Cadmium and Proliferation in Human Uterine Leiomyoma Cells: Evidence of a Role for EGFR/MAPK Pathways but Not Classical Estrogen Receptor Pathways

Abstract

Background:It has been proposed that cadmium (Cd) is an environmental “metalloestrogen” and that its action is mediated via the estrogen receptor (ER). Cd mimics the effects of estrogen in the rat uterus, and blood Cd concentrations positively correlate with ER levels in uteri of women with fibroids.Objectives:In the present study we explored whether Cd could stimulate proliferation of estrogen-responsive human uterine leiomyoma (ht-UtLM) cells and uterine smooth muscle cells (ht-UtSMCs) through classical interactions with ERα and ERβ, or by nongenomic mechanisms.Methods:We used estrogen response element (ERE) reporters, phosphorylated receptor tyrosine kinase arrays, Western blot analysis, estrogen binding, and cell proliferation assays to evaluate the effects of Cd on ht-UtLM cells and ht-UtSMCs.Results:Cd stimulated growth of both cell types at lower concentrations and inhibited growth at higher concentrations (≥ 50 μM). Cd did not significantly bind to ERα or ERβ, nor did it show transactivation in both cell types transiently transfected with ERE reporter genes. However, in both cells types, Cd (0.1 μM and 10 μM) activated p44/42 MAPK (ERK1/2), and a MAPK inhibitor (PD98059) abrogated Cd-induced cell proliferation. Cd in ht-UtLM cells, but not in ht-UtSMCs, activated the growth factor receptors EGFR, HGFR, and VEGF-R1 upstream of MAPK. Additional studies in ht-UtLM cells showed that AG1478, an EGFR inhibitor, abolished Cd-induced phosphorylation of EGFR and MAPK.Conclusions:Our results show that low concentrations of Cd stimulated cell proliferation in estrogen-responsive uterine cells by nongenomic activation of MAPK, but not through classical ER-mediated pathways.Citation:Gao X, Yu L, Moore AB, Kissling GE, Waalkes MP, Dixon D. 2015. Cadmium and proliferation in human uterine leiomyoma cells: evidence of a role for EGFR/MAPK pathways but not classical estrogen receptor pathways. Environ Health Perspect 123:331–336; http://dx.doi.org/10.1289/ehp.1408234

Requirement of ERα and basal activities of EGFR and Src kinase in Cd-induced activation of MAPK/ERK pathway in human breast cancer MCF-7 cells

“…The activation of EGFR in response to Cd appears to be cell type dependent as it was reported to occur in human uterine leiomyoma and smooth muscle cells (Gao et al, 2015). In an oral carcinoma cell line Ca9-22, however, Kuribayashi et al (2004) reported the activation of ERK by insulin like growth factor 1 (IGF-1) without EGFR phosphorylation.…”

Involvement of Notch1 signaling in malignant progression of A549 cells subjected to prolonged cadmium exposure

“…Although the possible involvement of IGF-1 cannot be excluded, a Notch1-mediated mechanism independent of ligand binding remains to be clarified. In addition, cadmium exposure-induced activation of other receptor-type tyrosine kinases, including the epidermal growth factor receptor (22,50), might contribute to the subsequent activation of the Akt/ERK pathway. A and B, prolonged 10 M CdCl 2 -exposed BEAS-2B cells (Cd) were transfected with control siRNA, Notch1 siRNA-1, or Notch1 siRNA-2.…”

Cadmium promotes the proliferation of triple-negative breast cancer cells through EGFR-mediated cell cycle regulation

“…Also in human airway epithelial cells, another study reported that Cd treatment caused reactive oxygen species generation, upregulating HIF-1 and VEGF expression which is involved in tumorigenesis and angiogenesis (Jing et al, 2012). Growth factor receptors such as EGFR, HGFR, and VEGFR-R1, but not ERα, were responsible for Cd-induced MAPK activation in human uterine cancer leiomyoma cells (Gao et al, 2015). Activation of EGFR and downstream phosphorylation of Src, ERK and AKT has also been reported in rat mesangial cells upon Cd treatment (Xiao et al, 2009).…”

“…Lack of involvement of ERα in other types of cells has also been demonstrated. For example, in leiomyoma cancer ht-UtLM cells, Cd was reported to neither bind to ERα or β, or stimulate ER-induced transcriptional activity (Gao et al, 2015). Moreover, in a transgenic estrogen reporter mouse model, Cd did not induce estrogen-like effect via classical ER signaling (Ali et al, 2010).…”

“…It is interesting to note that while the MCF7 cells are positive for ER, PR, and HER2, these cells have only low level of EGFR. Indeed, in recent years Cd has been implicated in EGFR-mediated MAPK activation in liver, lung and uterine cancer cells (Kundu et al, 2011; Ali et al, 2015; Gao et al, 2015). Therefore, the present study was designed to further delineate the role of EGFR in Cd-induced cell signaling and cell growth.…”