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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...

Inactivating mutations of Arid1a, a subunit of the Switch/sucrose nonfermentable chromatin remodeling complex, have been reported in multiple human cancers. Intestinal deletion of Arid1a has been reported to induce colorectal cancer in mice; however, its functional role in intestinal homeostasis remains unclear. We investigated the functional role of Arid1a in intestinal homeostasis in mice. We found that intestinal deletion of Arid1a results in loss of intestinal stem cells (ISCs), decreased Paneth and goblet cells, disorganized crypt-villous structures, and increased apoptosis in adult mice. Spheroids did not develop from intestinal epithelial cells deficient for Arid1a. Lineage-tracing experiments revealed that Arid1a deletion in Lgr5+ ISCs leads to impaired self-renewal of Lgr5+ ISCs but does not perturb intestinal homeostasis. The Wnt signaling pathway, including Wnt agonists, receptors, and target genes, was strikingly down-regulated in Arid1a-deficient intestines. We found that Arid1a directly binds to the Sox9 promoter to support its expression. Remarkably, overexpression of Sox9 in intestinal epithelial cells abrogated the above phenotypes, although Sox9 overexpression in intestinal epithelial cells did not restore the expression levels of Wnt agonist and receptor genes. Furthermore, Sox9 overexpression permitted development of spheroids from Arid1a-deficient intestinal epithelial cells. In addition, deletion of Arid1a concomitant with Sox9 overexpression in Lgr5+ ISCs restores self-renewal in Arid1a-deleted Lgr5+ ISCs. These results indicate that Arid1a is indispensable for the maintenance of ISCs and intestinal homeostasis in mice. Mechanistically, this is mainly mediated by Sox9. Our data provide insights into the molecular mechanisms underlying maintenance of ISCs and intestinal homeostasis.

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.

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