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.

Setdb1 p53 P ancreatic ductal adenocarcinoma (PDAC) is one of the most dismal malignancies, with an extremely poor prognosis. 1 In order to further improve the prognosis, it is crucial to elucidate the molecular mechanisms underlying PDAC initiation and progression. Recent studies have revealed that epigenetic abnormalities exhibit a great influence on the characteristics of cancer development in addition to genetic abnormalities. 2-4 One form of epigenetic regulation, known as histone modification, contributes to tumorigenesis by affecting the expression of oncogenes/tumor suppressor genes. In fact, previous reports have shown that histone methyltransferases suppress pancreatic cancer by regulating glucose/fatty acid metabolism and promoting pancreatic regeneration. 5,6 Setdb1 serves as a histone 3 lysine 9 trimethyltransferase. Trimethylation of histone 3 lysine 9 (H3K9me3) is a repressive chromatin modification. 7 Setdb1 plays different functional roles through gene silencing. It helps to control heterochromatin formation 8 and contributes to stem cell maintenance, 9 embryonic development, and endogenous proviral silencing. 10 Recently, an in vivo study revealed that the amplification of Setdb1 accelerates the development of melanoma, 11 and SETDB1 has been shown to promote tumorigenesis in various human cancers, including lung, 12 liver, 13,14 and breast cancers. 15 Furthermore, a wholeexome sequencing study revealed a copy number amplification mutation of SETDB1 in PDAC patients. 16 These findings indicate a role of Setdb1 in PDAC initiation and progression. However, the functional role of Setdb1 in PDAC remains elusive. Therefore, in this study, we aimed to investigate the impact of Setdb1 deletion on Kras-induced pancreatic tumorigenesis and elucidate the in vivo role of Setdb1 in PDAC formation in mouse models. Materials and Methods Mice Experimental animals were generated by crossing Ptf1a Cre (gift from Y. Kawaguchi, Kyoto University, Kyoto, Japan), 17 Kras G12D (gift from D. Tuveson, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY), 18 Setdb1 flox (gift from Y. Shinkai, Riken, Saitama, Japan), 10 and p53 flox (purchase from Jackson Laboratory, Bar Harbor, ME; JAX strain 008462). Acute pancreatitis was induced at 6 weeks of age by injecting cerulein (2 mg/injection diluted in phosphate-buffered saline; Sigma-Aldrich, St Louis, MO) intraperitoneally on 2 consecutive days once every hour for 8 hours each day. 19 Clinical Samples Forty-eight surgically resected specimens of pancreatic cancer tissues were obtained from patients who had been admitted to Kyoto University Hospital. Written informed consent was obtained from all patients and the protocol was approved by the Ethics Committee of Kyoto University.

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.

Nonalcoholic steatohepatitis (NASH) is an inflammatory form of nonalcoholic fatty liver disease that progresses to liver cirrhosis. It is still unknown how only limited patients with fatty liver develop NASH. Tumor necrosis factor (TNF)-α is one of the key molecules in initiating the vicious circle of inflammations. Nardilysin (N-arginine dibasic convertase; Nrd1), a zinc metalloendopeptidase of the M16 family, enhances ectodomain shedding of TNF-α, resulting in the activation of inflammatory responses. In this study, we aimed to examine the role of Nrd1 in the development of NASH. Nrd1+/+ and Nrd1−/− mice were fed a control choline-supplemented amino acid-defined (CSAA) diet or a choline-deficient amino acid-defined (CDAA) diet. Fatty deposits were accumulated in the livers of both Nrd1+/+ and Nrd1−/− mice by the administration of the CSAA or CDAA diets, although the amount of liver triglyceride in Nrd1−/− mice was lower than that in Nrd1+/+ mice. Serum alanine aminotransferase levels were increased in Nrd1+/+ mice but not in Nrd1−/− mice fed the CDAA diet. mRNA expression of inflammatory cytokines were decreased in Nrd1−/− mice than in Nrd1+/+ mice fed the CDAA diet. While TNF-α protein was detected in both Nrd1+/+ and Nrd1−/− mouse livers fed the CDAA diet, secretion of TNF-α in Nrd1−/− mice was significantly less than that in Nrd1+/+ mice, indicating the decreased TNF-α shedding in Nrd1−/− mouse liver. Notably, fibrotic changes of the liver, accompanied by the increase of fibrogenic markers, were observed in Nrd1+/+ mice but not in Nrd1−/− mice fed the CDAA diet. Similar to the CDAA diet, fibrotic changes were not observed in Nrd1−/− mice fed a high-fat diet. Thus, deletion of nardilysin prevents the development of diet-induced steatohepatitis and liver fibrogenesis. Nardilysin could be an attractive target for anti-inflammatory therapy against NASH.

Colonic epithelial cells comprise the mucosal barrier, and their dysfunction promotes microbial invasion from the gut lumen and induces the development of intestinal inflammation. The EP4 receptor is known to mediate the protective effect of prostaglandin (PG) E2 in the gastrointestinal tract; however, the exact role of epithelial EP4 in intestinal pathophysiology remains unknown. In the present study, we aimed to investigate the role of epithelial EP4 in maintaining colonic homeostasis by characterizing the intestinal epithelial cell-specific EP4 knockout (EP4 cKO) mice. Mice harboring the epithelial EP4 deletion showed significantly lower colonic crypt depth and lower numbers of secretory cell lineages, as well as impaired epithelial cells in the colon. Interestingly, EP4-deficient colon epithelia showed a higher number of apoptotic cells. Consistent with the defect in mucosal barrier function of colonic epithelia and secretory cell lineages, EP4 cKO colon stroma showed enhanced immune cell infiltration, which was accompanied by increased production of inflammatory cytokines. Furthermore, EP4-deficient colons were susceptible to dextran sulfate sodium (DSS)-induced colitis. Our study is the first to demonstrate that epithelial EP4 loss resulted in potential “inflammatory” status under physiological conditions. These findings provided insights into the crucial role of epithelial PGE2/EP4 axis in maintaining intestinal homeostasis.

We revealed factors that are highly expressed in Dclk1 intestinal tumor cells, which may help to develop cancer stem cell-targeted therapy in future.

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