A19 ROLE OF LGR5 IN DCLK1 POSITIVE CELL-DERIVED COLITIS-ASSOCIATED COLON CANCER. (15th March 2019)

• Record Type: Journal Article
• Authors: Shin, A E; Good, H; Zhang, L; Fazio, E N; Sherman, P M; Wang, T C; Asfaha, S
• Is Part Of: Journal of the Canadian Association of Gastroenterology. Volume 2(2019)Supplement 2
• Page Start: 36
• Page End: 37
• Publication Date: 2019-03-15
• Subjects: Gastroenterology -- Periodicals; 616.33005
• DOI: 10.1093/jcag/gwz006.018
• Languages: English
• ISSNs: 2515-2084

Abstract

Abstract: Background: Colorectal cancer (CRC) is the second leading cause of cancer death in Canada, with the major risk factor being chronic inflammation. As such, patients with inflammatory bowel disease (IBD) are at an increased risk of CRC. Despite the clear association between inflammation and cancer, the mechanism by which colitis leads to CRC is still not well understood. Our recent work has focused on a colonic epithelial cell known as the tuft cell that uniquely expresses the protein doublecortin-like kinase 1 (Dclk1). Using Cre-dependent lineage tracing of Dclk1-expressing cells, we showed that Dclk1 labels long-lived quiescent cells in the colon that serve as a cellular origin of CRC upon colonic inflammation. Aims: In this study, we aim to explore the mechanism by which inflammation contributes to tuft cell cancer initiation. We hypothesized that colonic inflammatory insult leads to dedifferentiation of Dclk1+ tuft cells to a stem cell state susceptible to tumor initiation. Methods: To generate tamoxifen-inducible Cre transgenic mice that allow for Dclk1 + cell lineage tracing and cell-specific knock-out of the tumor suppressor adenomatous polyposis coli (APC ), we first crossed our transgenic Dclk1-CreER T2 mice to both ROSA26-tdTomato and APC fl/fl mice (Dclk1/APC fl/fl ). To examine the role of dedifferentiation in colonic tumor initiation, these mice were further crossed to Lgr5-DTR-eGFP mice (Lgr5 DTR ;Dclk1/APC fl/fl ). These mice were given tamoxifen and DSS in order to induce tumorigenesis. Mice were administered diphtheria toxin (DT) for six weeks post DSS injury to ablate Lgr5-expressing cells and were compared to Lgr5 DTR -negative control mice (Dclk1/APC fl/fl ). Results: Reverse transcription polymerase chain reaction (RT-PCR) analysis of mRNA levels revealed significantly reduced Lgr5, and increased RSPO1 and RSPO3 levels in colonic tissues of DSS-administered mice. Ablation of Lgr5 + cells post DSS-colitis significantly reduced the number of colonic tumors in our Dclk1/APC fl/fl mouse model, with no significant difference in tumor size. Lgr5-expressing cells were readily seen throughout colonic tumors arising from Dclk1 + cells. Interestingly, two weeks post DSS-induced colitis, rare Dclk1 + cells that co-expressed Lgr5 were also detected. Conclusions: Our data prove that upon DSS-induced colonic injury, Dclk1 + tuft cells express the stem cell marker Lgr5 prior to initiation of colonic tumorigenesis. These data suggest that dedifferentiation of Dclk1 + cells plays an important role in colitis-associated CRC and provide insight into the molecular mechanism by which Dclk1-derived colonic tumors arise. Funding Agencies: CAG, CIHRCRS