Metformin inhibits 7,12-dimethylbenz[a]anthracene-induced breast carcinogenesis and adduct formation in human breast cells by inhibiting the cytochrome P4501A1/aryl hydrocarbon receptor signaling pathway

Metformin attenuates PM2.5-induced oxidative stress by inhibiting the AhR/CYP1A1 pathway in proximal renal tubular epithelial cells

The harmful effects of PM2.5 on human health, including an increased risk of chronic kidney disease (CKD), have raised a lot of attention, but the underlying mechanisms are unclear. We used the Shanghai Meteorological and Environmental Animal Exposure System (Shanghai-METAS) to simulate the inhalation of PM2.5 in the real environment and established an animal model by exposing C57BL/6 mice to filtered air (FA) and Particulate Matter (PM2.5) for 8 weeks. PM2.5 impaired the renal function of the mice, and the renal tubules underwent destructive changes. Analysis of NHANES data showed a correlation between reduced kidney function and higher blood levels of PM2.5 components, polychlorinated biphenyls (PCBs) and dioxins, which are Aryl hydrocarbon Receptor (AhR) ligands. PM2.5 exposure induced higher levels of AhR and CYP1A1 and oxidative stress as evidenced by the higher levels of ROS, MDA, and GSSG in kidneys of mice. PM2.5 exposure led to AhR overexpression and nuclear translocation in proximal renal tubular epithelial cells. Inhibition of AhR reduced CYP1A1 expression and PM2.5-increased levels of ROS, MDA and GSSG. Our study suggested metformin can mitigate PM2.5-induced oxidative stress by inhibiting the AhR/CYP1A1 pathway. These findings illuminated the role of AhR/CYP1A1 pathway in PM2.5-induced kidney injury and the protective effect of metformin on PM2.5-induced cellular damage, offering new insights for air pollution-related renal diseases.

Role of Aryl Hydrocarbon Receptor and Oxidative Stress in the Regioselective Toxicities of Hydroxychrysenes in Embryonic Japanese Medaka (Oryzias latipes)

Oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) are environmental contaminants that can be created through oxidation of parent PAHs. Previous studies have found that 2-hydroxychrysene (2-OHCHR) caused anemia in embryonic Japanese medaka whereas 6-hydroxychrysene (6-OHCHR) did not, an example of regioselective toxicity. Anemia was prevented by cytochrome P450 (CYP) inhibition, which reduced the formation of the potential oxidatively active metabolite, 1,2-catechol, from 2-OHCHR. 2-OHCHR has also been found to be a four-fold more potent aryl hydrocarbon receptor (AhR) agonist compared with 6-OHCHR. These findings led us to hypothesize that AhR activation and/or oxidative stress play an important role in 2-OHCHR toxicity. Although treatments with the AhR agonists polychlorinated biphenyl (PCB)126 and 2-methoxychrysene (2-MeOCHR) did not cause significant toxicity, pretreatments with the AhR antagonist, CH-223191, reduced anemia by 97.2 ± 0.84% and mortality by 96.6 ± 0.69%. Aryl hydrocarbon receptor inhibition by the antagonist was confirmed by significant reductions (91.0 ± 9.94%) in induced ethoxyresorufin-O-deethylase activity. Thiobarbituric acid reactive substances concentrations were 32.9 ± 3.56% higher (p < 0.05) in 2-OHCHR treatments at 100 hours postfertilization compared with controls. Staining 2-OHCHR-treated embryos with the reactive oxygen species (ROS) scavenger 2',7'-dichlorofluorescin diacetate revealed 32.6 ± 2.69% of 2-OHCHR-treated embryos exhibiting high concentrations of ROS in caudal tissues, which is a site for embryonic hematopoiesis in medaka. Pretreatment with antioxidants, N-acetylcysteine (NAC) or vitamin E (Vit E) significantly reduced 2-OHCHR-induced anemia (NAC: 80.7 ± 1.12% and Vit E: 99.1 ± 0.43%) and mortality (NAC: 67.1 ± 1.69% and Vit E: 98.9 ± 0.66%). These results indicate that AhR may mediate 2-OHCHR toxicity through canonical signaling by up-regulating CYP1, enhancing the formation of reactive metabolites of 2-OHCHR that generate ROS within caudal hematopoietic tissues, potentially disrupting hematopoiesis, leading to anemia and subsequent mortality. Environ Toxicol Chem 2023;42:698-706. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Crosstalk Between Aryl Hydrocarbon Receptor (AhR) and BCL-2 Pathways Suggests the Use of AhR Antagonist to Maintain Normal Differentiation State of Mammary Epithelial Cells During BCL-2 Inhibition Therapy

INTRODUCTION

Activating the aryl hydrocarbon receptor upon exposure to environmental pollutants promotes development of breast cancer stem cell (CSCs). BCL-2 family proteins protect cancer cells from the apoptotic effects of chemotherapeutic drugs. However, the crosstalk between AhR and the BCL-2 family in CSC development remains uninvestigated.

OBJECTIVES

This study explored the interaction mechanisms between AhR and BCL-2 in CSC development and chemoresistance.

METHODS

A quantitative proteomic analysis study was performed as a tool for comparative expression analysis of breast cancer cells treated by AhR agonist. The basal and inducible levels of BCL-2, AhR, and CYP1A1 in vitro breast cancer and epithelial cell lines and in vivo mice animal models were determined by RT-PCR, Western blot analysis, immunofluorescence, flow cytometry, silencing of the target, and immunohistochemistry. In addition, an in silico toxicity study was conducted using DEREK software.

RESULTS

Activation of the AhR/CYP1A1 pathway in mice increased EpCAM^High/CD49f^Low CD61⁺ luminal progenitor-like cells in early tumor formation but not in advanced tumors. In parallel, a chemoproteomic study on breast cancer MCF-7 cells revealed that the BCL-2 protein expression was the most upregulated upon AhR activation. The crosstalk between the AhR and BCL-2 pathways in vitro and in vivo modulated the CSCs features and chemoresistance. Interestingly, inhibition of BCL-2 in mice by venetoclax (VCX) increased EpCAM^High/CD49f^Low CD61⁺ luminal progenitor-like cells, causing inhibition of epithelial lineage markers, disruption of mammary gland branching and induced the epithelial-mesenchymal transition in mammary epithelial cells (MECs). The combined treatment of VCX and AhR antagonists in mice corrected the abnormal differentiation in MECs and protected mammary gland branching and cell identity.

CONCLUSIONS

This is the first study to report crosstalk between AhR and BCL-2 in breast CSCs and provides the rationale for using a combined treatment of BCL-2 inhibitor and AhR antagonist for more effective cancer prevention and treatment.

A Mini-Review of Flavone Isomers Apigenin and Genistein in Prostate Cancer Treatment

The initial responses to standard chemotherapies among prostate cancer (PCa) patients are usually significant, while most of them will finally develop drug resistance, rendering them with limited therapies. To discover new regimens for the treatment of PCa including resistant PCa, natural products, the richest source of bioactive compounds, can serve as a library for screening and identifying promising candidates, and flavones such as apigenin and genistein have been used in lab and clinical trials for treating PCa over decades. In this mini-review, we take a look into the progress of apigenin and genistein, which are isomers, in treating PCa in the past decade. While possessing very similar structure, these two isomers can both target the same signaling pathways; they also are found to work differently in PCa cells. Given that more combinations are being developed and tested, genistein appears to be the more promising option to be approved. The anticancer efficacies of these two flavones can be confirmed by in-vitro and in-vivo studies, and their applications remain to be validated in clinical trials. Information gained in this work may provide important information for new drug development and the potential application of apigenin and genistein in treating PCa.

LCZ696 Protects against Diabetic Cardiomyopathy-Induced Myocardial Inflammation, ER Stress, and Apoptosis through Inhibiting AGEs/NF-κB and PERK/CHOP Signaling Pathways

The present study is designed to determine the effect of LCZ696 on DCM in rats and investigate the underlying mechanism involved. Diabetes was induced by feeding rats with a high-fat diet for six weeks following a single injection of STZ (30 mg/kg). Diabetic rats were divided into three groups (n = 10). LCZ696 and valsartan treatment was started two weeks after diabetic induction and continued for eight weeks. At the end of the treatment, serum and cardiac tissues were analyzed by RT-PCR, Western blot, and ELISA kits. LCZ696 and valsartan ameliorated DCM progression by inhibiting AGEs formation at activity levels; pro-apoptotic markers (BAX/Bcl2 ratio and caspase-3) in mRNA and protein expressions, the NF-κB at mRNA; and protein levels associated with the restoration of elevated proinflammatory cytokines such as the TNF-α, IL-6, and IL-1β at the activity level. Furthermore, LCZ696 and valsartan contribute to restoring the induction of ER stress parameters (GRP78, PERK, eIF2a, ATF4, and CHOP) at mRNA and protein levels. LCZ696 and valsartan attenuated DCM by inhibiting the myocardial inflammation, ER stress, and apoptosis through AGEs/NF-κB and PERK/CHOP signaling cascades. Collectively, the present results reveal that LCZ696 had a more protective solid effect against DCM than valsartan.

In vivo and in vitro studies evaluating the chemopreventive effect of metformin on the aryl hydrocarbon receptor-mediated breast carcinogenesis

Metformin (MET) is a clinically used anti-hyperglycemic agent that shows activities against chemically-induced animal models of cancer. A study from our laboratory showed that MET protectes against 7, 12-dimethylbenz[a]anthracene (DMBA)-induced carcinogenesis in vitro human non-cancerous epithelial breast cells (MCF10A) via activation of the aryl hydrocarbon receptor (AhR). However, it is unclear whether MET can prevent the initiation of breast carcinogenesis in an in vivo rat model of AhR-induced breast carcinogenesis. Therefore, the main aims of this study are to examine the effect of MET on protecting against rat breast carcinogenesis induced by DMBA and to explore whether this effect is medicated through the AhR pathway. In this study, treatment of female rats with DMBA initiated breast carcinogenesis though inhibiting apoptosis and tumor suppressor genes while inducing oxidative DNA damage and cell cycle proliferative markers. This effect was associated with activation of AhR and its downstream target genes; cytochrome P4501A1 (CYP1A1) and CYP1B1. Importantly, MET treatment protected against DMBA-induced breast carcinogenesis by restoring DMBA effects on apoptosis, tumor suppressor genes, DNA damage, and cell proliferation. Mechanistically using in vitro human breast cancer MCF-7 cells, MET inhibited breast cancer stem cells spheroids formation and development by DMBA, which was accompanied by a proportional inhibition in CYP1A1 gene expression. In conclusion, the study reports evidence that MET is an effective chemopreventive therapy for breast cancer by inhibiting the activation of CYP1A1/CYP1B1 pathway in vivo rat model.

Metformin attenuates V-domain Ig suppressor of T-cell activation through the aryl hydrocarbon receptor pathway in Melanoma: In Vivo and In Vitro Studies

Melanoma is an aggressive skin cancer with a high rate of metastasis to other organs. Recent studies specified the overexpression of V-domain Ig suppressor of T-cell activation (VISTA) and Aryl Hydrocarbon Receptor (AHR) in melanoma. Metformin shows anti-tumor activities in several cancer types. However, the mechanism is unclear. This study aims to investigate the inhibitory effect of metformin on VISTA via AHR in melanoma cells (CHL-1, B16) and animal models. VISTA and AHR levels were assessed by qPCR, Western blot, immunofluorescence microscope, flow cytometry, and immunohistochemistry. Here, metformin significantly decreased VISTA and AHR levels in vitro and in vivo. Furthermore, metformin inhibited all AHR-regulated genes. VISTA levels were dramatically inhibited by AHR modulations using shRNA and αNF, confirming the central role of AHR in VISTA. Finally, melanoma cells were xenografted in C57BL/6 and nude mice. Metformin significantly reduced the tumor volume and growth rate. Likewise, VISTA and AHR-regulated protein levels were suppressed in both models. These findings demonstrate for the first time that VISTA is suppressed by metformin and identified a new regulatory mechanism through AHR. The data suggest that metformin could be a new potential therapeutic strategy to treat melanoma patients combined with targeted immune checkpoint inhibitors.

Taxifolin suppresses the malignant progression of gastric cancer by regulating the AhR/CYP1A1 signaling pathway

The development of novel approaches for the treatment of gastric cancer is of utmost importance. Taxifolin (Tax) has been reported to possess biological activities against a number of types of cancer. The objective of the present study was to examine the effects of Tax on gastric cancer and to explore its potential mechanisms of action. For this purpose, AGS and NCI‑N87 cells, as well as BALB/c mice with gastric cancer cell‑derived tumors were treated with Tax. Cell Counting Kit‑8 and colony formation assays were performed to detect cell viability and proliferation, respectively. Wound‑healing and Transwell assays were also conducted to determine the cell migratory and invasive abilities, respectively. Western blot analysis was performed to determine protein expression in vitro and in vivo. The results revealed that Tax significantly inhibited the viability, proliferation, migration and invasion of gastric cancer cells through the aryl hydrocarbon receptor (AhR)/cytochrome P450 1A1 (CYP1A1) signaling pathway. SB203580, an AhR agonist, partly abolished the inhibitory effects of Tax on gastric cancer cell viability, proliferation, migration and invasion. In addition, Tax also suppressed tumor growth in vivo. Collectively, the present study demonstrated that Tax significantly suppressed the tumor characteristics of gastric cancer. Tax may thus prove to be a potential therapeutic strategy for gastric cancer.

Eugenol-Induced Autophagy and Apoptosis in Breast Cancer Cells via PI3K/AKT/FOXO3a Pathway Inhibition

The use of natural compounds is promising in approaches to prevent and treat cancer. The long-term application of most currently employed chemotherapy techniques has toxic side effects. Eugenol, a phenolic phytochemical extracted from certain essential oils, has an anti-cancer effect. The modulation of autophagy can promote either the survival or apoptosis of cancer cells. Triple-negative (MDA-MB-231) and HER2 positive (SK-BR-3) breast cancer cell lines were treated with different doses of eugenol. Apoptosis was detected by a flow-cytometry technique, while autophagy was detected by acridine orange. Real-time PCR and Western blot assays were applied to investigate the effect of eugenol on the gene and protein expression levels of autophagy and apoptotic genes. Treating cells with different concentrations of eugenol significantly inhibited cell proliferation. The protein levels of AKT serine/threonine kinase 1 (AKT), forkhead box O3 (FOXO3a), cyclin dependent kinase inhibitor 1A (p21), cyclin-dependent kinase inhibitor (p27), and Caspase-3 and -9 increased significantly in Eugenol-treated cells. Eugenol also induced autophagy by upregulating the expression levels of microtubule-associated protein 1 light chain 3 (LC3) and downregulating the expression of nucleoporin 62 (NU p62). Eugenol is a promising natural anti-cancer agent against triple-negative and HER2-positive breast cancer. It appears to work by targeting the caspase pathway and by inducing autophagic cell death.

Influence of the Aryl Hydrocarbon Receptor Activating Environmental Pollutants on Autism Spectrum Disorder

Autism spectrum disorder (ASD) is an umbrella term that includes many different disorders that affect the development, communication, and behavior of an individual. Prevalence of ASD has risen exponentially in the past couple of decades. ASD has a complex etiology and traditionally recognized risk factors only account for a small percentage of incidence of the disorder. Recent studies have examined factors beyond the conventional risk factors (e.g., environmental pollution). There has been an increase in air pollution since the beginning of industrialization. Most environmental pollutants cause toxicities through activation of several cellular receptors, such as the aryl hydrocarbon receptor (AhR)/cytochrome P450 (CYPs) pathway. There is little research on the involvement of AhR in contributing to ASD. Although a few reviews have discussed and addressed the link between increased prevalence of ASD and exposure to environmental pollutants, the mechanism governing this effect, specifically the role of AhR in ASD development and the molecular mechanisms involved, have not been discussed or reviewed before. This article reviews the state of knowledge regarding the impact of the AhR/CYP pathway modulation upon exposure to environmental pollutants on ASD risk, incidence, and development. It also explores the molecular mechanisms involved, such as epigenesis and polymorphism. In addition, the review explores possible new AhR-mediated mechanisms of several drugs used for treatment of ASD, such as sulforaphane, resveratrol, haloperidol, and metformin.

Betulin ameliorates 7,12-dimethylbenz(a)anthracene-induced rat mammary cancer by modulating MAPK and AhR/Nrf-2 signaling pathway

The aim of the present study is to explore the preventive efficacy of betulin (BE) in 7,12-dimethylbenz(a)anthracene (DMBA)-administered mammary cancer by modulating Ahr/Nrf2 signaling in experimental models. The mammary cancer was stimulated by the addition of DMBA (25 mg/kg/b.Wt) mixed in 1 ml of vehicle solution (sunflower oil and saline 1:1) through subcutaneous injection. The DMBA-exposed mammary tumor models showed low bodyweight, elevated quantities of lipid peroxidation molecules (TBARS and LOOH), and low enzymatic (GPx, SOD, and CAT), and nonenzymatic (GSH, vitamin C, and vitamin E) antioxidant activities in plasma and mammary tissues. Moreover, histopathological studies confirmed that invasive ductal carcinoma was observed in DMBA-induced mammary tissue of the experimental model. Dietary oral supplementation of BE prevents the loss of bodyweight, overproduces lipid peroxidation, and restores the antioxidant activities in DMBA-exposed experimental animals. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a crucial antioxidant protein that involves preventing numerous cancers. Therefore, Nrf2-associated signaling concern is a significant target for preventing mammary cancer. This study observed an increased expression of MAPKs, Keap1, ARNT, AhR, and CYP1A1, whereas decreased expression of HO-1 and Nrf2 in DMBA-induced cancer-bearing experimental animals. The oral supplementation of BE effectively modulates the expression of MAPKs, AhR/Nrf2-associated protein expressions in DMBA-exposed experimental animals. This current study concluded that BE is a strong antioxidant, which triggers the MAPKs-mediated oxidative stress and inhibits proliferative markers by restoring the activity of Nrf2 signaling.

Epigenetic Regulation of Cancer Stem Cells by the Aryl Hydrocarbon Receptor Pathway

Compelling evidence has demonstrated that tumor bulk comprises distinctive subset of cells generally referred as cancer stem cells (CSCs) that have been proposed as a strong sustainer and promoter of tumorigenesis and therapeutic resistance. These distinguished properties of CSCs have raised interest in understanding the molecular mechanisms that govern the maintenance of these cells. Numerous experimental and epidemiological studies have demonstrated that exposure to environmental toxins such as the polycyclic aromatic hydrocarbons (PAHs) is strongly involved in cancer initiation and progression. The PAH-induced carcinogenesis is shown to be mediated through the activation of a cytosolic receptor, aryl hydrocarbon receptor (AhR)/Cytochrome P4501A pathway, suggesting a possible direct link between AhR and CSCs. Several recent studies have investigated the role of AhR in CSCs self-renewal and maintenance, however the molecular mechanisms and particularly the epigenetic regulations of CSCs by the AhR/CYP1A pathway have not been reviewed before. In this review, we first summarize the crosstalk between AhR and cancer genetics, with a particular emphasis on the mechanisms relevant to CSCs such as Wnt/β-catenin, Notch, NF-κB, and PTEN-PI3K/Akt signaling pathways. The second part of this review discusses the recent advances and studies highlighting the epigenetic mechanisms mediated by the AhR/CYP1A pathway that control CSC gene expression, self-renewal, and chemoresistance in various human cancers. Furthermore, the review also sheds light on the importance of targeting the epigenetic pathways as a novel therapeutic approach against CSCs.

Genome-Protecting Compounds as Potential Geroprotectors

Throughout life, organisms are exposed to various exogenous and endogenous factors that cause DNA damages and somatic mutations provoking genomic instability. At a young age, compensatory mechanisms of genome protection are activated to prevent phenotypic and functional changes. However, the increasing stress and age-related deterioration in the functioning of these mechanisms result in damage accumulation, overcoming the functional threshold. This leads to aging and the development of age-related diseases. There are several ways to counteract these changes: 1) prevention of DNA damage through stimulation of antioxidant and detoxification systems, as well as transition metal chelation; 2) regulation of DNA methylation, chromatin structure, non-coding RNA activity and prevention of nuclear architecture alterations; 3) improving DNA damage response and repair; 4) selective removal of damaged non-functional and senescent cells. In the article, we have reviewed data about the effects of various trace elements, vitamins, polyphenols, terpenes, and other phytochemicals, as well as a number of synthetic pharmacological substances in these ways. Most of the compounds demonstrate the geroprotective potential and increase the lifespan in model organisms. However, their genome-protecting effects are non-selective and often are conditioned by hormesis. Consequently, the development of selective drugs targeting genome protection is an advanced direction.

Anticancer mechanisms of metformin: A review of the current evidence

Metformin, a US Food and Drug Administration-approved "star" drug used for diabetes mellitus type 2, has become a topic of increasing interest to researchers due to its anti-neoplastic effects. Growing evidence has demonstrated that metformin may be a promising chemotherapeutic agent, and several clinical trials of metformin use in cancer treatment are ongoing. However, the anti-neoplastic effects of metformin and its underlying mechanisms have not been fully elucidated. In this review, we present the newest findings on the anticancer activities of metformin, and highlight its diverse anticancer mechanisms. Several clinical trials, as well as the limitations of the current evidence are also demonstrated. This review explores the crucial roles of metformin and provides supporting evidence for the repurposing of metformin as a treatment of cancer.

Kynurenine signaling through the aryl hydrocarbon receptor: Implications for aging and healthspan

The tryptophan metabolite kynurenine increases with aging and inflammation, and appears to contribute directly to the development and progression of several age-related conditions. Kynurenine is now known to signal through the aryl hydrocarbon receptor (Ahr) to modulate levels of reactive oxygen species (ROS). The Ahr promoter region contains several sites for NF-kB binding, indicating that inflammation is a key factor modulating Ahr expression. Furthermore, kynurenine activation of Ahr is observed to stimulate expression of the enzyme IDO1, which generates kynurenine by degrading tryptophan, representing a positive feedback loop that may link inflammation with ROS production. On the other hand, the antioxidant system-inducing transcription factor Nrf2 can be stimulated by Ahr, and Nrf2 can itself activate Ahr expression. The balance between pro- and antioxidant functions of Ahr mediated by kynurenine may therefore regulate healthy versus unhealthy aging in different tissues and organ systems. Potential therapeutic approaches to target this pathway include exercise to alter kynurenine production or molecules such as metformin or resveratrol that may suppress Ahr activity.

Safety of Metformin in Psoriasis Patients With Diabetes Mellitus: A 17-Year Population-Based Real-World Cohort Study

CONTEXT

The safety of metformin usage by diabetic psoriasis patients is unclear.

OBJECTIVE

To investigate the real-world safety of metformin in psoriatic patients with type 2 diabetes mellitus (T2DM).

DESIGN

We used the National Health Insurance Research Database to perform a cohort study. Based on metformin and other antidiabetic agent prescriptions, we divided all psoriasis patients with T2DM into the metformin group and the nonmetformin group. The outcomes included all-cause mortality, severe psoriasis, hospitalization due to psoriasis, and any cause for readmission.

RESULTS

The metformin group (n = 5520) and the nonmetformin group (n = 3062) did not significantly differ in the risk of all-cause mortality [hazard ratio (HR) 1.08; 95% CI, 0.90 to 1.30], severe psoriasis (HR, 0.95; 95% CI, 0.80 to 1.09), psoriasis-related admission (HR, 1.32; 95% CI, 0.90 to 1.93), and any-cause readmission (HR, 0.99; 95% CI, 0.90 to 1.11). The dose-response analysis found no significant increase in the risk of severe psoriasis and psoriasis-related admission, even with more than 80 defined daily doses or 1000 mg daily dose of metformin prescribed (P for linear trend > 0.05).

CONCLUSION

Metformin can be prescribed for diabetic psoriasis patients without safety concerns.

Metformin as an adjuvant in breast cancer treatment

Breast cancer is one of the most common malignancies in females. It is an etiologically complex disease driven by a multitude of cellular pathways. The proliferation and spread of breast cancer is intimately linked to cellular glucose metabolism, given that glucose is an essential cellular metabolic substrate and that insulin signalling has mitogenic effects. Growing interest has focused on anti-diabetic agents in the management of breast cancer. Epidemiologic studies show that metformin reduces cancer incidence and mortality among type 2 diabetic patients. Preclinical in vitro and in vivo research provides intriguing insight into the cellular mechanisms behind the oncostatic effects of metformin. This article aims to provide an overview of the mechanisms in which metformin may elicit its anti-cancerous effects and discuss its potential role as an adjuvant in the management of breast cancer.

Anti-metastatic and anti-proliferative activity of eugenol against triple negative and HER2 positive breast cancer cells

Background

Eugenol is a natural phenolic compound and possesses anticancer and antibacterial activities. Breast cancer is a major global health problem, and most of the chemotherapeutic agents are highly toxic with long-term side effects. Therefore, this study aimed to explore the possibility of using eugenol as an anti-metastatic and anti-proliferative agent against MDA-MB-231 and SK-BR-3 breast cancer cells.

Methods

Breast cancer cell lines MDA-MB-231 and SK-BR-3 were treated with eugenol and cell proliferation was measured using a real-time cell electronic sensing system. Annexin V analysis with flow cytometry was used to detect the effect of eugenol on cell death. In MDA-MB-231 and SK-BR-3 cells, metastatic potential after eugenol treatment was examined using a wound-healing assay. Real-time PCR was used to study the effect of eugenol on the expression of anti-metastatic genes such as MMP2, MMP9, and TIMP-1, and genes involved in apoptosis including Caspase3, Caspase7, and Caspase9.

Results

Treatment with 4 μM and 8 μM eugenol for 48 h significantly inhibited cell proliferation of MDA-MB-231, with an inhibition rate of 76.4%, whereas 5 μM and 10 μM of eugenol for 48 h significantly inhibited the proliferation of SK-BR-3 cells with an inhibition rate of 68.1%. Eugenol-treated cells showed significantly decreased MMP2 and MMP9 expression and an insignificant increase in TIMP1 expression in HER2 positive and triple negative breast cancer cells. Eugenol significantly increased the proportion of MDA-MB-231 and SK-BR-3 cells in late apoptosis and increased the expression of Caspase3, Caspase7, and Caspase9.

Conclusion

To the best of our knowledge, this is the first study to describe the anti-metastatic effect of eugenol against MDA-MB-231 and SK-BR-3 breast cancer cell lines.

Metformin inhibits IgE- and aryl hydrocarbon receptor-mediated mast cell activation in vitro and in vivo

Metformin, an anti-diabetic drug, possesses anti-inflammatory property beyond its glucose-lowering activity, but its regulatory effect on mast cells and allergic responses remains unknown, wherein the aryl hydrocarbon receptor (AhR)-ligand axis is critical in controlling mast cell activation. Herein, we provide evidence supporting the role of metformin in modulating mast cell activation by FcεR1-, AhR-mediated signaling or their combination. Metformin at relatively low doses was shown to suppress FcεR1-mediated degranulation, IL-13, TNF-α and sphingosine-1-phosphate (S1P) secretion in murine bone marrow-derived mast cells (BMMCs). In contrast, metformin at the same doses potently inhibited all parameters in mast cells stimulated with an AhR ligand, 5,11-dihydroindolo[3,2-b]carbazole-6-carbaldehyde (FICZ). Further, metformin was shown to inhibit FcεR1- and AhR-mediated passive cutaneous anaphylaxis (PCA) in vivo, reversible by a S1P receptor 2 antagonist, JTE-013. Using AhR reporter cells, Huh7-DRE-Luc cells, a human mast cell line, HMC-1, and BMMCs, metformin's inhibitory effect was mediated through the suppression of FICZ-induced AhR activity, calcium mobilization and ROS generation. Notably, FICZ-mediated oxidation of S1P lyase (S1PL) and its reduced activity were reversed by metformin, resulting in decreased levels of S1P. Collectively, these results suggested the potential utility of metformin in treating allergic diseases, particularly in cases with comorbid type II diabetes mellitus.

7,12-Dimethylbenz[α]anthracene increases cell proliferation and invasion through induction of Wnt/β-catenin signaling and EMT process

7,12-Dimethylbenz[α]anthracene (DMBA) is a hazardous component present in polluted environments. DMBA has been used as an experimental tool for in vivo tumor formation owing to its carcinogenic effects, but the detailed molecular mechanism of DMBA has not been fully established. To comprehend the carcinogenic mechanism of DMBA, we explored its effects in the breast cancer cell lines, MCF-7 and MDA-MB-231, and the cervical cancer cell line, HeLa. Cell viability assay and measurement of a proliferation marker showed that DMBA markedly increased cancer cell proliferation. Furthermore, morphological observations and wound healing assays in nontumorigenic MCF-10A cells and trans-well invasion assays in cancer cells following DMBA treatment revealed that DMBA induced cell migration and invasion. To reveal the molecular mechanism of DMBA, we investigated the effects of DMBA on the epithelial-mesenchymal transition (EMT) process and Wnt/β-catenin signaling, a critical pathway for cell proliferation that was reported to correlate with the EMT process, by using quantitative RT-PCR (qPCR), western blot analysis, and confocal microscopy. Consequently, we found that DMBA increased cancer cell proliferation and invasion through the promotion of EMT-inducing factors and β-catenin. Especially, it was revealed in promoter activity assay using mutated luciferase vectors on transcription factor-binding sites that TWIST1 is promoted by DMBA through induction of STAT3-mediated promoter activation. To further elucidate the detailed mechanism of DMBA, we aimed to identify the key regulator of its carcinogenic action. DMBA was shown to significantly upregulate the expression of specificity protein 1 (Sp1), a transcription factor, and the carcinogenic effects of DMBA were blocked via the suppression or interruption of Sp1 activity. In conclusion, our data suggested that DMBA induced carcinogenic effects through activation of Wnt/β-catenin signaling and the EMT process by upregulating Sp1 activity.

Inhibition of Mid-chain HETEs Protects Against Angiotensin II-induced Cardiac Hypertrophy

Recent data demonstrated the role of CYP1B1 in cardiovascular disease. It was, therefore, necessary to examine whether the inhibition of CYP1B1 and hence inhibiting the formation of its metabolites, using 2,4,3',5'-tetramethoxystilbene (TMS), would have a cardioprotective effect against angiotensin II (Ang II)-induced cardiac hypertrophy. For this purpose, male Sprague Dawley rats were treated with Ang II with or without TMS (300 μg/kg every third day i.p.). Thereafter, cardiac hypertrophy and the formation of mid-chain HETEs and arachidonic acid were assessed. In vitro, RL-14 cells were treated with Ang II (10 μM) in the presence and absence of TMS (0.5 μM). Then, reactive oxygen species, mitogen-activated protein kinase phosphorylation levels, and nuclear factor-kappa B-binding activity were determined. Our results demonstrated that TMS protects against Ang II-induced cardiac hypertrophy as indicated by the improvement in cardiac functions shown by the echocardiography as well as by reversing the increase in heart weight to tibial length ratio caused by Ang II. In addition, the cardioprotective effect of TMS was associated with a significant decrease in cardiac mid-chain HETEs levels. Mechanistically, TMS inhibited reactive oxygen species formation, the phosphorylation of ERK1/2, p38 mitogen-activated protein kinase, and the binding of p65 NF-κB.

Metformin and melatonin inhibit DMBA-induced mammary tumorigenesis in rats fed a high-fat diet

The data from in-vitro and in-vivo studies show that both peroral antidiabetic metformin (MF) and pineal hormone melatonin (MT) inhibit the growth of many cancers, including breast cancer. However, most in-vivo studies used standard-type diet with low fat content. Therefore, in this study, we evaluated the chemopreventive effect of MF and MT in an in-vivo model of breast cancer in rats on a high-fat diet (10% of total fat). Mammary carcinogenesis was induced by 7,12-dimethylbenz[a]anthracene (DMBA) in female Sprague-Dawley rats. Chemoprevention with MF (administered in a diet, 0.2%) and MT (administered in tap water, 20 mg/l) was induced 20 days before the carcinogen administration through the termination of the experiment (14 weeks after carcinogen administration). Tumor growth parameters were analyzed together with histopathological examination and immunohistochemical detection of KI67 (proliferation marker), caspase-3, BAX, BCL-2 (apoptosis markers), and CD24 and CD44 (cancer stem cell markers) in mammary tumor samples. The combination of chemopreventive agents decreased tumor incidence by 29%. Cumulative tumor volume was lower in all groups treated with chemoprevention. Histopathology did not show significant changes in high-grade/low-grade tumor ratio. Immunohistochemistry showed increased expression of BAX in the combination group, and caspase-3 expression increased in both MT and combination groups. MT, and particularly the MF and MT combination, inhibited DMBA-induced mammary tumor growth in rats by apoptosis stimulation in cancer cells. Our results indicate that MT supplements in patients treated with MF may have a considerable effect on the incidence of breast cancer.

Allyl isothiocyanate, a potent chemopreventive agent targets AhR/Nrf2 signaling pathway in chemically induced mammary carcinogenesis

In the present study, we investigated the effect of allyl isothiocyanate (AITC) on liver detoxification signaling pathway in 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary carcinogenesis. Mammary tumor was induced by a single dose of DMBA (25 mg/rat) injected subcutaneously near the mammary gland in Sprague-Dawley rats. DMBA-alone-treated rats show an increased synthesis of phase I detoxification enzymes, lipid peroxidative markers, liver marker enzymes, and lipid profiles whereas, depletion of phase II detoxification enzymes and antioxidants in rat liver tissues. Oral administration of AITC restored the levels of biochemical markers in DMBA-treated rats. Furthermore, histopathological results also confirmed that AITC protects DMBA-mediated hepatocellular damage. We also observed that AITC treatment significantly downregulates AhR and upregulates the expression of Nrf2 in DMBA-treated rats. The binding efficacy of AITC with AhR and Nrf2 analysis by molecular docking studies reveals that AITC has strong interaction with AhR and Nrf2 proteins through hydrogen and hydrophobic interactions. Thus, AITC prevents DMBA-induced mammary carcinogenesis via inhibition of phase I and induction of phase II detoxification enzymes by modulating AhR/Nrf2 signaling pathway.

Aryl hydrocarbon receptor/cytochrome P450 1A1 pathway mediates breast cancer stem cells expansion through PTEN inhibition and β-Catenin and Akt activation

BACKGROUND

Breast cancer stem cells (CSCs) are small sub-type of the whole cancer cells that drive tumor initiation, progression and metastasis. Recent studies have demonstrated a role for the aryl hydrocarbon receptor (AhR)/cytochrome P4501A1 pathway in CSCs expansion. However, the exact molecular mechanisms remain unclear.

METHODS

The current study was designed to a) determine the effect of AhR activation and inhibition on breast CSCs development, maintenance, self-renewal, and chemoresistance at the in vitro and in vivo levels and b) explore the role of β-Catenin, PI3K/Akt, and PTEN signaling pathways. To test this hypothesis, CSC characteristics of five human breast cancer cells; SKBR-3, MCF-7, and MDA-MB231, HS587T, and T47D treated with AhR activators or inhibitor were determined using Aldefluor assay, side population, and mammosphere formation. The mRNA, protein expression, cellular content and localization of the target genes were determined by RT-PCR, Western blot analysis, and Immunofluorescence, respectively. At the in vivo level, female Balb/c mice were treated with AhR/CYP1A1 inducer and histopathology changes and Immunohistochemistry examination for target proteins were determined.

RESULTS

The constitutive mRNA expression and cellular content of CYP1A1 and CYP1B1, AhR-regulated genes, were markedly higher in CSCs more than differentiating non-CSCs of five different human breast cancer cells. Activation of AhR/CYP1A1 in MCF-7 cells by TCDD and DMBA, strong AhR activators, significantly increased CSC-specific markers, mammosphere formation, aldehyde dehydrogenase (ALDH) activity, and percentage of side population (SP) cells, whereas inactivation of AhR/CYP1A1 using chemical inhibitor, α-naphthoflavone (α-NF), or by genetic shRNA knockdown, significantly inhibited the upregulation of ALDH activity and SP cells. Importantly, inactivation of the AhR/CYP1A1 significantly increased sensitization of CSCs to the chemotherapeutic agent doxorubicin. Mechanistically, Induction of AhR/CYP1A1 by TCDD and DMBA was associated with significant increase in β-Catenin mRNA and protein expression, nuclear translocation and its downstream target Cyclin D1, whereas AhR or CYP1A1 knockdown using shRNA dramatically inhibited β-Catenin cellular content and nuclear translocation. This was associated with significant inhibition of PTEN and induction of total and phosphorylated Akt protein expressions. Importantly, inhibition of PI3K/Akt pathway by LY294002 completely blocked the TCDD-induced SP cells expansion. In vivo, IHC staining of mammary gland structures of untreated and DMBA (30 mg/kg, IP)- treated mice, showed tremendous inhibition of PTEN expression accompanied with an increase in the expression p-Akt, β-Catenin and stem cells marker ALDH1.

CONCLUSIONS

The present study provides the first evidence that AhR/CYP1A1 signaling pathway is controlling breast CSCs proliferation, development, self-renewal and chemoresistance through inhibition of the PTEN and activation of β-Catenin and Akt pathways.

The Aryl Hydrocarbon Receptor Relays Metabolic Signals to Promote Cellular Regeneration

While sensing the cell environment, the aryl hydrocarbon receptor (AHR) interacts with different pathways involved in cellular homeostasis. This review summarizes evidence suggesting that cellular regeneration in the context of aging and diseases can be modulated by AHR signaling on stem cells. New insights connect orphaned observations into AHR interactions with critical signaling pathways such as WNT to propose a role of this ligand-activated transcription factor in the modulation of cellular regeneration by altering pathways that nurture cellular expansion such as changes in the metabolic efficiency rather than by directly altering cell cycling, proliferation, or cell death. Targeting the AHR to promote regeneration might prove to be a useful strategy to avoid unbalanced disruptions of homeostasis that may promote disease and also provide biological rationale for potential regenerative medicine approaches.

Targeting P-glycoprotein expression and cancer cell energy metabolism: combination of metformin and 2-deoxyglucose reverses the multidrug resistance of K562/Dox cells to doxorubicin

P-glycoprotein (P-gp) is one of the major obstacles to efficiency of cancer chemotherapy. Here, we investigated whether combination of metformin and 2-deoxyglucose reverses the multidrug resistance (MDR) of K562/Dox cells and tried to elucidate the possible mechanisms. The combination of metformin and 2-deoxyglucose selectively enhanced the cytotoxicity of doxorubicin against K562/Dox cells. Metformin was not a substrate of P-gp but suppressed the elevated level of P-gp in K562/Dox cells. The downregulation of P-gp may be partly attributed to the inhibition of extracellular signal-regulated kinase pathway. The addition of 2-deoxyglucose to metformin initiated a strong metabolic stress in both K562 and K562/Dox cells. Combination of metformin and 2-deoxyglucose inhibited glucose uptake and lactate production in K562 and K562/Dox cells leading to a severe depletion in ATP and a enhanced autophagy. Above all, P-gp substrate selectively aggravated this ATP depletion effect and increased cell apoptosis in K562/Dox cells. In conclusion, metformin decreases P-gp expression in K562/Dox cells via blocking phosphorylation of extracellular signal-regulated kinase. P-gp substrate increases K562/Dox cell apoptosis via aggravating ATP depletion induced by combination of metformin and 2-deoxyglucose. Our observations highlight the importance of combination of metformin and 2-deoxyglucose in reversing multidrug resistance.