associated with BC in the Jordanian population. In addition, this work investigates the association between selected BC prognostic factors and variants of the aforementioned CYP candidate genes.

Methods

Blood samples were withdrawn from 221 BC patients and 218 healthy volunteers recruited from the Jordanian population. Genomic DNA was withdrawn and, after quantification and quality control, was genotyped using the Sequenom MassARRAY® system (iPLEX GOLD). Statistical analysis was then carried out to assess allelic and genotypic frequencies as well as genetic association between cases and controls.

Results

The CYP19A1 SNP rs7176005 (p < 0.0045) and the CYP1A2 SNP rs762551 (p = 0.004) were significantly associated with BC risk. However, no such association was found for the screened SNPs of the CYP2C9, CYP1B1, CYP2C19 and CYP3A4 genes. Regarding the prognostic factors of BC, several of the screened SNPs were associated with different pathological and clinical features.

Conclusions

Certain CYP genes, particularly CYP19A1 and CYP1A2, were associated with BC risk and development in the Jordanian population.

Bone and body composition response to testosterone therapy vary according to polymorphisms in the CYP19A1 gene

PURPOSE

To evaluate the influence of single nucleotide polymorphisms (SNPs) of CYP19A1 on the response and susceptibility to side effects from testosterone therapy. This is a prospective, single-arm study of men with low-morning serum testosterone (<10.68 nmol/l) administered testosterone cypionate 200 mg intramuscularly every 2 weeks for 18 months.

METHODS

We measured areal bone mineral density (aBMD) and body composition by dual energy X-ray absorptiometry, tibial volumetric BMD and geometry by peripheral quantitative computer tomography, bone turnover markers by enzyme-linked immunosorbent assay, testosterone, and estradiol by liquid-chromatography/mass-spectroscopy, genotyping by microarray, CYP19A1 expression by quantitative polymerase chain reaction, hematocrit and prostate-specific antigen (PSA).

RESULTS

We enrolled 105 men (40-74-years-old). SNPs rs1062033 and rs700518 were associated with significant differences in outcomes at 18 months. The GG genotype in rs1062033 had significant increase in whole body aBMD, but had significant decrease in tibial bone size compared to the CG and CC genotypes. Body composition analysis showed that the CC genotype of rs1062033, and the AA genotype of rs700518, had significant increase in total lean and appendicular lean mass compared to CG and GG, and AG and GG, respectively. The GG genotype of rs700518 had significant increase in PSA (GG = 105.8 ± 23.3% vs. AG + AA = 53.4 ± 11.3%, p = 0.046) while hematocrit changes were comparable among genotypes. CYP19A1 expression was highest in GG genotype in both SNPs.

CONCLUSIONS

For the first time, we demonstrated that CYP19A1 SNPs influence response to testosterone therapy in hypogonadal men, highlighting the importance of genetic profiling in therapeutics even for common clinical conditions.

Prognostic impact of genetic variants of CYP19A1 and UGT2B17 in a randomized trial for endocrine-responsive postmenopausal breast cancer

Polymorphisms of genes involved in estrogen synthesis have been linked to breast cancer risk, prognosis, and treatment response. We investigated the prognostic impact of a deletion spanning the entire UGT2B17 gene (UGT2B17*2) and genetic variants of the aromatase CYP19A1 and estrogen receptor α (ESR1) in 125 postmenopausal women with ER-positive breast cancer enrolled in a randomized pre-surgical trial. The UGT2B17*2 was estimated by copy number variation assays and the CYP19A1 rs10046/rs4646 and ESR1 rs2077647/rs2234693/rs9340799 by TaqMan allelic discrimination assays. Serum exemestane/17-hydroxy exemestane were determined by MS and estrone (E1)/estradiol (E2)/ by GC-MS/MS. The association of genetic polymorphisms with "any event" was assessed by the Cox proportional hazards models adjusted for confounders. The UGT2B17*2 was associated with higher levels of 17-hydroxy exemestane (P = 0.04) and better prognosis (HR = 0.45; 95% CI: 0.20-1.01; P = 0.05) compared with homozygote UGT2B17 wt. The CYP19A1 rs10046 A and rs4646 C alleles were associated with higher estrogen levels: rs10046 AA vs. AG/GG genotypes had median E1 of 35.9 vs. 27.4 pg/mL (P = 0.05) and E2 of 7.57 vs. 3.9 pg/mL (P < 0.004). After a median follow-up of 7 years, women carrying the "low estrogen" alleles rs10046 G and rs4646 A had a better prognosis compared with homozygote wt for both polymorphisms (HR = 0.40; 95% CI: 0.17-0.93; P = 0.03). Our analysis points to an impact of UGT2B17 and CYP19A1 in postmenopausal endocrine responsive breast cancer. Carriers of UGT2B17*2 and CYP19A1 low estrogen variants may have better prognosis, supporting studies addressing the role of these polymorphisms in optimizing endocrine therapy. Trial registration: http://www.isrctn.com/ISRCTN86894592.

Personalizing aromatase inhibitor therapy in patients with breast cancer

BACKGROUND

Aromatase inhibitors are the mainstay of therapy for patients with hormone receptor-positive breast cancer in both adjuvant and metastatic settings. Their use in clinical practice has been challenged by significant inter-individual variability in response and tolerability. Hence, the purpose of this paper is to provide a succinct review of the literature on the genetic factors contributing to this variability.

DESIGN

A systematic search in PUBMED was conducted to identify studies that investigated the association between germline polymorphisms and disposition, clinical response and toxicities of aromatase inhibitors, as well as those evaluating the implications of mutations in ESR1 on clinical response.

RESULTS

Polymorphisms in genes coding for phase I and phase II enzymes (pharmacokinetic genes) significantly modulated exposure to aromatase inhibitors; however, there is a paucity of data linking interindividual variability in drug exposure to clinical response. Furthermore, pharmacogenetic studies interrogating relationship between polymorphisms in CYP19A1 (the target site of aromatase inhibitors, i.e. a pharmacodynamic gene) and response yielded conflicting results. Acquired mutations in ESR1 receptors have been identified as the underlying mechanism of resistance to aromatase inhibitors, and likely predict drug response. Although some pharmacogenetic studies have implicated polymorphisms in CYP19A1 and ESR1 with drug-related side effects, the putative role of these genes in predicting toxicity warrants further validation.

CONCLUSION

Genetic polymorphisms in pharmacokinetic and pharmacodynamic genes appear to influence aromatase inhibitor disposition, response and/or toxicity; however, prospective interventional studies are needed to understand the application of genomics to personalize aromatase inhibitor therapy in breast cancer patients.

Rs1008805 polymorphism of CYP19A1 gene is associated with the efficacy of hormone therapy in stage I-II and operable stage III breast cancer

It has been hypothesized that single nucleotide polymorphisms in CYP19A1 gene may alter aromatase activity and circulating steroid hormone levels in females. Therefore, it is biologically reasonable that CYP19A1 rs1008805 (A/G) polymorphism may be associated with the clinical outcome of hormone therapy. Genotyping for the CYP19A1 rs1008805 polymorphism was performed for 287 females with hormone receptor (HR)-positive early breast cancer, and potential associations were evaluated between CYP19A1 rs1008805 genotypes and disease-free survival (DFS). Based on the analysis of the whole cohort, no significant differences were observed between rs1008805 genotypes and DFS. However, in postmenopausal females, rs1008805 variants were significantly associated with DFS (AA vs. AG vs. GG, 89.2 vs. 58.2 vs. 32.7 months; P=0.019). In addition, when the population was divided into two cohorts, females with the GG variant exhibited a significantly poorer DFS [GG vs. AA or AG, 32.7 vs. 70.6 months; hazard ratio (HR), 3.613; 95% confidence interval (CI), 1.380-9.457; P=0.005]. Furthermore, when adjusted for other patient features in multivariate analyses, GG genotype remained an independent prognostic marker for DFS (HR, 3.439; 95% CI, 1.251-9.456; P=0.017). However, there were no significant differences in DFS between patients harboring the minor allele and those with the homozygous common allele (AG or GG vs. AA, 52.4 vs. 89.2 months; HR, 1.288; 95% CI, 0.705-2.353; P=0.408). There were also no associations between rs1008805 polymorphism and DFS for premenopausal females. In conclusion, the homozygous minor allele (GG) of CYP19A1 rs1008805 was identified to be significantly associated with an inferior clinical outcome of hormone therapy in postmenopausal hormone receptor-positive patients with early breast cancer. If confirmed by further study, genotyping for CYP19A1 rs1008805 polymorphism may provide predictive information to improve the selection of endocrine treatment.

Pharmacogenetics and aromatase inhibitor induced side effects in breast cancer patients

This paper reviews genetic variations mainly related to the onset of adverse events during aromatase inhibitors in early breast cancer. Genetic variability could occur at different steps. The analysis included studies that involved breast cancer patients, treated with an aromatase inhibitor, genotyped for CYP19A1 and/or CYP17A1 and/or CYP27B1 and/or TCLA1, and/or RANK/RANKL/OPG and/or ESR1/ESR2, and assessed for toxicity profile. Twenty-two articles were included for the analysis. Three studies evaluated outcomes and adverse events; 19 studies assessed only side effects. Functional variations may be useful in predicting the onset of toxicities. The identification of polymorphisms at increased risk of toxicity may enable patient management. However, more data are needed to be applied in the individualization of treatment in daily practice.

The Association of CYP19A1 Variation with Circulating Estradiol and Aromatase Inhibitor Outcome: Can CYP19A1 Variants Be Used to Predict Treatment Efficacy?

After menopause, estradiol is primarily synthesized in peripheral tissues by the enzyme aromatase, encoded by CYP19A1. CYP19A1 variation associates with circulating estradiol in postmenopausal women and this variation is best represented by the intronic variant rs727479. This variation appears to have pleiotropic effects as it also associates with endometrial cancer risk. Indeed, estradiol plays an important role in the development of breast and endometrial cancer. Aromatase inhibitor (AI) drugs are used in the treatment of both diseases, however, response rates for AIs are low and there is currently no way to identify breast or endometrial cancer patients who are more likely to receive a clinical benefit. Multiple studies have proposed that genetic variation in CYP19A1 will have effects on AI efficacy: eight candidate variant studies of sample size greater than 50 describe associations between CYP19A1 variation and the outcome of patients treated with AIs. Nominally significant associations with patient outcome were reported for several variants, including rs727479. However, only an association between rs4646 and time to progression was replicated in an independent study. Moreover, rs4646 is also the only variant that has an association with patient outcome that passes a multiple testing threshold and this variant is in linkage disequilibrium with rs727479, supporting the hypothesis that associations with patient outcome may be driven through the effects on circulating estradiol. Despite this preliminary evidence, well phenotyped and comprehensively genotyped patient sets need to be studied before conclusions can be drawn about the effects of CYP19A1 variation on AI efficacy.

Germline genetic predictors of aromatase inhibitor concentrations, estrogen suppression and drug efficacy and toxicity in breast cancer patients

The third-generation aromatase inhibitors (AIs), anastrozole, letrozole and exemestane, are highly effective for the treatment of estrogen receptor-positive breast cancer in postmenopausal women. AIs inhibit the aromatase (CYP19A1)-mediated production of estrogens. Most patients taking AIs achieve undetectable blood estrogen concentrations resulting in drug efficacy with tolerable side effects. However, some patients have suboptimal outcomes, which may be due, in part, to inherited germline genetic variants. This review summarizes published germline genetic associations with AI treatment outcomes including systemic AI concentrations, estrogenic response to AIs, AI treatment efficacy and AI treatment toxicities. Significant associations are highlighted with commentary about prioritization for future validation to identify pharmacogenetic predictors of AI treatment outcomes that can be used to inform personalized treatment decisions in patients with estrogen receptor-positive breast cancer.

The rs4646 and rs12592697 Polymorphisms in CYP19A1 Are Associated with Disease Progression among Patients with Breast Cancer from Different Racial/Ethnic Backgrounds

Given the racial/ethnic disparities in breast cancer, we evaluated the association between CYP19A1 single nucleotide polymorphisms (SNPs) on disease progression in women with breast cancer from different racial/ethnic backgrounds. This is a cross-sectional analysis of data from 327 women with breast cancer in the Expanded Breast Cancer Registry program of the University of New Mexico. Stored DNA samples were analyzed for CYP19A1 SNPs using a custom designed microarray panel. Genotype-phenotype correlations were analyzed. Of the 384 SNPs, 2 were associated with clinically significant outcomes, the rs4646 and rs12592697. The T allele for the rs4646 was associated with advanced stage of the disease at the time of presentation (odds ratio [OR]:1.8, confidence intervals [CI]: 1.05–3.13, p < 0.05) and a more progressive disease (OR: 2.1 [CI: 1.1–4.0], p = 0.04). For the rs12592697, the variant T allele was more frequent in Hispanic women and associated with a more progressive disease (OR: 2.05 [CI: 1.0–4.0], p = 0.04). However, further analysis according to menopausal status showed that the association between these 2 SNPs with disease progression or the stage at diagnosis are confined only to postmenopausal women. The odds ratios of disease progression among postmenopausal women carrying the T allele for the rs4646 and rs12592697 are 3.05 (1.21, 7.74, p = 0.02) and 3.80 (1.24, 11.6, p = 0.02), respectively. Regardless, differences in disease progression among the different genotypes for both SNPs disappeared after adjustment for treatment. In summary, the rs4646 and the rs12592697 SNPs in CYP19A1 are associated with differences in disease progression in postmenopausal women. However, treatment appears to mitigate the differences in genetic risk.

Polymorphisms in ABCB1 and CYP19A1 genes affect anastrozole plasma concentrations and clinical outcomes in postmenopausal breast cancer patients

AIMS

Anastrozole, an aromatase inhibitor widely used in breast cancer, has recently been indicated to be a P-glycoprotein (ABCB1) substrate. We have aimed to determine whether ABCB1 single-nucleotide polymorphisms (SNPs) can affect anastrozole plasma concentrations in these patients. In addition, we assessed the impact of SNPs in CYP19A1 and TCL1A on the development of arthralgia and cancer recurrence in our series.

METHODS

This study included 110 postmenopausal women with hormone receptor-positive breast cancer. Anastrozole plasma levels were determined by a liquid chromatography-electrospray ionization-quadrupole-time-of-flight mass spectrometry system. Patients were genotyped for SNPs in the ABCB1, TCL1A and CYP19A1 genes to search for associations with pharmacokinetic and pharmacodynamics parameters using logistic regression models.

RESULTS

Anastrozole concentrations showed an almost nine-fold interindividual variability (mean 26.95 ± 11.91 ng ml^-1 ). The ABCB1 2677-TT genotype was associated with higher plasma levels (32.22 ± 12.82 vs. 25.86 ± 11.56 ng ml^-1 for GG/GT subjects; 95% confidence interval: -12.3 to -0.40), whilst the 3435-TT genotype showed a protective effect on the risk of arthralgia (odds ratio = 0.32 [0.11-0.89]; P = 0.029). The CYP19A1 rs1008805 GG genotype was strongly and inversely associated with arthralgia (odds ratio = 0.24 [0.09-0.65], P = 0.004); however, SNPs near the TCL1A gene were not linked to this adverse effect. None of the patients who had cancer recurrence harboured the CYP19A1 rs727479 AA genotype, which, in contrast, was present in 38% of patients who did not relapse (P for trend = 0.031).

CONCLUSION

Our findings indicate that variability in anastrozole plasma levels may be attributable to the status of the ABCB1 gene locus. Furthermore, genetic variants in CYP19A1 were associated with arthralgia and cancer recurrence in our patients.

Genetic variation in the human cytochrome P450 supergene family

OBJECTIVES

Single nucleotide variations (SNVs) in the cytochrome P450 (CYP) gene family are a primary cause of interindividual differences in therapeutic effects and adverse reactions to drugs. However, we still lack important information on the extent of CYP polymorphisms at the population level. Here, we developed a comprehensive data set of SNVs in all 57 human CYP genes by integrating data from two extensive population sequencing projects and analyzed the distribution of SNVs in different subpopulations.

MATERIALS AND METHODS

CYP genetic variants derived from the NHLBI and 1000 Genomes project were classified by variant type, frequency, and ethnic origins. The genetic variability of CYP genes was normalized on the basis of nonlinear regression and the total number of genetic variations was estimated by the derived formulas.

RESULTS

In total, we detected 6165 SNVs, of which many were novel. The vast majority (83.2%) of all SNVs in coding regions were very rare (minor allele frequency <0.1%). On the basis of the regression analysis, the total number of genetic variations in human CYP genes was calculated to be 3.4 × 10 and 4.8 × 10 for a population size of one million in Europeans and Africans, respectively.

CONCLUSION

Our results suggest that the variant spectrum of human CYP genes is extensive and only a fraction of SNVs has been characterized to date. Moreover, the multitude of very rare novel sequence variants indicates that the commonly used SNV platforms are not satisfactory for determining the true genotype, which is critical information for personalized treatment with drugs influenced by CYP polymorphisms.

Polymorphisms in drug-metabolizing enzymes and steady-state exemestane concentration in postmenopausal patients with breast cancer

Discovery of clinical and genetic predictors of exemestane pharmacokinetics was attempted in 246 post-menopausal patients with breast cancer enrolled on a prospective clinical study. A sample was collected two hours after exemestane dosing at a 1 or 3 month study visit to measure drug concentration. The primary hypothesis was that patients carrying the low-activity CYP3A4*22 (rs35599367) SNP would have greater exemestane concentration. Additional SNPs in genes relevant to exemestane metabolism (CYP1A1/2, CYP1B1, CYP3A4, CYP4A11, AKR1C3/4, AKR7A2) were screened in secondary analyses and adjusted for clinical covariates. CYP3A4*22 was associated with a 54% increase in exemestane concentration (p<0.01). Concentration was greater in patients who reported White race, had elevated aminotransferases, renal insufficiency, lower body mass index, and had not received chemotherapy (all p<0.05), and CYP3A4*22 maintained significance after adjustment for covariates (p<0.01). These genetic and clinical predictors of exemestane concentration may be useful for treatment individualization in patients with breast cancer.

Structural and functional characterization of aromatase, estrogen receptor, and their genes in endocrine-responsive and -resistant breast cancer cells

Aromatase and estrogen receptor α (ER) are two key proteins for the proliferation of endocrine-responsive and -resistant breast cancers. Aromatase is an enzyme involved in the conversion of androgen (such as testosterone) to estrogen (such as 17β-estradiol). It is also a very effective therapeutic target for the treatment of endocrine-responsive breast cancer. Comparing endocrine-responsive and -resistant breast cancer, aromatase protein levels do not change significantly. Aromatase activity; however, can be increased via PI3K/Akt/IGFR signaling pathways in endocrine resistant cells. The activity of aromatase has been reported to be modulated by phosphorylation. The ER is an important steroid nuclear receptor in the proliferation of both endocrine-responsive and -resistant cells. Although the mutation or amplification of ER can cause endocrine resistance, it is not commonly found. Some point mutations and translocation events have been characterized and shown to promote estrogen-independent growth. Phosphorylation by cross-talk with growth factor pathways is one of the main mechanisms for ligand-independent activation of ER. Taken together, both ER and aromatase are important in ER-dependent breast cancer and the development of endocrine resistance.

The implications of genetic variation for the pharmacokinetics and pharmacodynamics of aromatase inhibitors

INTRODUCTION

Breast cancer is the most common female cancer and remains a serious public health concern worldwide. Third-generation aromatase inhibitors (AIs) are widely used in postmenopausal women with estrogen receptor positive breast cancer. However, there is marked interindividual variability in terms of the efficacy and incidence of adverse events following treatment with AIs. Pharmacogenetics has the potential to predict clinical outcomes based on patients' genetic information, paving the way towards personalized treatment.

AREAS COVERED

This article reviews pharmacogenetic studies of AIs, including pharmacokinetic and pharmacodynamic aspects, highlighting those studies where the efficacy and adverse events of AIs have been examined using both candidate gene and genome-wide approaches.

EXPERT OPINION

Pharmacogenetics is a promising approach to develop personalized medicine with AIs. However, the application of pharmacogenetics to predict therapeutic efficacy and adverse events in breast cancer patients is still far from implementation in routine clinical practice. Large, comprehensive, multicenter studies that simultaneously evaluate multiple genes and pathways, including rare variants, are warranted in order to produce reliable and informative results. The ultimate aim is to develop clinically-relevant guidelines for breast cancer therapy.

Genetic polymorphism at Val80 (rs700518) of the CYP19A1 gene is associated with body composition changes in women on aromatase inhibitors for ER (+) breast cancer

OBJECTIVE

Polymorphisms in the CYP19A1 (aromatase) gene influence disease-free survival and bone loss in patients taking aromatase inhibitors (AIs) for estrogen receptor-positive (ER+) breast cancers. Because AI use results in severe estrogen deficiency that may lead to changes in body composition, the aim of this study was to determine the effect of the rs700518 polymorphism in the CYP19A1 gene on the changes in body composition among postmenopausal women who were treated with AIs for ER+ breast cancer.

PATIENTS AND METHODS

This was a 1-year prospective study of changes in body composition in postmenopausal women who were initiated on third-generation AIs for ER+ breast cancer. Body composition was measured by dual-energy absorptiometry at 6 and 12 months, serum estradiol by radioimmunoassay, and genotyping by a TaqMan single-nucleotide polymorphism allelic discrimination assay.

RESULTS

Eighty-two women could provide at least one follow-up body composition measurement. Women with the GG genotype for the rs700518 (G/A at Val80) developed a significant increase in truncal fat mass index (P=0.03) and a significant decrease in fat-free mass index (P=0.01) at 12 months relative to patients carrying the A allele (GA/AA). There was no significant difference in the changes in estradiol levels among the genotypes.

CONCLUSION

Patients with the GG genotype for the rs700518 polymorphism in the CYP19A1 gene are at risk for significant loss of fat-free mass and increase in truncal fat with AI therapy. Whether there are associated metabolic abnormalities and whether changes would persist with long-term AI therapy need to be confirmed in a larger study with a longer duration of follow-up.

Elastin: a possible genetic biomarker for more severe ligament injuries in elite soccer. A pilot study

BACKGROUND

The study of new genetic biomarkers in genes related to connective tissue repair and regeneration may help to identify individuals with greater predisposition to injury, who may benefit from targeted preventive measures, and those who require longer recovery time following a muscle, ligament or tendon injury. The present study investigated whether single nucleotide polymorphisms of the Elastin gene could be related to MCL injury.

METHODS

60 top class football players were studied to identify single nucleotide polymorphisms for the Elastin (ELN) gene using Allelic Discrimination analysis. Each player was followed for 7 seasons, and each MCL injury was noted.

RESULTS

Ligament injury rate, severity and recovery time are related to specific genotypes observed in the elastin gene, especially the ELN-AA (16 MCL) and the ELN-AG (3 MCL). Players with the ELN-GG genotype sustained no MCL injury during the 7 seasons of the study.

CONCLUSIONS

The identification of polymorphisms in the ELN gene may be used as a novel tool to better define an athlete's genotype, and help to plan training and rehabilitation programmes to prevent or minimize MCL ligament injuries, and optimize the therapeutic and rehabilitation process after soft tissue injuries, and manage the workloads during trainings and matches.

CYP19A1 Genetic Polymorphisms rs4646 and Osteoporosis in Patients Treated with Aromatase Inhibitor-Based Adjuvant Therapy

OBJECTIVE

Third-generation aromatase inhibitors (AI) are potent suppressors of aromatase activity. The aim of this study was to measure the incidence of adverse effects in breast cancer patients treated with AI-based adjuvant therapy and the relationship with the CYP19A1 genotypes.

MATERIALS AND METHODS

Forty-five postmenopausal breast cancer patients (46-85 yrs) in AI adjuvant treatment were genotyped for the rs4646 polymorphisms of CYP19A1 gene and three variations were identified. Toxicities were registered at each follow-up medical examination, and classified in accord with the Common Terminology Criteria for Adverse Events.

RESULTS

Twenty-four (53.3%) patients presented the GG genotype; 19 (42.2%) the GT, and 2 (4.4%) the TT. The AI treatment was Anastrazole for 35 patients (77.8%) and Letrozole for the others (n=10; 22.2%). Osteoporosis was significantly associated with the GG genotype (p=0.001). Treatment discontinuation (TD) was observed in 6 cases (13.3%). The only parameter able to predict TD was the appearance of severe arthralgia/myalgia (Odds Ratio, OR=23.75; p=0.009), when adjusted for age and AI treatment.

CONCLUSION

Our results suggest that CYP19A1 polymorphic variants may influence susceptibility to develop AI-related side effects. Further prospective studies are needed to confirm the role of the aromatase gene (CYP19A1) polymorphisms in predicting adverse effects to AI-based therapy.

Associations between genetic variants and the effect of letrozole and exemestane on bone mass and bone turnover

Adjuvant therapy for hormone receptor (HR) positive postmenopausal breast cancer patients includes aromatase inhibitors (AI). While both the non-steroidal AI letrozole and the steroidal AI exemestane decrease serum estrogen concentrations, there is evidence that exemestane may be less detrimental to bone. We hypothesized that single nucleotide polymorphisms (SNP) predict effects of AIs on bone turnover. Early stage HR-positive breast cancer patients were enrolled in a randomized trial of exemestane versus letrozole. Effects of AI on bone mineral density (BMD) and bone turnover markers (BTM), and associations between SNPs in 24 candidate genes and changes in BMD or BTM were determined. Of the 503 enrolled patients, paired BMD data were available for 123 and 101 patients treated with letrozole and exemestane, respectively, and paired BTM data were available for 175 and 173 patients, respectively. The mean change in lumbar spine BMD was significantly greater for letrozole-treated (-3.2 %) compared to exemestane-treated patients (-1.0 %) (p = 0.0016). Urine N-telopeptide was significantly increased in patients treated with exemestane (p = 0.001) but not letrozole. Two SNPs (rs4870061 and rs9322335) in ESR1 and one SNP (rs10140457) in ESR2 were associated with decreased BMD in letrozole-treated patients. In the exemestane-treated patients, SNPs in ESR1 (Rs2813543) and CYP19A1 (Rs6493497) were associated with decreased bone density. Exemestane had a less negative impact on bone density compared to letrozole, and the effects of AI therapy on bone may be impacted by genetic variants in the ER pathway.

Predictive markers in elderly patients with estrogen receptor-positive breast cancer treated with aromatase inhibitors: an array-based pharmacogenetic study

So far, no reliable predictive clinicopathological markers of response to aromatase inhibitors (AIs) have been identified, and little is known regarding the role played by host genetics. To identify constitutive predictive markers, an array-based association study was performed in a cohort of 55 elderly hormone-dependent breast cancer (BC) patients treated with third-generation AIs. The array used in this study interrogates variants in 225 drug metabolism and disposition genes with documented functional significance. Six variants emerged as associated with response to AIs: three located in ABCG1, UGT2A1, SLCO3A1 with a good response, two in SLCO3A1 and one in ABCC4 with a poor response. Variants in the AI target CYP19A1 resulted associated with a favourable response only as haplotype; haplotypes with increased response association were also detected for ABCG1 and SLCO3A1. These results highlight the relevance of host genetics in the response to AIs and represent a first step toward precision medicine for elderly BC patients.

A potentially functional variant in the serotonin transporter gene is associated with premenopausal and perimenopausal hot flashes

OBJECTIVE

An increase in the use of selective serotonin reuptake inhibitors (SSRIs) and/or serotonin-norepinephrine reuptake inhibitors (SNRIs) to relieve menopausal hot flashes (HFs) has been observed recently. However, response to them has been heterogeneous. We hypothesized that this heterogeneity might be partially attributed to genetic variations in genes encoding the serotonin and/or norepinephrine transporters (SLC6A4 and SLC6A2). As a first step in testing the role of genetics in response to SSRIs/SNRIs, we examined the association between HFs and genetic variants within these two genes.

METHODS

We tested 29 haplotype-tagging single nucleotide polymorphisms within SLC6A4 and SLC6A2 for their association with HFs separately for European-American (396 cases and 392 controls) and African-American (125 cases and 81 controls) premenopausal and perimenopausal women.

RESULTS

We found that the minor allele of SLC6A4_rs11080121 was associated with protection against HFs (odds ratio, 0.75; 95% CI, 0.60-0.94) only in European-American women. Bioinformatics analyses indicated that rs11080121 is fully correlated with rs1042173 in the 3' untranslated region of SLC6A4. The minor allele of rs1042173 seems to disrupt a conserved binding site for hsa-miR-590-3p microRNA.

CONCLUSIONS

Disruption of a microRNA binding site leads to higher expression of SLC6A4, higher expression of SLC6A4 leads to depletion of serotonin in synaptic clefts, and depletion of serotonin triggers the presynaptic autoreceptor feedback mechanism to produce more serotonin, which is protective against HFs. This is the first study to test the association between HFs in both European-American and African-American premenopausal and perimenopausal women and genetic variants in two neurotransmitter transporter genes, SLC6A2 and SLC6A4. This information can be used in tailoring the pharmaceutical use of SSRIs/SNRIs for HF relief.

Actionable pharmacogenetic markers for prediction and prognosis in breast cancer

Breast cancer is a heterogeneous disease that necessitates proper patient classification to direct surgery, pharmacotherapy, and radiotherapy. Despite patients within the same subgroup receiving similar pharmacotherapy, substantial variation in clinical outcomes is observed. Pharmacogenetic variations with direct effect on pharmacokinetics and pharmacodynamics play a central role in clinical outcomes. Pharmacogenetic markers associated with clinical outcome are known as biomarkers. They are termed prognostic biomarkers when their presence is associated with a specific clinical outcome. If the presence of such biomarkers guides treatment, they are termed predictive biomarkers. A number of pharmacogenetic markers have been described in relation to breast cancer pharmacotherapy both in the adjuvant and neoadjuvant setting. CYP2D6 allelic variants produce variable rates of tamoxifen metabolism and are associated with survival outcomes. Other biomarkers have been described in relation to other forms of endocrine therapy and trastuzumab. In neoadjuvant and adjuvant breast cancer chemotherapy, specific biomarkers were correlated with clinical outcomes and risk of drug toxicity. This review highlights key biomarkers in breast cancer pharmacotherapy with the potential of translating such study outcomes into clinical practice.

Influence of CYP19A1 polymorphisms on the treatment of breast cancer with aromatase inhibitors: a systematic review and meta-analysis

BACKGROUND

Many clinical trials have shown the efficacy of aromatase inhibitors (AIs) in the management of breast cancer (BC). There is growing evidence that CYP19A1 single-nucleotide polymorphisms (SNPs) are associated with clinical response (CR) and adverse effects (AEs) among BC patients treated with AIs. The aim of this study was to analyze the association between CYP19A1 polymorphisms and AI treatment in BC patients.

METHODS

A systematic review was performed in MEDLINE, EMBASE, and LILACS. A meta-analysis was conducted to compare the association between CYP19A1 variants and treatment response among BC patients.

RESULTS

A total of 12 studies were included in the final analysis. There was significant variation among the populations studied and the SNPs and outcomes investigated. A meta-analysis was only possible for the evaluation of SNP rs4646 vs. the wild-type variant with respect to time to progression (TTP) among metastatic BC patients treated with AI. TTP was significantly increased in patients with the rs4646 variant compared with the wild-type gene (hazard ratio (HR) = 0.51 [95 % confidence interval (CI), 0.33-0.78], P = 0.002). Seven studies analyzed the association between AEs with different polymorphisms of CYP19A1. Although there was a statistically significant association with musculoskeletal adverse events (rs934635, rs60271534, rs700518rs, and haplotype M_3_5) and with vasomotor symptoms (rs934635, rs1694189, rs7176005, and haplotype M_5_3) in individual studies, similar associations were not observed in further studies. No statistically significant association between musculoskeletal AEs and SNPs rs4646, rs10046, rs727479, and rs1062033 was found.

CONCLUSIONS

These findings suggest that the presence of the rs4646 variant may be a predictive factor of the benefit of AI treatment for BC. The effects of CYP19A1 polymorphisms on clinical outcomes were most often detected in individual studies, suggesting that longer-term studies will better clarify these associations. Additional studies are needed to clarify the predictive value of other SNPs and whether CYP19A1 genotyping should be used to guide AI treatment.

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.

The CYP19 RS4646 polymorphism IS related to the prognosis of stage I-II and operable stage III breast cancer

Purpose

Aromatase, encoded by the CYP19 gene, catalyzes the final step of the conversion of androgens to estrogens. Given the critical role of CYP19 in estrogen synthesis, the potential influence of CYP19 rs4646 polymorphism on breast cancer survival, deserves further study.

Methods

Genotyping for CYP19 rs4646 variants was performed on 406 Chinese women with stage I–II and operable stage III breast cancer. Associations were evaluated between CYP19 rs4646 genotypes and disease-free survival (DFS).

Results

In premenopausal patients, women who are homozygous for the minor allele (AA) have a longer DFS compared with those carrying the major allele (CC or AC) (87 months versus 48.7 months; Hazard ratio (HR) = 0.56, 95 % CI = 0.318-0.985, P = 0.041). These differences were further demonstrated by a multivariate analysis (HR = 0.456, 95 % CI = 0.249-0.836, P = 0.011). Conversely, the same variant (AA) was estimated to be associated with a poorer DFS in postmenopausal women (AA versus AC or CC: 13.7 months versus 56.3 months; HR = 2.758, 95 % CI = 1.432-5.313, P = 0.002). Furthermore, the differences were confirmed by the COX proportional hazards model (HR = 2.983, 95% CI =1.494-5.955, P = 0.002).

Conclusions

The present study indicates that CYP19 rs4646 polymorphism is related to DFS in early breast cancer and that the prognosis index of the homozygous for the minor allele (AA) may depend on menopause status. The findings are novel, if confirmed, rs4646 genotypes may provide useful information for routine management in breast cancer.

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.

Polymorphic genetic variations of cytochrome P450 19A1 and T-cell leukemia 1A genes in the Tamil population

Aromatase inhibitors (AIs) are anti-neoplastic drugs widely used for the treatment of endocrine responsive breast carcinoma in postmenopausal women. Drug disposition, efficacy and tolerability of these agents are influenced by germ-line polymorphisms in the sequence of the genes encoding CYP19A1 and TCL1A proteins. In the current work, we aimed to determine the haplotype structures, linkage disequilibrium (LD) patterns, and allele and genotype frequency distribution of pharmacologically important variants from two genes (CYP19A1 and TCL1A) in Tamil population and assessed their ethnic differences. DNA derived from peripheral leukocytes of 111 healthy subjects were genotyped for 15 pharmacogenetic variants by real time thermocycler through allelic discrimination method using TaqMan 5' nuclease genotyping assay. The polymorphic variant allele frequencies of CYP19A1 were 42.3% (rs4646, T), 18% (rs10046, T), 36% (rs700519, T), 16.7% (rs700518, G), 26.1% (rs727479, G), 18% (rs4775936, T), 32% (rs10459592, G), 15.3% (rs1062033, C), 33.8% (rs749292, A), 40.1% (rs6493497, T) and 40.1% (rs7176005, G). TCL1A gene allele frequencies were 26.1% (rs7158782, G), 27% (rs7159713, G), 21.2% (rs2369049, G) and 27.5% (rs11849538, G). Comparing our data across the 5 HapMap populations (CEU, GIH, HCB, JPT and YRI) huge inter-ethnic differences were exhibited in the variant allele frequencies, LD patterns and haplotype blocks. Our results emphasize the importance of normative frequency documentation and will offer significant clinical relevance in personalizing AIs therapy.

Germline variants in the CYP19A1 gene are related to specific adverse events in aromatase inhibitor users: a substudy of Dutch patients in the TEAM trial

Musculoskeletal adverse events (MSAEs) and vasomotor symptoms (VMSs) are known side-effects of aromatase inhibitors, and may be related to genetic variations of the aromatase gene (CYP19A1). We investigated the relationship between these specific AEs and single nucleotide polymorphisms (SNPs) in the CYP19A1 gene in postmenopausal, hormone receptor-positive early breast cancer (BC) patients treated with adjuvant exemestane for 5 years. Dutch patients who were randomized to receive 5 years of exemestane in the Tamoxifen Exemestane Adjuvant Multinational (TEAM) trial were included. A tagging-SNP approach was performed, covering 80 % of variations of the CYP19A1 gene with 30 SNPs. Logistic regression analyses were used to assess the risk of reporting VMSs or MSAEs in relation to genotypes within selected SNPs. Of 737 included patients, 281 patients reported at least one MSAE (n = 210) or VMS (n = 163). Homozygous AA genotype of rs934635 was associated with a significantly higher odds of MSAEs (multivariate odds ratio (OR) 4.66, p = 0.008) and VMSs (multivariate OR 2.78, p = 0.044). Regarding both rs1694189 and rs7176005, the homozygous variant genotypes (TT) were associated with a higher odds of VMSs, but not MSAEs (OR 1.758, p = 0.025 and OR 6.361, p = 0.021, respectively). Our exploratory analysis demonstrated that some CYP19A1 gene variations may be associated with MSAEs and/or VMSs. Specifically, patients with the homozygous variant rs934635 genotype reported more MSAEs and VMSs. Although further confirmatory studies are warranted, genomic profiling can help identify patients at an increased risk of reporting these specific AEs, potentiating further personalized BC treatment.

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.

CYP19 genetic polymorphism haplotype AASA is associated with a poor prognosis in premenopausal women with lymph node-negative, hormone receptor-positive breast cancer

Given the critical role of CYP19 in estrogen synthesis, we investigated the influence of CYP19 gene polymorphisms on the clinical outcome of lymph node- (LN-) negative, hormone receptor- (HR-) positive early breast cancers. Genotyping for the CYP19 polymorphisms rs4646 (A/C), rs1065779 (A/C), CYP19 (TTTA)n (short allele/long (S/L) allele using the 7 TTTA repeat polymorphism as the cut-off), and rs1870050 (A/C) was performed on 296 patients with LN-negative, HR-positive breast cancers. All patients received adjuvant hormonal therapy. Associations were examined between these 4 genotypes and 6 common haplotypes of CYP19 and distant disease-free survival (DDFS), disease-free survival (DFS), and overall survival (OS). Patients were divided into the 6 subhaplotypes of CCLA (41.1%), AASA (17.1%), CASA (11.9%), CCLC (8.9%), CCSA (7.5%), AASC (8.9%), and others (4.6%). In premenopausal patients, haplotype AASA was significantly associated with a poor DDFS (adjusted hazard ratio (aHR), 3.3; P = 0.001), DFS (aHR, 2.5; P = 0.0008), and OS (aHR, 2.9; P = 0.0004) after adjusting for age, tumor size, tumor grade, estrogen receptor status, progesterone receptor status, chemotherapy, pathology, adjuvant hormone therapy, menopausal status, and radiotherapy. Furthermore, haplotype AASA remained a negative prognostic factor for premenopausal patients receiving adjuvant chemotherapy in terms of DDFS (aHR, 4.5; P = 0.0005), DFS (HR, 3.2; P = 0.003), and OS (HR, 6.4; P = 0.0009). However, in postmenopausal patients, haplotype AASA was not associated with a poor prognosis, whereas the AASC haplotype was significantly associated with a poor DFS (aHR, 3.1; P = 0.03) and OS (aHR, 4.4; P = 0.01). Our results indicate that, in patients with LN-negative, HR-positive breast cancers, genetic polymorphism haplotype AASA is associated with poor survival of premenopausal women but does not affect survival of postmenopausal women.

Impact of metabolizing enzymes on drug response of endocrine therapy in breast cancer

Estrogen-receptor positive breast cancer accounts for 75% of diagnosed breast cancers worldwide. There are currently two major options for adjuvant treatment: tamoxifen and aromatase inhibitors. Variability in metabolizing enzymes determines their pharmacokinetic profile, possibly affecting treatment response. Therefore, prediction of therapy outcome based on genotypes would enable a more personalized medicine approach, providing optimal therapy for each patient. In this review, the authors will discuss the current evidence on the most important metabolizing enzymes in endocrine therapy, with a special focus on CYP2D6 and its role in tamoxifen metabolism.

A polymorphism at the 3'-UTR region of the aromatase gene is associated with the efficacy of the aromatase inhibitor, anastrozole, in metastatic breast carcinoma

Estrogen-related genes and the fat mass and obesity-associated (FTO) gene play a critical role in estrogen metabolism, and those polymorphisms are associated with a poor prognosis in breast cancer. However, little is known about the association between these polymorphisms and the efficacy of anastrozole. The aim was to investigate the impact of the genetic polymorphisms, CYP19A1, 17-β-HSD-1 and FTO, on the response to anastrozole in metastatic breast carcinoma (MBC) and to evaluate the impact of those polymorphisms on various clinicopathologic features. Two-hundred seventy-two women with hormone receptor-positive MBC treated with anastrozole were identified retrospectively. DNA was extracted from peripheral blood and genotyped for five variants in three candidate genes. Time to progression was improved in patients carrying the variant alleles of rs4646 when compared to patients with the wild-type allele (16.40 months versus 13.52 months; p = 0.049). The rs4646 variant alleles were significantly associated with longer overall survival (37.3 months versus 31.6 months; p = 0.007). This relationship was not observed with the rs10046, rs2830, rs9926298 and rs9939609 polymorphisms. The findings of this study indicate that rs4646 polymorphism in the CYP19A1 gene may serve as a prognostic maker of the response to anastrozole in patients with MBC who are treated with anastrozole.

Impact of aromatase genetic variation on hormone levels and global outcome after severe TBI

Although experimental traumatic brain injury (TBI) studies support estradiol as a neuroprotectant and potent stimulator of neuroplasticity, clinical studies suggest a negative association between endogenous estradiol profiles and mortality/poor outcomes. However, no studies have evaluated associations with cerebral spinal fluid (CSF) hormone profiles and aromatase gene (cytochrome P450 [CYP]19A1) variability on clinical TBI outcomes. We evaluated 110 adults with severe TBI. Average and daily estradiol, testosterone, and estradiol/testosterone ratios (E2:T) were measured using CSF and serum samples and compared to healthy controls. Eighteen tagging and four functional single-nucleotide polymorphisms (SNPs) for CYP19A1 were genotyped and compared to hormones, acute mortality, and Glasgow Outcome Scale (GOS) scores 6 months post-TBI. TBI subjects had lower CSF estradiol over time versus controls. CSF testosterone was initially high, but declined over time. E2/T ratios were initially low, compared to controls, but rose over time. Higher mean E2/T ratio in bivariate analysis was associated with lower mortality (p=0.019) and better GOS-6 scores (p=0.030). rs2470152 influenced CSF E2/T ratio and also serum and CSF testosterone (p≤0.05 all comparisons). Multiple-risk SNPs rs2470152, rs4646, and rs2470144 were associated with worse GOS-6 scores (p≤0.05, all comparisons), and those with>1 risk SNP variant had a higher risk for poor outcome, compared with those with ≤1 risk variant. TBI results in low CSF estradiol and dynamic CSF testosterone and E2/T ratio. In contrast to clinical serum hormone studies, higher CSF E2/T ratio was associated with better outcome. Further, genetic variation in CYP19A1 influences both hormone dynamics and outcome post-TBI.

Genetic polymorphism at Val80 (rs700518) of the CYP19A1 gene is associated with aromatase inhibitor associated bone loss in women with ER + breast cancer

PURPOSE

Polymorphisms in the CYP19A1 (aromatase) gene have been reported to influence disease-free survival and the incidence of musculoskeletal complaints in patients taking aromatase inhibitors (AIs) for estrogen receptor positive (ER+) breast cancer. Bone loss and fractures are well-recognized complications from AI therapy. The objective of this study is to determine the influence of polymorphisms in the CYP19A1 gene on bone loss among patients taking aromatase inhibitors for ER+ breast cancer.

PATIENTS AND METHODS

The subjects consisted of 97 postmenopausal women with ER+ breast cancer who were initiated on third-generation AIs. Bone mineral density (BMD) was measured by dual energy X-ray absorptiometry at baseline and at 6 and 12 months. Twenty-four hour urine N-telopeptide (NTX) was measured by Elisa and serum estradiol was measured by ultrasensitive radioimmunoassay at baseline, and at 6 months. Genotyping was done by Taqman SNP allelic discrimination assay.

RESULTS

Women with the AA genotype for the rs700518 (G/A at Val(80)) developed significant bone loss at the lumbar spine and the total hip at 12 months relative to patients carrying the G allele (GA/GG); both p = 0.03. There was a borderline greater increase in urinary NTX in those with the AA genotype compared to patients with the G allele, p = 0.05; but no significant difference in changes in estradiol levels among the genotypes.

CONCLUSION

Patients with the AA genotype for the rs700518 polymorphism in the CYP19A1 gene are at risk for AI-associated bone loss and deserve close follow-up during long-term AI therapy.

Haplotype structures and functional polymorphic variants of the drug target enzyme aromatase (CYP19A1) in South Indian population

CYP19A1 gene product aromatase (CYP19A1) is a 58-kDa protein and belongs to the member of the cytochrome P450 superfamily, which facilitates the bioconversion of estrogens from androgens. Single-nucleotide polymorphisms (SNPs) of CYP19A1 affect the activity of the enzyme and have been implicated in the association of estrogen-dependent disease, prognosis, therapeutic efficacy, and toxicity of third-generation aromatase inhibitors (AIs). Based on ethnicity, the frequency distribution of CYP19A1 alleles will differ, and until now, no data are available for Indians. Using qRT-PCR with TaqMan assays, the frequencies of functionally important polymorphic variants of CYP19A1 gene were determined in 163 healthy subjects of South Indian origin. The observed frequencies of the CYP19A1 minor alleles for the SNPs rs4646 (T), rs10046 (T), rs700519 (T), rs700518 (G), rs727479 (G), rs4775936 (T), rs10459592 (G), rs749292 (A), rs6493497 (T), and rs7176005 (A) are 41.1 (35.8-46.4), 20.0 (15.6-24.3), 33.7 (28.6-38.9), 17.8 (13.6-21.9), 25.8 (21.0-30.5), 19.9 (15.6-24.3), 33.7 (28.6-38.9), 24.9 (20.2-29.5), 35.9 (30.7-41.1), and 35.9 (30.7-41.1), respectively. Strong linkage disequilibrium existed between CYP19A1 SNPs, and sixteen different haplotype structures with a frequency >1% were derived from all the 10 SNPs tested. The most common being the haplotype (H1) GCTATCTGTG with a frequency of about 17.8%. Gender-specific assessment showed significant difference in the allele frequency for rs749292 (p < 0.04), and greater inter-ethnic variation was detected in the distribution of CYP19A1 variants except for rs727479. Our results could provide preliminary insight for further pharmacogenetic investigations of AIs as well as for subsequent molecular epidemiological studies on the contribution of these variants to the occurrence and development of estrogen-dependent disease in South Indians.

CYP19A1 gene polymorphisms and risk of lung cancer

Objectives

To investigate the association between polymorphisms of aromatase (encoded by the CYP19A1 gene and a key enzyme in biosynthesis of oestradiol) and the risk of lung cancer, and whether there were differences stratified by sex and smoking history.

Methods

This case–control study included consecutive, nonselected and pathologically-confirmed lung cancer patients and healthy people. Participants were classed as nonsmokers or smokers by questionnaire. Peripheral blood samples from all participants were genotyped for three single-nucleotide polymorphism (SNPs; rs727479, rs730154 and rs10046); allelic frequencies were compared across genotype and clinical records.

Results

A total of 529 patients with lung cancer and 567 age- and sex-matched controls were included. After adjustment for age, sex and smoking history, rs727479 was significantly associated with the incidence of lung cancer (for alleles AC vs AA). There was also a significant difference between patients and controls in haplotype CCA, while haplotype ACA was only significantly associated with nonsmokers and female nonsmokers.

Conclusions

Polymorphisms of CYP19A1 may be related to the increased risk of lung cancer; in particular, haplotype ACA may contribute to lung-cancer progression in nonsmokers. Further validation with larger populations is required.

The relationship between eight GWAS-identified single-nucleotide polymorphisms and primary breast cancer outcomes

BACKGROUND

Several single-nucleotide polymorphisms (SNPs) associated with breast cancer risk have been identified through genome-wide association studies (GWAS). We investigated whether eight risk SNPs identified in GWAS were associated with breast cancer disease-free survival (DFS) and overall survival (OS) rates.

PATIENTS AND METHODS

A cohort of 739 white women with early-stage breast cancer was genotyped for eight GWAS-identified SNPs (rs2981582, rs1219648 [FGFR2], rs3803662, rs12443621, rs8051542 [TOX3], rs999737 [RAD51L1], rs6504950 [17q23], and rs4973768 [3p24]). Relationships between SNPs and breast cancer outcomes were evaluated using Cox proportional hazard regression models. The cumulative effects of SNPs on breast cancer outcomes were assessed by computing the number of at-risk genotypes.

RESULTS

At a median follow-up of 121 months (range: 188-231 months) for survivors, 237 deaths (32%) and 186 breast cancer events (25%) were identified among the 739 patients. After adjusting for age, clinical stage, and treatment, rs12443621 (16q12; p = .03) and rs6504950 (17q23; p = .008) were prognostic for OS but not DFS. A higher risk for death was also found in the multivariable analysis of patients harboring three or four at-risk genotypes of the GWAS SNPs compared to patients carrying two or less at-risk genotypes (hazard ratio: 1.60, 95% confidence interval: 1.23-2.24; p = .0008).

CONCLUSION

The study results suggest that previously identified breast cancer risk susceptibility loci, rs12443621 (16q12) and rs6504950 (17q23), may influence breast cancer prognosis or comorbid conditions associated with overall survival. The precise molecular mechanisms through which these risk SNPs, as well as others that were not included in the analysis, influence clinical outcomes remain to be determined.

Genetic associations with toxicity-related discontinuation of aromatase inhibitor therapy for breast cancer

Up to 25 % of patients discontinue adjuvant aromatase inhibitor (AI) therapy due to intolerable symptoms. Predictors of which patients will be unable to tolerate these medications have not been defined. We hypothesized that inherited variants in candidate genes are associated with treatment discontinuation because of AI-associated toxicity. We prospectively evaluated reasons for treatment discontinuation in women with hormone receptor-positive breast cancer initiating adjuvant AI through a multicenter, prospective, randomized clinical trial of exemestane versus letrozole. Using multiple genetic models, we evaluated potential associations between discontinuation of AI therapy because of toxicity and 138 variants in 24 candidate genes, selected a priori, primarily with roles in estrogen metabolism and signaling. To account for multiple comparisons, statistical significance was defined as p < 0.00036. Of the 467 enrolled patients with available germline DNA, 152 (33 %) discontinued AI therapy because of toxicity. Using a recessive statistical model, an intronic variant in ESR1 (rs9322336) was associated with increased risk of musculoskeletal toxicity-related exemestane discontinuation [HR 5.0 (95 % CI 2.1-11.8), p < 0.0002]. An inherited variant potentially affecting estrogen signaling may be associated with exemestane-associated toxicity, which could partially account for intra-patient differences in AI tolerability. Validation of this finding is required.

Pharmacogenomics of breast cancer therapy: an update

Clinical and histopathologic characteristics of breast cancer have long played an important role in treatment decision-making. Well-recognized prognostic factors include tumor size, node status, presence or absence of metastases, tumor grade, and hormone receptor expression. High tumor grade, presence of hormone receptors, and HER2-positivity are a few predictive markers of response to chemotherapy, endocrine manipulations, and anti-HER2 agents, respectively. However, there is much heterogeneity of outcomes in patients with similar clinical and pathologic features despite equivalent treatment regimens. Some of the differences in response to specific therapies can be attributed to somatic tumor characteristics, such as degree of estrogen receptor expression and HER2 status. In recent years, there has been great interest in evaluating the role that pharmacogenetics/pharmacogenomics, or variations in germline DNA, play in alteration of drug metabolism and activity, thus leading to disparate outcomes among patients with similar tumor characteristics. The utility of these variations in treatment decision-making remains debated. Here we review the data available to date on genomic variants that may influence response to drugs commonly used to treat breast cancer. While none of the variants reported to date have demonstrated clinical utility, ongoing prospective studies and increasing understanding of pharmacogenetics will allow us to better predict risk of toxicity or likelihood of response to specific treatments and to provide a more personalized therapy.

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.

Regulation of aromatase expression in breast cancer treated with anastrozole neoadjuvant therapy

Aromatase inhibitors (AIs), such as anastrozole, are established in the treatment of hormone-dependent breast cancer. However, ∼20% of patients with hormone receptor-positive breast tumors treated with anastrozole do not respond and it remains impossible to accurately predict sensitivity. Since polymorphisms in the aromatase gene may influence the response to inhibitory drugs, we evaluated the presence of rs6493497 and rs7176005 polymorphisms (mapping in the 5′-flanking region of the CYP19A1 gene coding for the aromatase protein) in a cohort of 37 patients with postmenopausal breast cancer who received three-month neoadjuvant treatment with anastrozole. We then investigated any association of the polymorphisms with changes in aromatase mRNA expression change and/or response to treatment. We also analyzed five miRNAs computationally predicted to target aromatase, to observe any association between their expression and sensitivity to anastrozole. Three samples carried the two polymorphisms and the remaining samples were wild-type for both, however, no association with response or with aromatase mRNA basal expression level or expression difference after therapy was observed. Polymorphic samples that were resistant to anastrozole showed no change or decrease in aromatase expression following AI treatment, whereas an increase in expression was observed for the polymorphic responsive samples. No statistically significant correlation was observed between miRNA and aromatase mRNA expression, or with response to anastrozole neoadjuvant treatment. These data indicate that the polymorphisms analyzed are not involved in aromatase activity and that other epigenetic mechanisms may regulate aromatase protein expression.

Plasma estrone sulfate concentrations and genetic variation at the CYP19A1 locus in postmenopausal women with early breast cancer treated with letrozole

Estrogen synthesis suppression induced by aromatase inhibitors in breast cancer (BC) patients may be affected by single nucleotide polymorphisms (SNPs) of the gene encoding aromatase enzyme, CYP19A1. We assessed the association between plasma estrone sulfate (ES), letrozole treatment, and four SNPs of CYP19A1 gene (rs10046 C>T, rs4646 G>T, rs749292 C>T, rs727479 T>G) which seem to be related to circulating estrogen levels. Patients were enrolled into a prospective, Italian multi-center clinical trial (Gruppo Italiano Mammella, GIM-5) testing the association of CYP19A1 SNPs with the efficacy of letrozole adjuvant therapy, in postmenopausal early BC patients. SNPs were identified from peripheral blood cell DNA. Plasma ES concentrations were evaluated by Radio Immuno Assay. Blood samples were obtained immediately before letrozole therapy (N = 204), at 6-weeks (N = 178), 6 (N = 152) and 12-months (N = 136) during treatment. Medians (IQR) of ES were 160 pg/mL (85–274) at baseline, 35 pg/mL (12–64) at 6-weeks, 29 pg/mL (17–48) at 6 months and 25 pg/mL (8–46) after 12 months treatment. No statistically significant association was evident between polymorphisms and ES circulating levels during letrozole therapy. Letrozole suppression of the aromatase enzyme function is not affected by polymorphisms of CYP19A1 gene in postmenopausal BC patients.