The role of CCCTC binding factor (CTCF) in epithelial to mesenchymal transition (EMT)

Abstract

The process of Epithelial to Mesenchymal transition (EMT) plays a major role in cancer metastasis. TGF‐β or EGF signaling pathways can trigger EMT, which involves a cell state transition from an attached, epithelial state to a migratory, mesenchymal phenotype. In addition, massive reorganization of chromatin occurs during EMT, coupled with significant gene expression changes. However, the underlying cause for what triggers these chromatin structure changes remains unknown. The well‐studied transcription factor CTCF is known to regulate the 3D structure of chromatin, and reorganize the genome. Recently, it was shown in Drosophila cells that CTCF recruits Smad proteins to their gene targets following addition of TGF‐β. EMT master regulatory protein SNAIL is among the key targets of Smad proteins. Therefore, we hypothesized that CTCF plays a role in TGF‐β‐induced EMT, both at the transcriptional level, and at the genome architectural level, leading to acquisition of an invasive phenotype.To test our hypothesis, we induced EMT in normal murine mammary gland (NMuMG) cells followed by chromatin immunoprecipitation (ChIP), to determine CTCF enrichment at the SNAIL promoter. We found TGF‐β, but not EGF, dependent enrichment of CTCF at the promoter and upstream regions of SNAIL relative to the control‐untreated cells. Correspondingly, we noted a TGF‐β dependent increase in expression of SNAIL mRNA, which is diminished when coupled with siRNA knockdown of CTCF. Further, CTCF is associated with the promoter and upstream regions of the SNAIL gene in metastatic cancer cell lines with high endogenous SNAIL expression. Taken together, we propose a role for CTCF in direct transcriptional regulation of genes involved in EMT. We are currently investigating the functional role of CTCF in EMT.Support or Funding InformationThis work was supported by award 5P20GM104360 from the National Institutes of Health to AD.