There is great interest in tumor stem cells (TSCs) as potential therapeutic targets; however, cancer therapies targeting TSCs are limited. A drawback is that TSC markers are often shared by normal stem cells (NSCs); thus, therapies that target these markers may cause severe injury to normal tissues. To identify a potential TSC-specific marker, we focused on doublecortin-like kinase 1 (Dclk1). Dclk1 was reported as a candidate NSC marker in the gut, but recent reports have implicated it as a marker of differentiated cells (for example, Tuft cells). Using lineage-tracing experiments, we show here that Dclk1 does not mark NSCs in the intestine but instead marks TSCs that continuously produce tumor progeny in the polyps of Apc(Min/+) mice. Specific ablation of Dclk1-positive TSCs resulted in a marked regression of polyps without apparent damage to the normal intestine. Our data suggest the potential for developing a therapy for colorectal cancer based on targeting Dclk1-positive TSCs.

Cancer stem cell (CSC)-specific markers may be potential therapeutic targets. We previously identified that Dclk1, a tuft cell marker, marks tumor stem cells (TSCs) in mouse intestinal adenomas. Based on the analysis of mouse Dclk1 + tumor cells, we aimed to identify a CSC-specific cell surface marker in human colorectal cancers (hCRCs) and validate the therapeutic effect of targeting it. IL17RB was distinctively expressed by Dclk1 + mouse intestinal tumor cells. Using Il17rb-CreERT2-IRES-EGFP mice, we show that IL17RB marked intestinal TSCs in an IL13-dependent manner. Tuft cell-like cancer cells were detected in a subset of hCRCs. In these hCRCs, lineage-tracing experiments in CRISPR-Cas9-mediated IL17RB-CreERT2 knockin organoids and xenograft tumors revealed that IL17RB marks CSCs that expand independently of IL-13. We observed up-regulation of POU2F3, a master regulator of tuft cell differentiation, and autonomous tuft cell-like cancer cell differentiation in the hCRCs. Furthermore, long-term ablation of IL17RBexpressing CSCs strongly suppressed the tumor growth in vivo. These findings reveal insights into a CSC-specific marker IL17RB in a subset of hCRCs, and preclinically validate IL17RB + CSCs as a cancer therapeutic target.C ancer stem cells (CSCs), capable of self-renewal and giving rise to progeny cells in cancers, have attracted attention as promising targets for anticancer therapeutics. The traditional xenotransplantation assays used to investigate the properties of CSCs have technical and conceptual limitations (1). Recent studies have shown that leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5) marks CSCs in human colorectal cancers (hCRCs) in vivo by lineage tracing of LGR5-CreERT2 knockin hCRC organoids generated by CRISPR-Cas9-mediated gene editing (2, 3). Because most of the CSC markers are also expressed by normal stem cells (4-7), long-term CSC targeting may disrupt normal tissue homeostasis [e.g., liver injury after long-term LGR5-targeting (8)], whereas short-term CSC targeting leads to tumor regrowth (2,9). Hence, identification of CSC-specific markers is essential. We previously showed that Dclk1, a differentiated tuft cell marker in normal intestine, marks tumor stem cells (TSCs) in mouse intestinal adenomas by lineage-tracing experiments (10). However, whether DCLK1 marks CSCs in hCRCs has not been elucidated by in vivo lineage tracing of the tumors. Furthermore, feasible strategies to target DCLK1 + cells are necessary to realize a novel CSC-targeted therapy for hCRCs. Identification of a specific cell surface marker in Dclk1 + cells can facilitate the sorting analysis of Dclk1 + tumor cells and can also have the potential for future antibody therapeutics.The IL-17 receptor family includes five members (IL17RA to IL17RE) (11). The heterodimer of IL17RA and IL17RC serves as a receptor for IL-17A and IL-17F to mediate Th17 immune response, and the heterodimer of IL17RA and IL17RB serves as a receptor for IL-25 to mediate Th2 immune response (12).Recent studies showed that...

Chromatin remodeler Brahma related gene 1 (BRG1) is silenced in approximately 10% of human pancreatic ductal adenocarcinomas (PDAs). We previously showed that BRG1 inhibits the formation of intraductal pancreatic mucinous neoplasm (IPMN) and that IPMN-derived PDA originated from ductal cells. However, the role of BRG1 in pancreatic intraepithelial neoplasia-derived (PanIN-derived) PDA that originated from acinar cells remains elusive. Here, we found that exclusive elimination of Brg1 in acinar cells of Ptf1a-CreER; KrasG12D; Brg1fl/fl mice impaired the formation of acinar-to-ductal metaplasia (ADM) and PanIN independently of p53 mutation, while PDA formation was inhibited in the presence of p53 mutation. BRG1 bound to regions of the Sox9 promoter to regulate its expression and was critical for recruitment of upstream regulators, including PDX1, to the Sox9 promoter and enhancer in acinar cells. SOX9 expression was downregulated in BRG1-depleted ADMs/PanINs. Notably, Sox9 overexpression canceled this PanIN-attenuated phenotype in KBC mice. Furthermore, Brg1 deletion in established PanIN by using a dual recombinase system resulted in regression of the lesions in mice. Finally, BRG1 expression correlated with SOX9 expression in human PDAs. In summary, BRG1 is critical for PanIN initiation and progression through positive regulation of SOX9. Thus, the BRG1/SOX9 axis is a potential target for PanIN-derived PDA.

In the mammalian stomach, the isthmus has been considered as a stem cell zone. However, various locations and proliferative activities of gastric stem cells have been reported. We focused here on the stem cell marker Bmi1, a polycomb group protein, aiming to elucidate the characteristics of Bmi1‐expressing cells in the stomach and to examine their stem cell potential. We investigated the Bmi1‐expressing cell lineage in Bmi1‐CreERT; Rosa26‐YFP, LacZ or Rosa26‐Confetti mice. We examined the in vivo and ex vivo effects of Bmi1‐expressing cell ablation by using Bmi1‐CreERT; Rosa26‐iDTR mice. The Bmi1 lineage was also traced during regeneration after high‐dose tamoxifen‐, irradiation‐ and acetic acid‐induced mucosal injuries. In the lineage‐tracing experiments using low‐dose tamoxifen, Bmi1‐expressing cells in the isthmus of the gastric antrum and corpus provided progeny bidirectionally, towards both the luminal and basal sides over 6 months. In gastric organoids, Bmi1‐expressing cells also provided progeny. Ablation of Bmi1‐expressing cells resulted in impaired gastric epithelium in both mouse stomach and organoids. After high‐dose tamoxifen‐induced gastric mucosal injury, Bmi1‐expressing cell lineages expanded and fully occupied all gastric glands of the antrum and the corpus within 7 days after tamoxifen injection. After irradiation‐ and acetic acid‐induced gastric mucosal injuries, Bmi1‐expressing cells also contributed to regeneration. In conclusion, Bmi1 is a gastric stem cell marker expressed in the isthmus of the antrum and corpus. Bmi1‐expressing cells have stem cell potentials, both under physiological conditions and during regeneration after gastric mucosal injuries. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease. Although rigorous efforts identified the presence of ‘cancer stem cells (CSCs)’ in PDAC and molecular markers for them, stem cell dynamics in vivo have not been clearly demonstrated. Here we focused on Doublecortin-like kinase 1 (Dclk1), known as a CSC marker of PDAC. Using genetic lineage tracing with a dual-recombinase system and live imaging, we showed that Dclk1+ tumor cells continuously provided progeny cells within pancreatic intraepithelial neoplasia, primary and metastatic PDAC, and PDAC-derived spheroids in vivo and in vitro. Furthermore, genes associated with CSC and epithelial mesenchymal transition were enriched in mouse Dclk1+ and human DCLK1-high PDAC cells. Thus, we provided direct functional evidence for the stem cell activity of Dclk1+ cells in vivo, revealing the essential roles of Dclk1+ cells in expansion of pancreatic neoplasia in all progressive stages.