Cellular plasticity in adult organs is involved in both regeneration and carcinogenesis. WT mouse acinar cells rapidly regenerate following injury that mimics acute pancreatitis, a process characterized by transient reactivation of pathways involved in embryonic pancreatic development. In contrast, such injury promotes the development of pancreatic ductal adenocarcinoma (PDA) precursor lesions in mice expressing a constitutively active form of the GTPase, Kras, in the exocrine pancreas. The molecular environment that mediates acinar regeneration versus the development of PDA precursor lesions is poorly understood. Here, we used genetically engineered mice to demonstrate that mutant Kras promotes acinar-to-ductal metaplasia (ADM) and pancreatic cancer precursor lesion formation by blocking acinar regeneration following acute pancreatitis. Our results indicate that β-catenin is required for efficient acinar regeneration. In addition, canonical β-catenin signaling, a pathway known to regulate embryonic acinar development, is activated following acute pancreatitis. This regeneration-associated activation of β-catenin signaling was not observed during the initiation of Kras-induced acinar-to-ductal reprogramming. Furthermore, stabilized β-catenin signaling antagonized the ability of Kras to reprogram acini into PDA preneoplastic precursors. Therefore, these results suggest that β-catenin signaling is a critical determinant of acinar plasticity and that it is inhibited during Kras-induced fate decisions that specify PDA precursors, highlighting the importance of temporal regulation of embryonic signaling pathways in the development of neoplastic cell fates. IntroductionPancreatic ductal adenocarcinoma (PDA) is the fourth leading cause of cancer death in the United States (1). Analysis of patient samples and genetically engineered mouse models suggests that it likely develops from preneoplastic ductal lesions, including pancreatic intraepithelial neoplasias (PanINs) (2). Understanding how signaling pathways interact in the pancreatic epithelium to elicit PanINs therefore represents a key step in the possible development of tools for early PDA detection and treatment. While PanINs express markers of ductal differentiation, many recent studies suggest that they can arise from pancreatic acinar cells that are reprogrammed into a preneoplastic state by undergoing acinar-toductal metaplasia (ADM) (3-7).Activating mutations in the gene encoding the GTPase Kras are nearly universal in human PDA (8), and targeting of mutated Kras to mouse pancreatic progenitors recapitulates the human PanIN-to-PDA progression sequence (9). While ADM is observed in these models (6) and Kras can spontaneously induce ADM and PanIN formation when activated in adult acini (3, 4, 7), expression of mutant Kras in acinar cells does not guarantee ductal reprogramming. Acini expressing mutant Kras during embryogenesis appear grossly unaffected (9), and some normal acinar tissue is maintained in the context of PanIN and PDA progression as mice age (9, 10...

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There is accumulating evidence that Wnt/␤-catenin signaling is involved in the regulation of liver development and physiology. The presence of genetic alterations resulting in constitutive ␤-catenin stabilization in human and murine liver tumors also implicates this pathway in hepatocyte proliferation. In the present study, we generated hepatocyte-specific ␤-catenin knockout mice to explore the role of ␤-catenin in liver function. Conditional knockout mice were born at the expected Mendelian ratio and developed normally to adulthood, indicating ␤-catenin is dispensable for essential liver function under normal breeding conditions. However, the liver mass of knockout mice was 20% less than those of mice in the control groups. Expression analysis revealed loss of genes required for glutamine synthesis in knockout mice. Loss of the liver glutamine synthesis pathway did not affect the blood ammonia level in mice fed a standard diet, yet, knockout mice showed significantly elevated blood ammonia levels with high-protein dietary feeding. Furthermore, the expression of two cytochrome P450 enzymes, CYP1A2 and CYP2E1, was almost completely abolished in livers from hepatocyte-specific ␤-catenin knockout mice. Consequently, these mice were resistant to acetaminophen challenge, confirming the requirement of these cytochrome P450 enzymes for metabolism of xenobiotic substances. ␤ -Catenin is an adapter protein that fulfills two distinct roles in cells. As a part of an adherens junction complex, it interacts with transmembrane proteins of the cadherin family to promote cell-cell adhesion. In addition, ␤-catenin is an integral part of the canonical Wnt signaling pathway known to regulate cell proliferation, differentiation, and stem cell maintenance in a wide variety of tissues. 1-3 Wnt ligands are secreted proteins that bind to cognate frizzled receptors expressed in the cell membrane of Wnt-responsive cells. In the absence of Wnt signals, cytoplasmic ␤-catenin is phosphorylated by glycogen synthase kinase 3␤, a modification that triggers rapid proteosomal degradation of ␤-catenin. Upon stimulation with Wnt ligands, cytoplasmic ␤-catenin is stabilized and translocates to the nucleus, where it forms active transcription complexes with members of the TCF/LEF1 transcription factor family.There is accumulating evidence that indicates a role for Wnt/␤-catenin signaling in hepatocyte proliferation. Micsenyi et al. reported nuclear/cytoplasmic localization of ␤-catenin in hepatocytes during early developmental stages, which gradually decrease with progression of organ development. During liver development, the level of nuclear/cytoplasmic ␤-catenin expression correlates well with the proliferative activity of hepatocytes. 4 Suppression of ␤-catenin by antisense oligonucleotides in ex vivo liver cultures results in decreased cell proliferation and increased apoptosis of hepatocytes. 5 Conversely, transgenic expression of N-terminally truncated ␤-catenin results in increased hepatocyte proliferation and hepatomegaly, 6 a finding that ...

Next‐generation sequencing ( NGS ) of tumor tissue (ie, clinical sequencing) can guide clinical management by providing information about actionable gene aberrations that have diagnostic and therapeutic significance. Here, we undertook a hospital‐based prospective study ( TOP ‐ GEAR project, 2nd stage) to investigate the feasibility and utility of NGS ‐based analysis of 114 cancer‐associated genes (the NCC Oncopanel test). We examined 230 cases (comprising more than 30 tumor types) of advanced solid tumors, all of which were matched with nontumor samples. Gene profiling data were obtained for 187 cases (81.3%), 111 (59.4%) of which harbored actionable gene aberrations according to the Clinical Practice Guidelines for Next Generation Sequencing in Cancer Diagnosis and Treatment (Edition 1.0) issued by 3 major Japanese cancer‐related societies. Twenty‐five (13.3%) cases have since received molecular‐targeted therapy according to their gene aberrations. These results indicate the utility of tumor‐profiling multiplex gene panel testing in a clinical setting in Japan. This study is registered with UMIN Clinical Trials Registry ( UMIN 000011141).

Recent sequencing analyses have shed light on heterogeneous patterns of genomic aberrations in human gastric cancers (GCs). To explore how individual genetic events translate into cancer phenotypes, we established a biological library consisting of genetically engineered gastric organoids carrying various GC mutations and 37 patient-derived organoid lines, including rare genomically stable GCs. Phenotype analyses of GC organoids revealed divergent genetic and epigenetic routes to gain Wnt and R-spondin niche independency. An unbiased phenotype-based genetic screening identified a significant association between CDH1/TP53 compound mutations and the R-spondin independency that was functionally validated by CRISPR-based knockout. Xenografting of GC organoids further established the feasibility of Wnt-targeting therapy for Wnt-dependent GCs. Our results collectively demonstrate that multifaceted genetic abnormalities render human GCs independent of the stem cell niche and highlight the validity of the genotype-phenotype screening strategy in gaining deeper understanding of human cancers.