Clinical Implications of Androgen-Positive Triple-Negative Breast Cancer

Differentiating Primary and Recurrent Lesions in Patients with a History of Breast Cancer: A Comprehensive Review

Breast cancer (BC) recurrence remains a concerning issue, requiring accurate identification and differentiation from primary lesions for optimal patient management. This comprehensive review aims to summarize and evaluate the current evidence on methods to distinguish primary breast tumors from recurrent lesions in patients with a history of BC. Also, we provide a comprehensive understanding of the different imaging techniques, including mammography, ultrasound, magnetic resonance imaging, and positron emission tomography, highlighting their diagnostic accuracy, limitations, and potential integration. In addition, the role of various biopsy modalities and molecular markers was explored. Furthermore, the potential role of liquid biopsy, circulating tumor cells, and circulating tumor DNA in differentiating between primary and recurrent BC was emphasized. Finally, it addresses emerging diagnostic modalities, such as radiomic analysis and artificial intelligence, which show promising potential in enhancing diagnostic accuracy. Through comprehensive analysis and review of the available literature, the current study provides an up-to-date understanding of the current state of knowledge, challenges, and future directions in accurately distinguishing between primary and recurrent breast lesions in patients with a history of BC.

Targeting AR-positive breast cancer cells via drug repurposing approach

Androgen Receptor (AR) is overexpressed in almost all the molecular subtypes of breast cancer. Besides aiding the tumorigenic environment of cancer by abnormal cell proliferation, AR also takes part in promoting cancer signaling pathways, thereby promoting aggressiveness. In this study, AR was selected as the target protein in breast cancer cells. Following this, a library of 1293 FDA-approved drugs was screened via molecular docking, MD simulation, and MMPBSA binding energy. Amongst the library of compounds, Adapalene exhibited the least binding energy of (-10.2 kCal/mol) in comparison to that of the chosen reference compound, Nilutamide (-8.6 kCal/mol). Furthermore, the in vitro efficacy of Adapalene was also determined in two different breast cancer cell lines such as MCF7 (AR-positive/ER-positive) and MDA-MB-231 (AR negative/TNBC). Initially, the cell viability assay (MTT) was performed, which endowed us with a lesser IC50 value of Adapalene in comparison to Nilutamide in both cell lines. The IC50 of Adapalene was found to be 12 μM and 39.4 μM in MCF7 and MDA-MB-231 cells, respectively. Furthermore, Adapalene also induced cellular ROS and apoptosis by 3.5-fold and 26.58% in MCF7 cells. However, the overall effect of Adapalene was significantly lower in the case of MDA-MB-231 cell lines, which could be attributed to its inherent nature of the absence of hormone receptors. Conclusively, Adapalene possesses greater therapeutic efficacy in comparison to the control drug, thereby hinting towards the potential use of Adapalene in the treatment of AR-positive breast cancer.

Androgen and Estrogen β Receptor Expression Enhances Efficacy of Antihormonal Treatments in Triple-Negative Breast Cancer Cell Lines

The triple-negative breast cancer (TNBC) subtype is characterized by the lack of expression of ERα (estrogen receptor α), PR (progesterone receptor) and no overexpression of HER-2. However, TNBC can express the androgen receptor (AR) or estrogen receptor β (ERβ). Also, TNBC secretes steroid hormones and is influenced by hormonal fluctuations, so the steroid inhibition could exert a beneficial effect in TNBC treatment. The aim of this study was to evaluate the effect of dutasteride, anastrozole and ASP9521 in in vitro processes using human TNBC cell lines. For this, immunofluorescence, sensitivity, proliferation and wound healing assays were performed, and hormone concentrations were studied. Results revealed that all TNBC cell lines expressed AR and ERβ; the ones that expressed them most intensely were more sensitive to antihormonal treatments. All treatments reduced cell viability, highlighting MDA-MB-453 and SUM-159. Indeed, a decrease in androgen levels was observed in these cell lines, which could relate to a reduction in cell viability. In addition, MCF-7 and SUM-159 increased cell migration under treatments, increasing estrogen levels, which could favor cell migration. Thus, antihormonal treatments could be beneficial for TNBC therapies. This study clarifies the importance of steroid hormones in AR and ERβ-positive cell lines of TNBC.

Molecular Characteristics and Therapeutic Vulnerabilities of Claudin-low Breast Cancers Derived from Cell Line Models

BACKGROUND/AIM

Breast cancers constitute heterogeneous tumor groups and their categorization in subtypes based on the expression of the estrogen (ER), progesterone (PR) and HER2 receptors has advanced therapeutics. Claudin-low breast cancer has been proposed as an additional subtype which is mostly ER, PR and HER2 negative, but its identification has not led to corresponding specific treatments yet.

MATERIALS AND METHODS

Breast cancer cell lines from the Cancer Cell Line Encyclopedia (CCLE) were assessed for mRNA suppression of claudins and mRNA expression of ER and ERBB2 (the gene encoding HER2). The set of identified claudin-low cell lines were compared with representative ER-/ERBB2- cell lines for associated molecular alterations, gene dependencies through CRISPR and microRNA arrays and in vitro drug sensitivities using the Genomics of Drug Sensitivity in Cancer (GDSC) project.

RESULTS

Claudin-low cell lines display up-regulation of mRNA expression of epithelial to mesenchymal transition (EMT) regulators. Methylation sensitive genes are down-regulated in claudin-low lines compared with other cell lines, without associated up-regulation of DNA methyltransferases. Dependency screen microarrays reveal dependencies of claudin-low cell lines on components of the cytoskeleton but no consistent dependencies in known oncogenes or tumor suppressors. Potential drug sensitivities revealed in the drug screens included sensitivities to WNT pathway modulators, tyrosine kinase cascade inhibitors and BET inhibitors. On the other hand, claudin-low cell lines showed resistance to deacetylase inhibitors.

CONCLUSION

Claudin-low cell line models duplicate features of claudin-low breast cancers and may serve as guides for identification of drugs worth exploring for further development.

Measurement of malignant spiculated mass lesions on mammogram: Do we include the length of the spicules?

AIM

The aim of this study is to determine if the core size or size with spicules has a better correlation with the final histologic size of spiculated mass lesions.

METHODS

A retrospective study of 48-month duration from January 2014 to December 2017 of biopsy-proven invasive ductal carcinoma presenting as spiculated mass lesions on mammogram was conducted.

RESULTS

There were 195 patients in the study. The mean of the core size was 16.6 mm; when spicules were included the mean size was 27.4mm and final histologic size 21.1 mm. Using unpaired Student 't' test difference in the means was statistically significant (p<0.0001). Pearson number (R) core size versus final histologic size was 0.535 (P < 0.001) and for size with spicules versus final histologic size was 0.495 (P < 0.001).

CONCLUSION

Our study demonstrated that the core size has a stronger positive correlation to final histologic size and should be used preoperatively in decision-making about surgery.

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.

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.

Molecular Classification, Treatment, and Genetic Biomarkers in Triple-Negative Breast Cancer: A Review

Breast cancer is the most common malignancy and the second most common cause of cancer-related mortality in women. Triple-negative breast cancers do not express estrogen receptors, progesterone receptors, or human epidermal growth factor receptor 2 and have a higher recurrence rate, greater metastatic potential, and lower overall survival rate than those of other breast cancers. Treatment of triple-negative breast cancer is challenging; molecular-targeted therapies are largely ineffective and there is no standard treatment. In this review, we evaluate current attempts to classify triple-negative breast cancers based on their molecular features. We also describe promising treatment methods with different advantages and discuss genetic biomarkers and other prediction tools. Accurate molecular classification of triple-negative breast cancers is critical for patient risk categorization, treatment decisions, and surveillance. This review offers new ideas for more effective treatment of triple-negative breast cancer and identifies novel targets for drug development.

Anti-Androgenic Therapies Targeting the Luminal Androgen Receptor of a Typical Triple-Negative Breast Cancer

Triple-negative tumors are progressively delineating their existence over the extended spectrum of breast cancers, marked by intricate molecular heterogeneity, a low overall survival rate, and an unexplored therapeutic approach. Although the basal subtype transcends the group and contributes approximately 80% to triple-negative breast cancer (TNBC) cases, the exceptionally appearing mesenchymal and luminal androgen receptor (LAR) subtypes portray an unfathomable clinical course. LAR with a distinct generic profile frequently metastasizes to regional lymph nodes and bones. This subtype is minimally affected by chemotherapy and shows the lowest pathologic complete response. The androgen receptor is the only sex steroid receptor that plays a cardinal role in the progression of breast cancers and is typically overexpressed in LAR. The partial AR antagonist bicalutamide and the next-generation AR inhibitor enzalutamide are being assessed in standard protocols for the mitigation of TNBC. There arises an inevitable need to probe into the strategies that could neutralize these androgen receptors and alleviate the trajectory of concerning cancer. This paper thus focuses on reviewing literature that provides insights into the anti-androgenic elements against LAR typical TNBC that could pave the way for clinical advancements in this dynamic sphere of oncology.

Identification of a minimum number of genes to predict triple-negative breast cancer subgroups from gene expression profiles

BACKGROUND

Triple-negative breast cancer (TNBC) is a very heterogeneous disease. Several gene expression and mutation profiling approaches were used to classify it, and all converged to the identification of distinct molecular subtypes, with some overlapping across different approaches. However, a standardised tool to routinely classify TNBC in the clinics and guide personalised treatment is lacking. We aimed at defining a specific gene signature for each of the six TNBC subtypes proposed by Lehman et al. in 2011 (basal-like 1 (BL1); basal-like 2 (BL2); mesenchymal (M); immunomodulatory (IM); mesenchymal stem-like (MSL); and luminal androgen receptor (LAR)), to be able to accurately predict them.

METHODS

Lehman's TNBCtype subtyping tool was applied to RNA-sequencing data from 482 TNBC (GSE164458), and a minimal subtype-specific gene signature was defined by combining two class comparison techniques with seven attribute selection methods. Several machine learning algorithms for subtype prediction were used, and the best classifier was applied on microarray data from 72 Italian TNBC and on the TNBC subset of the BRCA-TCGA data set.

RESULTS

We identified two signatures with the 120 and 81 top up- and downregulated genes that define the six TNBC subtypes, with prediction accuracy ranging from 88.6 to 89.4%, and even improving after removal of the least important genes. Network analysis was used to identify highly interconnected genes within each subgroup. Two druggable matrix metalloproteinases were found in the BL1 and BL2 subsets, and several druggable targets were complementary to androgen receptor or aromatase in the LAR subset. Several secondary drug-target interactions were found among the upregulated genes in the M, IM and MSL subsets.

CONCLUSIONS

Our study took full advantage of available TNBC data sets to stratify samples and genes into distinct subtypes, according to gene expression profiles. The development of a data mining approach to acquire a large amount of information from several data sets has allowed us to identify a well-determined minimal number of genes that may help in the recognition of TNBC subtypes. These genes, most of which have been previously found to be associated with breast cancer, have the potential to become novel diagnostic markers and/or therapeutic targets for specific TNBC subsets.

AR Expression Correlates with Distinctive Clinicopathological and Genomic Features in Breast Cancer Regardless of ESR1 Expression Status

Androgen receptor (AR) expression is frequently observed in breast cancer, but its association with estrogen receptor (ER) expression in breast cancer remains unclear. This study analyzed the clinicopathological and molecular features associated with AR negativity in both ER-positive and ER-negative breast cancer, trying to elucidate the molecular correlation between AR and ER. Our results showed that AR negativity was associated with different clinicopathological characteristics and molecular features in ER-positive and ER-negative breast cancer. Moreover, AR-positive breast cancer has better clinicopathological features than AR-negative breast cancer, especially in the ER-negative subtype. These results suggest that the role of AR in ER-negative breast cancer is distinctive from that in ER-positive breast cancer.

CXCL14 Attenuates Triple-Negative Breast Cancer Progression by Regulating Immune Profiles of the Tumor Microenvironment in a T Cell-Dependent Manner

Triple-negative breast cancer (TNBC) is aggressive and has a poor overall survival due to a lack of therapeutic targets compared to other subtypes. Chemokine signature revealed that TNBC had low levels of CXCL14, an orphan homeostatic chemokine to regulate the immune network. Here, we investigated if CXCL14 plays a critical role in TNBC progression, focusing on survival rates, tumor growth and metastasis, and immune profiles in the tumor microenvironment. Analysis of human breast-cancer datasets showed that low CXCL14 expression levels were associated with poor survival rates in patients with breast cancer, particularly for TNBC subtypes. Overexpression of CXCL14 in TNBC 4T1 orthotopic mouse model significantly reduced tumor weights and inhibited lung metastasis. Furthermore, the CXCL14 overexpression altered immune profiles in the tumor microenvironment as follows: decreased F4/80+ macrophages and CD4+CD25+ Treg cells, and increased CD8+T cells in primary tumors; decreased Ly6C+ myeloid cells and CD4+CD25+ Treg cells and increased CD4+ and CD8+T cells in lung metastatic tumors. CXCL14-induced reduction of tumor growth and metastasis was diminished in T cell-deficient nude mice. Taken together, our data demonstrate that CXCL14 inhibits TNBC progression through altering immune profiles in the tumor microenvironment and it is mediated in a T cell-dependent manner. Thus, CXCL14 could be used as a biomarker for prognosis.

Adaptation to Hypoxia May Promote Therapeutic Resistance to Androgen Receptor Inhibition in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) surpasses other BC subtypes as the most challenging to treat due to its lack of traditional BC biomarkers. Nearly 30% of TNBC patients express the androgen receptor (AR), and the blockade of androgen production and AR signaling have been the cornerstones of therapies for AR-positive TNBC. However, the majority of women are resistant to AR-targeted therapy, which is a major impediment to improving outcomes for the AR-positive TNBC subpopulation. The hypoxia signaling cascade is frequently activated in the tumor microenvironment in response to low oxygen levels; activation of the hypoxia signaling cascade allows tumors to survive despite hypoxia-mediated interference with cellular metabolism. The activation of hypoxia signaling networks in TNBC promotes resistance to most anticancer drugs including AR inhibitors. The activation of hypoxia network signaling occurs more frequently in TNBC compared to other BC subtypes. Herein, we examine the (1) interplay between hypoxia signaling networks and AR and (2) whether hypoxia and hypoxic stress adaptive pathways promote the emergence of resistance to therapies that target AR. We also pose the well-supported question, “Can the efficacy of androgen-/AR-targeted treatments be enhanced by co-targeting hypoxia?” By critically examining the evidence and the complex entwinement of these two oncogenic pathways, we argue that the simultaneous targeting of androgen biosynthesis/AR signaling and hypoxia may enhance the sensitivity of AR-positive TNBCs to AR-targeted treatments, derail the emergence of therapy resistance, and improve patient outcomes.

Chimeric Oncolytic Adenovirus Armed Chemokine Rantes for Treatment of Breast Cancer

The immunosuppressive state in the tumor microenvironment (TME) of breast cancer makes it difficult to treat with immunotherapy. Oncolytic viruses not only lyse tumor cells but also reshape the TME. Therefore, they can play a multi-mechanism synergistic effect with immunotherapy. In this study, an oncolytic adenovirus Ad5F11bSP-Rantes was constructed and used as a vector to express the chemokine Rantes. The objective of this study was to test the dual mechanisms of the oncolytic effect mediated by virus replication and the enhanced anticancer immune response mediated by Rantes chemotaxis of immune cells. It was found that Ad5F11bSP-Rantes has strong infectivity and effective killing activity against breast cancer cells. In the established triple negative breast cancer (TNBC) xenograft model in NCG mice whose immune system was humanized with human peripheral blood mononuclear cells (PBMCs), Ad5F11bSP-Rantes achieved 88.33% tumor inhibition rate. Rantes expression was high in mouse blood, a large number of CD3+ lymphocytes infiltrated in tumor tissues and E-cadherin was up-regulated in cancer cells, suggesting that Ad5F11bSP-Rantes altered the TME and induced a reversal of cancer cell epithelial-mesenchymal transition (EMT). In conclusion, oncolytic adenovirus can exert the oncolytic effect and the chemotactic effect of immune cells and realize the synergy of multiple anticancer effects. This strategy creates a candidate treatment for the optimization of breast cancer, especially TNBC, combination therapy.

Luminal androgen receptor breast cancer subtype and investigation of the microenvironment and neoadjuvant chemotherapy response

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype with low overall survival rates and high molecular heterogeneity; therefore, few targeted therapies are available. The luminal androgen receptor (LAR) is the most consistently identified TNBC subtype, but the clinical utility has yet to be established. Here, we constructed a novel genomic classifier, LAR-Sig, that distinguishes the LAR subtype from other TNBC subtypes and provide evidence that it is a clinically distinct disease. A meta-analysis of seven TNBC datasets (n = 1086 samples) from neoadjuvant clinical trials demonstrated that LAR patients have significantly reduced response (pCR) rates than non-LAR TNBC patients (odds ratio = 2.11, 95% CI: 1.33, 2.89). Moreover, deconvolution of the tumor microenvironment confirmed an enrichment of luminal epithelium corresponding with a decrease in basal and myoepithelium in LAR TNBC tumors. Increased immunosuppression in LAR patients may lead to a decreased presence of cycling T-cells and plasma cells. While, an increased presence of myofibroblast-like cancer-associated cells may impede drug delivery and treatment. In summary, the lower levels of tumor infiltrating lymphocytes (TILs), reduced immune activity in the micro-environment, and lower pCR rates after NAC, suggest that new therapeutic strategies for the LAR TNBC subtype need to be developed.

Role of PI3K/Akt/mTOR pathway in mediating endocrine resistance: concept to clinic

The majority of breast cancers express the estrogen receptor (ER) and for this group of patients, endocrine therapy is the cornerstone of systemic treatment. However, drug resistance is common and a focus for breast cancer preclinical and clinical research. Over the past 2 decades, the PI3K/Akt/mTOR axis has emerged as an important driver of treatment failure, and inhibitors of mTOR and PI3K are now licensed for the treatment of women with advanced ER-positive breast cancer who have relapsed on first-line hormonal therapy. This review presents the preclinical and clinical data that led to this new treatment paradigm and discusses future directions.

Translational Implications of Dysregulated Pathways and MicroRNA Regulation in Quadruple-Negative Breast Cancer

Triple-negative breast cancers (HER2−, ER−, PR−) continue to present a unique treatment challenge and carry unfavorable prognoses. The elucidation of novel therapeutic targets has necessitated the re-evaluation of stratification approaches to best predict prognosis, treatment response and theranostic and prognostic markers. Androgen receptor expression and function have important implications on proliferation, tumor progression, immunity and molecular signaling in breast cancer. Accordingly, there has been increasing support for classification of androgen receptor-negative triple-negative breast cancer or quadruple-negative breast cancer (QNBC). QNBC has unique molecular, signaling and expression regulation profiles, particularly those affected by microRNA regulatory networks. MicroRNAs are now known to regulate AR-related targets and pathways that are dysregulated in QNBC, including immune checkpoint inhibitors (ICIs), SKP2, EN1, ACSL4 and EGFR. In this review, we explore and define the QNBC tumor subtype, its molecular and clinical distinctions from other subtypes, miRNA dysregulation and function in QNBC, and knowledge gaps in the field. Potential insights into clinical and translational implications of these dysregulated networks in QNBC are discussed.

Long non-coding RNA HEIH: a novel tumor activator in multiple cancers

The last decade has witnessed the altered expression levels of long non-coding RNA HEIH in different types of cancer. More than half of the HEIH studies in cancer have been published within the last two years. To our knowledge, this is the first review to discuss very recent developments and insights into HEIH contribution to carcinogenesis. The functional role, molecular mechanism, and clinical significance of HEIH in human cancers are described in detail. The expression of HEIH is elevated in a broad spectrum of cancers, and its disorder contributes to cell proliferation, migration, invasion, and drug resistance of cancer cells through different underlying mechanisms. In addition, the high expression of HEIH is significantly associated with advanced tumor stage, tumor size and decreased overall survival, suggesting HEIH may function as a prognostic biomarker and potential therapeutic target for human cancers.

Role of PARP in TNBC: Mechanism of Inhibition, Clinical Applications, and Resistance

Triple-negative breast cancer is a combative cancer type with a highly inflated histological grade that leads to poor theragnostic value. Gene, protein, and receptor-specific targets have shown effective clinical outcomes in patients with TNBC. Cells are frequently exposed to DNA-damaging agents. DNA damage is repaired by multiple pathways; accumulations of mutations occur due to damage to one or more pathways and lead to alterations in normal cellular mechanisms, which lead to development of tumors. Advances in target-specific cancer therapies have shown significant momentum; most treatment options cause off-target toxicity and side effects on healthy tissues. PARP (poly(ADP-ribose) polymerase) is a major protein and is involved in DNA repair pathways, base excision repair (BER) mechanisms, homologous recombination (HR), and nonhomologous end-joining (NEJ) deficiency-based repair mechanisms. DNA damage repair deficits cause an increased risk of tumor formation. Inhibitors of PARP favorably kill cancer cells in BRCA-mutations. For a few years, PARPi has shown promising activity as a chemotherapeutic agent in BRCA1- or BRCA2-associated breast cancers, and in combination with chemotherapy in triple-negative breast cancer. This review covers the current results of clinical trials testing and future directions for the field of PARP inhibitor development.

Type 1 Nuclear Receptor Activity in Breast Cancer: Translating Preclinical Insights to the Clinic

The nuclear receptor (NR) family of transcription factors is intimately associated with the development, progression and treatment of breast cancer. They are used diagnostically and prognostically, and crosstalk between nuclear receptor pathways and growth factor signalling has been demonstrated in all major subtypes of breast cancer. The majority of breast cancers are driven by estrogen receptor α (ER), and anti-estrogenic therapies remain the backbone of treatment, leading to clinically impactful improvements in patient outcomes. This serves as a blueprint for the development of therapies targeting other nuclear receptors. More recently, pivotal findings into modulating the progesterone (PR) and androgen receptors (AR), with accompanying mechanistic insights into NR crosstalk and interactions with other proliferative pathways, have led to clinical trials in all of the major breast cancer subtypes. A growing body of evidence now supports targeting other Type 1 nuclear receptors such as the glucocorticoid receptor (GR), as well as Type 2 NRs such as the vitamin D receptor (VDR). Here, we reviewed the existing preclinical insights into nuclear receptor activity in breast cancer, with a focus on Type 1 NRs. We also discussed the potential to translate these findings into improving patient outcomes.

Molecular Classification Models for Triple Negative Breast Cancer Subtype Using Machine Learning

Triple negative breast cancer (TNBC) lacks well-defined molecular targets and is highly heterogenous, making treatment challenging. Using gene expression analysis, TNBC has been classified into four different subtypes: basal-like immune-activated (BLIA), basal-like immune-suppressed (BLIS), mesenchymal (MES), and luminal androgen receptor (LAR). However, there is currently no standardized method for classifying TNBC subtypes. We attempted to define a gene signature for each subtype, and to develop a classification method based on machine learning (ML) for TNBC subtyping. In these experiments, gene expression microarray data for TNBC patients were downloaded from the Gene Expression Omnibus database. Differentially expressed genes unique to 198 known TNBC cases were identified and selected as a training gene set to train in seven different classification models. We produced a training set consisting of 719 DEGs selected from uniquely expressed genes of all four subtypes. The highest average accuracy of classification of the BLIA, BLIS, MES, and LAR subtypes was achieved by the SVM algorithm (accuracy 95–98.8%; AUC 0.99–1.00). For model validation, we used 334 samples of unknown TNBC subtypes, of which 97 (29.04%), 73 (21.86%), 39 (11.68%) and 59 (17.66%) were predicted to be BLIA, BLIS, MES, and LAR, respectively. However, 66 TNBC samples (19.76%) could not be assigned to any subtype. These samples contained only three upregulated genes (EN1, PROM1, and CCL2). Each TNBC subtype had a unique gene expression pattern, which was confirmed by identification of DEGs and pathway analysis. These results indicated that our training gene set was suitable for development of classification models, and that the SVM algorithm could classify TNBC into four unique subtypes. Accurate and consistent classification of the TNBC subtypes is essential for personalized treatment and prognosis of TNBC.