Abstract 4092: Long-lived Dclk1+ cells serve as colon cancer initiating cells
Authors: Asfaha Samuel , Westphalen Christoph Benedikt , Hayakawa Yoku , Takemoto Yoshihiro , Lukin Dana J. , Setlik Wanda , Remotti Helen , Muley Ashlesha , Chen Xiaowei , May Randal , Houchen Courtney W. , Fox James G. , Gershon Michael D. , Quante Michael , Wang Timothy 
Published: May 2015

Abstract
Introduction: In the rapidly proliferating gastrointestinal epithelium, long-lived tissue stem cells, characterized by multipotentiality and self-renewing ability, remain the most likely cellular origin for cancer. Previous studies have suggested actively cycling Lgr5+ stem cells are one cellular origin for intestinal adenomas. However, it has also recently been suggested that non-Lgr5+ cells may also contribute to the cellular origin of colorectal cancer. Doublecortin-like kinase 1 (Dclk1) protein is a gastrointestinal tuft cell marker that has been proposed to identify quiescent stem cells and cancer stem cells that sustain tumor growth. The role of Dclk1+ tuft cells within the gastrointestinal epithelium and their potential to function as cancer-initiating cells, however, remain poorly understood. Here, we used Dclk1(BAC)-CreERT;ROSA26rLacZ mice crossed to APCff mice to examine whether Dclk1+ cells contribute to colonic tumor formation.
Methods: To recapitulate the endogenous expression pattern of Dclk1, we used a BAC strategy and generated a transgenic mouse with a Tamoxifen inducible Cre under the control of the Dclk1 promoter (Dclk1-BAC-Cre-ERT). Dclk1-CreERT mice were crossed to both ROSA26rLacZ and APCff mice and treated with tamoxifen (6 mg p.o.). Dclk1+ lineage tracing was assessed by X-gal staining. To examine the contribution of the Dclk1+ cells to colonic tumorigenesis, we treated Dclk1(BAC)-CreERT;ROSA26rLacZ; APCff mice with DSS (3% in drinking water) to induce colitis. Mice were sacrificed 3-4 months after DSS weeks to assess for tumor formation and X-gal staining performed to stain for the Dclk1+ cell lineage.
Results: Dclk1-BAC-CreERT genetic lineage tracing demonstrated that a subpopulation of Dclk1+ cells is extremely long-lived and shows rare stem cell abilities. Moreover, genetic ablation reveals a pivotal role for Dclk1+ tuft cells in the response to intestinal and colonic injury. Surprisingly, conditional loss of APC in Dclk1+ cells is not sufficient to drive colonic carcinogenesis, whereas induction of DSS colitis in Dclk1-CreERT; APCflox/flox mice leads to the development of poorly differentiated colonic adenocarcinoma. Importantly, colonic tumor formation occurs even when the onset of colitis is delayed for up to 3 months after APC loss in Dclk1+ cells.
Conclusions. Thus, our data define a novel intestinal Dclk1+ tuft cell population that is long-lived, quiescent and important for intestinal homeostasis and regeneration. Long-lived Dclk1+ cells maintain quiescence even following oncogenic mutation, but are activated by tissue injury and can serve as a potent cellular origin of colon cancer.
Citation Format: Samuel Asfaha, Christoph Benedikt Westphalen, Yoku Hayakawa, Yoshihiro Takemoto, Dana J. Lukin, Wanda Setlik, Helen Remotti, Ashlesha Muley, Xiaowei Chen, Randal May, Courtney W. Houchen, James G. Fox, Michael D. Gershon, Michael Quante, Timothy Wang. Long-lived Dclk1+ cells serve as colon cancer initiating cells. [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 4092. doi:10.1158/1538-7445.AM2014-4092