Triiodothyronine (T3) upregulates the expression of proto-oncogene TGFA independent of MAPK/ERK pathway activation in the human breast adenocarcinoma cell line, MCF7

ABSTRACT Objective: To verify the physiological action of triiodothyronine T3 on the expression of transforming growth factor α (TGFA) mRNA in MCF7 cells by inhibition of RNA Polymerase II and the MAPK/ERK pathway Materials and methods: The cell line was treated with T3 at a physiological dose (10−9M) for 10 minutes, 1 and 4 hour (h) in the presence or absence of the inhibitors, α-amanitin (RNA polymerase II inhibitor) and PD98059 (MAPK/ERK pathway inhibitor). TGFA mRNA expression was analyzed by RT-PCR. For data analysis, we used ANOVA, complemented with the Tukey test and Student t-test, with a minimum significance of 5%. Results: T3 increases the expression of TGFA mRNA in MCF7 cells in 4 h of treatment. Inhibition of RNA polymerase II modulates the effect of T3 treatment on the expression of TGFA in MCF7 cells. Activation of the MAPK/ERK pathway is not required for T3 to affect the expression of TGFA mRNA. Conclusion: Treatment with a physiological concentration of T3 after RNA polymerase II inhibition altered the expression of TGFA. Inhibition of the MAPK/ERK pathway after T3 treatment does not interfere with the TGFA gene expression in a breast adenocarcinoma cell line.

摘要 目的：通过抑制RNA聚合酶II（RNA Polymerase II）与丝裂原活化蛋白激酶/细胞外调节蛋白激酶（MAPK/ERK）通路，验证三碘甲状腺原氨酸T3对MCF7细胞内转化生长因子α（TGFA）mRNA表达的生理学作用。材料与方法：将MCF7细胞系在添加或不添加抑制剂α-鹅膏蕈碱（RNA聚合酶II抑制剂）与PD98059（MAPK/ERK通路抑制剂）的条件下，以生理剂量（10⁻⁹M）的T3分别处理10分钟、1小时及4小时。采用逆转录聚合酶链式反应（RT-PCR）分析TGFA mRNA的表达水平。数据分析采用方差分析（ANOVA），辅以图基检验（Tukey test）与学生t检验（Student t-test），最小显著性水平设定为5%。结果：经4小时T3处理后，MCF7细胞中TGFA mRNA的表达水平升高。RNA聚合酶II的抑制可调控T3处理对MCF7细胞内TGFA表达的影响。MAPK/ERK通路的激活并非T3影响TGFA mRNA表达的必要条件。结论：在RNA聚合酶II被抑制后施加生理浓度T3处理，可改变TGFA的表达。在该乳腺腺癌细胞系中，T3处理后抑制MAPK/ERK通路不会对TGFA基因的表达产生干扰。