Abstract 3888: DCLK1 is part of an EMT feedback loop and promotes colorectal cancer cell invasion and drug resistance
Authors: Qu Dongfeng , Weygant Nathaniel , Berry William L. , May Randal , Chandrakesan Parthasarathy , Tomasek James J. , Sureban Sripathi M. , Houchen Courtney , Ge Yang , Yao Jiannan , An Guangyu , Bannerman-Menson Edwin 
Published: July 2017

Abstract
Colorectal cancer (CRC) is the third leading cause of cancer death in the U.S., with only a 6% 5-yr survival rate for stage IV disease. Its spread and acquisition of resistance to chemotherapy, which are fueled by the epithelial-mesenchymal transition (EMT) process and supported by tumor stem cells (TSCs), are major challenges to improving patient outcomes. New therapies that target stemness and EMT are desperately needed to prevent or delay metastasis and improve patient survival. Recently doublecortin-like kinase 1 (DCLK1) has been definitively proven to mark TSCs in CRC by two independent groups. Previous studies have demonstrated that DCLK1 is a prognostic factor in CRC and that targeted downregulation or inhibition of DCLK1 results in decreased CRC proliferation, migration, invasion, and other anti-oncogenic effects. However, the effect of overexpression of DCLK1 and its kinase active mutant on CRC has not been assessed. In this study, we investigate the correlative role of EMT and DCLK1 expression in CRC progress. Human colon cancer cells (HCT116) were infected with Lentivirus containing wild type DCLK1 or mutant DCLK1R326C cDNA sequences to overexpress DCLK1, DCLK1R326C or green fluorescent protein (GFP) cDNA sequence as control. The expressing levels of DCLK1 and EMT factors were analyzed by western blotting. The proliferative and invasive potential of these cells were compared using a MTT assay for proliferation, wound healing assay for migration, and Matrigel coated transwell assay for invasion. Knockdown of either ZEB1 or DCLK1 by specific siRNA in HCT116 cells was performed. The effects of siDCLK1 on 5-FU were performed in both HCT116 and SW480 cells using a Caspase 3/7 activity assay. Analysis of human CRC was performed using TCGA COADREAD dataset. Here we report that compared to GFP control cells, HCT116-DCLK1 and HCT116-DCLK1R326C cells exhibited a more than 20% increase in proliferation, approximately 30% increase in migration, and a 2-fold increase (p &lt; 0.05) in invasion. DCLK1 expression level is decreased more than 30% by knocking down ZEB1 in HCT116 cells. In addition, knockdown DCLK1 increased 5-FU induced cell apoptosis more than 50% (P&lt;0.05). Evidence from TCGA COADREAD demonstrated that EMT predicts survival in CRC patients, and increased expression level of DCLK1 in CRC patients correlate to EMT and mesenchymal phenotype. These data suggest that DCLK1 is a part of an EMT feedback-loop and may be exploited with DCLK1-targeted therapeutics for CRC.
Citation Format: Dongfeng Qu, Nathaniel Weygant, William L. Berry, Randal May, Parthasarathy Chandrakesan, James J. Tomasek, Sripathi M. Sureban, Courtney Houchen, Yang Ge, Jiannan Yao, Guangyu An, Edwin Bannerman-Menson. DCLK1 is part of an EMT feedback loop and promotes colorectal cancer cell invasion and drug resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3888. doi:10.1158/1538-7445.AM2017-3888