A novel role of IGFBP5 in the migration, invasion and spheroids formation induced by IGF-I and insulin in MCF-7 breast cancer cells.

PURPOSE: The insulin-like growth factor (IGF) system includes IGF-I, IGF-II insulin and their membrane receptors. IGF system also includes a family of proteins namely insulin-like growth factor-binding proteins (IGFBPs) composed for six major members (IGFBP-1 to IGFBP6), which capture, transport and prolonging half-life of IGFs. However, it has been described that IGFBPs can also have other functions. METHODS: IGFBP5 expression was inhibited by shRNAs, migration was analyzed by scratch-wound assays, invasion assays were performed by the Boyden chamber method, spheroids formation assays were performed on ultra-low attachment surfaces, expression and phosphorylation of proteins were analyzed by Western blot. RESULTS: IGFBP5 is a repressor of IGF-IR expression, but it is not a repressor of IR in MCF-7 breast cancer cells. In addition, IGFBP5 is a suppressor of migration and MMP-9 secretion induced by IGF-I and insulin, but it does not regulate invasion in MCF-7 cells. IGFBP5 also is a repressor of MCF-7 spheroids formation. However treatment with 340 nM rescues the inhibitory effect of IGFBP in the MCF-7 spheroids formation. CONCLUSION: IGFBP5 regulates IGF-IR expression, migration and MMP-9 secretion induced by IGF-I and/or insulin, and the spheroids formation in MCF-7 breast cancer cells.

Benzo[a]pyrene promotes an epithelial-to-mesenchymal transition process in MCF10A cells and mammary tumor growth and brain metastasis in female mice.

Breast cancer is the most frequent neoplasia in developed countries and the leading cause of death in women worldwide. Epithelial-to-mesenchymal transition (EMT) is a cellular process through which epithelial cells decrease or lose their epithelial characteristics and gain mesenchymal properties. EMT mediates tumor progression, because tumor cells acquire the capacity to execute the multiple steps of invasion and metastasis. Benzo[a]pyrene (B[a]P) is an environmental organic pollutant generated during the burning of fossil fuels, wood, and other organic materials. B[a]P exposition increases the incidence of breast cancer, and induces migration and/or invasion in MDA-MB-231 and MCF-7 breast cancer cells. However, the role of B[a]P in the induction of an EMT process and metastasis of mammary carcinoma cells has not been studied in detail. In this study, we demonstrate that B[a]P induces an EMT process in MCF10A mammary non-tumorigenic epithelial cells. In addition, B[a]P promotes the formation of larger tumors in Balb/cJ mice inoculated with 4T1 cells than in untreated mice and treated with dimethyl sulfoxide (DMSO). B[a]P also increases the number of mice with metastasis to brain and the total number of brain metastatic nodules in Balb/cJ mice inoculated with 4T1 cells compared with untreated mice and treated with DMSO. In conclusion, B[a]P induces an EMT process in MCF10A cells and the growth of mammary tumors and metastasis to brain in Balb/cJ mice inoculated with 4T1 cells.

Caveolae Microdomains Mediate STAT5 Signaling Induced by Insulin in MCF-7 Breast Cancer Cells.

Caveolae are small plasma membrane invaginations constituted for membrane proteins namely caveolins and cytosolic proteins termed cavins, which can occupy up to 50% of the surface of mammalian cells. The caveolae have been involved with a variety of cellular processes including regulation of cellular signaling. Insulin is a hormone that mediates a variety of physiological processes through activation of insulin receptor (IR), which is a tyrosine kinase receptor expressed in all mammalian tissues. Insulin induces activation of signal transducers and activators of transcription (STAT) family members including STAT5. In this study, we demonstrate, for the first time, that insulin induces phosphorylation of STAT5 at tyrosine-694 (STAT5-Tyr(P)694), STAT5 nuclear accumulation and an increase in STAT5-DNA complex formation in MCF-7 breast cancer cells. Insulin also induces nuclear accumulation of STAT5-Tyr(P)694, caveolin-1, and IR in MCF-7 cells. STAT5 nuclear accumulation and the increase of STAT5-DNA complex formation require the integrity of caveolae and microtubule network. Moreover, insulin induces an increase and nuclear accumulation of STAT5-Tyr(P)694 in MDA-MB-231 breast cancer cells. In conclusion, results demonstrate that caveolae and microtubule network play an important role in STAT5-Tyr(P)694, STAT5 nuclear accumulation and STAT5-DNA complex formation induced by insulin in breast cancer cells.

Bovine holo-lactoferrin inhibits migration and invasion in MDA-MB-231 breast cancer cells.

PURPOSE: Breast cancer is the most common malignancy in developed countries and the main cause of deaths in women worldwide. Lactoferrin (Lf) is an iron-binding protein constituted for a single polypeptide chain that is folded into two symmetrical lobes that bind Fe2+ or Fe3+. Lf has the ability to reversibly bind Fe3+ and is found free of Fe3+ (Apo-Lf) or associated with Fe3+ (Holo-Lf) with a different three-dimensional conformation. However, the role of bovine Apo-Lf (Apo-BLf) and bovine Holo-Lf (Holo-BLf) in the migration and invasion induced by linoleic acid (LA) and fetal bovine serum (FBS), as well as in the expression of mesenchymal and epithelial proteins in breast cancer cells has not been studied. METHODS AND RESULTS: Scratch wound assays demonstrated that Holo-BLf and Apo-BLf do not induce migration, however they differentially inhibit the migration induced by FBS and LA in breast cancer cells MDA-MB-231. Western blot, invasion, zymography and immunofluorescence confocal microscopy assays demonstrated that Holo-BLf partly inhibit the invasion, FAK phosphorylation at tyrosine (Tyr)-397 and MMP-9 secretion, whereas it increased the number and size of focal adhesions induced by FBS in MDA-MB-231 cells. Moreover, Holo-BLf induced a slight increase of E-cadherin expression in MCF-7 cells, and inhibited vimentin expression in MCF-7 and MDA-MB-231 breast cancer cells. CONCLUSION: Holo-BLf inhibits cellular processes that mediate the invasion process in breast cancer cells.

Extracellular Vesicles from Human Plasma Show a Distinctive Proteome and miRNome Profile in Patients with Severe Cutaneous Adverse Reactions.

Cutaneous drug-induced reactions are immune-mediated responses that can lead to life-threatening diseases such as drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome, and toxic epidermal necrolysis, collectively known as severe cutaneous adverse reactions (SCARs). Unfortunately, they cannot be predicted during drug development, and, at present, a prognostic biomarker is not available nor are validated in vitro assays for diagnosis. Thus, by using proteomic and microarray miRNA analysis, the cargo of extracellular vesicles obtained from SCARs patients was analyzed and correlated with the severity of the reaction. Confirmatory assays using Western blot and qRT-PCR were performed to validate findings, and bioinformatic tools were used to establish the correlation between protein and miRNAs expression between groups. The proteomic analysis showed an increase in the amount of pro-inflammatory proteins, von Willebrand factor, and C-reactive protein and a decrease in anti-inflammatory and protective proteins in the SCARs group compared with the control group. Additionally, histone protein H2A was enriched in DRESS patients. APO1 and SERPINA4 proteins, highly increased in the control group but absent in the SCARs group, are the target of several overexpressed miRNAs, suggesting that the regulation of these proteins might involve gene silencing and protein repressing mechanisms in the severe patients. According with previous reports showing its presence in plasma and T-cells, microRNA miR-18 was upregulated in extracellular vesicles obtained from the most severe patients. Determination of the unique cargo associated with different disease conditions will help to understand the pathophysiology of these complex reactions and might help to develop novel biomarkers for life-threatening iatrogenic cutaneous disease.

Linoleic acid induces secretion of extracellular vesicles from MDA-MB-231 breast cancer cells that mediate cellular processes involved with angiogenesis in HUVECs.

Extracellular vesicles (EVs) are vesicles secreted by normal and malignant cells that are implicated in tumor progression. Linoleic acid (LA) is an essential polyunsaturated fatty acid that induces migration, invasion and an increase in phospholipase D activity in breast cancer cells. In this study, we determined whether stimulation of MDA-MB-231 breast cancer cells with LA induces the secretion of EVs, which can mediate cell processes related with angiogenesis in human umbilical vein endothelial cells (HUVECs). Our findings demonstrate that treatment of MDA-MB-231 cells with 90 µM LA for 48 h induce an increase in the number of EVs released. Moreover, EVs from MDA-MB-231 stimulated with 90 µM LA induce FAK and Src activation and migration via FAK and Src activity, whereas the secretion of these EVs is through FFAR1 and FFAR4 activation in HUVECs. The EVs from MDA-MB-231 cells treated with LA also increase proliferation, invasion, MMP-9 secretion, an increase of MMP-2 secretion and formation of new tubules in HUVECs. In summary, we demonstrate, for the first time, that treatment with LA induces the release of EVs from MDA-MB-231 cells that induce cellular processes involved with angiogenesis in HUVECs.

Role of phospholipase D in migration and invasion induced by linoleic acid in breast cancer cells.

Linoleic acid (LA) is an essential and omega-6 polyunsaturated fatty acid that mediates a variety of biological processes, including migration and invasion in breast cancer cells. Phospholipase D (PLD) catalyses the hydrolysis of phosphatidylcholine to produce phosphatidic acid and choline. Increases of expression and activity of PLD are reported in several human cancers, including gastric, colorectal, renal, stomach, lung and breast. In this article, we demonstrate that LA induces an increase of PLD activity in MDA-MB-231 breast cancer cells. Particularly, PLD1 and/or PLD2 mediate migration and invasion induced by LA. Moreover, LA induces increases in number and size of spheroids via PLD activity. FFAR1 also mediates migration and invasion, whereas PLD activation induced by LA requires the activities of FFAR1, FFAR4 and EGFR in MDA-MB-231 cells. In summary, PLD plays a pivotal role in migration and invasion induced by LA in MDA-MB-231 breast cancer cells.

Insulin induces an EMT-like process in mammary epithelial cells MCF10A.

Diabetes mellitus has been related with an increased risk of breast cancer, whereas it has been suggested that links between diabetes mellitus and cancer are hyperinsulinemia, insulin resistance, hyperglycemia, and chronic inflammation induced by adipose tissue. Contribution of hyperinsulinemia to carcinogenesis is mediated through resistance to endogenous insulin and by exogenous insulin used in treatment. Epithelial to mesenchymal transition (EMT) is a process by which epithelial cells are transdifferentiated to a mesenchymal state that has been implicated in cancer progression. However, the role of insulin in EMT process has not been studied in detail. In the present study, we demonstrate that insulin induces downregulation of E-cadherin expression, accompanied with an increase of N-cadherin and vimentin expression, and an increase of MMP-2 and -9 secretions. Insulin also induces FAK activation, an increase of NFκB DNA binding activity, migration, and invasion of mammary non-tumorigenic epithelial cells MCF10A. In addition, migration requires the activity of insulin receptors and insulin-like growth factor receptor 1 (IGF1R). In summary, our results demonstrate that insulin induces an EMT-like process in MCF10A cells.

Linoleic acid induces an increased response to insulin in MDA-MB-231 breast cancer cells.

Epidemiological studies and animal models suggest a link between high levels of dietary fat intake and an increased risk of developing breast cancer. Hyperinsulinemia is a feature of obesity, diabetes, and metabolic syndrome that is associated with an increased breast cancer risk. Insulin is a hormone involved in metabolic regulation of carbohydrate. However, it is also a growth factor that mediates proliferation and migration. Linoleic acid (LA) is a fatty acid that induces migration and invasion in breast cancer cells. In the present study, we demonstrate, for the first time, that treatment with LA increases IR and IGF1R expression through a Free Fatty Acid Receptor 4 (FFAR4)-, lipooxygenases (LOXs)-, and SRC-dependent pathway in MDA-MB-231 breast cancer cells, and similarly induces an increase of IR expression in MCF-7 breast cancer cells. In addition, insulin induces tyrosine phosphorylation of IR/IGF1R and migration in MDA-MB-231 cells pretreated with LA, whereas it augments the increase in migration in MCF-7 cells pretreated with LA. Pretreatment of MDA-MB-231 cells with LA induces invasion, proliferation, and increase the MMP-9 secretion induced by insulin. In summary, our findings demonstrate that treatment with LA induces a higher response to insulin in breast cancer cells.

Migration and invasion induced by linoleic acid are mediated through fascin in MDA-MB-231 breast cancer cells.

Epidemiological studies strongly suggest an association between high levels of dietary fat intake and an increased risk of developing breast cancer. Linoleic acid (LA) is an essential omega-6 PUFA and the major fatty acid in occidental diets. In breast cancer cells, LA induces expression of plasminogen activator inhibitor-1, proliferation, migration, and invasion. Fascin is an actin crosslinker globular protein that generates actin bundles made of parallel actin filaments, which mediate formation and stability of microspikes, stress fibers, membrane ruffles, and filopodia. However, the role of fascin in migration and invasion induced by LA in MDA-MB-231 breast cancer cells remains to be studied. We demonstrate here that LA induces an increase of fascin expression in MDA-MB-231 and MCF12A mammary epithelial cells. Particularly, LA induces the formation of filopodia and lamellipodia and the localization of fascin in these actin structures in MDA-MB-231 breast cancer cells. However, LA only induces formation of microspikes and the localization of fascin in these actin structures in mammary non-tumorigenic epithelial cells MCF12A. In addition, LA induces migration, invasion, and matrix metalloproteinase-9 secretion through a fascin-dependent pathway in MDA-MB-231 cells. In summary, our findings demonstrate that fascin is required for migration and invasion induced by LA in MDA-MB-231 breast cancer cells.

Erythropoietin Induces an Epithelial to Mesenchymal Transition-Like Process in Mammary Epithelial Cells MCF10A.

Anemia is associated with chemotherapy treatment in cancer patients. Erythropoietin (EPO) has been used to treat anemia of cancer patients, because it stimulates erythropoiesis. However, treatment of breast cancer patients with EPO has been associated with poor prognosis and decrease of survival. Epithelial to mesenchymal transition (EMT) is a process by which epithelial cells are transdifferentiated to a mesenchymal state. It has been implicated in tumor progression, because epithelial cells acquire the capacity to execute the multiple steps of invasion/metastasis process. However, the role of EPO on EMT process in human mammary epithelial cells has not been studied. In the present study, we demonstrate that EPO promotes a decrease of E-cadherin expression, an increase of N-cadherin, vimentin, and Snail2 expression, activation of FAK and Src kinases and an increase of MMP-2 and MMP-9 secretions. Moreover, EPO induces an increase of NFκB DNA binding activity, an increase of binding of p50 and p65 NFκB subunits to Snail1 promoter, migration, and invasion in mammary non-tumorigenic epithelial cells MCF10A. In summary, these findings demonstrate, for the first time, that EPO induces an EMT-like process in mammary non-tumorigenic epithelial cells. J. Cell. Biochem. 118: 2983-2992, 2017. © 2017 Wiley Periodicals, Inc.

Extracellular vesicles from women with breast cancer promote an epithelial-mesenchymal transition-like process in mammary epithelial cells MCF10A.

Extracellular vesicles (EVs) mediate many stages of tumor progression including angiogenesis, escape from immune surveillance, and extracellular matrix degradation. We studied whether EVs from plasma of women with breast cancer are able to induce an epithelial-mesenchymal transition (EMT) process in mammary epithelial cells MCF10A. Our findings demonstrate that EVs from plasma of breast cancer patients induce a downregulation of E-cadherin expression and an increase of vimentin and N-cadherin expression. Moreover, EVs induce migration and invasion, as well as an increase of NFκB-DNA binding activity and MMP-2 and MMP-9 secretions. In summary, our findings demonstrate, for the first time, that EVs from breast cancer patients induce an EMT-like process in human mammary non-tumorigenic epithelial cells MCF10A.

Coffee attenuates fibrosis by decreasing the expression of TGF-ß and CTGF in a murine model of liver damage.

This study was performed to evaluate the antifibrotic properties of coffee in a model of liver damage induced by repeated administration of thioacetamide (TAA) in male Wistar rats. In this study, cirrhosis was induced by chronic TAA administration and the effects of co-administration of conventional caffeinated coffee or decaffeinated coffee (CC, DC, respectively) for 8 weeks were evaluated. TAA administration elevated serum alkaline phosphatase (AP), γ-glutamyl transpeptidase (γ-GTP) and alanine aminotransferase (ALAT), liver lipid peroxidation, collagen content, depleted liver glycogen and glutathione peroxidase (GPx) activity. Additionally increased levels of a number of proteins were detected including transforming growth factor-beta (TGF-ß), connective tissue growth factor (CTGF) and alpha-smooth muscle actin (α-SMA), and matrix metalloproteinase (MMP)-2, 9 and 13. Coffee suppressed most of the changes produced by TAA. Histopathological analysis was in agreement with biochemical and molecular findings. These results indicate that coffee attenuates experimental cirrhosis; the action mechanisms are probably associated with its antioxidant properties and mainly by its ability to block the elevation of the profibrogenic cytokine TGF-ß and its downstream effector CTGF. Various components of coffee that have been related to such a favorable effect include caffeine, coffee oils kahweol, cafestol and antioxidant substances; however, no definite evidence for the role of these components has been established. These results support earlier findings suggesting a beneficial effect of coffee on the liver. However, more basic clinical studies must be performed to confirm this hypothesis.

Bisphenol A increases the size of primary mammary tumors and promotes metastasis in a murine model of breast cancer.

Triple negative breast cancer (TNBC) is a subtype of breast tumor characterized for the absence of estrogen and progesterone receptors expression and low HER2/neu expression. Bisphenol A (BPA) is an endocrine disrupting chemical with estrogenic activity that has been associated with increasing rates of breast cancer. Moreover, BPA is a solid organic synthetic chemical employed in the manufacture of many consumer products, epoxy resins and polycarbonate plastics including baby bottles, containers for food and beverages, and the lining of beverage cans. The G-protein-coupled estrogen receptor (GPER) is activated by endogenous hormones and synthetic ligands, such as BPA. GPER is expressed in TNBC cells and its expression is associated with larger tumor size, metastasis and worse survival prognosis. In breast cancer cells, BPA induces activation of signal transduction pathways that mediates migration and invasion via GPER in human TNBC MDA-MB-231 cells. In this study, we demonstrate that BPA induces an increase of GPER expression and its translocation from cytosol to cytoplasmic membrane, metalloproteinase (MMP)-2 and MMP-9 secretion, migration and invasion in murine TNBC 4T1 cells. In a murine TNBC model "in vivo" using 4T1 cells, BPA induces the formation of mammary tumors with more weight and volume, and an increase in the number of mice with metastasis to lung and nodules in lung compared with tumors and metastasis to lung of untreated Balb/cJ mice. In conclusion, our findings demonstrate that BPA mediates the growth of mammary primary tumors and metastasis to lung in a murine model of breast cancer.

Shotgun Proteomics of Co-Cultured Leukemic and Bone Marrow Stromal Cells from Different Species as a Preliminary Approach to Detect Intercellular Protein Transfer.

Cellular interactions within the bone marrow microenvironment modulate the properties of subsets of leukemic cells leading to the development of drug-resistant phenotypes. The intercellular transfer of proteins and organelles contributes to this process but the set of transferred proteins and their effects in the receiving cells remain unclear. This study aimed to detect the intercellular protein transfer from mouse bone marrow stromal cells (OP9 cell line) to human T-lymphoblasts (CCRF-CEM cell line) using nanoLC-MS/MS-based shotgun proteomics in a 3D co-culture system. After 24 h of co-culture, 1513 and 67 proteins from human and mouse origin, respectively, were identified in CCRF-CEM cells. The presence of mouse proteins in the human cell line, detected by analyzing the differences in amino acid sequences of orthologous peptides, was interpreted as the result of intercellular transfer. The transferred proteins might have contributed to the observed resistance to vincristine, methotrexate, and hydrogen peroxide in the co-cultured leukemic cells. Our results suggest that shotgun proteomic analyses of co-cultured cells from different species could be a simple option to get a preliminary survey of the proteins exchanged among interacting cells.

Extracellular vesicles from MDA-MB-231 breast cancer cells stimulated with insulin-like growth factor 1 mediate an epithelial-mesenchymal transition process in MCF10A mammary epithelial cells.

Insulin-like growth factor-1 (IGF-1) plays an important role in function and development of the mammary gland. However, high levels of IGF-1 has been associated with an increased risk of breast cancer development. Epithelial-mesenchymal transition (EMT) is a process where epithelial cells lose their epithelial characteristics and acquire a mesenchymal phenotype, which is considered one of the most important mechanisms in cancer initiation and promotion of metastasis. Extracellular vesicles (EVs) are released into the extracellular space by different cell types, which mediate intercellular communication and play an important role in different physiological and pathological processes, such as cancer. In this study, we demonstrate that EVs from MDA-MB-231 breast cancer cells stimulated with IGF-1 (IGF-1 EVs) decrease the levels of E-cadherin, increase the expression of vimentin and N-cadherin and stimulate the secretion of metalloproteinase-9 in mammary non-tumorigenic epithelial cells MCF10A. IGF-1 EVs also induce the expression of Snail1, Twist1 and Sip1, which are transcription factors involved in EMT. Moreover, IGF-1 EVs induce activation of ERK1/2, Akt1 and Akt2, migration and invasion. In summary, we demonstrate, for the first time, that IGF-1 EVs induce an EMT process in mammary non-tumorigenic epithelial cells MCF10A.

Extracellular vesicles from blood of breast cancer women induce angiogenic processes in HUVECs.

Breast cancer is the most frequent malignancy among women in developed countries and the main cause of death related to cancer in women worldwide. Extracellular vesicles (EVs) are vesicles with a variable size enclosed within a phospholipid bilayer that contain a variety of molecules with biological activity. Cancer cells release EVs that induce proliferation, escape from apoptosis, reprogramming energy metabolism, invasion and metastasis. In this study we studied whether EV fractions deprived of platelet EVs from breast cancer women (BC EVs) can mediate cell processes related with angiogenesis in human umbilical vein endothelial cells (HUVECs). Our findings demonstrate that BC EVs enhance migration, invasion and formation of new tubules in HUVECs, compared with EV fractions deprived of platelet EVs from healthy women (Ctrl EVs). In summary, we demonstrate, for the first time, that BC EVs induce cellular processes in HUVECs that participate in angiogenesis.

Role of Src/FAK in migration and invasion mediated by extracellular vesicles from MDA-MB-231 cells stimulated with linoleic acid.

Linoleic acid (LA) is the most abundant polyunsaturated fatty acid in occidental diets, which mediate a variety of processes in human breast cancer cells, including migration and invasion. Extracellular vesicles (EVs) are vesicles released from endosomes and plasma membrane that are composed of a variety of molecules, including proteins, nucleic acids and lipids. EVs from cancer cells promote processes related with cancer progression. In the present study, we demonstrate that treatment of MDA-MB-231 cells with EVs from MDA-MB-231 cells stimulated with LA (LA EVs) promote migration and invasion via Src activity. LA EVs induce activation of FAK via Src activity and of Src and Akt2. LA EVs also induce the assembly of focal adhesions and MMP-9 secretion. These findings demonstrate that LA EVs mediate an autocrine and/or paracrine Src/FAK signaling pathway to promote migration and invasion.

Effect on Human Vascular Endothelial Cells of Au Nanoparticles Synthesized from Vitex mollis.

A green method for synthesizing gold nanoparticles is proposed using hydroethanolic extract of Vitex mollis fruit (Vm extract) as a reducer and stabilizer. The formation of gold nanoparticles synthesized with Vm extract (AuVmNPs) was monitored by measuring the ultraviolet-visible spectra. The morphology and crystalline phase were determined using scanning electron microscopy, X-ray diffraction, and high-resolution transmission electron microscopy. Synthesized nanoparticles were generally spherical, and the size distribution obtained by transmission electron microscopy shows two populations with mean sizes of 12.5 and 22.5 nm. Cell viability assay using MTT and cellular apoptosis studies using annexin V on human umbilical vein endothelial cells (HUVECs) and the human mammary epithelial cell line (MCF10A) indicate that AuVmNPs have low toxicity. Cell migration tests indicate that AuVmNPs significantly inhibit HUVEC cell migration in a dose-dependent manner. The evaluation of the localization of AuVmNPs in HUVECs using confocal laser scanning microscopy indicates that nanoparticles penetrate cells and are found in the cytosol without preferential distribution and without entering the nucleus. The inhibitory effect on cellular migration and low toxicity suggest AuVmNPs as appropriate candidates in future studies of antiangiogenic activity.

Activation of the Aryl Hydrocarbon Receptor (AHR) induces human glutathione S transferase alpha 1 (hGSTA1) expression.

Glutathione S-transferases (GSTs) are a key enzyme superfamily involved in the detoxification and cytoprotection of a wide variety of xenobiotics, such as carcinogens, anticancer drugs, environmental toxicants, and endogenously produced free radicals. In the liver, the hGSTA1 isoenzyme is the most abundant and catalyzes the glutathione conjugation of a wide range of electrophiles and has been the principal GST responsible for xenobiotic detoxification. Given the critical role of this enzyme in several cellular processes, particularly cell detoxification, understanding the molecular mechanisms underlying the regulation of hGSTA1 expression is critical. Therefore, the aim of the present study was to investigate whether AHR is involved in the modulation of hGSTA1 gene expression and to characterize the molecular mechanism through which AHR exerts this regulation. Two xenobiotic response elements (XREs) were located at -602 bp and -1030 bp from the transcription start site at the hGSTA1 gene promoter. After treatment of HepG2 cells with beta-naphthoflavone (ß-NF), an AHR agonist, induction of hGSTA1 mRNA was observed. This effect was mediated by the recruitment of AHR to the hGSTA1 gene promoter and its transactivation, as indicated by the ChIP, EMSA and luciferase activity assays. The increase in hGSTA1 transcription regulated by AHR also resulted in enhanced levels of hGSTA1 protein and activity. Taken together, our data suggest that AHR ligands have the potential to modify xenobiotic and endobiotic metabolism mediated by hGSTA1, thereby altering the detoxification of xenobiotics, steroidogenesis and the efficacy of chemotherapeutic agents.