Aromatase Inhibitors for the Treatment and Prevention of Breast Cancer

Aromatase inhibitors for the treatment of breast cancer: An overview (2019-2023)

Aromatase inhibition is considered a legitimate approach for the treatment of ER-positive (ER+) breast cancer as it accounts for more than 70% of breast cancer cases. Aromatase inhibitor therapy has been demonstrated to be highly effective in decreasing tumour size, increasing survival rates, and lowering the chance of cancer recurrence. The present review deliberates the pathophysiology and the role of aromatase in estrogen biosynthesis. Estrogen biosynthesis, various androgens, and their function in the human body have also been discussed. The salient aspects of the aromatase active site, its mode of action, and AIs, along with their intended interactions with presently FDA-approved inhibitors, have been briefly discussed. It has been detailed how different reported AIs were designed, their SAR investigations, in silico analysis, and biological evaluations. Various AIs from multiple origins, such as synthetic and semi-synthetic, have also been discussed.

Research Progress on Bioactive Metal Complexes against ER-Positive Advanced Breast Cancer

Breast cancer is the most prevalent cancer in women and represents a serious disease that is harmful to life and health. In 1977, with the approval of tamoxifen, endocrine therapy has become the main clinical treatment for ER-positive (ER+) breast cancer. Although patients initially respond well to endocrine therapies, drug resistance often emerges and side effects can be challenging. To overcome drug resistance, the exploration for new drugs is a priority. Metal complexes have demonstrated significant antitumor activities, and platinum complexes are widely used in the clinic against various cancers, including breast cancer. In this Perspective, the first section describes the classification and mechanism of endocrine therapy drugs for ER+ breast cancer, and the second section summarizes research since 2000 into metal complexes with activity toward ER+ breast cancer. Finally, we discuss the opportunities, challenges, and future directions for metal complexes in the treatment of ER+ breast cancer.

Global Trends in Research of Androgen Receptor Associated With Breast Cancer From 2011 to 2020: A Scientometric Analysis

Recently, the androgen receptor has been found as a potential prognostic index and therapeutic target for breast cancer. To reveal the current research status and hotspots in this area, we analyzed the characteristics of related publications from 2011 to 2020. All related publications from 2011 to 2020 were retrieved from the Web of Science. Biblioshiny, VOSviewer, and CiteSpace V were applied to obtain the information on annual publications and citations, the highest yielding countries and authors, influential journals and articles, as well as hot keywords. In total, 2,118 documents, including 1,584 original articles and 534 reviews, were retrieved. Annual publication output was rich from 2014 to 2018, reaching the top in 2017. A systematic review written by Lehman et al. in 2011 was the most-cited document and reference. The United States was the leading country with the maximum number of publications, citations, and link strengths with other countries. The journal publishing the most was Oncotarget. Lehmann was the author who had the highest link strengths with other authors. The most highlighted keywords were "androgen receptor" (n = 1,209), "breast cancer" (n = 690), "expression" (n = 545), "breast cancer" (n = 410), "prostate cancer" (n = 290), and so on, revealing the trend from molecular mechanism level to therapeutic use level. The androgen receptor plays a significant role in the development of breast cancers, whereas its therapeutic value seems to be controversial and needs further study. With the help of a scientometric analysis in this field, researchers can clarify the current research status and hotspots worth fully exploring.

Development and evaluation of exemestane-loaded lyotropic liquid crystalline gel formulations

Introduction: The use of liquid crystalline (LC) gel formulations for drug delivery has considerably improved the current delivery methods in terms of bioavailability and efficacy. The purpose of this study was to develop and evaluate LC gel formulations to deliver the anti-cancer drug exemestane through transdermal route. Methods: Two LC gel formulations were prepared by phase separation coacervation method using glyceryl monooleate (GMO), Tween 80 and Pluronic® F127 (F127). The formulations were characterized with regard to encapsulation efficiency (EE), vesicle size, Fourier transform infrared (FTIR) spectroscopy, surface morphology (using light and fluorescence microscopy), in vitro release, ex vivo permeation, in vitro effectiveness test on MDA-MB231 cancer cell lines and histopathological analysis. Results: Results exhibited that the EE was 85%-92%, vesicle size was 119.9-466.2 nm while morphology showed spherical vesicles after hydration. An FTIR result also revealed that there was no significant shift in peaks corresponding to Exemestane and excipients. LC formulations release the drug from cellulose acetate and Strat-MTM membrane from 15%-88.95%, whereas ex vivo permeation ranges from 37.09-63%. The in vitro effectiveness study indicated that even at low exemestane concentrations (12.5 and 25 μg/mL) the formulations were able to induce cancer cell death, regardless of the surfactant used. Histopathological analysis thinning of the epidermis as the formulations penetrate into the intercellular regions of squamous cells. Conclusion: The results conjectured that exemestane could be incorporated into LC gels for the transdermal delivery system and further preclinical studies such as pharmacokinetic and pharmacodynamic studies will be carried out with suitable animal models.

Association of serum sex steroid receptor bioactivity and sex steroid hormones with breast cancer risk in postmenopausal women

Postmenopausal women with elevated serum sex steroids have an increased risk of breast cancer. Most of this risk is believed to be exerted through binding of the sex steroids to their receptors. For the first time, we investigate the association of estrogen receptor (ER) and androgen receptor (AR) serum bioactivity (SB) in addition to hormone levels in samples from women with breast cancer collected before diagnosis. Two hundred postmenopausal women participating in the UK Collaborative Trial of Ovarian Cancer Screening who developed ER-positive breast cancer 0.6-5 years after sample donation were identified and matched to 400 controls. ER and AR bioassays were used to measure ERα, ERβ, and AR SB. Androgen and estrogen levels were measured with immunoassays. Subjects were classified according to quintiles of the respective marker among controls and the associations between SB and hormones with breast cancer risk were determined by logistic regression analysis. ERα and ERβ SB were significantly higher before diagnosis compared with controls, while estrogens showed no difference. Women had a twofold increased breast cancer risk if ERα SB (odds ratio (OR), 2.114; 95% confidence interval (CI), 1.050-4.425; P=0.040) was in the top quintile >2 years before diagnosis or estrone (OR, 2.205; 95% CI, 1.104-4.586; P=0.029) was in the top quintile <2 years before diagnosis. AR showed no significant association with breast cancer while androstenedione (OR, 3.187; 95% CI, 1.738-6.044; P=0.0003) and testosterone (OR, 2.145; 95% CI, 1.256-3.712; P=0.006) were significantly higher compared with controls and showed a strong association with an almost threefold increased breast cancer risk independent of time to diagnosis. This study provides further evidence on the association of androgens and estrogens with breast cancer. In addition, it reports that high ER but not AR SB is associated with increased breast risk >2 years before diagnosis.

A multidisciplinary approach to the management of breast cancer, part 1: prevention and diagnosis

Breast cancer is the most common cancer among women in the United States, with an estimated 200,000 new cases diagnosed annually. A multidisciplinary focus that entails prevention, diagnosis, and treatment has led to significant strides in the reduction of breast cancer incidence and mortality. Additionally, breast cancer management has become increasingly complex, requiring comprehensive assessment and review of multiple issues that include the role of genetic testing, imaging and breast magnetic resonance imaging, surgical and reconstructive options, and a variety of new adjuvant therapies. It has become more evident that a multidisciplinary team approach that involves a spectrum of breast experts is necessary to provide optimal care to patients. This team includes medical oncologists, breast radiologists, breast pathologists, surgical breast specialists, radiation oncologists, geneticists, and primary care physicians. Furthermore, patient knowledge has increased use of the Internet, and more patients are seeking a multidisciplinary approach to treatment. This review considers information for health care professionals who will facilitate optimal patient care for women at increased risk for or presenting with a new diagnosis of breast cancer. The multidisciplinary team of authors, representing the different disciplines, has selected important state-of-the-art issues that arise in their daily practices for consideration, rather than summarizing what is already available in textbooks.

Strategies for the Prevention of Treatment-Related Bone Loss in Women Receiving Adjuvant Hormonal Therapy

More than 220,000 women will be diagnosed with breast cancer this year, and approximately 75% of these women will be long-term survivors of this disease. Survival has improved largely because of advances in adjuvant hormone therapy and chemotherapy, as well as early detection strategies. Because most women will receive adjuvant treatment, and the majority will survive cancer, it is increasingly important to understand the resultant toxicities and to devise monitoring and treatment strategies to avoid adverse long-term effects. Loss of bone mineral density leading to osteoporosis and increased risk of fracture as well as other morbidities is a well known complication of estrogen suppression associated with use of aromatase inhibitors (AIs) in postmenopausal women, and ovarian suppression with GnRH agonists or chemotherapy in premenopausal women. Hormone receptor positivity is increasingly frequent with increasing patient age, so that a large number of women already at risk for osteopenia associated with menopause are at risk for further bone loss caused by adjuvant hormone therapy with AIs. This article will review data on bone mineral density loss and risk of fracture in the large, randomized phase III trials comparing tamoxifen to AIs using the upfront, switching or extended hormone therapy approach. Data from prophylactic bisphosphonate intervention trials in both post- and premenopausal women will be discussed. Ongoing trials are described.

Chemoprevention of breast cancer among Asian women--its perspective and problems

Chemoprevention of breast cancer employing tamoxifen and others has been demonstrated to be effective in reducing the frequency of developing breast malignancy in Western countries. In Asian countries, the frequency of breast cancer as well as its premalignant lesions has recently increased. Therefore, the possible chemoprevention may benefit those women with potential high risks of developing breast cancer and with premalignant lesions. However, the details of these findings of chemoprevention in Western countries have not been available for women with Asian descendant. In addition, risk factors of developing breast cancer in healthy women have not been established in Asian countries compared to Western countries with relative paucity of familial breast cancer cases. Thus, possible chemoprevention of breast cancer in Asian countries may be targeted toward those with established premalignant breast lesions such as ductal carcinoma in situ and/or atypical ductal hyperplasia. However, due to their recent increment of their incidence, biological and/or clinical features of these premalignant breast lesions have not been extensively characterized in Asian women and further investigations are required for wide spread chemoprevention.

From adjuvant to preventive breast cancer treatment: bridging the gap over troubled waters

Recently, chemoprevention trials have demonstrated the efficacy of preventive medical treatment (PMT) in reducing breast cancer (BC) detection rates in at-risk affected and unaffected women selected according to clinical and/or familial risk criteria, particularly with the use of tamoxifen (TAM). Major concerns limiting the routine use of TAM are the questionable benefit/risk ratio and poor patient compliance, which justify the studies undertaken to determine the efficacy of aromatase inhibitors (AIs) with respect to TAM. Issues such as therapy duration, impact on survival, incidence of side-effects and which subsets benefit most from treatment, still remain unsolved. Therefore, only ER+ BC patients are routinely subjected to PMT, independently of their BRCA1/2 status, using adjuvant hormonal therapy. More attention must be focused towards BRCA1/2 carriers as they are probably the women at highest risk of developing BC, in which available data remain controversial and in which hormone-therapy might be important. Hence, at-risk women (affected patients or unaffected women) should be carefully evaluated for inclusion into highly selected preventive clinical trials aimed at evaluating PMT independently of, or according to, BC predisposition status (unknown, positive or negative BRCA1/BRCA2 status) and with respect to menopausal status. BC patients, harboring a BRCA1/2 predisposition, may represent the best subset for extended adjuvant treatment, useful as PMT, simultaneously. Only the evolving differentiation of categories of at-risk women will allow physicians to discriminate PMT in a highly selective manner.

Selective estrogen receptor modulators inhibit growth and progression of premalignant lesions in a mouse model of ductal carcinoma in situ

Introduction

Ductal carcinoma in situ (DCIS) is a noninvasive premalignant lesion and is considered a precursor to invasive carcinoma. DCIS accounts for nearly 20% of newly diagnosed breast cancer, but the lack of experimentally amenable in vivo DCIS models hinders the development of treatment strategies. Here, we demonstrate the utility of a mouse transplantation model of DCIS for chemoprevention studies using selective estrogen receptor modulators (SERMs). This model consists of a set of serially transplanted lines of genetically engineered mouse mammary intraepithelial neoplasia (MIN) outgrowth (MIN-O) tissue that have stable characteristics. We studied the ovarian-hormone-responsiveness of one of the lines with a particular focus on the effects of two related SERMs, tamoxifen and ospemifene.

Methods

The estrogen receptor (ER) status and ovarian-hormone-dependence of the mouse MIN outgrowth tissue were determined by immunohistochemistry and ovarian ablation. The effects of tamoxifen and ospemifene on the growth and tumorigenesis of MIN outgrowth were assessed at 3 and 10 weeks after transplantation. The effects on ER status, cell proliferation, and apoptosis were studied with immunohistochemistry.

Results

The MIN-O was ER-positive and ovarian ablation resulted in reduced MIN-O growth and tumor development. Likewise, tamoxifen and ospemifene treatments decreased the MIN growth and tumor incidence in comparison with the control (P < 0.01). Both SERMs significantly decreased cell proliferation. Between the two SERM treatment groups, there were no statistically significant differences in MIN-O size, tumor latency, or proliferation rate. In contrast, the ospemifene treatment significantly increased ER levels while tamoxifen significantly decreased them.

Conclusion

Tamoxifen and ospemifene inhibit the growth of premalignant mammary lesions and the progression to invasive carcinoma in a transplantable mouse model of DCIS. The inhibitory effects of these two SERMs are similar except for their effects on ER modulation. These differences in ER modulation may suggest different mechanisms of action between the two related SERMs and may portend different long-term outcomes. These data demonstrate the value of this model system for preclinical testing of antiestrogen or other therapies designed to prevent or delay the malignant transformation of premalignant mammary lesions in chemoprevention.