Department of Medicine, Division of Environmental Medicine, New York University Grossman School of Medicine, New York, NY 10010, USA.
Biomolecules. 2023 Jan 6;13(1):116. doi: 10.3390/biom13010116.
Cadmium (Cd) is a heavy metal found in cigarette smoke, as well as in air and drinking water due to agricultural and industrial activities, and it poses a health risk to the general population. Prolonged low-dose Cd exposure via inhalation or ingestion causes lung and kidney cancers in humans and in animal models. While high doses of Cd exposure are correlated with the occupational setting and are cytotoxic, low doses of Cd are mainly correlated with exposure in the general population and induce carcinogenesis. The mechanism by which Cd-exposed cells overcome calcium chelation and induce malignant transformation remains unclear. This study examines how cells exposed to low doses of Cd survive loss of E-cadherin cell-cell adhesion via activation of the epidermal growth factor receptor (EGFR) and signal transducer and activator of transcription 5 (STAT5), which work to upregulate genes associated with survival and proliferation. To demonstrate the role of Cd in EGFR/STAT5 activation, we exposed two epithelial cell lines, BEAS-2B and HEK293, to two different doses (0.4 µM and 1.6 µM) of Cadmium chloride hemipentahydrate (CdCl·2.5HO) that are environmentally relevant to levels of Cd found in food and cigarettes for 24 h (hours) and 9 weeks (wks). When comparing cells treated with Cd with control cells, the Cd treated cells exhibited faster proliferation; therefore, we studied activation of EGFR via the STAT5 pathway using immunofluorescence (IF) for protein expression and localization and, in addition, RT-qPCR to examine changes in EGFR/STAT5 inducible genes. Our results showed an increase in EGFR and phosphorylated EGFR (p-EGFR) protein, with 1.6 µM of Cadmium having the highest expression at both 24-hour (hr) and 9-week (wk) exposures. Moreover, the IF analysis also demonstrated an increase of STAT5 and phosphorylated STAT5 (pSTAT5) in both short-term and long-term exposure, with 0.4 µM having the highest expression at 24 h. Finally, via Western blot analysis, we showed that there was a dose-dependent decrease in E-cadherin protein expression and increased N-cadherin in cells treated with low doses of Cd. These data demonstrate that epithelial cells can overcome Cd-mediated toxicity via activation of EGFR pathway to induce cell proliferation and survival and promote epithelial to mesenchymal transition.
镉（Cd）是一种重金属，存在于香烟烟雾中，也存在于空气和饮用水中，这对一般人群构成了健康风险。通过吸入或摄入，长时间低剂量的 Cd 暴露会导致人类和动物模型中的肺癌和肾癌。虽然高剂量的 Cd 暴露与职业环境有关，且具有细胞毒性，但低剂量的 Cd 主要与一般人群的暴露有关，会诱导致癌作用。暴露于 Cd 的细胞如何克服钙螯合并诱导恶性转化的机制尚不清楚。本研究通过激活表皮生长因子受体（EGFR）和信号转导和转录激活因子 5（STAT5），检查了细胞如何在细胞间黏附蛋白 E-钙黏蛋白丧失的情况下存活，这些因子可上调与存活和增殖相关的基因。为了证明 Cd 在 EGFR/STAT5 激活中的作用，我们将两种上皮细胞系 BEAS-2B 和 HEK293 暴露于两种不同剂量（0.4 µM 和 1.6 µM）的二水合氯化镉（CdCl·2.5HO）中，这两个剂量与食物和香烟中发现的 Cd 水平相关，暴露时间为 24 小时（hrs）和 9 周（wks）。与对照细胞相比，用 Cd 处理的细胞表现出更快的增殖；因此，我们使用免疫荧光（IF）研究了通过 STAT5 途径的 EGFR 激活，并进行了 RT-qPCR 检查 EGFR/STAT5 诱导基因的变化。我们的结果表明 EGFR 和磷酸化 EGFR（p-EGFR）蛋白表达增加，在 24 小时（hr）和 9 周（wk）暴露时，1.6 µM 的 Cd 表达最高。此外，IF 分析还表明，在短期和长期暴露中，STAT5 和磷酸化 STAT5（pSTAT5）均增加，在 24 小时（h）时，0.4 µM 的表达最高。最后，通过 Western blot 分析，我们表明，用低剂量 Cd 处理的细胞中，E-钙黏蛋白蛋白表达呈剂量依赖性下降，N-钙黏蛋白增加。这些数据表明，上皮细胞可以通过激活 EGFR 途径来克服 Cd 介导的毒性，从而诱导细胞增殖和存活，并促进上皮间质转化。
