Gastroenterology
Abstract
Transcriptional reactivation of telomerase catalytic subunit (TERT) is a frequent hallmark of cancer, occurring in 90% of human malignancies. However, specific mechanisms driving TERT reactivation remain obscure for many tumor types and in particular gastric cancer (GC), a leading cause of global cancer mortality. Here, through comprehensive genomic and epigenomic analysis of primary GCs and GC cell lines, we identified the transcription factor early B cell factor 1 (EBF1) as a TERT transcriptional repressor and inactivation of EBF1 function as a major cause of TERT upregulation. Abolishment of EBF1 function occurs through 3 distinct (epi)genomic mechanisms. First, EBF1 is epigenetically silenced via DNA methyltransferase, polycomb-repressive complex 2 (PRC2), and histone deacetylase activity in GCs. Second, recurrent, somatic, and heterozygous EBF1 DNA–binding domain mutations result in the production of dominant-negative EBF1 isoforms. Third, more rarely, genomic deletions and rearrangements proximal to the TERT promoter remobilize or abolish EBF1-binding sites, derepressing TERT and leading to high TERT expression. EBF1 is also functionally required for various malignant phenotypes in vitro and in vivo, highlighting its importance for GC development. These results indicate that multimodal genomic and epigenomic alterations underpin TERT reactivation in GC, converging on transcriptional repressors such as EBF1.
Authors
Manjie Xing, Wen Fong Ooi, Jing Tan, Aditi Qamra, Po-Hsien Lee, Zhimei Li, Chang Xu, Nisha Padmanabhan, Jing Quan Lim, Yu Amanda Guo, Xiaosai Yao, Mandoli Amit, Ley Moy Ng, Taotao Sheng, Jing Wang, Kie Kyon Huang, Chukwuemeka George Anene-Nzelu, Shamaine Wei Ting Ho, Mohana Ray, Lijia Ma, Gregorio Fazzi, Kevin Junliang Lim, Giovani Claresta Wijaya, Shenli Zhang, Tannistha Nandi, Tingdong Yan, Mei Mei Chang, Kakoli Das, Zul Fazreen Adam Isa, Jeanie Wu, Polly Suk Yean Poon, Yue Ning Lam, Joyce Suling Lin, Su Ting Tay, Ming Hui Lee, Angie Lay Keng Tan, Xuewen Ong, Kevin White, Steven George Rozen, Michael Beer, Roger Sik Yin Foo, Heike Irmgard Grabsch, Anders Jacobsen Skanderup, Shang Li, Bin Tean Teh, Patrick Tan
Abstract
Approximately half of the world’s population is infected with the stomach pathogen Helicobacter pylori. Infection with H. pylori is the main risk factor for distal gastric cancer. Bacterial virulence factors, such as the oncoprotein CagA, augment cancer risk. Yet despite high infection rates, only a fraction of H. pylori–infected individuals develop gastric cancer. This raises the question of defining the specific host and bacterial factors responsible for gastric tumorigenesis. To investigate the tumorigenic determinants, we analyzed gastric tissues from human subjects and animals infected with H. pylori bacteria harboring different CagA status. For laboratory studies, well-defined H. pylori strain B128 and its cancerogenic derivative strain 7.13, as well as various bacterial isogenic mutants were employed. We found that H. pylori compromises key tumor suppressor mechanisms: the host stress and apoptotic responses. Our studies showed that CagA induces phosphorylation of XIAP E3 ubiquitin ligase, which enhances ubiquitination and proteasomal degradation of the host proapoptotic factor Siva1. This process is mediated by the PI3K/Akt pathway. Inhibition of Siva1 by H. pylori increases survival of human cells with damaged DNA. It occurs in a strain-specific manner and is associated with the ability to induce gastric tumor.
Authors
Manikandan Palrasu, Elena Zaika, Wael El-Rifai, Monica Garcia-Buitrago, Maria Blanca Piazuelo, Keith T. Wilson, Richard M. Peek Jr., Alexander I. Zaika
Abstract
Chronic pancreatitis (CP) is considered an irreversible fibroinflammatory pancreatic disease. Despite numerous animal model studies, questions remain about local immune characteristics in human CP. We profiled pancreatic immune cell characteristics in control organ donors and CP patients that included hereditary and idiopathic CP undergoing total pancreatectomy with islet auto-transplantation. Flow cytometric analysis revealed a significant increase in the frequency of CD68+ macrophages in idiopathic CP. In contrast, hereditary CP showed a significant increase in CD3+ T cell frequency, which prompted us to investigate the T cell receptor β (TCRβ) repertoire in CP and controls. TCRβ-sequencing revealed a significant increase in TCRβ repertoire diversity and reduced clonality in both CP groups versus controls. Interestingly, we observed differences in Vβ-Jβ gene family usage between hereditary and idiopathic CP and a positive correlation of TCRβ rearrangements with disease severity scores. Immunophenotyping analyses in hereditary and idiopathic CP pancreata indicate differences in innate and adaptive immune responses, which highlights differences in immunopathogenic mechanism of disease among subtypes of CP. TCR repertoire analysis further suggests a role for specific T cell responses in hereditary versus idiopathic CP pathogenesis providing new insights into immune responses associated with human CP.
Authors
Bomi Lee, Julia Z. Adamska, Hong Namkoong, Melena D. Bellin, Joshua J. Wilhelm, Gregory L. Szot, David M. Louis, Mark M. Davis, Stephen Pandol, Aida Habtezion
Abstract
Elevated pressure in the pancreatic gland is the central cause of pancreatitis following abdominal trauma, surgery, endoscopic retrograde cholangiopancreatography (ERCP), and gallstones. In the pancreas excessive intracellular calcium causes mitochondrial dysfunction, premature zymogen activation, and necrosis ultimately leading to pancreatitis. Although stimulation of the mechanically activated, calcium-permeable ion channel, Piezo1, in the pancreatic acinar cell is the initial step in pressure-induced pancreatitis, activation of Piezo1 produces only transient elevation in intracellular calcium that is insufficient to cause pancreatitis. Therefore, how pressure produces a prolonged calcium elevation necessary to induce pancreatitis is unknown. We demonstrate that Piezo1 activation in pancreatic acinar cells caused a prolonged elevation in intracellular calcium levels, mitochondrial depolarization, intracellular trypsin activation, and cell death. Notably, these effects were dependent on the degree and duration of force applied to the cell. Low or transient force were insufficient to activate these pathological changes whereas higher and prolonged application of force triggered sustained elevation in intracellular calcium leading to enzyme activation and cell death. All of these pathological events were rescued in acinar cells treated with a Piezo1 antagonist and in acinar cells from mice with genetic deletion of Piezo1. We discovered that Piezo1 stimulation triggered TRPV4 channel opening which was responsible for the sustained elevation in intracellular calcium that caused intracellular organelle dysfunction. Moreover, TRPV4 gene knockout mice were protected from Piezo1 agonist- and pressure-induced pancreatitis. These studies unveil a calcium signaling pathway in which Piezo1-induced TRPV4 channel opening causes pancreatitis.
Authors
Sandip M. Swain, Joelle M.J. Romac, Rafiq A. Shahid, Stephen J. Pandol, Wolfgang Liedtke, Steven R. Vigna, Rodger A. Liddle
Abstract
Visceral adipose tissue plays a critical role in numerous diseases. While imaging studies often show adipose involvement in abdominal diseases, their outcomes may vary from being a mild self limited illness to one with systemic inflammation and organ failure. We therefore compared the pattern of visceral adipose injury during acute pancreatitis and acute diverticulitis to determine its role in organ failure. Acute pancreatitis-associated adipose tissue had ongoing lipolysis in the absence of adipocyte triglyceride lipase (ATGL). Pancreatic lipase injection into mouse visceral adipose tissue hydrolyzed adipose triglyceride and generated excess non-esterified fatty acids (NEFA), which caused organ failure in the absence of acute pancreatitis. Pancreatic triglyceride lipase (PNLIP) increased in adipose tissue during pancreatitis and entered adipocytes by multiple mechanisms, hydrolyzing adipose triglyceride and generating excessive NEFA. During pancreatitis, obese PNLIP knockout mice, unlike obese adipocyte-specific ATGL knockouts, had lower visceral adipose tissue lipolysis, milder inflammation, lesser organ failure, and improved survival. PNLIP knockout mice, unlike ATGL knockouts, were protected from adipocyte-induced pancreatic acinar injury without affecting NEFA signaling or acute pancreatitis induction. Therefore during pancreatitis, unlike diverticulitis, PNLIP leaked into visceral adipose tissue can cause excessive visceral adipose tissue lipolysis independent of adipocyte-autonomous ATGL, and thereby worsen organ failure.
Authors
Cristiane de Oliveira, Biswajit Khatua, Pawan Noel, Sergiy Kostenko, Arup Bag, Bijinu Balakrishnan, Krutika S. Patel, Andre A. Guerra, Melissa N. Martinez, Shubham Trivedi, Ann E. McCullough, Dora M. Lam-Himlin, Sarah Navina, Douglas O. Faigel, Norio Fukami, Rahul Pannala, Anna Evans Phillips, Georgios I. Papachristou, Erin E. Kershaw, Mark E. Lowe, Vijay P. Singh
Abstract
Bruton tyrosine kinase (BTK) is present in a wide variety of cells and may thus have important non-B cell functions. Here we explored the function of this kinase in macrophages with studies of its regulation of the NLRP3 inflammasome. We found that bone marrow-derived macrophages (BMDMs) from BTK-deficient mice or monocytes from X-linked agammaglobulinemia patients exhibit increased NLRP3 inflammasome activity; this was also the case with BMDMs exposed to low doses of BTK inhibitor such as ibrutinib and monocytes from chronic lymphocytic leukemia patients being treated with ibrutinib. In mechanistic studies, we found that BTK binds to NLRP3 during the priming phase of inflammasome activation and in doing so inhibits LPS/nigericin-induced assembly of the NLRP3 inflammasome during the activation phase of inflammasome activation. This inhibitory effect was caused by BTK inhibition of PP2A-mediated dephosphorylation of Ser5 in the pyrin domain of NLRP3. Finally, we showed that BTK-deficient mice are subject to severe experimental colitis and such colitis is normalized by administration of anti-IL-β or an inhibitor of IL-1β signaling, anakinra. Together, these studies strongly suggest that BTK functions as a physiologic inhibitor of NLRP3 inflammasome activation; they thereby explain the fact that XLA patients are prone to develop Crohn’s disease.
Authors
Liming Mao, Atsushi Kitani, Eitaro Hiejima, Kim Montgomery-Recht, Wenchang Zhou, Ivan Fuss, Adrian Wiestner, Warren Strober
Abstract
An excess of fecal bile acids (BAs) is thought to be one of the mechanisms for diarrhea-predominant irritable bowel syndrome (IBS-D). However, the factors causing excessive BA excretion remain incompletely studied. Given the importance of gut microbiota in BA metabolism, we hypothesized that gut dysbiosis might contribute to excessive BA excretion in IBS-D. By performing BA-related metabolic and metagenomic analyses in 290 IBS-D patients and 89 healthy volunteers, we found that 24.5% of IBS-D patients exhibited excessive excretion of total BAs and alteration of BA-transforming bacteria in feces. Notably, the increase in Clostridia bacteria (e.g., C. scindens) was positively associated with the levels of fecal BAs and serum 7α-hydroxy-4-cholesten-3-one (C4), but negatively correlated with serum fibroblast growth factor 19 (FGF19) concentration. Furthermore, colonization with Clostridia-rich IBS-D fecal microbiota or C. scindens individually enhanced serum C4 and hepatic conjugated BAs but reduced ileal FGF19 expression in mice. Inhibition of Clostridium species with vancomycin yielded opposite results. Clostridia-derived BAs suppressed the intestinal FGF19 expression in vitro and in vivo. In conclusion, this study demonstrates that the Clostridia-rich microbiota contributes to excessive BA excretion in IBS-D patients, which provides a mechanistic hypothesis with testable clinical implications.
Authors
Ling Zhao, Wei Yang, Yang Chen, Fengjie Huang, Lin Lu, Chengyuan Lin, Tao Huang, Ziwan Ning, Lixiang Zhai, Linda L.D. Zhong, Waiching Lam, Zhen Yang, Xuan Zhang, Chungwah Cheng, Lijuan Han, Qinwei Qiu, Xiaoxiao Shang, Runyue Huang, Haitao Xiao, Zhenxing Ren, Dongfeng Chen, Silong Sun, Hani El-Nezami, Zongwei Cai, Aiping Lu, Xiaodong Fang, Wei Jia, Zhaoxiang Bian
Abstract
Authors
John M. Carethers
Abstract
Inflammatory bowel disease (IBD) is a chronic inflammatory disorder with rising incidence. Diseased tissues are heavily vascularized. Surprisingly, the pathogenic impact of the vasculature in IBD and the underlying regulatory mechanisms remain largely unknown. IFN-γ is a major cytokine in IBD pathogenesis, but in the context of the disease, it is almost exclusively its immune-modulatory and epithelial cell–directed functions that have been considered. Recent studies by our group demonstrated that IFN-γ also exerts potent effects on blood vessels. Based on these considerations, we analyzed the vessel-directed pathogenic functions of IFN-γ and found that it drives IBD pathogenesis through vascular barrier disruption. Specifically, we show that inhibition of the IFN-γ response in vessels by endothelial-specific knockout of IFN-γ receptor 2 ameliorates experimentally induced colitis in mice. IFN-γ acts pathogenic by causing a breakdown of the vascular barrier through disruption of the adherens junction protein VE-cadherin. Notably, intestinal vascular barrier dysfunction was also confirmed in human IBD patients, supporting the clinical relevance of our findings. Treatment with imatinib restored VE-cadherin/adherens junctions, inhibited vascular permeability, and significantly reduced colonic inflammation in experimental colitis. Our findings inaugurate the pathogenic impact of IFN-γ–mediated intestinal vessel activation in IBD and open new avenues for vascular-directed treatment of this disease.
Authors
Victoria Langer, Eugenia Vivi, Daniela Regensburger, Thomas H. Winkler, Maximilian J. Waldner, Timo Rath, Benjamin Schmid, Lisa Skottke, Somin Lee, Noo Li Jeon, Thomas Wohlfahrt, Viktoria Kramer, Philipp Tripal, Michael Schumann, Stephan Kersting, Claudia Handtrack, Carol I. Geppert, Karina Suchowski, Ralf H. Adams, Christoph Becker, Andreas Ramming, Elisabeth Naschberger, Nathalie Britzen-Laurent, Michael Stürzl
Abstract
Currently, an effective targeted therapy for pancreatitis is still lacking. Hereditary pancreatitis (HP) is a heritable, autosomal-dominant disorder with recurrent acute pancreatitis (AP) progressing to chronic pancreatitis (CP) and a markedly increased risk of pancreatic cancer. In 1996, mutations in PRSS1 were linked to the development of HP. Here, we developed a mouse model by inserting a full-length human PRSS1R122Hgene, the most commonly mutated gene in human HP, into mice. Expression of PRSS1R122H protein in the pancreas markedly increased stress signaling pathways and exacerbated AP. After the attack of AP, all PRSS1R122H mice had disease progression to CP, with similar histologic features as those observed in human HP. By comparing PRSS1R122H mice with PRSS1WT mice as well as enzymatically inactivated Dead-PRSS1R122H mice, we unraveled that increased trypsin activity is the mechanism for R122H mutation to sensitize mice to the development of pancreatitis. We further discovered that trypsin inhibition, in combination with anti-coagulation therapy, synergistically prevented the progression to CP in PRSS1R122H mice. These animal models help us better understand the complex nature of this disease and provide powerful tools for developing and testing novel therapeutics for human pancreatitis.
Authors
Fu Gui, Yuebo Zhang, Jianhua Wan, Xianbao Zhan, Yao Yao, Yinghua Li, Ashley N. Haddock, Ji Shi, Jia Guo, Jiaxiang Chen, Xiaohui Zhu, Brandy H. Edenfield, Lu Zhuang, Cheng Hu, Ying Wang, Debabrata Mukhopadhyay, Evette S. Radisky, Lizhi Zhang, Aurelia Lugea, Stephen J. Pandol, Yan Bi, Baoan Ji
Copyright © 2020 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)