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Background: Inter- and intra-tumor heterogeneity is considered a significant factor contributing to the development of endocrine resistance in breast cancer. Recent advances in single-cell RNA sequencing (scRNA-seq) and single-cell ATAC sequencing (scATAC-seq) allow us to explore inter- and intra-tumor heterogeneity at single-cell resolution. However, such integrated single-cell analysis has not yet been demonstrated to characterize the transcriptome and chromatin accessibility in breast cancer endocrine resistance., Methods: In this study, we conducted an integrated analysis combining scRNA-seq and scATAC-seq on more than 80,000 breast tissue cells from two normal tissues (NTs), three primary tumors (PTs), and three tamoxifen-treated recurrent tumors (RTs). A variety of cell types among breast tumor tissues were identified, PT- and RT-specific cancer cell states (CSs) were defined, and a heterogeneity-guided core signature (HCS) was derived through such integrated analysis. Functional experiments were performed to validate the oncogenic role of BMP7, a key gene within the core signature., Results: We observed a striking level of cell-to-cell heterogeneity among six tumor tissues and delineated the primary to recurrent tumor progression, underscoring the significance of these single-cell level tumor cell clusters classified from scRNA-seq data. We defined nine CSs, including five PT-specific, three RT-specific, and one PT-RT-shared CSs, and identified distinct open chromatin regions of CSs, as well as a HCS of 137 genes. In addition, we predicted specific transcription factors (TFs) associated with the core signature and novel biological/metabolism pathways that mediate the communications between CSs and the tumor microenvironment (TME). We finally demonstrated that BMP7 plays an oncogenic role in tamoxifen-resistant breast cancer cells through modulating MAPK signaling pathways., Conclusions: Our integrated single-cell analysis provides a comprehensive understanding of the tumor heterogeneity in tamoxifen resistance. We envision this integrated single-cell epigenomic and transcriptomic measure will become a powerful approach to unravel how epigenetic factors and the tumor microenvironment govern the development of tumor heterogeneity and to uncover potential therapeutic targets that circumvent heterogeneity-related failures., Competing Interests: Declarations Ethics approval and consent to participate This study uses previously collected breast cancer patients’ pathological specimens, or diagnostic specimens from various biospecimen resources that have already been granted local Institutional Review Board (IRB) protocol approvals. All patients’ samples are de-identified but included with some basic clinical features. We will not have any keys that may link specific Health Insurance Portability and Accountability Act (HIPAA)-defined protected health information (PHI) to specific individuals. Medical College of Wisconsin has granted this study without an IRB; therefore, ethics approval was waived in this case. This study was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki. Consent for publication Not applicable. Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Plasmalogens are vinyl-ether glycerophospholipids critical for the structure and function of neuronal membranes. Deficient plasmalogen levels are associated with neurodegenerative diseases, particularly Alzheimer's disease (AD), which has led to the hypothesis that plasmalogen deficiency might drive disease onset and progression. However, the lack of a suitable animal model with late-onset plasmalogen deficiency has prevented testing of this hypothesis. The goal of this project was therefore to develop and characterize a mouse model capable of undergoing a plasmalogen deficiency only in adulthood, mirroring the chronic decline thought to occur in AD. We report here the creation of a novel animal model containing a tamoxifen-inducible knockout of the Gnpat gene encoding the first step in the plasmalogen biosynthetic pathway. Tamoxifen treatment in adult animals resulted in a significant reduction of plasmalogens in both the circulation and tissues as early as four weeks. By four months, changes in behavior and nerve function were observed, with strong correlations between residual brain plasmalogen levels, hyperactivity, and latency. The model will be useful for further elucidating the role of plasmalogens in AD and evaluating plasmalogen therapies., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Tara Smith reports financial support was provided by Med-Life Discoveries LP. Kaeli J Knudsen reports financial support was provided by Med-Life Discoveries LP. Shawn A Ritchie reports financial support was provided by Med-Life Discoveries LP. Tara Smith reports a relationship with Med-Life Discoveries LP that includes: employment. Kaeli J Knudsen reports a relationship with Med-Life Discoveries LP that includes: employment. Shawn A Ritchie reports a relationship with Med-Life Discoveries LP that includes: employment. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Breast cancer (BC) is the most common malignancy among females worldwide, and its high metastasis rates are the leading cause of death just after lung cancer. Currently, tamoxifen (TAM) is a hydrophobic anticancer agent and a selective estrogen modulator (SERM), approved by the FDA that has shown potential anticancer activity against BC, but the non-targeted delivery has serious side effects that limit its ubiquitous utility. Therefore, releasing anti-cancer drugs precisely to the tumor site can improve efficacy and reduce the side effects on the body. Nanotechnology has emerged as one of the most important strategies to solve the issue of overdose TAM toxicity, owing to the ability of nano-enabled formulations to deliver desirable quantity of TAM to cancer cells over a longer period of time. In view of this, use of fluorescent carbon nanoparticles in targeted drug delivery holds novel promise for improving the efficacy, safety, and specificity of TAM therapy. Here, we synthesized biocompatible carbon nanoparticles (CNPs) using chitosan molecules without any toxic surface passivating agent. Synthesized CNPs exhibit good water dispersibility and emit intense blue fluorescence upon excitation (360 nm source). The surface of the CNPs has been functionalized with folate using click chemistry to improve the targeted drug uptake by the malignant cell. The pH difference between cancer and normal cells was successfully exploited to trigger TAM release at the target site. After six hours of incubation, CNPs released ∼ 74 % of the TAM drug in acidic pH. In vitro, studies have also demonstrated that after treatment with the synthesized CNPs, significant inhibition of the tumor growth could be achieved., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Latrophilin-2 (Lphn2), an adhesive GPCR (G protein-coupled receptor), was found to be a specific marker of cardiac progenitors during the differentiation of pluripotent stem cells into cardiomyocytes or during embryonic heart development in our previous studies. Its role in adult heart physiology, however, remains unclear., Methods: The embryonic lethality resulting from Lphn2 deletion necessitates the establishment of cardiomyocyte-specific, tamoxifen-inducible Lphn2 knockout mice, which was achieved by crossing Lphn2  flox/flox mice with mice having MerCreMer (tamoxifen-inducible Cre [Cyclization recombinase] recombinase) under the α-myosin heavy chain promoter., Results: Tamoxifen treatment for several days completely suppressed Lphn2 expression, specifically in the myocardium, and induced the dilated cardiomyopathy (D-CMP) phenotype with serious arrhythmia and sudden death in a short period of time. Transmission electron microscopy showed mitochondrial abnormalities, blurred Z-discs, and dehiscent myofibrils. The D-CMP phenotype, or heart failure, worsened during myocardial infarction. In a mechanistic study of D-CMP, Lphn2 knockout suppressed PGC-1α (Peroxisome proliferator-activated receptor gamma coactivator 1-alpha) and mitochondrial dysfunction, leading to the accumulation of reactive oxygen species and the global suppression of junctional molecules, such as N-cadherin (adherens junction), DSC-2 (desmocollin-2; desmosome), and connexin-43 (gap junction), leading to the dehiscence of cardiac myofibers and serious arrhythmia. In an experimental therapeutic trial, activators of p38-MAPK (p38 mitogen-activated protein kinases), which is a downstream signaling molecule of Lphn2, remarkably rescued the D-CMP phenotype of Lphn2 knockout in the heart by restoring PGC-1α and mitochondrial function and recovering global junctional proteins., Conclusions: Lphn2 is a critical regulator of heart integrity by controlling mitochondrial functions and cell-to-cell junctions in cardiomyocytes. Its deficiency leads to D-CMP, which can be rescued by activators of the p38-MAPK pathway., Competing Interests: None.

Purpose: Fibroblast growth factor receptor 2 (Fgfr2) is crucial for the homeostasis of meibomian gland (MG). However, the role of Fgfr2 in MG ductal epithelial progenitors remains to be delineated. Herein, we created a new transgenic mouse model with conditional deletion of Fgfr2 from MG ductal progenitors and investigated the cell-specific role in the pathogenesis of obstructive meibomian gland dysfunction., Methods: Peritoneal injection of tamoxifen (TAM) at 50 µg/gm for three consecutive days was performed to induce conditional deletion of Fgfr2 in two-month-old Krt5Fgfr2CKO or Krt5Fgfr2CKO-mTmG mice. Phenotypes of MG after Fgfr2 deletion were monitored by meibography, lipid staining, and immunostaining against keratin-6a in MG whole mounts. Lineage tracing of the Krt5+ progenitors of MG and biomarkers for ductal differentiation and proliferation were also examined by immunostainings., Results: The Krt5Fgfr2CKO mice developed extensive ductal occlusion and acinar atrophy at day 10 after TAM administration. Robust thickening of ductal epithelium with abnormal differentiation and proliferation of ductal basal meibocytes were observed in the MGs of Krt5Fgfr2CKO mice. In Krt5Fgfr2CKO-mTmG mice, the Krt5+ progenitors and its progeny were labeled by EGFP after Fgfr2 depletion by TAM with evident expansion of the suprabasal and superficial layers of MG ductal epithelium when compared with the controls., Conclusions: Our results substantiated the crucial role of Fgfr2 in homeostasis of the MG ductal epithelium. Deletion of Fgfr2 affects the MG ductal basal progenitors by impacting the differentiation of ductal meibocytes and the maintenance of acinar meibocytes, which are likely the underlying pathogenesis of obstructive MGD.

Centronuclear myopathies are rare congenital disorders characterized by muscle weakness and mislocalization of organelles. The main genes associated to these muscle diseases are MTM1, DNM2, BIN1 and RYR1. To date, no therapy is available. Nevertheless, tamoxifen, a pharmacological compound already used in clinics for breast cancer, showed beneficial effects on the muscle phenotypes in mouse models for centronuclear myopathies. Here, the effects of tamoxifen on muscle phenotypes will be compared in the various forms of this muscle disease., (© 2024 médecine/sciences – Inserm.)

Purpose: This research investigates the role of PPARγ in the complex molecular events underlying the acquisition of resistance to tamoxifen (Tam) in luminal A breast cancer (BC) cells. Furthermore, it focuses on evaluating the possibility of repurposing Imatinib mesylate, an FDA-approved anticancer agent recently recognized also as a PPARγ antagonist, for the personalized therapy of endocrine-resistant BC with increased PPARγ expression., Methods: Differential gene expression between parental and Tam-resistant MCF7 cells was assessed by RNA-seq followed by bioinformatics analysis and validation by RT-qPCR. PPARγ was downregulated by esiRNAs or inhibited by the antagonist GW9662. Cell viability and proliferation were measured by MTT and colony formation assays. Spheroids were prepared from parental and Tam-resistant MCF7 cells. Other luminal A BC cell lines resistant to Tam were generated., Results: In MCF7-TamR cells, PPARγ and several of its target genes were significantly upregulated. Increased PPARγ expression was due to the modulation of its positive/negative transcriptional regulators. Downregulating PPARγ with esiRNAs or GW9662 effectively killed parental and Tam-resistant cells and spheroids. Imatinib revealed to be as effective as GW9662 in restoring Tam susceptibility of these cells. PPARγ overexpression was also observed in the newly-selected Tam-resistant luminal A BC cells, in which GW9662 and Imatinib restored their susceptibility to Tam., Conclusion: Our findings demonstrate that the overexpression of PPARγ is a frequent occurrence during acquisition of Tam resistance in luminal A BC cells, and that PPARγ antagonism represents an alternative therapeutic approach for the personalized treatment of BC showing dysregulation of this nuclear receptor., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Background: Orlistat (Orli) is an anti-obesity medication that has been approved by the US Food and Drug Administration. It has relatively limited oral bioavailability with promising inhibitory effects on cell proliferation as well as reducing the growth of tumors., Aims: This investigation was done to evaluate the potential protective effect of Tamoxifen/Orlistat nanocrystals alone or in combination against Solid Ehrlich Carcinoma (SEC) and to clarify the possible underlying influences., Materials and Methods: The liquid antisolvent precipitation technique (bottom-up technology) was utilized to manufacture Orlistat Nanocrystals. To explore potential causes for the anti-tumor action, female Swiss Albino mice bearing SEC were randomly assigned into five equal groups (n = 6). Group 1: Tumor control group, group 2: Tam group: tamoxifen (0.01 g/kg, IP), group 3: Free-Orli group: orlistat (0.24 g/kg, IP), group 4: Nano-Orli: orlistat nanocrystals (0.24 g/kg, IP), group 5: Tam-Nano-Orli: Both doses of Tam and Nano-Orli. All treatments were administered for 16 days., Key Findings: The untreated mice showed development in the tumor volume and weight. As well as histopathology results from these mice revealed many tumor large cells as well as solid sheets of malignant cells. Also, untreated mice showed raised VEGF and TGF-1beta content. Moreover, results of gene expression in the SEC-bearing mice noted upregulation in HIF-1α, MMP-9, Bcl-2, and P27 gene expression and downregulation of TXNIP, BAX, and P53 gene expression. On the other hand, administrated TAM, Free-Orli, Nano-Orli, and a combination of Tam-Nano-Orli distinctly suppressed the tumor effects on estimated parameters with special reference to Tam-Nano-Orli., Significance: The developed Tamoxifen/Orlistat nanocrystals combination could be considered a promising approach to augment antitumor effects., Competing Interests: Declaration of Competing Interest The authors declare that there is no conflict of interest., (Copyright © 2024. Published by Elsevier Masson SAS.)

Background and Purpose: Radiotherapy (RT) is an integral treatment part for patients with head and neck squamous cell carcinoma (HNSCC), but radioresistance remains a major issue. Here, we use MitoTam, a mitochondrially targeted analogue of tamoxifen, which we aim to stimulate ferroptotic cell death with, and sensitize radioresistant cells to RT., Materials and Methods: We assessed viability, reactive oxygen species (ROS) production, disruption of mitochondrial membrane potential, and lipid peroxidation in radiosensitive (UT-SCC-40) and radioresistant (UT-SCC-5) HNSCC cells following MitoTam treatment. To assess ferroptosis specificity, we used the ferroptosis inhibitor ferrostatin-1 (fer-1). Also, total antioxidant capacity and sensitivity to tert-butyl hydroperoxide were evaluated to assess ROS-responses. 53BP1 staining was used to assess radiosensitivity after MitoTam treatment., Results: Our data revealed increased ROS, cell death, disruption of mitochondrial membrane potential, and lipid peroxidation following MitoTam treatment in both cell lines. Adverse effects of MitoTam on cell death, membrane potential and lipid peroxidation were prevented by fer-1, indicating induction of ferroptosis. Radioresistant HNSCC cells were less sensitive to the effects of MitoTam due to intrinsic higher antioxidant capacity. MitoTam treatment prior to RT led to superadditive residual DNA damage expressed by 53BP1 foci compared to RT or MitoTam alone., Conclusion: MitoTam induced ferroptosis in HNSCC cells, which could be used to overcome the elevated antioxidant capacity of radioresistant cells and sensitize such cells to RT. Treatment with MitoTam followed by RT could therefore present a promising effective therapy of radioresistant cancers., Statement of Significance: Radiotherapy is applied in the treatment of a majority of cancer patients. Radioresistance due to elevated antioxidant levels can be overcome by promoting ferroptotic cell death combining ROS-inducing drug MitoTam with radiotherapy., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [J.N., J.S. and L.W. own part of MitoTam intellectual property]., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Tamoxifen resistance is a common and difficult problem in the clinical treatment of breast cancer (BC). As a novel antitumor agent, Micheliolide (MCL) has shown a better therapeutic effect on tumours; however, little is known about MCL and its role in BC therapy. With tamoxifen stimulation, drug-resistant BC cells MCF7TAMR and T47DTAMR obtained a high oxidative status and Amidohydrolase 1 (ASAH1) was abnormally activated. The inhibition of ASAH1 rescued the sensitivity of resistant cells to tamoxifen. We found that MCL inhibited the expression of ASAH1 and cell proliferation, especially in MCF7TAMR and T47DTAMR cells. The high oxidative stress status of resistant cells stimulated the expression of ASAH1 by positively regulating AKT, which was restrained by MCL. MCL activated NRF2 by directly binding to KEAP1 and promoting the antioxidant level of tamoxifen-resistant (TAMR) cells. In addition, ACT001, the prodrug of MCL, significantly inhibited the tumour growth of TAMR cells in preclinical xenograft tumour models. In conclusion, ASAH1 mediates tamoxifen resistance in ER-positive BC cells. MCL could activate the cellular antioxidant system via NRF2/KEAP1 and inhibit ASAH1 expression through the ROS/AKT signalling pathway, thus suppressing cell proliferation. MCL could be used as a potential treatment for TAMR-BC., (© 2024 The Author(s). Cell Proliferation published by Beijing Institute for Stem Cell and Regenerative Medicine and John Wiley & Sons Ltd.)

Non-alcoholic steatohepatitis (NASH) is a severe liver condition characterized by excessive fat deposition, ballooning, and lobular inflammation. This investigation was conducted to estimate the capability of concomitant tamoxifen administration (TAM) with a high fat diet (HFD) to induce a reliable NASH model that mimics human NASH features. Rats were administered TAM (25 mg/kg/day p.o.) and consumed HFD for 5 weeks. A time-course investigation was conducted to determine the optimal time for NASH development. Liver function indices, hepatic lipid profile factors, oxidative stress biomarkers, and inflammatory mediators were estimated. Additionally, macroscopic and microscopic changes were examined. Compared with the time-matched control group receiving vehicle alone, TAM/HFD significantly impaired liver function indices represented as marked elevation in ALT, AST, and ALP serum levels. TAM/HFD significantly increased lipid profile factors including high TG and TC hepatic levels. Additionally, TAM/HFD remarkably raised hepatic levels of TNF-α and IL-17 and significantly decreased IL-10. The combination also increases the oxidative status evidenced by high content of MDA as well as low activity of GPx and SOD. Accordingly, the combination of TAM and HFD for 5 weeks collaboratively promotes NASH development by initiating compromised hepatocyte functionality, elevated lipid levels, oxidative stress, and liver inflammation., (© 2024. The Author(s).)

Breast cancer (BC) is a highly heterogeneous tumor that has surpassed lung cancer as the most frequently diagnosed cancer in women. In clinical practice,the primary approach for treating estrogen receptor alpha (ERα)-positive BC is through endocrine therapy, which involves targeting the ERα using medications like tamoxifen and fulvestrant. However, the problem of de novo or acquired resistance poses a significant clinical challenge, emphasizing the critical need for the development of novel therapeutic strategies. In this regard, we have successfully designed and developed a novel selective estrogen receptor degrader (SERD) called OBHSA, which specifically targets and degrades ERα, demonstrating remarkable efficacy. Our findings revealed the effectiveness of OBHSA in inhibiting the proliferation of various BC cells, including both tamoxifen-sensitive and tamoxifen-resistant BC cells, indicating its great potential to overcome endocrine resistance. In terms of mechanism, we discovered that OBHSA overcame tamoxifen resistance through two distinct pathways. Firstly, OBHSA degraded cyclin D1 in an ERα-dependent manner, thereby blocking the cell cycle. Secondly, OBHSA induced an elevation in intracellular reactive oxygen species, triggering an excessive activation of the unfolded protein response (UPR) and ultimately leading to apoptotic cell death. In summary, our finding demonstrated that OBHSA exerts anti-tumor effects by inducing cell cycle arrest and UPR-mediated apoptosis. These findings hold promise for the development of novel therapeutic drugs targeting endocrine-resistant BC., Competing Interests: Declaration of Competing Interest I would like to declare that all authors have given their permission to submit this manuscript. Furthermore, there are no conflicts of interest exist in the submission of this manuscript, including financial and personal relationships that may affect our work. The manuscript is approved by all authors for publication. The research described in the manuscript is original and has not been published elsewhere, in whole or in part. All the authors listed have approved the manuscript is enclosed., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Connexin 43 (Cx43) is a gap junction protein that participates in small molecule exchange between adjacent cells. It is a predominant Cx within the mammalian ovary, where is associated with proper follicle development. The expression and regulation of Cx43 in the chicken ovary is largely unknown. The aim of the present study was to examine the expression of the Cx43 gene (GJA1) and protein as well as the immunolocalization of Cx43 in the laying hen ovary in relation to follicle development, and to examine how tamoxifen (TMX; an estrogen receptor modulator) treatment affects these factors. qRT-PCR and western blotting demonstrated differences in Cx43 mRNA transcript and protein abundances in ovarian white follicles, yellowish follicles, small yellow follicles, and the largest yellow preovulatory follicles (F3-F1). In general, Cx43 was more abundant in hierarchical than prehierarchical follicles and in granulosa cells compared with theca cells. Further, the response to TMX treatment depended on the stage of follicle development and the layer of the follicular wall. Ovarian regression following TMX treatment was accompanied by an increase in Cx43 expression in most ovarian tissues, which may impact the formation and function of Cx43 hemichannels. Overall, our results showed, for the first time, the differences in Cx43 mRNA and protein levels between ovarian follicles, suggesting the potential involvement of this gap junction protein in the regulation of ovarian follicle development and function. In addition, the results indicate a possible role for estradiol in regulation of Cx43 transcription and/or translation in the chicken ovary. Understanding the contribution of Cx43 in mechanisms underlying ovarian follicle development may be of considerable importance for poultry egg production., Competing Interests: Declaration of competing interest None of the authors have any conflict of interest to declare., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Neurogenesis occurs in the adult brain in the hippocampal dentate gyrus, an area that contains neurons which are vulnerable to insults and injury, such as severe seizures. Previous studies showed that increasing adult neurogenesis reduced neuronal damage after these seizures. Because the damage typically is followed by chronic life-long seizures (epilepsy), we asked if increasing adult-born neurons would prevent epilepsy. Adult-born neurons were selectively increased by deleting the pro-apoptotic gene Bax from Nestin-expressing progenitors. Tamoxifen was administered at 6 weeks of age to conditionally delete Bax in Nestin-CreER T2 Bax fl/fl mice. Six weeks after tamoxifen administration, severe seizures (status epilepticus; SE) were induced by injection of the convulsant pilocarpine. After mice developed epilepsy, seizure frequency was quantified for 3 weeks. Mice with increased adult-born neurons exhibited fewer chronic seizures. Postictal depression was reduced also. These results were primarily in female mice, possibly because they were more affected by Bax deletion than males, consistent with sex differences in Bax . The female mice with enhanced adult-born neurons also showed less neuronal loss of hilar mossy cells and hilar somatostatin-expressing neurons than wild-type females or males, which is notable because loss of these two hilar cell types is implicated in epileptogenesis. The results suggest that selective Bax deletion to increase adult-born neurons can reduce experimental epilepsy, and the effect shows a striking sex difference. The results are surprising in light of past studies showing that suppressing adult-born neurons can also reduce chronic seizures., Competing Interests: SJ, JL, KG, JB, MK, CC No competing interests declared, HS Reviewing editor, eLife, (© 2023, Jain et al.)

DUX4 is the major gene responsible for facioscapulohumeral dystrophy (FSHD). Several mouse models expressing DUX4 have been developed, the most commonly used by academic laboratories being ACTA1-MCM/FLExDUX4. In this study, molecular and histological modifications in the tibialis anterior and quadriceps muscles were investigated in this model at different time points. We investigated several changes that could be used as markers of therapeutic efficacy. Our results confirm the progressive muscular dystrophy previously described but also highlight biases associated with tamoxifen injections and the complexity of choosing the genes used to calculate a DUX4-pathway gene composite score. We also developed a comprehensive force test that better reflects the movements made in everyday life. This functional force-velocity-endurance model, which describes the force production capacities at all velocity and fatigue levels, was applied on 12-13-week-old animals without tamoxifen. Our data highlight that previously unsuspected muscle properties are also affected by the expression of DUX4, leading to a weaker muscle with a lower initial muscle force but with preserved power and endurance capacity. Importantly, this force-velocity-endurance approach can be used in humans for clinical evaluations.

Currently, there are no specific antiviral therapeutic approaches targeting Human papillomaviruses (HPVs), which cause around 5% of all human cancers. Specific antiviral reagents are particularly needed for HPV-related oropharyngeal cancers (HPV + OPCs) whose incidence is increasing and for which there are no early diagnostic tools available. We and others have demonstrated that the estrogen receptor alpha (ERα) is overexpressed in HPV + OPCs, compared to HPV-negative cancers in this region, and that these elevated levels are associated with an improved disease outcome. Utilizing this HPV + -specific overexpression profile, we previously demonstrated that estrogen attenuates the growth and cell viability of HPV + keratinocytes and HPV + cancer cells in vitro . Expansion of this work in vivo failed to replicate this sensitization. The role of stromal support from the tumor microenvironment (TME) has previously been tied to both the HPV lifecycle and in vivo therapeutic responses. Our investigations revealed that in vitro co-culture with fibroblasts attenuated HPV + -specific estrogen growth responses. Continuing to monopolize on the HPV + -specific overexpression of ERα, our co-culture models then assessed the suitability of the selective estrogen receptor modulators (SERMs), raloxifene and tamoxifen, and showed growth attenuation in a variety of our models to one or both of these drugs in vitro . Utilization of these SERMs in vivo closely resembled the sensitization predicted by our co-culture models. Therefore, the in vitro fibroblast co-culture model better predicts in vivo responses. We propose that utilization of our co-culture in vitro model can accelerate cancer therapeutic drug discovery., Importance: Human papillomavirus-related cancers (HPV + cancers) remain a significant public health concern, and specific clinical approaches are desperately needed. In translating drug response data from in vitro to in vivo , the fibroblasts of the adjacent stromal support network play a key role. Our study presents the utilization of a fibroblast 2D co-culture system to better predict translational drug assessments for HPV + cancers. We also suggest that this co-culture system should be considered for other translational approaches. Predicting even a portion of treatment paradigms that may fail in vivo with a co-culture model will yield significant time, effort, resource, and cost efficiencies., Competing Interests: The authors declare no conflict of interest.

Introduction: Breast cancer is a significant public health problem around the world, ranking first in deaths due to cancer in females. The therapy to fight breast cancer involves different methods, including conventional chemotherapy. However, the acquired resistance that tumors develop during the treatment is still a central cause of cancer-associated deaths. One mechanism that induces drug resistance is cell communication via extracellular vesicles (EVs), which can carry efflux transporters and miRNA that increase sensitive cells' survivability to chemotherapy., Methods: Our study investigates the transcription changes modulated by EVs from tamoxifen- and doxorubicin-resistant breast cancer cells in sensitive cells and how these changes may induce acquired drug resistance, inhibit apoptosis, and increase survivability in the sensitive cells. Additionally, we exposed human macrophages to resistant EVs to understand the influence of EVs on immune responses., Results: Our results suggest that the acquired drug resistance is associated with the ability of resistant EVs to upregulate several transporter classes, which are directly related to the increase of cell viability and survival of sensitive cells exposed to EVs before a low-dose drug treatment. In addition, we show evidence that resistant EVs may downregulate immune system factors to evade detection and block cell death by apoptosis in sensitive breast cancer cells. Our data also reveals that human macrophages in contact with resistant EVs trigger a pro-inflammatory cytokine secretion profile, an effect that may be helpful for future immunotherapy studies., Discussion: These findings are the first transcriptome-wide analysis of cells exposed to resistant EVs, supporting that resistant EVs are associated with the acquired drug resistance process during chemotherapy by modulating different aspects of sensitive cancer cells that coffer the chemoresistance., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Santos, Rezende, Piraine, Oliveira, Ferreira, Carvalho, Calado, Pellegrini and Almeida.)

Background: Estrogen receptor-positive breast cancer accounts for around 70% of all cases. Tamoxifen, an anti-estrogenic inhibitor, is the primary drug used for this type of breast cancer treatment. However, tamoxifen resistance is a major challenge in clinics. Metabolic reprogramming, an emerging hallmark of cancer, plays a key role in cancer initiation, progression, and therapy resistance. The metabolism of non-essential amino acids such as serine, proline, and glutamine is involved in tumor metabolism reprogramming. Although the association of glutamine metabolism with tamoxifen resistance has been well established, the role of proline metabolism and its critical enzyme PRODH is unknown., Objective: The aim of this study is to explore the role and mechanism of PRODH in tamoxifen resistance in breast cancer cells., Methods: PRODH and GPX4 expressions in tamoxifen-resistant cells were detected using real-time PCR and Western blot analysis. The breast cells' response to tamoxifen was measured using MTT assays. Trans-well assays were used to detect cell migration and invasion. A Xenograft tumor assay was used to detect the role of PRODH in tumor growth. Reactive oxygen species were measured using flow cytometry., Results: PRODH expression is reduced in tamoxifen-resistant cells, and its overexpression enhances tamoxifen response in vitro and in vivo. Conversely, PRODH knockdown confers tamoxifen resistance in tamoxifen-sensitive cells. Mechanistic studies show that ferroptosis is inhibited in tamoxifen-resistant cells and overexpression of PRODH restores the ferroptosis in tamoxifen-resistant cells. Moreover, Ferrostatin-1 (Fer-1), the ferroptosis inhibitor, reversed the effect of PRODH on tamoxifen resistance., Conclusions: These findings suggest that PRODH regulates tamoxifen resistance by regulating ferroptosis in tamoxifen-resistant cells.

Tamoxifen (TAM) resistance is a major challenge in treating oestrogen receptor-positive (ER+) breast cancers. It is possible that the H 2 S synthase cystathionine-γ-lyase (CSE), which has been previously shown to promote tumour growth and metastasis in other cancer cells, is involved in this resistance. Therefore, we investigated CSE's role and potential mechanisms in TAM-resistant breast cancer cells. First, we examined the effect of CSE expression on TAM sensitivity and resistance in MCF7 (breast cancer) cells. The findings revealed that CSE was directly associated with TAM sensitivity and involved in TAM resistance in ER+ breast cancer cells, indicating that it may be useful as a biomarker. Next, we wanted to determine the molecular mechanism of CSE's role in TAM resistance. Using cell migration, co-immunoprecipitation, western blotting, and cell viability assays, we determined that the CSE/H2S system can affect the expression of PPARγ by promoting the sulfhydrylation of PPARγ, which regulates the transcriptional activity of ACSL1. ACSL1, in turn, influences STAT3 activation by affecting the phosphorylation, palmitoylation and dimerization of STAT3, ultimately leading to the development of TAM resistance in breast cancer. Finally, we examined the effect of CSE inhibitors on reducing drug resistance to determine whether CSE may be used as a biomarker of TAM resistance. We observed that the novel CSE inhibitor I194496 can reverse TAM resistance in TAM-resistant breast cancer via targeting the PPARγ/ACSL1/STAT3 signalling pathway. Overall, our data indicate that CSE may serve as a biomarker of TAM resistance and that the CSE inhibitor I194496 is a promising candidate for combating TAM resistance., (© 2024. The Author(s).)

Nanotechnology is emerging as a promising tool to enhance traditional cancer treatments due to rising chemotherapy resistance and the severe side effects of toxic drugs. Silver nanoparticles (AgNPs) are widely acknowledged for their antimicrobial and antiproliferative properties. Given these AgNP characteristics, this research conducts a comprehensive nanotoxicological assessment of strategic combinations involving AgNPs (68 nm) commercial formulation and tamoxifen on MCF-7 and MDA-MB-231 breast tumor cells. Utilizing CompuSyn software, the combination index was determined, revealing a synergistic cytotoxic and antiproliferative effect in AgNPs and tamoxifen combinations (CI < 0.97). Furthermore, this combination impaired cell migration (the scratch zone expanded by over 270%) and significantly increased reactive oxygen species production (up to 96% for MDA-MB-231 and 52% for MCF-7 cells). Surprisingly, the genotoxic effect of these mixtures was minimal (below the allowable genotoxicity index of 1.5). Additionally, both breast tumor cell lines exhibited increased proapoptotic and oxidative stress gene expression following the combined treatment. The internalization of AgNPs into breast cancer cells was observed, enhancing their synergistic antiproliferative effect when combined with tamoxifen. These findings suggest the potential of combining AgNPs with chemotherapeutic agents for innovative studies in oncology therapy., (© 2024 The Author(s). Journal of Biochemical and Molecular Toxicology published by Wiley Periodicals LLC.)

Resistance to endocrine therapy is a major clinical challenge in estrogen receptor (ER)-positive breast cancer. Obesity is associated with the clinical response to ER-positive breast cancers; however, the mechanism underlying obesity-induced resistance to endocrine therapy in ER-positive breast cancers remains unclear. In this study, we investigated the molecular mechanisms underlying obesity-induced resistance to tamoxifen (TAM), an anti-estrogen agent, in the ER-positive breast cancer cell line MCF-7 using differentiated adipocyte-conditioned medium (D-CM). Treatment of the cells with D-CM promoted TAM resistance by reducing TAM-induced apoptosis. The expression levels of the ERα target genes were higher in D-CM-treated cells than those in untreated ones. In contrast, when the cells were cultured in the presence of TAM, the expression levels were decreased, with or without D-CM. Moreover, the expression of the markers for cancer stem-like cells (CSCs) and mammosphere formation was enhanced by co-treating with D-CM and TAM, compared with TAM alone. The phosphatidylinositol-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway was activated in MCF-7 cells by D-CM treatment, even in the presence of TAM. Inhibition of the PI3K/Akt/mTOR pathway decreased the expression levels of the CSC markers, suppressed mammosphere formation, and resensitized to TAM via inducing apoptosis in D-CM-treated cells. These results indicate that the conditioned medium of differentiated adipocytes promoted TAM resistance by inducing the CSC phenotype through activation of the PI3K/Akt/mTOR pathway in ER-positive breast cancer cells. Thus, the PI3K/Akt/mTOR pathway may be a therapeutic target in obese patients with ER-positive breast cancers., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Tamoxifen is a widely used anti‑estrogen drug in the endocrine therapy of breast cancer (BC). It blocks estrogen signaling by competitively binding to estrogen receptor α (ERα), thereby inhibiting the growth of BC cells. However, with the long‑term application of tamoxifen, a subset of patients with BC have shown resistance to tamoxifen, which leads to low overall survival and progression‑free survival. The molecular mechanism of resistance is mainly due to downregulation of ERα expression and abnormal activation of the PI3K/AKT/mTOR signaling pathway. Moreover, the downregulation of targeted gene expression mediated by DNA methylation is an important regulatory mode to control protein expression. In the present review, methylation and tamoxifen are briefly introduced, followed by a focus on the effect of methylation on tamoxifen resistance and sensitivity. Finally, the clinical application of methylation for tamoxifen is described, including its use as a prognostic indicator. Finally, it is hypothesized that when methylation is used in combination with tamoxifen, it could recover the resistance of tamoxifen.

Purpose: Rapid proliferation and nutrition starvation in the tumor microenvironment pose significant challenges to cellular protein homeostasis. The accumulation of misfolded proteins in the endoplasmic reticulum lumen induces stress on cells and causes irreversible damage to cells if unresolved. Emerging reports emphasize the influence of the tumor microenvironment on therapeutic molecule efficacy and treatment outcomes. Hence, we aimed to understand the influence of tamoxifen on the cellular adaptation to endoplasmic reticulum stress during metabolic stress in breast cancer cells., Methods: Nutrition deprivation induces endoplasmic reticulum stress (ER stress), and the unfolded protein response (UPR) in breast cancer cells was confirmed by a Thioflavin B assay and western blotting. Tamoxifen-indued ER-phagy was studied using an MCD assay, confocal microscopy, and western blotting., Results: Nutrition deprivation induces ER stress in breast cancer cells. Interestingly, tamoxifen modulates the nutrition deprivation-induced endoplasmic reticulum stress through enhancing the selective ER-phagy, a specialized autophagy. The tamoxifen-induced ER-phagy is mediated by AMPK activation. The pharmacological inhibition of AMPK blocks tamoxifen-induced ER-phagy and tamoxifen modulatory effect on ER stress during nutrition deprivation., Conclusion: Tamoxifen modulates ER stress by inducing ER-phagy through AMPK, thereby, may support breast cancer cell survival during nutrition deprivation conditions., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Researchers are encountering challenges in addressing the issue of cancer cells becoming unresponsive to various chemotherapy treatments due to drug resistance. This study was designed to study the influence of antioxidant resveratrol (RSV) to sensitize resistant breast cancer (BC) cells toward tamoxifen (TAM). The cytotoxic effects of RSV and TAM against TAM-resistant LCC2 cells and their parental michigan cancer foundation-7 BC cells were determined by sulphorhodamine B assay. Further, the expression levels of multidrug resistance (MDR) genes including ABCB1, ABCC2, ABCG2, and MRP1 using quantitative polymerase chain reaction, apoptosis induction, and reactive oxygen species (ROS) content using flow cytometry were evaluated in either LCC2 cells treated with RSV, TAM, or their combination. The obtained results showed that resistant cells have a magnificent level of MDR genes. This elevated expression dramatically lowered upon receiving the combined therapy of RSV and TAM. Additionally, our work assessed the possible role of RSV in modulating the expression of MDR genes by controlling the expression of certain microRNAs (miRNAs) that target ATP-binding cassette (ABC) transporters. According to the obtained data, the TAM and RSV combination increased the expression of tumor inhibitor miRNAs such miR-10b-3p, miR-195-3p, and miR-223-3p, which made LCC2 cells more sensitive to TAM. Furthermore, this combination showed an elevation in apoptotic levels and total ROS content. The combination between RSV and TAM could be a functional therapy in the fight against TAM-resistant BC cells via modulating miRNA and ABC transporters., (© 2024 Deutsche Pharmazeutische Gesellschaft.)

Purpose: Tamoxifen, a widely used drug for breast cancer treatment, is associated with adverse effects on the liver, including the development of fatty liver. This study aimed to investigate the potential protective effect of caffeine against tamoxifen-induced fatty liver in Wistar rats., Methods: Rats were divided into normal control, tamoxifen + saline, and tamoxifen + caffeine. Plasma samples were assessed for biochemical markers related to oxidative stress, inflammation, liver function, and cell damage. Additionally, liver histopathology was examined to quantify the extent of fatty infiltration., Results: In the tamoxifen + saline group, elevated levels of plasma malondialdehyde (MDA), tumor necrosis factor-alpha (TNF-α), alanine aminotransferase (ALT), cytokeratin 18, and soluble ST2 were observed compared to the normal control group, indicating increased oxidative stress, inflammation, and liver injury (p < 0.01). Moreover, histopathological examination revealed a significant increase in fatty infiltration (p < 0.001). However, in the tamoxifen + caffeine group, these markers were markedly reduced (p < 0.05, p < 0.01), and fatty infiltration was significantly mitigated (p < 0.001)., Conclusions: The findings suggest that caffeine administration attenuates tamoxifen-induced fatty liver in rats by ameliorating oxidative stress, inflammation, liver injury, and cell damage. Histopathological evidence further supports the protective role of caffeine. This study highlights the potential of caffeine as a therapeutic intervention to counter tamoxifen-induced hepatic complications, contributing to the optimization of breast cancer treatment strategies.

This study investigates the potential of 2-methoxyestradiol (2-ME) to overcome tamoxifen (TAM) resistance in MCF-7 breast cancer cells by downregulating hypoxia-inducible factor 1 alpha (HIF-1α). Through a series of in vitro experiments, the authors demonstrate that combining 2-ME with TAM enhances the cytotoxic effects on resistant cells, increases apoptosis markers, and reduces cholesterol and triglyceride levels. While the findings highlight a promising therapeutic approach, the lack of in vivo or clinical data limits direct clinical application. Future research should focus on validating these results in animal models and exploring long-term efficacy and molecular mechanisms., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: Drug combination therapy is preferred over monotherapy in clinical research to improve therapeutic effects. Developing a new nanodelivery system for cancer drugs can reduce side effects and provide several advantages, including matched pharmacokinetics and potential synergistic activity. This study aimed to examine and determine the efficiency of the gemini surfactants (GSs) as a pH-sensitive polymeric carrier and cell-penetrating agent in cancer cells to achieve dual drug delivery and synergistic effects of curcumin (Cur) combined with tamoxifen citrate (TMX) in the treatment of MCF-7 and MDA-MB-231 human BC cell lines., Methods: The synthesized NPs were self-assembled using a modified nanoprecipitation method. The functional groups and crystalline form of the nanoformulation were examined by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and dynamic light scattering (DLS) used to assess zeta potential and particle size, and the morphological analysis determined by transmission electron microscopy (TEM). The anticancer effect was evaluated through an in vitro cytotoxicity MTT assay, flow cytometry analysis, and apoptosis analysis performed for mechanism investigation., Results: The tailored NPs were developed with a size of 252.3 ± 24.6 nm and zeta potential of 18.2 ± 4.4 mV capable of crossing the membrane of cancer cells. The drug loading and release efficacy assessment showed that the loading of TMX and Cur were 93.84% ± 1.95% and 90.18% ± 0.56%, respectively. In addition, the drug release was more controlled and slower than the free state. Polymeric nanocarriers improved controlled drug release 72.19 ± 2.72% of Tmx and 55.50 ± 2.86% of Cur were released from the Tmx-Cur-Gs NPs after 72 h at pH = 5.5. This confirms the positive effect of polymeric nanocarriers on the controlled drug release mechanism. moreover, the toxicity test showed that combination-drug delivery was much more greater than single-drug delivery in MCF-7 and MDA-MB-231 cell lines. Cellular imaging showed excellent internalization of TMX-Cur-GS NPs in both MCF-7 and MDA-MB-231 cells and synergistic anticancer effects, with combination indices of 0.561 and 0.353, respectively., Conclusion: The combined drug delivery system had a greater toxic effect on cell lines than single-drug delivery. The synergistic effect of TMX and Cur with decreasing inhibitory concentrations could be a more promising system for BC-targeted therapy using GS NPs., (© 2024. The Author(s).)

Medical treatment with low ozone concentrations proved to exert therapeutic effects in various diseases by inducing a cytoprotective antioxidant response through the nuclear factor erythroid derived-like 2 (Nrf2) transcription factor pathway. Low ozone doses are increasingly administered to oncological patients as a complementary treatment to mitigate some adverse side-effects of antitumor treatments. However, a widespread concern exists about the possibility that the cytoprotective effect of Nrf2 activation may confer drug resistance to cancer cells or at least reduce the efficacy of antitumor agents. In this study, the effect of low ozone concentrations on tamoxifen-treated MCF7 human breast cancer cells has been investigated in vitro by histochemical and molecular techniques. Results demonstrated that cell viability, proliferation and migration were generally similar in tamoxifen-treated cells as in cells concomitantly treated with tamoxifen and ozone. Notably, low ozone concentrations were unable to overstimulate the antioxidant response through the Nfr2 pathway, thus excluding a possible ozone-driven cytoprotective effect that would lead to increased tumor cell survival during the antineoplastic treatment. These findings, though obtained in an in vitro model, support the hypothesis that low ozone concentrations do not interfere with the tamoxifen-induced effects on breast cancer cells.

Background: Increased cancer stem cell (CSC) content and SOX2 overexpression are common features in the development of resistance to therapy in hormone-dependent breast cancer, which remains an important clinical challenge. SOX2 has potential as biomarker of resistance to treatment and as therapeutic target, but targeting transcription factors is also challenging. Here, we examine the potential inhibitory effect of different polyoxometalate (POM) derivatives on SOX2 transcription factor in tamoxifen-resistant breast cancer cells., Methods: Various POM derivatives were synthesised and characterised by infrared spectra, powder X-ray diffraction pattern and nuclear magnetic resonance spectroscopy. Estrogen receptor (ER) positive breast cancer cells, and their counterparts, which have developed resistance to the hormone therapy tamoxifen, were treated with POMs and their consequences assessed by gel retardation and chromatin immunoprecipitation to determine SOX2 binding to DNA. Effects on proliferation, migration, invasion and tumorigenicity were monitored and quantified using microscopy, clone formation, transwell, wound healing assays, flow cytometry and in vivo chick chorioallantoic membrane (CAM) models. Generation of lentiviral stable gene silencing and gene knock-out using CRISPR-Cas9 genome editing were applied to validate the inhibitory effects of the selected POM. Cancer stem cell subpopulations were quantified by mammosphere formation assays, ALDEFLUOR activity and CD44/CD24 stainings. Flow cytometry and western blotting were used to measure reactive oxygen species (ROS) and apoptosis., Results: POMs blocked in vitro binding activity of endogenous SOX2. [P 2 W 18 O 62 ] 6- (PW) Wells-Dawson-type anion was the most effective at inhibiting proliferation in various cell line models of tamoxifen resistance. 10 µM PW also reduced cancer cell migration and invasion, as well as SNAI2 expression levels. Treatment of tamoxifen-resistant cells with PW impaired tumour formation by reducing CSC content, in a SOX2-dependent manner, which led to stem cell depletion in vivo. Mechanistically, PW induced formation of reactive oxygen species (ROS) and inhibited Bcl-2, leading to the death of tamoxifen-resistant cells. PW-treated tamoxifen-resistant cells showed restored sensitivity to tamoxifen., Conclusions: Together, these observations highlight the potential use of PW as a SOX2 inhibitor and the therapeutic relevance of targeting SOX2 to treat tamoxifen-resistant breast cancer., (© 2024. The Author(s).)

In the pentose phosphate pathway, dehydroepiandrosterone (DHEA) uncompetitively inhibits glucose-6-phosphate dehydrogenase (G6PD), reducing NADPH production and increasing oxidative stress, which can influence the onset and/or progression of several diseases, including cancer. 2-Deoxy-D-glucose (2-DG), a glucose mimetic, competes with glucose for cellular uptake, inhibiting glycolysis and competing with glucose-6-phosphate (G-6-P) for G6PD activity. In this study, we report that DHEA-α-2-DG (5), an α-covalent conjugate of DHEA and 2-DG, exhibits better anticancer activity than DHEA, 2-DG, DHEA +2-DG, and polydatin in MCF-7 cells, and reduces NADPH/NADP + ratio in cellular assays. In vitro enzyme kinetics and molecular docking studies showed that 5 uncompetitively inhibits human G6PD activity and binds to the structural NADP + site but not to the catalytic NADP + site. Further combining 5 with the FDA-approved drug tamoxifen enhanced its cytotoxicity against MCF-7 cells, suggesting that it could serve as a candidate for combination of drug strategies., (© 2024 The Author(s). Chemical Biology & Drug Design published by John Wiley & Sons Ltd.)

The cancer-associated alternative splicing (AS) events generate cancer-related transcripts which are involved in uncontrolled cell proliferation and drug resistance. However, the key AS variants implicated in tamoxifen (TAM) resistance in breast cancer remain elusive. In the current study, we investigated the landscape of AS events in nine pairs of primary and relapse breast tumors from patients receiving TAM-based therapy. We unrevealed a notable association between the inclusion of exon 7.2 in the 5'untranslated region (5'UTR) of ALDOA mRNA and TAM resistance. Mechanistically, the inclusion of ALDOA exon 7.2 enhances the translation efficiency of the transcript, resulting in increased ALDOA protein expression, mTOR pathway activity, and the promotion of TAM resistance in breast cancer cells. Moreover, the inclusion of exon 7.2 in ALDOA mRNA is mediated by MSI1 via direct interaction. In addition, elevated inclusion of ALDOA exon 7.2 or expression of MSI1 is associated with an unfavorable prognosis in patients undergoing endocrine therapy. Notably, treatment with Aldometanib, an ALDOA inhibitor, effectively restrains the growth of TAM-resistant breast cancer cells in vitro and in vivo. The present study unveils the pivotal role of an AS event in ALDOA, under the regulation of MSI1, in driving TAM resistance in breast cancer. Therefore, this study provides a promising therapeutic avenue targeting ALDOA to combat TAM resistance., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Background: Resveratrol, a natural compound, may be an alternative to improving conventional breast cancer therapy. Thus, we assessed the capability of resveratrol at a low dose to enhance the in vitro effect of conventional theray in estrogen receptor (ER) and human epidermal growth factor receptor type 2 (HER2)-positive breast cancer cells., Methods: Cell viability of breast cancer cells was measured with neutral red uptake assay. Apoptosis, autophagy, cell cycle progression and cell proliferation were detected through hypotonic fluorescent solution assay, formation of acidic vesicular organelles, flow cytometry, and bromodeoxyuridine assay, respectively. Western blotting was performed to study the expression of pro-apoptotic, anti-apoptotic and autophagic proteins, and estrogen receptors., Results: Resveratrol combined with tamoxifen metabolites or trastuzumab reduced cell viability of ER- and HER2-positive breast cancer cells, respectively. This effect was mainly associated with induction of apoptosis due to a greater formation of hypodiploid nuclei, reduced protein expression of procaspase-7, Bcl-2, Bcl-xL, and PARP; and increased expression of cleaved PARP. Resveratrol decreased the expression of ERα and increased that of ERβ, contributing to the reduced viability on breast cancer cells. Combined treatments induced autophagy, evidenced by increased levels of acidic vesicular organelles and degradation of p62/SQSTM1 protein. Nevertheless, on inhibiting autophagy with 3-methyladenine, cell viability was further reduced and apoptosis was induced, suggesting a pro-survival role of autophagy, impairing apoptosis., Conclusions: Resveratrol increasead the in vitro cytotoxic effect of conventional therapy in breast cancer cells. However, it was necessary to block resveratrol-induced autophagy to improve the therapeutic response., (© 2024. The Author(s), under exclusive licence to The Japanese Breast Cancer Society.)

Background/aim: Interferon-induced trans-membrane protein 1 (IFITM1) is known to be involved in breast cancer progression. We aimed to investigate its role in estrogen receptor (ER)-positive breast cancer cells with wild-type p53 and tamoxifen-resistant breast cancer cells., Materials and Methods: The ER-positive breast cancer cell lines, MCF-7 with wild-type p53 and T47D with mutant p53, were used. We established an MCF-7-derived tamoxifen-resistant cell line (TamR) by long-term culture of MCF-7 cells with 4-hydroxytamoxifen., Results: IFITM1 inhibition in MCF-7 cells significantly decreased cell growth and migration. MCF-7 cells with suppression of IFITM1 using siRNA or ruxolitinib showed reduced cell viability after tamoxifen treatment compared with that in the control MCF-7 cells. Unexpectedly, mRNA and protein levels of IFITM1 were decreased in TamR cells compared with those in MCF-7 cells. TamR cells with suppression of IFITM1 using siRNA or ruxolitinib showed no change in cell viability after treatment with tamoxifen. P53 knockdown using siRNA reduced the mRNA levels of IRF9 and increased mRNA and protein levels of SOCS3 in MCF-7 cells, suggesting that loss or mutation of p53 can affect the induction of IFITM1 via the JAK/STAT signaling pathway in breast cancer. Furthermore, MCF-7 cells with p53 knockdown using siRNA showed no decrease in cell viability after tamoxifen treatment or IFITM1 inhibition, indicating that p53 status may be important for cell death after tamoxifen treatment or IFITM1 inhibition., Conclusion: IFITM1 inhibition may enhance the sensitivity to tamoxifen based on p53-dependent enhancement of IFN signaling in wild-type p53, ER-positive breast cancer cells., (Copyright © 2024, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Post-mitotic, non-proliferative dermal fibroblasts have crucial functions in maintenance and restoration of tissue homeostasis. They are involved in essential processes such as wound healing, pigmentation and hair growth, but also tumor development and aging-associated diseases. These processes are energetically highly demanding and error prone when mitochondrial damage occurs. However, mitochondrial function in fibroblasts and the influence of mitochondrial dysfunction on fibroblast-specific demands are still unclear. To address these questions, we created a mouse model in which accelerated cell-specific mitochondrial DNA (mtDNA) damage accumulates. We crossed mice carrying a dominant-negative mutant of the mitochondrial replicative helicase Twinkle (RosaSTOP system) with mice that express fibroblast-specific Cre Recombinase (Collagen1A2 Cre ERT ) which can be activated by Tamoxifen (Twinkle FIBRO ). Thus, we are able to induce mtDNA deletions and duplications in specific cells, a process which resembles the physiological aging process in humans, where this damage accumulates in all tissues. Upon proliferation in vitro, Tamoxifen induced Twinkle fibroblasts deplete most of their mitochondrial DNA which, although not disturbing the stoichiometry of the respiratory chain complexes, leads to reduced ROS production and mitochondrial membrane potential as well as an anti-inflammatory and anti-fibrotic profile of the cells. In Sodium Azide treated wildtype fibroblasts, without a functioning respiratory chain, we observe the opposite, a rather pro-inflammatory and pro-fibrotic signature. Upon accumulation of mitochondrial DNA mutations in vivo the Twinkle FIBRO mice are protected from fibrosis development induced by intradermal Bleomycin injections. This is due to dampened differentiation of the dermal fibroblasts into α-smooth-muscle-actin positive myofibroblasts in Twinkle FIBRO mice. We thus provide evidence for striking differences of the impact that mtDNA mutations have in contrast to blunted mitochondrial function in dermal fibroblasts and skin homeostasis. These data contribute to improved understanding of mitochondrial function and dysfunction in skin and provide mechanistic insight into potential targets to treat skin fibrosis in the future., (Copyright © 2024. Published by Elsevier B.V.)

Introduction: The current study aimed to investigate the role of probiotic Lactobacillus reuteri for the treatment and prevention of breast cancer., Materials and Methods: Breast cancer was induced by using Cadmium Chloride (Cd) (2 mg/kg) in group II. Tamoxifen was administered to group III. Group IV was treated with Lactobacillus reuteri. Group V was treated with Cd for one month and divided into three subgroups including VA, VB, and VC which were treated with tamoxifen, Lactobacillus reuteri, and tamoxifen + Lactobacillus reuteri, respectively., Results: Significantly higher levels of TNF-α (40.9 ± 4.2 pg/mL), IL-6 (28.0 ± 1.5 pg/mL), IL-10 (60.2 ± 2.0 pg/mL), IFN-γ (60.2 ± 2.0 pg/mL), ALAT (167.2 ± 6.2 U/l), ASAT (451.6 ± 13.9 U/l), and MDA (553.8 ± 19.6 U/l) was observed in Cd group. In comparison, significantly lower levels of TNF-α (18.0 ± 1.1 pg/mL), IL-6 (9.4 ± 0.4 pg/mL), IL-10 (20.8 ± 1.1 pg/mL), IFN-γ (20.8 ± 1.1 pg/mL), ALAT (85.2 ± 3.6 U/l), ASAT (185 ± 6.9 U/l), and MDA (246.0 ± 7.5 U/l) were observed in group Cd + Tam + LR. Liver histopathology of the Cd group showed hemorrhage and ductal aberrations. However, mild inflammation and healthier branched ducts were observed in treatment groups. Furthermore, the renal control group showed normal glomerular tufts, chronic inflammation from the Cd group, and relatively healthier glomerulus with mild inflammation in treatment groups., Conclusion: Hence, the preventive and anticancerous role of probiotic Lactobacillus reuteri is endorsed by the findings of the current study., Competing Interests: Declaration of competing interest The authors declared no conflicts of interest., (Copyright © 2024 Japanese Society of Chemotherapy, Japanese Association for Infectious Diseases, and Japanese Society for Infection Prevention and Control. Published by Elsevier Ltd. All rights reserved.)

Tamoxifen (TAM) is commonly administered to a variety of inducible or conditional transgenic mice that contain Cre recombinase fused with ER. While the impacts of adult TAM treatment are well documented in the field of adipose biology, the long-term effects of postnatal TAM treatment on adult life are still understudied. In this study, we investigated whether postnatal TAM treatment had long-lasting effects on adult body composition and adiposity in male and female mice, fed either with chow or a high-fat diet (HFD). We found that postnatal, but not adult, TAM treatment had long-lasting impacts on female mice, resulting in lower body weight, lower fat mass, and smaller adipocytes. In contrast, postnatal exposure to TAM impaired male but not female cold-induced adipose beiging capacity. Interestingly, upon HFD feeding, the sex-dependent effects of TAM on adult life disappeared, and both female and male mice showed a more obese phenotype with impaired glucose tolerance. These findings suggest that postnatal TAM injection exerts a long-lasting impact on adipose tissue in adult life in a sex- and diet-dependent manner., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Studies have reported overexpression of NAT1 gene for xenobiotic metabolizing arylamine N -acetyltransferase type 1 in estrogen receptor positive breast tumors, and this association has been linked to patient chemoresistance and response to tamoxifen. We probed the expression of NAT1 , using quantitative reverse transcription PCR to screen clinically characterized breast cancer tissue cDNA arrays. Primers detecting all NAT1 alternative transcripts were used, and the protocol and results are reported according to consensus guidelines. The clinical information about 166 tumor samples screened is provided, including tumor stage, estrogen and progesterone receptor status and HER2 expression. NAT1 was found to be significantly ( P  < 0.001) upregulated in hormone receptor positive vs. negative tumors. No correlation was apparent between NAT1 and tumor stage or HER2 expression. Our findings demonstrate a strong correlation between the expression of NAT1 and steroid hormone receptors in breast tumors, supporting its possible utility as a pharmacogenetic biomarker or drug target. Of the two polymorphic NAT genes, NAT1 is the one primarily expressed in breast tissue, and is subjected to regulation by two differential promoters and more than one polyadenylation signal. Hormonal factors may enhance NAT1 gene expression at the transcriptional or epigenetic level, and tamoxifen has additionally been shown to inhibit NAT1 enzymatic activity. The outcome of tamoxifen treatment is also more favorable in patients with NAT1 overexpressing tumors. The study adds to the growing body of evidence implicating NAT1 in breast cancer and its pharmacological treatment., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

The cholesterogenic phenotype, encompassing de novo biosynthesis and accumulation of cholesterol, aids cancer cell proliferation and survival. Previously, the role of cholesteryl ester (CE) transfer protein (CETP) has been implicated in breast cancer aggressiveness, but the molecular basis of this observation is not clearly understood, which this study aims to elucidate. CETP knock-down resulted in a >50% decrease in cell proliferation in both 'estrogen receptor-positive' (ER+; Michigan Cancer Foundation-7 (MCF7) breast cancer cells) and 'triple-negative' breast cancer (TNBC; MDA-MB-231) cell lines. Intriguingly, the abrogation of CETP together with the combination treatment of tamoxifen (5 μM) and acetyl plumbagin (a cholesterol-depleting agent) (5 μM) resulted in twofold to threefold increase in apoptosis in both cell lines. CETP knockdown also showed decreased intracellular CE levels, lipid raft and lipid droplets in both cell lines. In addition, RT 2 Profiler PCR array (Qiagen, Germany)-based gene expression analysis revealed an overall downregulation of genes associated in cholesterol biosynthesis, lipid signalling and drug resistance in MCF7 cells post-CETP knock-down. On the contrary, resistance in MDA-MB-231 cells was reduced through increased expression in cholesterol efflux genes and the expression of targetable surface receptors by endocrine therapy. The pilot xenograft mice study substantiated CETP's role as a cancer survival gene as knock-down of CETP stunted the growth of TNBC tumour by 86%. The principal findings of this study potentiate CETP as a driver in breast cancer growth and aggressiveness and thus targeting CETP could limit drug resistance via the reduction in cholesterol accumulation in breast cancer cells, thereby reducing cancer aggressiveness., (© 2024 The Authors. IUBMB Life published by Wiley Periodicals LLC on behalf of International Union of Biochemistry and Molecular Biology.)

Metabolic dysfunction-associated steatohepatitis (MASH) is a chronic liver disorder marked by hepatic fat accumulation and inflammatory infiltrates which may evolve to cirrhosis. Clinical studies have demonstrated the higher risk of MASH development after tamoxifen (TAM) therapy, especially in obese patients. Therefore, we aimed to evaluate MASH induction by TAM combined with high fat diet (HFD) and the potential interference of memantine (MEMA) with MASH progression via modulation of SIRT6 and its related signaling pathways. MASH was induced in female Wistar rats by co-administration of TAM (25 mg/kg/day, p.o.) and HFD for 5 weeks. Liver function biomarkers, tissue triglyceride and cholesterol, MASH scoring, SIRT6 with its related signals, and lipid synthesis/oxidation markers were estimated. By comparison to MASH group, MEMA improved liver function indices (ALT, AST, ALP, albumin) and reduced the progression of MASH, evidenced by decreased accumulation of lipids in hepatic tissue, improved histological features, and reduced MASH scoring. MEMA enhanced hepatic SIRT6 and downregulated p-AKT/mTOR signaling, that subsequently reduced expressions of the lipid synthesis biomarkers (SREBP1c, SCD), while elevating the lipid oxidation markers (PPAR-α, CPT1). Moreover, MEMA enhanced NRF2/HO-1 signaling, with subsequently improved antioxidant defense and pro-inflammatory/anti-inflammatory cytokines balance. Analysis of SIRT6 correlations with p-AKT/mTOR, NRF2/HO-1, SREBP1c, and PPAR-α further confirmed our results. Consequently, we conclude that MEMA could interfere with MASH progression, at least in part, via enhanced SIRT6 expression and modulation of its related p-AKT/mTOR and NRF2/HO-1 signaling pathways, eventually reducing liver steatosis and inflammation. That could be a promising therapeutic modality for curbing MASH progression., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The discovery of adult-born granule cells (aDGCs) in the dentate gyrus of the hippocampus has raised questions regarding how they develop, incorporate into the hippocampal circuitry, and contribute to learning and memory. Here, we used patch-clamp electrophysiology to investigate the intrinsic and synaptic excitability of mouse aDGCs as they matured, enabled by using a tamoxifen-induced genetic label to birth date the aDGCs at different animal ages. Importantly, we also undertook immunofluorescence studies of the expression of the immediate early gene Egr1 and compared these findings with the electrophysiology data in the same animals. We examined two groups of animals, with aDGC birthdating when the mice were 2 months and at 7-9 months of age. In both groups, cells 4 weeks old had lower thresholds for current-evoked action potentials than older cells but fired fewer spikes during long current pulses and responded more poorly to synaptic activation. aDGCs born in both 2 and 7-9-month-old mice matured in their intrinsic excitability and synaptic properties from 4-12 weeks postgenesis, but this occurred more slowly for the older age animals. Interestingly, this pattern of intrinsic excitability changes did not correlate with the pattern of Egr1 expression. Instead, the development of Egr1 expression was correlated with the frequency of spontaneous excitatory postsynaptic currents. These results suggest that in order for aDGCs to fully participate in hippocampal circuitry, as indicated by Egr1 expression, they must have developed enough synaptic input, in spite of the greater input resistance and reduced firing threshold that characterizes young aDGCs., (© 2024 The Author(s). Hippocampus published by Wiley Periodicals LLC.)

Objective: Tamoxifen is the most used agent to treat estrogen receptor-positive (ER+) breast cancer (BC). While it decreases the risk of cancer recurrence by 50%, many patients develop resistance to this treatment, culminating in highly aggressive disease. Tamoxifen resistance comes from the repression of ER transcriptional activity that switches the cancer cells to proliferation via nonhormonal signaling pathways. Here, we evaluate a potential strategy to overcome tamoxifen resistance by focused ultrasound (FUS), a noninvasive approach for the mechanical excitation of cancer cells., Methods: Resistant and nonresistant ER+ BC cells and xenografts from patients with ER+ BC were treated with tamoxifen, FUS or their combination. The apoptosis, proliferation rate, gene expression and activity of estrogen receptor, and morphological changes were measured in treated cells and tissues., Results: FUS caused the mechanical disruption of tamoxifen-resistant BC cells that in turn led to the upregulation of ERα-encoding gene expression and long-term re-sensitization of the cells to tamoxifen. Patient-derived xenografts treated with Tamoxifen and FUS demonstrated a significant reduction in tumor viability and proliferation and a strong structural damage to tumor cells and extracellular matrix., Conclusion: FUS can improve ER+ BC treatment by re-sensitizing the cancer cells to tamoxifen., Competing Interests: Conflict of interest The authors have no relevant financial or non-financial interests to disclose., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Breast cancer is the most prevalent cancer in women globally. Over-activated estrogen receptor (ER) α signaling is considered the main factor in luminal breast cancers, which can be effectively managed with selective estrogen receptor modulators (SERMs) like tamoxifen. However, approximately 30-40% of ER + breast cancer cases are recurrent after tamoxifen therapy. This implies that the treatment of breast cancer is still hindered by resistance to tamoxifen. Recent studies have suggested that post-translational modifications of ERα play a significant role in endocrine resistance. The stability of both ERα protein and its transcriptome is regulated by a balance between E3 ubiquitin ligases and deubiquitinases. According to the current knowledge, approximately 100 deubiquitinases are encoded in the human genome, but it remains unclear which deubiquitinases play a critical role in estrogen signaling and endocrine resistance. Thus, decoding the key deubiquitinases that significantly impact estrogen signaling, including the control of ERα expression and stability, is critical for the improvement of breast cancer therapeutics., Methods: We used several ER positive breast cancer cell lines, DUB siRNA library screening, xenograft models, endocrine-resistant (ERα-Y537S) model and performed immunoblotting, real time PCR, RNA sequencing, immunofluorescence, and luciferase activity assay to investigate the function of USP36 in breast cancer progression and tamoxifen resistance., Results: In this study, we identify Ubiquitin-specific peptidase 36 (USP36) as a key deubiquitinase involved in ERα signaling and the advancement of breast cancer by deubiquitinases siRNA library screening. In vitro and in vivo studies showed that USP36, but not its catalytically inactive mutant (C131A), could promote breast cancer progression through ERα signaling. Conversely, silencing USP36 inhibited tumorigenesis. In models resistant to endocrine therapy, silencing USP36 destabilized the resistant form of ERα (Y537S) and restored sensitivity to tamoxifen. Molecular studies indicated that USP36 inhibited K48-linked polyubiquitination of ERα and enhanced the ERα transcriptome. It is interesting to note that our results suggest USP36 as a novel biomarker for treatment of breast cancer., Conclusion: Our study revealed the possibility that inhibiting USP36 combined with tamoxifen could provide a potential therapy for breast cancer., (© 2024. The Author(s).)

Objective: Estrogen receptor-positive (ER+) breast cancer represents about 80% of cases, tamoxifen is the election neoadjuvant chemotherapy. However, a large percentage of patients develop chemoresistance, compromising recovery. Clinical evidence suggests that high plasmatic levels of low-density lipoproteins (LDL) could promote cancer progression. The present study analyzed the effect of LDL on the primary plasmatic active Tamoxifen's metabolites resistance acquisition, 4-hydroxytamoxifen (4OH-Tam) and 4-hydroxy-N-desmethyl-tamoxifen (endoxifen), in breast cancer ERα + cells (MCF-7)., Methods: Two resistant cellular variants, MCF-7Var-H and MCF-7Var-I, were generated by a novel strategy and their phenotype features were evaluated. Phenotypic assessment was performed by MTT assays, cytometry, immunofluorescence microscopy, zymography and protein expression analysis., Results: MCF-7Var-H, generated only with tamoxifen metabolites, showed a critical down-regulation in hormone receptors, augmented migration capacity, metalloprotease 9 extracellular medium excretion, and a mesenchymal morphology in contrast with native MCF-7, suggesting the transition towards Triple-negative breast cancer (TNBC) phenotype. In contrast, MCF-7Var-I which was generated in a high LDL media, showed only a slight upregulation in ER and other less noticeable metabolic adaptations. Results suggest a potential role of transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) in phenotypic differences observed among variants., Conclusion: LDL high or low concentrations during Tamoxifen´s metabolites chemoresistance acquisition leads to different cellular mechanisms related to chemoresistance. A novel adaptative cellular response associated with Nrf2 activity could be implicated., (© 2024 The Author(s).)

The clinical studies for breast cancer (BC) are now assessing the efficacy of 2-Methoxyestradiol (2-ME), a naturally occurring derivative of estradiol. Our study aimed to explore the potential of combining the 2-ME and tamoxifen (TAM) on sensitization of TAM-resistant cells using LCC2 the TAM-resistant cells as a model and comparing the results to the sensitive cells MCF-7. Sulphorhodamine-B (SRB) assay is used to examine the 2-ME chemo-sensitizing impact on the cytotoxicity of TAM on LCC2 cells. Colorimetric assay kits were used to assess the level of the apoptosis-related markers caspases 3, Bcl2, and Bax in cell lysate. Hypoxia-inducible factor 1 alpha (HIF-1α) expression was measured using western blotting. Total cholesterol and triglyceride (TG) levels were examined colorimetrically, using the BIOLABO kit. The use of 2-ME enhanced the cytotoxic effects of TAM and effectively reversed TAM resistance. This was achieved by inhibiting the expression of HIF-1α, while concurrently increasing the levels of apoptotic marker caspase-3, as well as the pro-apoptotic protein Bax. Additionally, there was a reduction in the levels of Bcl2, an anti-apoptotic protein. Furthermore, a reduction in TG and cholesterol levels was noted. Our findings show that HIF-1α plays an important role in TAM resistance and that suppression of HIF-1α by 2-ME-mediated sensitization of BC-resistant cells to TAM. Therefore, the concurrent administration of TAM/2-ME might potentially serve as a viable therapeutic approach to address TAM resistance and enhance the overall therapy efficacy for patients with BC., (© 2024. The Author(s).)

Luminal breast cancer has a high incidence worldwide and poses a severe health threat. Estrogen receptor alpha (ER-α) is activated by 17β-estradiol (E2), and its overexpression promotes cancerous characteristics. Luminal breast cancer is an epithelial type; however, the cytokine IL-6, secreted by cells within the tumor microenvironment, stimulates the epithelial-to-mesenchymal transition (EMT) and promotes metastasis. Also, IL-6 decreases ER-α levels, favoring the tamoxifen (TMX) resistance development. However, genes under E2 regulation continue to be expressed even though this receptor is absent. GPR30 is an alternative E2 receptor present in both luminal and aggressive triple-negative breast cancer and is related to TMX resistance and cancer progression. The roles of GPR30 and IL-6 in metastasis have been individually established; however, their interplay remains unexplored. This study aims to elucidate the role of GPR30 in IL-6-induced metastatic properties of MCF-7 luminal breast cancer cells. Results showed that GPR30 contributes to the E2-induced MCF-7 proliferation because its inhibition with the antagonist G15 and the Pertussis toxin (PTX) reduced it. Besides, GPR30 upregulated vimentin and downregulated E-cadherin levels in MCF-7 and TMX-resistant (R-TMX) cells and is also involved in the IL-6-induced migration, invasion, and TMX resistance in MCF-7 cells. In addition, in MDA-MB-231 triple-negative cells, both basal and IL-6-induced metastatic properties were related to GPR30 activity. These results indicate that the GPR30 receptor regulates the EMT induced by IL-6 in breast cancer cells.

Tamoxifen, a selective estrogen receptor modulator (SERM), exhibits dual agonist or antagonist effects contingent upon its binding to either G-protein-coupled estrogen receptor (GPER) or estrogen nuclear receptor (ESR). Estrogen signaling plays a pivotal role in initiating epigenetic alterations and regulating estrogen-responsive genes in breast cancer. Employing three distinct breast cancer cell lines-MCF-7 (ESR+; GPER+), MDA-MB-231 (ESR-; GPER-), and SkBr3 (ESR-; GPER+)-this study subjected them to treatment with two tamoxifen derivatives: 4-hydroxytamoxifen (4-HT) and endoxifen (Endox). Through 2D high-performance liquid chromatography with tandem mass spectrometry detection (HPLC-MS/MS), varying levels of 5-methylcytosine (5-mC) were found, with MCF-7 displaying the highest levels. Furthermore, TET3 mRNA expression levels varied among the cell lines, with MCF-7 exhibiting the lowest expression. Notably, treatment with 4-HT induced significant changes in TET3 expression across all cell lines, with the most pronounced increase seen in MCF-7 and the least in MDA-MB-231. These findings underscore the influence of tamoxifen derivatives on DNA methylation patterns, particularly through modulating TET3 expression, which appears to be contingent on the presence of estrogen receptors. This study highlights the potential of targeting epigenetic modifications for personalized anti-cancer therapy, offering a novel avenue to improve treatment outcomes.

Breast cancer (BC) remains the second leading cause of cancer-related mortalities in women. Resistance to hormone therapies such as tamoxifen, an estrogen receptor (ER) inhibitor, is a major hurdle in the treatment of BC. Enhancer of zeste homolog 2 (EZH2), the methyltransferase component of the Polycomb repressive complex 2 (PRC2), has been implicated in tamoxifen resistance. Evidence suggests that EZH2 often functions noncanonically, in a methyltransferase-independent manner, as a transcription coactivator through interacting with oncogenic transcription factors. Unlike methyltransferase inhibitors, proteolysis targeting chimeras (PROTAC) can suppress both activating and repressive functions of EZH2. Here, we find that EZH2 PROTACs, MS177 and MS8815, effectively inhibited the growth of BC cells, including those with acquired tamoxifen resistance, to a much greater degree when compared to methyltransferase inhibitors. Mechanistically, EZH2 associates with forkhead box M1 (FOXM1) and binds to the promoters of FOXM1 target genes. EZH2 PROTACs induce degradation of both EZH2 and FOXM1, leading to reduced expression of target genes involved in cell cycle progression and tamoxifen resistance. Together, this study supports that EZH2-targeted PROTACs represent a promising avenue of research for the future treatment of BC, including in the setting of tamoxifen resistance., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Tamoxifen (TAM) is a classical anti-estrogenic drug that antagonizes estrogen by competitively binding to estrogen receptor α (ERα). However, drug resistance to TAM remains a significant challenge in breast cancer treatment. In this study, we aimed to design an actively targeted drug delivery system to enhance the proliferation inhibitory effects of TAM on ER positive breast cancer cells. Herein, chitosan (CS) was modified with genistein (GEN) to obtain the actively targeted GEN-CS. The TAM-loaded nanoparticles (TAM-GEN-CS-NPs) were constructed using an ionic-crosslinking method, with GEN-CS as the carrier material and sodium tripolyphosphate (TPP) as the crosslinking agent. As a result, TAM-GEN-CS-NPs exhibited a spherical morphology with an average size of 299.8 nm. The encapsulation efficiency and drug loading content were 85.77% and 14.13 µg/mg, respectively. Compared with free TAM, TAM-GEN-CS-NPs displayed obvious slow-release performance. In vitro cellular assays demonstrated that TAM-GEN-CS-NPs had active targeting and proliferation inhibitory effects on MCF-7 cells. The IC 50 of TAM and TAM-GEN-CS-NPs were 10.25 µg/mL and 7.22 µg/mL, respectively. More importantly, the combination index (CI) value of TAM and GEN was less than 1, indicating synergistic effects. Therefore, TAM-GEN-CS-NPs hold the potential to enhance TAM therapy for breast cancer through active targeting and synergistic treatment strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 American Pharmacists Association. Published by Elsevier Inc. All rights reserved.)

Background: Ovarian cancer is a malignant tumor of the female reproductive system, and its mortality rate is as high as 70%. Estrogen receptor α (ERα)-positive ovarian cancer accounted for most of all ovarian cancer patients. ERα can promote the growth and proliferation of tumors., Methods: The combined effect of All-trans retinoic acid (ATRA) and tamoxifen was obtained by the combination screening of tamoxifen and compound library by MTS. In addition, colony formation assay, flow cytometry analysis, immunofluorescence staining, quantitative real-time polymerase chain reaction (PCR), western blot, and tumor xenotransplantation models were used to further evaluate the efficacy of tamoxifen and ATRA in vitro and in vivo for ER-α-positive ovarian cancer., Results: In our study, we found that All-trans retinoic acid (ATRA) can cooperate with tamoxifen to cause cell cycle arrest and apoptosis and inhibit ERα-positive ovarian cancer in vivo and in vitro. Further exploration of the mechanism found that ATRA can Inhibit genes related to the ERα signaling pathway, enhance the sensitivity of ERα-positive ovarian cancer cells to tamoxifen, and ascertain the effectiveness of tamoxifen and ATRA as treatments for ovarian cancer with an ERα-positive status., Conclusion: Combination of ATRA and tamoxifen is a new way for the treatment of ERα-positive ovarian cancer., (© 2024. The Author(s).)

Receptors are proteinous macromolecules which remain in the apo form under normal/unliganded conditions. As the ligand approaches, there are specific stereo-chemical changes in the apo form of the receptor as per the stereochemistry of a ligand. Accordingly, a series of substituted dimethyl-chroman-based stereochemically flexible and constrained Tamoxifen analogs were synthesized as anti-breast cancer agents. The synthesized compounds 19a-e, 20a-e, 21, and 22a-e, showed significant antiproliferative activity against estrogen receptor-positive (ER + , MCF-7) and negative (ER - , MDA MB-231) cells within IC 50 value 8.5-25.0 µM. Amongst all, four potential molecules viz 19b, 19e, 22a, and 22c, were evaluated for their effect on the cell division cycle and apoptosis of ER + and ER - cancer cells (MCF-7 & MDA MB-231cells), which showed that these compounds possessed antiproliferative activity through triggering apoptosis. In-silico docking experiments elucidated the possible affinity of compounds with estrogen receptors-α and -β., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)