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|Other Titles:||Effects of Arsenics on Cell Growth and Estrogen Receptor-α Expression in MCF-7 Breast Cancer Cells|
Department of Life Science, NTNU
|Abstract:||無機砷是一種環境中常見的污染物及人類的致癌物質。近年來，有報導認為無機砷是藉由動情素的模式引起生理變化。本研究目的是在證明亞砷酸鈉（sodium arsenite, 三價砷，As(3)）及砷酸鈉（sodium arsenate, 五價砷，As(5)）是否具有干擾動情素對MCF-7人類乳腺腺腫瘤細胞的作用。由細胞增生實驗結果顯示：當藥物處理濃度小於1μM As(3)或小於10μM As(5)時，可促進細胞增生；高於此二濃度的處理則抑制細胞增生。低劑量的0.1~1 μM As(3)或1~10 μM As(5)/24小時處理，在6天的觀察中，細胞有持續增生的趨勢。外加500nM動情素拮抗劑(ICI182, 780)協同處理時，可將單獨處理As(3)、As(5)及17β-estradiol（雌二醇，E2）所誘發的細胞增生抑制。以西方轉法漬法(Western blotting)分析動情素受體α(estrogen receptor α, ER α)蛋白質的表現量，發現低劑量的0.1~1μM As(3)及1~40 μM As(5)處理均會使細胞的ERα蛋白質的表現量下降。細胞以ERα抗體免疫螢光染色，可發現0.5μM As(3)及1nM E2處理組的細胞整體ERα亮度較控制組弱；單一細胞的ERα螢光呈現擴散狀分布，E2與控制組二者細胞核與細胞質都有ERα分布，然而在As(3)處理組，ERα主要分部於細胞質中，在細胞核則無。在進行As(3)與動情素競爭結合動情素受體之實驗，發現0.1、0.5、1μM As(3)與ERα的結合比為28％、35％、48％，顯示As(3)能與動情素受體結合，且呈劑量效應。上述實驗結果得知低劑量的As(3)及As(5)處理MCF-7細胞會造成細胞增生、降低ERα的表現及能與ERα結合，顯示無機砷可能透過動情素的模式引起細胞生理作用。|
Inorganic arsenics, are one of widely dispersed environmental pollutants and well-documented human carcinogens. Previous reports indicated that inorganic arsenic might somehow act through an estrogenic mode of action. In this study, effects of sodium arsenite (trivalent) and sodium arsenate (pentavalent) on cytotoxicity, cell proliferation and the expression of estrogen receptor α (ER α) in breast adenocarcinoma MCF-7 cells were examined. The preliminary results showed that the inhibiting threshold concentrations of sodium arsenite and sodium arsenate on cell growth were at 1μM and 10μM, respectively, whereas their concentrations lower than inhibiting threshold concentrations promoted cell growth instead of cell toxicity. Time course studies on cells treated with 0.1~1μM sodium arsenite and 1~10μM sodium arsenate for 24 h, and observed consecutive six days without drugs, MCF-7 cells proliferation exhibited continuous increase. Cotreated with drugs and estrogen antagonist (ICI 182,780), MCF-7 cell proliferations were completely inhibited. Data of Western blotting showed that the expression of ER α were decreased in cells treated with low dose of sodium arsenite and sodium arsenate. Immunocytochemical studies with fluorescent microscopy illustrated that ERα displayed a diffusion distribution in cytoplasm and were more concentrated within nucleus of control cell and E2-treated cells. In arsenic-treated cells, the ER α only displayed in cytoplasm. Whole-cell competitive estrogen-receptor binding assay demonstrated that 0.1, 0.5 and 1μM sodium arsenite could bind with 28%, 35% and 48% in ER respectively. Based on the results, MCF-7 cells treated with a low dose sodium arsenite and sodium arsenate increased cell proliferation, lowered the ability of ER α expression and binding to estrogen receptor that strongly suggested inorganic arsenics induce physiological effects through a estrogen model.
|Appears in Collections:||生物學報|
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