Phthalates Stimulate the Epithelial to Mesenchymal TransitionThrough an HDAC6-Dependent Mechanism in Human BreastEpithelial Stem Cells

Abstract

Phthalates are environmental hormone-like molecules that are associated with breast cancer risk and are involved in metastasis, a process that requires the epithelial-mesenchymal transition (EMT). However, few studies have addressed the potential effects of phthalates on stem cells. Here we tested the hypothesis that phthalates such as butyl benzyl phthalate and di-n-butyl phthalate induce EMT in R2d cells, a stem cell-derived human breast epithelial cell line that is responsive to estradiol for tumor development. We observed that phthalates induced EMT as evidenced by morphological changes concomitant with increased expression of mesenchymal markers and decreased expression of epithelial markers. Molecular mechanism studies revealed that histone deacetylase 6 (HDAC6) is required for phthalate-induced cell migration and invasion during EMT in vitro and metastasis into the lungs of nude mice. We also constructed a series of mutant HDAC6 promoter fragments and found that the transcription factor AP-2a plays a novel role in regulating the HDAC6 promoter. Furthermore, phthalates stimulated estrogen receptors and triggered the downstream EGFR-PKA signaling cascade, leading to increased expression of AP-2a in the nucleus. We also observed that phthalates increased expression of the PP1/HDAC6 complex and caused Akt activation and GSK3β inactivation, leading to transcriptional activation of vimentin through the β-catenin-TCF-4/LEF1 pathway. Understanding the signaling cascades of phthalates that activate EMT through HDAC6 in breast epithelial stem cells provides the identification of novel therapeutic target for human breast cancer.

n-Butyl Benzyl Phthalate Promotes Breast Cancer Progression by Inducing Expression of Lymphoid Enhancer Factor 1

“…We and others have shown that phthalate exposure results in pronounced cell transformation, both in vitro and in tumor xenograft models [30]. In the current study, we show that the BBP-LEF1 cascade observed in R2d cells can be recapitulated in the ER-positive breast cancer cell line MCF-7.…”

Microenvironment, Oncoantigens, and Antitumor Vaccination: Lessons Learned from BALB-neuT Mice

“…It is worth noting that some of these networks seem to be regulatory keys of therapeutic resistance, such as Survivin [37], Topoisomerase II α [38], Desmoglein 2 [39], BCL2-interacting killer [40], and ribonucleotide reductase M2 polypeptide [41]. In addition, several identified proteins have a role in CSC self-renewal, which has been demonstrated in the cases of maternal embryonic leucine zipper kinase [42], transcription factor AP-2 γ [43], the microtubule associated TPX2 protein [44], and Aurora kinase A [44]. At present, our efforts are focused on the characterization of some of these targets and our final goal is the setup of new DNA vaccines that will be tested in BALB-neuT mice in association with anti-HER2 vaccination, in order to improve the vaccination's efficacy against advanced tumor and metastases.…”

Exposure to phthalate‐containing prescription drugs and the risk of colorectal adenocarcinoma: A Danish nationwide case‐control study

“…2,3 Ortho-phthalates are known to stimulate the epithelial-tomesenchymal transition necessary for cancer invasion and metastasis, mediated by histone deacetylase 6. 4 In vitro studies support a role of phthalates in mechanisms of colon carcinogenesis. Additionally, a dose-dependent effect of ortho-phthalates on aryl hydrocarbon receptor (AhR) function has been suggested.…”

“…Ortho‐phthalates are known to stimulate the epithelial‐to‐mesenchymal transition necessary for cancer invasion and metastasis, mediated by histone deacetylase 6 . In vitro studies support a role of phthalates in mechanisms of colon carcinogenesis.…”