Tamoxifen as the first targeted long-term adjuvant therapy for breast cancer

Development of new steroid-based hydrazide and (thio)semicarbazone compounds with anticancer properties

Most breast and prostate cancers are caused by abnormal production or action of steroidal hormones. Hormonal drugs based on steroid scaffolds represent a significant class of chemotherapeutics that are routinely used in chemotherapy. In this study, the synthesis of new 17a-homo lactone and 17α-(pyridine-2-ylmethyl) androstane derivatives with hydrazide and semicarbazone motifs is presented. All compounds were screened for their effect on cell viability against a panel of five cancer cell lines and one healthy cell line. Two compounds showed significant cytotoxicity against cancer cells, with low toxicity against healthy cells. The relative binding affinities of compounds for the ligand-binding domains of estrogen receptor α, estrogen receptor β, androgen receptor and glucocorticoid receptor were tested using a fluorescence screen in yeast. Potential for inhibition of aldo-keto reductase 1C3 and 1C4 activity was measured in vitro. Experimental results are analyzed in the context of molecular docking simulations. Our results could help guide design of steroid compounds with improved anticancer properties against androgen- and estrogen-dependent cancers.

Targeting aberrant fatty acid synthesis and storage in endocrine resistant breast cancer cells

Background

Lipid metabolic reprogramming is an emerging characteristic of endocrine therapy (ET) resistance in estrogen receptor-positive (ER+) breast cancer. We explored changes in lipid metabolism in ER+ breast cancer cell lines following acquired resistance to common endocrine treatments and tested efficacy of an inhibitor in current clinical trials.

Methods

We derived ER+ breast cancer cell lines resistant to Tamoxifen (TamR), Fulvestrant (FulvR), and long-term estrogen withdrawal (EWD). Parental and ET resistant cells were subjected to global gene expression and unbiased lipidomic profiling. Lipid storage changes were assessed via neutral lipid staining with Oil Red O (ORO). The impact of the fatty acid synthase (FASN) inhibitor TVB-2640 on the growth and lipid storage of these cell lines was evaluated. Additionally, 13 C 2 -acetate tracing was used to examine FASN activity in parental and ET resistant cells in the absence or presence of TVB-2640.

Results

Compared to parental cells, lipid metabolism and processing pathways were notably enriched in ET resistant cells, which exhibited distinct lipidomes characterized by increased triglyceride and polyunsaturated FA (PUFA) species. ET-resistant cells displayed enhanced cytoplasmic lipid droplets. Increased FASN protein levels were observed in ET-resistant cells, and TVB-2640 effectively inhibited FASN activity. FASN inhibition reduced cell growth in some but not all cell lines and ET resistance types and did not correlate to lipid storage reduction. 13 C 2 -acetate tracing confirmed reduced palmitate synthesis and enhanced PUFA synthesis in ET-resistant cells, especially when combined with FulvR.

Conclusion

ET resistant breast cancer cells exhibit a shift towards enhanced triglyceride storage and complex lipids enriched with PUFA acyl chains. While targeting FASN alongside ET may not fully overcome ET resistance in our models, focusing on the unique lipid metabolic dependencies, such as PUFA pathways, may present a promising alternative strategy for treating ET resistant breast cancer.

A computational study of potent series of selective estrogen receptor degraders for breast cancer therapy

A detailed multistep framework combining quantitative structure-activity relationship, global reactivity, absorption, distribution, metabolism and elimination properties, molecular docking and molecular dynamics simulation (MD) on a series of Selective Estrogen Receptor Down-Regulators (SERDs) interacting with Estrogen Receptor α (ERα) has been performed. The partial least squares regression method derived an empirical model with better predictive capability. The results of global reactivity descriptors revealed that all the compounds are considered strong electrophiles, allowing them to participate in polar reactions more easily. The Brain Or IntestinaL EstimateD permeation diagram revealed that compounds 49 and 31 were predicted to be well absorbed by the human gastrointestinal tract and would not enter the brain. The elucidation of the binding mode between the most active compounds that comply with Lipinski's and Veber's rules from the dataset and ERα targets was explored by molecular docking. The MD simulations were performed for 100 ns on the best compounds, which indicated their stability state under dynamics simulations. These findings are expected to help predict the anticancer activities of the studied SERD compounds and better understand their binding mechanism with ERα targets.Communicated by Ramaswamy H. Sarma.

Molecular Action of Tamoxifen in the Ovaries of Rats with Mammary Neoplasia

Tamoxifen (TAM) is a drug commonly used in patients with breast cancer. The anticancer effect of TAM occurs via its ability to antagonize estrogen-dependent growth of mammary epithelial cells. Previously, we demonstrated that TAM prevented the chemotherapy-induced loss of ovarian follicular reserves in both cancer-free rats and rats with cancer. Such follicular loss is a main cause of infertility in young women treated for cancer. The current study was undertaken to discover the molecules and intracellular pathways involved in the action of TAM in the ovaries of rats with mammary tumors. To meet this goal we used transcriptomic (RNA-Seq) and proteomic (2D-DIGE/MS) approaches. TAM inhibited the expression of genes and lncRNAs involved in ovarian steroidogenesis. Moreover, TAM altered the expression of genes related to primordial follicle activation or arrest. In addition, proteomic screening indicated the importance of basic metabolic processes in the ovarian actions of TAM. Although simple extrapolation of these data to humans is not possible, the results of this study emphasize the need to explore the ability of TAM to affect ovarian function in women undergoing cancer treatment.

Tamoxifen as a modulator of CXCL12-CXCR4-CXCR7 chemokine axis: A breast cancer and glioblastoma view

The chemokine stromal cell-derived-factor 1 (SDF)-1/CXCL12 acts by binding to its receptors, the CXC-4 chemokine receptor (CXCR4) and the CXC-7 chemokine receptor (CXCR7). The binding of CXCL12 to its receptors results in downstream signaling that leads to cell survival, proliferation and migration of tumor cells. CXCL12 and CXCR4 are highly expressed in breast cancer (BC) and glioblastoma (GBM) compared to normal cells. High expression of this chemokine axis correlates with increased therapy resistance and grade, tumor spread and poorer prognosis in these tumors. Tamoxifen (TMX) is a selective estrogen receptor modulator (SERM) that inhibits the expression of estrogen-regulated genes, including growth and angiogenic factors secreted by tumor cells. Additionally, TMX targets several proteins, such as protein kinase C (PKC), phospholipase C (PLC), P-glycoprotein (PgP), phosphatidylinositol-3-kinase (PI3K) and ion channels. This drug showed promising antitumor activity against both BC and GBM cells. In this review, we discuss the role of the CXCL12-CXCR4-CXCR7 chemokine axis in BC and GBM tumor biology and propose TMX as a potential modulator of this axis in these tumors. TMX modulates the CXCL12-CXCR4-CXCR7 axis in BC, however, there are no studies on this in GBM. We propose that studying this axis in GBM cells/patients treated with TMX might be beneficial for these patients. TMX inhibits important signaling pathways in these tumors and the activation of this chemokine axis is associated with increased therapy resistance.

Natural compounds targeting nuclear receptors for effective cancer therapy

Human nuclear receptors (NRs) are a family of forty-eight transcription factors that modulate gene expression both spatially and temporally. Numerous biochemical, physiological, and pathological processes including cell survival, proliferation, differentiation, metabolism, immune modulation, development, reproduction, and aging are extensively orchestrated by different NRs. The involvement of dysregulated NRs and NR-mediated signaling pathways in driving cancer cell hallmarks has been thoroughly investigated. Targeting NRs has been one of the major focuses of drug development strategies for cancer interventions. Interestingly, rapid progress in molecular biology and drug screening reveals that the naturally occurring compounds are promising modern oncology drugs which are free of potentially inevitable repercussions that are associated with synthetic compounds. Therefore, the purpose of this review is to draw our attention to the potential therapeutic effects of various classes of natural compounds that target NRs such as phytochemicals, dietary components, venom constituents, royal jelly-derived compounds, and microbial derivatives in the establishment of novel and safe medications for cancer treatment. This review also emphasizes molecular mechanisms and signaling pathways that are leveraged to promote the anti-cancer effects of these natural compounds. We have also critically reviewed and assessed the advantages and limitations of current preclinical and clinical studies on this subject for cancer prophylaxis. This might subsequently pave the way for new paradigms in the discovery of drugs that target specific cancer types.

Research progress on tamoxifen and its analogs associated with nuclear receptors

Tamoxifen, a triphenylethylene-based selective estrogen-receptor modulator, is a landmark drug for the treatment of breast cancer and is also used for treating liver cancer and osteoporosis. Structural studies of tamoxifen have led to the synthesis of more than 20 novel tamoxifen analogs as receptor modulators, including 16 ERα modulators 2-17, an ERRβ inverse agonist 19 and six ERRγ inverse agonists 20-25. This paper summarizes the research progress and structure-activity relationships of tamoxifen analogs modulating these three nuclear receptors reported in the literature, and introduces the relationship between these three nuclear receptor-mediated diseases and tamoxifen analogs to guide the research of novel tamoxifen analogs.

Early increase in tamoxifen dose in CYP2D6 poor metaboliser breast cancer patients and survival: A propensity score matching analysis

PURPOSE

Tamoxifen is a drug used for hormone receptor-positive breast cancers, primarily metabolised by the CYP2D6 enzyme into active metabolites such as endoxifen. CYP2D6 displays varying degrees of activity depending on its genotype. This study aims to analyse the effect of an early increase in tamoxifen dose in poor metabolisers (PM) on survival.

METHODS

We enrolled 220 patients diagnosed with breast cancer who were treated with tamoxifen. CYP2D6 polymorphisms were determined, and the phenotype was estimated according to the Clinical Pharmacogenetics Implementation Consortium. Disease-free survival (DFS) and overall survival (OS) were analysed considering the entire patient group, and a subgroup of 110 patients selected by Propensity Score Matching (PSM). All women were treated with 20 mg/day of tamoxifen for 5 years, except PM, who initially received 20 mg/day for 4 months, followed by 40 mg/day for 4 months and 60 mg/day for 4 months before returning to the standard dose of 20 mg/day until completing 5 years of treatment.

RESULTS

The analysis of the influence of CYP2D6 polymorphisms in the complete group and in the PSM subgroup revealed no significant differences for DFS or OS. Furthermore, DFS and OS were analysed in relation to various covariates such as age, histological grade, nodal status, tumour size, HER-2, Ki-67, chemotherapy, and radiotherapy. Only age, histological grade, nodal status, and chemotherapy treatment demonstrated statistical significance.

CONCLUSION

An early increase in tamoxifen dose in PM patients is not associated with survival differences among CYP2D6 phenotypes.

The crosstalk between ubiquitination and endocrine therapy

Endocrine therapy (ET), also known as hormone therapy, refers to the treatment of tumors by regulating and changing the endocrine environment and hormone levels. Its related mechanism is mainly through reducing hormone levels and blocking the binding of hormones to corresponding receptors, thus blocking the signal transduction pathway to stimulate tumor growth. However, with the application of ET, some patients show resistance to ET, which is attributed to abnormal accumulation of hormone receptors (HRs) and the production of multiple mutants of HRs. The targeted degradation of abnormal accumulation protein mediated by ubiquitination is an important approach that regulates the protein level and function of intracellular proteins in eukaryotes. Here, we provide a brief description of the traditional and novel drugs available for ET in this review. Then, we introduce the link between ubiquitination and ET. In the end, we elaborate the clinical application of ET combined with ubiquitination-related molecules. KEY MESSAGES: • A brief description of the traditional and novel drugs available for endocrine therapy (ET). • The link between ubiquitination and ET. • The clinical application of ET combined with ubiquitination-related molecules.

Design, synthesis and biological evaluation of fluorinated selective estrogen receptor degraders (FSERDs) - A promising strategy for advanced ER positive breast cancer

Although endocrine therapies involving pharmaceuticals, such as tamoxifen and aromatase inhibitors, had initially demonstrated good responses in patients with estrogen receptor-positive (ER+) breast cancer, they often led to drug resistance. ER plays a vital role in the progression of metastatic diseases. Fulvestrant, a first generation selective estrogen receptor degrader (SERD), can effectively downregulate the ER protein and inhibit its downstream signaling pathways. However, as the drug needs to be intramuscularly injected, its widespread use is limited owing to poor patient compliance. Herein, we described a novel class of orally bioavailable fluorine-substituted SERDs that exhibit improved pharmacokinetic profiles. We substituted the hydroxyl group of clinical SERD candidate 6 with a fluorine atom to diminish phase II metabolism. The subsequent structure-activity relationship (SAR) investigation identified 22h and 27b, which can effectively degrade ER in a dose-dependent manner and exhibit considerable antiproliferative potency and efficacy in vitro and in vivo. The excellent pharmacokinetic profiles of 27b render it promising candidate of clinically useful oral SERD.

Vanillin-Based Indolin-2-one Derivative Bearing a Pyridyl Moiety as a Promising Anti-Breast Cancer Agent via Anti-Estrogenic Activity

The structure-based design introduced indoles as an essential motif in designing new selective estrogen receptor modulators employed for treating breast cancer. Therefore, here, a series of synthesized vanillin-substituted indolin-2-ones were screened against the NCI-60 cancer cell panel followed by in vivo, in vitro, and in silico studies. Physicochemical parameters were evaluated with HPLC and SwissADME tools. The compounds demonstrated promising anti-cancer activity for the MCF-7 breast cancer cell line (GI = 6-63%). The compound with the highest activity (6j) was selective for the MCF-7 breast cancer cell line (IC₅₀ = 17.01 μM) with no effect on the MCF-12A normal breast cell line supported by real-time cell analysis. A morphological examination of the used cell lines confirmed a cytostatic effect of compound 6j. It inhibited both in vivo and in vitro estrogenic activity, triggering a 38% reduction in uterine weight induced by estrogen in an immature rat model and hindering 62% of ER-α receptors in in vitro settings. In silico molecular docking and molecular dynamics simulation studies supported the stability of the ER-α and compound 6j protein-ligand complex. Herein, we report that indolin-2-one derivative 6j is a promising lead compound for further pharmaceutical formulations as a potential anti-breast cancer drug.

Association of the Estrogen Receptor 1 Polymorphisms rs2046210 and rs9383590 with the Risk, Age at Onset and Prognosis of Breast Cancer

Estrogen receptor α (ERα), encoded by the ESR1 gene, is a key prognostic and predictive biomarker firmly established in routine diagnostics and as a therapeutic target of breast cancer, and it has a central function in breast cancer biology. Genetic variants at 6q25.1, containing the ESR1 gene, were found to be associated with breast cancer susceptibility. The rs2046210 and rs9383590 single nucleotide variants (SNVs) are located in the same putative enhancer region upstream of ESR1 and were separately identified as candidate causal variants responsible for these associations. Here, both SNVs were genotyped in a hospital-based case-control study of 409 female breast cancer patients and 422 female controls of a Central European (Austrian) study population. We analyzed the association of both SNVs with the risk, age at onset, clinically and molecularly relevant characteristics and prognosis of breast cancer. We also assessed the concordances between both SNVs and the associations of each SNV conditional on the other SNV. The minor alleles of both SNVs were found to be non-significantly associated with an increased breast cancer risk. Significant associations were found in specific subpopulations, particularly in patients with an age younger than 55 years. The minor homozygotes of rs2046210 and the minor homozygotes plus heterozygotes of rs9383590 exhibited a several-years-younger age at onset than the common homozygotes, which was more pronounced in ER-positive and luminal patients. Importantly, the observed associations of each SNV were not consistently nullified upon correction for the other SNV nor upon analyses in common homozygotes for the other SNV. We conclude that both SNVs remain independent candidate causal variants.

Glutamine synthetase regulates the immune microenvironment and cancer development through the inflammatory pathway

Although adjuvant tamoxifen therapy is beneficial to estrogen receptor-positive (ER⁺) breast cancer patients, a significant number of patients still develop metastasis or undergo recurrence. Therefore, identifying novel diagnostic and prognostic biomarkers for these patients is urgently needed. Predictive markers and therapeutic strategies for tamoxifen-resistant ER⁺ breast cancer are not clear, and micro (mi)RNAs have recently become a focal research point in cancer studies owing to their regulation of gene expressions, metabolism, and many other physiological processes. Therefore, systematic investigation is required to understand the modulation of gene expression in tamoxifen-resistant patients. High-throughput technology uses a holistic approach to observe differences among expression profiles of thousands of genes, which provides a comprehensive level to extensively investigate functional genomics and biological processes. Through a bioinformatics analysis, we revealed that glutamine synthetase/glutamate-ammonia ligase (GLUL) might play essential roles in the recurrence of tamoxifen-resistant ER⁺ patients. GLUL increases intracellular glutamine usage via glutaminolysis, and further active metabolism-related downstream molecules in cancer cell. However, how GLUL regulates the tumor microenvironment for tamoxifen-resistant ER⁺ breast cancer remains unexplored. Analysis of MetaCore pathway database demonstrated that GLUL is involved in the cell cycle, immune response, interleukin (IL)-4-induced regulators of cell growth, differentiation, and metabolism-related pathways. Experimental data also confirmed that the knockdown of GLUL in breast cancer cell lines decreased cell proliferation and influenced expressions of specific downstream molecules. Through a Connectivity Map (CMap) analysis, we revealed that certain drugs/molecules, including omeprazole, methacholine chloride, ioversol, fulvestrant, difenidol, cycloserine, and MK-801, may serve as potential treatments for tamoxifen-resistant breast cancer patients. These drugs may be tested in combination with current therapies in tamoxifen-resistant breast cancer patients. Collectively, our study demonstrated the crucial roles of GLUL, which provide new targets for the treatment of tamoxifen-resistant breast cancer patients.

Validation of a 3D perfused cell culture platform as a tool for humanised preclinical drug testing in breast cancer using established cell lines and patient-derived tissues

3D cell culture models of cancer are currently being developed to recapitulate in vivo physiological conditions and to assess therapeutic responses. However, most models failed to incorporate the biochemical and biophysical stimuli from fluid flow. In this study, a three-dimensional scaffold, SeedEZ was applied within the PerfusionPal perfused culture system to investigate how perfusion, and blood-like oxygen delivery influenced breast cancer cell growth and their responses to a commonly used breast cancer drug tamoxifen. Our results showed that breast cancer cells could be maintained over 3 weeks in PerfusionPal with increased cell viability compared to static 3D culture in fully humanised conditions. This platform also supported examining the effect of tamoxifen on breast cancer cell lines and in primary patient-derived breast cancer samples. Future work is warranted to further the adaption for fully humanised assessment of drug effectiveness in a patient personalized approach with the aim to reduce the burden of animal use in cancer research and increase the degree of human pre-clinical data translation to clinic.

Hyaluronic acid-based nano drug delivery systems for breast cancer treatment: Recent advances

Breast cancer (BC) is the most common malignancy among females worldwide, and high resistance to drugs and metastasis rates are the leading causes of death in BC patients. Releasing anti-cancer drugs precisely to the tumor site can improve the efficacy and reduce the side effects on the body. Natural polymers are attracting extensive interest as drug carriers in treating breast cancer. Hyaluronic acid (HA) is a natural polysaccharide with excellent biocompatibility, biodegradability, and non-immunogenicity and is a significant component of the extracellular matrix. The CD44 receptor of HA is overexpressed in breast cancer cells and can be targeted to breast tumors. Therefore, many researchers have developed nano drug delivery systems (NDDS) based on the CD44 receptor tumor-targeting properties of HA. This review examines the application of HA in NDDSs for breast cancer in recent years. Based on the structural composition of NDDSs, they are divided into HA NDDSs, Modified HA NDDSs, and HA hybrid NDDSs.

Appraising Adjuvant Endocrine Therapy in Hormone Receptor Positive HER2-Negative Breast Cancer—A Literature Review

Background: Approximately 75% of breast cancer (BC) is associated with luminal differentiation expressing endocrine receptors (ER). For ER+ HER2− tumors, adjuvant endocrine therapy (ET) is the cornerstone treatment. Although relapse events steadily continue, the ET benefits translate to dramatically lengthen life expectancy with bearable side-effects. This review of ER+ HER2− female BC outlines suitable adjuvant treatment strategies to help guide clinical decision making around appropriate therapy. Methods: A literature search was conducted in Embase, Medline, and the Cochrane Libraries, using ER+ HER−, ET BC keywords. Results: In low-risk patients: five years of ET is the standard option. While Tamoxifen remains the preferred selection for premenopausal women, AI is the choice for postmenopausal patients. In the high-risk category: ET plus/minus OFS with two years of Abemaciclib is recommended. Although extended ET for a total of ten years is an alternative, the optimal AI duration is undetermined; nevertheless an additional two to three years beyond the initial five years may be sufficient. In this postmenopausal group, bisphosphonate is endorsed. Conclusions: Classifying the risk category assists in deciding the treatment route and its optimal duration. Tailoring the breadth of ET hinges on a wide array of factors to be appraised for each individualized case, including weighing its benefits and harms.

The crucial role of epigenetic regulation in breast cancer anti-estrogen resistance: Current findings and future perspectives

Breast cancer (BC) cell de-sensitization to Tamoxifen (TAM) or other selective estrogen receptor (ER) modulators (SERM) is a complex process associated with BC heterogeneity and the transformation of ER signalling. The most influential resistance-related mechanisms include modifications in ER expression and gene regulation patterns. During TAM/SERM treatment, epigenetic mechanisms can effectively silence ER expression and facilitate the development of endocrine resistance. ER status is efficiently regulated by specific epigenetic tools including hypermethylation of CpG islands within ER promoters, increased histone deacetylase activity in the ER promoter, and/or translational repression by miRNAs. Over-methylation of the ER α gene (ESR1) promoter by DNA methyltransferases was associated with poor prognosis and indicated the development of resistance. Moreover, BC progression and spreading were marked by transformed chromatin remodelling, post-translational histone modifications, and expression of specific miRNAs and/or long non-coding RNAs. Therefore, targeted inhibition of histone acetyltransferases (e.g. MYST3), deacetylases (e.g. HDAC1), and/or demethylases (e.g. lysine-specific demethylase LSD1) was shown to recover and increase BC sensitivity to anti-estrogens. Indicated as a powerful molecular instrument, the administration of epigenetic drugs can regain ER expression along with the activation of tumour suppressor genes, which can in turn prevent selection of resistant cells and cancer stem cell survival. This review examines recent advances in the epigenetic regulation of endocrine drug resistance and evaluates novel anti-resistance strategies. Underlying molecular mechanisms of epigenetic regulation will be discussed, emphasising the utilization of epigenetic enzymes and their inhibitors to re-program irresponsive BCs.

Targeting Nuclear Receptors in Lung Cancer—Novel Therapeutic Prospects

Lung cancer, the second most commonly diagnosed cancer, is the major cause of fatalities worldwide for both men and women, with an estimated 2.2 million new incidences and 1.8 million deaths, according to GLOBOCAN 2020. Although various risk factors for lung cancer pathogenesis have been reported, controlling smoking alone has a significant value as a preventive measure. In spite of decades of extensive research, mechanistic cues and targets need to be profoundly explored to develop potential diagnostics, treatments, and reliable therapies for this disease. Nuclear receptors (NRs) function as transcription factors that control diverse biological processes such as cell growth, differentiation, development, and metabolism. The aberrant expression of NRs has been involved in a variety of disorders, including cancer. Deregulation of distinct NRs in lung cancer has been associated with numerous events, including mutations, epigenetic modifications, and different signaling cascades. Substantial efforts have been made to develop several small molecules as agonists or antagonists directed to target specific NRs for inhibiting tumor cell growth, migration, and invasion and inducing apoptosis in lung cancer, which makes NRs promising candidates for reliable lung cancer therapeutics. The current work focuses on the importance of various NRs in the development and progression of lung cancer and highlights the different small molecules (e.g., agonist or antagonist) that influence NR expression, with the goal of establishing them as viable therapeutics to combat lung cancer.

Chitosan: A versatile bio-platform for breast cancer theranostics

Breast cancer is considered one of the utmost neoplastic diseases globally, with a high death rate of patients. Over the last decades, many approaches have been studied to early diagnose and treat it, such as chemotherapy, hormone therapy, immunotherapy, and MRI and biomarker tests; do not show the optimal efficacy. These existing approaches are accompanied by severe side effects, thus recognizing these challenges, a great effort has been done to find out the new remedies for breast cancer. Main finding: Nanotechnology opened a new horizon to the treatment of breast cancer. Many nanoparticulate platforms for the diagnosis of involved biomarkers and delivering antineoplastic drugs are under either clinical trials or just approved by the Food and Drug Administration (FDA). It is well known that natural phytochemicals are successfully useful to treat breast cancer because these natural compounds are safer, available, cheaper, and have less toxic effects. Chitosan is a biocompatible and biodegradable polymer. Further, it has outstanding features, like chemical functional groups that can easily modify our interest with an exceptional choice of promising applications. Abundant studies were directed to assess the chitosan derivative-based nanoformulation's abilities in delivering varieties of drugs. However, the role of chitosan in diagnostics and theranostics not be obligated. The present servey will discuss the application of chitosan as an anticancer drug carrier such as tamoxifen, doxorubicin, paclitaxel, docetaxel, etc. and also, its role as a theranostics (i.e. photo-responsive and thermo-responsive) moieties. The therapeutic and theranostic potential of chitosan in cancer is promising and it seems that to have a good potential to get to the clinic.

p21 activated kinase-1 and tamoxifen - A deadly nexus impacting breast cancer outcomes

Tamoxifen is a commonly used drug in the treatment of ER + ve breast cancers since 1970. However, development of resistance towards tamoxifen limits its remarkable clinical success. In this review, we have attempted to provide a brief overview of multiple mechanism that may lead to tamoxifen resistance, with a special emphasis on the roles played by the oncogenic kinase- PAK1. Analysing the genomic data sets available in the cBioPortal, we found that PAK1 gene amplification significantly affects the Relapse Free Survival of the ER + ve breast cancer patients. While PAK1 is known to promote tamoxifen resistance by phosphorylating ERα at Ser305, existing literature suggests that PAK1 can fuel up tamoxifen resistance obliquely by phosphorylating other substrates. We have summarised some of the approaches in the mass spectrometry based proteomics, which would enable us to study the tamoxifen resistance specific phosphoproteomic landscape of PAK1. We also propose that elucidating the multiple mechanisms by which PAK1 promotes tamoxifen resistance might help us discover druggable targets and biomarkers.

Estrogen Receptor: A Paradigm for Targeted Therapy

Nearly two-thirds of breast cancers overexpress estrogen receptors, and endocrine therapy is considered the backbone of systemic therapy both in early and advanced settings. While this is now widely recognized in clinical practice, this is the culmination of outstanding contribution of many investigators and patients. Indubitably, estrogen receptor targeting has had the most impact among targeted therapies and has significantly affected patient survival. In this commentary, we revisit a landmark article published in Cancer Research in 1977 by Knight and colleagues, which laid the groundwork for the use of estrogen receptors in prognostication and adjuvant treatment selection, as well as some of the key breakthroughs in estrogen receptor biology that span more than a century.See related article by Knight and colleagues, Cancer Res 1977;37:4669-71.

CYP3A4∗22 Genotyping in Clinical Practice: Ready for Implementation?

Cytochrome P450 3A4 (CYP3A4) is the most important drug metabolizing enzyme in the liver, responsible for the oxidative metabolism of ∼50% of clinically prescribed drugs. Therefore, genetic variation in CYP3A4 could potentially affect the pharmacokinetics, toxicity and clinical outcome of drug treatment. Thus far, pharmacogenetics for CYP3A4 has not received much attention. However, the recent discovery of the intron 6 single-nucleotide polymorphism (SNP) rs35599367C > T, encoding the CYP3A4^∗22 allele, led to several studies into the pharmacogenetic effect of CYP3A4^∗22 on different drugs. This allele has a relatively minor allele frequency of 3-5% and an effect on CYP3A4 enzymatic activity. Thus far, no review summarizing the data published on several drugs is available yet. This article therefore addresses the current knowledge on CYP3A4^∗22. This information may help in deciding if, and for which drugs, CYP3A4^∗22 genotype-based dosing could be helpful in improving drug therapy. CYP3A4^∗22 was shown to significantly influence the pharmacokinetics of several drugs, with currently being most thoroughly investigated tacrolimus, cyclosporine, and statins. Additional studies, focusing on toxicity and clinical outcome, are warranted to demonstrate clinical utility of CYP3A4^∗22 genotype-based dosing.

FLTX2: A Novel Tamoxifen Derivative Endowed with Antiestrogenic, Fluorescent, and Photosensitizer Properties

Tamoxifen is the most widely used selective modulator of estrogen receptors (SERM) and the first strategy as coadjuvant therapy for the treatment of estrogen-receptor (ER) positive breast cancer worldwide. In spite of such success, tamoxifen is not devoid of undesirable effects, the most life-threatening reported so far affecting uterine tissues. Indeed, tamoxifen treatment is discouraged in women under risk of uterine cancers. Recent molecular design efforts have endeavoured the development of tamoxifen derivatives with antiestrogen properties but lacking agonistic uterine tropism. One of this is FLTX2, formed by the covalent binding of tamoxifen as ER binding core, 7-nitrobenzofurazan (NBD) as the florescent dye, and Rose Bengal (RB) as source for reactive oxygen species. Our analyses demonstrate (1) FLTX2 is endowed with similar antiestrogen potency as tamoxifen and its predecessor FLTX1, (2) shows a strong absorption in the blue spectral range, associated to the NBD moiety, which efficiently transfers the excitation energy to RB through intramolecular FRET mechanism, (3) generates superoxide anions in a concentration- and irradiation time-dependent process, and (4) Induces concentration- and time-dependent MCF7 apoptotic cell death. These properties make FLTX2 a very promising candidate to lead a novel generation of SERMs with the endogenous capacity to promote breast tumour cell death in situ by photosensitization.

Regioselective Synthesis of α-Functional Stilbenes via Precise Control of Rapid cis-trans Isomerization in Flow

The rapid cis-trans isomerization of α-anionic stilbene was regioselectively controlled by using flow microreactors, and its reaction with various electrophiles was conducted. The reaction time was precisely controlled within milliseconds to seconds at -50 °C to selectively give the cis- or trans-isomer in high yields. This synthetic method in flow was well-applied to synthesize precursors of commercial drug compound, (E)- and (Z)-tamoxifen with high regioselectivity and productivity.

CUL4B renders breast cancer cells tamoxifen-resistant via miR-32-5p/ER-α36 axis

Tamoxifen (TAM) resistance is a significant clinical challenge in endocrine therapies for estrogen receptor (ER)-positive breast cancer patients. Cullin 4B (CUL4B), which acts as a scaffold protein in CUL4B-RING ubiquitin ligase complexes (CRL4B), is frequently overexpressed in cancer and represses tumor suppressors through diverse epigenetic mechanisms. However, the role and the underlying mechanisms of CUL4B in regulating drug resistance remain unknown. Here, we showed that CUL4B promotes TAM resistance in breast cancer cells through a miR-32-5p/ER-α36 axis. We found that upregulation of CUL4B correlated with decreased TAM sensitivity of breast cancer cells, and knockdown of CUL4B or expression of a dominant-negative CUL4B mutant restored the response to TAM in TAM-resistant MCF7-TAM^R and T47D-TAM^R cells. Mechanistically, we demonstrated that CUL4B renders breast cancer cells TAM-resistant by upregulating ER-α36 expression, which was mediated by downregulation of miR-32-5p. We further showed that CRL4B epigenetically represses the transcription of miR-32-5p by catalyzing monoubiquitination at H2AK119 and coordinating with PRC2 and HDAC complexes to promote trimethylation at H3K27 at the promoter of miR-32-5p. Pharmacologic or genetic inhibition of CRL4B/PRC2/HDAC complexes significantly increased TAM sensitivity in breast cancer cells in vitro and in vivo. Taken together, our findings thus establish a critical role for the CUL4B-miR-32-5p-ER-α36 axis in the regulation of TAM resistance and have important therapeutic implications for combined application of TAM and the inhibitors of CRL4B/PRC2/HDAC complex in breast cancer treatment. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The Antiproliferative and Apoptotic Effect of a Novel Synthesized S-Triazine Dipeptide Series, and Toxicity Screening in Zebrafish Embryos

Several derivatives containing morpholine/piperidine, anilines, and dipeptides as pending moieties were prepared using s-triazine as a scaffold. These compounds were evaluated for their anticancer activity against two human breast cancer cell lines (MCF-7 and MDA-MB-231), a colon cancer cell line (HCT-116), and a non-tumorigenic cell line (HEK 293). Tamoxifen was used as a reference. Animal toxicity tests were carried out in zebrafish embryos. Most of these compounds showed a higher activity against breast cancer than colon cancer. Compound 3a-which contains morpholine, aniline, and glycylglycinate methyl ester-showed a high level of cytotoxicity against MCF-7 cells with IC₅₀ values of less than 1 µM. This compound showed a much lower level of toxicity against the non-tumorigenic HEK-293 cell line, and in the in vivo studies using zebrafish embryos. Furthermore, it induced cell cycle arrest at the G2/M phase, and apoptosis in MCF-7 cells. On the basis of our results, 3a emerges as a potential candidate for further development as a therapeutic drug to treat hormone receptor-positive breast cancer.

Recent Advances in Integrative Multi-Omics Research in Breast and Ovarian Cancer

The underlying molecular heterogeneity of cancer is responsible for the dynamic clinical landscape of this disease. The combination of genomic and proteomic alterations, including both inherited and acquired mutations, promotes tumor diversity and accounts for variable disease progression, therapeutic response, and clinical outcome. Recent advances in high-throughput proteogenomic profiling of tumor samples have resulted in the identification of novel oncogenic drivers, tumor suppressors, and signaling networks; biomarkers for the prediction of drug sensitivity and disease progression; and have contributed to the development of novel and more effective treatment strategies. In this review, we will focus on the impact of historical and recent advances in single platform and integrative proteogenomic studies in breast and ovarian cancer, which constitute two of the most lethal forms of cancer for women, and discuss the molecular similarities of these diseases, the impact of these findings on our understanding of tumor biology as well as the clinical applicability of these discoveries.

Clinical CYP2D6 Genotyping to Personalize Adjuvant Tamoxifen Treatment in ER-Positive Breast Cancer Patients: Current Status of a Controversy

Simple Summary

Tamoxifen is an important adjuvant endocrine therapy in estrogen receptor (ER)-positive breast cancer patients. It is mainly catalyzed by the enzyme CYP2D6 into the most active metabolite endoxifen. Genetic variation in the CYP2D6 gene influences endoxifen formation and thereby potentially therapy outcome. However, the association between CYP2D6 genotype and clinical outcome on tamoxifen is still under debate, as contradictory outcomes have been published. This review describes the latest insights in both CYP2D6 genotype and endoxifen concentrations, as well CYP2D6 genotype and clinical outcome, from 2018 to 2020.

Abstract

Tamoxifen is a major option for adjuvant endocrine treatment in estrogen receptor (ER) positive breast cancer patients. The conversion of the prodrug tamoxifen into the most active metabolite endoxifen is mainly catalyzed by the enzyme cytochrome P450 2D6 (CYP2D6). Genetic variation in the CYP2D6 gene leads to altered enzyme activity, which influences endoxifen formation and thereby potentially therapy outcome. The association between genetically compromised CYP2D6 activity and low endoxifen plasma concentrations is generally accepted, and it was shown that tamoxifen dose increments in compromised patients resulted in higher endoxifen concentrations. However, the correlation between CYP2D6 genotype and clinical outcome is still under debate. This has led to genotype-based tamoxifen dosing recommendations by the Clinical Pharmacogenetic Implementation Consortium (CPIC) in 2018, whereas in 2019, the European Society of Medical Oncology (ESMO) discouraged the use of CYP2D6 genotyping in clinical practice for tamoxifen therapy. This paper describes the latest developments on CYP2D6 genotyping in relation to endoxifen plasma concentrations and tamoxifen-related clinical outcome. Therefore, we focused on Pharmacogenetic publications from 2018 (CPIC publication) to 2021 in order to shed a light on the current status of this debate.

Paeoniflorin Sensitizes Breast Cancer Cells to Tamoxifen by Downregulating microRNA-15b via the FOXO1/CCND1/β-Catenin Axis

Background

Paeoniflorin (Pae) possesses anti-tumor activity in various malignancies. However, it is unclear whether Pae plays a sensitizer role in breast cancer (BC) and the molecular mechanisms involved in this process. Our oligonucleotide microarray revealed that microRNA (miR)-15b is the most significantly downregulated miRNA in MCF-7/4-hydroxytamoxifen (4-OHT) cells treated with Pae. This paper summarized the relevance of Pae in BC cell endocrine resistance to tamoxifen (Tam) and the molecular mechanisms involved miR-15b expression.

Materials and Methods

4-OHT-resistant BC cell lines were developed and treated with different concentrations of Pae. Flow cytometry, lactose dehydrogenase activity, caspase-3 activity, colony formation, and EdU assays were carried out to assess the impact of Pae on BC cells. Differentially expressed miRNAs in BC cells treated with Pae were analyzed by microarray. Targeting mRNAs of screened miR-15b as well as the binding of forkhead box O1 (FOXO1) to the cyclin D1 (CCND1) promoter sequence were predicted through bioinformatics analysis. Finally, the expression of β-catenin signaling-related genes in cells was detected by Western blotting.

Results

Pae (100 μg/mL) inhibited the clonality and viability of BC cells, while enhancing apoptosis in vitro. Pae also repressed miR-15b expression. Overexpression of miR-15b restored the growth and resistance of BC cells to 4-OHT. Moreover, Pae promoted FOXO1 expression by downregulating miR-15b, thereby transcriptionally inhibiting CCND1 and subsequently blocking β-catenin signaling.

Conclusion

Pae inhibits 4-OHT resistance in BC cells by regulating the miR-15b/FOXO1/CCND1/β-catenin pathway.

Alterations in Progesterone Receptor Isoform Balance in Normal and Neoplastic Breast Cells Modulates the Stem Cell Population

To investigate the role of PR isoforms on the homeostasis of stem cells in the normal and neoplastic mammary gland, we used PRA and PRB transgenic mice and the T47D human breast cancer cell line and its derivatives, T47D YA and YB (manipulated to express only PRA or PRB, respectively). Flow cytometry and mammosphere assays revealed that in murine breast, overexpression of PRB leads to an increase in luminal and basal progenitor/stem cells. Ovariectomy had a negative impact on the luminal compartment and induced an increase in mammosphere-forming capacity in cells derived from WT and PRA mice only. Treatment with ICI 182,780 augmented the mammosphere-forming capacity of cells isolated from WT and PRA mice, whilst those from PRB remained unaltered. T47D YB cells showed an increase in the CD44⁺/CD24^Low/- subpopulation; however, the number of tumorspheres did not vary relative to T47D and YA, even though they were larger, more irregular, and had increased clonogenic capacity. T47D and YA tumorspheres were modulated by estrogen/antiestrogens, whereas YB spheres remained unchanged in size and number. Our results show that alterations in PR isoform balance have an impact on normal and tumorigenic breast progenitor/stem cells and suggest a key role for the B isoform, with implications in response to antiestrogens.

Serendipity in the search for "morning-after pills" led to clomiphene for the induction of ovulation

The approval of the oral contraceptive on June 23, 1960, by the United States Food and Drug Administration (FDA), changed society forever. For the first time, a pill designed and tested by men, supported by influential women, allowed women to control their fertility. For the first time, the FDA approved a medicine to be taken by humans without a disease. The chance discovery of a new group of medicines called nonsteroidal antiestrogens, created an opportunity for the pharmaceutical industry. These compounds were shown to be postcoital antifertility agents in rats and mice. In the 1960s, the development of a "morning-after pill" would have had an enormous market. Numerous companies focused discovery efforts to evaluate the development of their patented nonsteroidal antiestrogens: Merrell (clomiphene), Upjohn (U-11,100A), and ICI Pharmaceutical Division (ICI46,474). However, the antifertility effects of antiestrogens in rats and mice does not mean that the new medicine would be an antifertility agent in women. In this case, clomiphene did exactly the opposite of what it was predicted to prevent. Clomiphene became the first medicine to induce ovulation in subfertile women. This article describes the twists and turns of drug discovery and development over the past half century. The conclusion emphasizes the evolution of drug development over decades, based on fashions in medical research and discoveries in clinical pharmacology. As a result, new uses for old molecules, that started life as "nonsteroidal antiestrogens," have revolutionized women's health as members of the new group of medicines called selective estrogen receptor modulators.

Computer-Aided Ligand Discovery for Estrogen Receptor Alpha

Breast cancer (BCa) is one of the most predominantly diagnosed cancers in women. Notably, 70% of BCa diagnoses are Estrogen Receptor α positive (ERα+) making it a critical therapeutic target. With that, the two subtypes of ER, ERα and ERβ, have contrasting effects on BCa cells. While ERα promotes cancerous activities, ERβ isoform exhibits inhibitory effects on the same. ER-directed small molecule drug discovery for BCa has provided the FDA approved drugs tamoxifen, toremifene, raloxifene and fulvestrant that all bind to the estrogen binding site of the receptor. These ER-directed inhibitors are non-selective in nature and may eventually induce resistance in BCa cells as well as increase the risk of endometrial cancer development. Thus, there is an urgent need to develop novel drugs with alternative ERα targeting mechanisms that can overcome the limitations of conventional anti-ERα therapies. Several functional sites on ERα, such as Activation Function-2 (AF2), DNA binding domain (DBD), and F-domain, have been recently considered as potential targets in the context of drug research and discovery. In this review, we summarize methods of computer-aided drug design (CADD) that have been employed to analyze and explore potential targetable sites on ERα, discuss recent advancement of ERα inhibitor development, and highlight the potential opportunities and challenges of future ERα-directed drug discovery.

Exposure-response analysis of endoxifen serum concentrations in early-breast cancer

Purpose

Tamoxifen is part of endocrine therapy in breast cancer treatment. Studies have indicated the use of endoxifen concentrations, tamoxifen active metabolite, to guide tamoxifen efficacy. Three endoxifen thresholds have been suggested (5.9 ng/ml, 5.2 ng/ml and 3.3 ng/ml) for therapeutic drug monitoring (TDM). Our aim was to validate these thresholds and to examine endoxifen exposure with clinical outcome in early-breast cancer patients using tamoxifen.

Methods

Data from 667 patients from the CYPTAM study (NTR1509) were available. Patients were stratified (above or below), according to the endoxifen threshold values for tamoxifen efficacy and tested by Cox regression. Logistic regressions to estimate the probability of relapse and tamoxifen discontinuation were performed.

Results

None of the thresholds showed a statistically significant difference in relapse-free survival: 5.2 ng/ml threshold: hazard ratio (HR): 2.545, 95% confidence interval (CI) 0.912–7.096, p value: 0.074; 3.3 ng/ml threshold: HR: 0.728; 95% CI 0.421–1.258, p value: 0.255. Logistic regression did not show a statistically significant association between the risk of relapse (odds ratio (OR): 0.971 (95% CI 0.923–1.021, p value: 0.248) and the risk for tamoxifen discontinuation (OR: 1.006 95% CI 0.961–1.053, p value: 0.798) with endoxifen concentrations.

Conclusion

Our findings do not confirm the endoxifen threshold values for TDM nor does it allow definition of a novel threshold. These findings indicate a limited value of TDM to guide tamoxifen efficacy.

The Role of Long Noncoding RNAs in Antiestrogen Resistance in Breast Cancer: An Overview and Update

As a standard treatment, endocrine therapy has dramatically enhanced the prognosis of patients with estrogen receptor (ER)-positive breast cancer, which accounts for nearly 70% of all breast cancers. Antiestrogen drugs such as tamoxifen and aromatase inhibitors are the standard treatment options for ERα-positive breast cancer. However, acquired antiestrogen resistance is still the leading cause of disease recurrence and progression. Evidence has shown that long noncoding RNAs (lncRNAs) play an essential role in the development of antiestrogen resistance in ER-positive breast cancer and can serve as biomarkers or potential therapeutic targets. This review highlights the role of lncRNAs in the development of antiestrogen resistance in breast cancer.

Although c‑MYC contributes to tamoxifen resistance, it improves cisplatin sensitivity in ER‑positive breast cancer

Tamoxifen (TAM) resistance is a major challenge in the treatment of estrogen receptor‑positive (ER+) breast cancer. To date, to the best of our knowledge, there are only a few studies available examining the response of patients with TAM‑resistant breast cancer to chemotherapy, and the guidelines do not specify recommended drugs for these patients. In the present study, TAM‑resistant cells were shown to exhibit increased proliferation and invasion compared with the parent cells, and the increased expression of c‑MYC was demonstrated to play an important role in TAM resistance. Furthermore, the TAM‑resistant cells were significantly more sensitive to cisplatin compared with the parent cells, and the silencing of c‑MYC expression desensitized the cells to cisplatin through the inhibition of the cell cycle. An increased c‑MYC expression was observed in 28 pairs of primary and metastatic tumors from patients treated with TAM, and the clinical remission rate of cisplatin‑based chemotherapy was significantly higher compared with other chemotherapy‑based regimens in 122 patients with TAM resistant breast cancer. Taken together, the data of the present study demonstrated that although c‑MYC was involved in TAM resistance, it increased the sensitivity of ER+ breast cancer to cisplatin. Thus, cisplatin may be a preferred chemotherapeutic agent for the treatment of patients with TAM‑resistant breast cancer, particularly in patients where the rapid control of disease progression is required.

A new class of 1,3,5-triazine-based selective estrogen receptor degraders (SERDs): Lead optimization, molecular docking and dynamic simulation

Selective estrogen receptor degrader (SERD) that acts as not only ER antagonist, but also ER degrader, would be useful for the treatment for drug-resistance ER+ breast cancer. However, most of currently available SERD candidates involve very limited molecular scaffolds and are still in clinical trials. In this study, we introduced a 1,3,5-triazine ring into a homobibenzyl motif extracted from amounts of ER ligands and synthesized sixteen SERDs bearing acrylic acid or acrylic amide side chains that possess both ERα antagonism and degradation properties. And all compounds were screened for their anti-proliferative activity against ER+ MCF-7 and Ishikawa cell lines. Among them, compound XHA1614 displayed potent growth inhibition activity against MCF-7 and Ishikawa cells with IC₅₀ values of 3.15 μM and 3.11 μM, respectively. Moreover, XHA1614 could dramatically degrade ER level at 1 nM in a Western blotting assay and afforded an outstanding antagonistic activity via suppressing the expression of progesterone receptor messenger RNA in MCF-7 cells in a RT-PCR assay. Further molecular docking and dynamic simulation on properly selected derivative furnished insights into its binding profile within ERα. Our findings suggest that the 1,3,5-triazine core was a feasible alternative to currently reported SERD scaffold, and provide information that will be useful for further development of promising SERDs candidates for breast cancer therapies.

Pan-cancer analyses of human nuclear receptors reveal transcriptome diversity and prognostic value across cancer types

The human nuclear receptor (NR) superfamily comprises 48 ligand-dependent transcription factors that play regulatory roles in physiology and pathophysiology. In cancer, NRs have long served as predictors of disease stratification, treatment response, and clinical outcome. The Cancer Genome Atlas (TCGA) Pan-Cancer project provides a wealth of genetic data for a large number of human cancer types. Here, we examined NR transcriptional activity in 8,526 patient samples from 33 TCGA ‘Pan-Cancer’ diseases and 11 ‘Pan-Cancer’ organ systems using RNA sequencing data. The web-based Kaplan-Meier (KM) plotter tool was then used to evaluate the prognostic potential of NR gene expression in 21/33 cancer types. Although, most NRs were significantly underexpressed in cancer, NR expression (moderate to high expression levels) was predominantly restricted (46%) to specific tissues, particularly cancers representing gynecologic, urologic, and gastrointestinal ‘Pan-Cancer’ organ systems. Intriguingly, a relationship emerged between recurrent positive pairwise correlation of Class IV NRs in most cancers. NR expression was also revealed to play a profound effect on patient overall survival rates, with ≥5 prognostic NRs identified per cancer type. Taken together, these findings highlighted the complexity of NR transcriptional networks in cancer and identified novel therapeutic targets for specific cancer types.

ERα36 as a Potential Therapeutic Target for Tamoxifen-Resistant Breast Cancer Cell Line Through EGFR/ERK Signaling Pathway

Background

Acquired tamoxifen resistance is one of the major barriers to the successful treatment of breast cancer. Recently, overexpression of ERα36 was demonstrated to be a potential mechanism for the generation of acquired tamoxifen resistance. This study aims to evaluate the possibility of ERα36 being a therapeutic target for tamoxifen-resistant breast cancer.

Methods

A tamoxifen-resistant cell subline (MCF-7/TAM) was established by culturing MCF-7 cells in medium plus 1 μM tamoxifen over 6 months. Colony-forming assay was used to determine the sensitivity of MCF-7/TAM cells to tamoxifen. Stable transfection was used to knockdown ERα36 expression in MCF-7/TAM cells. MTT assay and Transwell migration assay were used to assess the in vitro proliferation and migration, respectively. Nude mouse tumorigenicity assay was used to evaluate in vivo tumorigenicity. Western blot analysis and quantitative real-time PCR (qRT-PCR) were used to examine the expression of ERα36, ERα, EGFR and phosphorylated ERK1/2. The dual-luciferase reporter assay was used to determine the effect of ERα36 on the activity of EGFR-promotor.

Results

MCF-7/TAM cells possessed greatly increased ERα36 expression and EGFR expression and exhibited significantly increased in vitro proliferation and migration ability, as well as increased in vivo tumor growth ability, compared to parental MCF-7 cells. Knockdown of ERα36 expression inhibited in vitro proliferation and migration, as well as in vivo tumor growth ability of MCF-7/TAM cells. ERα36 regulated EGFR expression at the transcriptional level, and knockdown of ERα36 in MCF-7/TAM cells downregulated EGFR expression and then blocked EGFR/ERK signaling pathway.

Conclusion

Knockdown of ERα36 inhibits the growth of MCF-7/TAM cells in vitro and in vivo by blocking EGFR/ERK signaling pathway. ERα36 may be a candidate therapeutic target for the treatment of tamoxifen-resistant breast cancer.

Alginate based tamoxifen/metal dual core-folate decorated shell: Nanocomposite targeted therapy for breast cancer via ROS-driven NF-κB pathway modulation

Breast cancer endocrine resistance prevents unleashing full capabilities of Tamoxifen (TMX), besides TMX off-target side effects on healthy tissue. In this study, we engineered TMX nanocomposite via co-loading it on alginate-based silver nanoparticles and embedding within folic acid-polyethylene glycol surface conjugate. The coating process was done by w/o/w double emulsion method. To confirm the silver nanoparticles formation, UV spectroscopy, XRD and TEM analysis were carried out. TEM results confirmed the core-shell structure of folate targeted nanocomposite with approximate average diameter of 66 nm, the nanocomposite structures were characterized by FTIR, TGA and SEM. By comparing with the non-targeted formula, folate decorated formula had 12-folds lowered IC₅₀ value and 12.5-14-fold higher cancer cells toxic selectivity index. Also, after 4 h treatment, both fluorescence microscopic and flow cytometric analysis indicated higher intracellular accumulation of folic acid conjugated formula on MCF-7 cancer cells than the non-targeted one with 3.44-folds. The breast cancer cytotoxic effects of this metal-endocrine nanocomposite formula could be explained by the induction of reactive oxygen species (ROS), down regulation of survival oncogenic genes (BCL-2 and Survivin) and the accumulation of MCF-7 cells in G2/M phase. All these data confirm the efficiency and efficacy of the formulated nanocomposite as future treatment for breast cancer.

iRGD-guided tamoxifen polymersomes inhibit estrogen receptor transcriptional activity and decrease the number of breast cancer cells with self-renewing capacity

BACKGROUND

Tamoxifen (Tam) is the most frequent treatment for estrogen receptor (ER) positive breast cancer. We recently showed that fibronectin (FN) leads to Tam resistance and selection of breast cancer stem cells. With the aim of developing a nanoformulation that would simultaneously tackle ER and FN/β1 integrin interactions, we designed polyethylene glycol-polycaprolactone polymersomes polymersomes (PS) that carry Tam and are functionalized with the tumor-penetrating iRGD peptide (iRGD-PS-Tam).

RESULTS

Polyethylene glycol-polycaprolactone PS were assembled and loaded with Tam using the hydration film method. The loading of encapsulated Tam, measured by UPLC, was 2.4 ± 0.5 mol Tam/mol polymer. Physicochemical characterization of the PS demonstrated that iRGD functionalization had no effect on morphology, and a minimal effect on the PS size and polydispersity (176 nm and Pdi 0.37 for iRGD-TAM-PS and 171 nm and Pdi 0.36 for TAM-PS). iRGD-PS-Tam were taken up by ER+ breast carcinoma cells in 2D-culture and exhibited increased penetration of 3D-spheroids. Treatment with iRGD-PS-Tam inhibited proliferation and sensitized cells cultured on FN to Tam. Mechanistically, treatment with iRGD-PS-Tam resulted in inhibition ER transcriptional activity as evaluated by a luciferase reporter assay. iRGD-PS-Tam reduced the number of cells with self-renewing capacity, a characteristic of breast cancer stem cells. In vivo, systemic iRGD-PS-Tam showed selective accumulation at the tumor site.

CONCLUSIONS

Our study suggests iRGD-guided delivery of PS-Tam as a potential novel therapeutic strategy for the management of breast tumors that express high levels of FN. Future studies in pre-clinical in vivo models are warranted.

17β-estradiol at low concentrations attenuates the efficacy of tamoxifen in breast cancer therapy

Tamoxifen has been applied widely in the treatment of estrogen receptor (ER)-positive breast cancer. The impact of low concentrations of 17β-estradiol (E2) (a pervasive environmental pollutant) on its effectiveness was studied in vitro using an MCF-7 cell line. Cell proliferation, migration, invasion, and apoptosis were studied along with cell cycle progression, reactive oxygen species generation and mitochondrial membrane potentials repression. The signaling pathways involved were identified. Typical concentrations of E2 in the environment (10^-10 to 10^-8 M) were observed to promote cell growth and protect MCF-7 cells from tamoxifen's cytotoxicity. Cell migration, invasion, cell cycle progression and apoptosis all involved in reducing tamoxifen's cytotoxicity. E2 at environmental concentrations induced PI3K/Akt and MAPK/ERK signal transduction through the estrogen receptor pathways to affect cell proliferation. Taken together, the results explain how E2 in the environment may attenuate the efficacy of tamoxifen in ER-positive breast cancer therapy. They provide considerable support for E2's adverse effects on human health and cancer management.