1 3625 206 IN VIVO GENOME AND METHYLOME ADAPTATION OF CAG-NEGATIVE HELICOBACTER PYLORI DURING EXPERIMENTAL HUMAN INFECTION. MULTIPLE STUDIES HAVE DEMONSTRATED RAPID BACTERIAL GENOME EVOLUTION DURING CHRONIC INFECTION WITH HELICOBACTER PYLORI IN CONTRAST, LITTLE WAS KNOWN ABOUT GENETIC CHANGES DURING THE FIRST STAGES OF INFECTION, WHEN SELECTIVE PRESSURE IS LIKELY TO BE HIGHEST. USING SINGLE-MOLECULE, REAL-TIME (SMRT) AND ILLUMINA SEQUENCING TECHNOLOGIES, WE ANALYZED GENOME AND METHYLOME EVOLUTION DURING THE FIRST 10 WEEKS OF INFECTION BY COMPARING THE CAG PATHOGENICITY ISLAND (CAGPAI)-NEGATIVE H. PYLORI CHALLENGE STRAIN BCS 100 WITH PAIRS OF H. PYLORI REISOLATES FROM GASTRIC ANTRUM AND CORPUS BIOPSY SPECIMENS OF 10 HUMAN VOLUNTEERS WHO HAD BEEN INFECTED WITH THIS STRAIN AS PART OF A VACCINE TRIAL. MOST GENETIC CHANGES DETECTED IN THE REISOLATES AFFECTED GENES WITH A SURFACE-RELATED ROLE OR A PREDICTED FUNCTION IN PEPTIDE UPTAKE. APART FROM PHENOTYPIC CHANGES OF THE BACTERIAL ENVELOPE, A DUPLICATION OF THE CATALASE GENE WAS OBSERVED IN ONE REISOLATE, WHICH RESULTED IN HIGHER CATALASE ACTIVITY AND IMPROVED SURVIVAL UNDER OXIDATIVE STRESS CONDITIONS. THE METHYLOMES ALSO VARIED IN SOME OF THE REISOLATES, MOSTLY BY ACTIVITY SWITCHING OF PHASE-VARIABLE METHYLTRANSFERASE (MTASE) GENES. THE OBSERVED IN VIVO MUTATION SPECTRUM WAS REMARKABLE FOR A VERY HIGH PROPORTION OF NONSYNONYMOUS MUTATIONS. ALTHOUGH THE DATA SHOWED SUBSTANTIAL WITHIN-STRAIN GENOME DIVERSITY IN THE CHALLENGE STRAIN, MOST ANTRUM AND CORPUS REISOLATES FROM THE SAME VOLUNTEERS WERE HIGHLY SIMILAR TO EACH OTHER, INDICATING THAT THE CHALLENGE INFECTION REPRESENTS A MAJOR SELECTIVE BOTTLENECK SHAPING THE TRANSMITTED POPULATION. OUR FINDINGS SUGGEST RAPID IN VIVO SELECTION OF H. PYLORI DURING EARLY-PHASE INFECTION PROVIDING ADAPTATION TO DIFFERENT INDIVIDUALS BY COMMON MECHANISMS OF GENETIC AND EPIGENETIC ALTERATIONS.IMPORTANCE EXCEPTIONAL GENETIC DIVERSITY AND VARIABILITY ARE HALLMARKS OF HELICOBACTER PYLORI, BUT THE BIOLOGICAL ROLE OF THIS PLASTICITY REMAINS INCOMPLETELY UNDERSTOOD. HERE, WE HAD THE RARE OPPORTUNITY TO INVESTIGATE THE MOLECULAR EVOLUTION DURING THE FIRST WEEKS OF H. PYLORI INFECTION BY COMPARING THE GENOMES AND EPIGENOMES OF H. PYLORI STRAIN BCS 100 USED TO CHALLENGE HUMAN VOLUNTEERS IN A VACCINE TRIAL WITH THOSE OF BACTERIA REISOLATED FROM THE VOLUNTEERS 10 WEEKS AFTER THE CHALLENGE. THE DATA PROVIDE MOLECULAR INSIGHTS INTO THE PROCESS OF ESTABLISHMENT OF THIS HIGHLY VERSATILE PATHOGEN IN 10 DIFFERENT HUMAN INDIVIDUAL HOSTS, SHOWING, FOR EXAMPLE, SELECTION FOR CHANGES IN HOST-INTERACTION MOLECULES AS WELL AS CHANGES IN EPIGENETIC METHYLATION PATTERNS. THE DATA PROVIDE IMPORTANT CLUES TO THE EARLY ADAPTATION OF H. PYLORI TO NEW HOST NICHES AFTER TRANSMISSION, WHICH WE BELIEVE IS VITAL TO UNDERSTAND ITS SUCCESS AS A CHRONIC PATHOGEN AND DEVELOP MORE EFFICIENT TREATMENTS AND VACCINES. 2020 2 3232 29 HELICOBACTER PYLORI-INDUCED SIGNALING PATHWAYS CONTRIBUTE TO INTESTINAL METAPLASIA AND GASTRIC CARCINOGENESIS. HELICOBACTER PYLORI (H. PYLORI) INDUCES CHRONIC GASTRIC INFLAMMATION, ATROPHIC GASTRITIS, INTESTINAL METAPLASIA, AND CANCER. ALTHOUGH THE RISK OF GASTRIC CANCER INCREASES EXPONENTIALLY WITH THE EXTENT OF ATROPHIC GASTRITIS, THE PRECISE MECHANISMS OF GASTRIC CARCINOGENESIS HAVE NOT BEEN FULLY ELUCIDATED. H. PYLORI INDUCES GENETIC AND EPIGENETIC CHANGES IN GASTRIC EPITHELIAL CELLS THROUGH ACTIVATING INTRACELLULAR SIGNALING PATHWAYS IN A CAGPAI-DEPENDENT MANNER. H. PYLORI EVENTUALLY INDUCES GASTRIC CANCER WITH CHROMOSOMAL INSTABILITY (CIN) OR MICROSATELLITE INSTABILITY (MSI), WHICH ARE CLASSIFIED AS TWO MAJOR SUBTYPES OF GASTRIC CANCER. ELUCIDATION OF THE PRECISE MECHANISMS OF GASTRIC CARCINOGENESIS WILL ALSO BE IMPORTANT FOR CANCER THERAPY. 2015 3 2429 43 EPIGENETIC SILENCING OF MIR-137 IS A FREQUENT EVENT IN GASTRIC CARCINOGENESIS. MICRORNAS (MIRNA) ARE INVOLVED IN POSTTRANSCRIPTIONAL REGULATION OF GENE EXPRESSION AND ARE DYSREGULATED DURING CARCINOGENESIS. CPG ISLAND METHYLATION OF MIR-137 IS A COMMON EVENT IN DIFFERENT CANCERS; HOWEVER, THE ROLE OF MIR-137 IN GASTRIC CANCER (GC) REMAINS LARGELY UNEXPLORED. IN THIS STUDY WE AIMED TO CHARACTERIZE THE EPIGENETIC ALTERATIONS OF MIR-137 IN GASTRIC CARCINOGENESIS. WE ANALYZED TOTAL 295 TISSUES INCLUDING PAIRED PRIMARY GASTRIC CANCER (T-GC) WITH CORRESPONDING ADJACENT GASTRIC MUCOSA (N-GC), PAIRED PRIMARY COLORECTAL CANCER (CRC) TISSUES WITH CORRESPONDING NON-TUMOROUS MUCOSA, GASTRIC TISSUES FROM CONTROLS (N), AND PATIENTS WITH CHRONIC/ATROPHIC GASTRITIS (CG) WITH AND WITHOUT HELICOBACTER PYLORI INFECTION. BISULFITE PYROSEQUENCING AND TAQMAN RT-PCR WERE USED TO ANALYZE MIR-137 METHYLATION AND EXPRESSION, RESPECTIVELY. SURVIVAL DIFFERENCES WERE EVALUATED USING KAPLAN-MEIER ANALYSES. MIR-137 CPG ISLAND METHYLATION WAS MORE FREQUENT IN TUMOROUS COMPARED TO NON-TUMOROUS CONDITIONS AND HIGHER IN CRC THAN IN GC. IN COMPARISON TO N-GC, MIR 137 METHYLATION LEVEL WAS LOWER IN N AND CG TISSUES, WHICH CORRELATES WITH CORREAS CASCADE. MIR-137 METHYLATION INVERSELY CORRELATES WITH GLOBAL LINE-1 METHYLATION AND MIR-137 EXPRESSION. MIR-137 METHYLATION WAS HIGHER IN INTESTINAL TYPE GC COMPARED TO DIFFUSE ONE, AND HIGHER IN ANTRUM COMPARED TO CARDIA AND CORPUS, HOWEVER, MIR-137 METHYLATION WAS ASSOCIATED WITH WORSE PROGNOSIS IN DIFFUSE, BUT NOT IN INTESTINAL TYPE OF GC. THE EXPRESSION IN COLON WAS SIGNIFICANTLY HIGHER COMPARED TO ANY GASTRIC TISSUES SUGGESTING FUNCTIONAL DIFFERENCE. IN SUMMARY, MIR-137 METHYLATION IS A FREQUENT EVENT IN GASTROINTESTINAL CANCERS WHICH OCCURS EARLY IN STEPWISE MANNER DURING GASTRIC CARCINOGENESIS AND INVERSELY CORRELATES WITH GLOBAL METHYLATION. (C) 2015 WILEY PERIODICALS, INC. 2016 4 1544 42 DNA METHYLATION IN HUMAN GASTRIC EPITHELIAL CELLS DEFINES REGIONAL IDENTITY WITHOUT RESTRICTING LINEAGE PLASTICITY. BACKGROUND: EPIGENETIC MODIFICATIONS IN MAMMALIAN DNA ARE COMMONLY MANIFESTED BY DNA METHYLATION. IN THE STOMACH, ALTERED DNA METHYLATION PATTERNS HAVE BEEN OBSERVED FOLLOWING CHRONIC HELICOBACTER PYLORI INFECTIONS AND IN GASTRIC CANCER. IN THE CONTEXT OF EPIGENETIC REGULATION, THE REGIONAL NATURE OF THE STOMACH HAS BEEN RARELY CONSIDERED IN DETAIL. RESULTS: HERE, WE ESTABLISH GASTRIC MUCOSA DERIVED PRIMARY CELL CULTURES AS A RELIABLE SOURCE OF NATIVE HUMAN EPITHELIUM. WE DESCRIBE THE DNA METHYLATION LANDSCAPE ACROSS THE PHENOTYPICALLY DIFFERENT REGIONS OF THE HEALTHY HUMAN STOMACH, I.E., ANTRUM, CORPUS, FUNDUS TOGETHER WITH THE CORRESPONDING TRANSCRIPTOMES. WE SHOW THAT STABLE REGIONAL DNA METHYLATION DIFFERENCES TRANSLATE TO A LIMITED EXTENT INTO REGULATION OF THE TRANSCRIPTOMIC PHENOTYPE, INDICATING A LARGELY PERMISSIVE EPIGENETIC REGULATION. WE IDENTIFY A SMALL NUMBER OF TRANSCRIPTION FACTORS WITH NOVEL REGION-SPECIFIC ACTIVITY AND LIKELY EPIGENETIC IMPACT IN THE STOMACH, INCLUDING GATA4, IRX5, IRX2, PDX1 AND CDX2. DETAILED ANALYSIS OF THE WNT PATHWAY REVEALS DIFFERENTIAL REGULATION ALONG THE CRANIOCAUDAL AXIS, WHICH INVOLVES NON-CANONICAL WNT SIGNALING IN DETERMINING CELL FATE IN THE PROXIMAL STOMACH. BY EXTENDING OUR ANALYSIS TO PRE-NEOPLASTIC LESIONS AND GASTRIC CANCERS, WE CONCLUDE THAT EPIGENETIC DYSREGULATION CHARACTERIZES INTESTINAL METAPLASIA AS A FOUNDING BASIS FOR FUNCTIONAL CHANGES IN GASTRIC CANCER. WE PRESENT INSIGHTS INTO THE DYNAMICS OF DNA METHYLATION ACROSS ANATOMICAL REGIONS OF THE HEALTHY STOMACH AND PATTERNS OF ITS CHANGE IN DISEASE. FINALLY, OUR STUDY PROVIDES A WELL-DEFINED RESOURCE OF REGIONAL STOMACH TRANSCRIPTION AND EPIGENETICS. 2022 5 3229 32 HELICOBACTER PYLORI-INDUCED GASTRIC INFLAMMATION AND GASTRIC CANCER. HELICOBACTER PYLORI (H. PYLORI) INFECT OVER HALF OF THE WORLD'S POPULATION. THE PREVALENCE OF H. PYLORI INFECTION AND THE PREDOMINANT GENOTYPE OF H. PYLORI VIRULENCE FACTORS VARY CONSIDERABLY ACROSS DIFFERENT GEOGRAPHICAL REGIONS. H. PYLORI COULD UNIQUELY PERSIST FOR DECADES IN THE HARSH STOMACH ENVIRONMENT, WHERE IT DAMAGES THE GASTRIC MUCOSA AND CHANGES THE PATTERN OF GASTRIC HORMONE RELEASE, THEREBY AFFECTS GASTRIC PHYSIOLOGY. BY UTILIZING VARIOUS VIRULENCE FACTORS, H. PYLORI TARGETS DIFFERENT CELLULAR PROTEINS TO MODULATE THE HOST INFLAMMATORY RESPONSE AND INITIATE MULTIPLE "HITS" ON THE GASTRIC MUCOSA, RESULTING IN CHRONIC GASTRITIS AND PEPTIC ULCERATION. AMONG THE LONG-TERM CONSEQUENCES OF H. PYLORI INFECTION IS GASTRIC MALIGNANCIES, PARTICULARLY GASTRIC CANCER (GC) AND GASTRIC MUCOSA-ASSOCIATED LYMPHOID TISSUE (MALT) LYMPHOMA. AS SUCH, H. PYLORI HAS BEEN RECOGNIZED AS A CLASS I CARCINOGEN BY THE INTERNATIONAL AGENCY FOR RESEARCH ON CANCER. DESPITE A CLOSE CAUSAL LINK BETWEEN H. PYLORI INFECTION AND THE DEVELOPMENT OF GASTRIC MALIGNANCIES, THE PRECISE MECHANISMS INVOLVED IN THIS PROCESS ARE STILL OBSCURE. STUDIES OVER THE PAST TWO DECADES HAVE REVEALED THAT H. PYLORI EXERT ONCOGENIC EFFECTS ON GASTRIC MUCOSA THROUGH A COMPLEX INTERACTION BETWEEN BACTERIAL FACTORS, HOST FACTORS, AND ENVIRONMENTAL FACTORS. NUMEROUS SIGNALING PATHWAYS CAN BE ACTIVATED BY H. PYLORI. IN THIS REVIEW, WE AIM TO ELABORATE ON THE RECENT DEVELOPMENTS IN THE PATHOPHYSIOLOGICAL MECHANISMS OF H. PYLORI-INDUCED GASTRIC INFLAMMATION AND GASTRIC CANCER. 2014 6 6273 33 THE ORIGINS OF GASTRIC CANCER FROM GASTRIC STEM CELLS: LESSONS FROM MOUSE MODELS. THE CELLULAR ORIGIN OF DIGESTIVE CANCERS HAS BEEN A LONG-STANDING QUESTION IN THE CANCER FIELD. MOUSE MODELS HAVE IDENTIFIED LONG-LIVED STEM CELLS IN MOST ORGAN SYSTEMS, INCLUDING THE LUMINAL GASTROINTESTINAL TRACT, AND NUMEROUS STUDIES HAVE POINTED TO TISSUE RESIDENT STEM CELLS AS THE MAIN CELLULAR ORIGIN OF CANCER. DURING GASTRIC CARCINOGENESIS, CHRONIC INFLAMMATION INDUCES GENETIC AND EPIGENETIC ALTERATIONS IN LONG-LIVED STEM CELLS, ALONG WITH EXPANSION OF STEM CELL NICHES, EVENTUALLY LEADING TO INVASIVE CANCER. THE GASTRIC CORPUS AND ANTRUM HAVE DISTINCT STEM CELLS AND STEM CELL NICHES, SUGGESTING DIFFERENTIAL REGULATION OF CANCER INITIATION AT THE 2 SITES. IN THIS SHORT REVIEW, WE DISCUSS RECENT EXPERIMENTAL MODELS AND HUMAN STUDIES, WHICH PROVIDE IMPORTANT INSIGHTS INTO THE PATHOGENESIS OF GASTRIC CANCER. 2017 7 4984 33 PATHWAYS OF GASTRIC CARCINOGENESIS, HELICOBACTER PYLORI VIRULENCE AND INTERACTIONS WITH ANTIOXIDANT SYSTEMS, VITAMIN C AND PHYTOCHEMICALS. HELICOBACTER PYLORI IS A CLASS ONE CARCINOGEN WHICH CAUSES CHRONIC ATROPHIC GASTRITIS, GASTRIC INTESTINAL METAPLASIA, DYSPLASIA AND ADENOCARCINOMA. THE MECHANISMS BY WHICH H. PYLORI INTERACTS WITH OTHER RISK AND PROTECTIVE FACTORS, PARTICULARLY VITAMIN C IN GASTRIC CARCINOGENESIS ARE COMPLEX. GASTRIC CARCINOGENESIS INCLUDES METABOLIC, ENVIRONMENTAL, EPIGENETIC, GENOMIC, INFECTIVE, INFLAMMATORY AND ONCOGENIC PATHWAYS. THE MOLECULAR CLASSIFICATION OF GASTRIC CANCER SUBTYPES HAS REVOLUTIONIZED THE UNDERSTANDING OF GASTRIC CARCINOGENESIS. THIS INCLUDES THE TUMOUR MICROENVIRONMENT, GERMLINE MUTATIONS, AND THE ROLE OF HELICOBACTER PYLORI BACTERIA, EPSTEIN BARR VIRUS AND EPIGENETICS IN SOMATIC MUTATIONS. THERE IS EVIDENCE THAT ASCORBIC ACID, PHYTOCHEMICALS AND ENDOGENOUS ANTIOXIDANT SYSTEMS CAN MODIFY THE RISK OF GASTRIC CANCER. GASTRIC JUICE ASCORBATE LEVELS DEPEND ON DIETARY INTAKE OF ASCORBIC ACID BUT CAN ALSO BE DECREASED BY H. PYLORI INFECTION, H. PYLORI CAGA SECRETION, TOBACCO SMOKING, ACHLORHYDRIA AND CHRONIC ATROPHIC GASTRITIS. ASCORBIC ACID MAY BE PROTECTIVE AGAINST GASTRIC CANCER BY ITS ANTIOXIDANT EFFECT IN GASTRIC CYTOPROTECTION, REGENERATING ACTIVE VITAMIN E AND GLUTATHIONE, INHIBITING ENDOGENOUS N-NITROSATION, REDUCING TOXIC EFFECTS OF INGESTED NITROSODIMETHYLAMINES AND HETEROCYCLIC AMINES, AND PREVENTING H. PYLORI INFECTION. THE EFFECTIVENESS OF SUCH CYTOPROTECTION IS RELATED TO H. PYLORI STRAIN VIRULENCE, PARTICULARLY CAGA EXPRESSION. THE ROLE OF VITAMIN C IN EPIGENETIC REPROGRAMMING IN GASTRIC CANCER IS STILL EVOLVING. OTHER FACTORS IN CONJUNCTION WITH VITAMIN C ALSO PLAY A ROLE IN GASTRIC CARCINOGENESIS. ERADICATION OF H. PYLORI MAY LEAD TO RECOVERY OF VITAMIN C SECRETION BY GASTRIC EPITHELIUM AND ENABLE REGRESSION OF PREMALIGNANT GASTRIC LESIONS, THEREBY INTERRUPTING THE CORREA CASCADE OF GASTRIC CARCINOGENESIS. 2020 8 6871 31 [PATHOGENETIC IMPORTANCE OF HELICOBACTER PYLORI INFECTION]. H. PYLORI ARE ETIOLOGICAL FACTOR OF HUMAN ACUTE AND CHRONIC GASTRITIS. DEPENDING ON PATHOGENIC FACTORS OF MICROORGANISM AND POLYMORPHISM OF HUMAN GENES, CHRONIC GASTRITIS CAN BE A CAUSE FOR ULCERATIVE ENTERITIS OF THE DUODENUM OR STOMACH, GASTRIC ADENOCARCINOMA AND MALT-LYMPHOMA DEVELOPMENT. WE REVEALED GENETIC FEATURES OF BACTERIA, DETERMINED THE INTENSITY OF INFLAMMATION, SUCH AS PATHOGENIC FACTORS--CAG, PLASTIC REGION OF THE GENOME AND ADHESIN CODING GENES. EPIGENETIC CHANGES, FOR EXAMPLE THE METHYLATION OF E-CADHERIN GENE ASSOCIATED WITH H PYLORI, ARE CRUCIAL FOR CARCINOGENESIS. THEREBY, PREDISPOSITION OF CHRONIC GASTRITIS ASSOCIATED WITH H. PYLORI TO ULCERATIVE ENTERITIS OF THE DUODENUM, ULCERATIVE STOMACH DISEASE OR GASTRIC ADENOCARCINOMA DEPENDS ON TOPOGRAPHY, THE INTENSITY OF INFLAMMATION AND CHANGES OF ACID PRODUCTION IN THE STOMACH. 2012 9 3222 45 HELICOBACTER PYLORI ASSOCIATED CHRONIC GASTRITIS, CLINICAL SYNDROMES, PRECANCEROUS LESIONS, AND PATHOGENESIS OF GASTRIC CANCER DEVELOPMENT. HELICOBACTER PYLORI (H. PYLORI) INFECTION IS WELL KNOWN TO BE ASSOCIATED WITH THE DEVELOPMENT OF PRECANCEROUS LESIONS SUCH AS CHRONIC ATROPHIC GASTRITIS (AG), OR GASTRIC INTESTINAL METAPLASIA (GIM), AND CANCER. VARIOUS MOLECULAR ALTERATIONS ARE IDENTIFIED NOT ONLY IN GASTRIC CANCER (GC) BUT ALSO IN PRECANCEROUS LESIONS. H. PYLORI TREATMENT SEEMS TO IMPROVE AG AND GIM, BUT STILL REMAINS CONTROVERSIAL. IN CONTRAST, MANY STUDIES, INCLUDING META-ANALYSIS, SHOW THAT H. PYLORI ERADICATION REDUCES GC. MOLECULAR MARKERS DETECTED BY GENETIC AND EPIGENETIC ALTERATIONS RELATED TO CARCINOGENESIS REVERSE FOLLOWING H. PYLORI ERADICATION. THIS INDICATES THAT THESE CHANGES MAY BE AN IMPORTANT FACTOR IN THE IDENTIFICATION OF HIGH RISK PATIENTS FOR CANCER DEVELOPMENT. PATIENTS WHO UNDERWENT ENDOSCOPIC TREATMENT OF GC ARE AT HIGH RISK FOR DEVELOPMENT OF METACHRONOUS GC. A RANDOMIZED CONTROLLED TRIAL FROM JAPAN CONCLUDED THAT PROPHYLACTIC ERADICATION OF H. PYLORI AFTER ENDOSCOPIC RESECTION SHOULD BE USED TO PREVENT THE DEVELOPMENT OF METACHRONOUS GC, BUT RECENT RETROSPECTIVE STUDIES DID NOT SHOW THE TENDENCY. PATIENTS WITH PRECANCEROUS LESIONS (MOLECULAR ALTERATIONS) THAT DO NOT REVERSE AFTER H. PYLORI TREATMENT, REPRESENT THE "POINT OF NO RETURN" AND MAY BE AT HIGH RISK FOR THE DEVELOPMENT OF GC. THEREFORE, EARLIER H. PYLORI ERADICATION SHOULD BE CONSIDERED FOR PREVENTING GC DEVELOPMENT PRIOR TO THE APPEARANCE OF PRECANCEROUS LESIONS. 2014 10 5181 31 PREMALIGNANT LESIONS IN GASTRIC CANCER. DESPITE A PLATEAU IN INCIDENCE, GASTRIC CANCER IS ONE OF THE MOST COMMON CANCERS WORLDWIDE AND CAUSES CONSIDERABLE MORBIDITY AND MORTALITY. PREMALIGNANT GASTRIC LESIONS ARE WELL KNOWN RISK FACTORS FOR THE DEVELOPMENT OF INTESTINAL-TYPE GASTRIC ADENOCARCINOMAS. IN THIS MULTISTEP MODEL OF GASTRIC CARCINOGENESIS, HELICOBACTER PYLORI CAUSES CHRONIC ACTIVE INFLAMMATION OF THE GASTRIC MUCOSA, WHICH SLOWLY PROGRESSES THROUGH THE PREMALIGNANT STAGES OF ATROPHIC GASTRITIS, INTESTINAL METAPLASIA, AND ADENOMA/DYSPLASIA TO GASTRIC CARCINOMA. THIS PROGRESSION IS PARALLELED BY A STEPWISE ACCUMULATION OF MULTIPLE GENETIC AND EPIGENETIC ABNORMALITIES. DETECTION, TREATMENT, AND MOLECULAR ANALYSES OF PREMALIGNANT LESIONS MAY THUS PROVIDE A BASIS FOR GASTRIC CANCER PREVENTION. THIS REVIEW DESCRIBES AN OVERVIEW OF CURRENT KNOWLEDGE ON PREMALIGNANT GASTRIC LESIONS. IT ALSO REVIEWS THE ISSUE OF SURVEILLANCE OF PATIENTS WITH PREMALIGNANT LESIONS IN ORDER TO IMPROVE THE SURVIVAL OF PATIENTS WITH GASTRIC CANCER. 2010 11 4960 39 PATHOGENESIS OF PRE-NEOPLASTIC LESIONS OF THE STOMACH: TARGETS FOR PREVENTION. GASTRIC ATROPHY AND INTESTINAL METAPLASIA ARE GENERALLY CONSIDERED TO BE PRECANCEROUS LESIONS OF THE STOMACH. CHRONIC HELICOBACTER PYLORI INFECTION IS ONE THE MOST IMPORTANT FACTORS IN THE DEVELOPMENT OF THESE PRE-MALIGNANT GASTRIC LESIONS. IN ADDITION TO BACTERIAL FACTORS, POLYMORPHISMS IN THE CYTOKINE GENES OF THE HOST THAT MODULATE INFLAMMATORY RESPONSES ARE FOUND TO HAVE A SYNERGISTIC EFFECT IN THE DEVELOPMENT OF GASTRIC CANCER AS WELL AS PRE-NEOPLASTIC LESIONS. RECENTLY, INAPPROPRIATE ACTIVATION OF THE INTESTINE-SPECIFIC TRANSCRIPTION FACTOR LIKE THE HOMEOBOX GENE COMPLEX CDX1 AND CDX2 ARE FOUND TO BE AN IMPORTANT CONTRIBUTING FACTOR IN THE INDUCTION OF INTESTINAL METAPLASIA IN THE STOMACH. ABERRANT EXPRESSION OF CYCLOOXYGENASE-2 AND EPIGENETIC CHANGES ARE ALSO FREQUENTLY DETECTED IN PRE-NEOPLASTIC GASTRIC LESIONS. ONE OF THE MOST IMPORTANT QUESTIONS RELATING TO THESE PRE-NEOPLASTIC GASTRIC LESIONS IS THAT WHETHER H. PYLORI ERADICATION COULD REVERSE THESE CHANGES. HOWEVER, MOST CONTROLLED STUDIES SHOWED NO OR JUST MODEST IMPROVEMENT IN INTESTINAL METAPLASIA AFTER H. PYLORI ERADICATION. FURTHER STUDIES SHOULD EVALUATE THE ROLE OF OTHER CHEMOPREVENTIVE AGENTS, PARTICULARLY CYCLOOXYGENASE-2 INHIBITOR, ON REGRESSION OF PRE-NEOPLASTIC LESIONS. 2004 12 3223 46 HELICOBACTER PYLORI INFECTION AND AUTOIMMUNE DISEASES; IS THERE AN ASSOCIATION WITH SYSTEMIC LUPUS ERYTHEMATOSUS, RHEUMATOID ARTHRITIS, AUTOIMMUNE ATROPHY GASTRITIS AND AUTOIMMUNE PANCREATITIS? A SYSTEMATIC REVIEW AND META-ANALYSIS STUDY. AUTOIMMUNE DISEASES ARE CONSIDERED AS ONE OF THE MOST IMPORTANT DISORDERS OF THE IMMUNE SYSTEM, IN WHICH THE PROLONGED AND CHRONIC PROCESSES ELIMINATE SELF-TOLERANCE TO THE AUTO-ANTIGENS. THE PREVALENCE OF AUTOIMMUNE DISEASES HAS BEEN INCREASING WORLDWIDE IN THE RECENT YEARS. ACCORDING TO THE LITERATURE, BIOLOGICAL PROCESSES SUCH AS THE HOST GENOME, EPIGENETIC EVENTS, ENVIRONMENTAL CONDITION, DRUG CONSUMPTION, AND INFECTIOUS AGENTS ARE THE MOST IMPORTANT RISK FACTORS THAT MAKE THE HOST SUSCEPTIBLE TO THE DEVELOPMENT OF AUTOIMMUNE DISEASES. IN THE RECENT YEARS, THE ROLE OF HELICOBACTER PYLORI IN THE INDUCTION OF AUTOIMMUNE DISEASES HAS ATTRACTED EXTENSIVE ATTENTION. VIA MOLECULAR MIMICRY, EPITOPE SPREADING, BYSTANDER ACTIVATION, POLYCLONAL ACTIVATION, DYSREGULATION IN IMMUNE RESPONSE, AND HIGHLY IMMUNE-DOMINANT VIRULENCE, SUCH AS CAGA, H. PYLORI CAUSES TISSUE DAMAGE, POLARITY, AND PROLIFERATION OF THE HOST CELLS LEADING TO THE MODULATION OF HOST IMMUNE RESPONSES. MOREOVER, GIVEN THE LARGE POPULATION WORLDWIDE INFECTED WITH H. PYLORI, IT SEEMS LIKELY THAT THE BACTERIUM MAY DEVELOP INTO AUTOIMMUNE DISEASES THROUGH DYSREGULATION OF THE IMMUNE RESPONSE. THE FREQUENCY AND RELATIONSHIP BETWEEN H. PYLORI INFECTION AND SYSTEMIC LUPUS ERYTHEMATOSUS, RHEUMATOID ARTHRITIS, AUTOIMMUNE ATROPHY GASTRITIS, AND AUTOIMMUNE PANCREATITIS WERE EVALUATED USING THE DATA FROM 43 STUDIES INVOLVING 5052 PATIENTS. ACCORDING TO STATISTICAL ANALYSIS IT IS PROBABLE THAT INFECTION WITH MORE VIRULENT STRAINS OF H. PYLORI (SUCH AS H. PYLORI CAGA POSITIVE) CAN INCREASE THE RISK OF AUTOIMMUNE DISEASES. IN ADDITION, IT WAS SHOWN THAT INFECTION WITH H. PYLORI CAN PREVENT THE DEVELOPMENT OF ATROPHIC GASTRITIS BY STIMULATING INFLAMMATION IN THE GASTRIC ANTRUM. HOWEVER, FUTURE STUDIES SHOULD CONFIRM THE VALIDITY OF THIS STUDY. 2021 13 3233 35 HELICOBACTER, INFLAMMATION, AND GASTRIC CANCER. HELICOBACTER PYLORI INFECTION LEADS TO LONG-LASTING CHRONIC INFLAMMATION AND REPRESENTS THE MOST COMMON RISK FACTOR UNDERLYING GASTRIC CANCER. RECENTLY, NEW INSIGHTS INTO THE MECHANISMS THROUGH WHICH H. PYLORI AND MUCOSAL INFLAMMATION LEAD TO CANCER DEVELOPMENT HAVE EMERGED. H. PYLORI VIRULENCE FACTORS, IN PARTICULAR SPECIFIC CAGA GENOTYPES, REPRESENT MAIN FACTORS IN GASTRIC CANCER, INDUCING ALTERED INTRACELLULAR SIGNALING IN EPITHELIAL CELLS. THE CHRONIC NATURE OF H. PYLORI INFECTION APPEARS TO RELATE TO THE VACA VIRULENCE FACTOR AND TH17/TREG MECHANISMS. A ROLE OF H. PYLORI INFECTION IN EPIGENETIC AND MICRORNA DEREGULATION HAS BEEN SHOWN. MUTATION OF THE EPITHELIAL CELL GENOME, A HALLMARK OF CANCER, WAS DEMONSTRATED TO ACCUMULATE IN H. PYLORI INFECTED STOMACH PARTLY DUE TO INADEQUATE DNA REPAIR. GASTRIC STEM CELLS WERE SHOWN TO BE TARGETS OF OXIDATIVE INJURY IN THE HELICOBACTER-INFLAMMATORY MILIEU. RECENT ADVANCES EMPHASIZING THE CONTRIBUTION OF BACTERIAL FACTORS, INFLAMMATORY MEDIATORS, AND THE HOST EPITHELIAL RESPONSE IN GASTRIC CARCINOGENESIS ARE REVIEWED. 2013 14 3227 38 HELICOBACTER PYLORI INFECTION-INDUCED H3SER10 PHOSPHORYLATION IN STEPWISE GASTRIC CARCINOGENESIS AND ITS CLINICAL IMPLICATIONS. BACKGROUND: OUR PREVIOUS WORKS HAVE DEMONSTRATED THAT HELICOBACTER PYLORI (HP) INFECTION CAN ALTER HISTONE H3 SERINE 10 PHOSPHORYLATION STATUS IN GASTRIC EPITHELIAL CELLS. HOWEVER, WHETHER HELICOBACTER PYLORI-INDUCED HISTONE H3 SERINE 10 PHOSPHORYLATION PARTICIPATES IN GASTRIC CARCINOGENESIS IS UNKNOWN. WE INVESTIGATE THE EXPRESSION OF HISTONE H3 SERINE 10 PHOSPHORYLATION IN VARIOUS STAGES OF GASTRIC DISEASE AND EXPLORE ITS CLINICAL IMPLICATION. MATERIALS AND METHODS: STOMACH BIOPSY SAMPLES FROM 129 PATIENTS WERE COLLECTED AND STAINED WITH HISTONE H3 SERINE 10 PHOSPHORYLATION, KI67, AND HELICOBACTER PYLORI BY IMMUNOHISTOCHEMISTRY STAINING, EXPRESSED AS LABELING INDEX. THEY WERE CATEGORIZED INTO NONATROPHIC GASTRITIS, CHRONIC ATROPHIC GASTRITIS, INTESTINAL METAPLASIA, LOW-GRADE INTRAEPITHELIAL NEOPLASIA, HIGH-GRADE INTRAEPITHELIAL NEOPLASIA, AND INTESTINAL-TYPE GASTRIC CANCER GROUPS. HELICOBACTER PYLORI INFECTION WAS DETERMINED BY EITHER (13) C-UREA BREATH TEST OR IMMUNOHISTOCHEMISTRY STAINING. RESULTS: IN HELICOBACTER PYLORI-NEGATIVE PATIENTS, LABELING INDEX OF HISTONE H3 SERINE 10 PHOSPHORYLATION WAS GRADUALLY INCREASED IN NONATROPHIC GASTRITIS, CHRONIC ATROPHIC GASTRITIS, INTESTINAL METAPLASIA GROUPS, PEAKED AT LOW-GRADE INTRAEPITHELIAL NEOPLASIA, AND DECLINED IN HIGH-GRADE INTRAEPITHELIAL NEOPLASIA AND GASTRIC CANCER GROUPS. IN HELICOBACTER PYLORI-INFECTED PATIENTS, LABELING INDEX OF HISTONE H3 SERINE 10 PHOSPHORYLATION FOLLOWED THE SIMILAR PATTERN AS ABOVE, WITH INCREASED EXPRESSION OVER THE CORRESPONDING HELICOBACTER PYLORI-NEGATIVE CONTROLS EXCEPT IN NONATROPHIC GASTRITIS PATIENT WHOSE LABELING INDEX WAS DECREASED WHEN COMPARED WITH HELICOBACTER PYLORI-NEGATIVE CONTROL. LABELING INDEX OF KI67 IN HELICOBACTER PYLORI-NEGATIVE GROUPS WAS HIGHER IN GASTRIC CANCER THAN CHRONIC ATROPHIC GASTRITIS AND LOW-GRADE INTRAEPITHELIAL NEOPLASIA GROUPS, AND HIGHER IN INTESTINAL METAPLASIA GROUP COMPARED WITH CHRONIC ATROPHIC GASTRITIS GROUP. IN HELICOBACTER PYLORI-POSITIVE GROUPS, KI67 LABELING INDEX WAS INCREASED STEPWISE FROM NONATROPHIC GASTRITIS TO GASTRIC CANCER EXCEPT SLIGHTLY DECREASE IN CHRONIC ATROPHIC GASTRITIS GROUP. IN ADDITION, WE NOTED THAT HISTONE H3 SERINE 10 PHOSPHORYLATION STAINING IS ACCOMPANIED WITH ITS LOCATION CHANGES FROM GASTRIC GLAND BOTTOM EXPANDED TO WHOLE GLAND AS DISEASE STAGE PROGRESS. CONCLUSIONS: THESE RESULTS INDICATE THAT STEPWISE GASTRIC CARCINOGENESIS IS ASSOCIATED WITH ALTERED HISTONE H3 SERINE 10 PHOSPHORYLATION, HELICOBACTER PYLORI INFECTION ENHANCES HISTONE H3 SERINE 10 PHOSPHORYLATION EXPRESSION IN THESE PROCESSES; IT IS ALSO ACCOMPANIED WITH HISTONE H3 SERINE 10 PHOSPHORYLATION LOCATION CHANGE FROM GLAND BOTTOM STAINING EXPAND TO WHOLE GLAND EXPRESSION. THE RESULTS SUGGEST THAT EPIGENETIC DYSREGULATION MAY PLAY IMPORTANT ROLES IN HELICOBACTER PYLORI-INDUCED GASTRIC CANCER. 2018 15 3230 37 HELICOBACTER PYLORI-INDUCED INFLAMMATION AND EPIGENETIC CHANGES DURING GASTRIC CARCINOGENESIS. THE SEQUENCE OF EVENTS ASSOCIATED WITH THE DEVELOPMENT OF GASTRIC CANCER HAS BEEN DESCRIBED AS "THE GASTRIC PRECANCEROUS CASCADE". THIS CASCADE IS A DYNAMIC PROCESS THAT INCLUDES LESIONS, SUCH AS ATROPHIC GASTRITIS, INTESTINAL METAPLASIA AND DYSPLASIA. ACCORDING TO THIS MODEL, HELICOBACTER PYLORI (H. PYLORI) INFECTION TARGETS THE NORMAL GASTRIC MUCOSA CAUSING NON-ATROPHIC GASTRITIS, AN INITIATING LESION THAT CAN BE CURED BY CLEARING H. PYLORI WITH ANTIBIOTICS OR THAT MAY THEN LINGER IN THE CASE OF CHRONIC INFECTION AND PROGRESS TO ATROPHIC GASTRITIS. THE PRESENCE OF VIRULENCE FACTORS IN THE INFECTING H. PYLORI DRIVES THE CARCINOGENESIS PROCESS. INDEPENDENT EPIDEMIOLOGICAL AND ANIMAL STUDIES HAVE CONFIRMED THE SEQUENTIAL PROGRESSION OF THESE PRECANCEROUS LESIONS. PARTICULARLY LONG-TERM FOLLOW-UP STUDIES ESTIMATED A RISK OF 0.1% FOR ATROPHIC GASTRITIS/INTESTINAL METAPLASIA AND 6% IN CASE OF DYSPLASIA FOR THE LONG-TERM DEVELOPMENT OF GASTRIC CANCER. WITH THIS IN MIND, A BETTER UNDERSTANDING OF THE GENETIC AND EPIGENETIC CHANGES ASSOCIATED WITH PROGRESSION OF THE CASCADE IS CRITICAL IN DETERMINING THE RISK OF GASTRIC CANCER ASSOCIATED WITH H. PYLORI INFECTION. IN THIS REVIEW, WE WILL SUMMARIZE SOME OF THE MOST RELEVANT MECHANISMS AND FOCUS PREDOMINANTLY BUT NOT EXCLUSIVELY ON THE DISCUSSION OF GENE PROMOTER METHYLATION AND MIRNAS IN THIS CONTEXT. 2015 16 3037 72 GENOME AND METHYLOME VARIATION IN HELICOBACTER PYLORI WITH A CAG PATHOGENICITY ISLAND DURING EARLY STAGES OF HUMAN INFECTION. BACKGROUND & AIMS: HELICOBACTER PYLORI IS REMARKABLE FOR ITS GENETIC VARIATION; YET, LITTLE IS KNOWN ABOUT ITS GENETIC CHANGES DURING EARLY STAGES OF HUMAN INFECTION, AS THE BACTERIA ADAPT TO THEIR NEW ENVIRONMENT. WE ANALYZED GENOME AND METHYLOME VARIATIONS IN A FULLY VIRULENT STRAIN OF H PYLORI DURING EXPERIMENTAL INFECTION. METHODS: WE PERFORMED A RANDOMIZED PHASE I/II, OBSERVER-BLIND, PLACEBO-CONTROLLED STUDY OF 12 HEALTHY, H PYLORI-NEGATIVE ADULTS IN GERMANY FROM OCTOBER 2008 THROUGH MARCH 2010. THE VOLUNTEERS WERE GIVEN A PROPHYLACTIC VACCINE CANDIDATE (N = 7) OR PLACEBO (N = 5) AND THEN CHALLENGED WITH H PYLORI STRAIN BCM-300. BIOPSY SAMPLES WERE COLLECTED AND H PYLORI WERE ISOLATED. GENOMES OF THE CHALLENGE STRAIN AND 12 REISOLATES, OBTAINED 12 WEEKS AFTER (OR IN 1 CASE, 62 WEEKS AFTER) INFECTION WERE SEQUENCED BY SINGLE-MOLECULE, REAL-TIME TECHNOLOGY, WHICH, IN PARALLEL, PERMITTED DETERMINATION OF GENOME-WIDE METHYLATION PATTERNS FOR ALL STRAINS. FUNCTIONAL EFFECTS OF GENETIC CHANGES OBSERVED IN H PYLORI STRAINS DURING HUMAN INFECTION WERE ASSESSED BY MEASURING RELEASE OF INTERLEUKIN 8 FROM AGS CELLS (TO DETECT CAG PATHOGENICITY ISLAND FUNCTION), NEUTRAL RED UPTAKE (TO DETECT VACUOLATING CYTOTOXIN ACTIVITY), AND ADHESION ASSAYS. RESULTS: THE OBSERVED MUTATION RATE WAS IN AGREEMENT WITH RATES PREVIOUSLY DETERMINED FROM PATIENTS WITH CHRONIC H PYLORI INFECTIONS, WITHOUT EVIDENCE OF A MUTATION BURST. A LOSS OF CAG PATHOGENICITY ISLAND FUNCTION WAS OBSERVED IN 3 REISOLATES. IN ADDITION, 3 REISOLATES FROM THE VACCINE GROUP ACQUIRED MUTATIONS IN THE VACUOLATING CYTOTOXIN GENE VACA, RESULTING IN LOSS OF VACUOLIZATION ACTIVITY. WE OBSERVED INTERSTRAIN VARIATION IN METHYLOMES DUE TO PHASE VARIATION IN GENES ENCODING METHYLTRANSFERASES. CONCLUSIONS: WE ANALYZED ADAPTATION OF A FULLY VIRULENT STRAIN OF H PYLORI TO 12 DIFFERENT VOLUNTEERS TO OBTAIN A ROBUST ESTIMATE OF THE FREQUENCY OF GENETIC AND EPIGENETIC CHANGES IN THE ABSENCE OF INTERSTRAIN RECOMBINATION. OUR FINDINGS INDICATE THAT THE LARGE AMOUNT OF GENETIC VARIATION IN H PYLORI POSES A CHALLENGE TO VACCINE DEVELOPMENT. CLINICALTRIALS.GOV NO: NCT00736476. 2018 17 5180 31 PREMALIGNANT CONDITIONS OF GASTRIC CANCER. PREMALIGNANT LESIONS OF GASTRIC CANCER ENCOMPASS A VARIETY OF CONDITIONS SUCH AS CHRONIC GASTRITIS, INTESTINAL METAPLASIA AND DYSPLASIA, IN WHICH ELEVATED RISK OF DEVELOPING GASTRIC CANCER HAVE BEEN DOCUMENTED. AMONG THEM, INTESTINAL METAPLASIA IS FREQUENTLY ENCOUNTERED IN OUR DAILY ENDOSCOPIC EXAMINATION, YET ITS CLINICAL SIGNIFICANCE IS OFTEN UNDERESTIMATED DESPITE OF A NUMBER OF REPORTS DEMONSTRATING GENETIC AND EPIGENETIC ALTERATIONS IN THE INTESTINAL METAPLASTIC MUCOSA. IN THIS REVIEW, I WILL DESCRIBE THE MOLECULAR MECHANISMS OF PHENOTYPIC CHANGES FROM GASTRIC MUCOSA TO INTESTINAL METAPLASIA BASED ON OUR ANALYSIS OF MOUSE MODEL OF INTESTINAL METAPLASIA GENERATED BY ECTOPIC EXPRESSION OF CDX2 IN CONJUNCTION WITH THE STUDIES WITH HUMAN INTESTINAL METAPLASIA. 2013 18 3225 42 HELICOBACTER PYLORI INFECTION INTRODUCES DNA DOUBLE-STRAND BREAKS IN HOST CELLS. GASTRIC CANCER IS AN INFLAMMATION-RELATED MALIGNANCY RELATED TO LONG-STANDING ACUTE AND CHRONIC INFLAMMATION CAUSED BY INFECTION WITH THE HUMAN BACTERIAL PATHOGEN HELICOBACTER PYLORI. INFLAMMATION CAN RESULT IN GENOMIC INSTABILITY. HOWEVER, THERE ARE CONSIDERABLE DATA THAT H. PYLORI ITSELF CAN ALSO PRODUCE GENOMIC INSTABILITY BOTH DIRECTLY AND THROUGH EPIGENETIC PATHWAYS. OVERALL, THE MECHANISMS OF H. PYLORI-INDUCED HOST GENOMIC INSTABILITIES REMAIN POORLY UNDERSTOOD. WE USED MICROARRAY SCREENING OF H. PYLORI-INFECTED HUMAN GASTRIC BIOPSY SPECIMENS TO IDENTIFY CANDIDATE GENES INVOLVED IN H. PYLORI-INDUCED HOST GENOMIC INSTABILITIES. WE FOUND UPREGULATION OF ATM EXPRESSION IN VIVO IN GASTRIC MUCOSAL CELLS INFECTED WITH H. PYLORI. USING GASTRIC CANCER CELL LINES, WE CONFIRMED THAT THE H. PYLORI-RELATED ACTIVATION OF ATM WAS DUE TO THE ACCUMULATION OF DNA DOUBLE-STRAND BREAKS (DSBS). DSBS WERE OBSERVED FOLLOWING INFECTION WITH BOTH CAG PATHOGENICITY ISLAND (PAI)-POSITIVE AND -NEGATIVE STRAINS, BUT THE EFFECT WAS MORE ROBUST WITH CAG PAI-POSITIVE STRAINS. THESE RESULTS ARE CONSISTENT WITH THE FACT THAT INFECTIONS WITH BOTH CAG PAI-POSITIVE AND -NEGATIVE STRAINS ARE ASSOCIATED WITH GASTRIC CARCINOGENESIS, BUT THE RISK IS HIGHER IN INDIVIDUALS INFECTED WITH CAG PAI-POSITIVE STRAINS. 2014 19 4725 39 NORMAL GASTRIC TISSUE HELICOBACTER PYLORI INFECTION IS ASSOCIATED WITH EPIGENETIC AGE ACCELERATION, INCREASED MITOTIC TICK RATE, TISSUE CELL COMPOSITION, AND NATURAL KILLER CELL METHYLATION ALTERATIONS. BACKGROUND: GASTRIC ADENOCARCINOMAS ARE A LEADING CAUSE OF GLOBAL MORTALITY, ASSOCIATED WITH CHRONIC INFECTION WITH HELICOBACTER PYLORI . THE MECHANISMS BY WHICH INFECTION WITH H. PYLORI CONTRIBUTES TO CARCINOGENESIS ARE NOT WELL UNDERSTOOD. RECENT STUDIES FROM SUBJECTS WITH AND WITHOUT GASTRIC CANCER HAVE IDENTIFIED SIGNIFICANT DNA METHYLATION ALTERATIONS IN NORMAL GASTRIC MUCOSA ASSOCIATED WITH H. PYLORI INFECTION AND GASTRIC CANCER RISK. HERE WE FURTHER INVESTIGATED DNA METHYLATION ALTERATIONS IN NORMAL GASTRIC MUCOSA IN GASTRIC CANCER CASES (N = 42) AND CONTROL SUBJECTS (N = 42) WITH H. PYLORI INFECTION DATA. WE ASSESSED TISSUE CELL TYPE COMPOSITION, DNA METHYLATION ALTERATIONS WITHIN CELL POPULATIONS, EPIGENETIC AGING, AND REPETITIVE ELEMENT METHYLATION. RESULTS: IN NORMAL GASTRIC MUCOSA OF BOTH GASTRIC CANCER CASES AND CONTROL SUBJECTS, WE OBSERVED INCREASED EPIGENETIC AGE ACCELERATION ASSOCIATED WITH H. PYLORI INFECTION. WE ALSO OBSERVED AN INCREASED MITOTIC TICK RATE ASSOCIATED WITH H. PYLORI INFECTION IN BOTH GASTRIC CANCER CASES AND CONTROLS. SIGNIFICANT DIFFERENCES IN IMMUNE CELL POPULATIONS ASSOCIATED WITH H. PYLORI INFECTION IN NORMAL TISSUE FROM CANCER CASES AND CONTROLS WERE IDENTIFIED USING DNA METHYLATION CELL TYPE DECONVOLUTION. WE ALSO FOUND NATURAL KILLER CELL-SPECIFIC METHYLATION ALTERATIONS IN NORMAL MUCOSA FROM GASTRIC CANCER PATIENTS WITH H. PYLORI INFECTION. CONCLUSIONS: OUR FINDINGS FROM NORMAL GASTRIC MUCOSA PROVIDE INSIGHT INTO UNDERLYING CELLULAR COMPOSITION AND EPIGENETIC ASPECTS OF H. PYLORI ASSOCIATED GASTRIC CANCER ETIOLOGY. 2023 20 3226 41 HELICOBACTER PYLORI INFECTION, ONCOGENIC PATHWAYS AND EPIGENETIC MECHANISMS IN GASTRIC CARCINOGENESIS. CHRONIC COLONIZATION OF THE HUMAN STOMACH BY HELICOBACTER PYLORI, A GRAM-NEGATIVE BACTERIUM, IS THE MAJOR CAUSE OF CHRONIC GASTRITIS, PEPTIC ULCERS AND GASTRIC CANCER. RECENT PROGRESS HAS ELUCIDATED IMPORTANT BACTERIAL AND HOST FACTORS THAT ARE RESPONSIBLE FOR H. PYLORI-INDUCED GASTRIC INFLAMMATION AND GASTRIC MALIGNANCY. H. PYLORI CYTOTOXIN-ASSOCIATED ANTIGEN A IS THE MAJOR ONCOGENIC FACTOR INJECTED INTO HOST CELLS FROM BACTERIA AND IT DISRUPTS EPITHELIAL CELL FUNCTIONS. TOGETHER WITH H. PYLORI CAG PATHOGENICITY ISLAND, IT CAUSES GENERAL INFLAMMATORY STRESS WITHIN GASTRIC MUCOSA AND ACTIVATES MULTIPLE ONCOGENIC PATHWAYS IN EPITHELIAL CELLS. A GROWING LIST OF THESE PATHWAYS INCLUDES NF-KAPPAB, ACTIVATOR PROTEIN-1, PI3K, SIGNAL TRANSDUCERS AND ACTIVATORS OF TRANSCRIPTION 3, WNT/BETA-CATENIN AND CYCLOOXYGENASE 2. H. PYLORI INDUCES EPIGENETIC ALTERATIONS, SUCH AS DNA METHYLATION AND HISTONE MODIFICATION, WHICH PLAY CRITICAL ROLES IN ONCOGENIC TRANSFORMATION. IN ADDITION, INVESTIGATIONS INTO GASTRIC STEM CELL OR PROGENITOR CELL BIOLOGY HAVE SHED LIGHT ON THE MECHANISMS THROUGH WHICH GASTRIC CANCER MAY ORIGINATE. CONTINUED INVESTIGATION IN THESE AREAS WILL YIELD NOVEL INSIGHTS AND HELP TO ELUCIDATE THE MECHANISMS OF BACTERIA-INDUCED CARCINOGENESIS. 2010