Anastrozole has an Association between Degree of Estrogen Suppression and Outcomes in Early Breast Cancer and is a Ligand for Estrogen Receptor α

Estrogen levels in young women with hormone receptor-positive breast cancer on ovarian function suppression therapy

Ovarian function suppression (OFS) benefits young women with hormone receptor (HR)-positive breast cancer but they are at risk for ovarian function breakthrough. We assessed endocrine effects of gonadotropin-releasing hormone agonist (GnRHa) treatment in a prospective cohort of patients aged ≤ 40 years with HR-positive breast cancer. Plasma estradiol (E2), estrone, and follicule-stimulating hormone (FSH) levels were measured from blood samples drawn 1 and 4 years after diagnosis. Patient characteristics, invasive breast cancer-free survival (iBCFS), and overall survival (OS) were compared between those with and without E2 > 2.72 pg/mL during GnRHa treatment. Among eligible patients, 54.7% (46/84) and 60% (15/25) had E2 > 2.72 pg/mL at 1 and 4 years, respectively. Factors associated with E2 > 2.72 pg/mL at 1 year were no prior chemotherapy (P = 0.045) and tamoxifen use (P = 0.009). After a median follow-up of 7 years, among patients with stage I-III breast cancer (N = 74), iBCFS events were seen in 6 (8.1%) with E2 > 2.72 pg/mL and 5 (6.8%) with E2 ≤ 2.72 pg/mL (P = 0.893). Among patients with de novo metastatic breast cancer (N = 12), 6 (50%) with E2 > 2.72 pg/mL and 3 (25%) with E2 ≤ 2.72 pg/mL died during follow-up (P = 0.052). Larger studies exploring the clinical implications of incomplete E2 suppression by GnRHa are needed to ensure optimal OFS treatment strategies are being employed for this population.

Anastrozole Dose Escalation for Optimal Estrogen Suppression in Postmenopausal Early-Stage Breast Cancer: A Prospective Trial

PURPOSE

We previously reported that postmenopausal women with estrogen receptor-α-positive breast cancer receiving adjuvant anastrozole 1 mg/day (ANA1) with estrone (E1) ≥1.3 pg/mL and estradiol (E2) ≥0.5 pg/mL [inadequate estrogen suppression (IES)] had a threefold increased risk of a breast cancer event. The objective of this study was to determine if increasing anastrozole to 10 mg/day (ANA10) could result in adequate estrogen suppression (AES: E1 <1.3 pg/mL and/or E2 <0.5 pg/mL) among those with IES on ANA1.

PATIENTS AND METHODS

Postmenopausal women with estrogen receptor-α-positive breast cancer planning to receive adjuvant ANA1 were eligible. E1 and E2 were assessed pre- and post-8 to 10 weeks of ANA1. Those with IES were switched to 8- to 10-week cycles of ANA10 followed by letrozole 2.5 mg/day. E1 and E2 were assessed after each cycle. Anastrozole concentrations were measured post-ANA1 and post-ANA10. Primary analyses included patients who documented taking at least 80% of the planned treatment (adherent cohort).

RESULTS

In total, 132 (84.6%) of 156 eligible patients were ANA1 adherent. IES occurred in 40 (30.3%) adherent patients. Twenty-five (78.1%) of 32 patients who began ANA10 were adherent, and AES was achieved in 19 (76.0%; 90% confidence interval, 58.1%-89.0%) patients. Anastrozole concentrations post-ANA1 and post-ANA10 did not differ by estrogen suppression status among adherent patients. AES was maintained/attained in 21 (91.3%) of 23 letrozole-adherent patients.

CONCLUSIONS

Approximately 30% of ANA1-adherent patients had IES. Among those who switched to ANA10 and were adherent, 76% had AES. Further studies are required to validate emerging data that ANA1 results in IES for some patients and to determine the clinical benefit of switching to ANA10 or an alternative aromatase inhibitor.

Androgen receptor-mediated pharmacogenomic expression quantitative trait loci: implications for breast cancer response to AR-targeting therapy

BACKGROUND

Endocrine therapy is the most important treatment modality of breast cancer patients whose tumors express the estrogen receptor α (ERα). The androgen receptor (AR) is also expressed in the vast majority (80-90%) of ERα-positive tumors. AR-targeting drugs are not used in clinical practice, but have been evaluated in multiple trials and preclinical studies.

METHODS

We performed a genome-wide study to identify hormone/drug-induced single nucleotide polymorphism (SNP) genotype - dependent gene-expression, known as PGx-eQTL, mediated by either an AR agonist (dihydrotestosterone) or a partial antagonist (enzalutamide), utilizing a previously well characterized lymphoblastic cell line panel. The association of the identified SNPs-gene pairs with breast cancer phenotypes were then examined using three genome-wide association (GWAS) studies that we have published and other studies from the GWAS catalog.

RESULTS

We identified 13 DHT-mediated PGx-eQTL loci and 23 Enz-mediated PGx-eQTL loci that were associated with breast cancer outcomes post ER antagonist or aromatase inhibitors (AI) treatment, or with pharmacodynamic (PD) effects of AIs. An additional 30 loci were found to be associated with cancer risk and sex-hormone binding globulin levels. The top loci involved the genes IDH2 and TMEM9, the expression of which were suppressed by DHT in a PGx-eQTL SNP genotype-dependent manner. Both of these genes were overexpressed in breast cancer and were associated with a poorer prognosis. Therefore, suppression of these genes by AR agonists may benefit patients with minor allele genotypes for these SNPs.

CONCLUSIONS

We identified AR-related PGx-eQTL SNP-gene pairs that were associated with risks, outcomes and PD effects of endocrine therapy that may provide potential biomarkers for individualized treatment of breast cancer.

Superior suppression of serum estrogens during neoadjuvant breast cancer treatment with letrozole compared to exemestane

PURPOSE

The aromatase inhibitor letrozole and the aromatase inactivator exemestane are two of the most pivotal cancer drugs used for endocrine treatment of ER-positive breast cancer in all phases of the disease. Although both drugs inhibit CYP19 (aromatase) and have been used for decades, a direct head-to-head, intra-patient-cross-over comparison of their ability to decrease estrogen synthesis in vivo is still lacking.

METHODS

Postmenopausal breast cancer patients suitable for neoadjuvant endocrine therapy were randomized to receive either letrozole (2.5 mg o.d.) or exemestane (25 mg o.d.) for an initial treatment period, followed by a second treatment period on the alternative drug (intra-patient cross-over study design). Serum levels of estrone (E1), estradiol (E2), letrozole, exemestane, and 17-hydroxyexemestane were quantified simultaneously using a novel, ultrasensitive LC-MS/MS method established in our laboratory.

RESULTS

Complete sets of serum samples (baseline and during treatment with letrozole or exemestane) were available from 79 patients, including 40 patients starting with letrozole (cohort 1) and 39 with exemestane (cohort 2). Mean serum estrone and estradiol levels in cohort 1 were 174 pmol/L and 46.4 pmol/L at baseline, respectively. Treatment with letrozole suppressed serum E1 and E2 to a mean value of 0.2 pmol/L and 0.4 pmol/L (P < 0.001). After the cross-over to exemestane, mean serum levels of E1 and E2 increased to 1.4 pmol/L and 0.7 pmol/L, respectively. In cohort 2, baseline mean serum levels of E1 and E2 were 159 and 32.5 pmol/L, respectively. Treatment with exemestane decreased these values to 1.8 pmol/L for E1 and 0.6 pmol/L for E2 (P < 0.001). Following cross-over to letrozole, mean serum levels of E1 and E2 were significantly further reduced to 0.1 pmol/L and 0.4 pmol/L, respectively. Serum drug levels were monitored in all patients throughout the entire treatment and confirmed adherence to the protocol and drug concentrations within the therapeutic range for all patients. Additionally, Ki-67 values decreased significantly during treatment with both aromatase inhibitors, showing a trend toward a stronger suppression in obese women.

CONCLUSION

To the best of our knowledge, we present here for the first time a comprehensive and direct head-to-head, intra-patient-cross-over comparison of the aromatase inhibitor letrozole and the aromatase inactivator exemestane concerning their ability to suppress serum estrogen levels in vivo. All in all, our results clearly demonstrate that letrozole therapy results in a more profound suppression of serum E1 and E2 levels compared to exemestane.

Drug repurposing for personalized medicine

Personalized medicine has emerged as a revolutionary approach to healthcare in the 21st century. By understanding a patient's unique genetic and biological characteristics, it aims to tailor treatments specifically to the individual. This approach takes into account factors such as an individual's lifestyle, genetic makeup, and environmental factors to provide targeted therapies that have the potential to be more effective and lower the risk of side reactions or ineffective treatments. It is a paradigm shift from the traditional "one size fits all" approach in medicine, where patients with similar symptoms or diagnoses receive the same standard treatments regardless of their differences. It leads to improved clinical outcomes and more efficient use of healthcare resources. Drug repurposing is a strategy that uses existing drugs for new indications and aims to take advantage of the known safety profiles, pharmacokinetics, and mechanisms of action of these drugs to accelerate the development process. Precision medicine may undergo a revolutionary change as a result, enabling the rapid development of novel treatment plans utilizing drugs that traditional methods would not otherwise link to. In this chapter, we have focused on a few strategies wherein drug repurposing has shown great success for precision medicine. The approach is particularly useful in oncology as there are many variations induced in the genetic material of cancer patients, so tailored treatment approaches go a long way. We have discussed the cases of breast cancer, glioblastoma and hepatocellular carcinoma. Other than that, we have also looked at drug repurposing approaches in anxiety disorders and COVID-19.

Long-term Follow-up and Safety of Patients after an Upfront Therapy with Letrozole for Early Breast Cancer in Routine Clinical Care - The PreFace Study

Introduction

Adjuvant treatment of patients with early-stage breast cancer (BC) should include an aromatase inhibitor (AI). Especially patients with a high recurrence risk might benefit from an upfront therapy with an AI for a minimum of five years. Nevertheless, not much is known about the patient selection for this population in clinical practice. Therefore, this study analyzed the prognosis and patient characteristics of postmenopausal patients selected for a five-year upfront letrozole therapy.

Patients and Methods

From 2009 to 2011, 3529 patients were enrolled into the adjuvant phase IV PreFace clinical trial (NCT01908556). Postmenopausal hormone receptor-positive BC patients, for whom an upfront five-year therapy with letrozole (2.5 mg/day) was indicated, were eligible. Disease-free survival (DFS), overall survival (OS) and safety in relation to patient and tumor characteristics were assessed.

Results

3297 patients started letrozole therapy. The majority of patients (n = 1639, 57%) completed the five-year treatment. 34.5% of patients continued with endocrine therapy after the mandated five-year endocrine treatment. Five-year DFS rates were 89% (95% CI: 88-90%) and five-year OS rates were 95% (95% CI: 94-96%). In subgroup analyses, DFS rates were 83%, 84% and 78% for patients with node-positive disease, G3 tumor grading, and pT3 tumors respectively. The main adverse events (any grade) were pain and hot flushes (66.8% and 18.3% of patients).

Conclusions

The risk profile of postmenopausal BC patients selected for a five-year upfront letrozole therapy showed a moderate recurrence and death risk. However, in subgroups with unfavorable risk factors, prognosis warrants an improvement, which might be achieved with novel targeted therapies.

Safety and Serum Estradiol Levels in Hormonal Treatments for Vulvovaginal Atrophy in Breast Cancer Survivors: A Systematic Review and Meta-Analysis

Vulvo-vaginal atrophy (VVA) or genitourinary syndrome of menopause (GSM) is a common condition among breast cancer (BC) patients, especially those undergoing antiestrogen therapy. Despite being an option in refractory cases, the safety of hormonal treatment remains uncertain in this population. The aim of this study was to review the safety and serum estrogen levels of hormonal therapy in patients with BC history presenting with VVA symptoms. Pubmed, Embase, and Cochrane were searched for studies comparing different hormonal treatment options for VVA in breast cancer survivors. Statistical analysis was performed using a random effects model and heterogeneity using Cochran's Q-statistic and the I2 index. We included 17 studies, of which 5 were randomized controlled trials (RCTs). Treatment modalities included in this study were topical vaginal estradiol and estriol preparations, vaginally applied testosterone, DHEA, and ospemifene. We found that, among patients treated with the estriol and estradiol preparations, there was an average increase of 7.67 pg/mL (SMD 7.67 pg/mL; 95% CI -1.00, 16.35; p < .001). Analysis of the testosterone group found temporary peaks of serum estradiol levels, but 1 study showed persistent elevation above normal postmenopausal levels. One study with prasterone revealed no elevation of serum estradiol concentration. One study with ospemifene demonstrated no increase in the risk of BC recurrence. In conclusion, among treatments available for BC survivors, low-dose vaginal estrogen showed the smallest changes in serum estradiol levels and had the most evidence, but safety remains unclear, especially for patients on aromatase inhibitors. Alternative treatments such as ospemifene need more data supporting safety and efficacy. These results suggest that concerns related to cancer recurrence should keep aiming for the lowest possible concentration.

Ovarian Function Suppression in Premenopausal Women with Concurrent Endocrine Therapy Use

INTRODUCTION

Almost 20% of patients receiving ovarian function suppression (OFS) and endocrine therapy (ET) for breast cancer treatment had inadequate OFS within the first year of treatment. Few studies have explored the long-term effectiveness of OFS to maintain estrogen suppression.

PATIENTS AND METHODS

This retrospective, single institution study examined premenopausal women with early-stage breast cancer undergoing treatment with OFS and ET. The primary endpoint was the percentage of patients with inadequate ovarian suppression (estradiol ≥10 pg/mL) during OFS cycle 2 or later. The secondary endpoint was the percentage of patients with inadequate ovarian suppression within the first cycle after OFS initiation. Differences in age, body mass index (BMI), and previous chemotherapy use were summarized via multivariable logistic regression.

RESULTS

Of the 131 patients included in the analysis, 35 (26.7%) lacked adequate suppression during OFS cycle 2 or later cycles. Patients with adequate suppression throughout treatment were more likely to be older (odds ratio [OR] 1.12 [95% CI, 1.05-1.22], P = .02), have a lower BMI (OR 0.88 [95% CI, 0.82-0.94], P < .001), and have received chemotherapy (OR 6.30 [95% CI, 2.06-20.8], P = .002). A total of 20 of 83 patients (24.1%) had an inadequately suppressed estradiol level within 35 days of OFS initiation.

CONCLUSION

This "real world" cohort demonstrates that estradiol concentrations above the postmenopausal range of the assay are frequently detected, including more than 1 year after the start of OFS. Additional research is needed to establish estradiol monitoring guidelines and optimal degree of ovarian suppression.

Mechanistic Effects of Estrogens on Breast Cancer

PURPOSE

Current concepts regarding estrogen and its mechanistic effects on breast cancer in women are evolving. This article reviews studies that address estrogen-mediated breast cancer development, the prevalence of occult tumors at autopsy, and the natural history of breast cancer as predicted by a newly developed tumor kinetic model.

METHODS

This article reviews previously published studies from the authors and articles pertinent to the data presented.

RESULTS

We discuss the concepts of adaptive hypersensitivity that develops in response to long-term deprivation of estrogen and results in both increased cell proliferation and apoptosis. The effects of menopausal hormonal therapy on breast cancer in postmenopausal women are interpreted based on the tumor kinetic model. Studies of the administration of a tissue selective estrogen complex in vitro, in vivo, and in patients are described. We review the various clinical studies of breast cancer prevention with selective estrogen receptor modulators and aromatase inhibitors. Finally, the effects of the underlying risk of breast cancer on the effects of menopausal hormone therapy are outlined.

DISCUSSION

The overall intent of this review is to present data supporting recent concepts, discuss pertinent literature, and critically examine areas of controversy.

Simultaneous Quantification of Aromatase Inhibitors and Estrogens in Postmenopausal Breast Cancer Patients

CONTEXT

Currently there are no assays that can simultaneously quantify serum levels of the third-generation aromatase inhibitors (AIs): letrozole, anastrozole, and exemestane, and the ultra-low levels of estrogens in postmenopausal breast cancer patients on AI treatment. Such measurements may be pivotal for the determination of optimal and individualized treatment regimens. We aimed at developing a liquid chromatography-tandem mass spectrometry (MS/MS) method for simultaneous assessment of letrozole, anastrozole, exemestane, and 17-hydroxyexemestane as well as subpicomolar levels of estradiol and estrone.

METHODS

Internal standards, calibrators, serum samples, and quality controls were in fully automated steps transferred to a deep-well plate for a 2-step liquid-liquid extraction. The extracts were reconstituted and analytes were separated chromatographically using 2 serially coupled columns, then subject to MS/MS in electrospray ionization mode. The method was thoroughly validated and is traceable to 2 accredited estrogen methods.

RESULTS

The measurement range for estrone and estradiol was 0.2 to 12 000 pmol/L and 0.8 to 13 000 pmol/L, and covered the expected therapeutic range for the AIs. All analytes had a precision of less than or equal to 13%, and accuracies within 100 ± 8%. As proof of concept, AI and estrogen levels were determined in serum samples from postmenopausal breast cancer patients under treatment.

CONCLUSION

We present here an assay suitable for the simultaneous measurement of serum levels of all third-generation AIs and ultra-low levels of estrogens, providing a powerful new tool to study drug efficacy and compliance. The method is highly valuable for postmenopausal patients whose pretreatment estradiol levels are below the threshold of detection for most routine assays, but still require suppression.

Drug Repurposing in Cancer Therapy: Influence of Patient’s Genetic Background in Breast Cancer Treatment

Cancer is among the leading causes of death worldwide and it is estimated that in 2040 more than 29 million people will be diagnosed with some type of cancer. The most prevalent type of cancer in women, worldwide, is breast cancer, a type of cancer associated with a huge death rate. This high mortality is mainly a consequence of the development of drug resistance, which is one of the major challenges to overcome in breast cancer treatment. As a result, research has been focused on finding novel therapeutical weapons, specifically ones that allow for a personalized treatment, based on patients’ characteristics. Although the scientific community has been concerned about guaranteeing the quality of life of cancer patients, researchers are also aware of the increasing costs related to cancer treatment, and efforts have been made to find alternatives to the development of new drugs. The development of new drugs presents some disadvantages as it is a multistep process that is time- and money-consuming, involving clinical trials that commonly fail in the initial phases. A strategy to overcome these disadvantages is drug repurposing. In this review, we focused on describing potential repurposed drugs in the therapy of breast cancer, considering their pharmacogenomic profile, to assess the relationship between patients’ genetic variations and their response to a certain therapy. This review supports the need for the development of further fundamental studies in this area, in order to investigate and expand the knowledge of the currently used and novel potential drugs to treat breast cancer. Future clinical trials should focus on developing strategies to group cancer patients according to their clinical and biological similarities and to discover new potential targets, to enable cancer therapy to be more effective and personalized.

Anastrozole Regulates Fatty Acid Synthase in Breast Cancer

Our previous matched case-control study of postmenopausal women with resected early-stage breast cancer revealed that only anastrozole, but not exemestane or letrozole, showed a significant association between the 6-month estrogen concentrations and risk of breast cancer. Anastrozole, but not exemestane or letrozole, is a ligand for estrogen receptor α. The mechanisms of endocrine resistance are heterogenous and with the new mechanism of anastrozole, we have found that treatment of anastrozole maintains fatty acid synthase (FASN) protein level by limiting the ubiquitin-mediated FASN degradation, leading to increased breast cancer cell growth. Mechanistically, anastrozole decreases the guided entry of tail-anchored proteins factor 4 (GET4) expression, resulting in decreased BCL2-associated athanogene cochaperone 6 (BAG6) complex activity, which in turn, prevents RNF126-mediated degradation of FASN. Increased FASN protein level can induce a negative feedback loop mediated by the MAPK pathway. High levels of FASN are associated with poor outcome only in patients with anastrozole-treated breast cancer, but not in patients treated with exemestane or letrozole. Repressing FASN causes regression of breast cancer cell growth. The anastrozole-FASN signaling pathway is eminently targetable in endocrine-resistant breast cancer.

Interaction Between SNP Genotype and Efficacy of Anastrozole and Exemestane in Early-Stage Breast Cancer

Aromatase inhibitors (AIs) are the treatment of choice for hormone receptor-positive early breast cancer in postmenopausal women. None of the third-generation AIs are superior to the others in terms of efficacy. We attempted to identify genetic factors that could differentiate between the effectiveness of adjuvant anastrozole and exemestane by examining single-nucleotide polymorphism (SNP)-treatment interaction in 4,465 patients. A group of SNPs were found to be differentially associated between anastrozole and exemestane regarding outcomes. However, they showed no association with outcome in the combined analysis. We followed up common SNPs near LY75 and GPR160 that could differentiate anastrozole from exemestane efficacy. LY75 and GPR160 participate in epithelial-to-mesenchymal transition and growth pathways, in both cases with SNP-dependent variation in regulation. Collectively, these studies identified SNPs that differentiate the efficacy of anastrozole and exemestane and they suggest additional genetic biomarkers for possible use in selecting an AI for a given patient.

Mitochondrial estrogen receptors alter mitochondrial priming and response to endocrine therapy in breast cancer cells

Breast cancer is the most common cancer with a high rate of mortality and morbidity among women worldwide. Estrogen receptor status is an important prognostic factor and endocrine therapy is the choice of first-line treatment in ER-positive breast cancer. However, most tumors develop resistance to endocrine therapy. Here we demonstrate that BH3 profiling technology, in particular, dynamic BH3 profiling can predict the response to endocrine therapy agents as well as the development of acquired resistance in breast cancer cells independent of estrogen receptor status. Immunofluorescence analysis and subcellular fractionation experiments revealed distinct ER-α and ER-β subcellular localization patterns in breast cancer cells, including mitochondrial localization of both receptor subtypes. shRNA-mediated depletion of ER-β in breast cancer cells led to resistance to endocrine therapy agents and selective reconstitution of ER-β in mitochondria restored sensitivity. Notably, mitochondria-targeted ER-α did not restore sensitivity, even conferred further resistance to endocrine therapy agents. In addition, expressing mitochondria-targeted ER-β in breast cancer cells resulted in decreased mitochondrial respiration alongside increased total ROS and mitochondrial superoxide production. Furthermore, our data demonstrated that mitochondrial ER-β can be successfully targeted by the selective ER-β agonist Erteberel. Thus, our findings provide novel findings on mitochondrial estrogen signaling in breast cancer cells and suggest the implementation of the dynamic BH3 technique as a tool to predict acquired endocrine therapy resistance.

Monitoring serum estradiol levels in breast cancer patients during extended adjuvant letrozole treatment after five years of tamoxifen: a prospective trial

PURPOSE

To analyze whether monitoring serum estradiol (E2) levels using a highly sensitive and specific liquid chromatography tandem mass spectrometry (LC-MS/MS) method may identify patients with AI failure with E2 levels below the lower limit of quantification (LLOQ) after schwitching from tamoxifen to letrozole.

METHODS

In a prospective study of breast cancer patients switching to letrozole treatment after previous tamoxifen, plasma estrogen levels were measured at baseline and after 3- and 12-months using LC-MS/MS.

RESULTS

Forty-six patients were classified postmenopausal and entered into the final analysis. Thirty-nine (85%) patients had three- and 12-month E2 concentrations below the LLOQ (5 pmol/L). In the seven patients classified as AI-failures during letrozole treatment, serum E2-MS level rose above 5 pmol/L at 3 months with a mean E2-MS 77.5 pmol/L or 12 months with a mean E2-MS 21 pmol/L. None of the baseline variables i.e., age at diagnosis, age at study entry, age at menarche, BMI, endometrial thickness, total ovarian volume, baseline FSH, E2-IA, or E2-MS were significantly associated with the risk of AI failure in logistic regression. E2 levels at baseline measured by E2-IA did not significantly correlate to the levels measured by E2-MS.

CONCLUSIONS

There is a relatively high risk of inadequate estrogen suppression in patients who switch from tamoxifen treatment to AIs. The use of sensitive and specific assays, such as LC-MS/MS methods, to monitor estrogen levels during AI treatment is essential to minimize the risk of a proceeding inefficient endocrine therapy.

Single-nucleotide polymorphism biomarkers of adjuvant anastrozole-induced estrogen suppression in early breast cancer

OBJECTIVES

Based on our previous findings that postmenopausal women with estrone (E1) and estradiol (E2) concentrations at or above 1.3 pg/ml and 0.5 pg/ml, respectively, after 6 months of adjuvant anastrozole therapy had a three-fold risk of recurrence, we aimed to identify a single-nucleotide polymorphism (SNP)-based model that would predict elevated E1 and E2 and then validate it in an independent dataset.

PATIENTS AND METHODS

The test set consisted of 322 women from the M3 study and the validation set consisted of 152 patients from MA.27. All patients were treated with adjuvant anastrozole, had on-anastrozole E1 and E2 concentrations and genome-wide genotyping.

RESULTS

SNPs were identified from the M3 genome-wide association study. The best model to predict the E1-E2 phenotype with high balanced accuracy was a support vector machine model using clinical factors plus 46 SNPs. We did not have an independent cohort that is similar to the M3 study with clinical, E1-E2 phenotypes and genotype data to test our model. Hence, we chose a nested matched case-control cohort (MA.27 study) for testing. Our E1-E2 model was not validated but we found the MA.27 validation cohort was both clinically and genomically different.

CONCLUSIONS

We identified a SNP-based model that had excellent performance characteristics for predicting the phenotype of elevated E1 and E2 in women treated with anastrozole. This model was not validated in an independent dataset but that dataset was clinically and genomically substantially different. The model will need validation in a prospective study.

Gene Expression Signatures of BRCAness and Tumor Inflammation Define Subgroups of Early-Stage Hormone Receptor-Positive Breast Cancer Patients

PURPOSE

Patients with estrogen receptor- and/or progesterone receptor-positive, early breast cancer benefit from hormonal treatment, yet high global death burdens due to high prevalence and long-term recurrence risk call for biomarkers to guide additional treatment approaches.

EXPERIMENTAL DESIGN

From a prospective, observational study of postmenopausal early breast cancer patients treated with tamoxifen or aromatase inhibitors, gene expression analyses of 612 tumors was performed using the NanoString Breast Cancer 360 panel to interrogate 23 breast cancer pathways. Candidate signatures associated with disease subtype and event-free survival (EFS) were obtained by cluster analysis, Cox modeling, and conditional inference trees, and were independently tested in 613 patients from BreastMark. Tumor-infiltrating lymphocytes (TIL) were assessed on tissue sections, and mutational burden was assessed in 36 tumors by whole-exome sequencing.

RESULTS

PAM50-derived classification distinguished lower-risk (Luminal A) from higher-risk subtypes (Luminal B, P = 0.04; HER2, P = 0.006; Basal, P = 0.008). In higher-risk patients, shorter EFS was associated with low androgen receptor [HR = 3.61; 95% confidence interval (CI), 1.72-7.56; P = 0.001] or high BRCAness signature expression (HR = 3.58; 95% CI, 1.19-10.7; P = 0.023). BRCAness was independently confirmed as a predictor of shorter EFS (HR = 2.64; 95% CI, 1.31-5.34; P = 0.007). About 13%-15% of patients, enriched for high-grade, higher-risk subtypes (P ≤ 0.0001), had strong expression of the Tumor Inflammation Signature (TIS) suggestive of an inhibited antitumor immune response. TIS scores were strongly associated with TIL numbers (P < 1e-30) but not with tumor mutation status.

CONCLUSIONS

BRCA-related DNA repair deficiency and suppressed tumor immune responses may be clinically relevant predictors of endocrine therapy complementing treatment options in subgroups of hormone-sensitive early breast cancer.

Development, Characterization and In Vitro Evaluation of Paclitaxel and Anastrozole Co-Loaded Liposome

Paclitaxel (PTX) and anastrozole (ANA) have been frequently applied in breast cancer treatment. PTX is well-known for its anti-proliferative effect meanwhile ANA has just been discovered to act as an estrogen receptor α (ERα) ligand. The combination therapy of PTX and ANA is expected to improve treating efficiency, as ANA would act as a ligand binding with the ERα gene expressed in breast cancer cells and thereafter PTX would inhibit the division and cause death to those cancer cells. In this study, liposome-based nanocarriers (LP) were developed for co-encapsulation of PTX and ANA to improve the efficacy of the combined drugs in an Estrogen receptor-responsive breast cancer study. PTX-ANA co-loaded LP was prepared using thin lipid film hydration method and was characterized for morphology, size, zeta potential, drug encapsulation and in vitro drug release. In addition, cell proliferation (WST assay) and IN Cell Analyzer were used for in vitro cytotoxicity studies on a human breast cancer cell line (MCF-7). Results showed that the prepared LP and PTX-ANA-LP had spherical vesicles, with a mean particle size of 170.1 ± 13.5 nm and 189.0 ± 22.1 nm, respectively. Controlled and sustained releases were achieved at 72 h for both of the loaded drugs. The in vitro cytotoxicity study found that the combined drugs showed higher toxicity than each single drug separately. These results suggested a new approach to breast cancer treatment, consisting of the combination therapy of PTX and ANA in liposomes based on ER response.

Pharmacogenomics of aromatase inhibitors in postmenopausal breast cancer and additional mechanisms of anastrozole action

Aromatase inhibitors (AIs) reduce breast cancer recurrence and prolong survival, but up to 30% of patients exhibit recurrence. Using a genome-wide association study of patients entered on MA.27, a phase III randomized trial of anastrozole versus exemestane, we identified a single nucleotide polymorphism (SNP) in CUB And Sushi multiple domains 1 (CSMD1) associated with breast cancer–free interval, with the variant allele associated with fewer distant recurrences. Mechanistically, CSMD1 regulates CYP19 expression in an SNP- and drug-dependent fashion, and this regulation is different among 3 AIs: anastrozole, exemestane, and letrozole. Overexpression of CSMD1 sensitized AI-resistant cells to anastrozole but not to the other 2 AIs. The SNP in CSMD1 that was associated with increased CSMD1 and CYP19 expression levels increased anastrozole sensitivity, but not letrozole or exemestane sensitivity. Anastrozole degrades estrogen receptor α (ERα), especially in the presence of estradiol (E2). ER⁺ breast cancer organoids and AI- or fulvestrant-resistant breast cancer cells were more sensitive to anastrozole plus E2 than to AI alone. Our findings suggest that the CSMD1 SNP might help to predict AI response, and anastrozole plus E2 serves as a potential new therapeutic strategy for patients with AI- or fulvestrant-resistant breast cancers.

A germline variation within the CSMD1 gene predicts aromatase inhibitor response in breast cancer.