Evi1 Transcriptionally Represses Slug To Regulate Epithelial-Mesenchymal Transition (Emt) In Human Colon Cancer

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Ecotropic viral integration site-1 (EVI1) is an oncogenic transcription factor that is frequently implicated in hematological malignancies and in some solid tumors. Deregulated expression of EVI1 impairs several pathways including proliferation, differentiation, apoptosis and cell cycle through different mechanisms in different cell types. EVI1 was found to be overexpressed in 53% of human colorectal cancer samples, 100% of colon adenocarcinoma samples, 100% of human colon cancer cell lines and its presence might affect disease progression and sensitivity to chemotherapy. To investigate the stage specific expression pattern of EVI1 in colon cancer patient samples, we analyzed two of the publicly available microarray datasets (GEO database) of colon cancer patients and observed that although EVI1 is upregulated in the initial stage of the disease, the expression level decreases with the progression of the disease. In cancer cells loss of epithelial adhesion molecule E-cadherin is considered to be a fundamental event in EMT. To decipher whether EVI1 is involved in EMT, we checked five transcription factors (SLUG, SNAIL, TWIST, ZEB1 and ZEB2) which controls the expression of E-cadherin in cancer cells. Significant negative correlation was observed between the expression levels of EVI1 and all the above transcription factors in colon cancer patient samples. Recently it was shown by using ChIP sequencing that EVI1 target SLUG and SNAIL in SKOV3 cells. To understand whether EVI1 directly binds to both SLUG and SNAIL, we did an in silico analysis and searched for EVI1 binding site(s) in the functional promoter region of both SLUG and SNAIL. Although we did not observe any binding site in SNAIL promoter region; we observed two EVI1 binding sites in the SLUG promoter region. To validate the predicted target sites in vivo, we did a ChIP assay and found that EVI1 binds to one of the site and not both of them. To determine the transcriptional regulation, we cloned the promoter region of SLUG (-1100 bp) in pGL3 vector and did luciferase assay, which revealed that EVI1 significantly represses SLUG activity in EVI1 transfected cells. Analysis of gene expression databases corroborates the above finding and shows that EVI1 negatively regulates SLUG expression in each stage of the disease as well as in colon cancer cell lines. We have worked on the functional aspects of the binding in terms of EMT which will be presented in the poster. Citation Format: Kasturi B. Nayak, Soumen Chakraborty. EVI1 transcriptionally represses SLUG to regulate epithelial-mesenchymal transition (EMT) in human colon cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 465. doi:10.1158/1538-7445.AM2014-465