Estrogen Receptor-Positive Breast Cancer: Exploiting Signaling Pathways Implicated in Endocrine Resistance

Progression from ductal carcinoma in situ to invasive breast cancer: molecular features and clinical significance

Ductal carcinoma in situ (DCIS) represents pre-invasive breast carcinoma. In untreated cases, 25-60% DCIS progress to invasive ductal carcinoma (IDC). The challenge lies in distinguishing between non-progressive and progressive DCIS, often resulting in over- or under-treatment in many cases. With increasing screen-detected DCIS in these years, the nature of DCIS has aroused worldwide attention. A deeper understanding of the biological nature of DCIS and the molecular journey of the DCIS-IDC transition is crucial for more effective clinical management. Here, we reviewed the key signaling pathways in breast cancer that may contribute to DCIS initiation and progression. We also explored the molecular features of DCIS and IDC, shedding light on the progression of DCIS through both inherent changes within tumor cells and alterations in the tumor microenvironment. In addition, valuable research tools utilized in studying DCIS including preclinical models and newer advanced technologies such as single-cell sequencing, spatial transcriptomics and artificial intelligence, have been systematically summarized. Further, we thoroughly discussed the clinical advancements in DCIS and IDC, including prognostic biomarkers and clinical managements, with the aim of facilitating more personalized treatment strategies in the future. Research on DCIS has already yielded significant insights into breast carcinogenesis and will continue to pave the way for practical clinical applications.

A NAD(P)H oxidase mimic for catalytic tumor therapy via a deacetylase SIRT7-mediated AKT/GSK3β pathway

Nicotinamide adenine dinucleotide (NADH) and its phosphorylated form, NADPH, are essential cofactors that play critical roles in cell functions, influencing antioxidation, reductive biosynthesis, and cellular pathways involved in tumor cell apoptosis and tumorigenesis. However, the use of nanomaterials to consume NAD(P)H and thus bring an impact on signaling pathways in cancer treatment remains understudied. In this study, we employed a salt template method to synthesize a carbon-coated-cobalt composite (C@Co) nanozyme, which exhibited excellent NAD(P)H oxidase (NOX)-like activity and mimicked the reaction mechanism of natural NOX. The C@Co nanozyme efficiently consumed NAD(P)H within cancer cells, leading to increased production of reactive oxygen species (ROS) and a reduction in mitochondrial membrane potential. Meanwhile, the generation of the biologically active cofactor NAD(P)+ promoted the expression of the deacetylase SIRT7, which in turn inhibited the serine/threonine kinase AKT signaling pathway, ultimately promoting apoptosis. This work sheds light on the influence of nanozymes with NOX-like activity on cellular signaling pathways in tumor therapy and demonstrates their promising antitumor effects in a tumor xenograft mouse model. These findings contribute to a better understanding of NAD(P)H manipulation in cancer treatment and suggest the potential of nanozymes as a therapeutic strategy for cancer therapy.

Synergy between PEDF and Doxorubicin in Breast Cancer Cells: Effects on Metastatic and Metabolic Pathways

Pigment epithelium-derived factor (PEDF), a serine protease inhibitor (Serpin) family member, shows promise in inhibiting tumour growth. In our study, we explored the effects of PEDF on the efficacy of the frontline chemotherapy agent doxorubicin (Dox) in BC cells. We found that Dox+PEDF treatment significantly reduced glucose uptake in MDA-MB-231 cells compared to the control (p = 0.0005), PEDF (p = 0.0137), and Dox (p = 0.0171) alone but paradoxically increased it in MCF-7 cells. Our findings further revealed that PEDF, Dox, and Dox+PEDF substantially hindered tumour cell migration from tumour spheroids, with Dox+PEDF showing the most significant impact (p < 0.0001). We also observed notable decreases in the expression of metastatic markers (uPAR, uPA, CXCR4, MT1-MMP, TNF-α) across all treatment groups (p < 0.0001) in both cell lines. When it comes to metabolic pathways, PEDF increased phosphorylated IRS-1 (p-IRS1) levels in MDA-MB-231 and MCF-7 (p < 0.0001), while Dox decreased it, and the combination led to an increase. In MDA-MB-231 cells, treatment with PEDF, Dox, and the combination led to a notable decrease in both phosphorylated AKT (p-AKT) and total AKT levels. In MCF-7, while PEDF, Dox, and their combination led to a reduction in p-AKT, total levels of AKT increased in the presence of Dox and Dox+PEDF. Combining PEDF with Dox enhances the targeting of metastatic and metabolic pathways in breast cancer cell lines. This synergy, marked by PEDF's increasing roles in cancer control, may pave the way for more effective cancer treatments.

Therapeutic evolution in HR+/HER2- breast cancer: from targeted therapy to endocrine therapy

Breast cancer, a complex and varied disease, has four distinct subtypes based on estrogen receptor and human epidermal growth factor receptor 2 (HER2) levels, among which a significant subtype known as HR+/HER2-breast cancer that has spurred numerous research. The prevalence of breast cancer and breast cancer-related death are the most serious threats to women's health worldwide. Current progress in treatment strategies for HR+/HER2-breast cancer encompasses targeted therapy, endocrine therapy, genomic immunotherapy, and supplementing traditional methods like surgical resection and radiotherapy. This review article summarizes the current epidemiology of HR+/HER2-breast cancer, introduces the classification of HR+/HER2-breast cancer and the commonly used treatment methods. The mechanisms of action of various drugs, including targeted therapy drugs and endocrine hormone therapy drugs, and their potential synergistic effects are deeply discussed. In addition, clinical trials of these drugs that have been completed or are still in progress are included.

Research progress of exosomes in drug resistance of breast cancer

Since breast cancer is a heterogeneous disease, there are currently a variety of treatment methods available, including chemotherapy, endocrine therapy, molecular targeted therapy, immunotherapy, radiation therapy, etc. Breast cancer recurrence and metastasis, despite many treatment modalities, constitute a considerable threat to patients' survival time and pose a clinical challenge that is difficult to tackle precisely. Exosomes have a very special and crucial role in the treatment of drug resistance in breast cancer as a carrier of intercellular communication in the tumor microenvironment. Exosomes and breast cancer treatment resistance have been linked in a growing number of clinical investigations in recent years. This paper covers the status of research on exosomes in the treatment of breast cancer drug resistance and offers theoretical guidance for investigating new strategies to treat breast cancer drug resistance.

The promise of combining CDK4/6 inhibition with hormonal therapy in the first-line treatment setting for metastatic or recurrent endometrial adenocarcinoma

Metastatic or recurrent endometrioid adenocarcinoma of the uterine corpus is often incurable with limited treatment options. First-line treatment often includes cytotoxic chemotherapy, which incurs significant toxicities for many patients. Endometrial cancer, specifically endometrioid cancer, is a hormone-sensitive disease and, while single-agent hormonal therapies have demonstrated clinical benefit, resistance to these agents often leads to the use of chemotherapy. There is a lack of approved endocrine treatment options in the metastatic setting for most recurrent endometrial cancers, representing an unmet clinical need. Emerging evidence suggests that hormonal therapy in combination with other targeted treatments, such as cyclin dependent kinase (CDK)4/6 inhibitors, is well tolerated and effective in select patient populations. We discuss the clinical evidence suggesting that the combination of CDK4/6 inhibitors and hormonal therapy has the potential to represent an important addition to the first-line treatment options for patients with low-grade advanced or recurrent endometrial cancer.

Metastatic ER+ Breast Cancer: Mechanisms of Resistance and Future Therapeutic Approaches

Endocrine therapy is the main treatment for hormone receptor-positive (HR+) breast cancer. However, advanced tumors develop resistance to endocrine therapy, rendering it ineffective as the disease progresses. There are several molecular mechanisms of primary and secondary endocrine resistance. Resistance can develop due to either alteration of the estrogen receptor pathway (e.g., ESR1 mutations) or upstream growth factors signaling pathways (e.g., PI3K/Akt/mTOR pathway). Despite progress in the development of molecularly targeted anticancer therapies, the emergence of resistance remains a major limitation and an area of unmet need. In this article, we review the mechanisms of acquired endocrine resistance in HR+ advanced breast cancer and discuss current and future investigational therapeutic approaches.

Tailoring Potential Natural Compounds for the Treatment of Luminal Breast Cancer

Breast cancer (BC) is the most diagnosed cancer worldwide, mainly affecting the epithelial cells from the mammary glands. When it expresses the estrogen receptor (ER), the tumor is called luminal BC, which is eligible for endocrine therapy with hormone signaling blockade. Hormone therapy is essential for the survival of patients, but therapeutic resistance has been shown to be worrying, significantly compromising the prognosis. In this context, the need to explore new compounds emerges, especially compounds of plant origin, since they are biologically active and particularly promising. Natural products are being continuously screened for treating cancer due to their chemical diversity, reduced toxicity, lower side effects, and low price. This review summarizes natural compounds for the treatment of luminal BC, emphasizing the activities of these compounds in ER-positive cells. Moreover, their potential as an alternative to endocrine resistance is explored, opening new opportunities for the design of optimized therapies.

The role of the tumor microenvironment in endocrine therapy resistance in hormone receptor-positive breast cancer

Endocrine therapy is the prominent strategy for the treatment of hormone-positive breast cancers. The emergence of resistance to endocrine therapy is a major health concern among hormone-positive breast cancer patients. Resistance to endocrine therapy demands the design of newer therapeutic strategies. The understanding of underlying molecular mechanisms of endocrine resistance, components of the tumor microenvironment (TME), and interaction of resistant breast cancer cells with the cellular/acellular components of the intratumoral environment are essential to formulate new therapeutic strategies for the treatment of endocrine therapy-resistant breast cancers. In the first half of the article, we have discussed the general mechanisms (including mutations in estrogen receptor gene, reregulated activation of signaling pathways, epigenetic changes, and cell cycle alteration) responsible for endocrine therapy resistance in hormone-positive breast cancers. In the latter half, we have emphasized the precise role of cellular (cancer-associated fibroblasts, immune cells, and cancer stem cells) and acellular components (collagen, fibronectin, and laminin) of TME in the development of endocrine resistance in hormone-positive breast cancers. In sum, the article provides an overview of the relationship between endocrine resistance and TME in hormone-positive breast cancers.

Integrative analysis of mRNA and miRNA expression profiles and somatic variants in oxysterol signaling in early-stage luminal breast cancer

Oxysterols, oxidized derivatives of cholesterol, act in breast cancer (BC) as selective estrogen receptor modulators and affect cholesterol homeostasis, drug transport, nuclear and cell receptors, and other signaling proteins. Using data from three highly overlapping sets of patients (N = 162 in total) with early-stage estrogen-receptor-positive luminal BC-high-coverage targeted DNA sequencing (113 genes), mRNA sequencing, and full micro-RNA (miRNA) transcriptome microarrays-we describe complex oxysterol-related interaction (correlation) networks, with validation in public datasets (n = 538) and 11 databases. The ESR1-CH25H-INSIG1-ABCA9 axis was the most prominent, interconnected through miR-125b-5p, miR-99a-5p, miR-100-5p, miR-143-3p, miR-199b-5p, miR-376a-3p, and miR-376c-3p. Mutations in SC5D, CYP46A1, and its functionally linked gene set were associated with multiple differentially expressed oxysterol-related genes. STARD5 was upregulated in patients with positive lymph node status. High expression of hsa-miR-19b-3p was weakly associated with poor survival. This is the first study of oxysterol-related genes in BC that combines DNA, mRNA, and miRNA multiomics with detailed clinical data. Future studies should provide links between intratumoral oxysterol signaling depicted here, circulating oxysterol levels, and therapy outcomes, enabling eventual clinical exploitation of present findings.

ESR1 fusion proteins invoke breast cancer subtype-dependent enrichment of ligand independent pro-oncogenic signatures and phenotypes

Breast cancer is a leading cause of female mortality and despite advancements in diagnostics and personalized therapeutics, metastatic disease largely remains incurable due to drug resistance. Fortunately, identification of mechanisms of therapeutic resistance have rapidly transformed our understanding of cancer evasion and is enabling targeted treatment regimens. When the druggable estrogen receptor (ER, ESR1 ), expressed in two-thirds of all breast cancer, is exposed to endocrine therapy, there is risk of somatic mutation development in approximately 30% of cases and subsequent treatment resistance. A more recently discovered mechanism of ER mediated endocrine resistance is the expression of ER fusion proteins. ER fusions, which retain the protein's DNA binding domain, harbor ESR1 exons 1-6 fused to an in-frame gene partner resulting in loss of the 3' ER ligand binding domain (LBD). In this report we demonstrate that in no-special type (NST) and invasive lobular carcinoma (ILC) cell line models, ER fusion proteins exhibit robust hyperactivation of canonical ER signaling pathways independent of the ligand estradiol or anti-endocrine therapies such as Fulvestrant and Tamoxifen. We employ cell line models stably overexpressing ER fusion proteins with concurrent endogenous ER knockdown to minimize the influence of endogenous wildtype ER. Cell lines exhibited shared transcriptomic enrichment in pathways known to be drivers of metastatic disease, notably the MYC pathway. The heterogeneous 3' fusion partners, particularly transcription factors SOX9 and YAP1 , evoked varying degrees of transcriptomic and cistromic activity that translated into unique phenotypic readouts. Herein we report that cell line activity is subtype-, fusion-, and assay-specific suggesting that the loss of the LBD, the 3' fusion partner, and the cellular landscape all influence fusion activity. Therefore, it will be critical to generate additional data on frequency of the ER fusions, in the context of the clinicopathological features of the tumor.

Significance

ER fusion proteins exhibit diverse mechanisms of endocrine resistance in breast cancer cell lines representing the no special type (NST) and invasive lobular cancer (ILC) subtypes. Our emphasize upon both the shared and unique cellular adaptations imparted by ER fusions offers the foundation for further translational research and clinical decision making.

Coencapsulation of Gemcitabine and Thymoquinone in Citrem-Phosphatidylcholine Hexosome Nanocarriers Improves In Vitro Cellular Uptake in Breast Cancer Cells

Lyotropic liquid crystalline nanoassemblies (LLCNs) are internally self-assembled (ISA)-somes formed by amphiphilic molecules in a mixture comprising a lipid, stabilizer, and/or surfactant and aqueous media/dispersant. LLCNs are unique nanoassemblies with versatile applications in a wide range of biomedical functions. However, they comprise a nanosystem that is yet to be fully explored for targeted systemic treatment of breast cancer. In this study, LLCNs proposed for gemcitabine and thymoquinone (Gem-TQ) co-delivery were prepared from soy phosphatidylcholine (SPC), phytantriol (PHYT), or glycerol monostearate (MYVR) in optimized ratios containing a component of citric and fatty acid ester-based emulsifier (Grinsted citrem) or a triblock copolymer, Pluronic F127 (F127). Hydrodynamic particle sizes determined were below 400 nm (ranged between 96 and 365 nm), and the series of nanoformulations displayed negative surface charge. Nonlamellar phases identified by small-angle X-ray scattering (SAXS) profiles comprise the hexagonal, cubic, and micellar phases. In addition, high entrapment efficiency that accounted for 98.3 ± 0.1% of Gem and 99.5 ± 0.1% of TQ encapsulated was demonstrated by the coloaded nanocarrier system, SPC/citrem/Gem-TQ hexosomes. Low cytotoxicity of SPC-citrem hexosomes was demonstrated in MCF10A cells consistent with hemo- and biocompatibility observed in zebrafish (Danio rerio) embryos for up to 96 h postfertilization (hpf). SPC/citrem/Gem-TQ hexosomes demonstrated IC50 of 24.7 ± 4.2 μM in MCF7 breast cancer cells following a 24 h treatment period with the moderately synergistic interaction between Gem and TQ retained (CI = 0.84). Taken together, biocompatible SPC/citrem/Gem-TQ hexosomes can be further developed as a multifunctional therapeutic nanodelivery approach, plausible for targeting breast cancer cells by incorporation of targeting ligands.

The Application of 18F-FES PET in Clinical Cancer Care: A Systematic Review

INTRODUCTION

[18F]fluoroestradiol (FES) can be used for the noninvasive visualization and quantification of tumor estrogen receptor (ER) expression and activity and was FDA-approved as a diagnostic agent in May 2022 for detecting ER-positive lesions in patients with recurrent or metastatic breast cancer. PET imaging was also used to detect ER-positive lesions and malignancy among patients with uterine, ovarian, and other ER-positive solid tumors. We conducted a systemic review of the studies on FES PET imaging used among patients with cancer not limited to breast cancer to better understand the application of FES PET imaging.

METHODS

PubMed/MEDLINE and Cochrane Library databases were used to perform a comprehensive and systematic search and were updated until August 15, 2022. Two authors independently reviewed the titles and abstracts of the retrieved articles by using the search algorithm and selected the articles based on the inclusion and exclusion criteria. All statistical analyses were conducted using R statistical software.

RESULTS

Forty-three studies with 2352 patients were included in the qualitative synthesis, and 23 studies with 1388 patients were included in the quantitative analysis, which estimated the FES-positive detection rate. Thirty-two studies (77%) included breast cancer patients in 43 included studies. The FES SUVmean was higher in patients with endometrial cancer (3.4-5.3) than in those with breast cancer (2.05) and uterine sarcoma (1.1-2.6). The pooled detection rates of FES PET imaging were 0.80 for breast and 0.84 for ovarian cancer patients, both similar to that of 18F-FDG. The FES uptake threshold of 1.1 to 1.82 could detect 11.1% to 45% ER heterogeneity, but the threshold of FES uptake did not have consistent predictive ability for prognosis among patients with breast cancer, unlike uterine cancer. However, FES uptake can effectively predict and monitor treatment response, especially endocrine therapy such as estradiol, ER-blocking agents (fulvestrant and tamifoxen), and aromatase inhibitors (such as letrozole and Z-endoxifen).

CONCLUSIONS

[18F]fluoroestradiol PET is not only a convenient and accurate diagnostic imaging tool for detecting ER-expressing lesions in patients with breast and ovarian cancer but also among patients with uterine cancer. [18F]fluoroestradiol PET is a noninvasive predictive and monitoring tool for treatment response and prognosis.

Biomarkers in Breast Cancer: An Old Story with a New End

Breast cancer is the second most frequent cancer in the world. It is a heterogeneous disease and the leading cause of cancer mortality in women. Advances in molecular technologies allowed for the identification of new and more specifics biomarkers for breast cancer diagnosis, prognosis, and risk prediction, enabling personalized treatments, improving therapy, and preventing overtreatment, undertreatment, and incorrect treatment. Several breast cancer biomarkers have been identified and, along with traditional biomarkers, they can assist physicians throughout treatment plan and increase therapy success. Despite the need of more data to improve specificity and determine the real clinical utility of some biomarkers, others are already established and can be used as a guide to make treatment decisions. In this review, we summarize the available traditional, novel, and potential biomarkers while also including gene expression profiles, breast cancer single-cell and polyploid giant cancer cells. We hope to help physicians understand tumor specific characteristics and support decision-making in patient-personalized clinical management, consequently improving treatment outcome.

VPS34-IN1 induces apoptosis of ER + breast cancer cells via activating PERK/ATF4/CHOP pathway

VPS34-IN1 is a specific selective inhibitor of Class III Phosphatidylinositol 3-kinase (PI3K) and has been shown to exhibit a significant antitumor effect in leukemia and liver cancer. In current study, we focused on the anticancer effect and potential mechanism of VPS34-IN1 in estrogen receptor positive (ER + ) breast cancer. Our results revealed that VPS34-IN1 inhibited the viability of ER + breast cancer cells in vitro and in vivo. Flow cytometry and western blot analyses showed that VPS34-IN1 treatment induced breast cancer cell apopotosis. Interestingly, VPS34-IN1 treatment activated protein kinase R (PKR)-like ER kinase (PERK) branch of endoplasmic reticulum (ER) stress. Furthermore, knockdown of PERK by siRNA or inhibition of PERK activity by chemical inhibitor GSK2656157 could attenuate VPS34-IN1-mediated apoptosis in ER + breast cancer cells. Collectively, VPS34-IN1 has an antitumor effect in breast cancer, and it may result from activating PERK/ATF4/CHOP pathway of ER stress to induce cell apoptosis. These findings broaden our understanding of the anti-breast cancer effects and mechanisms of VPS34-IN1 and provide new ideas and reference directions for the treatment of ER + breast cancer.

FOXA1 Reprogramming Dictates Retinoid X Receptor Response in ESR1-Mutant Breast Cancer

Estrogen receptor alpha (ER/ESR1) mutations occur in 30% to 40% of endocrine resistant ER-positive (ER+) breast cancer. Forkhead box A1 (FOXA1) is a key pioneer factor mediating ER-chromatin interactions and endocrine response in ER+ breast cancer, but its role in ESR1-mutant breast cancer remains unclear. Our previous FOXA1 chromatin immunoprecipitation sequencing (ChIP-seq) identified a large portion of redistributed binding sites in T47D genome-edited Y537S and D538G ESR1-mutant cells. Here, we further integrated FOXA1 genomic binding profile with the isogenic ER cistrome, accessible genome, and transcriptome data of T47D cell model. FOXA1 redistribution was significantly associated with transcriptomic alterations caused by ESR1 mutations. Furthermore, in ESR1-mutant cells, FOXA1-binding sites less frequently overlapped with ER, and differential gene expression was less associated with the canonical FOXA1-ER axis. Motif analysis revealed a unique enrichment of retinoid X receptor (RXR) motifs in FOXA1-binding sites of ESR1-mutant cells. Consistently, ESR1-mutant cells were more sensitive to growth stimulation with the RXR agonist LG268. The mutant-specific response was dependent on two RXR isoforms, RXR-α and RXR-β, with a stronger dependency on the latter. In addition, T3, the agonist of thyroid receptor (TR) also showed a similar growth-promoting effect in ESR1-mutant cells. Importantly, RXR antagonist HX531 blocked growth of ESR1-mutant cells and a patient-derived xenograft (PDX)-derived organoid with an ESR1 D538G mutation. Collectively, our data support the evidence for a stronger RXR response associated with FOXA1 reprograming in ESR1-mutant cells, suggesting development of therapeutic strategies targeting RXR pathways in breast tumors with ESR1 mutation.

IMPLICATIONS

It provides comprehensive characterization of the role of FOXA1 in ESR1-mutant breast cancer and potential therapeutic strategy through blocking RXR activation.

LINC00426 is a potential immune phenotype-related biomarker and an overall survival predictor in PAM50 luminal B breast cancer

Background: Breast cancer (BRCA) represents the most frequent diagnosed malignancy in women worldwide. Despite treatment advances, BRCAs eventually develop resistance to targeted therapies, resulting in poor prognosis. The identification of new biomarkers, like immune-related long non-coding RNAs (lncRNAs), could contribute to the clinical management of BRCA patients. In this report, we evaluated the LINC00426 expression in PAM50 BRCA subtypes from two clinical independent cohorts (BRCA-TCGA and GEO-GSE96058 datasets). Methods and results: Using Cox regression models and Kaplan-Meier survival analyses, we identified that LINC00426 expression was a consistent overall survival (OS) predictor in luminal B (LB) BRCA patients. Subsequently, differential gene expression and gene set enrichment analyses identified that LINC00426 expression was associated with different immune-related and cancer-related pathways and processes in LB BRCA. Additionally, the LINC00426 expression was correlated with the infiltration level of diverse immune cell populations, alongside immune checkpoint and cytolytic activity-related gene expression. Conclusion: This evidence suggests that LINC00426 is a potential biomarker of immune phenotype and an OS predictor in PAM50 LB BRCA.

An Update on Tamoxifen and the Chemo-Preventive Potential of Vitamin E in Breast Cancer Management

Breast cancer (BC) is the most common female cancer in terms of incidence and mortality worldwide. Tamoxifen (Nolvadex) is a widely prescribed, oral anti-estrogen drug for the hormonal treatment of estrogen-receptor-positive BC, which represents 70% of all BC subtypes. This review assesses the current knowledge on the molecular pharmacology of tamoxifen in terms of its anticancer and chemo-preventive actions. Due to the importance of vitamin E compounds, which are widely taken as a supplementary dietary component, the review focuses only on the potential importance of vitamin E in BC chemo-prevention. The chemo-preventive and onco-protective effects of tamoxifen combined with the potential effects of vitamin E can alter the anticancer actions of tamoxifen. Therefore, methods involving an individually designed, nutritional intervention for patients with BC warrant further consideration. These data are of great importance for tamoxifen chemo-prevention strategies in future epidemiological studies.

A Basic Review on Estrogen Receptor Signaling Pathways in Breast Cancer

Breast cancer is the most common cancer and the deadliest among women worldwide. Estrogen signaling is closely associated with hormone-dependent breast cancer (estrogen and progesterone receptor positive), which accounts for two-thirds of tumors. Hormone therapy using antiestrogens is the gold standard, but resistance to these treatments invariably occurs through various biological mechanisms, such as changes in estrogen receptor activity, mutations in the ESR1 gene, aberrant activation of the PI3K pathway or cell cycle dysregulations. All these factors have led to the development of new therapies, such as selective estrogen receptor degraders (SERDs), or combination therapies with cyclin-dependent kinases (CDK) 4/6 or PI3K inhibitors. Therefore, understanding the estrogen pathway is essential for the treatment and new drug development of hormone-dependent cancers. This mini-review summarizes current literature on the signalization, mechanisms of action and clinical implications of estrogen receptors in breast cancer.

CDK4/6 Inhibitors—Overcoming Endocrine Resistance Is the Standard in Patients with Hormone Receptor-Positive Breast Cancer

Purpose of review: Tamoxifen and aromatase inhibitors can be considered as some of the first targeted therapies. For the past 30 years, they were the endocrine treatment standard in the advanced and early breast cancer setting. CDK4/6 inhibitors, however, are the first substances in almost two decades to broadly improve the therapeutic landscape of hormone receptor-positive breast cancer patients for the upcoming years. This review is designed to discuss the recent history, current role, future directions and opportunities of this substance class. Recent findings: The CDK4/6 inhibitors abemaciclib, dalpiciclib, palbociclib and ribociclib have all demonstrated a statistically significant improvement in progression-free survival in advanced disease. However, to date, abemaciclib and ribociclib are the only CDK4/6 inhibitors to have shown an improvement in overall survival in patients with metastatic breast cancer. Moreover, abemaciclib is the first CDK4/6 inhibitor to also reduce the risk of recurrence in those with early-stage disease. Further CDK inhibitors, treatment combinations with other drugs and different therapy sequences are in development. Summary: Achieving significant improvements in survival rates in the advanced and early breast cancer treatment setting, CDK4/6 inhibitors have set a new standard of care for patients with advanced breast cancer. It remains important to better understand resistance mechanisms to be able to develop novel substances and treatment sequences.

Nuclear receptor modulators inhibit osteosarcoma cell proliferation and tumour growth by regulating the mTOR signaling pathway

Osteosarcoma is the most common primary malignant bone tumour in children and adolescents. Chemoresistance leads to poor responses to conventional therapy in patients with osteosarcoma. The discovery of novel effective therapeutic targets and drugs is still the main focus of osteosarcoma research. Nuclear receptors (NRs) have shown substantial promise as novel therapeutic targets for various cancers. In the present study, we performed a drug screen using 29 chemicals that specifically target 17 NRs in several different human osteosarcoma and osteoblast cell lines. The retinoic acid receptor beta (RARb) antagonist LE135, peroxisome proliferator activated receptor gamma (PPARg) antagonist T0070907, liver X receptor (LXR) agonist T0901317 and Rev-Erba agonist SR9011 significantly inhibited the proliferation of malignant osteosarcoma cells (U2OS, HOS-MNNG and Saos-2 cells) but did not inhibit the growth of normal osteoblasts. The effects of these NR modulators on osteosarcoma cells occurred in a dose-dependent manner and were not observed in NR-knockout osteosarcoma cells. These NR modulators also significantly inhibited osteosarcoma growth in vivo and enhanced the antitumour effect of doxorubicin (DOX). Transcriptomic and immunoblotting results showed that these NR modulators may inhibit the growth of osteosarcoma cells by regulating the PI3K/AKT/mTOR and ERK/mTOR pathways. DDIT4, which blocks mTOR activation, was identified as one of the common downstream target genes of these NRs. DDIT4 knockout significantly attenuated the inhibitory effects of these NR modulators on osteosarcoma cell growth. Together, our results revealed that modulators of RARb, PPARg, LXRs and Rev-Erba inhibit osteosarcoma growth both in vitro and in vivo through the mTOR signaling pathway, suggesting that treatment with these NR modulators is a novel potential therapeutic strategy.

An Exemestane Derivative, Oxymestane-D1, as a New Multi-Target Steroidal Aromatase Inhibitor for Estrogen Receptor-Positive (ER+) Breast Cancer: Effects on Sensitive and Resistant Cell Lines

Around 70-85% of all breast cancer (BC) cases are estrogen receptor-positive (ER⁺). The third generation of aromatase inhibitors (AIs) is the first-line treatment option for these tumors. Despite their therapeutic success, they induce several side effects and resistance, which limits their efficacy. Thus, it is crucial to search for novel, safe and more effective anti-cancer molecules. Currently, multi-target drugs are emerging, as they present higher efficacy and lower toxicity in comparison to standard options. Considering this, this work aimed to investigate the anti-cancer properties and the multi-target potential of the compound 1α,2α-epoxy-6-methylenandrost-4-ene-3,17-dione (Oxy), also designated by Oxymestane-D1, a derivative of Exemestane, which we previously synthesized and demonstrated to be a potent AI. For this purpose, it was studied for its effects on the ER⁺ BC cell line that overexpresses aromatase, MCF-7aro cells, as well as on the AIs-resistant BC cell line, LTEDaro cells. Oxy reduces cell viability, impairs DNA synthesis and induces apoptosis in MCF-7aro cells. Moreover, its growth-inhibitory properties are inhibited in the presence of ERα, ERβ and AR antagonists, suggesting a mechanism of action dependent on these receptors. In fact, Oxy decreased ERα expression and activation and induced AR overexpression with a pro-death effect. Complementary transactivation assays demonstrated that Oxy presents ER antagonist and AR agonist activities. In addition, Oxy also decreased the viability and caused apoptosis of LTEDaro cells. Therefore, this work highlights the discovery of a new and promising multi-target drug that, besides acting as an AI, appears to also act as an ERα antagonist and AR agonist. Thus, the multi-target action of Oxy may be a therapeutic advantage over the three AIs applied in clinic. Furthermore, this new multi-target compound has the ability to sensitize the AI-resistant BC cells, which represents another advantage over the endocrine therapy used in the clinic, since resistance is a major drawback in the clinic.

Efficacy and exploratory biomarker analysis of entinostat plus exemestane in advanced or recurrent breast cancer: phase II randomized controlled trial

BACKGROUND

We aimed to confirm the efficacy and safety of the oral histone deacetylase inhibitor entinostat in Japanese patients with hormone receptor-positive advanced/recurrent breast cancer and to explore potential biomarkers.

METHODS

This phase II, double-blind, randomized, placebo-controlled trial (ClinicalTrials.gov; NCT03291886) was conducted at 28 Japanese sites (September 2017-July 2020; interim analysis cutoff: April 2019). Patients with progression/relapse following non-steroidal aromatase inhibitors were randomized 1:1 to entinostat (5 mg/week) or placebo, plus exemestane (25 mg/day). Primary endpoint was progression-free survival; secondary endpoints included overall survival and safety. Exploratory biomarker outcomes included lysine acetylation, immune cell profiles, estrogen receptor 1 mutations and plasma chemokines.

RESULTS

Of 133 randomized patients, 131 (65 entinostat, 66 placebo) who received study drug were analyzed. Median (95% confidence interval) progression-free survival was 5.8 (3.2-7.8) months for entinostat and 3.3 (3.1-5.8) months for placebo (hazard ratio [95% confidence interval]: 0.75 [0.50 - 1.14]; P = 0.189). Median overall survival was not reached in either group. Entinostat tended to prolong progression-free survival in patients aged ≥65 years, not endocrine resistant, or with estrogen receptor 1 Y537S mutation. Candidate biomarkers of efficacy (progression-free survival) included lysine acetylation in CD3+ cells, plasma interferon gamma-induced protein 10, dendritic cell CD86 expression, and CD4+ cell expression of human leukocyte antigen-DR and inducible T-cell co-stimulator. Safety was similar to non-Japanese populations; however, seven entinostat-treated patients (10.8%) had reversible lung injury.

CONCLUSIONS

In Japanese patients, the safety of entinostat plus exemestane was acceptable and progression-free survival was prolonged, although not significantly. Exploratory analyses identified potential biomarkers, including lysine acetylation, of efficacy.

Targeting Estrogen Signaling in the Radiation-induced Neurodegeneration: A Possible Role of Phytoestrogens

Radiation for medical use is a well-established therapeutic method with an excellent prognosis rate for various cancer treatments. Unfortunately, a high dose of radiation therapy comes with its own share of side effects, causing radiation-induced non-specific cellular toxicity; consequently, a large percentage of treated patients suffer from chronic effects during the treatment and even after the post-treatment. Accumulating data evidenced that radiation exposure to the brain can alter the diverse cognitive-related signaling and cause progressive neurodegeneration in patients because of elevated oxidative stress, neuroinflammation, and loss of neurogenesis. Epidemiological studies suggested the beneficial effect of hormonal therapy using estrogen in slowing down the progression of various neuropathologies. Despite its primary function as a sex hormone, estrogen is also renowned for its neuroprotective activity and could manage radiation-induced side effects as it regulates many hallmarks of neurodegenerations. Thus, treatment with estrogen and estrogen-like molecules or modulators, including phytoestrogens, might be a potential approach capable of neuroprotection in radiation-induced brain degeneration. This review summarized the molecular mechanisms of radiation effects and estrogen signaling in the manifestation of neurodegeneration and highlighted the current evidence on the phytoestrogen mediated protective effect against radiationinduced brain injury. This existing knowledge points towards a new area to expand to identify the possible alternative therapy that can be taken with radiation therapy as adjuvants to improve patients' quality of life with compromised cognitive function.

Transcription Factors and Cancer: Approaches to Targeting

ABSTRACT

Cancer is defined by the presence of uncontrollable cell growth, whereby improper proliferative signaling has overcome regulation by cellular mechanisms. Transcription factors are uniquely situated at the helm of signaling, merging extracellular stimuli with intracellular responses. Therefore, this class of proteins plays a pivotal role in coordinating the correct gene expression levels for maintaining normal cellular functions. Dysregulation of transcription factor activity unsurprisingly drives tumorigenesis and oncogenic transformation. Although this imparts considerable therapeutic potential to targeting transcription factors, their lack of enzymatic activity renders intervention challenging and has contributed to a sense that transcription factors are "undruggable." Yet, enduring efforts to elucidate strategies for targeting transcription factors as well as a deeper understanding of their interactions with binding partners have led to advancements that are emerging to counter this narrative. Here, we highlight some of these approaches, focusing primarily on therapeutics that have advanced to the clinic.

Expression analysis elucidates the roles of Nicastrin, Notch4, and Hes1 in prognosis and endocrine-therapy resistance in ER-positive breast cancer patients

Background and purpose

Although some proposed mechanisms responsible for tamoxifen resistance have already been present, further study is needed to determine the mechanisms underlying tamoxifen resistance more clearly. The critical role of Notch signaling has been described in promoting resistance in therapeutics, but there is little information about its role in tamoxifen resistance progression.

Experimental approach

In the present study, the expression of Notch pathway genes, including Notch4, nicastrin and the Notch downstream target Hes1 was evaluated using quantitative RT-PCR in 36 tamoxifen-resistant (TAM-R) and 36 tamoxifen-sensitive (TAM-S) patients. Expression data were correlated with the clinical outcome and survival of patients.

Findings/Results

mRNA levels of Notch4 (fold change = 2.7), nicastrin (fold change = 6.71), and Hes1 (fold change= 7.07) were significantly higher in TAM-R breast carcinoma patients compared to sensitive cases. We confirmed all these genes were co-expressed. Hence, it seems that Notch signaling is involved in tamoxifen resistance in our TAM-R patients. Obtained results showed that Hes1, nicastrin, and Notch4 mRNA upregulation was correlated with the N stage. The extracapsular nodal extension was associated with nicastrin and Notch4 overexpression. Moreover, nicastrin overexpression was correlated with perineural invasion. Hes1 upregulation was also associated with nipple involvement. Finally, the Cox regression proportional hazard test revealed that overexpression of nicastrin was an independent worse survival factor.

Conclusion and implications

Presumably, upregulation of the Notch pathway may be involved in tamoxifen resistance in breast cancer patients.

p53 Mutation as Plausible Predictor for Endocrine Resistance Therapy in Luminal Breast Cancer

Endocrine therapy resistance in Luminal Breast Cancer is a significant issue to be tackled, but currently, no specific biomarker could be used to anticipate this event. p53 mutation is widely known as one of Breast Cancer's most prominent genetic alterations. Its mutation could generate various effects in Estrogen Receptor and Progesterone Receptor molecular works, tangled in events leading to the aggravation of endocrine therapy resistance. Hence the possibility of p53 mutation utilization as an endocrine therapy resistance predictive biomarker is plausible. The purpose of this review is to explore the latest knowledge of p53 role in Estrogen Receptor and Progesterone Receptor molecular actions, thus aggravating the Endocrine Therapy resistance in Luminal Breast Cancer, from which we could define possibilities and limitations to utilize p53 as the predictive biomarker of endocrine therapy resistance in Luminal Breast Cancer.

Deciphering the Role and Signaling Pathways of PKCα in Luminal A Breast Cancer Cells

Protein kinase C (PKC) comprises a family of highly related serine/threonine protein kinases involved in multiple signaling pathways, which control cell proliferation, survival, and differentiation. The role of PKCα in cancer has been studied for many years. However, it has been impossible to establish whether PKCα acts as an oncogene or a tumor suppressor. Here, we analyzed the importance of PKCα in cellular processes such as proliferation, migration, or apoptosis by inhibiting its gene expression in a luminal A breast cancer cell line (MCF-7). Differential expression analysis and phospho-kinase arrays of PKCα-KD vs. PKCα-WT MCF-7 cells identified an essential set of proteins and oncogenic kinases of the JAK/STAT and PI3K/AKT pathways that were down-regulated, whereas IGF1R, ERK1/2, and p53 were up-regulated. In addition, unexpected genes related to the interferon pathway appeared down-regulated, while PLC, ERBB4, or PDGFA displayed up-regulated. The integration of this information clearly showed us the usefulness of inhibiting a multifunctional kinase-like PKCα in the first step to control the tumor phenotype. Then allowing us to design a possible selection of specific inhibitors for the unexpected up-regulated pathways to further provide a second step of treatment to inhibit the proliferation and migration of MCF-7 cells. The results of this study suggest that PKCα plays an oncogenic role in this type of breast cancer model. In addition, it reveals the signaling mode of PKCα at both gene expression and kinase activation. In this way, a wide range of proteins can implement a new strategy to fine-tune the control of crucial functions in these cells and pave the way for designing targeted cancer therapies.

Loss of Brca1 and Trp53 in adult mouse mammary ductal epithelium results in development of hormone receptor-positive or hormone receptor-negative tumors, depending on inactivation of Rb family proteins

BACKGROUND

Breast cancer is a heterogenous disease with several histological and molecular subtypes. Models that represent these subtypes are essential for translational research aimed at improving clinical strategy for targeted therapeutics.

METHODS

Different combinations of genetic aberrations (Brca1 and Trp53 loss, and inhibition of proteins of the Rb family) were induced in the mammary gland by injection of adenovirus expressing Cre recombinase into the mammary ducts of adult genetically engineered mice. Mammary tumors with different genetic aberrations were classified into molecular subtypes based on expression of molecular markers and RNAseq analysis. In vitro potency assays and Western blots were used to examine their drug sensitivities.

RESULTS

Induction of Brca1 and Trp53 loss in mammary ductal epithelium resulted in development of basal-like hormone receptor (HR)-negative mammary tumors. Inhibition of Rb and Trp53 loss or the combination of Rb, Trp53 and Brca1 aberrations resulted in development of luminal ductal carcinoma positive for ER, PR, and Her2 expression. HR positivity in tumors with Rb, Trp53 and Brca1 aberrations indicated that functionality of the Rb pathway rather than Brca1 status affected HR status in these models. Mammary tumor gene expression profiles recapitulated human basal-like or luminal B breast cancer signatures, but HR-positive luminal cancer models were endocrine resistant and exhibited upregulation of PI3K signaling and sensitivity to this pathway inhibition. Furthermore, both tumor subtypes were resistant to CDK4/6 inhibition.

CONCLUSIONS

Examination of molecular expression profiles and drug sensitivities of tumors indicate that these breast cancer models can be utilized as a translational platform for evaluation of targeted combinations to improve chemotherapeutic response in patients that no longer respond to hormone therapy or that are resistant to CDK4/6 inhibition.

Molecular Mechanisms of Anti-Estrogen Therapy Resistance and Novel Targeted Therapies

Breast cancer (BC) is the most commonly diagnosed cancer in women, constituting one-third of all cancers in women, and it is the second leading cause of cancer-related deaths in the United States. Anti-estrogen therapies, such as selective estrogen receptor modulators, significantly improve survival in estrogen receptor-positive (ER+) BC patients, which represents about 70% of cases. However, about 60% of patients inevitably experience intrinsic or acquired resistance to anti-estrogen therapies, representing a major clinical problem that leads to relapse, metastasis, and patient deaths. The resistance mechanisms involve mutations of the direct targets of anti-estrogen therapies, compensatory survival pathways, as well as alterations in the expression of non-coding RNAs (e.g., microRNA) that regulate the activity of survival and signaling pathways. Although cyclin-dependent kinase 4/6 and phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) inhibitors have significantly improved survival, the efficacy of these therapies alone and in combination with anti-estrogen therapy for advanced ER+ BC, are not curative in advanced and metastatic disease. Therefore, understanding the molecular mechanisms causing treatment resistance is critical for developing highly effective therapies and improving patient survival. This review focuses on the key mechanisms that contribute to anti-estrogen therapy resistance and potential new treatment strategies alone and in combination with anti-estrogen drugs to improve the survival of BC patients.

The Present and Future of Clinical Management in Metastatic Breast Cancer

Regardless of the advances in our ability to detect early and treat breast cancer, it is still one of the common types of malignancy worldwide, with the majority of patients decease upon metastatic disease. Nevertheless, due to these advances, we have extensively characterized the drivers and molecular profiling of breast cancer and further dividing it into subtypes. These subgroups are based on immunohistological markers (Estrogen Receptor-ER; Progesterone Receptor-PR and Human Epidermal Growth Factor Receptor 2-HER-2) and transcriptomic signatures with distinct therapeutic approaches and regiments. These therapeutic approaches include targeted therapy (HER-2+), endocrine therapy (HR+) or chemotherapy (TNBC) with optional combination radiotherapy, depending on clinical stage. Technological and scientific advances in the identification of molecular pathways that contribute to therapy-resistance and establishment of metastatic disease, have provided the rationale for revolutionary targeted approaches against Cyclin-Dependent Kinases 4/6 (CDK4/6), PI3 Kinase (PI3K), Poly ADP Ribose Polymerase (PARP) and Programmed Death-Ligand 1 (PD-L1), among others. In this review, we focus on the comprehensive overview of epidemiology and current standard of care treatment of metastatic breast cancer, along with ongoing clinical trials. Towards this goal, we utilized available literature from PubMed and ongoing clinical trial information from clinicaltrials.gov to reflect the up to date and future treatment options for metastatic breast cancer.

CDK4/6 inhibitor resistance mechanisms and treatment strategies (Review)

In recent years, the incidence rate of breast cancer has increased year by year, and it has become a major threat to the health of women globally. Among all breast cancer subtypes, the hormone receptor (HR)⁺/human epidermal growth factor receptor 2 (HER2)⁻ luminal subtype breast cancer is the most common form of breast cancer. Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors, the hotspots in the field of targeted therapy for breast cancer, have proved to exhibit a good effect on patients with HR⁺/HER2⁻ breast cancer in a number of clinical trials, but the problem of drug resistance is inevitable. At present, three specific CDK4/6 inhibitors (palbociclib, ribociclib and abemaciclib) have been approved by the USA Food and Drug Administration for the first-line treatment of HR⁺/HER2⁻ breast cancer. The drug resistance mechanisms of CDK4/6 inhibitors can be divided into cell cycle-specific resistance and cell cycle non-specific resistance. With the discovery of the drug resistance mechanism of CDK4/6 inhibitors, various targeted strategies have been proposed. The present review mainly discusses the mechanism of CDK4/6 inhibitors, drug resistance mechanisms and treatment strategies after resistance.

Expert consensus on the clinical application of PI3K/AKT/mTOR inhibitors in the treatment of advanced breast cancer

Phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB or AKT)/mammalian target of rapamycin (mTOR) signaling pathway (PAM pathway) plays an important role in the development of breast cancer and are closely associated with the resistance to endocrine therapy in advanced breast cancer. Therefore, anticancer treatment targeting key molecules in this signaling pathway has become a research hotspot in recent years. Randomized clinical trials have demonstrated that PI3K/AKT/mTOR inhibitors bring significant clinical benefit to patients with advanced breast cancer, especially to those with hormone receptor (HR)-positive, human epidermal growth factor receptor (HER) 2-negative advanced breast cancer. Alpelisib, a PI3K inhibitor, and everolimus, an mTOR inhibitor, have been approved by FDA. Based on their high efficacy and relatively good safety profile, an expanded indication of everolimus in breast cancer has been approved by National Medical Products Administration (NMPA). Alpelisib is expected to be approved in China in the near future. The members of the consensus expert panel reached this consensus to comprehensively define the role of PI3K/AKT/mTOR signaling pathway in breast cancer, efficacy and clinical applications of PI3K/AKT/mTOR inhibitors, management of adverse reactions, and PIK3CA mutation detection, to promote the understanding of PI3K/AKT/mTOR inhibitors for Chinese oncologists, improve clinical decision-making, and prolong the survival of target patient population.

Estradiol and Estrogen-like Alternative Therapies in Use: The Importance of the Selective and Non-Classical Actions

Estrogen is one of the most important female sex hormones, and is indispensable for reproduction. However, its role is much wider. Among others, due to its neuroprotective effects, estrogen protects the brain against dementia and complications of traumatic injury. Previously, it was used mainly as a therapeutic option for influencing the menstrual cycle and treating menopausal symptoms. Unfortunately, hormone replacement therapy might be associated with detrimental side effects, such as increased risk of stroke and breast cancer, raising concerns about its safety. Thus, tissue-selective and non-classical estrogen analogues have become the focus of interest. Here, we review the current knowledge about estrogen effects in a broader sense, and the possibility of using selective estrogen-receptor modulators (SERMs), selective estrogen-receptor downregulators (SERDs), phytoestrogens, and activators of non-genomic estrogen-like signaling (ANGELS) molecules as treatment.

Gene Expression Changes by Diallyl Trisulfide Administration in Chemically-induced Mammary Tumors in Rats

Diallyl trisulfide (DATS) was shown to be a potent inhibitor of luminal-type MCF-7 xenograft growth in vivo. The present study was conducted to determine the preventive effect of DATS administration using an N-methyl-N-nitrosourea (MNU)-induced rat mammary tumor model, which shares molecular resemblance to luminal-type human breast cancers. The DATS administration (50 mg/kg body weight, 5 times/week) was safe, but did not reduce mammary tumor latency, incidence, burden or multiplicity. Therefore, we conducted RNA-seq analysis using mammary tumors from control and DATS-treated rats (n = 3 for each group) to gain insights into lack of mammary tumor prevention by this phytochemical. The gene ontology and the Kyoto encyclopedia of genes and genomes pathway analyses of the RNA-seq data revealed upregulation of genes associated with ribosomes, translation, peptide biosynthetic/metabolic process, and oxidative phosphorylation but downregulation of genes associated with mitogen-activated protein kinases. A total of 33 genes associated with ribosomes were significantly upregulated by DATS treatment, including RPL11 and RPS14. Western blotting confirmed upregulation of RPL11 and neurofascin protein expression in mammary tumors from DATS-treated rats when compared to controls. A statistically significant increase in protein level of c-Jun N-terminal kinase 2 was also observed in tumors from DATS-treated rats when compared to controls. On the other hand, expression of complex I subunits NDUFV1 or NDUFS1 was not affected by DATS treatment. These results offer potential explanations for ineffectiveness of DATS in the chemically-induced rat mammary tumor model. Inhibitors of the proteins upregulated by DATS may be needed to improve chemopreventive efficacy of this phytochemical.

AMEERA-5: a randomized, double-blind phase 3 study of amcenestrant plus palbociclib versus letrozole plus palbociclib for previously untreated ER+/HER2– advanced breast cancer

Background:

For estrogen receptor–positive (ER+)/human epidermal growth factor receptor 2–negative (HER2–) advanced breast cancer (ABC), the current standard first-line treatment includes an aromatase inhibitor in combination with a cyclin-dependent kinase 4/6 inhibitor. When resistance occurs, often related to the occurrence of ESR1 mutations, selective estrogen receptor modulators or degraders (SERDs) may be used, alone or in combination regimens. Amcenestrant (SAR439859), an optimized oral SERD, has shown clinical antitumor activity in combination with palbociclib in patients with ER+/HER2– ABC and, as monotherapy, in patients with and without ESR1 mutations. Here, we describe the study design of AMEERA-5, an ongoing, prospective, phase 3, randomized, double-blind, multinational study comparing the efficacy and safety of amcenestrant plus palbociclib versus letrozole plus palbociclib in patients with advanced (locoregional recurrent or metastatic) ER+/HER2– breast cancer.

Methods:

Patients are pre-/postmenopausal women and men with no prior systemic therapy for ABC. The planned enrollment is 1066 patients. Patients are randomized 1:1 to either amcenestrant 200 mg plus palbociclib 125 mg or letrozole 2.5 mg plus palbociclib 125 mg. Amcenestrant, letrozole, and their matching placebos are taken once daily continuously; palbociclib is taken once daily for 21 days, followed by 7 days off-treatment for a 28-day cycle. Treatment continues until disease progression, unacceptable toxicity, or decision to stop treatment. Pre-/perimenopausal women and men receive goserelin subcutaneously. Randomization is stratified by de novo metastatic disease, menopausal status, and visceral metastases. The primary endpoint is progression-free survival. The key secondary endpoint is overall survival; others are safety, pharmacokinetics, and quality of life.

Conclusions:

AMEERA-5 is evaluating the efficacy and safety of amcenestrant in combination with palbociclib as first-line therapy in pre-/postmenopausal women and men with ER+/HER2– ABC.

ClinicalTrials Identifier:

NCT04478266.

Impacts of endocrine-disrupting chemicals on prostate function and cancer

Because of their historical mode of action, endocrine-disrupting chemicals (EDCs) are associated with sex-steroid receptors, namely the two estrogen receptors (ERα and ERβ) and the androgen receptor (AR). Broadly, EDCs can modulate sex-steroid receptor functions. They can also indirectly impact the androgen and estrogen pathways by influencing steroidogenesis, expression of AR or ERs, and their respective activity as transcription factors. Additionally, many of these chemicals have multiple cellular targets other than sex-steroid receptors, which results in a myriad of potential effects in humans. The current article reviews the association between prostate cancer and the endocrine-disrupting functions of four prominent EDC families: bisphenols, phthalates, phytoestrogens, and mycoestrogens. Results from both in vitro and in vivo models are included and discussed to better assess the molecular mechanisms by which EDCs can modify prostate biology. To overcome the heterogeneity of results published, we established common guidelines to properly study EDCs in the context of endocrine diseases. Firstly, the expression of sex-steroid receptors in the models used must be determined before testing. Then, in parallel to EDCs, pharmacological compounds acting as positive (agonists) and negative controls (antagonists) have to be employed. Finally, EDCs need to be used in a precise range of concentrations to modulate sex-steroid receptors and avoid off-target effects. By adequately integrating molecular endocrinology aspects in EDC studies and identifying their underlying molecular mechanisms, we will truly understand their impact on prostate cancer and distinguish those that favor the progression of the disease from those that slow down tumor development.

Loss of REST in breast cancer promotes tumor progression through estrogen sensitization, MMP24 and CEMIP overexpression

BACKGROUND

Breast cancer is the most common malignancy in women, and is both pathologically and genetically heterogeneous, making early detection and treatment difficult. A subset of breast cancers express normal levels of REST (repressor element 1 silencing transcription factor) mRNA but lack functional REST protein. Loss of REST function is seen in ~ 20% of breast cancers and is associated with a more aggressive phenotype and poor prognosis. Despite the frequent loss of REST, little is known about the role of REST in the molecular pathogenesis of breast cancer.

METHODS

TCGA data was analyzed for the expression of REST target genes in breast cancer patient samples. We then utilized gene knockdown in MCF-7 cells in the presence or absence of steroid hormones estrogen and/ progesterone followed by RNA sequencing, as well as chromatin immunoprecipitation and PCR in an attempt to understand the tumor suppressor role of REST in breast cancer.

RESULTS

We show that REST directly regulates CEMIP (cell migration-inducing and hyaluronan-binding protein, KIAA1199) and MMP24 (matrix metallopeptidase 24), genes known to have roles in invasion and metastasis. REST knockdown in breast cancer cells leads to significant upregulation of CEMIP and MMP24. In addition, we found REST binds to RE-1 sites (repressor element-1) within the genes and influences their transcription. Furthermore, we found that the estrogen receptor (ESR1) signaling pathway is activated in the absence of REST, regardless of hormone treatment.

CONCLUSIONS

We demonstrate a critical role for the loss of REST in aggressive breast cancer pathogenesis and provide evidence for REST as an important diagnostic marker for personalized treatment plans.

Piperlongumine as a Neuro-Protectant in Chemotherapy Induced Cognitive Impairment

Advances in the early diagnosis and treatment have led to increases in breast cancer survivorship. Survivors report cognitive impairment symptoms such as loss of concentration and learning and memory deficits which significantly reduce the patient's quality of life. Additional therapies are needed to prevent these side effects and, the precise mechanisms of action responsible are not fully elucidated. However, increasing evidence points toward the use of neuroprotective compounds with antioxidants and anti-inflammatory properties as tools for conserving learning and memory. Here, we examine the ability of piperlongumine (PL), an alkaloid known to have anti-inflammatory and antioxidant effects, to play a neuroprotective role in 16-week-old female C57BL/6J mice treated with a common breast cancer regimen of doxorubicin, cyclophosphamide, and docetaxel (TAC). During social memory testing, TAC-treated mice exhibited impairment, while TAC/PL co-treated mice did not exhibit measurable social memory deficits. Proteomics analysis showed ERK1/2 signaling is involved in TAC and TAC/PL co-treatment. Reduced Nrf2 mRNA expression was also observed. mRNA levels of Gria2 were increased in TAC treated mice and reduced in TAC/PL co-treated mice. In this study, PL protects against social memory impairment when co-administered with TAC via multifactorial mechanisms involving oxidative stress and synaptic plasticity.

The estrogen receptor beta agonist liquiritigenin enhances the inhibitory effects of the cholesterol biosynthesis inhibitor RO 48-8071 on hormone-dependent breast-cancer growth

PURPOSE

Most hormone-dependent human breast cancers develop resistance to anti-hormone therapy over time. Our goal was to identify novel treatment strategies to avoid this drug resistance and thereby control hormone-dependent breast cancer.

METHODS

Sulforhodamine B assays were used to measure viability of cultured human breast-cancer cells. BT-474 cell tumor xenografts in nude mice were used to evaluate tumor growth. Immunohistochemistry was used to assess estrogen-receptor and angiogenesis-marker expression, as well as apoptosis, in tumor-xenograft tissues.

RESULTS

MCF-7 and BT-474 breast-cancer cells treated with either RO 48-8071 <[4'-[6-(Allylmethylamino)hexyloxy]-4-bromo-2'-fluorobenzophenone fumarate] [RO]; a small-molecule inhibitor of oxidosqualene cyclase, a key enzyme in cholesterol biosynthesis> or liquiritigenin [LQ; an estrogen receptor (ER) β agonist] exhibited significantly reduced viability in vitro. RO + LQ treatment further significantly reduced cell viability. Administration of RO, LQ, or RO + LQ significantly inhibited growth of BT-474 tumor xenografts in vivo. RO, LQ, or RO + LQ reduced ERα but induced ER β expression in tumor xenografts. Both compounds significantly reduced angiogenesis-marker expression and increased apoptosis in tumor xenografts; use of RO + LQ significantly enhanced the effects observed with a single agent.

CONCLUSION

The ERβ ligand LQ significantly enhanced the inhibition of breast-cancer cell viability and tumor-xenograft growth by RO. The anti-tumor properties of RO may in part be due to an off-target effect that reduces ERα and increases ERβ, the latter of which can then interact with LQ to promote anti-proliferative effects. The RO + LQ combination may have value when considering novel treatment strategies for hormone-dependent breast cancer.

Comprehensive immunohistochemical analysis of RET, BCAR1, and BCAR3 expression in patients with Luminal A and B breast cancer subtypes

PURPOSE

Breast cancer (BC) is considered a heterogeneous disease composed of distinct subtypes with diverse clinical outcomes. Luminal subtype tumors have the best prognosis, and patients benefit from endocrine therapy. However, resistance to endocrine therapies in BC is an obstacle to successful treatment, and novel biomarkers are needed to understand and overcome this mechanism. The RET, BCAR1, and BCAR3 genes may be associated with BC progression and endocrine resistance.

METHODS

Aiming to evaluate the expression profile and prognostic value of RET, BCAR1, and BCAR3, we performed immunohistochemistry on tissue microarrays (TMAs) containing a cohort of 361 Luminal subtype BC.

RESULTS

Low expression levels of these three proteins were predominantly observed. BCAR1 expression was correlated with nuclear grade (p = 0.057), and BCAR3 expression was correlated with lymph node status (p = 0.011) and response to hormonal therapy (p = 0.021). Further, low expression of either BCAR1 or BCAR3 was significantly associated with poor prognosis (p = 0.005; p = 0.042). Pairwise analysis showed that patients with tumors with low BCAR1/low BCAR3 expression had a poorer overall survival (p = 0.013), and the low BCAR3 expression had the worst prognosis with RET high expression stratifying these patients into two different groups. Regarding the response to hormonal therapy, non-responder patients presented lower expression of RET in comparison to the responder group (p = 0.035). Additionally, the low BCAR1 expression patients had poorer outcomes than BCAR1 high (p = 0.015).

CONCLUSION

Our findings suggest RET, BCAR1, and BCAR3 as potential candidate markers for endocrine therapy resistance in Luminal BC.

Transcriptomic Analysis of Breast Cancer Patients Sensitive and Resistant to Chemotherapy: Looking for Overall Survival and Drug Resistance Biomarkers

Worldwide breast cancer ranks first in mortality and incidence rates in women over 20 years old. Rather than one disease, breast cancer is a heterogeneous group of diseases that express distinct molecular profiles. Neoadjuvant chemotherapy is an important therapeutic strategy for breast cancer patients independently of their molecular subtype, with the drawback of resistance development. In addition, chemotherapy has adverse effects that combined with resistance could contribute to lower overall survival. Although great efforts have been made to find diagnostic and prognostic biomarkers for breast cancer and for response to targeted and immune therapy for this pathology, little has been explored regarding biomarkers of response to anthracyclines and taxanes based neoadjuvant chemotherapy. This work aimed to evaluate the molecular profile of patients who received neoadjuvant chemotherapy to identify differentially expressed genes (DEGs) that could be used as biomarkers of chemotherapy response and overall survival. Breast cancer patients who were candidates for neoadjuvant chemotherapy were enrolled in this study. After treatment and according to their pathological response, they were assigned as sensitive or resistant. To evaluate DEGs, Gene Ontology, Kyoto Encyclopedia Gene and Genome (KEGG), and protein–protein interactions, RNA-seq information from all patients was obtained by next-generation sequencing. A total of 1985 DEGs were found, and KEGG analysis indicated a great number of DEGs in metabolic pathways, pathways in cancer, cytokine–cytokine receptor interactions, and neuroactive ligand-receptor interactions. A selection of 73 DEGs was used further for an analysis of overall survival using the METABRIC study and the ductal carcinoma dataset of The Cancer Genome Atlas (TCGA) database. Nine DEGs correlated with overall survival, of which the subexpression of C1QTNF3, CTF1, OLFML3, PLA2R1, PODN, KRT15, HLA-A, and the overexpression of TUBB and TCP1 were found in resistant patients and related to patients with lower overall survival.

FoxO3a Inhibits Tamoxifen-Resistant Breast Cancer Progression by Inducing Integrin α5 Expression

Resistance to endocrine therapy is still a major clinical challenge in the management of estrogen receptor α-positive (ERα+) breast cancer (BC). Here, the role of the Forkhead box class O (FoxO)3a transcription factor in tumor progression has been evaluated in tamoxifen-resistant BC cells (TamR), expressing lower levels of FoxO3a compared to sensitive ones. FoxO3a re-expression reduces TamR motility (wound-healing and transmigration assays) and invasiveness (matrigel transwell invasion assays) through the mRNA (qRT-PCR) and protein (Western blot) induction of the integrin α5 subunit of the α5β1 fibronectin receptor, a well-known membrane heterodimer controlling cell adhesion and signaling. The induction occurs through FoxO3a binding to a specific Forkhead responsive core sequence located on the integrin α5 promoter (cloning, luciferase, and ChIP assays). Moreover, FoxO3a failed to inhibit migration and invasion in integrin α5 silenced (siRNA) cells, demonstrating integrin α5 involvement in both processes. Finally, using large-scale gene expression data sets, a strong positive correlation between FoxO3a and integrin α5 in ERα+, but not in ER-negative (ERα-), BC patients emerged. Altogether, our data show how the oncosuppressor FoxO3a, by increasing the expression of its novel transcriptional target integrin α5, reverts the phenotype of endocrine-resistant BC toward a lower aggressiveness.

Expression of GALNT8 and O-glycosylation of BMP receptor 1A suppress breast cancer cell proliferation by upregulating ERα levels

BACKGROUND

Mucin-type O-glycosylation is one of the most abundant types of O-glycosylation and plays important roles in various human carcinomas, including breast cancer. A large family of polypeptide N-acetyl-α-galactosaminyltransferases (GALNTs) initiate and define sites of mucin-type O-glycosylation. However, the specific mechanisms underlying GALNT8 expression and its roles in tumorigenesis remain poorly characterized.

METHODS

GALNT8 expression was assessed in 140 breast cancer patients. Immunofluorescence, immunoprecipitation, lectin blot and quantitative real-time PCR were used to investigate the expression of GALNT8 and its role in regulating estrogen receptor α (ERα) via bone morphogenetic protein (BMP) signaling.

RESULTS

The expression of GALNT8 was associated with breast cancer patient survival. GALNT8 downregulation was associated with a reduction in ERα levels, while GALNT8 overexpression elevated the transcription and protein levels of ERα and suppressed colony formation, suggesting an important role of GALNT8 in cancer cell proliferation. Conversely, GALNT8 knockdown led to the inhibition of BMP/SMAD/RUNX2 axis, which decreased ERα transcription. Further analysis suggested that BMP receptor 1A (BMPR1A) was O-GalNAcylated. Sites mutation of BMPR1A indicated that Thr137 and Ser37/Ser39/Ser44/Thr49 of BMPR1A were the main O-glycosylation sites. Although we cannot exclude the indirect effect of GALNT8, our results demonstrated that the expression of GALNT8 and O-glycosylation of BMPR1A play key roles in regulating the activity of BMP/SMAD/RUNX2 signaling and ERα expression.

CONCLUSION

These findings suggest that GALNT8 expression and abnormal O-GalNAcylation of BMPR1A increase ERα expression and suppress breast cancer cell proliferation by modulating the BMP signaling pathway.

GENERAL SIGNIFICANCE

Our results identify the involvement of GALNT8 in regulating ERα expression.

Endocrine Treatment for Breast Cancer Patients Revisited-History, Standard of Care, and Possibilities of Improvement

PURPOSE OF REVIEW

Due to the findings of current studies and the approval of novel substances for the therapy of hormone-receptor-positive breast cancer patients, the established standards of endocrine treatment are changing. The purpose of this review is to give an overview of the history of endocrine treatment, to clarify its role in the present standard of care, and to discuss the possibilities of improvement.

RECENT FINDINGS

Tamoxifen, aromatase inhibitors, and fulvestrant are the main drugs that have been used for decades in the therapy of hormone-receptor-positive breast cancer patients. However, since a relevant number of women suffer at some point from disease recurrence or progression, several novel substances are being investigated to overcome resistance mechanisms by interfering with certain signaling pathways, such as the PI3K/AKT/mTOR or the CDK4/6 pathways. mTOR and CDK4/6 inhibitors were the first drugs approved for this purpose and many more are in development.

SUMMARY

Endocrine treatment is one of the best tolerable cancer therapies available. Continuous investigation serves to improve patients' outcomes and modernize the current standard of care. Considering the resistance mechanisms and substances analyzed against these, endocrine treatment of hormone-receptor-positive breast cancer is on the brink of a new era.

Resistance to endocrine therapy in HR + and/or HER2 + breast cancer: the most promising predictive biomarkers

Breast cancer is the most common cancer in women. It is a heterogeneous disease, encompassing different biological subtypes that differ in histological features, outcomes, clinical behaviour and different molecular subtypes. Therapy has progressed substantially over the past years with a reduction both for locoregional and systemic therapy. Endocrine therapies have considerably reduced cancer recurrence and mortality. Despite the major diagnostic and therapeutic innovations, resistance to therapy has become a main challenge, especially in metastatic breast cancer, and became a major factor limiting the use of endocrine therapeutic agents in ER positive breast cancers. Approximately 50% of patients with ER positive metastatic disease achieve a complete or partial response with endocrine therapy. However, in the remaining patients, the benefit is limited due to resistance, intrinsic or acquired, resulting in disease progression and poor outcome.Tumour heterogeneity as well as acquired genetic changes and therapeutics pressure have been involved in the endocrine therapy resistance. Nowadays, targeted sequencing of genes involved in cancer has provided insights about genomic tumour evolution throughout treatment and resistance driver mutations. Several studies have described multiple alterations in receptor tyrosine kinases, signalling pathways such as Phosphoinositide-3-kinase-protein kinase B/Akt/mTOR (PI3K/Akt/mTOR) and Mitogen-activated protein kinase (MAPK), cell cycle machinery and their implications in endocrine treatment failure.One of the current concern in cancer is personalized therapy. The focus has been the discovery of new potentially predictive biomarkers capable to identify reliably the most appropriate therapy regimen and which patients will experience disease relapse. The major concern is also to avoid overtreatment/undertreatment and development of resistance.This review focuses on the most promising predictive biomarkers of resistance in estrogen receptor-positive breast cancer and the emerging role of circulating free-DNA as a powerful tool for longitudinal monitoring of tumour molecular profile throughout treatment.

NRIP1 is activated by C-JUN/C-FOS and activates the expression of PGR, ESR1 and CCND1 in luminal A breast cancer

Using chip array assays, we identified differentially expressed genes via a comparison between luminal A breast cancer subtype and normal mammary ductal cells from healthy donors. In silico analysis confirmed by western blot and immunohistochemistry revealed that C-JUN and C-FOS transcription factors are activated in luminal A patients as potential upstream regulators of these differentially expressed genes. Using a chip-on-chip assay, we identified potential C-JUN and C-FOS targets. Among these genes, the NRIP1 gene was revealed to be targeted by C-JUN and C-FOS. This was confirmed after identification and validation with transfection assays specific binding of C-JUN and C-FOS at consensus binding sites. NRIP1 is not only upregulated in luminal A patients and cell lines but also regulates breast cancer-related genes, including PR, ESR1 and CCND1. These results were confirmed by NRIP1 siRNA knockdown and chip array assays, thus highlighting the putative role of NRIP1 in PGR, ESR1 and CCND1 transcriptional regulation and suggesting that NRIP1 could play an important role in breast cancer ductal cell initiation.

A practical guide to endocrine therapy in the management of estrogen receptor-positive male breast cancer

The majority (more than 90%) of male breast cancers (MaBCs) are estrogen receptor-positive, such that endocrine therapy is the mainstay of MaBC treatment. Endocrine therapy has been associated with improved overall survival in observational studies on MaBC, though large randomized clinical trials have never been completed to confirm this benefit in this population. Tamoxifen is currently the preferred drug for both metastatic and adjuvant treatment of MaBC. Known differences in treatment patterns and hormonal milieu between men and women may warrant a unique approach to the management of toxicities in men. This review provides a detailed discussion of endocrine therapy for MaBC.

Breast Cancer Treatments: Updates and New Challenges

Breast cancer (BC) is the most frequent cancer diagnosed in women worldwide. This heterogeneous disease can be classified into four molecular subtypes (luminal A, luminal B, HER2 and triple-negative breast cancer (TNBC)) according to the expression of the estrogen receptor (ER) and the progesterone receptor (PR), and the overexpression of the human epidermal growth factor receptor 2 (HER2). Current BC treatments target these receptors (endocrine and anti-HER2 therapies) as a personalized treatment. Along with chemotherapy and radiotherapy, these therapies can have severe adverse effects and patients can develop resistance to these agents. Moreover, TNBC do not have standardized treatments. Hence, a deeper understanding of the development of new treatments that are more specific and effective in treating each BC subgroup is key. New approaches have recently emerged such as immunotherapy, conjugated antibodies, and targeting other metabolic pathways. This review summarizes current BC treatments and explores the new treatment strategies from a personalized therapy perspective and the resulting challenges.