EZH2 is regulated by ERK/AKT and targets integrin alpha2 gene to control Epithelial-Mesenchymal Transition and anoikis in colon cancer cells

摘要

Epithelial-Mesenchymal Transition is a good example of cell plasticity. In tumorigenesis, this process has been associated with metastasis. Overexpression of EZH2 has been detected in most malignant human tumors, including colorectal carcinomas. Herein, we provide evidence supporting the idea that oncogenic Epithelial-Mesenchymal Transition in colon cancer cell models is partially controlled by epigenetic factors such as the transcription regulator EZH2. Evaluation of EZH2 mRNA and protein levels revealed overexpression in cell lines with metastatic traits. Analysis of EZH2 mRNA expression was expanded in clinical samples of colon cancer, and high level of EZH2 correlates with appearance of metastasis. Furthermore, inhibition of ERK and AKT pathways in metastatic colon cancer cell lines attenuates EZH2 overexpression. EZH2 promoter analysis illustrates presence of putative AP-1 binding sites and occupancy of transcription factors such as FRA-1 and C-JUN is demonstrated here on EZH2 promoter. Abrogation of EZH2 expression impairs the ability of colon cancer cells to move associated with anoikis in three-dimensional environment. Integrin alpha2 was identified to be a novel EZH2 target by chromatin immunoprecipitation and short hairpin RNA analysis. This study proposes that activation of ERK/AKT pathways and FRA1/C-JUN induce EZH2 overexpression, which results in Integrin alpha2 silencing. Our results show how deregulation of epigenetic factors and mechanisms can affect cancer cell aggressiveness and propose EZH2 as a potential metastasis marker and/or therapeutic target for colorectal cancer treatment. (C) 2012 Elsevier Ltd. All rights reserved.