Regulation of Estrogen Sulfotransferase Expression by Confluence of MCF10A Breast Epithelial Cells: Role of the Aryl Hydrocarbon Receptor

Abstract

Estrogen sulfotransferase (SULT1E1) catalyzes the sulfonation of estrogens, which limits estrogen mitogenicity. We recently reported that SULT1E1 expression is low in preconfluent MCF10A human breast epithelial cells but increases when the cells become confluent. Pulse-chase labeling experiments with 5-bromouridine demonstrated that the confluence-mediated increase in SULT1E1 expression was due to increased mRNA synthesis. Because aryl hydrocarbon receptor (AhR) activation has been shown to suppress SULT1E1 expression and loss of cell-cell contact has been shown to activate the AhR in other cell types, we tested whether the confluence-associated changes in SULT1E1 expression were mediated by the AhR. Relative to confluent MCF10A cells, preconfluent cells had higher levels of CYP1A1 mRNA and greater activation of an AhR-responsive luciferase reporter, demonstrating that the AhR was active in the preconfluent cells. AhR and aryl hydrocarbon receptor nuclear translocator mRNA and protein levels were also higher in preconfluent than in confluent cultures. Treatment of preconfluent cells with the AhR antagonist, 3Ј-methoxy-4Ј-nitroflavone (MNF), or AhR knockdown significantly increased SULT1E1 expression. MCF10A cells stably transfected with a luciferase reporter containing ϳ7 kilobases of the SULT1E1 5Ј-flanking region showed both MNF-and confluence-inducible luciferase expression. Preconfluent cells transiently transfected with the reporter showed both MNF treatment-and AhR knockdown-mediated luciferase induction, but mutation of a computationally predicted dioxin response element (DRE) at nucleotide (nt) Ϫ3476 did not attenuate these effects. These results demonstrate that SULT1E1 expression in MCF10A cells is transcriptionally regulated by confluence through a suppressive action of the AhR, which is not mediated through a DRE at nt Ϫ3476.

Breast cancer pathogenesis is linked to the intra-tumoral estrogen sulfotransferase (hSULT1E1) expressions regulated by cellular redox dependent Nrf-2/NFκβ interplay

“…When the breast cells switch to a proliferative state, a lessening of cell-cell contact causes activation of AhR activity and suppression of SULT1E1 expression in tumor as found in our studies (Fig. 3), resulting in increased active estrogen levels in the breast microenvironment [74], interestingly it was found that arsenic-induced AhR activation and -enhanced CYP1A1 expression can be further increased by a pro-oxidant, buthionine-(S,R)sulfoximine, and suppressed by antioxidants, such as N-acetylcysteine and catalase [75] leading to the conclusion that AhR is active under oxidative stress which may suppress SULT1E1 expression.…”

Regulation of Cytosolic Sulfotransferases in Models of Human Hepatocyte Development

“…Effects of Lipid-and Xenobiotic-Sensing Receptor Activators on SULT Expression in HepaRG Cells. To identify nuclear signaling pathways that regulate SULT expression in the HepaRG model of human liver cell differentiation, cells were treated for 48 hours with activators of the AhR and several lipid-and xenobiotic-sensing nuclear receptors that have been reported to regulate SULT expression in other human cell systems (Song et al, 2001;Fang et al, 2005Fang et al, , 2007Jiang et al, 2005;Fu et al, 2011;Rondini et al, 2014;Barrett et al, 2016;Dubaisi et al, 2016). Both confluent and differentiated HepaRG cells were treated to consider the possibility that cells in the two stages could differ in their responses due to differences in their content of transcriptional machinery.…”

“…SULT expression is regulated by lipid-and xenobiotic-sensing receptors, including aryl hydrocarbon receptor (AhR), constitutive androstane receptor, pregnane X receptor (PXR), liver X receptor (LXR), farnesoid X receptor (FXR), peroxisome proliferator-activated receptors (PPARs), and vitamin D receptor (VDR) in a species-and tissue-specific manner (Echchgadda et al, 2004a,b;Fang et al, 2005Fang et al, , 2007Jiang et al, 2005;Fu et al, 2011;Kodama et al, 2011;Sueyoshi et al, 2011). Most studies of human SULT regulation have been performed using primary cultures of adult human hepatocytes (Fang et al, 2005(Fang et al, , 2007Uppal et al, 2007), or hepatic or extrahepatic cell lines (Song et al, 2001;Higashi et al, 2004;Jiang et al, 2005;Fu et al, 2011;Rondini et al, 2014;Barrett et al, 2016;Dubaisi et al, 2016), but none have been performed using human fetal hepatocytes or culture models of human liver cell differentiation. Consequently, little is known about the mechanisms that regulate SULT expression during human liver development.…”

SERMs Attenuate Estrogen-Induced Malignant Transformation of Human Mammary Epithelial Cells by Upregulating Detoxification of Oxidative Metabolites

“…Another group reported expression of SULT 1E1 mRNA alone in MCF-10A cells and observed both epigenetic regulation of SULT 1E1 mRNA and repression in transformed MCF-10A-derived cells (39). There is some evidence to suggest that SULT 1E1 gene transcription is mediated via the aryl hydrocarbon receptor in MCF-10A cells (55). In addition, there may be an association between breast cancer and genetic polymorphisms in human UGT1A1, another key mediator of conjugative metabolism (56).…”