Impaired glycosylation of gastric mucins drives gastric tumorigenesis and serves as a novel therapeutic target.

BACKGROUND: Gastric cancer is often accompanied by a loss of MUC6, but its pathogenic role in gastric carcinogenesis remains unclear. METHOD: Muc6 knockout (Muc6-/-) mice and Muc6-dsRED mice were newly generated. Tff1Cre, Golph3-/-, R26-Golgi-mCherry, Hes1flox/flox, Cosmcflox/flox, A4gnt-/- mice were also used. Histology, DNAs and RNAs, proteins, and sugar chains were analyzed by whole exon DNA sequence, RNA sequence, immunohistochemistry, lectin-binding assays, and LC-MS analysis. Gastric organoids and cell lines were used for in vitro assays and xenograft experiments. RESULT: Deletion of Muc6 in mice spontaneously causes pan-gastritis and invasive gastric cancers. Muc6-deficient tumor growth was dependent on MAPK activation, mediated by Golgi stress-induced upregulation of GOLPH3. Glycomic profiling revealed aberrant expression of mannose-rich N-linked glycans in gastric tumors, detected with Banana lectin in association with lack of MUC6 expression. We identified a precursor of clusterin as a binding partner of mannose glycans. MAPK activation, Golgi stress responses, aberrant mannose expression are found in a separate Cosmc- and A4gnt-deficient mouse models which lack normal O-glycosylation. Banana lectin-drug conjugates proved an effective treatment for mannose-rich murine and human gastric cancer. CONCLUSION: We propose that Golgi stress responses and aberrant glycans are important drivers of, and promising new therapeutic targets for gastric cancer.

A case of acute liver failure caused by Budd-Chiari syndrome salvaged by brain-dead donor liver transplantation.

A 24-year-old man was admitted to our hospital with abdominal distension. He was found to have acute liver failure and diagnosed with Budd-Chiari syndrome based on angiography and liver biopsy. Liver transplantation was deemed necessary when angiography showed extensive thrombotic occlusion of the hepatic veins and liver biopsy revealed submassive hepatic necrosis. The patient was found to have the JAK2V617F mutation, indicating a myeloproliferative neoplasm as the background disease. He developed hepatic encephalopathy but remained conscious on on-line hemodiafiltration. Brain-dead donor liver transplantation was performed on hospital day 30. Since then, the patient has remained well.

Case report: Irinotecan-induced interstitial lung disease in an advanced colorectal cancer patient resurfacing decades after allogeneic bone marrow transplantation for aplastic anemia; a case report and narrative review of literature.

Two mechanisms of drug-induced interstitial lung disease (DILD) have been reported: 1) direct injury of lung epithelial cells and/or endothelial cells in lung capillaries by the drug and/or its metabolites and 2) hypersensitivity reactions. In both mechanisms, immune reactions such as cytokine and T cell activation are involved in DILD. While past and present lung diseases and accumulative lung damage due to smoking and radiation are risk factors for DILD, the association between the immune status of the host and DILD is not well known. Herein, we report a case of advanced colorectal cancer with a history of allogeneic bone marrow transplantation for aplastic anemia more than 30 years prior, in which DILD occurred early after irinotecan-containing chemotherapy. Bone marrow transplantation might be a potential risk factor for DILD.

The Outcome of Salvage Liver Transplantation and Liver Resection for Recurrent Hepatocellular Carcinoma Using the 5-5-500 Rule, Japanese Extended Liver Transplantation Criteria for Hepatocellular Carcinoma.

BACKGROUND: Liver transplantation (LT) for hepatocellular carcinoma (HCC) is limited to Child-Pugh class C patients according to the Japanese HCC treatment algorithm. However, extended criteria of LT for HCC, known as the 5-5-500 rule, were published in 2019. Hepatocellular carcinoma reportedly has a high recurrence rate after primary treatment. We hypothesized that the outcome of recurrent HCC would be improved if the 5-5-500 rule were adopted for patients with recurrent HCC. We, therefore, analyzed the outcomes of surgical treatment (liver resection [LR] and LT) for recurrent HCC using the 5-5-500 rule in our institute. METHODS: Fifty-two patients younger than 70 years of age received surgical treatment for recurrent HCC using our institute's 5-5-500 rule from 2010 to 2019. We divided these patients into the LR and LT groups in the first study. The 10-year overall survival and re-recurrence-free survival were analyzed. The second study analyzed the risk factors of re-recurrence after surgical treatment for recurrent HCC. RESULTS: In the first study, the background characteristics of the 2 groups (LR and LT) showed no significant difference, except for age and Child-Pugh classification. There was no significant difference in the overall survival between groups (P = .35), but the re-recurrence-free survival in the LR group was significantly shorter than that in the LT group (P < .01). In the second study, the male sex and LR were risk factors of re-recurrence after surgical treatment for recurrent HCC. Child-Pugh's class did not contribute to re-recurrence. CONCLUSIONS: To improve the outcomes of recurrent HCC, LT is the better choice, regardless of the Child-Pugh class.

HNF1B-driven three-dimensional chromatin structure for molecular classification in pancreatic cancers.

The molecular subtypes of pancreatic cancer (PC), either classical/progenitor-like or basal/squamous-like, are currently a major topic of research because of their direct association with clinical outcomes. Some transcription factors (TFs) have been reported to be associated with these subtypes. However, the mechanisms by which these molecular signatures of PCs are established remain unknown. Epigenetic regulatory processes, supported by dynamic changes in the chromatin structure, are essential for transcriptional profiles. Previously, we reported the importance of open chromatin profiles in the biological features and transcriptional status of PCs. Here, we aimed to analyze the relationships between three-dimensional (3D) genome structures and the molecular subtypes of human PCs using Hi-C analysis. We observed a correlation of the specific elements of 3D genome modules, including compartments, topologically associating domains, and enhancer-promoter loops, with the expression of related genes. We focused on HNF1B, a TF that is implicated in the progenitor subtype. Forced expression of HNF1B in squamous-type PC organoids induced the upregulation and downregulation of genes associated with progenitor and squamous subtypes, respectively. Long-range genomic interactions induced by HNF1B were accompanied by compartment modulation and H3K27ac redistribution. We also found that these HNF1B-induced changes in subtype-related gene expression required an intrinsically disordered region, suggesting a possible involvement of phase separation in compartment modulation. Thus, mapping of 3D structural changes induced by TFs, such as HNF1B, may become a useful resource for further understanding the molecular features of PCs.

Efficacy of Early Video Capsule Endoscopy for Acute Overt Lower Gastrointestinal Bleeding with Colonic Diverticulosis: A Prospective Observational Study.

BACKGROUND/AIMS: Although most patients with presumptive colonic diverticular bleeding (CDB) do not undergo a small bowel investigation in clinical practice, no prospective study supports this management. We evaluated the utility of early small bowel capsule endoscopy (CE) after negative colonoscopy results. METHODS: This prospective study evaluated the diagnostic yield of early small bowel CE (≤3 days from visit) for consecutive patients with acute-onset hematochezia, when colonoscopy found colonic diverticulosis but did not identify the definite bleeding source (n = 51; presumptive CDB). As a matched control for comparing clinical outcomes, presumptive CDB patients without CE (n = 51) were retrospectively extracted. RESULTS: On CE for the prospective cohort, the rates of total positive findings, P2 findings (high bleeding potential according to the P classification), and blood pooling in the colon were 57%, 12% (ulceration, 8%; angioectasia, 4%), and 24%, respectively. The rates of rebleeding within 30 and 365 days were 16% and 29% in the prospective cohort with CE, respectively, and were not significantly different from those in the retrospective cohort without CE (10% and 25%, respectively). In addition, thromboembolism and mortality within 30 and 365 days were not significantly different between those with and without CE. CONCLUSION: Early CE detected a suspected small bowel bleeding source in 12% of acute-onset presumptive CDB patients but did not significantly improve major clinical outcomes. Therefore, routine CE is unnecessary for presumptive CDB patients after colonoscopy (UMIN000026676).

Altered mucosal immunity in HIV-positive colon adenoma: decreased CD4+ T cell infiltration is correlated with nadir but not current CD4+ T cell blood counts.

BACKGROUND: People living with HIV (PLWH) face greater risks of developing non-AIDS-defining cancers (NADCs) than the general population; however, the underlying mechanisms remain elusive. The tumor microenvironment plays a significant role in the carcinogenesis of colorectal cancer (CRC), an NADC. We studied this carcinogenesis in PLWH by determining inflammatory phenotypes and assessing PD-1/PD-L1 expression in premalignant CRC stages of colon adenomas in HIV-positive and HIV-negative patients. METHODS: We obtained polyp specimens from 22 HIV-positive and 61 HIV-negative participants treated with colonoscopy and polyp excision. We analyzed adenomas from 33 HIV-positive and 99 HIV-negative patients by immunohistochemistry using anti-CD4, anti-CD8, anti-FoxP3, and anti-CD163 antibodies. Additionally, we analyzed the expression levels of immune checkpoint proteins. We also evaluated the correlation between cell infiltration and blood cell counts. RESULTS: HIV-positive participants had fewer infiltrating CD4+ T cells than HIV-negative participants (p = 0.0016). However, no statistical differences were observed in infiltrating CD8+ and FoxP3+ T cells and CD163+ macrophages. Moreover, epithelial cells did not express PD-1 or PD-L1. Notably, CD4+ T cell infiltration correlated with nadir blood CD4+ T cell counts (p <  0.05) but not with current blood CD4+ T cell counts. CONCLUSION: Immune surveillance dysfunction owing to decreased CD4+ T cell infiltration in colon adenomas might be involved in colon carcinogenesis in HIV-positive individuals. Collectively, since the nadir blood CD4+ T cell count is strongly correlated with CD4+ T cell infiltration, it could facilitate efficient follow-up and enable treatment strategies for HIV-positive patients with colon adenomas.

Fusion HBx from HBV integrant affects hepatocarcinogenesis through deregulation of ER stress response.

Hepatitis B virus (HBV) infection is a major cause of hepatocellular carcinoma (HCC) worldwide. HBV X protein (HBx) is potentially the most oncogenic among HBV-encoding proteins, while HBV integration, which is frequently observed in HCC, contributes to HCC development. However, the molecular mechanism underlying HBV-induced hepatocarcinogenesis remains unclear. In this study, we identified the fusion HBx, the HBx-human fusion protein derived from HBV integrant, in Hep3B cells and investigated its role in hepatocarcinogenesis. The identified full-length fusion mRNA was 3,725 bp in length, and the fusion HBx, which consisted of 1-140 amino acids of HBx followed by 61 amino acids from the human genome, was translated from the fusion mRNA. The fusion HBx knockdown resulted in reduced cell proliferation and invasion, and loss of tumor development in nude mice. Moreover, the fusion HBx, but not wild HBx, provided anchorage-independent growth ability in soft agar although its transactivation ability was abrogated. Microarray analysis revealed that fusion HBx deregulated endoplasmic reticulum (ER) stress response by modifying ATF3, ATF4, and ATF6 transcription. Interestingly, the effects of fusion HBx on ER stress signaling pathway were similar to those of C-terminal truncated HBx, but significantly different from those of wild HBx. Our findings suggest that the fusion HBx plays a significant role in hepatocarcinogenesis by modifying ER stress response and could be an attractive target for the treatment of HBV-induced HCC.

Intrahepatic Cholangiocarcinoma With Neither Intrahepatic Metastasis Nor Lymph Node Metastasis Is the Optimal Indication for Hepatectomy With Adjuvant Therapy.

Background/Aim: The optimal indication of hepatectomy with adjuvant therapy for intrahepatic cholangiocarcinoma (ICC) has not been evaluated in detail. Patients and Methods: We retrospectively studied 224 patients with ICC who underwent hepatectomy between 2000 and 2019. Prognostic factors for overall survival (OS) were evaluated by univariate and multivariate analysis. A total of 127 patients were treated with adjuvant therapy (62 patients with chemotherapy and 65 patients with immunotherapy) after hepatectomy, and 97 patients were treated with hepatectomy alone. Results: Intrahepatic metastasis (IM), lymph node metastasis (LNM) of ICC, adjuvant chemotherapy, and adjuvant immunotherapy were significant prognostic factors for OS on multivariate analysis. In 127 patients with neither IM nor LNM, the 5-year OS rate was significantly higher in 36 patients with adjuvant chemotherapy (81%) and in 34 patients with adjuvant immunotherapy (68%) than in 57 patients with hepatectomy alone (45%). Conclusion: The absence of IM or LNM is the optimal indication for hepatectomy with adjuvant therapy in patients with ICC.

Inhibiting SCAP/SREBP exacerbates liver injury and carcinogenesis in murine nonalcoholic steatohepatitis.

Enhanced de novo lipogenesis mediated by sterol regulatory element-binding proteins (SREBPs) is thought to be involved in nonalcoholic steatohepatitis (NASH) pathogenesis. In this study, we assessed the impact of SREBP inhibition on NASH and liver cancer development in murine models. Unexpectedly, SREBP inhibition via deletion of the SREBP cleavage-activating protein (SCAP) in the liver exacerbated liver injury, fibrosis, and carcinogenesis despite markedly reduced hepatic steatosis. These phenotypes were ameliorated by restoring SREBP function. Transcriptome and lipidome analyses revealed that SCAP/SREBP pathway inhibition altered the fatty acid (FA) composition of phosphatidylcholines due to both impaired FA synthesis and disorganized FA incorporation into phosphatidylcholine via lysophosphatidylcholine acyltransferase 3 (LPCAT3) downregulation, which led to endoplasmic reticulum (ER) stress and hepatocyte injury. Supplementation with phosphatidylcholines significantly improved liver injury and ER stress induced by SCAP deletion. The activity of the SCAP/SREBP/LPCAT3 axis was found to be inversely associated with liver fibrosis severity in human NASH. SREBP inhibition also cooperated with impaired autophagy to trigger liver injury. Thus, excessively strong and broad lipogenesis inhibition was counterproductive for NASH therapy; this will have important clinical implications in NASH treatment.

Clinicopathological Features of Gastric Cancer with Autoimmune Gastritis.

Most gastric cancers develop in patients with chronic gastritis. Chronic gastritis can be classified into two major subtypes: Helicobacter pylori (H. pylori)-induced gastritis and autoimmune gastritis (AIG). Whereas H. pylori-related gastric cancers are more common and have been extensively investigated, the clinicopathological features of gastric cancer with autoimmune gastritis are unclear. Patients diagnosed with gastric cancer and hospitalized in the University Tokyo Hospital from 1998 to 2017 were enrolled. Diagnosis of autoimmune gastritis was based on positivity for serum anti-parietal cell antibody (APCA). We evaluated mucin expression and immune cell infiltration by immunohistochemical staining for MUC5AC, MUC6, PD-L1, CD3, CD11, Foxp3, and PD1. We also examined the presence of bacterial taxa that are reportedly enriched in AIG. Survival analyses of recurrence and 5-year mortality were also performed. In total, 261 patients (76 APCA-positive and 185 APCA-negative) were analyzed. Immunohistochemical staining in the matched cohort showed that AIG-related gastric cancer had higher MUC5AC expression (p = 0.0007) and MUC6 expression (p = 0.0007). Greater infiltration of CD3-positive (p = 0.001), Foxp3-positive (p < 0.001), and PD1-positive cells (p = 0.001); lesser infiltration of CD11b-positive (p = 0.005) cells; and a higher prevalence of Bacillus cereus (p = 0.006) were found in AIG-related gastric cancer patients. The cumulative incidences of gastric cancer recurrence were 2.99% at 2 years, 15.68% at 6 years, and 18.81% at 10 years in APCA-positive patients; they were 12.79% at 2 years, 21.35% at 6 years, and 31.85% at 10 years in APCA-negative patients. The cumulative incidences of mortality were 0% at 3 years and 0% at 5 years in APCA-positive patients; they were 1.52% at 3 years and 2.56% at 5 years in APCA-negative patients. We identified molecular differences between AIG and non-AIG gastric cancer. Differences in T-cell populations and the gastric microbiota may contribute to the pathogenesis of gastric cancers and potentially affect the response to immunotherapy.

Machine learning-based personalized prediction of gastric cancer incidence using the endoscopic and histologic findings at the initial endoscopy.

BACKGROUND AND AIMS: Accurate risk stratification for gastric cancer is required for optimal endoscopic surveillance in patients with chronic gastritis. We aimed to develop a machine learning (ML) model that incorporates endoscopic and histologic findings for an individualized prediction of gastric cancer incidence. METHODS: We retrospectively evaluated 1099 patients with chronic gastritis who underwent EGD and biopsy sampling of the gastric mucosa. Patients were randomly divided into training and test sets (4:1). We constructed a conventional Cox proportional hazard model and 3 ML models. Baseline characteristics, endoscopic atrophy, and Operative Link on Gastritis-Intestinal Metaplasia Assessment (OLGIM)/Operative Link on Gastritis Assessment (OLGA) stage at initial EGD were comprehensively assessed. Model performance was evaluated using Harrel's c-index. RESULTS: During a mean follow-up of 5.63 years, 94 patients (8.55%) developed gastric cancer. The gradient-boosting decision tree (GBDT) model achieved the best performance (c-index from the test set, .84) and showed high discriminative ability in stratifying the test set into 3 risk categories (P < .001). Age, OLGIM/OLGA stage, endoscopic atrophy, and history of malignant tumors other than gastric cancer were important predictors of gastric cancer incidence in the GBDT model. Furthermore, the proposed GBDT model enabled the generation of a personalized cumulative incidence prediction curve for each patient. CONCLUSIONS: We developed a novel ML model that incorporates endoscopic and histologic findings at initial EGD for personalized risk prediction of gastric cancer. This model may lead to the development of effective and personalized follow-up strategies after initial EGD.

MNX1-HNF1B Axis Is Indispensable for Intraductal Papillary Mucinous Neoplasm Lineages.

BACKGROUND & AIMS: Chromatin architecture governs cell lineages by regulating the specific gene expression; however, its role in the diversity of cancer development remains unknown. Among pancreatic cancers, pancreatic ductal adenocarcinoma (PDAC) and intraductal papillary mucinous neoplasms (IPMN) with an associated invasive carcinoma (IPMNinv) arise from 2 distinct precursors, and their fundamental differences remain obscure. Here, we aimed to assess the difference of chromatin architecture regulating the transcriptional signatures or biological features in pancreatic cancers. METHODS: We established 28 human organoids from distinct subtypes of pancreatic tumors, including IPMN, IPMNinv, and PDAC. We performed exome sequencing (seq), RNA-seq, assay for transposase-accessible chromatin-seq, chromatin immunoprecipitation-seq, high-throughput chromosome conformation capture, and phenotypic analyses with short hairpin RNA or clustered regularly interspaced short palindromic repeats interference. RESULTS: Established organoids successfully reproduced the histology of primary tumors. IPMN and IPMNinv organoids harbored GNAS, RNF43, or KLF4 mutations and showed the distinct expression profiles compared with PDAC. Chromatin accessibility profiles revealed the gain of stomach-specific open regions in IPMN and the pattern of diverse gastrointestinal tissues in IPMNinv. In contrast, PDAC presented an impressive loss of accessible regions compared with normal pancreatic ducts. Transcription factor footprint analysis and functional assays identified that MNX1 and HNF1B were biologically indispensable for IPMN lineages. The upregulation of MNX1 was specifically marked in the human IPMN lineage tissues. The MNX1-HNF1B axis governed a set of genes, including MYC, SOX9, and OLFM4, which are known to be essential for gastrointestinal stem cells. High-throughput chromosome conformation capture analysis suggested the HNF1B target genes to be 3-dimensionally connected in the genome of IPMNinv. CONCLUSIONS: Our organoid analyses identified the MNX1-HNF1B axis to be biologically significant in IPMN lineages.

Artificial intelligence versus expert endoscopists for diagnosis of gastric cancer in patients who have undergone upper gastrointestinal endoscopy.

AIMS: To compare endoscopy gastric cancer images diagnosis rate between artificial intelligence (AI) and expert endoscopists. PATIENTS AND METHODS: We used the retrospective data of 500 patients, including 100 with gastric cancer, matched 1:1 to diagnosis by AI or expert endoscopists. We retrospectively evaluated the noninferiority (prespecified margin 5 %) of the per-patient rate of gastric cancer diagnosis by AI and compared the per-image rate of gastric cancer diagnosis. RESULTS: Gastric cancer was diagnosed in 49 of 49 patients (100 %) in the AI group and 48 of 51 patients (94.12 %) in the expert endoscopist group (difference 5.88, 95 % confidence interval: -0.58 to 12.3). The per-image rate of gastric cancer diagnosis was higher in the AI group (99.87 %, 747 /748 images) than in the expert endoscopist group (88.17 %, 693 /786 images) (difference 11.7 %). CONCLUSIONS: Noninferiority of the rate of gastric cancer diagnosis by AI was demonstrated but superiority was not demonstrated.

Cell fate analysis of zone 3 hepatocytes in liver injury and tumorigenesis.

BACKGROUND & AIMS: Liver lobules are typically subdivided into 3 metabolic zones: zones 1, 2, and 3. However, the contribution of zonal differences in hepatocytes to liver regeneration, as well as to carcinogenic susceptibility, remains unclear. METHODS: We developed a new method for sustained genetic labelling of zone 3 hepatocytes and performed fate tracing to monitor these cells in multiple mouse liver tumour models. RESULTS: We first examined changes in the zonal distribution of the Wnt target gene Axin2 over time using Axin2-Cre ERT2 ;Rosa26-Lox-Stop-Lox-tdTomato mice (Axin2;tdTomato). We found that following tamoxifen administration at 3 weeks of age, approximately one-third of total hepatocytes that correspond to zone 3 were labelled in Axin2;tdTomato mice; the tdTomato+ cell distribution closely matched that of the zone 3 marker CYP2E1. Cell fate analysis revealed that zone 3 hepatocytes maintained their own lineage but rarely proliferated beyond their liver zonation during homoeostasis; this indicated that our protocol enabled persistent genetic labelling of zone 3 hepatocytes. Using this system, we found that zone 3 hepatocytes generally had high neoplastic potential, which was promoted by constitutive activation of Wnt/ß-catenin signalling in the pericentral area. However, the frequency of zone 3 hepatocyte-derived tumours varied depending on the regeneration pattern of the liver parenchyma in response to liver injury. Notably, Axin2-expressing hepatocytes undergoing chronic liver injury significantly contributed to liver regeneration and possessed high neoplastic potential. Additionally, we revealed that the metabolic phenotypes of liver tumours were acquired during tumorigenesis, irrespective of their spatial origin. CONCLUSIONS: Hepatocytes receiving Wnt/ß-catenin signalling from their microenvironment have high neoplastic potential, and Wnt/ß-catenin signalling is a potential drug target for the prevention of hepatocellular carcinoma. LAY SUMMARY: Lineage tracing revealed that zone 3 hepatocytes residing in the pericentral niche have high neoplastic potential. Under chronic liver injury, hepatocytes receiving Wnt/ß-catenin signalling broadly exist across all hepatic zones and significantly contribute to liver tumorigenesis as well as liver regeneration. Wnt/ß-catenin signalling is a potential drug target for the prevention of hepatocellular carcinoma.

Axin2+ Peribiliary Glands in the Periampullary Region Generate Biliary Epithelial Stem Cells That Give Rise to Ampullary Carcinoma.

BACKGROUND & AIMS: Peribiliary glands (PBGs), clusters of epithelial cells residing in the submucosal compartment of extrahepatic bile ducts, have been suggested as biliary epithelial stem/progenitor cell niche; however, evidence to support this claim is limited because of a lack of PBG-specific markers. We therefore sought to identify PBG-specific markers to investigate the potential role of PBGs as stem/progenitor cell niches, as well as an origin of cancer. METHODS: We examined the expression pattern of the Wnt target gene Axin2 in extrahepatic bile ducts. We then applied lineage tracing to investigate whether Axin2-expressing cells from PBGs contribute to biliary regeneration and carcinogenesis using Axin2-CreERT mice. RESULTS: Wnt signaling activation, marked by Axin2, was limited to PBGs located in the periampullary region. Lineage tracing showed that Axin2-expressing periampullary PBG cells are capable of self-renewal and supplying new biliary epithelial cells (BECs) to the luminal surface. Additionally, the expression pattern of Axin2 and the mature ductal cell marker CK19 were mutually exclusive in periampullary region, and fate tracing of CK19+ luminal surface BECs showed gradual replacement by CK19- cells, further supporting the continuous replenishment of new BECs from PBGs to the luminal surface. We also found that Wnt signal enhancer R-spondin3 secreted from Myh11-expressing stromal cells, corresponding to human sphincter of Oddi, maintained the periampullary Wnt signal-activating niche. Notably, introduction of PTEN deletion into Axin2+ PBG cells, but not CK19+ luminal surface BECs, induced ampullary carcinoma whose development was suppressed by Wnt inhibitor. CONCLUSION: A specific cell population receiving Wnt-activating signal in periampullary PBGs functions as biliary epithelial stem/progenitor cells and also the cellular origin of ampullary carcinoma.

Deletion of Histone Methyltransferase G9a Suppresses Mutant Kras-driven Pancreatic Carcinogenesis.

BACKGROUND/AIM: The entire mechanisms by which epigenetic modifiers contribute to the development of pancreatic cancer remain unknown. Although the histone methyltransferase G9a is a promising target in human cancers, its role in pancreatic carcinogenesis has been under-studied. The aim of the study was to examine the role of G9a in pancreatic carcinogenesis by a gene-targeting mouse model. MATERIALS AND METHODS: We established pancreas-specific G9aflox/flox mice and crossed them with Ptf1aCre/; KrasG12D/+ (KC) mice, which spontaneously develop pancreatic cancer. The phenotypes of the resulting KC mice with G9a deletion were examined. We analyzed transcriptomic data by microarray and genome-wide chromatin accessibility by transposase-accessible chromatin using sequencing. We established pancreatic organoids from KC mice. RESULTS: G9a deficiency impaired the progression of pancreatic intraepithelial neoplasia (PanIN) and prolonged the survival of KC mice. The number of phosphorylated Erk-positive cells and Dclk1-positive cells, which are reported to be essential for the progression of PanIN, were decreased by G9a deletion. UNC0638, an inhibitor of G9a, suppressed the growth of organoids and increased global chromatin accessibility, especially around the regions including the protein phosphatase 2A genes. CONCLUSION: Thus, our study suggested the functional interaction of G9a, Dclk1 and Mapk pathway in the Kras-driven pancreatic carcinogenesis. The inhibition of G9a may suppress the initiation of oncogenic Kras-driven pancreatic carcinogenesis.