Abstract 3829: Dclk1 expressing crypt epithelial cells become tumor initiating stem cells in an inflammation associated environment
Authors: Chandrakesan Parthasarathy , Panneerselvam Janani , Qu Dongfeng , Rao Chinthalapally , Bronze Michael , Houchen Courtney 
Published: September 2020

Abstract
Background: Chronic intestinal inflammation is a major risk factor for the development of CRC and consequently individuals suffering from inflammatory bowel diseases (IBD) are at increased risk. However, the molecular mechanism by which inflammation initiates colonic tumorigenesis in the cell type is unclear and the regulatory factors that mediate the complex interplay between inflammation and the colonic tumor initiation are unknown. Doublecortin-like kinase 1 (Dclk1) is a microtubule-associated kinase, which marks TSCs in colon cancer, and is predominantly expressed in a unique intestinal epithelial cell type termed the tuft cells. Tuft cells are chemosensory cells that regulate host immunity and inflammation and is highly increased in CRC and, ablation of Dclk1 expressing cells in the ApcMin/+ mice completely regressed the tumors without affecting the normal stem cell population. Our aim is to elucidate the molecular mechanism that is responsible for inflammation-associated colon cancer and to determine the role of Dclk1 expressing tuft cells in this process.
Experimental Procedure: YMCA non-malignant colonic epithelial cells were used. Loss and gain of Dclk1 expression in the YMCA cells were carried with siRNA transfection and lentivirus overexpression vector infection respectively. Dclk1 expressing cells were selected for stable cell generation. DSS and LPS were used. Cell self-renewal, secondary and tertiary organoid generation, survival, DNA damage, DNA damage response (DDR) and apoptosis were assessed. Protein and mRNA expressions by western-blot and RT-PCR.
Results: Here, we report that increased expression of Dclk1 is the key to the generation of tumor-initiating cells under the influence of an inflammatory environment. We observed increased self-renewal of Dclk1+ YMCA cells treated with DSS and further increase in self-renewal was observed with DSS+LPS treatment. Silencing Dclk1 failed to initiate self-renewal under the influence of DSS and LPS treatment. Dclk1+ YMCA cells displayed enhanced inflammatory mediators, survival with colony formation and increased survival pathways (AKT/mTOR/Beta-catenin/NFkB pathways) and DDR (ATM/ATR) with DSS or LPS treatment. However, the DNA damage and cell apoptosis were not increased in vector control cells and significantly increased in Dclk1 knockdown cells after DSS or LPS treatment.
Conclusion: Our data demonstrate that the increased expression of Dclk1 is associated with tumor-initiating features, and survival ability in an inflammatory environment, which is important to understand the cell type and inflammation associated mechanisms in tumor initiation. Based on these findings we proposed that specific targeting of Dclk1-expressing colonic crypt epithelial cells has the potential to result in ablation of tumor initiation.
Citation Format: Parthasarathy Chandrakesan, Janani Panneerselvam, Dongfeng Qu, Chinthalapally Rao, Michael Bronze, Courtney Houchen. Dclk1 expressing crypt epithelial cells become tumor initiating stem cells in an inflammation associated environment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3829.