A functionally significant cross-talk between androgen receptor and ErbB2 pathways in estrogen receptor negative breast cancer. Neoplasia. 2008;10:542-548. [PMID: 18516291 DOI: 10.1593/neo.08274]

Paving the path ForwARd: Advances and challenges in androgen receptor targeting in breast cancer

The role of androgen receptors (AR) in breast cancer is crucial for preclinical and clinical research. While AR-targeted therapy is a standard treatment for prostate cancer, the application of this therapeutic strategy to breast cancer has not been established. Indeed, AR is expressed in around 60-90% of breast cancers, making it imperative that we learn more about its prognostic and predictive impacts and targeting potential in breast cancer. Over the past decade, AR-targeted therapies ─ including AR antagonists and selective AR modulators ─ have shown promise in breast cancer treatment. However, an incomplete understanding of AR's role across breast cancer subtypes hinders clinical application. The lack of standardized AR expression thresholds further complicates patient selection, underscoring the urgent need for biomarker-driven strategies to optimize AR-targeted approaches in breast cancer. In this review, we provide an overview of a clinical perspective of AR in breast cancer by discussing AR biology, AR as a biomarker, and AR-targeted therapy development. We present our review with a particular emphasis on the distinct roles of AR in ER-positive (ER+) and ER-negative (ER-) breast cancer subtypes. Finally, the paper addresses the hurdles that have impeded the development of a robust clinical landscape for AR-targeted therapies and possible solutions for overcoming these challenges.

Looking beyond the ER, PR, and HER2: what's new in the ARsenal for combating breast cancer?

Breast cancer (BrCa) is a complex and heterogeneous disease with diverse molecular subtypes, leading to varied clinical outcomes and posing significant treatment challenges. The increasing global burden of BrCa, particularly in low- and middle-income countries, underscores the urgent need for more effective therapeutic strategies. The androgen receptor (AR), expressed in a substantial proportion of breast cancer cases, has emerged as a potential biomarker and therapeutic target. In breast cancer, AR exhibits diverse functions across subtypes, often interacting with other hormone receptors, thereby influencing tumor progression and treatment responses. This intricate interplay is further complicated by the presence of constitutively expressed AR splice variants (AR-Vs) that drive resistance to AR-targeting therapies through structural rearrangements in the domains and activation of aberrant signaling pathways. Although AR-targeting drugs, initially developed for prostate cancer (PCa), have shown promise in AR-positive breast cancer, significant gaps remain in understanding AR's precise functions and therapeutic potential. The systemic management of breast cancer is guided primarily by theranostic biomarkers; ER, PR, HER2, and Ki67 which also dictate the breast cancer classification. The ubiquitous expression of AR in BrCa and the emergence of AR-Vs can assist the management of disease complementing the standard of care. This article provides a comprehensive overview of AR and its splice variants in the context of breast cancer, highlighting their prognostic and predictive value across different subtypes looking beyond the conventional ER, PR, and HER2 status. This review also raises the possibility of using AR splice variants in predicting tumor aggressiveness. From the settings of developing nations, this may provide useful insight by integrating recent advances in AR-targeted therapies and exploring their translational potential, emphasizing the critical need for further research to optimize AR-based therapeutic strategies for breast cancer management.

Treatments Targeting the Androgen Receptor and Its Splice Variants in Breast Cancer

Breast cancer is a major cause of death worldwide. The complexity of endocrine regulation in breast cancer may allow the cancer cells to escape from a particular treatment and result in resistant and aggressive disease. These breast cancers usually have fewer treatment options. Targeted therapies for cancer patients may offer fewer adverse side effects because of specificity compared to conventional chemotherapy. Signaling pathways of nuclear receptors, such as the estrogen receptor (ER), have been intensively studied and used as therapeutic targets. Recently, the role of the androgen receptor (AR) in breast cancer is gaining greater attention as a therapeutic target and as a prognostic biomarker. The expression of constitutively active truncated AR splice variants in breast cancer is a possible mechanism contributing to treatment resistance. Therefore, targeting both the full-length AR and AR variants, either through the activation or suppression of AR function, depending on the status of the ER, progesterone receptor, or human epidermal growth factor receptor 2, may provide additional treatment options. Studies targeting AR in combination with other treatment strategies are ongoing in clinical trials. The determination of the status of nuclear receptors to classify and identify patient subgroups will facilitate optimized and targeted combination therapies.

Small molecule inhibition of TFF3 overcomes tamoxifen resistance and enhances taxane efficacy in ER+ mammary carcinoma

Even though tamoxifen has significantly improved the survival of estrogen receptor positive (ER+) mammary carcinoma (MC) patients, the development of drug resistance with consequent disease recurrence has limited its therapeutic efficacy. Trefoil factor-3 (TFF3) has been previously reported to mediate anti-estrogen resistance in ER+MC. Herein, the efficacy of a small molecule inhibitor of TFF3 (AMPC) in enhancing sensitivity and mitigating acquired resistance to tamoxifen in ER+MC cells was investigated. AMPC induced apoptosis of tamoxifen-sensitive and resistant ER+MC cells and significantly reduced cell survival in 2D and 3D culture in vitro. In addition, AMPC reduced cancer stem cell (CSC)-like behavior in ER+MC cells in a BCL2-dependent manner. Synergistic effects of AMPC and tamoxifen were demonstrated in ER+MC cells and AMPC was observed to improve tamoxifen efficacy in tamoxifen-sensitive cells and to re-sensitize cells to tamoxifen in tamoxifen-resistant ER+MC in vitro and in vivo. Additionally, tamoxifen-resistant ER+MC cells were concomitantly resistant to anthracycline, platinum and fluoropyrimidine drugs, but not to Taxanes. Taxane treatment of tamoxifen-sensitive and resistant ER+MC cells increased TFF3 expression indicating a combination vulnerability for tamoxifen-resistant ER+MC cells. Taxanes increased CSC-like behavior of tamoxifen-sensitive and resistant ER+MC cells which was reduced by AMPC treatment. Taxanes synergized with AMPC to promote apoptosis and reduce CSC-like behavior in vitro and in vivo. Hence, AMPC restored the sensitivity of tamoxifen and enhanced the efficacy of Taxanes in tamoxifen-resistant ER+MC. In conclusion, pharmacological inhibition of TFF3 may serve as an effective combinatorial therapeutic strategy for the treatment of tamoxifen-resistant ER+MC.

Androgen Receptor Expression in ER and PR Negative Breast Cancer-A Study from a Tertiary Hospital in Northern India

Sumeet SidhuObjectives  Breast cancer is the leading cause of cancer-related deaths in women. Estrogen (ER) and progesterone receptor (PR) status and Her2 overexpression are major determinants in therapeutic decision making. Triple-negative breast cancers (TNBCs) have limited treatment options. Androgen receptor (AR) expression opens up therapeutic avenues for these patients. The aim of this article was to study the immunohistochemical expression of ARs in ER and PR Negative breast carcinomas and to correlate AR expression with various clinical, histopathological, and other immunohistochemical parameters. Materials and Methods  It is a cross-sectional study including 105 ER and PR Negative cases of breast carcinoma. Clinical parameters, histopathology, and immunohistochemical expression of AR, Her2, and Ki67 were analyzed in all cases. Results  AR expression was observed in 63.8% of ER and PR Negative breast cancers. In this group, AR expression was strongly associated with Her2 co-expression (89.2%) as compared to TNBCs (45.8%); p -value = 0.0002. Significant correlation was also observed between AR expression and tumor necrosis ( p -value = 0.034) and postmenopausal status ( p  = 0.007). Conclusion  Our study shows that significant proportion of ER and PR Negative breast carcinomas (ER- PR- Her2+ and TNBCs) show AR expression. We strongly recommend routine evaluation of all hormone receptor-negative breast carcinomas for AR status by immunohistochemistry.

Correlation between androgen receptor expression and pathological response rate in pre-operative HER2-positive breast cancer patients

PURPOSE

In this study, we aimed to explore the potential significance of AR expression in HER2-positive breast cancer patients who underwent neoadjuvant targeted therapy. Specifically, we investigated the correlation between AR expression levels and pathological complete response (pCR) rates. Our objective was to determine whether there were significant differences in pCR rates among HER2-positive breast cancer patients with different levels of AR expression.

METHODS

We conducted a retrospective analysis of 258 HER-2 positive breast cancer patients who underwent neoadjuvant dual-blocked standard therapy (following the NCCN Guideline 2021) at three breast cancer centers in southwest China. We analyzed the clinicopathological features and pCR rates of these patients. The cut-off value for AR expression level was calculated as the median value of 70%. We used the chi-square test to investigate the correlation between AR expression level and pCR rate, as well as other clinicopathological features.

RESULTS

Out of the 258 patients analyzed, 154 (59.69%) achieved pCR. Based on the cut-off value of 70%, AR expression level was classified as low (AR ≤ 70%) or high (AR > 70%) expression. Our analysis revealed a significant correlation between AR expression level and pCR rate in HER2-positive breast cancer patients (P = 0.031). We also found a significant association between pCR rate and clinical stage (P = 0.033) and chemotherapy regimen (P = 0.034). Furthermore, subgroup analyses showed that the pCR rate was higher in patients with high AR expression levels compared to those with low AR expression levels. Additionally, we observed that patients with an ER/AR ratio of less than 1 had a higher pCR rate than those with an ER/AR ratio greater than 1 (P = 0.038).

CONCLUSION

Our study findings suggest that HER2-positive breast cancer patients with high AR expression levels may achieve higher pCR rates when treated with neoadjuvant dual-blocked therapy. Overall, our results support the idea that AR expression levels have a significant correlation with pCR rates in HER2-positive breast cancer patients receiving this particular form of treatment.

Integrins and Actions of Androgen in Breast Cancer

Androgen has been shown to regulate male physiological activities and cancer proliferation. It is used to antagonize estrogen-induced proliferative effects in breast cancer cells. However, evidence indicates that androgen can stimulate cancer cell growth in estrogen receptor (ER)-positive and ER-negative breast cancer cells via different types of receptors and different mechanisms. Androgen-induced cancer growth and metastasis link with different types of integrins. Integrin αvβ3 is predominantly expressed and activated in cancer cells and rapidly dividing endothelial cells. Programmed death-ligand 1 (PD-L1) also plays a vital role in cancer growth. The part of integrins in action with androgen in cancer cells is not fully mechanically understood. To clarify the interactions between androgen and integrin αvβ3, we carried out molecular modeling to explain the potential interactions of androgen with integrin αvβ3. The androgen-regulated mechanisms on PD-L1 and its effects were also addressed.

Comprehensive characterization of HER2-low breast cancers: implications in prognosis and treatment

BACKGROUND

HER2-low cancers are heterogeneous with different degrees of HER2 expression and hormone receptor (HR) status. Currently, its analysis is mostly focused on the standard clinic-pathologic features or common biomarkers expression, without considering the heterogeneity within the category. A further characterization and understanding of this cancer subgroup will facilitate its management.

METHODS

A large cohort of HER2-negative cancers (N = 1464) was included. The HER2-low (N = 412) and HER2-zero cancers (N = 1052) were compared and correlated with a comprehensive panel of clinico-pathologic features and biomarker expression according to different HER2 expressions and HR statuses. The prognostic values of these features in HER2-low cancers were also evaluated.

FINDINGS

The characteristics of HER2-low breast cancers, as compared to HER2-zero, varied with the HR status. HER2-low luminal cancers were associated with younger age, larger tumor, high pAKT and high HLA expression. Among TNBCs, opposite trends in age and tumor size were found. Additionally, HER2-low TNBC showed less necrosis, higher pN, lower c-kit and CK14 than HER2-zero cancers. Nonetheless, regardless of HR status, HER2-low status was associated with increased COX2 and AR expression, implicated in the biology of HER2-low cancers. HER2-low cancers showed high expression of HLAs in tumors and PD-L1 in immune cells. In particular, the co-expression of HLAs was found to be associated with better survival in HER2-low cancers.

INTERPRETATION

This study revealed further characteristic of HER2-low breast cancers as compared to HER2-zero cancers, provided further insights into its prognostication and therapeutic strategies.

FUNDING

Health and Medical Research Fund (08190586), Cheng Yue Pui Charity Foundation and CUHK direct grant.

Stranger Things: New Roles and Opportunities for Androgen Receptor in Oncology Beyond Prostate Cancer

The androgen receptor (AR) is one of the oldest therapeutic targets in oncology and continues to dominate the treatment landscape for advanced prostate cancer, where nearly all treatment regimens include some form of AR modulation. In this regard, AR remains the central driver of prostate cancer cell biology. Emerging preclinical and clinical data implicate key roles for AR in additional cancer types, thereby expanding the importance of this drug target beyond prostate cancer. In this mini-review, new roles for AR in other cancer types are discussed as well as their potential for treatment with AR-targeted agents. Our understanding of these additional functions for AR in oncology expand this receptor's potential as a therapeutic target and will help guide the development of new treatment approaches.

Potential Therapeutic Targets for Luminal Androgen Receptor Breast Cancer: What We Know so Far

Luminal Androgen Receptor Breast Cancers (LAR BCs) are characterized by a triple negative phenotype and by the expression of Androgen Receptor (AR), coupled with luminal-like genomic features. This unique BC subtype, accounting for about 10% of all triple negative BC, has raised considerable interest given its ill-defined clinical behavior and the chance to exploit AR as a therapeutic target. The complexity of AR activity in BC cells, as revealed by decades of mechanistic studies, holds promise to offer additional therapeutic options beyond mere AR inhibition. Indeed, preclinical and translational evidence showed that several pathways and mediators, including PI3K/mToR, HER2, BRCA1, cell cycle and immune modulation, can be tackled in LAR BCs. Moving from bench to bedside, several clinical trials tested anti-androgen therapies in LAR BCs, but their results are inconsistent and often disappointing. More recently, studies exploring combinations of anti-androgen agents with other targeted therapies have been designed and are currently ongoing. While the results from these trials are awaited, a concerted effort will be needed to find the biological vulnerabilities of LAR BCs which may disclose new and effective therapeutic targets, eventually improving patients' outcomes.

Role of androgen receptor signaling pathway-related lncRNAs in the prognosis and immune infiltration of breast cancer

Androgen receptor (AR) is strong association with breast cancer (BRCA). We aimed to investigate the effect of the androgen receptor signaling pathway-related long non-coding RNAs (ARSP-related lncRNAs) on the process of subtype classification and the tumor microenvironment (TME) of breast cancer (BRCA). Our study screen ARSP-related lncRNAs for the construction of a risk model. The single-sample gene set enrichment analysis (ssGSEA) method was used to detect the differences between the immune responses generated by the patients belonging to the low- and high-risk groups. The relationship between the ARSP-related lncRNAs and TME was explored following the process of cluster analysis. The univariate Cox analysis and the Lasso regression analysis method was used to screen nine of these lncRNAs to develop a risk model. It was observed that risk score could function as an independent prognostic factor, affecting the prognoses of patients suffering from BRCA. The validity of the model was assessed by analyzing the generated calibration curves and a nomogram. Additionally, the effect of the risk score on the extent of immune cell infiltration realized in TME was explored. M2 macrophages correlated positively, whereas NK cells, CD4+ T cells, and naive B cells correlated negatively with the risk score. Results obtained using the cluster analysis indicated that immune scores correlated with clustered subtypes. Finally, the risk score and cluster subtypes were analyzed to study the sensitivity of the patients toward different drugs to identify the appropriate therapeutic agents. The prognoses of patients suffering from BRCA can be accurately predicted by ARSP-related lncRNAs.

Proxalutamide in patients with AR-positive metastatic breast cancer: Results from an open-label multicentre phase Ib study and biomarker analysis

AIM

Proxalutamide is a novel second-generation non-steroidal androgen receptor (AR) antagonist. This study aimed to evaluate the preliminary efficacy and safety of proxalutamide in patients with AR-positive metastatic breast cancer (AR⁺ mBC).

METHODS

In this open-label, dose-expansion, multicentre phase Ib trial, patients with AR⁺ mBC (immunohistochemistry [IHC] ≥1%) received proxalutamide orally once daily. Two proxalutamide dose cohorts (cohort A: 200 mg; cohort B: 300 mg) were sequentially investigated. Primary endpoints were disease control rate (DCR) at 8 and 16 weeks and recommended phase II dose (RP2D).

RESULTS

Forty-five patients with three median lines (range, 1-13) prior systemic therapy were enrolled (cohort A, n = 30; cohort B, n = 15). Among 39 evaluable patients, DCR at 8 and 16 weeks was 25.6% (95% confidence interval [CI], 11.9-39.4%), with 26.9% in cohort A and 23.1% in cohort B. No patient achieved partial response or complete response. Proxalutamide 200 mg/day was determined as RP2D. The 6-month progression-free survival (PFS) rate was 19.6% (95% CI, 10.2-37.5%). In the triple-negative subgroup, DCR at 8 weeks was 38.5%, with median PFS of 9.1 months (95% CI, 7.8-NA) in those who achieved response at 8 weeks (n = 5). Most common grade 3/4 adverse events were aspartate aminotransferase increase (8.9%) and γ-glutamyltransferase increase (8.9%). By biomarker analysis, patients with moderate AR expression of IHC (26%-75%), PIK3CA pathogenic mutations, or <60 ng/ml cell-free DNA yield showed longer PFS.

CONCLUSION

Proxalutamide showed promising anti-tumour activity with good tolerability in patients with heavily pretreated AR⁺ mBC, supporting further investigation.

TRIAL REGISTRATION

This clinical study was prospectively registered at chinadrugtrials.org.cn (Identifier: CTR20170757) and clinical trials.gov (Identifier: NCT04103853).

FOXA1 in Breast Cancer: A Luminal Marker with Promising Prognostic and Predictive Impact

The present review focuses on the function of the forkhead protein FOXA1 in breast cancer (BC) in relation to steroid hormone receptors. We explored the currently available analytic approaches for FOXA1 assessment both at gene and protein levels, comparing the differences between the available techniques used for its diagnostic assessment. In addition, we elaborated on data regarding the prognostic and predictive role of this marker in BC based on several studies that evaluated its expression in relation to the outcome and/or response to therapy. FOXA1, similar to the androgen receptor (AR), may have a dual role in BC according to hormonal status. In luminal cancers, its expression contributes to a better prognosis, while in triple-negative breast cancers (TNBC), it implies an adverse outcome. Consequently, we observed that FOXA1-positive expression in a neoadjuvant setting may predict a lack of response in luminal BC as opposed to TNBC, in which FOXA1 allegedly increases its chemosensitivity. In conclusion, considering its accessible and convenient identification by immunohistochemistry, its important impact on prognosis, and its suitability to identify patients with different responses to chemotherapy, we propose that FOXA1 could be tested in routine diagnostics as an additional prognostic and predictive marker in BC.

Integration of androgen hormones in endometrial cancer biology

Endometrial cancer (EC) is a gynecological pathology that affects the uterine inner lining. In recent years, genomic studies revealed continually evolving mutational landscapes of endometrial tumors that hold great potential for tailoring therapeutic strategies. This review aims to broaden our knowledge of EC biology by focusing on the role of androgen hormones. First, we discuss epidemiological evidence implicating androgens with EC pathogenesis and cover their biosynthesis and metabolism to bioactive 11-oxyandrogens. Next, we explore the endometrial tumor tissue and the altered microbiota as alternative sources of androgens and their 11-oxymetabolites in EC patients. Finally, we discuss the biological significance of androgens' genomic and nongenomic signaling as part of a medley of pathways ultimately deciding the fate of cells.

Transcriptome profiling and proteomic validation reveals targets of the androgen receptor signaling in the BT-474 breast cancer cell line

BACKGROUND

Accumulating evidence suggests that the androgen receptor (AR) and its endogenous ligands influence disease progression in breast cancer (BCa). However, AR-mediated changes in BCa differ among the various BCa subtypes according to their hormone receptor profile [i.e., presence/absence of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2, (HER2)]. Thus, we explored the androgen-regulated transcriptomic changes in the ER⁺PR⁺HER2⁺ BCa cell line, BT-474, and compared them with PR-mediated changes.

METHODS

We performed RNA sequencing analysis in treated BT-474 cells with dihydrotestosterone (DHT) and progesterone. Validation of the top ten differentially androgen-regulated genes and a number of other genes found in enriched signaling pathways was performed by qRT-PCR in BT-474 and other BCa cell lines. In addition, a parallel reaction monitoring targeted proteomic approach was developed to verify selected transcripts at the protein level.

RESULTS

In total 19,450 transcripts were detected, of which 224 were differentially regulated after DHT treatment. The increased expression of two well-known androgen-regulated genes, KLK2 (p < 0.05) and KLK3 (p < 0.001), confirmed the successful androgen stimulation in BT-474 cells. The transcription factor, ZBTB16, was the most highly upregulated gene, with ~ 1000-fold change (p < 0.001). Pathway enrichment analysis revealed downregulation of the DNA replication processes (p < 0.05) and upregulation of the androgen signaling and fatty acid metabolism pathways (p < 0.05). Changes related to progesterone treatment showed opposite effects in gene expression than DHT treatment. Similar expression profiles were observed among other BCa cell lines expressing high levels of AR (ZR75.1 and MBA-MB-453). The parallel reaction monitoring targeted proteomic analysis further confirmed that altered protein expression (KLK3, ALOX15B) in the supernatant and cell lysate of DHT-treated BT-474 cells, compared to control cells.

DISCUSSION

Our findings suggest that AR modulates the metabolism of BT-474 cells by affecting the expression of a large number of genes and proteins. Based on further pathway analysis, we suggest that androgen receptor acts as a tumor suppressor in the BT-474 cells.

BC-DETECT: combined detection of serum HE4 and TFF3 improves breast cancer diagnostic efficacy

BACKGROUND

Early accurate breast cancer (BC) diagnosis is critical in disease management. Mammography has been widely used. However, its radiation, and high false-negative and -positive results have always been a concern. We evaluated combined detection of human epididymal protein 4 (HE4) and trefoil factor 3 (TFF3) as substitute method to enhance BC diagnosis.

METHODS

HE4 and TFF3 blood levels were determined by ELISA in sera of 120 BC patients and 80 women (40 healthy and 40 benign breast disease) as controls. Receiver-operating characteristic curve was applied for evaluation diagnostic power of each biomarker and their combination.

RESULTS

In BC patients, serum HE4 [5 (2-11.9) vs. 3.1 (1.8-5.4) and 1 (1-3.5); P = 0.022] and TFF3 [5.3 (4.5-6.7) vs. 4.7 (4-4.8) and 3.9 (3-4.4); P = 0.027] were significantly higher than that in benign and healthy groups, respectively. Both HE4 (AUC = 0.783; P < 0.0001) and TFF3 (AUC = 0.759; P < 0.0001) had superior BC diagnostic ability compared to CEA and CA-15.3. Logistic regression analysis revealed simplified index BC-DETECT = HE4 + TFF3, and its values were significantly (P = 0.0132) elevated in BC (10.9 (8.4-17.2) compared to benign (7.2 (5.4-10.1)) and healthy (5.1 (4-6.3)) controls. AUC of BC-DETECT for BC prediction was (AUC = 0.850; P < 0.0001) with sensitivity, specificity, and positive and negative predictive values and accuracy of 84.2%, 70%, 80.8%, 74.7%, and 78.5%, respectively. High BC-DETECT levels were associated with tumor non-luminal subtypes, late stage, high grade, large size, lymph-node invasion, and multiple lesions.

CONCLUSIONS

BC-DETECT is inexpensive, rapid, and easy to perform and reliably guides BC early detection. Moreover, the association between elevated BC-DETECT values and disease severity may propose its potential role as prognostic marker.

Potential epigenetic modifications implicated in triple- to quadruple-negative breast cancer transition: a review

Current research on triple-negative breast cancer (TNBC) has resulted in delineation into the quadruple-negative breast cancer (QNBC) subgroup. Epigenetic modifications such as DNA methylation, histone posttranslational modifications and associated changes in chromatin architecture have been implicated in breast cancer pathogenesis. Herein, the authors highlight genes with observed epigenetic modifications that are associated with more aggressive TNBC/QNBC pathogenesis and possible interventions. Advanced literature searches were done on PubMed/MEDLINE, Scopus and Google Scholar. The results suggest that nine epigenetically altered genes/differentially expressed proteins in addition to the downregulated androgen receptor are associated with TNBC aggressiveness and could be implicated in the TNBC to QNBC transition. Thus, restoring the normal expression of these genes via epigenetic reprogramming could be therapeutically beneficial to TNBC and QNBC patients.

Androgen receptor in breast cancer: The "5W" questions

Androgen receptor (AR) is expressed in 60-70% of breast cancers (BCs) and the availability of anti-AR compounds, currently used for treating prostate cancer, paves the way to tackle specifically AR-positive BC patients. The prognostic and predictive role of AR in BC is a matter of debate, since the results from clinical trials are not striking, probably due to both technical and biological reasons. In this review, we aimed to highlight WHAT is AR, describing its structure and functions, WHAT to test and HOW to detect AR, WHERE AR should be tested (on primary tumor or metastasis) and WHY studying this fascinating hormone receptor, exploring and debating on its prognostic and predictive role. We considered AR and its ratio with other hormone receptors, analyzing also studies including patients with ductal carcinoma in situ and with early and advanced BC, as well. We also emphasized the effects that both other hormone receptors and the newly emerging androgen-inducible non coding RNAs may have on AR function in BC pathology and the putative implementation in the clinical setting. Moreover, we pointed out the latest results by clinical trials and we speculated about the use of anti-AR therapies in BC clinical practice.

Triple-negative apocrine carcinoma as a rare cause of a breast lump in a Syrian female: a case report and review of the literature

BACKGROUND

Apocrine carcinoma is a rare tumor that constitutes < 4% of all breast malignancies, characterized by the proliferation of large atypical cells with strictly defined borders, abundant eosinophilic cytoplasm, large nuclei, and prominent nucleoli in more than 90% of tumor cells. Triple-negative apocrine carcinoma is a rare molecular subtype that constitutes less than 1% of triple-negative breast cancers and is characterized by negative expression of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor, with positive expression of androgen receptor.

CASE PRESENTATION

We report a case of a 45-year-old Syrian female who presented to our hospital due to a painless palpable mass in her left breast. Following physical and radiological examinations, an excisional biopsy was performed. Microscopic examination of the specimen followed by immunohistochemical staining revealed the diagnosis of a triple-negative apocrine carcinoma.

CONCLUSION

Triple-negative apocrine carcinoma is an extremely rare neoplasm that must be considered in the differential diagnoses of breast lesions through detailed clinical, histological, and immunohistochemical correlations. In our manuscript, we aimed to present the first case report of a Syrian female who was diagnosed with a triple-negative apocrine carcinoma, aiming to highlight the importance of detailed clinical, histological and immunohistochemical correlations with a detailed review of diagnostic criteria, molecular characteristics, and treatment recommendations.

Multiomics analysis of serial PARP inhibitor treated metastatic TNBC inform on rational combination therapies

In a pilot study, we evaluated the feasibility of real-time deep analysis of serial tumor samples from triple negative breast cancer patients to identify mechanisms of resistance and treatment opportunities as they emerge under therapeutic stress engendered by poly-ADP-ribose polymerase (PARP) inhibitors (PARPi). In a BRCA-mutant basal breast cancer exceptional long-term survivor, a striking tumor destruction was accompanied by a marked infiltration of immune cells containing CD8 effector cells, consistent with pre-clinical evidence for association between STING mediated immune activation and benefit from PARPi and immunotherapy. Tumor cells in the exceptional responder underwent extensive protein network rewiring in response to PARP inhibition. In contrast, there were minimal changes in the ecosystem of a luminal androgen receptor rapid progressor, likely due to indifference to the effects of PARP inhibition. Together, identification of PARPi-induced emergent changes could be used to select patient specific combination therapies, based on tumor and immune state changes.

FOXA1: A Pioneer of Nuclear Receptor Action in Breast Cancer

The pioneering function of FOXA1 establishes estrogen-responsive transcriptomes in luminal breast cancer. Dysregulated FOXA1 chromatin occupancy through focal amplification, mutation, or cofactor recruitment modulates estrogen receptor (ER) transcriptional programs and drives endocrine-resistant disease. However, ER is not the sole nuclear receptor (NR) expressed in breast cancers, nor is it the only NR for which FOXA1 serves as a licensing factor. Receptors for androgens, glucocorticoids, and progesterone are also found in the majority of breast cancers, and their functions are also impacted by FOXA1. These NRs interface with ER transcriptional programs and, depending on their activation level, can reprogram FOXA1-ER cistromes. Thus, NR interplay contributes to endocrine therapy response and resistance and may provide a vulnerability for future therapeutic benefit in patients. Herein, we review what is known regarding FOXA1 regulation of NR function in breast cancer in the context of cell identity, endocrine resistance, and NR crosstalk in breast cancer progression and treatment.

Breast Cancer Consensus Subtypes: A system for subtyping breast cancer tumors based on gene expression

Breast cancer is heterogeneous in prognoses and drug responses. To organize breast cancers by gene expression independent of statistical methodology, we identified the Breast Cancer Consensus Subtypes (BCCS) as the consensus groupings of six different subtyping methods. Our classification software identified seven BCCS subtypes in a study cohort of publicly available data (n = 5950) including METABRIC, TCGA-BRCA, and data assayed by Affymetrix arrays. All samples were fresh-frozen from primary tumors. The estrogen receptor-positive (ER+) BCCS subtypes were: PCS1 (18%) good prognosis, stromal infiltration; PCS2 (15%) poor prognosis, highly proliferative; PCS3 (13%) poor prognosis, highly proliferative, activated IFN-gamma signaling, cytotoxic lymphocyte infiltration, high tumor mutation burden; PCS4 (18%) good prognosis, hormone response genes highly expressed. The ER− BCCS subtypes were: NCS1 (11%) basal; NCS2 (10%) elevated androgen response; NCS3 (5%) cytotoxic lymphocyte infiltration; unclassified tumors (9%). HER2+ tumors were heterogeneous with respect to BCCS.

Apocrine lesions of the breast

Apocrine change is recognised in benign, atypical and malignant lesions of the breast. Apocrine metaplasia, a frequent finding in the breast of women over the age of 25 years, is most commonly seen in benign cysts with a simple or papillary configuration. Apocrine change is also recognised in other benign lesions including sclerosing adenosis, now known as apocrine adenosis. Apocrine atypia usually refers to cytological atypia in which there is at least threefold variation in nuclear size but architectural atypia may also occur. The distinction between atypical apocrine hyperplasia and non-high-grade apocrine ductal carcinoma in situ may be difficult due to the relative rarity of these entities and the lack of validated diagnostic criteria. Lobular carcinoma in situ (LCIS) with apocrine change is considered to be a variant of pleomorphic LCIS. An apocrine variant of encapsulated papillary carcinoma is also recognised. Apocrine change is described in invasive carcinoma, including no special type, lobular, micropapillary and mucinous variants. The recent WHO 2019 update recognises 'carcinoma with apocrine differentiation' as a special type breast carcinoma based on the presence of apocrine morphology in at least 90% of the tumour. Tumours with apocrine morphology are usually but not always hormone receptor negative. Human epidermal growth factor receptor 2 (HER-2) status is variable. Molecular studies have identified breast tumours with apocrine features and high expression of androgen receptor mRNA including 'luminal androgen receptor tumours' and 'molecular apocrine tumours'. The term 'pure apocrine carcinoma' has been proposed to describe an invasive carcinoma with apocrine morphology that is oestrogen and progesterone receptor negative and androgen receptor positive. HER-2 status may be positive or negative. This article reviews the pathology of benign, atypical and malignant apocrine lesions of the breast, with emphasis on diagnostic criteria including an approach to evaluation of apocrine lesions on needle core biopsy, and recent advances in our understanding of invasive apocrine carcinoma.

Intrinsic Subtypes and Androgen Receptor Gene Expression in Primary Breast Cancer. A Meta-Analysis

The androgen receptor (AR) is frequently expressed in breast cancer (BC), but its association with clinical and biological parameters of BC patients remains unclear. Here, we investigated the association of AR gene expression according to intrinsic BC subtypes by meta-analysis of large-scale microarray transcriptomic datasets. Sixty-two datasets including 10315 BC patients were used in the meta-analyses. Interestingly, AR mRNA level is significantly increased in patients categorized with less aggressive intrinsic molecular subtypes including, Luminal A compared to Basal-like (standardized mean difference, SMD: 2.12; 95% confidence interval, CI: 1.88 to 2.35; p < 0.001) or when comparing Luminal B to Basal-like (SMD: 1.53; CI: 1.33 to 1.72; p < 0.001). The same trend was observed when analyses were performed using immunohistochemistry-based surrogate subtypes. Consistently, the AR mRNA expression was higher in patients with low histological grade (p < 0.001). Furthermore, our data revealed higher levels of AR mRNA in BC patients expressing either estrogen or progesterone receptors (p < 0.001). Together, our findings indicate that high mRNA levels of AR are associated with BC subgroups with the less aggressive clinical features.

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.

Androgen receptor expression in breast cancer: Implications on prognosis and treatment, a brief review

Approximately 70%-85% of breast cancers express androgen receptors (ARs). The role of AR in breast cancer pathogenesis is currently in exploration. Both androgens and anti-androgens have demonstrated variable inhibitory and stimulatory effects in AR-positive breast cancer depending on estrogen receptor and HER2 co-expression. Androgen signaling pathways interact with other critical cellular pathways, such as the PI3K/AKT/mTOR, Ras/Raf/MAPK/ERK, Wnt/β-catenin, and estrogen signaling pathways. Therapeutic exploitation of AR has been the crux of management of prostate cancer for decades. In recent years there has been increasing interest in AR as a novel therapeutic target in breast cancer. There have been many early phase clinical trials evaluating the safety and efficacy of various AR-targeted agents in breast cancer. Some of these studies have shown promising clinical benefits. Studies of biomarkers to identify the patients likely to benefit from AR-targeted therapies are currently in progress. Besides, AR expression may be an important prognostic and predictive marker for breast cancer, which needs to be defined better in future studies.

Neoadjuvant targeted therapy for apocrine carcinoma of the breast: A case report

BACKGROUND

Apocrine carcinoma of the breast is a special type of invasive ductal carcinoma of the breast that is rare in clinical practice. Neoadjuvant therapy, especially neoadjuvant targeted therapy, has rarely been reported for apocrine carcinoma of the breast.

CASE SUMMARY

A 63-year-old woman presented with apocrine carcinoma of the left breast underwent core needle biopsy. The patient was diagnosed with apocrine carcinoma by immunohistochemical staining and negative hormone status (estrogen receptor and progesterone receptor) but showed overexpression of human epidermal factor receptor 2 (HER-2). Moreover, positive expression of androgen receptor (approximately 60%) and gross cystic disease fluid protein 15 was observed. The patient was treated with neoadjuvant targeted therapy consisting of the TCH regimen (docetaxel, carboplatin area under curve 6 and trastuzumab) every 21 d. The mass in the left breast was significantly reduced, and pain in the breast and left upper arm also improved.

CONCLUSION

HER-2 positive apocrine carcinoma of the breast can be improved by neoadjuvant chemotherapy combined with targeted therapy.

Primary De novo ductal adenocarcinoma of the lacrimal gland

BACKGROUND

Primary ductal adenocarcinoma of the lacrimal gland is a rare and aggressive malignant epithelial lacrimal gland neoplasm, morphologically and phenotypically resembles salivary duct carcinoma, and both strongly resemble infiltrating ductal carcinoma of breast.

METHOD

Retrospective Chart review of cases of malignant lacrimal gland tumors from 2013 July to 2020 July. Authors describe the clinico radiological, morphological and immunohistochemical features of primary ductal adenocarcinoma (PDA) of lacrimal gland. Extensive review of literature of PDA of lacrimal gland and salivary gland ductal carcinoma has been performed.

RESULTS

Retrospective chart review of the last 7 years yielded 22 malignant lacrimal gland neoplasms of which 4 cases demonstrated features of primary ductal adenocarcinoma of lacrimal gland, 2/4 cases showed an evidence of a pre existing pleomorphic adenoma and 2 were found to be de novo ductal adenocarcinomas. PDA of lacrimal gland showed expression of CK7, CK19, AR, HER2, cyclin D1 and were negative for CK5/14, CK 20, ER, PR, PSA, TTF-1, S-100 and SMA. Expression of GCDFP-15 was noted in one case. The presence of multiple events of loco-regional recurrences and/or distant metastasis necessitated a multidisciplinary approach.

CONCLUSIONS

Authors have expressed the need of clinical correlation; thorough tissue sampling and extensive immunohistochemical work up in identification of de novo PDA's and their molecular subtypes. A multi-institutional study might help in formulating the diagnostic criteria, identification of actionable targets, and thus study the role of targeted therapy in this rare and aggressive tumor which may result in better patient outcomes.

Role of androgen and microRNA in triple-negative breast cancer

Breast cancer (BC) is the most frequent type of malignancy affecting females worldwide. Molecular-based studies resulted in an identification of at least four subtypes of breast carcinoma, including luminal A and luminal B, Human growth factor receptor (HER-2)-enriched and triple-negative tumors (basal-like and normal breast-like). A proportion of BC cases are of the triple-negative breast cancer (TNBC) type. TNBC lacks the expression of estrogen receptor (ER), progesterone receptor (PR), and HER-2, and is known to express androgen receptor (AR) at considerable levels. AR has been shown to promote the progression of TNBC. However, the exact mechanisms have yet to be unraveled. One of these mechanisms could be through regulating the expression of microRNA (miRNA) molecules, which play an important regulatory role in BC through post-transcriptional gene silencing. Activation of AR controls the expression of miRNA molecules, which target selective mRNAs, consequently, affecting protein expression. In this review we attempt to elucidate the relations between AR and miRNA in TNBC.

ARe we there yet? Understanding androgen receptor signaling in breast cancer

The role of androgen receptor (AR) activation and expression is well understood in prostate cancer. In breast cancer, expression and activation of AR is increasingly recognized for its role in cancer development and its importance in promoting cell growth in the presence or absence of estrogen. As both prostate and breast cancers often share a reliance on nuclear hormone signaling, there is increasing appreciation of the overlap between activated cellular pathways in these cancers in response to androgen signaling. Targeting of the androgen receptor as a monotherapy or in combination with other conventional therapies has proven to be an effective clinical strategy for the treatment of patients with prostate cancer, and these therapeutic strategies are increasingly being investigated in breast cancer. This overlap suggests that targeting androgens and AR signaling in other cancer types may also be effective. This manuscript will review the role of AR in various cellular processes that promote tumorigenesis and metastasis, first in prostate cancer and then in breast cancer, as well as discuss ongoing efforts to target AR for the more effective treatment and prevention of cancer, especially breast cancer.

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.

AR/ER Ratio Correlates with Expression of Proliferation Markers and with Distinct Subset of Breast Tumors

The co-expression of androgen (AR) and estrogen (ER) receptors, in terms of higher AR/ER ratio, has been recently associated with poor outcome in ER-positive (ER+) breast cancer (BC) patients. The aim of this study was to analyze if the biological aggressiveness, underlined in ER+ BC tumors with higher AR/ER ratio, could be due to higher expression of genes related to cell proliferation. On a cohort of 47 ER+ BC patients, the AR/ER ratio was assessed by immunohistochemistry and by mRNA analysis. The expression level of five gene proliferation markers was defined through TaqMan^®-qPCR assays. Results were validated using 979 BC cases obtained from gene expression public databases. ER+ BC tumors with ratios of AR/ER ≥ 2 have higher expression levels of cellular proliferation genes than tumors with ratios of AR/ER < 2, in both the 47 ER+ BC patients (P < 0.001) and in the validation cohort (P = 0.005). Moreover, BC cases with ratios of AR/ER ≥ 2 of the validation cohort were mainly assigned to luminal B and HER2-enriched molecular subtypes, typically characterized by higher proliferation and poorer prognosis. These data suggest that joint routine evaluation of AR and ER expression may identify a unique subset of tumors, which show higher levels of cellular proliferation and therefore a more aggressive behavior.

Expression of androgen receptor and its regulatory molecule Lin28 in non-luminal subtype breast cancer

Androgen receptor (AR) was associated with favourable outcome in luminal breast cancer. However, the role of AR in non-luminal breast cancer remains inconclusive. The aim of the present study was to evaluate the clinical significance of the AR and its regulatory pathway in non-luminal subtypes of breast cancer. In total, 284 breast cancer patients were recruited from January 2007 to January 2016. Tissue microarrays were constructed from archival paraffin blocks and assessed for AR and its regulatory molecule, Lin28, by immunohistochemistry. The association between AR and Lin28 expression and clinicopathological parameters was analyzed. Results showed that AR and Lin28 were co-expressed. No association between these proteins and clinicopathological parameters, and survival outcome was found. However, a higher proportion of the patients with AR and Lin28 expression were observed in HER2 subtype. In conclusion, Lin28 may be a novel marker for prognosis and targeted for treatment in HER2 subtype breast cancer.

The expression and prognostic role of EBP1 and relationship with AR in HER2+ breast cancer

Human epidermal growth factor receptor (HER)-2 positive (HER2⁺) breast cancer (BC) has a poor survival rate and is more aggressive in nature. HER2-targeting agents could be beneficial for patients with HER2⁺ BC. In addition, targeted therapy and chemotherapy have been successfully used. However, a few patients are resistant to treatment. ErbB3 binding protein 1 (EBP1) binds to HER3 and inhibits the proliferation and invasive potential of tumor cells. However, its role in HER2⁺ BC has not been demonstrated. In this study, we aimed to analyze the relationship between androgen receptor (AR) and EBP1 expression in HER2⁺ BC. A total of 282 cases (140 cases of HER2⁺ invasive BC and 142 HER2-negative invasive BC) were included in this study. We performed immunohistochemistry (IHC) to analyze the expression of AR and EBP1; thereafter, we evaluated the relationship between these two biomarkers and estrogen receptor (ER), progesterone receptor (PR), HER2, p53, Ki67 expression, and other clinicopathological parameters. Of the HER2⁺ cases, 67 (47.9%) showed high expression of EBP1 (EBP1^high) and 73 (52.1%) showed low/no expression of EBP1 (EBP1^low/no). EBP1 expression was correlated with AR expression, histological grade, and lymphatic metastasis (p < 0.001, < 0.001, and 0.013, respectively). Kaplan-Meier analysis revealed that AR⁺ and EBP1^low/no group had poorer overall survival (OS) and disease-free survival (DFS) compared with other groups (AR^- and EBP1^low/no, AR⁺ and EBP1^high, and AR^- and EBP1^high). AR⁺ and EBP1^low/no expression were independent prognostic factors for OS and DFS in HER2+ BC. This study showed the clinicopathological role of EBP1 and AR in HER2+ BC. Targeting EBP1 may be an effective treatment strategy for patients with AR⁺ HER2⁺ BC.

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.

Consideration of breast cancer subtype in targeting the androgen receptor

The androgen receptor (AR) is a drug target in breast cancer, and AR-targeted therapies have induced tumor responses in breast cancer patients. In this review, we summarized the role of AR in breast cancer based on preclinical and clinical data. Response to AR-targeted therapies in unselected breast cancer populations is relatively low. Preclinical and clinical data show that AR antagonists might have a role in estrogen receptor (ER)-negative/AR-positive tumors. The prognostic value of AR for patients remains uncertain due to the use of various antibodies and cut-off values for immunohistochemical assessment. To get more insight into the role of AR in breast cancer, we additionally performed a retrospective pooled analysis to determine the prognostic value of the AR using mRNA profiles of 7270 primary breast tumors. Our analysis shows that a higher AR mRNA level is associated with improved disease outcome in patients with ER-positive/human epidermal growth factor receptor 2 (HER2)-negative tumors, but with worse disease outcome in HER2-positive subgroups. In conclusion, next to AR expression, incorporation of additional tumor characteristics will potentially make AR targeting a more valuable therapeutic strategy in breast cancer.

MicroRNAs and Androgen Receptor: Emerging Players in Breast Cancer

Breast cancer (BC) is the most common cause of cancer among women, with a high incidence rate occurrence every year worldwide despite advances in its management. BC is characterized by a spectrum of subtypes which respond differently to treatments due to their biological features, representing the main issue in the control of this type of malignancy. Androgen receptor (AR) is emerging as a target to investigate among hormone receptors, since it seems to play a role at various stages of development of specific BC subsets. For this reason, in recent years AR has become very important in the clinical practice, although its role remains controversial. A number of studies have proposed a correlation between microRNAs (miRNAs), a class of gene expression modulators, and AR in prostate cancer (PC), but there are still few evidences about the relationship between miRNAs and AR in BC. The purpose of this review is to present a state of the art scenario with consideration to the most recent discoveries about miRNAs involved in the AR associated pathogenesis of BC, in order to provide new insights into the role of miRNAs as key drivers in the modulation of AR, and possible actors in the development and progression of BC. Moreover, we consider findings about involvement of AR signaling in all stages of BC, highlighting its association with different subsets of breast carcinomas and with pre- and postmenopausal state of patients.

Androgen receptor: A promising therapeutic target in breast cancer

Breast cancer (BCa) is the second most common cancer worldwide and the most prevalent cancer in women. The majority of BCa cases are positive (+) for the estrogen receptor (ER⁺, 80%) and progesterone receptor (PR⁺, 65%). Estrogen and progesterone hormones are known to be involved in cancer progression, and thus hormonal deprivation is used as an effective treatment for ER⁺PR⁺ BCa subtypes. However, some ER⁺PR⁺ BCa patients develop resistance to such therapies. Meanwhile, chemotherapy is the only available treatment for ER^-PR^- BCa tumors. Another hormone receptor known as the androgen receptor (AR) has also been found to be widely expressed in human breast carcinomas. However, the mechanisms of AR and its endogenous androgen ligands is not well-understood in BCa and its biological role in this hormone-related disease remains unclear. In this review, we aim to address the importance of the AR in BCa diagnosis and prognosis, current AR-targeting approaches in BCa, and the potential for AR-downstream molecules to serve as therapeutic targets.

Androgen excess in breast cancer development: implications for prevention and treatment

The aim of this review is to highlight the pivotal role of androgen excess in the development of breast cancer. Available evidence suggests that testosterone controls breast epithelial growth through a balanced interaction between its two active metabolites: cell proliferation is promoted by estradiol while it is inhibited by dihydrotestosterone. A chronic overproduction of testosterone (e.g. ovarian stromal hyperplasia) results in an increased estrogen production and cell proliferation that are no longer counterbalanced by dihydrotestosterone. This shift in the androgen/estrogen balance partakes in the genesis of ER-positive tumors. The mammary gland is a modified apocrine gland, a fact rarely considered in breast carcinogenesis. When stimulated by androgens, apocrine cells synthesize epidermal growth factor (EGF) that triggers the ErbB family receptors. These include the EGF receptor and the human epithelial growth factor 2, both well known for stimulating cellular proliferation. As a result, an excessive production of androgens is capable of directly stimulating growth in apocrine and apocrine-like tumors, a subset of ER-negative/AR-positive tumors. The key role of androgen excess in the genesis of different subtypes of breast cancer has significant clinical implications for both treatment and prevention. Our belief stems from a thorough analysis of the literature, where an abundance of evidence is present to justify a clinical trial that would investigate the effectiveness of treating the underlying excessive androgen production.

Apocrine lesions of the breast: part 2 of a two-part review. Invasive apocrine carcinoma, the molecular apocrine signature and utility of immunohistochemistry in the diagnosis of apocrine lesions of the breast

Pure apocrine carcinoma of the breast is rare and has been defined by using a combination of morphologic (apocrine morphology in >90% of tumour cells) and immunohistochemical criteria (oestrogen receptor (ER) and progesterone receptor (PR) negative and androgen receptor (AR) positive). Recent advances in the molecular classification of breast tumours have uncovered a subset of breast tumours associated with high expression of androgen receptor mRNA including the so-called 'luminal androgen receptor (LAR) tumours' and 'molecular apocrine tumours' (MATs). Recognition of these tumour subsets has opened potential avenues for therapies exploiting the AR pathway in triple negative breast carcinoma (TNBC). In this second part of our two-part review, we focus on the definition of pure apocrine carcinoma, recent advances in understanding the molecular apocrine signature in breast carcinoma, its relationship to pure apocrine carcinoma defined at the level of light microscopy and immunohistochemistry (IHC) and the therapeutic implications of androgen expression in TNBC. We complete the article with a summary of the utility of IHC in stratifying apocrine lesions of the breast.

Prolactin-induced protein (PIP)-characterization and role in breast cancer progression

Prolactin-induced protein (PIP) is a small secreted glycoprotein carrying several N-linked carbohydrate chains. The expression of PIP is generally restricted to cells with apocrine properties. It was found in apocrine glands of the axilla, vulva, eyelid, ear canal, and seminal vesicle. Being a secretory protein, PIP is present in seminal plasma, saliva, lacrimal fluid, tears, sweat gland secretion. Little is known about the biological role of PIP. It binds to numerous proteins, however, in most cases the biological role of such interactions is poorly understood. A notable exception is its binding to CD4 receptors present on the surface of T lymphocytes, macrophages, and spermatozoa. The available data suggest that PIP can have immunomodulatory functions and plays an important role in cell-mediate adoptive immunity. PIP binds to bacteria from several genera, which suggests that this glycoprotein may participate also in innate immunity and protection of hosts against microbial infections. Increased levels of PIP were found in several types of human cancer (prostate, sweat and salivary gland cancers). It is especially common in breast cancer, however, data on the expression of PIP in normal and cancerous breast cancer tissues are to some degree conflicting. In early studies, it was shown that PIP is absent or its expression is very low in normal breast epithelium, whereas in breast cancers PIP is frequently expressed and present in large amounts. On the other hand, later study showed that expression of PIP is lower in advanced apocrine carcinomas and invasive carcinomas than in, respectively, in situ carcinomas and adjacent normal tissue. The most recent study revealed that PIP gene expression decreased gradually along with higher stage and grade of breast cancer. In agreement with these data, it was shown that that low levels or the lack of PIP expression are associated with a worse response of breast cancer cells to chemotherapy. It was proposed that PIP plays important role in the development and progression of breast cancer. However, its role in these processes is both unclear and controversial. In this review, the role of PIP in both physiological processes and carcinogenesis is discussed.

Genetic Markers in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) accounts for 15% to 20% of breast cancer cases and is characterized by the absence of estrogen, progesterone, and human epidermal growth factor 2 receptors. Though TNBC is a highly heterogenic and aggressive disease, TNBC patients have better response to neoadjuvant therapy compared to other breast cancer subtypes. Nevertheless, patients with residual disease have a very poor prognosis, with higher probability of relapse and lower overall survival in the first years after diagnosis. TNBC has 6 subtypes with distinct molecular signatures with different prognoses and probably different responses to therapy. The precise stratification of TNBC is therefore crucial for the development of potent standardized and targeted therapies. In spite of intensive research into finding new molecular biomarkers and designing personalized therapeutic approaches, BRCA mutational status is the only clinically validated biomarker for personalized therapy in TNBC. Recent studies have reported several promising biomarkers that are currently being validated through clinical trials. The objective of this review was to summarize the clinically relevant genetic markers for TNBC that could serve as diagnostic, prognostic, or predictive or could improve personalized therapeutic strategies.

Androgen receptor in triple negative breast cancer: A potential target for the targetless subtype

Triple negative breast cancer (TNBC) represents the 15-20% of all breast cancers (BC) and is characterized by a very aggressive behavior. Recent data suggest that TNBC is not a single disease, but it is rather an umbrella for different ontology-profiles such as basal like 1 and 2, mesenchymal, and the luminal androgen receptor (LAR). The LAR subtype is characterized by the expression of the Androgen Receptor (AR) and its downstream effects. Notwithstanding the role of the AR in several signaling pathways, its impact on a biological and clinical standpoint is still controversial. The LAR subtype has been associated with better prognosis, less chemotherapy responsiveness and lower pathologic complete response after neoadjuvant treatment. Clinical evidence suggests a role for anti-androgen therapies such as bicalutamide, enzalutamide and abiraterone, offering an interesting chemo-free alternative for chemo-unresponsive patients, and therefore potentially shifting current treatment strategies.

Androgen receptor and heat shock protein 27 co-regulate the malignant potential of molecular apocrine breast cancer

Background

The most striking feature of molecular apocrine breast cancer (MABC) is the expression of androgen receptor (AR). We report here the mechanism of the AR in regulating the behavior of MABC.

Methods

The MABC cell line, MDA-MB-453, and the nonMABC cell line, MCF7, were used in this study. The effect of dihydrotestosterone (DHT) and heat shock protein 27 (HSP27) on cell proliferation was quantified using the cell counter kit-8 (CCK8) and clonogenic assays in vitro and by a xenograft tumor model in vivo. The expression of the AR and HSP27 was analyzed using western blot, qPCR, and immunofluorescence assays. Complexes of the AR and HSP27 were detected by co-immunoprecipitation (Co-IP).

Results

In MDA-MB-453 cells, DHT promoted cell proliferation and stimulated AR and HSP27 translocation from the cytoplasm to the nucleus, whereas, it inhibited MCF7 cell growth, and only the AR translocated into the nucleus. HSP27 knock-down decreased the proliferative ability of MDA-MB-453 cells, which could be rescued by DHT, while HSP27 and DHT had synergistic effects on MCF7 cells. HSP27 phosphorylation was a prerequisite for AR translocation into the nucleus, especially phosphorylation on serine 82. In addition, DHT stimulated the tumorigenic and metastatic capacities of MDA-MB-453 cells, while HSP27 knock-down decreased the rate of tumor formation and induced apoptosis in cells.

Conclusions

The results suggest that HSP27 assists the AR in regulating the malignant behavior of MABC, and these findings might be helpful in the treatment of MABC.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0762-y) contains supplementary material, which is available to authorized users.

Androgen receptor in advanced breast cancer: is it useful to predict the efficacy of anti-estrogen therapy?

Background

Androgen receptor (AR) is widely expressed in breast cancer (BC) but its role in estrogen receptor (ER)-positive tumors is still controversial. The AR/ER ratio has been reported to impact prognosis and response to antiestrogen endocrine therapy (ET).

Methods

We assessed whether AR in primary tumors and/or matched metastases is a predictor of efficacy of first-line ET in advanced BC. Patients who had received first-line ET (2002–2011) were recruited, while those given concomitant chemotherapy or trastuzumab or pretreated with > 2 lines of chemotherapy were excluded. ER, progesterone receptor (PgR), Ki67 and AR expression were assessed by immunohistochemistry, and HER2 mainly by fluorescent in-situ hybridization. Cut-offs of 1 and 10% immunostained cells were used to categorize AR expression.

Results

Among 102 evaluable patients, biomarkers were assessed in primary tumors in 70 cases and in metastases in 49, with 17 patients having both determinations. The overall concordance rate between primary tumors and metastases was 64.7% (95% CI 42%-87.4%) for AR status. AR status did not affect TTP significantly, whereas PgR and Ki67 status did. AR/PgR ≥0.96 was associated with a significantly shorter TTP (HR = 1.65, 95% CI 1.05-2.61, p = 0.028). AR status in primary tumors or metastases was not associated with progressive disease (PD) as best response. In contrast, Ki67 ≥ 20% and PgR < 10% showed a statistically significant association with PD as best response.

Conclusions

AR expression does not appear to be useful to predict the efficacy of ET in advanced BC, whereas Ki67 and PgR exert a greater impact on its efficacy.

Lin28A activates androgen receptor via regulation of c-myc and promotes malignancy of ER-/Her2+ breast cancer

Having previously demonstrated the co-expression status of the Lin28A and androgen receptor (AR) in ER−/Her2+ breast cancer, we tested the hypothesis that Lin28A can activate AR and promotes growth of ER−/Her2+ breast cancer. The expression of Lin28A and AR were examined after Lin28A siRNA and Lin28A plasmid were transfected into ER−/Her2+ breast cancer cells. Chromatin immune-precipitation (ChIP) analysis and Luciferase Assays were used to evaluate the effect of Lin28A and c-myc on AR promoter activity. MTT assays, Boyden chamber invasion assays, colony formation assays and flow cytometry analysis were performed. ER−/Her2+ breast cancer cells which transfected with Lin28A siRNAs and Lin28A plasmid were injected into nude mice, and tumorigenesis was monitored. Our data showed that Lin28A can induced AR expression in ER−/Her2+ breast cancer cells. ChIP analysis showed that Lin28A stimulates the recruitment of c-Myc to the promoter of the AR gene. Lin28A enhanced growth ability, colonies ability, cells proliferation activities, invasive ability and inhibited cells apoptosis of ER−/Her2+ breast cancer cells. Lin28A high expression cells exhibited significantly higher tumorigenic ability in vivo. Our study demonstrates that Lin28A can activates androgen receptor via regulation of c-myc and promotes malignancy of ER−/Her2+ breast cancer. Our findings underline a novel role for Lin28A in breast cancer development and activation of the AR axis.