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目的探讨人乳腺癌细胞系MCF-7中叉头框转录因子M1(FOXM1)对脾酪氨酸激酶(SYK)表达的调控机制。方法从MCF-7、T47D、SK-BR3和MDA-MB-231中提取RNA和蛋白质,分别用PCR和Western blotting检测SYK的表达水平,并检测SYK基因启动子区CpG岛甲基化。在MCF-7中过表达FOXM1,采用Western blotting和实时荧光定量PCR检测FOXM1和SYK的表达。利用染色质免疫沉淀(ChIP)技术和荧光素酶报告基因检测转录因子FOXM1对SYK基因转录水平的调控作用。结果 SYK在MCF-7中呈阳性表达,而在T47D、SKBR3和MDA-MB-231中呈阴性表达;MCF-7细胞中SYK基因启动子区Cp G岛甲基化水平低于对照细胞(P<0.05)。在MCF-7中过表达FOXM1能下调SYK表达,在SK-BR3细胞系中沉默FOXM1基因能激活SYK表达。ChIP结果显示FOXM1直接参与调控SYK的转录;基因沉默FOXM1激活SYK基因启动子活性,过表达FOXM1抑制SYK基因启动子的活性。结论在人乳腺癌细胞系MCF-7中,SYK是FOXM1的靶基因,FOXM1可能通过调节SYK的表达来调控乳腺癌的发生发展。
Objective To investigate the regulatory mechanism of forkhead box transcription factor M1 (FOXM1) on the expression of spleen tyrosine kinase (SYK) in human breast cancer cell line MCF-7. Methods RNA and protein were extracted from MCF-7, T47D, SK-BR3 and MDA-MB-231. The expression of SYK was detected by PCR and Western blotting, and the methylation of CpG island in SYK gene promoter region was detected. FOXM1 was overexpressed in MCF-7, FOXM1 and SYK were detected by Western blotting and real-time fluorescence quantitative PCR. Using chromatin immunoprecipitation (ChIP) and luciferase reporter gene detection of transcription factor FOXM1 SYK gene transcriptional regulation. Results SYK was positive in MCF-7 and negative in T47D, SKBR3 and MDA-MB-231. The methylation of CpG island in SYK gene promoter region in MCF-7 cells was lower than that in control cells <0.05). Overexpression of FOXM1 in MCF-7 down-regulated SYK expression and silencing of FOXM1 in SK-BR3 cell line activated SYK expression. ChIP results showed that FOXM1 directly involved in the regulation of SYK transcription; gene silencing FOXM1 activates SYK gene promoter activity, overexpression of FOXM1 inhibits SYK gene promoter activity. Conclusion SYK is the target gene of FOXM1 in human breast cancer cell line MCF-7. FOXM1 may regulate the occurrence and development of breast cancer by regulating the expression of SYK.