Prognostic value of androgen receptor in triple negative breast cancer: A meta-analysis

A triple hormone receptor ER, AR, and VDR signature is a robust prognosis predictor in breast cancer

BACKGROUND

Despite evidence indicating the dominance of cell-of-origin signatures in molecular tumor patterns, translating these genome-wide patterns into actionable insights has been challenging. This study introduces breast cancer cell-of-origin signatures that offer significant prognostic value across all breast cancer subtypes and various clinical cohorts, compared to previously developed genomic signatures.

METHODS

We previously reported that triple hormone receptor (THR) co-expression patterns of androgen (AR), estrogen (ER), and vitamin D (VDR) receptors are maintained at the protein level in human breast cancers. Here, we developed corresponding mRNA signatures (THR-50 and THR-70) based on these patterns to categorize breast tumors by their THR expression levels. The THR mRNA signatures were evaluated across 56 breast cancer datasets (5040 patients) using Kaplan-Meier survival analysis, Cox proportional hazard regression, and unsupervised clustering.

RESULTS

The THR signatures effectively predict both overall and progression-free survival across all evaluated datasets, independent of subtype, grade, or treatment status, suggesting improvement over existing prognostic signatures. Furthermore, they delineate three distinct ER-positive breast cancer subtypes with significant survival in differences-expanding on the conventional two subtypes. Additionally, coupling THR-70 with an immune signature identifies a predominantly ER-negative breast cancer subgroup with a highly favorable prognosis, comparable to ER-positive cases, as well as an ER-negative subgroup with notably poor outcome, characterized by a 15-fold shorter survival.

CONCLUSIONS

The THR cell-of-origin signature introduces a novel dimension to breast cancer biology, potentially serving as a robust foundation for integrating additional prognostic biomarkers. These signatures offer utility as a prognostic index for stratifying existing breast cancer subtypes and for de novo classification of breast cancer cases. Moreover, THR signatures may also hold promise in predicting hormone treatment responses targeting AR and/or VDR.

Androgen receptor: Structure, signaling, function and potential drug discovery biomarker in different breast cancer subtypes

The Androgen Receptor (AR) is emerging as an important factor in the pathogenesis of breast cancer (BC), which is the most common malignancy worldwide. >70 % of AR expression in primary and metastatic breast tumors has been observed which suggests that AR may be a new marker and a potential therapeutic target among AR-positive BC patients. Biological insight into AR-positive breast cancer reveals that AR may cross-talk with several vital signaling pathways, including key molecules and receptors. Downstream signaling of AR might also affect many clinically important pathways that are emerging as clinical targets in BC. AR exhibits different behaviors depending on the breast cancer molecular subtype. Preliminary clinical research using AR-targeted drugs, which have already been FDA-approved for prostate cancer (PC), has given promising results for AR-positive breast cancer patients. However, since AR positivity's prognostic and predictive value remains uncertain, it is difficult to identify and stratify patients who would benefit from AR-targeted therapies alone. Thus, the need of the hour is to target the androgen receptor as a monotherapy or in combination with other conventional therapies which has proven to be an effective clinical strategy for the treatment of prostate cancer patients, and these therapeutic strategies are increasingly being investigated in breast cancer. Therefore, in this manuscript, we review the role of AR in various cellular processes that promote tumorigenesis and aggressiveness, in different subtypes of breast cancer, as well as discuss ongoing efforts to target AR for the more effective treatment and prevention of breast cancer.

The molecular subtyping and precision medicine in triple-negative breast cancer---based on Fudan TNBC classification

Triple-negative breast cancer (TNBC) is widely recognized as the most aggressive form of breast cancer, occurring more frequently in younger patients and characterized by high heterogeneity, early distant metastases and poor prognosis. Multiple treatment options have failed to achieve the expected therapeutic effects due to the lack of clear molecular targets. Based on genomics, transcriptomics and metabolomics, the multi-omics analysis further clarifies TNBC subtyping, which provides a greater understanding of tumour heterogeneity and targeted therapy sensitivity. For instance, the luminal androgen receptor subtype (LAR) exhibits responsiveness to anti-AR therapy, and the basal-like immune-suppressed subtype (BLIS) tends to benefit from poly (ADP-ribose) polymerase inhibitors (PARPis) and anti-angiogenic therapy. The efficacy of multi-dimensional combination therapy holds immense importance in guiding personalized and precision medicine for TNBC. This review offers a systematic overview of recent FuDan TNBC molecular subtyping and its role in the instruction of clinical precision therapy.

Current and future trends in neoadjuvant immunotherapy for the treatment of triple-negative breast cancer

Triple-negative breast cancer (TNBC) comprises 15-20% of all breast cancers (BC). Lacking targeted therapy options, TNBC becomes the focal point of clinical investigations aiming not only to identify drugs with enhanced response potential but also to uncover new immunological and/or metabolic pathways conducive to more effective treatments. Currently, neoadjuvant treatment for TNBC relies on standard chemotherapy in conjunction with immunotherapy, given the improved response observed with this drug combination. This review delves into the latest therapeutic updates in TNBC treatment and explores potential advancements shaping the future landscape of this disease in the neoadjuvant setting.

The androgen receptor interacts with GATA3 to transcriptionally regulate a luminal epithelial cell phenotype in breast cancer

BACKGROUND

The androgen receptor (AR) is a tumor suppressor in estrogen receptor (ER) positive breast cancer, a role sustained in some ER negative breast cancers. Key factors dictating AR genomic activity in a breast context are largely unknown. Herein, we employ an unbiased chromatin immunoprecipitation-based proteomic technique to identify endogenous AR interacting co-regulatory proteins in ER positive and negative models of breast cancer to gain new insight into mechanisms of AR signaling in this disease.

RESULTS

The DNA-binding factor GATA3 is identified and validated as a novel AR interacting protein in breast cancer cells irrespective of ER status. AR activation by the natural ligand 5α-dihydrotestosterone (DHT) increases nuclear AR-GATA3 interactions, resulting in AR-dependent enrichment of GATA3 chromatin binding at a sub-set of genomic loci. Silencing GATA3 reduces but does not prevent AR DNA binding and transactivation of genes associated with AR/GATA3 co-occupied loci, indicating a co-regulatory role for GATA3 in AR signaling. DHT-induced AR/GATA3 binding coincides with upregulation of luminal differentiation genes, including EHF and KDM4B, established master regulators of a breast epithelial cell lineage. These findings are validated in a patient-derived xenograft model of breast cancer. Interaction between AR and GATA3 is also associated with AR-mediated growth inhibition in ER positive and ER negative breast cancer.

CONCLUSIONS

AR and GATA3 interact to transcriptionally regulate luminal epithelial cell differentiation in breast cancer regardless of ER status. This interaction facilitates the tumor suppressor function of AR and mechanistically explains why AR expression is associated with less proliferative, more differentiated breast tumors and better overall survival in breast cancer.

Androgen receptor in breast cancer and its clinical implication

Breast cancer is a heterogeneous group of diseases characterized by diverse subtypes. Currently, the classification of breast cancer is based on the status of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2). In addition to these receptors, the presence of the androgen receptor (AR) in breast cancer cells adds a layer of complexity to our understanding of the disease. The role of AR in breast cancer is intricate, as it can alter diverse signaling pathways in the presence of different hormone receptors (HRs). This complex interplay between signaling pathways affects patient outcomes and prognosis, and the presence of AR has a significant effect. While AR positivity is common in breast cancer, the efficacy of utilizing AR blockade as a monotherapy has been limited, demonstrating only modest results. To address this challenge, substantial efforts have been directed toward comprehending the intricacies of AR's role and pathways in breast cancer development in the hope of understanding its utility as a biomarker or drug target. Multiple ongoing clinical trials are currently investigating combination treatments involving AR inhibitors and other agents to disrupt oncogenic signaling pathways and their crosstalk. Particularly in the context of triple-negative breast cancer (TNBC), where targeted therapeutic options are lacking, extensive research efforts have been dedicated to exploring the potential of AR-related interventions. This review aims to provide an overview of the various breast cancer subtypes with AR signaling mechanisms, and ongoing clinical trials that hold the potential to reshape future clinical approaches.

Overexpression of BQ323636.1 contributes to anastrozole resistance in AR+ve/ER+ve breast cancer

Aromatase inhibitors (Ais) are used as adjuvant endocrine therapy for oestrogen receptor-positive (ER+ve) post-menopausal breast cancer patients. Ais, by inhibiting the enzyme aromatase, block the conversion of androgen to oestrogen, reducing oestrogen levels. Resistance to Ais limits their clinical utilisation. Here, we show that overexpression of BQ323636.1 (BQ), a novel splice variant of nuclear co-repressor NCOR2, is associated with resistance to the non-steroidal aromatase inhibitor anastrozole in ER+ve post-menopausal breast cancer. Mechanistic study indicates that BQ overexpression enhances androgen receptor (AR) activity and in the presence of anastrozole, causes hyper-activation of AR signalling, which unexpectedly enhanced cell proliferation, through increased expression of CDK2, CDK4, and CCNE1. BQ overexpression reverses the effect of anastrozole in ER+ve breast cancer in an AR-dependent manner, whilst co-treatment with the AR antagonist bicalutamide recovered its therapeutic effect both in vitro and in vivo. Thus, for BQ-overexpressing breast cancer, targeting AR can combat anastrozole resistance. Clinical study of 268 primary breast cancer samples of ER+ve patients who had been treated with non-steroidal Ais showed 32.5% (38/117) of cases with combined high nuclear expression of BQ and AR, which were found to be significantly associated with Ai resistance. Non-steroidal Ai-treated patients with high nuclear expression of both BQ and AR had poorer overall, disease-specific, and disease-free survival. These findings suggest the importance of assessing BQ and AR expression status in the primary ER+ve breast tumour prior to Ai treatment. This may save patients from inappropriate treatment and enable effective therapy to be given at an early stage. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

The Potential of Hormonal Therapies for Treatment of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is considered one of the most aggressive forms of breast cancer with poor survival rates compared to other breast cancer subtypes. TNBC is characterized by the absence of the estrogen receptor alpha, progesterone receptor, and the human epidermal growth factor receptor 2, limiting those viable treatment options available to patients with other breast cancer subtypes. Furthermore, due to the particularly high heterogeneity of TNBC, conventional treatments such as chemotherapy are not universally effective, leading to drug resistance and intolerable side effects. Thus, there is a pressing need to discover new therapies beneficial to TNBC patients. This review highlights current findings regarding the roles of three steroid hormone receptors, estrogen receptor beta, the androgen receptor, and the glucocorticoid receptor, in the progression of TNBC. In addition, we discussed several ongoing and completed clinical trials targeting these hormone receptors in TNBC patients.

Core Needle Biopsy Accuracy for Androgen Receptor Expression in Invasive Breast Cancer

OBJECTIVE

 Breast cancer (BC) biomarkers, such as hormone receptors expression, are crucial to guide therapy in BC patients. Antiandrogens have been studied in BC; however, limited data are available on androgen receptor (AR) expression test methodology. We aim to report the core needle biopsy (CNB) accuracy for AR expression in BC.

METHODS

 Patients diagnosed with stage I-III invasive BC from a single institution were included. Androgen receptor expression was evaluated by immunohistochemistry (IHC) using 1 and 10% cutoff and the AR expression in surgical specimens (SS) was the gold standard. Kappa coefficients were used to evaluate the intraprocedural agreement.

RESULTS

 A total of 72 patients were included, with a mean age of 61 years old and 84% were Luminal A or B tumors. The prevalence of AR expression in all BC samples was 87.5% using a cutoff ≥ 10% in SS. With a cutoff value ≥ 1%, CNB had an accuracy of 95.8% (Kappa value = 0.645; 95% confidence interval [CI]: 0.272-1.000; p < 0.001) and 86.1% (Kappa value = 0.365; 95% CI: 0.052-0.679; p < 0.001) when ≥ 10% cutoff was used for AR positivity. Androgen receptor expression in CNB (cutoff ≥ 1%) had a sensitivity of 98.5%, specificity of 60%, positive predictive value of 97.0%, and a negative predictive value of 76.9% in the detection of AR expression in SS.

CONCLUSION

 Core needle biopsy has good accuracy in evaluating AR expression in BC. The accuracy of CNB decreases with higher cutoff values for AR positivity.

Molecular features of androgen-receptor low, estrogen receptor-negative breast cancers in the Carolina breast cancer study

PURPOSE

Androgen receptor (AR) expression is absent in 40-90% of estrogen receptor (ER)-negative breast cancers. The prognostic value of AR in ER-negative patients and therapeutic targets for patients absent in AR remains poorly explored.

METHODS

We used an RNA-based multigene classifier to identify AR-low and AR-high ER-negative participants in the Carolina Breast Cancer Study (CBCS; N = 669) and The Cancer Genome Atlas (TCGA; N = 237). We compared AR-defined subgroups by demographics, tumor characteristics, and established molecular signatures [PAM50 risk of recurrence (ROR), homologous recombination deficiency (HRD), and immune response].

RESULTS

AR-low tumors were more prevalent among younger (RFD =  + 10%, 95% CI = 4% to 16%) participants in CBCS and were associated with HER2 negativity (RFD = - 35%, 95% CI = - 44% to - 26%), higher grade (RFD =  + 17%, 95% CI = 8% to 26%), and higher risk of recurrence scores (RFD =  + 22%, 95% CI = 16.1% to 28%), with similar results in TCGA. The AR-low subgroup was strongly associated with HRD in CBCS (RFD =  + 33.3%, 95% CI = 23.8% to 43.2%) and TCGA (RFD =  + 41.5%, 95% CI = 34.0% to 48.6%). In CBCS, AR-low tumors had high adaptive immune marker expression.

CONCLUSION

Multigene, RNA-based low AR expression is associated with aggressive disease characteristics as well as DNA repair defects and immune phenotypes, suggesting plausible precision therapies for AR-low, ER-negative patients.

TROP2, androgen receptor, and PD-L1 status in histological subtypes of high-grade metaplastic breast carcinomas

AIMS

High-grade metaplastic breast carcinoma (HG-MBC) is a rare subtype of invasive breast carcinoma, mostly triple-negative. Metaplastic carcinomas are less responsive to neoadjuvant chemotherapy and are associated with a worse outcome than invasive carcinomas of no special type.

METHODS

Clinicopathological characteristics and immunophenotype were retrospectively assessed in a series of 65 patients diagnosed with HG-MBC between 2005 and 2017 at the Curie Institute (antibody panel: oestrogen receptor [ER], progesterone receptor [PR], androgen receptor [AR], human epidermal growth factor receptor 2 [HER2], programmed death ligand-1 [PD-L1], and trophoblast cell surface antigen 2 [TROP2]).

RESULTS

The median age at diagnosis was 59.5 years. Six (9%) patients had metastatic disease at diagnosis. Among the nonmetastatic patients receiving neoadjuvant therapy, 26% (5/19) achieved pathological complete response. Most tumours were pT1/pT2 (77%) and 12% were pN+. Histological subtypes (mixed, squamous, mesenchymal, and spindle cell) were 40%, 35.5%, 15.5%, and 9%, respectively. Tumour-infiltrating lymphocytes were low or moderate except when squamous differentiation was present. Most tumours were triple-negative (92%). AR and TROP2 were positive in 34% and 85% of the cases, respectively. PD-L1 was positive in tumour cells in 18% (cutoff: 1% of positive tumour cells) of the cases and in tumour-infiltrating immune cells in 40% (cutoff: 1% of tumour area) of the cases. Notably, spindle cell and mesenchymal metaplastic breast carcinomas were mostly PDL1-negative. Lastly, 21 (32.3%) cases were HER2-low, all being HER2 1+, with no HER2 2+.

CONCLUSION

Metaplastic breast carcinoma could benefit from tailored therapeutic strategies adapted to the phenotypic specificities of histological subtypes.

Molecular Features of Androgen-Receptor Low, Estrogen Receptor-Negative Breast Cancers in the Carolina Breast Cancer Study

PURPOSE

Androgen receptor (AR) expression is absent in 40-90% of estrogen receptor (ER)-negative breast cancers. The prognostic value of AR in ER-negative patients and therapeutic targets for patients absent in AR remains poorly explored.

METHODS

We used an RNA-based multigene classifier to identify AR-low and AR-high ER-negative participants in the Carolina Breast Cancer Study (CBCS; n=669) and The Cancer Genome Atlas (TCGA; n=237). We compared AR-defined subgroups by demographics, tumor characteristics, and established molecular signatures [PAM50 risk of recurrence (ROR), homologous recombination deficiency (HRD), and immune response].

RESULTS

AR-low tumors were more prevalent among Black (relative frequency difference (RFD) = +7%, 95% CI = 1% to 14%) and younger (RFD = +10%, 95% CI = 4% to 16%) participants in CBCS and were associated with HER2-negativity (RFD = -35%, 95% CI = -44% to -26%), higher grade (RFD = +17%, 95% CI = 8% to 26%), and higher risk of recurrence scores (RFD = +22%, 95% CI = 16.1% to 28%), with similar results in TCGA. The AR-low subgroup was strongly associated with HRD in CBCS (RFD = +33.3%, 95% CI = 23.8% to 43.2%) and TCGA (RFD = +41.5%, 95% CI = 34.0% to 48.6%). In CBCS, AR-low tumors had high adaptive immune marker expression.

CONCLUSION

Multigene, RNA-based low AR expression is associated with aggressive disease characteristics as well as DNA repair defects and immune phenotypes, suggesting plausible precision therapies for AR-low, ER-negative patients.

Androgen Receptor Status in Triple Negative Breast Cancer: Does It Correlate with Clinicopathological Characteristics?

Purpose

Triple negative breast cancer (TNBC) is a breast carcinoma subtype that neither expresses estrogen (ER) and progesterone receptors (PR) nor the human epidermal growth factor receptor 2 (HER2). Patients with TNBC have been shown to have poorer outcomes mainly owing to the limited treatment options available. However, some studies have shown TNBC tumors expressing androgen receptors (AR), raising hopes of its prognostic role.

Patients and Methods

This retrospective study investigated the expression of AR in TNBC and its relationship with known patient demographics, tumor and survival characteristics. From the records of 205 TNBC patients, 36 had available archived tissue samples eligible for AR staining. For statistical purposes, tumors were classified as either "positive" or "negative" for AR expression. The nuclear expression of AR was scored by measuring the percentage of stained tumor cells and its staining intensity.

Results

AR was expressed by 50% of the tissue samples in our TNBC cohort. The relationship between AR status with age at the time of TNBC diagnosis was statistically significant, with all AR positive TNBC patients being greater than 50 years old (vs 72.2% in AR negative TNBC). Also, the relationship between AR status and type of surgery received was statistically significant. There were no statistically significant associations between AR status with other tumor characteristics including "TNM status", tumor grade or treatments received. There was no statistically significant difference in median survival between AR negative and AR positive TNBC patients (3.5 vs 3.1 years; p = 0.581). The relationship between OS time and AR status (p = 0.581), type of surgery (p = 0.061) and treatments (p = 0.917) were not statistically significant.

Conclusion

The androgen receptor may be an important prognostic marker in TNBC, with further research warranted. This research may benefit future studies investigating receptor-targeted therapies in TNBC.

MicroRNAs within the Basal-like signature of Quadruple Negative Breast Cancer impact overall survival in African Americans

We previously found that QNBC tumors are more frequent in African Americans compared to TNBC tumors. To characterize this subtype further, we sought to determine the miRNA-mRNA profile in QNBC patients based on race. Both miRNA and mRNA expression data were analyzed from TCGA and validated using datasets from the METABRIC, TCGA proteomic, and survival analysis by KMPLOT. miRNA-mRNAs which include FOXA1 and MYC (mir-17/20a targets); GATA3 and CCNG2 (mir-135b targets); CDKN2A, CDK6, and B7-H3 (mir-29c targets); and RUNX3, KLF5, IL1-β, and CTNNB1 (mir-375 targets) were correlated with basal-like and immune subtypes in QNBC patients and associated with a worse survival. Thus, QNBC tumors have an altered gene signature implicated in racial disparity and poor survival.

'Why is survival with triple negative breast cancer so low? insights and talking points from preclinical and clinical research'

INTRODUCTION

Triple negative breast cancer is typically related to poor prognosis, early metastasis, and high recurrence rate. Intrinsic and extrinsic biological features of TNBC and resistance mechanisms to conventional therapies can support its aggressive behavior, characterizing TNBC how extremely heterogeneous. Novel combination strategies are under investigation, including immunotherapeutic agents, anti-drug conjugates, PARP inhibitors, and various targeting agents, exploring, in the meanwhile, possible predictive biomarkers to correctly select patients for the optimal treatment for their specific subtype.

AREAS COVERED

This article examines the main malignity characteristics across different subtype, both histological and molecular, and the resistance mechanisms, both primary and acquired, to different drugs explored in the landscape of TNBC treatment, that lead TNBC to still has high mortality rate.

EXPERT OPINION

The complexity of TNBC is not only the main reason of its aggressivity, but its heterogeneity should be exploited in terms of therapeutics opportunities, combining agents with different mechanism of action, after a correct selection by biologic or molecular biomarkers. The main goal is to understand what TNBC really is and to act selectively on its characteristics, with a personalized anticancer treatment.

The POLR3G Subunit of Human RNA Polymerase III Regulates Tumorigenesis and Metastasis in Triple-Negative Breast Cancer

RNA polymerase (Pol) III transcribes short untranslated RNAs that contribute to the regulation of gene expression. Two isoforms of human Pol III have been described that differ by the presence of the POLR3G/RPC32α or POLR3GL/RPC32β subunits. POLR3G was found to be expressed in embryonic stem cells and at least a subset of transformed cells, whereas POLR3GL shows a ubiquitous expression pattern. Here, we demonstrate that POLR3G is specifically overexpressed in clinical samples of triple-negative breast cancer (TNBC) but not in other molecular subtypes of breast cancer. POLR3G KO in the MDA-MB231 TNBC cell line dramatically reduces anchorage-independent growth and invasive capabilities in vitro. In addition, the POLR3G KO impairs tumor growth and metastasis formation of orthotopic xenografts in mice. Moreover, KO of POLR3G induces expression of the pioneer transcription factor FOXA1 and androgen receptor. In contrast, the POLR3G KO neither alters proliferation nor the expression of epithelial-mesenchymal transition marker genes. These data demonstrate that POLR3G expression is required for TNBC tumor growth, invasiveness and dissemination and that its deletion affects triple-negative breast cancer-specific gene expression.

Androgen receptor function and targeted therapeutics across breast cancer subtypes

Despite significant progress in breast cancer (BC) therapy, it is globally the most commonly diagnosed cancer and leads to the death of over 650,000 women annually. Androgen receptor (AR) is emerging as a potential new therapeutic target in BC. While the role of AR is well established in prostate cancer (PCa), its function in BC remains incompletely understood. Emerging data show that AR's role in BC is dependent on several factors including, but not limited to, disease subtype, tumour microenvironment, and levels of circulating oestrogens and androgens. While targeting AR in PCa is becoming increasingly effective, these advances have yet to make any significant impact on the care of BC patients. However, this approach is increasingly being evaluated in BC and it is clear that improvements in our understanding of AR's role in BC will increase the likelihood of success for AR-targeted therapies. This review summarizes our current understanding of the function of AR across BC subtypes. We highlight limitations in our current knowledge and demonstrate the importance of categorizing BC subtypes effectively, in relation to determining AR activity. Further, we describe the current state of the art regarding AR-targeted approaches for BC as monotherapy or in combination with radiotherapy.

Racial Disparity in Quadruple Negative Breast Cancer: Aggressive Biology and Potential Therapeutic Targeting and Prevention

Simple Summary

Quadruple negative breast cancer (QNBC), a subgroup of triple negative BC, has emerged as a highly aggressive BC subtype that disproportionately afflicts and impacts Black/African-American (AA) women. In this article, we review molecular distinctions in Black/AA and White/European-American (EA) QNBC biology as well as address potential non-genetic risk factors that could be underlying this racially disparate burden. We aim to provide deeper insight and provide a framework for novel discovery of actionable therapeutic targets and identify lifestyle changes to improve outcomes for Black/AA QNBC patients.

Abstract

Black/African-American (AA) women, relative to their White/European-American (EA) counterparts, experience disproportionately high breast cancer mortality. Central to this survival disparity, Black/AA women have an unequal burden of aggressive breast cancer subtypes, such as triple-negative breast cancer (ER/PR-, HER2-wild type; TNBC). While TNBC has been well characterized, recent studies have identified a highly aggressive androgen receptor (AR)-negative subtype of TNBC, quadruple-negative breast cancer (ER/PR-, HER2-wildtype, AR-; QNBC). Similar to TNBC, QNBC disproportionately impacts Black/AA women and likely plays an important role in the breast cancer survival disparities experienced by Black/AA women. Here, we discuss the racial disparities of QNBC and molecular signaling pathways that may contribute to the aggressive biology of QNBC in Black/AA women. Our immediate goal is to spotlight potential prevention and therapeutic targets for Black/AA QNBC; ultimately our goal is to provide greater insight into reducing the breast cancer survival burden experienced by Black/AA women.

Luminal androgen receptor (LAR) subtype of triple-negative breast cancer: molecular, morphological, and clinical features

According to the classification presented by Lehmann BD (2016), triple-negative breast cancer (TNBC) is a heterogeneous group of malignant tumors with four specific subtypes: basal-like (subtype 1 and subtype 2), mesenchymal, and luminal androgen receptor (LAR) subtypes. The basal-like subtypes of carcinomas predominate in this group, accounting for up to 80% of all cases. Despite the significantly lower proportions of mesenchymal and LAR variants in the group of breast carcinomas with a TNBC profile, such tumors are characterized by aggressive biological behavior. To this end, the LAR subtype is of particular interest, since the literature on such tumors presents different and even contradictory data concerning the disease course and prognosis. This review is devoted to the analysis of the relevant literature, reflecting the main results of studies on the molecular properties and clinical features of the disease course of LAR-type TNBC carcinomas.

The landscape of systemic therapy for early stage triple negative breast cancer

INTRODUCTION

Triple negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with higher risk of disease recurrence and mortality than other breast cancer subtypes. Historically, chemotherapy has been the primary systemic treatment for early stage TNBC. Recent developments in immune checkpoint inhibitors (ICIs) and novel therapeutic agents have transformed the treatment of TNBC.

AREAS COVERED

This review provides a comprehensive overview of the current evidence on treatment of early stage TNBC. We highlight the incorporation of ICIs and other targeted therapies in (neo)adjuvant treatment and the ongoing development of novel therapeutic agents.

EXPERT OPINION

The landscape of early TNBC treatment is rapidly evolving which has given rise to the introduction of ICIs and PARP inhibitors into the systemic therapy. Despite modest improvement in pathologic complete response (pCR) rate, ICI plus chemotherapy significantly improves long-term outcomes and is now used in (neo)adjuvant treatment of patients with TNBC and high risk for disease recurrence. Capecitabine remains the standard adjuvant treatment for residual disease, with olaparib being an option for patients with germline BRCA1/2 mutations. Early detection of minimal residual disease may identify patients requiring additional therapy to prevent recurrence.

Heterogeneity of triple-negative breast cancer: understanding the Daedalian labyrinth and how it could reveal new drug targets

INTRODUCTION

Triple-negative breast cancer (TNBC) is considered the most aggressive breast cancer subtype with the least favorable outcomes. However, recent research efforts have generated an enhanced knowledge of the biology of the disease and have provided a new, more comprehensive understanding of the multifaceted ecosystem that underpins TNBC.

AREAS COVERED

In this review, the authors illustrate the principal biological characteristics of TNBC, the molecular driver alterations, targetable genes, and the biomarkers of immune engagement that have been identified across the subgroups of TNBC. Accordingly, the authors summarize the landscape of the innovative and investigative biomarker-driven therapeutic options in TNBC that emerge from the unique biological basis of the disease.

EXPERT OPINION

The therapeutic setting of TNBC is rapidly evolving. An enriched understanding of the tumor spatial and temporal heterogeneity and the surrounding microenvironment of this complex disease can effectively support the development of novel and tailored opportunities of treatment.

Triple Negative Breast Cancer: An Analysis of the Subtypes and the Effects of Menopausal Status on Invasive Breast Cancer

Background: Triple negative breast cancer (TNBC) is a subtype of breast cancer which lacks hormone receptor (HR) expression and HER2 gene amplification and is the most aggressive subtype, with a heterogeneous genetic profile. The aim of this retrospective study was to evaluate the clinical significance of menopausal status in breast cancer cases with TNBC. Methods: Primary breast cancer patients who underwent curative surgery were enrolled in this retrospective study. A total of 5153 invasive breast cancer cases with Stage I–III were analyzed. The distribution of cases according to the menopausal status and subtypes was investigated and the clinicopathological characteristics and prognosis were compared between pre- and postmenopausal TNBC patients. Results: TNBC was frequently seen in postmenopausal patients and Luminal B and Luminal/HER2 subtypes were more common in premenopausal patients. There was no difference in DFS in the Luminal A/B and HER2 subtypes, but a significant difference was seen in the TNBC patients. Premenopausal patients with TNBC frequently had an overexpression of the p53 protein, a significantly higher Ki-67 index value, and a higher nuclear grade. A multivariate analysis revealed that menopausal status, nodal status, and tumor size were significant factors for DFS in TNBC cases. Conclusion: Menopausal status significantly correlates with breast cancer subtypes. TNBC was often seen in postmenopausal patients and these patients tend to have more favorable factors and a better DFS than premenopausal patients. These findings suggest that menopausal status is an important factor for evaluating biology and prognosis in TNBC cases.

The Association of RGS2 and Slug in the Androgen-induced Acquisition of Mesenchymal Features of Breast MDA-MB-453 Cancer Cells

BACKGROUND

Epithelial-mesenchymal transition (EMT) of tumor cells is a prerequisite to cancer cell invasion and metastasis. This process involves a network of molecular alterations. Androgen receptor (AR) plays an important role in the biology of breast cancers, particularly those dependent on AR expression like luminal AR (LAR) breast cancer subtype. We have recently reported that the AR agonist, dihydrotestosterone (DHT), induces a mesenchymal transition of MDA-MB-453 cells, concomitant with transcriptional up-regulation of Slug and regulator of G protein signaling 2 (RGS2).

OBJECTIVE

The role of Slug and RGS2 in mediating the DHT-induced effects in these cells was investigated.

METHODS

MDA-MB-453 cells were used as a model system of LAR breast cancer. Immunofluorescence was used to examine cell morphology and protein localization. Protein expression was analyzed by immunoblotting. Protein localization was confirmed by cell fractionation followed by immunoblotting. Protein-protein interaction was confirmed by co-immunoprecipitation followed by immunoblotting. Transwell membranes were used to assess cell migration. Transfection of cells with siRNA molecules that target Slug and RGS2 mRNA was utilized to delineate the modes of action of these two molecules.

RESULTS

Treatment of MDA-MB-453 cells with DHT induced the expression of both proteins. In addition, AR-Slug, AR-RGS2, and Slug-RGS2 interactions were observed shortly after AR activation. Knocking down Slug abrogated the basal, but not the DHT-induced, cell migration and blocked DHT-induced mesenchymal transition. On the other hand, RGS2 knocked-down cells had an increased level of Slug protein and assumed mesenchymal cell morphology with induced migration, and the addition of DHT further elongated cell morphology and stimulated their migration. Inhibition of AR or β-catenin reverted the RGS2 knocked-down cells to the epithelial phenotype, but only inhibition of AR blocked their DHT-induced migration.

CONCLUSIONS

These results suggest the involvement of RGS2 and Slug in a complex molecular network regulating the DHT-induced mesenchymal features in MDA-MB-453 cells. The study may offer a better understanding of the biological role of AR in breast cancer toward devising AR-based therapeutic strategies.

Androgen down-regulates desmocollin 2 in association with induction of mesenchymal transition of breast MDA-MB-453 cancer cells

Desmosomes are cellular structures that are critical in cell-cell adhesion and in maintaining tissue architecture. Changes in the expression of desmocollin-2 (DSC2) have been noted during tumor progression into an invasive phenotype and as cells undergo epithelial-mesenchymal transition. We have previously reported that breast MDA-MB-453 cancer cells, a luminal androgen receptor model of triple-negative breast cancer, acquire mesenchymal features when treated with the androgen receptor (AR) agonist, dihydrotestosterone (DHT). We have therefore investigated androgen regulation of the expression and cellular localization of DSC2 in MDA-MB-453 cells. Treatment of the cells with DHT resulted in a dose-dependent reduction in DSC2 protein levels and dispersion of its membrane localization concomitant with AR- and β-catenin-mediated mesenchymal transition of cells. A significant correlation was revealed between decreased expression of AR and increased expression of DSC2 in patient samples. In addition, whereas lower expression of AR was associated with a reduced overall and recurrence-free survival of breast cancer patients, higher expression of DSC2 was found in invasive breast tumors than in normal breast cells and was correlated with lower patient survival. Upon knocking down DSC2, the cells became elongated, mesenchymal-like, and slightly, but insignificantly, more migratory. The addition of DHT further stimulated cell elongation and migration. DSC2 siRNA-transfected cells reverted to a normal epithelial morphology upon inhibition of β-catenin. These results highlight the role of DSC2 in maintaining the epithelial morphology of MDA-MB-453 cells and the negative regulation of the desmosomal protein by DHT during stimulation of the androgen-induced, β-catenin-mediated mesenchymal transition of the cells. This article is protected by copyright. All rights reserved.

Androgen Receptor as an Emerging Feasible Biomarker for Breast Cancer

Biomarkers can be used for diagnosis, prognosis, and prediction in targeted therapy. The estrogen receptor α (ERα) and human epidermal growth factor receptor 2 (HER2) are standard biomarkers used in breast cancer for guiding disease treatment. The androgen receptor (AR), a nuclear hormone receptor, contributes to the development and progression of prostate tumors and other cancers. With increasing evidence to support that AR plays an essential role in breast cancer, AR has been considered a useful biomarker in breast cancer, depending on the context of breast cancer sub-types. The existing survival analyses suggest that AR acts as a tumor suppressor in ER + ve breast cancers, serving as a favorable prognostic marker. However, AR functions as a tumor promoter in ER-ve breast cancers, including HER2 + ve and triple-negative (TNBC) breast cancers, serving as a poor prognostic factor. AR has also been shown to be predictive of the potential of response to adjuvant hormonal therapy in ER + ve breast cancers and to neoadjuvant chemotherapy in TNBC. However, conflicting results do exist due to intrinsic molecular differences between tumors and the scoring method for AR positivity. Applying AR expression status to guide treatment in different breast cancer sub-types has been suggested. In the future, AR will be a feasible biomarker for breast cancer. Clinical trials using AR antagonists in breast cancer are active. Targeting AR alone or other therapeutic agents provides alternatives to existing therapy for breast cancer. Therefore, AR expression will be necessary if AR-targeted treatment is to be used.

Impact of Androgen Receptor Expression and the AR:ER Ratio on the Survival Outcomes in the Diverse Subgroups of Vietnamese Breast Cancer: A Single Institutional Retrospective Cohort Analysis

Background: The androgen receptor (AR) has recently emerged as a useful marker for the more favorable prognosis and better outcomes among women with estrogen receptor (ER) + ve breast cancer (BC) and the further refinement of BC subtype. Furthermore, AR expression in ER − ve tumors has a particular prognostic significance. Additionally, the ratio of nuclear AR to ER may critically have an influence on tumor biology and respond to endocrine therapy. Purpose: To define the AR expression and AR:ER ratio, and explored their correlation with the clinicopathological features, prognosis, and survival outcomes in the various subclasses of invasive BC. Methods: The current study was conducted on 522 BC patients who had surgical operations, without neoadjuvant chemotherapy by applying a retrospective cohort analysis. The clinicopathological characteristics were recorded. Immunohistochemical staining was performed on AR, ER, PR, HER2, and Ki67. Expression of AR was paired into different immunophenotypes for analysis with clinicopathological features and survival. All BC patients’ survival was analyzed using Kaplan–Meier and log-rank models. Results: The presence of AR was detected in 65.3%. Positive AR, the ratio of AR:ER<2, luminal androgen receptor (LAR) + and AR + HER2 + immunophenotypes were significantly associated with better prognostic features. AR:ER<2 was observed in the prolonged overall survival (OS) and disease-free survival (DFS) (87.9 and 86.2%, respectively) compared to AR:ER≥2 (25.0% in both) (P < .001). In contrast, in HR + ve BCs, the AR expression was not significantly correlated with survival. The multivariate model revealed that the ratio of nuclear AR to ER remained as an independent prognostic variable. Conclusion: The AR expression had a distinct OS and DFS. The AR:ER ratio is an independent indicator for predicting the OS and DFS of BC patients in both univariate and multivariate analyses.

Involvement of β-catenin in Androgen-induced Mesenchymal Transition of Breast MDA-MB-453 Cancer Cells

Purpose The cellular and molecular dynamics of DHT-induced EMT in MDA-MB-453 cells were investigated.Methods:PCR arrays were used to examine the expression of EMT-regulatory genes. Immunoblotting was used to detect protein levels and confirm protein-protein interaction following immunoprecipitation. Immunofluorescence was used to observe rearrangement of the actin cytoskeleton and cell morphology. Cell migration was assessed by transwell assayResults: Change of cell morphology was concomitant with increased cell migration after treating cells with DHT. Exposure of cells to DHT for one hour was sufficient to induce changes in cell morphology and actin cytoskeleton after 72 hours indicating altered gene expression. A long-term lasting nuclear translocation of AR was observed after a short exposure of cells to DHT. Investigating the expression of 84 EMT-related genes revealed down-expression of β-catenin, N-cadherin, and TCF-4 and increased expression of Slug, all of which were confirmed at the protein level. Yet, not only early interaction of AR and β-catenin was observed following AR activation, inhibition of β-catenin blocked DHT-induced mesenchymal transition and migration. Wnt signaling was found to be partially important in DHT-induced morphological alteration. The mesenchymal transition of cells could be induced by treating cells with an inhibitor of glycogen synthase kinase-3β, an enzyme that inhibits β-catenin; this morphological transition could be reversed by antagonizing AR suggesting that AR functions downstream of β-catenin.Conclusions: These results suggest that MDA-MB-453 cells undergo partial EMT induced by DHT, β-catenin is critical for this phenotypic change, and AR probably reciprocally mediates the mesenchymal transition of these cells upon activation of GSK-3 β.

Estrogens and Progestogens in Triple Negative Breast Cancer: Do They Harm?

Triple-negative breast cancers (TNBC) occur more frequently in younger women and do not express estrogen receptor (ER) nor progesterone receptor (PR), and are therefore often considered hormone-insensitive. Treatment of premenopausal TNBC patients almost always includes chemotherapy, which may lead to premature ovarian insufficiency (POI) and can severely impact quality of life. Hormone replacement therapy (HRT) is contraindicated for patients with a history of hormone-sensitive breast cancer, but the data on safety for TNBC patients is inconclusive, with a few randomized trials showing increased risk-ratios with wide confidence intervals for recurrence after HRT. Here, we review the literature on alternative pathways from the classical ER/PR. We find that for both estrogens and progestogens, potential alternatives exist for exerting their effects on TNBC, ranging from receptor conversion, to alternative receptors capable of binding estrogens, as well as paracrine pathways, such as RANK/RANKL, which can cause progestogens to indirectly stimulate growth and metastasis of TNBC. Finally, HRT may also influence other hormones, such as androgens, and their effects on TNBCs expressing androgen receptors (AR). Concluding, the assumption that TNBC is completely hormone-insensitive is incorrect. However, the direction of the effects of the alternative pathways is not always clear, and will need to be investigated further.

Therapeutic Strategies for Metastatic Triple-Negative Breast Cancers: From Negative to Positive

Metastatic triple-negative breast cancer (TNBC) is a distinct and immensely complex form of breast cancer. Among all subtypes of breast cancers, TNBC has a comparatively high rate of relapse, a high rate of distant metastasis, and poor overall survival after standard chemotherapy. Chemotherapy regimens are an essential component of the management of this estrogen receptor-negative, progesterone receptor-negative, and epidermal growth factor receptor2 negative subtype of breast cancers. Chemotherapy is critical for preventing the recurrence of the disease and for achieving long-term survival. Currently, a couple of agents are approved for the management of this disease, including chemotherapy like eribulin, targeted therapy like PARP inhibitor, as well as an antibody-drug conjugate (ADC) to target TROP2. Like many other metastatic cancers, immune checkpoint inhibitors (ICIs) have also been approved for TNBC patients with PD-L1 positive tumors and high tumor mutational burden. In this review article, we discuss these newly approved and promising novel agents that may change the therapeutic landscape for advanced/metastatic TNBC patients.

Emerging Therapeutics for Patients with Triple-Negative Breast Cancer

PURPOSE OF REVIEW

Triple negative breast cancer (TNBC) accounts for approximately 10-15% of all breast cancers and it is associated with a poor prognosis. However, recent new effective treatment strategies have improved its outcomes. The aim of this review is to provide an overview on the emerging therapeutics for TNBC, describing both previously approved therapies that are currently being repurposed, as well as new target therapies that may improve patient outcomes.

RECENT FINDINGS

Emerging therapies are forthcoming in TNBC's treatment landscape, including new post-neoadjuvant chemotherapy strategies, PARP inhibitors, immune checkpoint inhibitors, and antibody-drug conjugates. Combination of different therapies such as AKT/PI3K/mTOR-inhibitors, other immunotherapeutic agents, CDK-inhibitors, antiandrogens, antiangiogenics, and histone deacetylase inhibitors is under clinical investigation. The treatment landscape for TNBC is gradually evolving towards a more personalized approach with promising expectations.

T1a triple negative breast cancer has the worst prognosis among all the small tumor (<1 cm) of TNBC and HER2-rich subtypes

Background

Triple negative breast cancer (TNBC), accounting for 15% of all breast cancer cases, was usually considered as the most aggressive subtype. The present study evaluated the prognosis of T1a TNBC and the impact of tumor size on T1 TNBC survival in large-scale population.

Methods

This retrospective study enrolled T1a/T1b/T1c TNBC and HER2⁺/hormone receptor (HoR)^- patients diagnosed between 2010 to 2012 from the Surveillance, Epidemiology, and End Results database. The following information was extracted for further analyses: demographic variables including age at diagnosis, race, marital status, laterality, histological grade, T/N stage, American Joint Committee on Cancer (AJCC) stage, radiation therapy, survival and cause of death. Kaplan-Meier method and Cox regression were engaged for breast cancer specific survival (BCSS) and overall survival (OS) analyses.

Results

In all, the present study enrolled 6,953 TNBC and 2,648 HER2⁺/HoR^- patients. T1a TNBC which generally omitted adjuvant chemotherapy had worse prognosis than T1a HER2⁺/HoR^- [BCSS: hazard ratio (HR) 3.23, 95% confidence interval (CI): 1.05-9.09, P=0.03; OS: HR 2.63, 95% CI: 1.25-5.56, P=0.01] and T1b HER2⁺/HoR^- (BCSS: HR 5.26, 95% CI: 1.61-16.7, P=0.006; OS: HR 3.03, 95% CI: 1.27-7.14, P=0.013) tumors which both were recommended by the National Comprehensive Cancer Network (NCCN) guideline to have chemotherapy. T1a TNBC also showed a trend with poorer prognosis than T1b TNBC, but did not reach statistical significance.

Conclusions

T1a TNBC had the worst prognosis among all small tumors (<1 cm) of TNBC and HER2⁺/HoR^- subtypes, indicating the necessity of more intensive adjuvant treatment.

Triple-negative breast cancer: promising prognostic biomarkers currently in development

Introduction: Triple-negative breast cancer (TNBC) is an aggressive type of breast cancer associated with poor prognosis and limited treatment options. Validated prognostic and predictive biomarkers are needed to guide treatment decisions and prognostication.Areas covered: In this review, we discuss established and developing prognostic and predictive biomarkers in TNBC and associated emerging and approved therapies. Biomarkers reviewed include epidermal growth factor receptor (EGFR), vascular endothelial growth factors (VEGF), fibroblast growth factor receptor (FGFR), human epidermal growth factor receptor 2 (HER2), androgen receptor, NOTCH signaling, oxidative stress/redox signaling, microRNAs, TP53 mutation, breast cancer susceptibility gene 1 or 2 (BRCA1/2) mutation/homologous recombination deficiency (HRD), NTRK gene fusion, PI3K/AKT/mTOR, immune biomarkers (programmed death-ligand 1 (PDL1), tumor-infiltrating lymphocytes (TILs), tumor mutational burden (TMB), neoantigens, defects in DNA mismatch repair proteins (dMMR)/microsatellite instability-high (MSI-H)), circulating tumor cells/cell-free DNA, novel targets of antibody-drug conjugates, and residual disease.Expert opinion: Biomarker-driven care in the management of TNBC is increasing and has helped expand options for patients diagnosed with this subtype of breast cancer. Research efforts are ongoing to identify additional biomarkers and targeted treatment options with the ultimate goal of improving clinical outcomes and survivorship.

Androgen Receptor and PIM1 Expression in Tumor Tissue of Patients With Triple-negative Breast Cancer

BACKGROUND/AIM

Effective targeted therapies for triple-negative breast cancer (TNBC) are limited. In a subset of TNBC, androgen receptor (AR) plays an important role, while the human proviral integration site for Moloney murine leukemia virus-1 (PIM1) overexpression is also implicated. PIM1 kinases phosphorylate AR, thus regulating its transcriptional activity, regardless of the presence or not of androgens. We evaluated the expression of AR and PIM1 and their prognostic significance in TNBC.

MATERIALS AND METHODS

AR and PIM1 transcripts were quantified by quantitative reverse transcription polymerase chain reaction in formalin-fixed paraffin-embedded tumor from 141 patients with TNBC.

RESULTS

AR was expressed in 38.3%, PIM1 in 10.6%, while co-expression of AR and PIM1 was detected in 7/141 cases (5.0%). No prognostic significance of AR or PIM1 was reached for overall or disease-free survival.

CONCLUSION

Co-expression of AR and PIM1 exists in only in a small percentage of patients with TNBC. The implications of this finding in the therapeutic management of patients with TNBC should be investigated in larger patient cohorts.

Targeted Treatment of Triple-Negative Breast Cancer

ABSTRACT

Triple-negative breast cancer is increasingly recognized as a heterogeneous entity that can be categorized according to histologic, molecular, and clinical subtypes. While chemotherapy remains the backbone of treatment for this disease, there are now several available targeted agents including immunotherapy, poly(adenosine diphosphate-ribose) polymerase inhibitors, and most recently a Food and Drug Administration-approved antibody-drug conjugate sacituzumab govitecan-hziy as a third-line treatment of metastatic triple-negative breast cancer. We review several actionable targets for triple-negative breast cancer and describe promising nonimmunotherapeutic agents including cyclin-dependent kinase inhibitors, androgen receptor inhibitors, mitogen-activated protein kinase inhibitors, phosphoinositide 3-kinase inhibitors, AKT (also known as protein kinase B) inhibitors, and antibody-drug conjugates.

Triple-Negative Breast Cancer: Assessing the Role of Immunohistochemical Biomarkers on Neoadjuvant Treatment

OBJECTIVE

This study aimed to investigate the influence of immunohistochemical (IHC) biomarkers in the response to neoadjuvant chemotherapy (NACT) and survival outcomes in the subset of locally advanced triple-negative breast cancer (TNBC).

MATERIALS AND METHODS

The epidermal growth factor receptor (EGFR), androgen receptor (AR), cytokeratins (CK5/6, CK14 and CK17), Ki67 and p53 immunohistochemistry were evaluated on 171 cases of TNBC submitted to NACT and subsequently to surgery. Intensity and percentage of the expression of these biomarkers were combined to formulate a specific score, that was correlated with prognostic features and assessed for survival outcomes.

RESULTS

Most patients had advanced clinical-stage tumors (stage III: 83.6%; cT3/T4: 85.9%; cN1-3: 71.3%). The predominant histological subtype was high-grade (67.3%) and invasive ductal carcinoma (93.6%). The residual cancer burden (RCB) 0-1 corresponded to 28.7% of cases and low-risk lymph node ratio (LNR) represented 77.2%. High Ki67 expression only showed a significant correlation with grade 3 tumors (p = 0.0157). CK5/6 was observed in 16% (27/169), CK14 was positive in 10.1% (17/169), CK17 in 91.1% (153/168), p53 in 52.6% (70/133), EGFR in 92.9% (157/169 cases), AR in 13% (22/169) and Ki67 index was scored ≥40% in 57.9% (95/165). No IHC biomarker significantly impacted response or survival. Regarding the analysis of the outcomes of event-free survival (EFS) and overall survival (OS), clinical stage (p = 0.014 and p = 0.042, respectively), RCB (p < 0.0001 and p <0.0001, respectively) and LNR (p <0.0001 and p <0.0001, respectively) showed significant association.

CONCLUSION

No IHC biomarker evaluated showed a significant association with a response or survival outcomes in TNBC patients. Clinical stage, LNR and RCB stood out for strongly influencing survival.

Insights for the application of TILs and AR in the treatment of TNBC in routine clinical practice

Triple negative breast cancer (TNBC), usually presenting with a very aggressive phenotype, is a heterogeneous entity. We aim to discuss new biomarkers, suitable for prognostic and predictive purposes. We retrospectively collected clinical variables and immunohistochemical characteristics of early TNBCs, specifically focusing on the prognostic and predictive significance of tumor infiltrating lymphocytes (TILs) and androgen receptor (AR) expression, assessing their correlation with clinical variables. Among 159 patients, TILs were significantly higher in younger patients and with lower BMI, and in tumors with higher ki-67 and greater nodal involvement; conversely, AR was significantly higher in older patients and in tumors with lower ki-67. Interestingly and in line with literature, both TILs level and ARs expression were lower within metastatic sites, in patients who developed distant metastases, compared to those found in the primary site. Small (pT1) and node negative tumors were highly represented and no correlation of either TILs or AR with prognosis could be observed. Our findings support the use of stromal TILs to identify a more aggressive, but chemo-sensitive phenotype, mostly represented in younger women, while AR may identify a less aggressive, slow-growing luminal TNBC subtype, more common among older patients. TILs and AR are worth implementing in routine clinical practice to refine prognosis even if, in our case series, we couldn't identify a significant correlation of the two variables with either disease-free and overall survival.

Androgen Receptor mRNA levels determine the prognosis in triple-negative breast cancer patients

BACKGROUND

Anti-Androgen Receptor (AR) therapy holds promise for a subset of AR expressing triple-negative breast cancer (TNBC) patients. However, current AR assays are suboptimal in detecting the dynamic range of AR expression, contributing to its controversial role in TNBC disease prognosis. This study is aimed at evaluating the feasibility of qRT-PCR to sensitively and robustly detect AR mRNA levels for prognostication.

METHODS

mRNA expression profiling was performed on FFPE blocks from a retrospective cohort of 101 TNBC patients using qRT-PCR and compared with AR protein expression by immunohistochemistry . Statistical analyses included Spearman's rank correlation, Chi-square and Kaplan-Meier analyses. Distant Metastasis Free Survival was used as the end point in survival analysis.

RESULTS

AR mRNA expression was observed in 34/101 patients (34%) whereas 12/80 cases (15%) were positive by IHC. qRT-PCR could thus detect more AR positive patients as compared to IHC, with 75% (9/12) concordance between the two methods. Co-expression of GATA3 and FOXA1 mRNA was observed in 85 and 88% of AR mRNA positive tumors, respectively. AR mRNA positivity was significantly correlated with age at disease onset (p = 0.02), high FOXA1/GATA3 (p < 0.05) and distant recurrence. AR mRNA positive patients had poorer DMFS (43%; p = 0.002). DMFS dropped further to 26% (p = 0.006) in AR (+)/high FOXA1/GATA3 patients. AR mRNA expression together with node positivity had the worst DMFS (23%; p < 0.0001) compared to patients who were either positive for any one of these, or negative for both AR and node status. Low Ki67 mRNA with AR mRNA positivity also had poorer DMFS (39%; p = 0.001) compared to patients expressing low Ki67 with no AR mRNA expression.

CONCLUSION

qRT-PCR was more sensitive and reliable in detecting the dynamic expression levels of AR compared to IHC and this variation could be explained by the higher sensitivity of the former method. High AR mRNA expression was strongly associated with expression of AR protein, high FOXA1/GATA3 mRNA, and with poor prognosis. qRT-PCR was more efficient in detecting the AR positive cases compared to IHC. A distinct signature involving high GATA3/FOXA1, low Ki67, and node positivity in AR mRNA positive tumors correlated with poor prognosis. Thus, AR mRNA screening can serve as an effective prognostic marker along with offering potential targeted therapy options for TNBC.

Lack of Androgen Receptor Expression Selects for Basal-Like Phenotype and Is a Predictor of Poor Clinical Outcome in Non-Metastatic Triple Negative Breast Cancer

Background: Androgen receptor (AR) has emerged as a significant favorable prognostic indicator in estrogen receptor expressing (ER⁺) breast cancer (BCa); however, its clinical and biological relevance in triple negative breast cancer (TNBC) and association with cancer stem cell (CSC) markers remain ambiguous. Methods: We examined the immunohistochemical expression of AR in a cohort of stage I-III TNBC cases (n = 197) with a long-term clinical follow-up data (mean follow-up = 53.6 months). Significance of AR expression was correlated with prognostic biomarkers including cancer stem cell markers (CD44, CD24, and ALDH1), basal markers (CK5, CK14, and nestin), proliferation marker (ki-67), apoptotic marker (Bcl-2), and COX-2. Expression of CK5 and nestin was used for the categorization of TNBC into basal (TN, CK5⁺, and/or nestin⁺) and non-basal (TN, CK5^-, and/or nestin^-) phenotypes, and Kaplan-Meier curves were used for estimation of overall survival and breast cancer-specific survival (BCSS). Results: AR expression was observed in 18.8% of non-metastatic TNBC tumors. Expression of AR correlated with lower grade (P < 0.001) and conferred a favorable prognostic significance in patients with axillary lymph node metastasis (P = 0.005). Lack of AR expression correlated with expression of CSC phenotype (CD44⁺/CD24^-) (P < 0.001), COX-2 (P = 0.02), basal markers (CK5: P = 0.03), and nestin (P = 0.01). Basal-like phenotype (TN, CK5⁺, and/or nestin⁺) correlated with quadruple-negative breast cancer (QNBC) and showed a significant association with adverse prognostic markers including high proliferation index (P < 0.001), expression of COX-2 (P = 0.009), and CSC phenotype (CD44⁺/CD24^-: P = 0.01). Expression of AR remained an independent prognostic indicator for improved overall survival (P = 0.003), whereas basal-like phenotype was associated with an adverse BCSS (P = 0.013). Conclusions: Assessment of AR and basal markers identified biologically and clinically distinct subgroups of TNBC. Expression of AR defined a low-risk TNBC subgroup associated with improved overall survival, whereas expression of basal markers (CK5 and nestin) identified a high-risk subgroup associated with adverse BCSS. Integration of immunohistochemical analysis of AR and basal biomarkers to the assessment of TNBC tumors is expected to improve the prognostication of an otherwise heterogeneous disease.

Triple-negative pleomorphic lobular carcinoma and expression of androgen receptor: Personal case series and review of the literature

Pleomorphic lobular carcinoma (PLC) is a histological variant of invasive lobular carcinoma (ILC) and is associated with worse prognosis than classical ILC. It exhibits a greater degree of cellular atypia and pleomorphism and is occasionally accompanied with apocrine morphology. We investigated the immunohistochemical characteristics of samples from 31 Japanese patients with PLC to elucidate the clinicopathological characteristics of PLC including androgen receptor (AR) immunoreactivity. The surrogate molecular subtypes were luminal A-like, luminal B-like, luminal B-like/HER2, HER2-type, and triple-negative in 5, 4, 3, 5, and 14 cases, respectively. AR was positive in 92.8% (13/14) of the triple-negative PLC cases and 100% (10/10) of the non-triple-negative PLC cases. Disease-specific survival was worse in patients with histological grade 3 PLCs than in those with histological grade 2 PLCs (p = 0.007). However, there was no significant difference in the progression-free survival between the two groups (p = 0.152). No other clinicopathological characteristics were associated with prognosis. These results reveal that PLC exhibits various surrogate molecular subtypes and that the triple-negative subtype frequently expresses AR. The observed molecular apocrine differentiation implicates that triple-negative PLC can be categorized into the luminal AR subtype. Furthermore, AR-targeted therapy might be useful for patients with triple-negative PLC.

Novel targeted therapies for metastatic breast cancer

Metastatic breast cancer (mBC) continues to be a leading cause of cancer-related death in women. Even though mortality rates have improved over recent years, the 5-year survival rate of advanced BC is still at only 27%. As researchers and clinicians attempt to tackle this challenge, there has been extensive research and many trials studying treatment options for BC patients with metastatic disease, with numerous new therapies being discovered as a result. We review the most pertinent novel agents to enter the scope of BC treatment, including CDK4/6 inhibitors, PI3K inhibitors, mTOR inhibitors, immunotherapy, PARP inhibitors, and more.

Pathology of triple negative breast cancer

Triple negative breast cancer (TNBC) is a subtype of breast tumor lacking hormone receptors expression and HER2 gene amplification and represents 24 % of newly diagnosed breast neoplasms. In this review, pathological aspects of triple-negative breast cancer are illustrated, with particular attention to the seminal studies that defined this subtype of breast cancer by a molecular point of view. This paper also focuses on practical issues raised in clinical routine by the introduction of genetic expression breast cancer profiling and the innovative prognostic and predictive impact on triple-negative breast cancer pathology. Moreover, histopathological aspects of triple-negative neoplasms are also mentioned, underlying the importance of histologic diagnosis of particular cancer subtypes with decisive impact on clinical outcome. Importantly, focus on new therapeutic frontier represented by immunotherapy is illustrated, with particular mention of immune checkpoint inhibitors introduction in TNBC therapy and their impact on future treatments.

Early stage triple negative breast cancer: Management and future directions

Triple negative breast cancer is the most aggressive kind of breast cancer with high risk of recurrences and poor outcomes. Systemic chemotherapy has significantly improved long term outcomes in early stage patients; however, metastatic recurrences still develop in a significant number of patients. Anthracycline and taxane based chemotherapy regimens are standard of care for early stage patients. Neoadjuvant treatment is preferred due to the ability to assess pathologic responses providing important prognostic information and guidance in adjuvant therapy decisions. Carboplatin addition to the anthracycline and taxane backbone is associated with a significant improvement in pathologic complete response but is associated with more toxicity. Understanding the immune microenvironment of triple negative disease is an exciting field and immune checkpoint inhibitors have shown great promise in further improving response rates in early stage patients. Patients with residual disease after neoadjuvant chemotherapy have a significantly higher risk of recurrence compared to those with complete responses. Adjuvant capecitabine for these high-risk patients have shown significant improvement in long term outcomes and is routinely used in this setting. Given the heterogeneity within triple negative tumors, molecular subtypes with variable genomic makeup and chemo sensitivities have been identified and will likely aid in further clinical developmental therapeutics.

Co-Expression of Androgen Receptor and Cathepsin D Defines a Triple-Negative Breast Cancer Subgroup with Poorer Overall Survival

Background: In the triple-negative breast cancer (TNBC) group, the luminal androgen receptor subtype is characterized by expression of androgen receptor (AR) and lack of estrogen receptor and cytokeratin 5/6 expression. Cathepsin D (Cath-D) is overproduced and hypersecreted by breast cancer (BC) cells and is a poor prognostic marker. We recently showed that in TNBC, Cath-D is a potential target for antibody-based therapy. This study evaluated the frequency of AR/Cath-D co-expression and its prognostic value in a large series of patients with non-metastatic TNBC. Methods: AR and Cath-D expression was evaluated by immunohistochemistry in 147 non-metastatic TNBC. The threshold for AR positivity (AR+) was set at ≥1% of stained cells, and the threshold for Cath-D positivity (Cath-D+) was moderate/strong staining intensity. Lymphocyte density, macrophage infiltration, PD-L1 and programmed cell death (PD-1) expression were assessed. Results: Scarff-Bloom-Richardson grade 1–2 and lymph node invasion were more frequent, while macrophage infiltration was less frequent in AR+/Cath-D+ tumors (62.7%). In multivariate analyses, higher tumor size, no adjuvant chemotherapy and AR/Cath-D co-expression were independent prognostic factors of worse overall survival. Conclusions: AR/Cath-D co-expression independently predicted overall survival. Patients with TNBC in which AR and Cath-D are co-expressed could be eligible for combinatory therapy with androgen antagonists and anti-Cath-D human antibodies.

Influence of Androgen Receptor on the Prognosis of Breast Cancer

We investigated the prognostic influence of androgen receptor (AR) on breast cancer. AR status was assessed using immunohistochemistry with tissue microarrays from 395 operable primary breast cancer patients who received curative surgery. The Kaplan–Meier estimator was used to analyze the survival rates and a log-rank test was used to determine the significance of the differences in survival. The Cox proportional hazards model was used to calculate the hazard ratio (HR) and the 95% confidence interval (CI) of survival. There were 203 (51.4%) subjects with a low expression of AR, and 192 patients (48.6%) with a high expression rate. The high AR expression group showed superior overall survival (p = 0.047) and disease-free survival (p = 0.004) when compared with the low AR expression group. The high AR expression group showed superior systemic recurrence-free survival when compared with the low AR expression group (p = 0.027). AR was an independent prognostic factor for both overall survival (HR, 0.586; 95% CI, 0.381–0.901; p = 0.015) and disease-free survival (HR, 0.430; 95% CI, 0.274–0.674; p < 0.001). A high AR expression was a significant favorable prognostic factor only in the subgroups with positive hormone receptors (HRc) and negative human epidermal growth factor receptor 2 (HER2) when considering disease-free survival (p = 0.026). The high AR expression group was significantly associated with superior overall survival and disease-free survival when compared with the low AR expression group with breast cancer patients. AR was a significant independent prognostic factor for both overall survival and disease-free survival. The prognostic impact of AR was valid in the HRc(+)/HER2(−) subtype when considering disease-free survival. These findings suggest the clinical usefulness of AR as a prognostic marker of breast cancer in clinical settings.

The Landscape of Targeted Therapies in TNBC

Triple negative breast cancer (TNBC) constitutes the most aggressive molecular subtype among breast tumors. Despite progress on the underlying tumor biology, clinical outcomes for TNBC unfortunately remain poor. The median overall survival for patients with metastatic TNBC is approximately eighteen months. Chemotherapy is the mainstay of treatment while there is a growing body of evidence that targeted therapies may be on the horizon with poly-ADP-ribose polymerase (PARP) and immune check-point inhibitors already established in the treatment paradigm of TNBC. A large number of novel therapeutic agents are being evaluated for their efficacy in TNBC. As novel therapeutics are now incorporated into clinical practice, it is clear that tumor heterogeneity and clonal evolution can result to de novo or acquired treatment resistance. As precision medicine and next generation sequencing is part of cancer diagnostics, tailored treatment approaches based on the expression of molecular markers are currently being implemented in clinical practice and clinical trial design. The scope of this review is to highlight the most relevant current knowledge regarding underlying molecular profile of TNBC and its potential application in clinical practice.

Neoadjuvant Chemotherapy in Triple Negative Breast Cancer: Correlation between Androgen Receptor Expression and Pathological Response

Background:

There is growing evidence that the response to chemotherapy may be affected by Androgen Receptor (AR) expression suggesting that triple-negative breast cancers (TNBC) AR+ and quadruple negative breast cancer (QNBC) subtypes may have different diseases behavior.

Methodology:

We retrospectively estimated the predictive value of the AR expression in stage II and stage III TNBC patients treated with neoadjuvant chemotherapy (NAC) and correlated with the rate of pathological response (pCR).

Results:

Of 89 TNBC patients, 29 patients (32.6%) were TNBC AR+ and 60 patients (67.4) were QNBC. Most of the patients were less than 60 years old. Of note, approximately 62% in the QNBC group were less than 40 years old compared with 39 % in the TNBC AR+ group. The Ki-67 expression was higher in the QNBC in comparison with TNBC AR+ being 86.7% and 65.5%, respectively. QNBC subgroup showed higher rates of pCR compared with TNBC; 60% and 24%, respectively. Higher Ki-67 expression, higher grade, and lymph node involvement were statistically significantly correlated with the rate of pCR in the QNBC group (p=0.02, p=0.04, and p=0.03, respectively). In contrast, no significant association was observed between pCR and clinical-pathological features in the TNBC AR+ group.

Conclusion:

Our results suggested that the AR expression in TNBC may be applied as a predictive marker for NAC. TNBC AR+ had a lower rate of pCR compared with QNBC, suggesting that this subtype may have a partial chemoresistance.

Significance of glucocorticoid signaling in triple-negative breast cancer patients: a newly revealed interaction with androgen signaling

PURPOSE

Chemotherapy is the only current effective systemic treatment for triple-negative breast cancer (TNBC) patients. Therefore, the identification of active biological pathways that could become therapeutic targets is crucial. In this study, considering the well-reported biological roles of glucocorticoid and androgen receptors (GR, AR) in TNBC, we attempted to explore the effects of glucocorticoids (GCs) on cell kinetics as well as the potential interaction between GR and AR in TNBC.

METHODS

We first explored the association between the status of GR, AR, and/or GCs-metabolizing enzymes such as 11β-hydroxysteroid dehydrogenase (11βHSD) 1 and 2 and the clinicopathological variables of the TNBC patients. Thereafter, we also studied the effects of dexamethasone (DEX) with/without dihydrotestosterone (DHT) on TNBC cell lines by assessing the cell proliferation, migration and GC response genes at the transcriptional level.

RESULTS

GR positivity in carcinoma cells was significantly associated with adverse clinical outcome of the patients and AR positivity was significantly associated with lower histological grade and Ki-67 labeling index of the cases examined. In particular, AR positivity was significantly associated with decreased risks of developing recurrence in GR-positive TNBC patients. The subsequent in vitro studies revealed that DEX-promoted cell migration was inhibited by the co-treatment with DHT in GR/AR double-positive HCC38 cells. In addition, DHT inhibited the DEX-increased serum and glucocorticoid-regulated kinase-1 (SGK1) mRNA expression.

CONCLUSION

This is the first study to reveal that the interaction of GR and AR did influence the clinical outcome of TNBC patients and GCs induced cell migration in TNBC cells.

Response to mTOR and PI3K inhibitors in enzalutamide-resistant luminal androgen receptor triple-negative breast cancer patient-derived xenografts

Luminal androgen receptor (LAR) breast cancer accounts for 10% of all triple-negative breast cancers (TNBC). Anti-androgen therapy for this subtype is in development, but yields only partial clinical benefits. In this study, we aimed to characterize the genomic alterations of LAR TNBC, to analyze activation of the PI3K signaling pathway and to compare the response to PI3K pathway inhibitors with that to anti-androgen therapy in patient-derived xenografts (PDX) of LAR TNBC.

Methods: Four LAR PDX models were identified, on the basis of their transcriptomic profiles, in a cohort of 57 PDX models of TNBC. The expression of AR-related genes, basal and luminal cytokeratins and EMT genes was analyzed by RT-PCR and IHC. AKT1 and PIK3CA mutations were identified by targeted NGS, and activation of the PI3K pathway was analyzed with a reverse-phase protein array. Three LAR PDXs with a PIK3CA or AKT1 mutation were treated with the AR inhibitor enzalutamide, a PI3K inhibitor, a dual PI3K-mTOR inhibitor and a mTORC1-mTORC2 inhibitor. Finally, we screened a clinical cohort of 329 TNBC for PIK3CA and AKT1 hotspot mutations.

Results: LAR TNBC PDXs were significantly enriched in PIK3CA and AKT1 mutations, and had higher levels of luminal-androgen-like gene expression and a higher PI3K pathway protein activation score than other TNBC subtypes. Immunohistochemistry analysis revealed strong expression of the luminal cytokeratin CK18 and AR in three LAR PDX models. We found that mTOR and PI3K inhibitors had marked antitumor activity in vivo in PDX harboring genomic alterations of PIK3CA and AKT1 genes that did not respond to the AR antagonist enzalutamide. PIK3CA mutations were detected in more than one third of AR+ TNBC from patients (38%), and only 10% of AR-negative TNBC.

Conclusion: Our results for PDX models of LAR TNBC resistant to enzalutamide indicate that PIK3CA and AKT1 are potential therapeutic targets.