转录因子FOXM1剪接异构体在乳腺癌EMT过程中的初步研究

谭拥军++陈含笑��

摘 要：探究转录因子FOXM1不同的剪接异构体对乳腺癌EMT过程中的影响.采用基因工程方法分别构建了表达FOXM1B-EGFP和FOXM1C-EGFP两种 FOXM1剪接异构体真核表达质粒，并将其转染进乳腺癌细胞，采用RT-PCR和Western印迹检测细胞样本中FOXM1剪接异构体的表达和EMT相关基因表达，同时采用transwell检测高表达不同FOXM1剪接异构体细胞的侵袭和迁移能力.成功构建了FOXM1B-EGFP和FOXM1C-EGFP真核表达质粒.外源FOXM1B在乳腺癌间质型细胞的表达高于上皮型细胞，并主要存在于细胞核内，且高表达FOXM1B 能够显著促进乳腺癌细胞的侵袭和EMT过程.外源FOXM1C在乳腺癌上皮型细胞中的表达高于间质型细胞，并且在细胞核和细胞质中均有表达，高表达FOXM1C能够显著抑制细胞的侵袭和EMT过程.实验结果表明，在乳腺癌细胞中，FOXM1B主要存在于细胞核内，FOXM1C在细胞核和细胞质中均有表达.本研究预示FOXM1B和FOXM1C对乳腺癌细胞EMT过程发挥不同的影响.

关键词：细胞粘附；FOXM1B；FOXM1C；乳腺癌； EMT

中图分类号：Q279 文献标识码：A

A Preliminary Study of Transcription Factor FOXM1

Isoforms in Breast Cancer EMT Process

TAN Yong-jun，CHEN Han-xiao

（College of Biology， Hunan Univ， Changsha， Hunan 410082， China）

Abstract：To explore the impact of different transcription factor FOXM1 isoforms in breast cancer EMT process， the eukaryotic expression plasmids for two FOXM1 isoforms， FOXM1B-EGFP and FOXM1C-EGFP， were constructed and transfected into breast cancer cells. The expression levels of FOXM1 isoforms and EMT related genes in the cells were detected with RT-PCR and Western blot. The migration ability of the cells overexpressing the FOXM1 isoforms was measured with the transwell test. The FOXM1B-EGFP and FOXM1C-EGFP eukaryotic expression plasmids were successfully constructed. We found that the levels of exogenous FOXM1B in mesenchymal cells were higher than those in epithelial cells， and it was mainly located in the nucleus. The high levels of FOXM1B expression significantly stimulated the invasion of breast cancer cells and EMT process. The levels of exogenous FOXM1C in epithelial cells were higher than those in mesenchymal cells， and they were expressed in both the nucleus and the cytoplasm. The high levels of FOXM1C expression inhibited the invasion of breast cancer cells and EMT process. FOXM1B was located mainly in the nucleus of cells and FOXM1C was expressed in both the nucleus and the cytoplasm of cells. The research has indicated that FOXM1B and FOXM1C play different roles in the process of EMT of breast cancer cells.

Key words：cell adhesion； FOXM1B；FOXM1C；breast cancer；EMT

FOXM1（Forkhead box protein M1）是叉头框（Forkhead box，Fox）转录因子家族中的成员，又称为Trident，HFH-11，Win，MPP-2等，定位于 12p13-3 号染色体，由十个外显子组成[ 1].FOXM1的蛋白表达存在着A，B 和C 3种剪接异构体：FOXM1A 比FOXM1B多两个外显子，不具有转录活性，在细胞中表达很低；FOXM1C比FOXM1B多一个外显子，和FOXM1B一样具有转录活性，且在肿瘤组织中有高表达，但在某些方面具有不同的生物学功能[ 2-3]；FOXM1B主要在癌细胞中高表达，而FOXM1C在正常细胞和癌细胞中均有高表达[ 4].上皮间质转化（Epithelial to mesenchymal transition，EMT）是指上皮细胞失去极性和细胞与细胞之间的连接点，经过细胞骨架重排、发生类似纤维……