Androgen receptor expression in breast cancer in relation to molecular phenotype: results from the Nurses' Health Study

A phase II trial of abiraterone acetate plus prednisone in patients with triple-negative androgen receptor positive locally advanced or metastatic breast cancer (UCBG 12-1)

BACKGROUND

Several expression array studies identified molecular apocrine breast cancer (BC) as a subtype that expresses androgen receptor (AR) but not estrogen receptor α. We carried out a multicentre single-arm phase II trial in women with AR-positive, estrogen, progesterone receptor and HER2-negative (triple-negative) metastatic or inoperable locally advanced BC to assess the efficacy and safety of abiraterone acetate (AA) plus prednisone.

PATIENTS AND METHODS

Patients with a metastatic or locally advanced, centrally reviewed, triple-negative and AR-positive (≥10% by immunohistochemistry, IHC) BC were eligible. Any number of previous lines of chemotherapy was allowed. AA (1000 mg) was administered once a day with prednisone (5 mg) twice a day until disease progression or intolerance. The primary end point was clinical benefit rate (CBR) at 6 months defined as the proportion of patients presenting a complete response (CR), partial response (PR) or stable disease (SD) ≥6 months. Secondary end points were objective response rate (ORR), progression-free survival (PFS) and safety.

RESULTS

One hundred and forty-six patients from 27 centres consented for IHC central review. Of the 138 patients with sufficient tissue available, 53 (37.6%) were AR-positive and triple-negative, and 34 of them were included from July 2013 to December 2014. Thirty patients were eligible and evaluable for the primary end point. The 6-month CBR was 20.0% [95% confidence interval (CI) 7.7%-38.6%], including 1 CR and 5 SD ≥6 months, 5 of them still being under treatment at the time of analysis (6.4+, 9.2+, 14.5+, 17.6+, 23.4+ months). The ORR was 6.7% (95% CI 0.8%-22.1%). The median PFS was 2.8 months (95% CI 1.7%-5.4%). Fatigue, hypertension, hypokalaemia and nausea were the most common drug-related adverse events; the majority of them being grade 1 or 2.

CONCLUSIONS

AA plus prednisone treatment is beneficial for some patients with molecular apocrine tumours and five patients are still on treatment.

CLINICALTRIALSGOV

NCT01842321.

Postmenopausal mammographic breast density and subsequent breast cancer risk according to selected tissue markers

BACKGROUND

This study aimed to determine if associations of pre-diagnostic percent breast density, absolute dense area, and non-dense area with subsequent breast cancer risk differ by the tumour's molecular marker status.

METHODS

We included 1010 postmenopausal women with breast cancer and 2077 matched controls from the Nurses' Health Study (NHS) and the Nurses' Health Study II (NHS II) cohorts. Breast density was estimated from digitised film mammograms using computer-assisted thresholding techniques. Information on breast cancer risk factors was obtained prospectively from biennial questionnaires. Polychotomous logistic regression was used to assess associations of breast density measures with tumour subtypes by the status of selected tissue markers. All tests of statistical significance were two sided.

RESULTS

The association of percent density with breast cancer risk appeared to be stronger in ER- as compared with ER+ tumours, but the difference did not reach statistical significance (density ⩾50% vs <10% odds ratio (OR)=3.06, 95% confidence interval (CI) 2.17-4.32 for ER+; OR=4.61, 95% CI 2.36-9.03 for ER-, Pheterogeneity=0.08). Stronger positive associations were found for absolute dense area and CK5/6- and EGFR- as compared with respective marker-positive tumours (Pheterogeneity=0.002 and 0.001, respectively). Stronger inverse associations of non-dense area with breast cancer risk were found for ER- as compared with ER+ tumours (Pheterogeneity=0.0001) and for AR+, CK5/6+, and EGFR+ as compared with respective marker-negative tumours (Pheterogeneity=0.03, 0.005, and 0.009, respectively). The associations of density measures with breast cancer did not differ by progesterone receptor and human epidermal growth factor receptor 2 status.

CONCLUSIONS

Breast density influences the risk of breast cancer subtypes by potentially different mechanisms.

Androgen Receptor Biology in Triple Negative Breast Cancer: a Case for Classification as AR+ or Quadruple Negative Disease

Triple negative breast cancer (TNBC) is an aggressive breast cancer subtype that lacks estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 (HER2) amplification. Due to the absence of these receptors, TNBC does not respond to traditional endocrine or HER2-targeted therapies that improve patient prognosis in other breast cancer subtypes. TNBC has a poor prognosis, and currently, there are no effective targeted therapies. Some TNBC tumors express androgen receptor (AR) and may benefit from AR-targeted therapies. Here, we review the literature on AR in TNBC and propose that TNBC be further sub-classified as either AR+ TNBC or quadruple negative breast cancer since targeting AR may represent a viable therapeutic option for a subset of TNBC.

Steroid hormones, steroid receptors, and breast cancer stem cells

The ovarian hormones progesterone and estrogen play important roles in breast cancer etiology, proliferation, and treatment. Androgens may also contribute to breast cancer risk and progression. In recent years, significant advances have been made in defining the roles of these steroid hormones in stem cell homeostasis in the breast. Stem cells are potential origins of breast cancer and may dictate tumor phenotype. At least a portion of breast cancers are proposed to be driven by cancer stem cells (CSCs), cells that mimic the self-renewing and repopulating properties of normal stem cells, and can confer drug resistance. Progesterone has been identified as the critical hormone regulating normal murine mammary stem cell (MaSC) populations and normal human breast stem cells. Synthetic progestins increase human breast cancer risk; one theory speculates that this occurs through increased stem cells. Progesterone treatment also increases breast CSCs in established breast cancer cell lines. This is mediated in part through progesterone regulation of transcription factors, signal transduction pathways, and microRNAs. There is also emerging evidence that estrogens and androgens can regulate breast CSC numbers. The evolving concept that a breast CSC phenotype is dynamic and can be influenced by cell signaling and external cues emphasizes that steroid hormones could be crucial players in controlling CSC number and function. Here we review recent studies on steroid hormone regulation of breast CSCs, and discuss mechanisms by which this occurs.

Targeting the androgen receptor in prostate and breast cancer: several new agents in development

Prostate cancer (PCa) and breast cancer (BCa) share similarities as hormone-sensitive cancers with a wide heterogeneity of both phenotype and biology. The androgen receptor (AR) is a hormone receptor involved in both benign and malignant processes. Targeting androgen synthesis and the AR pathway has been and remains central to PCa therapy. Recently, there has been increased interest in the role of the AR in BCa development and growth, with results indicating AR co-expression with estrogen, progesterone, and human epidermal growth factor receptors, across all intrinsic subtypes of BCa. Targeting the AR axis is an evolving field with novel therapies in development which may ultimately be applicable to both tumor types. In this review, we offer an overview of available agents which target the AR axis in both PCa and BCa and provide insights into the novel drugs in development for targeting this signaling pathway.

Multiple molecular subtypes of triple-negative breast cancer critically rely on androgen receptor and respond to enzalutamide in vivo

Triple-negative breast cancer (TNBC) has the lowest 5-year survival rate of invasive breast carcinomas, and currently there are no approved targeted therapies for this aggressive form of the disease. The androgen receptor (AR) is expressed in up to one third of TNBC and we find that all AR(+) TNBC primary tumors tested display nuclear localization of AR, indicative of transcriptionally active receptors. While AR is most abundant in the "luminal AR (LAR)" molecular subtype of TNBC, here, for the first time, we use both the new-generation anti-androgen enzalutamide and AR knockdown to demonstrate that the other non-LAR molecular subtypes of TNBC are critically dependent on AR protein. Indeed, AR inhibition significantly reduces baseline proliferation, anchorage-independent growth, migration, and invasion and increases apoptosis in four TNBC lines (SUM159PT, HCC1806, BT549, and MDA-MB-231), representing three non-LAR TNBC molecular subtypes (mesenchymal-like, mesenchymal stem-like, and basal-like 2). In vivo, enzalutamide significantly decreases viability of SUM159PT and HCC1806 xenografts. Furthermore, mechanistic analysis reveals that AR activation upregulates secretion of the EGFR ligand amphiregulin (AREG), an effect abrogated by enzalutamide in vitro and in vivo. Exogenous AREG partially rescues the effects of AR knockdown on proliferation, migration, and invasion, demonstrating that upregulation of AREG is one mechanism by which AR influences tumorigenicity. Together, our findings indicate that non-LAR subtypes of TNBC are AR dependent and, moreover, that enzalutamide is a promising targeted therapy for multiple molecular subtypes of AR(+) TNBC.

Dietary lignan intake and androgen receptor expression in breast tumors

PURPOSE

Lignans, a class of phytoestrogen commonly found in the Western diet, have been linked to decreased breast cancer risks in epidemiologic studies. Similar to estrogen receptors, the androgen receptor (AR), a prognostic factor in breast tumors, may be affected by lignans. However, few studies have investigated this link in the context of breast cancer etiology. We evaluated the relationship between dietary lignan intake and AR expression in incident breast tumors.

METHODS

Tumor tissue, epidemiological, and clinical data were collected from 216 women with incident, primary, histologically confirmed breast cancer enrolled in the Roswell Park Cancer Institute (RPCI) Data Bank and BioRepository (DBBR). On average, three tumor cores from each participant were assembled into a tissue micro array. After immunohistochemical staining, a trained RPCI pathologist determined AR status of each core. Lignan intake was calculated from a food frequency questionnaire collected upon enrollment into the DBBR.

RESULTS

We observed a weak positive association between dietary lignans and AR expression [β (SE) 27.6 (17.0), p 0.10], and there was no significant difference in lignan intake across categories of AR expression (p = 0.09, R (2) = 0.35).

CONCLUSION

Our results do not support a clear relationship between dietary lignan intake and AR expression. This investigation is the first, to our knowledge, to examine dietary lignan intake and AR expression in breast tumors. Further research is needed within a larger, more representative sample to determine whether lignan intake is truly associated with AR expression.

FABP7 and HMGCS2 are novel protein markers for apocrine differentiation categorizing apocrine carcinoma of the breast

Apocrine carcinoma of the breast is a distinctive malignancy with unique morphological and molecular features, generally characterized by being negative for estrogen and progesterone receptors, and thus not electable for endocrine therapy. Despite the fact that they are morphologically distinct from other breast lesions, no standard molecular criteria are currently available for their diagnosis. Using gel-based proteomics in combination with mass spectrometry and immunohistochemistry we have identified two novel markers, HMGCS2 and FABP7 that categorize the entire breast apocrine differentiation spectrum from benign metaplasia and cysts to invasive stages. Expression of HMGCS2 and FABP7 is strongly associated with apocrine differentiation; their expression is retained by most invasive apocrine carcinomas (IAC) showing positive immunoreactivity in 100% and 78% of apocrine carcinomas, respectively, as compared to non-apocrine tumors (16.7% and 6.8%). The nuclear localization of FABP7 in tumor cells was shown to be associated with more aggressive stages of apocrine carcinomas. In addition, when added to the panel of apocrine biomarkers previously reported by our group: 15-PGDH, HMGCR and ACSM1, together they provide a signature that may represent a golden molecular standard for defining the apocrine phenotype in the breast. Moreover, we show that combining HMGCS2 to the steroidal profile (HMGCS2+/Androgen Receptor (AR)+/Estrogen Receptor(ER)-/Progesteron Receptor (PR)- identifies IACs with a greater sensitivity (79%) as compared with the steroidal profile (AR+/ER-/PR-) alone (54%). We have also presented a detailed immunohistochemical analysis of breast apocrine lesions with a panel of antibodies against proteins which correspond to 10 genes selected from published transcriptomic signatures that currently characterize molecular apocrine subtype and shown that except for melanophilin that is overexpressed in benign apocrine lesions, these proteins were not specific for morphological apocrine differentiation in breast.

Claudin 4 expression in triple-negative breast cancer: correlation with androgen receptors and Ki-67 expression

Breast cancer is the most common malignancy in women and the leading cause of cancer mortality worldwide. Triple-negative breast cancer (TNBC) is an important phenotype of breast cancer that accounts for a relatively small number of breast cancer cases but still represent a focus of increasing interest at the clinical, biological, and epidemiological level. Claudins are the major component of the tight junction, and only a few studies have addressed the role of claudins in breast cancer, especially TNBC. Androgen receptors (ARs), as members of the nuclear receptor superfamily, are known to be involved in a complex network of signaling pathways that collectively regulate cell proliferation. However, roles of AR in breast cancer development and progression have not been very clearly understood. The proliferation marker Ki-67 has been confirmed as an independent predictive and prognostic factor in early breast cancer. The aims of this study are to identify the clinicopathologic associations and prognostic value of claudin 4 expression in TNBC and to correlate claudin 4 expression with AR status and Ki-67 expression. Paraffin blocks obtained from 56 female patients with triple-negative primary invasive ductal breast carcinomas were analyzed for claudin 4, AR, and Ki-67 immunohistochemical expression. High levels of claudin 4 expression were detected in 66.1% of TNBC cases. There was a significant positive correlation with age, tumor size, grade, nodal status, metastasis, and Ki-67 expression (all P < .05) and negative correlation with AR status (P < .001). Androgen receptor showed positivity in 29 cases (51.78%). There was a statistical negative correlation with the all the studied clinicopathologic parameters, claudin 4 and Ki-67 expression. High claudin 4 expression, negative AR expression, and high Ki-67 index would provide a strong prognostic power to differentiate the patients with worse outcome among TNBC patients. Moreover, target treatment for TNBC cells expressing claudin 4 or AR enriched would be valuable for future therapies.

Coagulation factor VII is regulated by androgen receptor in breast cancer

Androgen receptor (AR) is widely expressed in breast cancer; however, there is limited information on the key molecular functions and gene targets of AR in this disease. In this study, gene expression data from a cohort of 52 breast cancer cell lines was analyzed to identify a network of AR co-expressed genes. A total of 300 genes, which were significantly enriched for cell cycle and metabolic functions, showed absolute correlation coefficients (|CC|) of more than 0.5 with AR expression across the dataset. In this network, a subset of 35 "AR-signature" genes were highly co-expressed with AR (|CC|>0.6) that included transcriptional regulators PATZ1, NFATC4, and SPDEF. Furthermore, gene encoding coagulation factor VII (F7) demonstrated the closest expression pattern with AR (CC=0.716) in the dataset and factor VII protein expression was significantly associated to that of AR in a cohort of 209 breast tumors. Moreover, functional studies demonstrated that AR activation results in the induction of factor VII expression at both transcript and protein levels and AR directly binds to a proximal region of F7 promoter in breast cancer cells. Importantly, AR activation in breast cancer cells induced endogenous factor VII activity to convert factor X to Xa in conjunction with tissue factor. In summary, F7 is a novel AR target gene and AR activation regulates the ectopic expression and activity of factor VII in breast cancer cells. These findings have functional implications in the pathobiology of thromboembolic events and regulation of factor VII/tissue factor signaling in breast cancer.

Association of H3K9me3 and H3K27me3 repressive histone marks with breast cancer subtypes in the Nurses' Health Study

Repressive histone tail modifications have been associated with molecular breast cancer subtypes. We investigated whether histone 3 lysine 9 trimethylation (H3K9me3) and histone 3 lysine 27 trimethylation (H3K27me3) were associated with tumor features and subtypes while adjusting for prospectively collected reproductive and lifestyle breast cancer risk factors. We have tissue microarray data with immunohistochemical marker information on 804 incident cases of invasive breast cancer diagnosed from 1976-2000 in the Nurses' Health Study. Tissue microarray sections were stained for global H3K9me3 and H3K27me3, and scored into four categories. Multivariate odds ratios (OR) and 95 % confidence intervals (CI) were calculated using logistic regression models for tumor features and subtypes, adjusting for breast cancer risk factors. While there were no significant associations between H3K9me3 and tumor features, H3K27me3 was significantly associated with lower grade tumors compared to high grade tumors in the multivariate model (OR = 1.95, 95 % CI 1.35-2.81, p = 0.0004). H3K27me3 was suggestively associated with estrogen receptor-positive (ER+) tumors (OR = 1.47, 95 % CI 0.97-2.23, p = 0.07). In subtype analyses, H3K27me3 was positively associated with the luminal A subtype compared to all other subtypes (OR = 1.42, 95 % CI 1.14-1.77, p = 0.002), and was inversely associated with HER2-type (OR = 0.58, 95 % CI 0.37-0.91, p = 0.02) and basal-like breast cancer (OR = 0.52, 95 % CI 0.36-0.76, p = 0.0006). In the largest immunohistochemical examination of H3K9me3 and H3K27me3 in breast cancer, we found that H3K27me3 positivity, but not H3K9me3, was associated with lower grade tumors and the luminal A subtype after adjusting for reproductive and lifestyle breast cancer risk factors.

Complexities of androgen receptor signalling in breast cancer

While the clinical benefit of androgen-based therapeutics in breast cancer has been known since the 1940s, we have only recently begun to fully understand the mechanisms of androgen action in breast cancer. Androgen signalling pathways can have either beneficial or deleterious effects in breast cancer depending on the breast cancer subtype and intracellular context. This review discusses our current knowledge of androgen signalling in breast cancer, including the relationship between serum androgens and breast cancer risk, the prognostic significance of androgen receptor (AR) expression in different breast cancer subtypes and the downstream molecular pathways mediating androgen action in breast cancer cells. Intracrine androgen metabolism has also been discussed and proposed as a potential mechanism that may explain some of the reported differences regarding dichotomous androgen actions in breast cancers. A better understanding of AR signalling in this disease is critical given the current resurgence in interest in utilising contemporary AR-directed therapies for breast cancer and the need for biomarkers that will accurately predict clinical response.

Expression of androgen receptor in inflammatory breast cancer and its clinical relevance

BACKGROUND

Inflammatory breast cancer (IBC) is characterized by an aggressive clinical course with early metastasis and frequent resistance to conventional therapies. Identifying a novel therapeutic approach may improve the prognosis for patients with IBC. Because androgen receptor (AR)-expressing tumors may be targeted by anti-AR therapy, the authors examined the prevalence of AR expression in IBC tumors and explored its clinical relevance.

METHODS

Tissue microarrays of 88 IBC tumors were stained immunohistochemically with monoclonal antibody against AR, and the results were correlated with clinicopathologic parameters and survival outcomes.

RESULTS

The median follow-up was 10.8 years. AR was positive in 39% of the IBC tumors and in approximately one-third of estrogen receptor (ER)-negative and progesterone receptor (PR)-negative tumors. AR positivity was significantly associated with lymphovascular invasion (P = .01) but not with other clinicopathologic parameters. There was a trend toward an association between AR expression and PR expression (P = .07). In univariate survival analysis, patients who had AR-negative/ER-negative tumors had significantly worse overall survival (P = .03) and disease-specific survival (P = .04) than patients who had tumors with other combinations of AR/ER status.

CONCLUSIONS

AR expression was common in IBC tumors, and AR positivity was significantly associated with lymphovascular invasion. Patients who had AR-negative/ER-negative tumors had the worst survival outcomes. Further study with a larger series will be required to delineate the biologic mechanisms of AR and their clinical significance in IBC tumors.

Importance of Breast Cancer Subtype in the Development of Androgen Receptor Directed Therapy

The androgen receptor (AR) has re-emerged as a potential therapeutic target in breast cancer. This stems from recent progress made in preclinical models, that have recognized important differences in the effect of AR expression on patient outcomes among different breast cancer subtypes. In parallel, the clinical development of new generations of AR directed therapies for prostate cancer has begun to mature. The availability of these new agents has translated into new trials to treat breast cancer. It is critical that studies of the effect of AR expression and signaling in breast cancer be context and subtype specific in order to successfully target AR signalling as a therapeutic strategy for breast cancer. We will review developments in preclinical studies, and recent clinical trials targeting AR in breast cancer.

Loss of androgen receptor expression predicts early recurrence in triple-negative and basal-like breast cancer

Treatment of triple-negative invasive breast cancers, defined by the absence of estrogen and progesterone receptors and c-erbB2 expression, remains challenging. Androgen receptor, a member of the nuclear receptor superfamily that is involved in signaling pathways regulating cell proliferation, has been implicated in breast tumorigenesis. We immunohistochemically examined the expression of androgen receptor, basal markers (CK14, 34βE12) and EGFR in 699 triple-negative invasive breast cancers in tissue microarrays using the streptavidin-biotin method, and correlated the findings with clinical outcome. Positive androgen receptor expression was defined as staining of 1% or more of tumor cell nuclei. Survival outcomes were estimated with the Kaplan-Meier method and compared between groups with log-rank statistics. Cox proportional hazards models were used to determine the effect of androgen receptor on survival outcomes. Immunohistochemical positivity was observed in 38% of tumors, with the proportion of stained tumor cells ranging from 1 to 95% (mean 29%, median 10%). Androgen receptor expression was inversely associated with histologic grade and mitotic score. CK14, 34βE12 and EGFR confirmed 85% of cases to be basal-like, without significant association of basal-like phenotype with androgen receptor expression. Disease-free survival was significantly better in androgen receptor-positive triple-negative breast cancer, with a trend for improved overall survival. Decreased recurrence likelihood in both triple-negative and basal-like tumors (hazard ratio, 0.704; 95% confidence intervals, 0.498-0.994; P=0.0464; and hazard ratio, 0.675; 95% confidence intervals, 0.468-0.974; P=0.0355, respectively) was noted within 5 years of diagnosis but not thereafter. Our study suggests that loss of androgen receptor in triple-negative breast cancers augurs a worse prognosis, including those with basal-like features. More work in elucidating its relationship with mechanisms of progression, as well as trials of targeted treatment for androgen receptor-expressing triple-negative tumors, needs to be performed.

Subtype classification for prediction of prognosis of breast cancer from a biomarker panel: correlations and indications

Background

Hormone receptors, including the estrogen receptor and progesterone receptor, human epidermal growth factor receptor 2 (HER2), and other biomarkers like Ki67, epidermal growth factor receptor (EGFR, also known as HER1), the androgen receptor, and p53, are key molecules in breast cancer. This study evaluated the relationship between HER2 and hormone receptors and explored the additional prognostic value of Ki67, EGFR, the androgen receptor, and p53.

Methods

Quantitative determination of HER2 and EGFR was performed in 240 invasive breast cancer tissue microarray specimens using quantum dot (QD)-based nanotechnology. We identified two subtypes of HER2, ie, high total HER2 load (HTH2) and low total HER2 load (LTH2), and three subtypes of hormone receptor, ie, high hormone receptor (HHR), low hormone receptor (LHR), and no hormone receptor (NHR). Therefore, breast cancer patients could be divided into five subtypes according to HER2 and hormone receptor status. Ki67, p53, and the androgen receptor were determined by traditional immunohistochemistry techniques. The relationship between hormone receptors and HER2 was investigated and the additional value of Ki67, EGFR, the androgen receptor, and p53 for prediction of 5-year disease-free survival was assessed.

Results

In all patients, quantitative determination showed a statistically significant (P<0.001) negative correlation between HER2 and the hormone receptors and a significant positive correlation (P<0.001) between the estrogen receptor and the progesterone receptor (r=0.588), but a significant negative correlation (P<0.001, r=−0.618) with the HHR subtype. There were significant differences between the estrogen receptor, progesterone receptor, and HER2 subtypes with regard to total HER2 load and hormone receptor subtypes. The rates of androgen receptor and p53 positivity were 46.3% and 57.0%, respectively. Other than the androgen receptor, differences in expression of Ki67, EGFR, and p53 did not achieve statistical significance (P>0.05) between the five subtypes. EGFR and Ki67 had prognostic significance for 5-year disease-free survival in univariate analysis, but the androgen receptor and p53 did not. Multivariate analysis identified that EGFR expression had predictive significance for 5-year disease-free survival in hormone-receptor positive patients and in those with the lymph node-positive breast cancer subtype.

Conclusion

Hormone receptor expression was indeed one of the molecular profiles in the subtypes identified by quantitative HER2 and vice versa. EGFR status may provide discriminative prognostic information in addition to HER2 and hormone receptor status, and should be integrated into routine practice to help formulate more specific prediction of the prognosis and appropriate individualized treatment.

Taxonomy of breast cancer based on normal cell phenotype predicts outcome

Accurate classification is essential for understanding the pathophysiology of a disease and can inform therapeutic choices. For hematopoietic malignancies, a classification scheme based on the phenotypic similarity between tumor cells and normal cells has been successfully used to define tumor subtypes; however, use of normal cell types as a reference by which to classify solid tumors has not been widely emulated, in part due to more limited understanding of epithelial cell differentiation compared with hematopoiesis. To provide a better definition of the subtypes of epithelial cells comprising the breast epithelium, we performed a systematic analysis of a large set of breast epithelial markers in more than 15,000 normal breast cells, which identified 11 differentiation states for normal luminal cells. We then applied information from this analysis to classify human breast tumors based on normal cell types into 4 major subtypes, HR0-HR3, which were differentiated by vitamin D, androgen, and estrogen hormone receptor (HR) expression. Examination of 3,157 human breast tumors revealed that these HR subtypes were distinct from the current classification scheme, which is based on estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Patient outcomes were best when tumors expressed all 3 hormone receptors (subtype HR3) and worst when they expressed none of the receptors (subtype HR0). Together, these data provide an ontological classification scheme associated with patient survival differences and provides actionable insights for treating breast tumors.

Role of the androgen receptor in breast cancer and preclinical analysis of enzalutamide

Introduction

The androgen receptor (AR) is widely expressed in breast cancers and has been proposed as a therapeutic target in estrogen receptor alpha (ER) negative breast cancers that retain AR. However, controversy exists regarding the role of AR, particularly in ER + tumors. Enzalutamide, an AR inhibitor that impairs nuclear localization of AR, was used to elucidate the role of AR in preclinical models of ER positive and negative breast cancer.

Methods

We examined nuclear AR to ER protein ratios in primary breast cancers in relation to response to endocrine therapy. The effects of AR inhibition with enzalutamide were examined in vitro and in preclinical models of ER positive and negative breast cancer that express AR.

Results

In a cohort of 192 women with ER + breast cancers, a high ratio of AR:ER (≥2.0) indicated an over four fold increased risk for failure while on tamoxifen (HR = 4.43). The AR:ER ratio had an independent effect on risk for failure above ER % staining alone. AR:ER ratio is also an independent predictor of disease-free survival (HR = 4.04, 95% CI: 1.68, 9.69; p = 0.002) and disease specific survival (HR = 2.75, 95% CI: 1.11, 6.86; p = 0.03). Both enzalutamide and bicalutamide inhibited 5-alpha-dihydrotestosterone (DHT)-mediated proliferation of breast cancer lines in vitro; however, enzalutamide uniquely inhibited estradiol (E2)-mediated proliferation of ER+/AR + breast cancer cells. In MCF7 xenografts (ER+/AR+) enzalutamide inhibited E2-driven tumor growth as effectively as tamoxifen by decreasing proliferation. Enzalutamide also inhibited DHT- driven tumor growth in both ER positive (MCF7) and negative (MDA-MB-453) xenografts, but did so by increasing apoptosis.

Conclusions

AR to ER ratio may influence breast cancer response to traditional endocrine therapy. Enzalutamide elicits different effects on E2-mediated breast cancer cell proliferation than bicalutamide. This preclinical study supports the initiation of clinical studies evaluating enzalutamide for treatment of AR⁺ tumors regardless of ER status, since it blocks both androgen- and estrogen- mediated tumor growth.

Androgen receptor decreases CMYC and KRAS expression by upregulating let-7a expression in ER-, PR-, AR+ breast cancer

It is generally known that the decision to use anti-estrogen therapy is based on the expression of estrogen and progesterone receptors in breast cancers. Recent studies have shown that androgen receptor (AR) is frequently expressed in ER-, PR- breast cancer and plays an important role in the prognosis of breast cancer patients. Furthermore, AR can increase the global expression of microRNAs, post-transcriptional gene regulators that play a crucial role in the initiation and progression of breast cancer. In this study, we investigated the functions and relations of AR, related miRNAs and target proteins in ER-, PR-, AR+ breast cancer. The results showed that androgen-induced AR activating signal directly upregulates let-7a expression, downregulates CMYC and KRAS protein expression, and inhibits cell proliferation in ER-, PR-, AR+ breast cancer cells. Overexpression of let-7a inhibits cell proliferation and downregulates CMYC and KRAS protein expression, whereas inhibition of let-7a expression by specific antisense oligonucleo-tides increases cell growth and upregulates CMYC and KRAS protein expression. We performed in situ hybridization for let-7a and immunohistochemical staining for CMYC and KRAS using sequential sections obtained from surgically-resected breast cancer tissues and observed an inverse correlation between the staining pattern of let-7a and its target proteins. Androgen-induced AR activating signal upregulates let-7a that targets CMYC and KRAS and contributes to ER-, PR-, AR+ breast cancer pathogenesis. Elucidation of this pathway will help develop new therapies.

Androgen receptor-positive triple negative breast cancer: a unique breast cancer subtype

BACKGROUND

The significance of androgen receptor (AR) expression in triple-negative breast cancer (TNBC) is unclear, and published studies so far have been inconclusive.

METHODS

A tissue microarray was constructed using tissue obtained from 119 patients with primary TNBC and stained for AR expression. Other tissue types obtained included recurrent TNBC, normal breast tissue, adjacent ductal carcinoma-in situ (DCIS), lymph node (LN) and distant metastases. Positive AR expression was defined as ≥10% nuclear staining.

RESULTS

Epithelial tissue was present and evaluable in 94 TNBC patients with a total of 177 tissue cores. AR expression in TNBC was 22 of 94 (23%). AR expression was higher in normal breast tissue (88%) and adjacent DCIS (73% overall). All LN metastases from AR-positive TNBC patients were also AR positive; in addition, no AR-negative TNBC patient had AR-positive LNs. AR expression was associated with older patient age (63 vs. 57 years, respectively, p = 0.051) and LN metastases (p = 0.033). Locoregional recurrence and overall/disease-specific survival were similar between AR-positive and AR-negative patients, although AR-positive patients had more advanced disease. On multivariate analysis, the presence of LN metastases was associated with poorer recurrence-free survival in AR-positive patients (hazard ratio, 4.34) (p = 0.031).

CONCLUSIONS

The AR is expressed in normal breast tissue, and expression decreases with advancement to DCIS and invasive cancer. AR-positive TNBC was more common in older patients and had a higher propensity for LN metastases. AR-positive TNBC may represent a breast cancer subtype with unique features that may be amenable to treatment with alternative targeted therapies.

Phase II trial of bicalutamide in patients with androgen receptor-positive, estrogen receptor-negative metastatic Breast Cancer

PURPOSE

Patients with hormone receptor-negative breast cancer generally do not benefit from endocrine-targeted therapies. However, a subset with androgen receptor (AR) expression is predicted to respond to antiandrogen therapies. This phase II study explored bicalutamide in AR-positive, estrogen receptor (ER), and progesterone receptor (PgR)-negative metastatic breast cancer.

EXPERIMENTAL DESIGN

Tumors from patients with ER/PgR-negative advanced breast cancer were tested centrally for AR [immunohistochemistry (IHC) > 10% nuclear staining considered positive]. If either the primary or a metastatic site was positive, patients were eligible to receive the AR antagonist bicalutamide at a dose of 150 mg daily. Clinical benefit rate (CBR), the primary endpoint, was defined as the total number of patients who show a complete response (CR), partial response (PR), or stable disease (SD) > 6 months; secondary endpoints included progression-free survival (PFS) and toxicity. Correlative studies included measurement of circulating endocrine markers and IHC surrogates for basal-like breast cancer.

RESULTS

Of 424 patients with ER/PgR-negative breast cancer, 12% tested AR-positive. The 6-month CBR was 19% [95% confidence interval (CI), 7%-39%] for bicalutamide. The median PFS was 12 weeks (95% CI, 11-22 weeks). Bicalutamide was well-tolerated with no grade 4/5 treatment-related adverse events observed.

CONCLUSION

AR was expressed in 12% of patients with ER/PgR-negative breast cancer screened for this trial. The CBR of 19% observed with bicalutamide shows proof of principle for the efficacy of minimally toxic androgen blockade in a select group of patients with ER/PgR-negative, AR-positive breast cancer.

Molecular apocrine breast cancers are aggressive estrogen receptor negative tumors overexpressing either HER2 or GCDFP15

Introduction

Molecular apocrine (MA) tumors are estrogen receptor (ER) negative breast cancers characterized by androgen receptor (AR) expression. We analyzed a group of 58 transcriptionally defined MA tumors and proposed a new tool to identify these tumors.

Methods

We performed quantitative reverse transcription PCR (qRT-PCR) for ESR1, AR, FOXA1 and AR-related genes, and immunohistochemistry (IHC) for ER, PR, Human Epidermal Growth Factor Receptor 2 (HER2), CK5/6, CK17, EGFR, Ki67, AR, FOXA1 and GCDFP15 and we analyzed clinical features.

Results

MA tumors were all characterized by ESR1(-) AR(+) FOXA1(+) and AR-related genes positive mRNA profile. IHC staining on these tumors showed 93% ER(-), only 58% AR(+) and 90% FOXA1(+). 67% and 57% MA tumors were HER2(3+) and GCDFP15(+), respectively. Almost all MA tumors (94%) had the IHC signature HER2(3+) or GCDFP15(+) but none of the 13 control basal-like (BL) tumors did. Clinically, MA tumors were rather aggressive, with poor prognostic factors.

Conclusion

MA tumors could be better defined by their qRT-PCR-AR profile than by AR IHC. In addition, we found that HER2 or GCDFP15 protein overexpression is a sensitive and specific tool to differentiate MA from BL in the context of ER negative tumors. A composite molecular and IHC signature could, therefore, help to identify MA tumors in daily practice.

Molecular imaging for monitoring treatment response in breast cancer patients

Currently, tumour response following drug treatment is based on measurement of anatomical size changes. This is often done according to Response Evaluation Criteria in Solid Tumours (RECIST) and is generally performed every 2-3 cycles. Bone metastases, being the most common site of distant metastases in breast cancer, are not measurable by RECIST. The standard response measurement provides no insight in changes of molecular characteristics. In the era of targeted medicine, knowledge of specific molecular tumour characteristics becomes more important. A potential way to assess this is by means of molecular imaging. Molecular imaging can visualise general tumour processes, such as glucose metabolism with (18)F-fluorodeoxyglucose ((18)F-FDG) and DNA synthesis with (18)F-fluorodeoxythymidine ((18)F-FLT). In addition, an increasing number of more specific targets, such as hormone receptors, growth factor receptors, and growth factors can be visualised. In the future molecular imaging may thus be of value for personalised treatment-selection by providing insight in the expression of these drug targets. Additionally, when molecular changes can be detected early during therapy, this may serve as early predictor of response. However, in order to define clinical utility of this approach results from (ongoing) clinical trials is required. In this review we summarise the potential role of molecular imaging of general tumour processes as well as hormone receptors, growth factor receptors, and tumour micro-environment for predicting and monitoring treatment response in breast cancer patients.

Human epidermal growth factor receptor-2-positive breast cancer: does estrogen receptor status define two distinct subtypes?

BACKGROUND

Human epidermal growth factor receptor-2 (HER2) overexpression occurs in ∼20% of breast cancers and has historically been associated with decreased survival. Despite substantial improvements in clinical outcomes, particularly with the emergence of HER2-targeted therapy, a substantial minority of patients still relapses, and progression is inevitable in metastatic disease. Accumulating data indicate that HER2-positive disease is itself a heterogeneous entity.

METHODS AND RESULTS

In this article, we qualitatively review the data supporting the classification of HER2-positive disease as at least two separate entities, distinguished by estrogen receptor (ER) status. We summarize differences in clinical outcomes, including response to neoadjuvant therapy, timing and patterns of dissemination, efficacy of therapy in the metastatic setting and survival outcomes.

CONCLUSIONS

The collective data are sufficiently strong at this point to propose that ER status defines two distinct subtypes within HER2-positive breast cancer, and we highlight the implications of this knowledge in future research, including understanding of the basic biology of HER2-positive breast cancer and the design of future clinical trials.

Frequent copy number gains at 1q21 and 1q32 are associated with overexpression of the ETS transcription factors ETV3 and ELF3 in breast cancer irrespective of molecular subtypes

Several ETS transcription factors are involved in the pathogenesis of human cancers by different mechanisms. As gene copy number gain/amplification is an alternative mechanism of oncogenic activation and 1q gain is the most common copy number change in breast carcinoma, we investigated how that genomic change impacts in the expression of the three 1q ETS family members ETV3, ELK4, and ELF3. We have first evaluated 141 breast carcinomas for genome-wide copy number changes by chromosomal CGH and showed that 1q21 and 1q32 were the two chromosome bands with most frequent genomic copy number gains. Second, we confirmed by FISH with locus-specific BAC clones that cases showing 1q gain/amplification by CGH showed copy number increase of the ETS genes ETV3 (located in 1q21~23), ELF3, and ELK4 (both in 1q32). Third, gene expression levels of the three 1q ETS genes, as well as their potential targets MYC and CRISP3, were evaluated by quantitative real-time PCR. We here show for the first time that the most common genomic copy number gains in breast cancer, 1q21 and 1q32, are associated with overexpression of the ETS transcription factors ETV3 and ELF3 (but not ELK4) at these loci irrespective of molecular subtypes. Among the three 1q ETS genes, ELF3 has a relevant role in breast carcinogenesis and is also the most likely target of the 1q copy number increase. The basal-like molecular subtype presented the worst prognosis regarding disease-specific survival, but no additional prognostic value was found for 1q copy number status or ELF3 expression. In addition, we show that there is a correlation between the expression of the oncogene MYC, irrespectively of copy number gain at its loci in 8q24, and the expression of both the transcriptional repressor ETV3 and the androgen respondent ELK4.

Histone demethylase GASC1--a potential prognostic and predictive marker in invasive breast cancer

Background

The histone demethylase GASC1 (JMJD2C) is an epigenetic factor suspected of involvement in development of different cancers, including breast cancer. It is thought to be overexpressed in the more aggressive breast cancer types based on mRNA expression studies on cell lines and meta analysis of human breast cancer sets. This study aimed to evaluate the prognostic and predictive value of GASC1 for women with invasive breast cancer.

Methods

All the 355 cases were selected from a cohort enrolled in the Kuopio Breast Cancer Project between April 1990 and December 1995. The expression of GASC1 was studied by immunohistochemistry (IHC) on tissue microarrays. Additionally relative GASC1 mRNA expression was measured from available 57 cases.

Results

In our material, 56% of the cases were GASC1 negative and 44% positive in IHC staining. Women with GASC1 negative tumors had two years shorter breast cancer specific survival and time to relapse than the women with GASC1 positive tumors (p=0.017 and p=0.034 respectively). The majority of GASC1 negative tumors were ductal cases (72%) of higher histological grade (84% of grade II and III altogether). When we evaluated estrogen receptor negative and progesterone receptor negative cases separately, there was 2 times more GASC1 negative than GASC1 positive tumors in each group (chi2, p= 0.033 and 0.001 respectively). In the HER2 positive cases, there was 3 times more GASC1 negative cases than GASC1 positives (chi2, p= 0.029). Patients treated with radiotherapy (n=206) and hormonal treatment (n=62) had better breast cancer specific survival, when they were GASC1 positive (Cox regression: HR=0.49, p=0.007 and HR=0.33, p=0.015, respectively). The expression of GASC1 mRNA was in agreement with the protein analysis.

Conclusions

This study indicates that the GASC1 is both a prognostic and a predictive factor for women with invasive breast cancer. GASC1 negativity is associated with tumors of more aggressive histopathological types (ductal type, grade II and III, ER negative, PR negative). Patients with GASC1 positive tumors have better breast cancer specific survival and respond better to radiotherapy and hormonal treatment.

Androgen resistance in female mice increases susceptibility to DMBA-induced mammary tumors

Hormones, notably estrogens, are pivotal in the origins of breast cancer but androgenic effects, while supported by persistence of AR expression in breast cancers, remain controversial. This study determined the role of the androgen actions via androgen receptor (AR) in experimental mammary cancer. Androgen-resistant female and male mice (ARKO) were generated using Cre/loxP technique and featured a global AR inactivation. The effect of AR inactivation and influence of genetic background on 7,12-dimethylbenz[a]anthracene (DMBA)-induced tumorigenesis was confirmed using two separate ARKO models with different genetic backgrounds. The onset of palpable mammary tumors was significantly faster in ARKO females (median time 22 vs 34 weeks, respectively; (p = 0.0024; multivariate Cox regression) compared to WT and independent of the mouse genetic background. The cumulative incidence at 9 months was 81 ± 10% [mean ± SE] for ARKO compared to 50 ± 13% in WT females. The increased DMBA susceptibility of ARKO females was associated with a higher epithelial proliferation index but not with major structural or receptor (estrogen or progesterone) expression differences between the virgin WT or ARKO female mammary glands. AR inactivation allowed substantial ductal extension in ARKO males while WT males displayed only rudimentary epithelial branches or complete regression of epithelial structures. Yet, DMBA did not induce epithelial mammary tumors in WT or ARKO males, demonstrating that AR inactivation alone is insufficient to promote mammary tumors. These results demonstrate that AR inactivation accelerates mammary carcinogenesis in female mice exposed to the chemical carcinogen DMBA regardless of mouse genetic background but require prior exposure to endogenous ovarian hormones.

Does Androgen Receptor Have a Prognostic Role in Patients with Estrogen/Progesterone-Negative and c-erbB-2-Positive Breast Cancer?

Recently, it has been shown that androgen and androgen receptor (AR) also have an important role in the pathogenesis and outcome of breast cancer. However, their significance in different subtypes of breast cancer is still under investigation. The aim of this study was to study the effects of AR on clinicopathological features and prognosis in patients with estrogen and progesterone receptor (ER/PR)-negative, HER2-positive breast cancer. Tumor paraffin-embedded blocks from archives were used for AR study. Data of patients with ER/PR-negative and HER2-positive breast cancer diagnosed at our institute between 1999 and 2010 were recorded and analyzed retrospectively. We studied 36 patients with ER/PR-negative and HER2-positive breast cancer for AR status. Sixteen of them (44.4%) showed AR positivity. The median age was 47 and 56 years for AR-negative and -positive patients, respectively ( P = 0.03). The number of postmenopausal patients was higher in the AR-positive than -negative group (56 vs 30%) ( P = 0.01). Other demographic data were similar in both group. Histopathological parameters and tumor and nodal stages were similar in both groups. Trastuzumab treatment was more frequently given to AR-positive than -negative patients (94 vs 44%) ( P = 0.01). Median follow-up was 47.1 and 34.7 months in AR-negative and -positive groups, respectively ( P = 0.03). Relapse occurred in six and four patients in AR-negative and -positive groups. Median progression-free survival (PFS) was similar in both groups (15.7 and 19.6 months in AR-negative and -positive patients, respectively; P = 0.56). Two patients died at 23.4 and 46 months of follow-up in the AR-negative group. There were no deaths in the AR-positive group. Overall survival analyses were not done as a result of an unmet number of events. Median PFS was similar in AR-positive and -negative in that group of patients with ER/PR-negative and HER2-positive breast cancer. However AR-positive patients were more frequently postmenopausal, older, and positive for lymphovascular space invasion. More frequently applied trastuzumab in the AR-positive group might have an effect on the similarity of PFS between the two groups. Studies with higher numbers in this subset of patients with breast cancer will give more robust data.

Prolactin-induced protein mediates cell invasion and regulates integrin signaling in estrogen receptor-negative breast cancer

Introduction

Molecular apocrine is a subtype of estrogen receptor (ER)-negative breast cancer that is characterized by a steroid-response gene signature. We have recently identified a positive feedback loop between androgen receptor (AR) and extracellular signal-regulated kinase (ERK) signaling in this subtype. In this study, we investigated the transcriptional regulation of molecular apocrine genes by the AR-ERK feedback loop.

Methods

The transcriptional effects of AR and ERK inhibition on molecular apocrine genes were assessed in cell lines. The most regulated gene in this process, prolactin-induced protein (PIP), was further studied using immunohistochemistry of breast tumors and xenograft models. The transcriptional regulation of PIP was assessed by luciferase reporter assay and chromatin immunoprecipitation. The functional significance of PIP in cell invasion and viability was assessed using siRNA knockdown experiments and the mechanism of PIP effect on integrin-β1 signaling was studied using immunoblotting and immunoprecipitation.

Results

We found that PIP is the most regulated molecular apocrine gene by the AR-ERK feedback loop and is overexpressed in ER-/AR+ breast tumors. In addition, PIP expression is regulated by AR-ERK signaling in xenograft models. These observations are explained by the fact that PIP is a target gene of the ERK-CREB1 pathway and is also induced by AR activation. Furthermore, we demonstrated that PIP has a significant functional role in maintaining cell invasion and viability of molecular apocrine cells because of a positive regulatory effect on the Integrin-ERK and Integrin-Akt signaling pathways. In fact, PIP-knockdown markedly decreases the phosphorylation of ERK, Akt, and CREB1. Importantly, PIP knockdown leads to a marked reduction of integrin-β1 binding to ILK1 and ErbB2 that can be reversed by the addition of fibronectin fragments.

Conclusions

We have identified a novel feedback loop between PIP and CREB1 mediated through the Integrin signaling pathway. In this process, PIP cleaves fibronectin to release fragments that activate integrin signaling, which in turn increases PIP expression through the ERK-CREB1 pathway. In addition, we demonstrated that PIP expression has a profound effect on cell invasion and the viability of molecular apocrine cells. Therefore, PIP signaling may be a potential therapeutic target in molecular apocrine breast cancer.

The Role of Androgen Receptor in Breast Cancer

The androgen receptor (AR) is a proven clinical target in prostate cancer. Recent research indicates that it is an emerging hormonal target in breast cancer as well, with potential clinical benefit in both estrogen receptor(ER) positive and negative tumors. Compared to the ER, AR contains unique functional domains with relevance to its altered role in human breast cancer. The majority of ER-positive tumors express AR, and a significant percentage of ER-negative tumors might benefit from combined targeting of AR and the ErbB2/HER2 oncogene. Signaling downstream of AR might also affect many clinically important pathways which are also emerging clinical targets in breast cancer. AR expression might also play a role during tumor progression to metastatic disease. The role of AR as a new important biomarker in breast cancer will be reviewed herein.

Cross-regulation between FOXA1 and ErbB2 signaling in estrogen receptor-negative breast cancer

Molecular apocrine is a subtype of estrogen receptor-negative (ER.) breast cancer, which is characterized by a steroid-response gene signature that includes androgen receptor, FOXA1, and a high frequency of ErbB2 overexpression. In this study, we demonstrate that there is a strong association between the overexpression of FOXA1 and ErbB2 in ER- breast tumors. This has led us to identify a cross-regulation network between FOXA1 and ErbB2 signaling in ER- breast cancer. We present two mechanisms to explain the association between FOXA1 and ErbB2 overexpression in molecular apocrine cells. In one process, ErbB2 signaling genes CREB1 and c-Fos regulate FOXA1 transcription, and in another process, AP2α regulates the expression of both FOXA1 and ErbB2. Moreover, we demonstrate that FOXA1, in turn, regulates the transcription of ErbB2 signaling genes. This includes a core gene signature that is shared across two molecular apocrine cell lines. Importantly, the most upregulated (RELB) and downregulated (PAK1) genes in this signature are direct FOXA1 targets. Our data suggest that FOXA1 acts as a dual-function transcription factor and the repressive function of FOXA1 on RELB can be explained by the recruitment of its binding partner corepressor TLE3. It is notable that a group of FOXA1-regulated genes vary across molecular apocrine cell lines leading to the differences in the functional effects of FOXA1 on extracellular signal-regulated kinase phosphorylation and cell viability between these lines. This study demonstrates that there is a cross-regulation network between FOXA1 and ErbB2 signaling that connects FOXA1 to some of the key signaling pathways in ER-breast cancer.

Expression of the androgen receptor and its correlation with molecular subtypes in 980 chinese breast cancer patients

BACKGROUND

Recent studies have shown that androgen displays an inhibitory effect on breast cancer cell lines that express androgen receptor (AR) but not estrogen receptor (ER) and progesterone receptor (PR). We have previously reported that approximately 1/3 of ER negative high grade invasive ductal carcinomas express AR. Thus, AR can serve as a potential therapeutic target for this group of patients.

AIM

Here we investigated AR expression patterns in 980 consecutive breast carcinomas.

RESULTS

We found that (1) AR was expressed more frequently (77%) than ER (61%) and PR (60%) in breast carcinomas; (2) AR expression was associated with ER and PR expression (P < 0.0001), small tumor size (P = 0.0324) and lower Ki-67 expression (P = 0.0013); (3) AR expression was found in 65% of ER negative tumors; (4) AR expression was associated with PR and Ki-67 in ER negative tumors, but not in ER positive tumors; (5) AR expression was higher in ER positive subtypes (Luminal A, Luminal B and Luminal HER2 subtypes, 80%-86%) and lower in ER negative subtypes [HER2, triple negative (TN), and TN EFGR positive subtypes; 52%-66%], with over 50% of TN tumors expressing AR.

CONCLUSION

More breast carcinomas express AR than ER and PR, including significant numbers of ER negative and TN tumors, for which AR could serve as a potential therapeutic target.

Androgen receptor genotypes predict response to endocrine treatment in breast cancer patients

BACKGROUND

The androgen receptor (AR) is frequently expressed in breast cancers. The AR genotype may affect disease-free survival and response to endocrine therapy.

METHODS

In all, 634 women undergoing breast cancer surgery between 2002 and 2008 were followed until 30 June 2010. Six haplotype-tagging single-nucleotide polymorphisms in the AR, and the resulting AR diplotypes, were examined in relation to breast cancer patient characteristics, tumour characteristics, disease-free survival, and response to endocrine treatment.

RESULTS

Five common AR diplotypes were found. Seventeen rare variants were combined into a composite group. The resulting six AR diplotype groups were clustered into two subgroups, groups A (n=128) and B (n=499), with three diplotypes in each. Patients in group B had larger total breast volume (P=0.024), higher body mass index (BMI) (P=0.050), more axillary lymph node involvement (P(trend)=0.020), and higher histological grade (P(trend)=0.031). There were 59 breast cancer events in the 569 patients with invasive cancers and no preoperative treatment. Patients in group B also had shorter disease-free survival (P=0.037) than patients in group A. Among patients in group B with oestrogen receptor α positive tumours, tamoxifen (TAM) treatment was associated with longer disease-free survival (P=0.008), while treatment with aromatase inhibitors (AIs) was not (P=0.94). Response to endocrine treatment could not be predicted based on BMI, suggesting that the effect of AR diplotypes went beyond that of a higher BMI.

CONCLUSION

A marker for a group of patients who responded to TAM, but not to AIs, was identified. If this finding is confirmed, AR genotyping may provide useful information for selection of endocrine treatment of breast cancer patients.

Isolation and characterization of Pseudomonas aeruginosa PAO mutant that produces altered elastase

Triple-negative breast cancer (TNBC) is cancer that tested as negative for estrogen receptors (ER), progesterone receptors (PR), and excess human epidermal growth factor receptor 2 (HER2) protein which accounts for 15%–20% of all breast cancer cases. TNBC is considered to be a poorer prognosis than other types of breast cancer, mainly because it involves more aggressive phenotypes that are similar to stem cell–like cancer cells (cancer stem cell, CSC). Thus, targeted treatment of TNBC remains a major challenge in clinical practice. This review article surveys the latest evidence concerning the role of genomic alteration in current TNBC treatment responses, current clinical trials and potential targeting sites, CSC and drug resistance, and potential strategies targeting CSCs in TNBC. Furthermore, the role of insulin-like growth factor 1 receptor (IGF-1R) and nicotinic acetylcholine receptors (nAChR) in stemness expression, chemoresistance, and metastasis in TNBC and their relevance to potential treatments are also discussed and highlighted.