Effects of oestrogens and anti-oestrogens on normal breast tissue from women bearing BRCA1 and BRCA2 mutations

ER-positive and BRCA2-mutated breast cancer: a literature review

BRCA2-mutated carriers have a high lifetime risk of breast cancer (BC), an early age of onset, and an increased risk of other cancers (including ovarian, pancreatic, and prostate cancer). Almost 70-80% of BRCA2-mutated BC are estrogen receptor (ER)-positive, which is a particular type of ER-positive BC that differs from sporadic ER-positive BC. This article reviews the clinicopathological features, treatment, and prognosis of ER-positive and BRCA2-mutated BC to provide a reference for clinical decision-making.

BRCA Genes: The Role in Genome Stability, Cancer Stemness and Therapy Resistance

Carcinogenesis is a multistep process, and tumors frequently harbor multiple mutations regulating genome integrity, cell division and death. The integrity of cellular genome is closely controlled by the mechanisms of DNA damage signaling and DNA repair. The association of breast cancer susceptibility genes BRCA1 and BRCA2 with breast and ovarian cancer development was first demonstrated over 20 years ago. Since then the germline mutations within these genes were linked to genomic instability and increased risk of many other cancer types. Genomic instability is an engine of the oncogenic transformation of non-tumorigenic cells into tumor-initiating cells and further tumor evolution. In this review we discuss the biological functions of BRCA1 and BRCA2 genes and the role of BRCA mutations in tumor initiation, regulation of cancer stemness, therapy resistance and tumor progression.

BRCA Mutations and Breast Cancer Prevention

Women who inherit a deleterious BRCA1 or BRCA2 mutation face substantially increased risks of developing breast cancer, which is estimated at 70%. Although annual screening with magnetic resonance imaging (MRI) and mammography promotes the earlier detection of the disease, the gold standard for the primary prevention of breast cancer remains bilateral mastectomy. In the current paper, I review the evidence regarding the management of healthy BRCA mutation carriers, including key risk factors and protective factors, and also discuss potential chemoprevention options. I also provide an overview of the key findings from the literature published to date, with a focus on data from studies that are well-powered, and preferably prospective in nature.

Personalized prevention in high risk individuals: Managing hormones and beyond

Increasing numbers of women are being identified at 'high-risk' of breast cancer, defined by The National Institute of Health and Care Excellence (NICE) as a 10-year risk of ≥8%. Classically women have been so identified through family history based risk algorithms or genetic testing of high-risk genes. Recent research has shown that assessment of mammographic density and single nucleotide polymorphisms (SNPs), when combined with established risk factors, trebles the number of women reaching the high risk threshold. The options for risk reduction in such women include endocrine chemoprevention with the selective estrogen receptor modulators tamoxifen and raloxifene or the aromatase inhibitors anastrozole or exemestane. NICE recommends offering anastrozole to postmenopausal women at high-risk of breast cancer as cost effectiveness analysis showed this to be cost saving to the National Health Service. Overall uptake to chemoprevention has been disappointingly low but this may improve with the improved efficacy of aromatase inhibitors, particularly the lack of toxicity to the endometrium and thrombogenic risks. Novel approaches to chemoprevention under investigation include lower dose and topical tamoxifen, denosumab, anti-progestins and metformin. Although oophorectomy is usually only recommended to women at increased risk of ovarian cancer it has been shown in numerous studies to reduce breast cancer risks in the general population and in those with mutations in BRCA1/2. However, recent evidence from studies that have confined analysis to true prospective follow up have cast doubt on the efficacy of oophorectomy to reduce breast cancer risk in BRCA1 mutation carriers, at least in the short-term.

Proliferation and ovarian hormone signaling are impaired in normal breast tissues from women with BRCA1 mutations: benefit of a progesterone receptor modulator treatment as a breast cancer preventive strategy in women with inherited BRCA1 mutations

Women with inherited BRCA1 mutations have an elevated risk (40-80%) for developing breast and ovarian cancers. Reproductive history has been reported to alter this risk, suggesting a relationship between ovarian hormone signaling and BRCA1-related tumor development. BRCA1 interactions with estrogen receptor (ER) and progesterone receptor (PR) signaling were previously described in human breast cancer cell lines and mouse models. However, few studies have examined the effect of ovarian hormone regulation in normal human breast tissues bearing a heterozygous BRCA1 mutation. This study compares the proliferation level (Ki67) and the expression of ER, PR, and of the PR target gene, fatty acid synthase (FASN), in histologically normal breast tissues from women with BRCA1 mutations (BRCA1+/mut, n=23) or without BRCA1 mutations (BRCA1+/+, n=28). BRCA1+/mut tissues showed an increased proliferation and impaired hormone receptor expression with a marked loss of the PR isoform, PR-B. Responses to estradiol and progesterone treatments in BRCA1+/mut and BRCA1+/+ breast tissues were studied in a mouse xenograft model, and showed that PR and FASN expression were deregulated in BRCA1+/mut breast tissues. Progesterone added to estradiol treatment increased the proliferation in a subset of BRCA1+/mut breast tissues. The PR inhibitor, ulipristal acetate (UPA), was able to reverse this aberrant progesterone-induced proliferation. This study suggests that a subset of women with BRCA1 mutations could be candidates for a UPA treatment as a preventive breast cancer strategy.

Responsiveness of Brca1 and Trp53 Deficiency-Induced Mammary Preneoplasia to Selective Estrogen Modulators versus an Aromatase Inhibitor in Mus musculus

An intervention study initiated at age 4 months compared the impact of tamoxifen (25 mg), raloxifene (22.5 mg), and letrozole (2.5 mg) administered by 60-day release subcutaneous pellet on mammary preneoplasia prevalence at age 6 months in conditional genetically engineered mouse models with different Breast cancer 1 (Brca1) gene dosages targeted to mammary epithelial cells and germline Tumor protein P53 (Trp53) haploinsufficiency (10-16/cohort). The proportion of unexposed control mice demonstrating mammary preneoplasia at age 6 months was highest in Brca1^{fl11/fl11/Cre/p53-/+} (54%) mice followed by Brca1^{WT/fl11/Cre/p53-/+} mice (30%). By age 12 months, invasive mammary cancers appeared in 80% of Brca1^{fl11/fl11/Cre/p53-/+} and 42% of Brca1^{WT/fl11/Cre/p53-/+} control unexposed mice. The spectrum of cancer histology was similar in both models without somatic mutation of the nongenetically engineered Brca1, Trp53, Brca2, or Death-associated protein kinase 3 (Dapk3) alleles. Two-month exposure to tamoxifen, raloxifene, and letrozole significantly reduced estrogen-mediated tertiary branching by 65%, 71%, and 78%, respectively, in Brca1^{fl11/fl11/Cre/p53-/+} mice at age 6 months. However, only letrozole significantly reduced hyperplastic alveolar nodules (HAN) prevalence (by 52%) and number (by 30%) and invasive cancer appeared despite tamoxifen exposure. In contrast, tamoxifen significantly reduced HAN number by 95% in Brca1^{WT/fl11/Cre/p53-/+} mice. Control mice with varying combinations of the different genetically modified alleles and MMTV-Cre transgene demonstrated that the combination of Brca1 insufficiency and Trp53 haploinsufficiency was required for appearance of preneoplasia and no individual genetic alteration confounded the response to tamoxifen. In summary, although specific antihormonal approaches showed effectiveness, with Brca1 gene dosage implicated as a possible modifying variable, more effective chemopreventive approaches for Brca1 mutation-induced cancer may require alternative and/or additional agents. Cancer Prev Res; 10(4); 244-54. ©2017 AACR.

Loss of glucocorticoid receptor activation is a hallmark of BRCA1-mutated breast tissue

Glucocorticoids (GCs) regulate cell homeostasis and can affect carcinogenesis. An inherited germline mutation in the BRCA1 gene, a tumor suppressor gene, confers a predisposition to breast and ovarian cancers. BRCA1 participates in the maintenance of genome stability through DNA repair, in cellular homeostasis through gene transcription, and in signaling regulation. The interaction between BRCA1 and the glucocorticoid receptor (GR) signaling pathway was studied in normal breast tissues and triple-negative breast cancers from BRCA1 mutation carriers. A loss of the active Ser211 phosphorylated form of GR was found in the mutant as compared to the non-mutant. In in vitro studies, the BRCA1 status in breast cancer cell lines regulates GC-dependent proliferation/apoptosis and impacts GC-dependent gene expression. The lack of BRCA1 inhibited dexamethasone actions on its target genes' expression and the opposite effect was seen with BRCA1 overexpression. BRCA1 overexpression enhances MAPK p38 phosphorylation, resulting in an amplification of GR phosphorylation on Ser 211 and GR basal expression. Our results indicate that BRCA1 is essential to develop an efficient GC signalization. GR P-Ser211 levels may constitute an important diagnostic factor for screening BRCA1 loss of expression in tumors from BRCA1 mutation carriers as well as in sporadic BRCAness tumors. This marker may help to optimize therapeutic strategies.

Baseline E(2) levels are higher in BRCA2 mutation carriers: a potential target for prevention?

PURPOSE

BRCA gene mutations and elevated serum estradiol (E(2)) are well-known risk factors for breast cancer. The aim of this study was to investigate the association between BRCA gene mutations and serum E(2) level.

METHODS

We measured baseline (menstrual cycle day 2-3) E(2) levels of 96 women with breast cancer who underwent BRCA testing.

RESULTS

The mean age, parity, and age at menarche did not differ between women with and without BRCA1/2 mutations. Basal serum E(2) level was significantly higher in women with BRCA2 mutations compared to women with BRCA1 mutations or without BRCA mutations (71.7 ± 41.6 vs. 45.5 ± 20.7 vs. 38.5 ± 12.6 pg/ml in BRCA2 mutation carriers, BRCA1 mutation carriers, and non-carriers, respectively, p value = 0.03). Women with BRCA2 mutations had 3.1 times as great risk for high basal E(2) level (>48 pg/ml) as women without BRCA mutations after adjusting for age and BMI (95 % confidence interval: 1.3, 7.6). BRCA mutation carriers with high serum E(2) level were significantly younger than the carriers with low serum E(2) level (31.4 ± 3.1 vs. 34.7 ± 4.9 years, p = 0.04).

CONCLUSIONS

In this pilot study, we found an association between high basal serum E(2) levels and BRCA2 mutations. Our results suggest that increased production of E(2) may have a role in the pathogenesis of BRCA2-mutation-related breast cancer.

Risk-reducing strategies for women carrying BRCA1/2 mutations with a focus on prophylactic surgery

Background

Women who have inherited mutations in the BRCA1 or BRCA2 genes have substantially elevated risks of breast and ovarian cancer. Mutation carriers have various options, including extensive and regular surveillance, chemoprevention and risk-reducing surgery. The aim of this review is to provide an up-to-date analysis and to subsequently summarise the available literature in relation to risk-reducing strategies, with a keen focus on prophylactic surgery.

Methods

The literature review is facilitated by Medline and PubMed databases. The cross-referencing of the obtained articles was used to identify other relevant studies.

Results

Prophylactic surgery (bilateral mastectomy, bilateral salpingo-oophorectomy or a combination of both procedures) has proved to be the most effective risk-reducing strategy. There are no randomised controlled trials able to demonstrate the potential benefits or harms of prophylactic surgery; therefore, the evidence has been derived from retrospective and short follow-up prospective studies, in addition to hypothetical mathematical models.

Based on the current knowledge, it is reasonable to recommend prophylactic oophorectomy for BRCA1 or BRCA2 mutation carriers when childbearing is completed in order to reduce the risk of developing breast and ovarian cancer. In addition, women should be offered the options of rigorous breast surveillance, chemoprevention with anti-oestrogens--especially for carriers of BRCA2--or bilateral prophylactic mastectomy.

Conclusion

The selection of the most appropriate risk-reducing strategy is not a straightforward task. The impact of risk-reducing strategies on cancer risk, survival, and overall quality of life are the key criteria considered for decision-making. Notably, various other factors should be taken into consideration when evaluating individual mutation carriers' individual circumstances, namely woman's age, morbidity, type of mutation, and individual preferences and expectations.

Although prospective randomised controlled trials concerned with examining the various interventions in relation to the woman's age and type of mutation are needed, randomisation is extremely difficult and rather deemed unethical given the current available evidence from retrospective studies.

Normal breast tissue implanted into athymic nude mice identifies biomarkers of the effects of human pregnancy levels of estrogen

We have generated a novel model system for the study of estrogen intervention in normal breast tissue. Nulliparous human breast tissue was implanted into immunocompromised nude mice and treated with high-dose estrogen to simulate the effects of pregnancy. Treatment of mice with human mid-pregnancy levels of 17beta-estradiol for a period of 4 weeks was followed by 4 weeks of withdrawal to mimic involution. Gene expression in the xenograft tissue was then analyzed by real-time reverse transcription-PCR to identify differences between treated and control tissues. Ten genes previously identified as altered by pregnancy in rodent models were found to be differentially expressed in human breast tissue with a > or =1.8-fold up-regulation of CDC42, TGFbeta3, DCN, KRT14, LTF, and AREG and a > or =0.7-fold down-regulation of STAT1, CTGF, IGF1, and VAMP1. Immunohistochemical analysis of archival paraffin-embedded adult premenopausal human breast tissue specimens identified a significantly lower level of expression of STAT1 (P < 0.05, Mann-Whitney U test) in parous compared with age-matched nulliparous tissue (median of 24% compared with 42% epithelial cells positive). We conclude that many of the pregnancy-induced breast cancer-protective changes observed in rodent models also occur in human breast tissue following intervention using human pregnancy levels of estrogen and that STAT1 expression is a potential biomarker of parity-induced breast cancer protection in the human breast.

Estrogen and progesterone receptor levels in nonneoplastic breast epithelium of breast cancer cases versus benign breast biopsy controls

BACKGROUND

Previous studies and biological mechanisms of carcinogenesis suggest that the steroid receptor content of benign breast epithelium may be related to breast cancer risk. The objective in this study was to compare the levels of estrogen receptor-alpha (ER) and progesterone receptor (PR) in nonneoplastic breast epithelium between breast cancer cases and biopsy controls.

METHODS

Between 1995 and 1997 at two sites (Women's College Hospital in Toronto and Kingston General Hospital), 667 women who were scheduled for diagnostic excisional breast biopsies completed a questionnaire providing personal information and agreed to allow analysis of routinely resected tissue. Histological slides with nonneoplastic epithelium were available for 101 cancer cases and 200 biopsy controls in Toronto and for 105 cancer cases and 119 controls in Kingston. Nonneoplastic epithelium was examined with immunohistochemical assays to determine the percent of epithelial cells staining for ER and PR. Unconditional logistic regression was used to calculate odds ratios (OR) stratified by study site.

RESULTS

The ER content of nonneoplastic tissue was higher in cases than biopsy controls in unadjusted analyses; after adjustment for age, however, a weak association remained in only one of the study sites. After adjustment for age, the PR content of nonneoplastic tissue was slightly lower in breast cancer cases than controls in one study site. Furthermore, this inverse association was confined to women with PR negative breast cancer in comparison to the controls. No interaction between ER and PR content of nonneoplastic tissue was observed in relation to the odds of having breast cancer.

CONCLUSION

The results of this study are consistent with only a slight indication of increased ER levels in nonneoplastic tissue in breast cancer cases relative to controls. This study contributes to the understanding of breast cancer by examining both ER and PR in nonneoplastic tissue. Limitations remain, however, such as the necessity of using as controls women with benign breast changes, difficulties in selecting the appropriate tissue for analysis, and tissue sampling concurrent to diagnosis.

Endocrinology of the wild and mutant BRCA1 gene and types of hormonal carcinogenesis

Information related to the BRCA1 gene has increasingly become a subject for analysis by endocrinologists. For example, it is hard to dismiss the fact that, in BRCA1 mutation carriers, tumors develop predominantly in such estrogen-dependent organs as the mammary glands and ovaries but not in the endometrium. Another characteristic feature is that although BRCA1 mutants and knock-downs are unable to inhibit the transcriptional activity of estrogen receptor-alpha, in BRCA1 mutation carriers breast cancers are often estrogen receptor-negative and originate from the basal rather than the luminal epithelium. The latter, together with other data, suggests that BRCA1-positive breast neoplasms could be considered to be a consequence of the genotoxic variant of hormonal carcinogenesis (that is, associated with DNA damaging rather then with pure hormonal/physiological properties of hormones or their derivatives). Of indisputable significance are the data demonstrating that knocking down of the BRCA1 gene is accompanied by aromatase overexpression and the abolishment of IGF-1 receptor expression suppression, thus increasing both steroid and insulin signaling. Importantly, the endocrine-genotoxic 'liberation' found upon transfer from the wild-type to the mutant BRCA1 provides grounds to regard BRCA1 as a modulator of endocrine-genotoxic switching (predominantly into a direction of DNA-damaging hormone effects) and also to ask whether this is a property of only this or some other tumor suppressor's.

Individualized preventive and therapeutic management of hereditary breast ovarian cancer syndrome

Life-saving, risk-reducing medical interventions are required for women with a BRCA1/2 mutation. Interventions comprise a four-stage approach that involves risk assessment, genetic counseling, gene-mutation analysis and medical intervention strategies. Genetic counseling should be offered at specialized familial breast-cancer clinics and gene-mutation analysis should be recommended on the basis of personal and family-history-based risk criteria. Prophylactic bilateral salpingo-oophorectomy appears to offer the optimal benefit-risk ratio compared with prophylactic bilateral mastectomy, chemoprevention, or intensified surveillance. Tamoxifen is an alternative approach only for BRCA2 mutation carriers. The comprehensive, clinical decision-making Ioannina algorithm provided here can facilitate the complex preventive strategic approach. Newly diagnosed BRCA1/2 carriers might benefit from extensive surgery and a specific pharmacological treatment, but data to support this strategy are limited. Microarray gene-expression studies show that breast tumors from BRCA1 carriers are predominantly of basal subtype (i.e. triple negative) and BRCA2 carriers are of luminal subtype (i.e. estrogen-receptor-positive). Although optimum management of women with familial susceptibility to breast and ovarian cancer has not yet been prospectively validated, data indicate substantial benefits when an individualized evidence-based prevention strategy is provided by an experienced team.

The predominant role of surgery in the prevention and new trends in the surgical treatment of women with BRCA1/2 mutations

BACKGROUND

Advances in understanding molecular and genetic mechanisms underlying cancer promise an "individualized" management of the disease. Women with a BRCA1 or BRCA2 germ-line mutation are at very high risk of breast and/or ovarian cancer. Because high-quality data are lacking from randomized trials, prevention strategies and treatment of patients with BRCA-associated breast cancer are complex.

METHODS

The data for this review were obtained by searching PubMed and Medline for articles about optimizing prevention and treating women with familial susceptibility to breast and ovarian cancer.

RESULTS

Prophylactic surgery is the rational approach for women who carry the BRCA mutation; chemoprevention and/or intensified surveillance represent alternative approaches. Prophylactic bilateral salpingo-oophorectomy is superior to bilateral prophylactic mastectomy. However, reaching a definitive clinical decision is complex, and several variables should be considered for an individualized approach. Accumulating data support the concept of more extensive surgery for newly diagnosed breast cancer in women with a BRCA mutation but new unbaised studies are needed for an evidence-based approach . Such patients treated with breast conservation therapy for early-stage breast cancer are at higher risk of contralateral breast cancer than noncarriers. Primary bilateral mastectomy could also be considered and discussed with these patients. Breast tumors from BRCA1 mutation carriers are predominantly of basal subtype (i.e., triple negative), and BRCA2 mutation carriers are of luminal subtype (i.e., estrogen receptor positive). Decisions on adjuvant treatment are based on estrogen receptor, progesterone receptor, and HER2 status.

CONCLUSIONS

The complex management of healthy women and breast cancer patients with familial susceptibility to breast and ovarian cancer requires an individualized prevention or treatment strategy by an experienced team.

Hereditary breast cancer: pathobiology, clinical translation, and potential for targeted cancer therapeutics

BRCA1 and BRCA2 breast cancers have distinct biological features as evidenced by histopathologic, immunohistochemical, gene expression profiling, and array-comparative genomic hybridization data. BRCA1 breast cancers may have a worse prognosis but may, however be amenable to treatment such as chemotherapy for small high-grade, lymph node negative breast cancers. Paradoxically, tamoxifen may provide effective adjuvant and chemopreventive therapy despite the predominantly negative estrogen receptor status of BRCA1 breast cancers. The distinctive biology of BRCA1 and BRCA2 breast cancers bodes well for the development of targeted cancer therapies. Cells with BRCA1 or BRCA2 loss of function are deficient in DNA double strand break repair and are sensitized to poly(ADP-ribose) polymerase (PARP) inhibitors, causing the persistence of DNA lesions which are usually repaired by homologous recombination and ultimately leading to apoptosis. The potentially high efficacy and low toxicity of poly(ADP-ribose) polymerase inhibitors presents an opportunity for targeted cancer therapeutics for BRCA1 and BRCA2 germline mutation carriers. Genotype-tailored chemoprevention may be feasible which could theoretically eliminate single cells that have sustained a second hit, before cancer progression takes place. If targeted cancer therapies emerge, it will become crucially important to identify BRCA carriers at the time of diagnosis for optimal therapy and to identify unaffected carriers for chemoprevention. If so, then to the extent that barriers in the recognition and referral of patients to genetic counseling cannot be surmounted, pathological and genomic methods to identify a BRCA1 or BRCA2 breast cancer profile will gain increasing clinical importance.

Risk factors for breast cancer characterized by the estrogen receptor alpha A908G (K303R) mutation

INTRODUCTION

Estrogen is important in the development of breast cancer, and its biological effects are mediated primarily through the two estrogen receptors alpha and beta. A point mutation in the estrogen receptor alpha gene, ESR1, referred to as A908G or K303R, was originally identified in breast hyperplasias and was reported to be hypersensitive to estrogen. We recently detected this mutation at a low frequency of 6% in invasive breast tumors of the Carolina Breast Cancer Study (CBCS).

METHODS

In this report, we evaluated risk factors for invasive breast cancer classified according to the presence or absence of the ESR1 A908G mutation in the CBCS, a population-based case-control study of breast cancer among younger and older white and African-American women in North Carolina. Of the 653 breast tumors evaluated, 37 were ESR1 A908G mutation-positive and 616 were mutation-negative.

RESULTS

ESR1 A908G mutation-positive breast cancer was significantly associated with a first-degree family history of breast cancer (odds ratio [OR] = 2.69, 95% confidence interval [CI] = 1.15 to 6.28), whereas mutation-negative breast cancer was not. Comparison of the two case subgroups supported this finding (OR = 2.65, 95% CI = 1.15 to 6.09). There was also the suggestion that longer duration of oral contraceptive (OC) use (OR = 3.73, 95% CI = 1.16 to 12.03; Ptrend = 0.02 for use of more than 10 years) and recent use of OCs (OR = 3.63, 95% CI = 0.80 to 16.45; Ptrend = 0.10 for use within 10 years) were associated with ESR1 A908G mutation-positive breast cancer; however, ORs for comparison of the two case subgroups were not statistically significant. Hormone replacement therapy use was inversely correlated with mutation-negative breast cancer, but the effect on mutation-positive cancer was unclear due to the small number of postmenopausal cases whose tumors carried the mutation. Mutation-negative breast cancer was associated with several reproductive factors, including younger age at menarche (OR = 1.46, 95% CI = 1.09 to 1.94) and greater total estimated years of ovarian function (OR = 1.82, 95% CI = 1.21 to 2.74).

CONCLUSION

These preliminary results suggest that OCs may interact with the ESR1 A908G mutant receptor to drive the development of some breast tumors.