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?-Difluoromethylornithine reduces gastric carcinogenesis by causing mutations in Helicobacter pylori cagY.

ABSTRACT: Infection by Helicobacter pylori is the primary cause of gastric adenocarcinoma. The most potent H. pylori virulence factor is cytotoxin-associated gene A (CagA), which is translocated by a type 4 secretion system (T4SS) into gastric epithelial cells and activates oncogenic signaling pathways. The gene cagY encodes for a key component of the T4SS and can undergo gene rearrangements. We have shown that the cancer chemopreventive agent ?-difluoromethylornithine (DFMO), known to inhibit the enzyme ornithine decarboxylase, reduces H. pylori-mediated gastric cancer incidence in Mongolian gerbils. In the present study, we questioned whether DFMO might directly affect H. pylori pathogenicity. We show that H. pylori output strains isolated from gerbils treated with DFMO exhibit reduced ability to translocate CagA in gastric epithelial cells. Further, we frequently detected genomic modifications in the middle repeat region of the cagY gene of output strains from DFMO-treated animals, which were associated with alterations in the CagY protein. Gerbils did not develop carcinoma when infected with a DFMO output strain containing rearranged cagY or the parental strain in which the wild-type cagY was replaced by cagY with DFMO-induced rearrangements. Lastly, we demonstrate that in vitro treatment of H. pylori by DFMO induces oxidative DNA damage, expression of the DNA repair enzyme MutS2, and mutations in cagY, demonstrating that DFMO directly affects genomic stability. Deletion of mutS2 abrogated the ability of DFMO to induce cagY rearrangements directly. In conclusion, DFMO-induced oxidative stress in H. pylori leads to genomic alterations and attenuates virulence.

SUBMITTER: Sierra JC

PROVIDER: S-EPMC6421409 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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α-Difluoromethylornithine reduces gastric carcinogenesis by causing mutations in Helicobacter pylori cagY.

Sierra Johanna C JC Suarez Giovanni G Piazuelo M Blanca MB Luis Paula B PB Baker Dara R DR Romero-Gallo Judith J Barry Daniel P DP Schneider Claus C Morgan Douglas R DR Peek Richard M RM Gobert Alain P AP Wilson Keith T KT

Proceedings of the National Academy of Sciences of the United States of America 20190225 11

Infection by Helicobacter pylori is the primary cause of gastric adenocarcinoma. The most potent H. pylori virulence factor is cytotoxin-associated gene A (CagA), which is translocated by a type 4 secretion system (T4SS) into gastric epithelial cells and activates oncogenic signaling pathways. The gene cagY encodes for a key component of the T4SS and can undergo gene rearrangements. We have shown that the cancer chemopreventive agent α-difluoromethylornithine (DFMO), known t ...[more]

PMID: 30804204

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Project description:BACKGROUND & AIMS: Gastric cancer results from a combination of Helicobacter pylori (H pylori) infection, exposure to dietary carcinogens, and predisposing genetic make-up. Because the role of these factors in gastric carcinogenesis cannot be determined readily in human beings, the present study examined the role of an oral carcinogen and H pylori infection in rhesus monkeys. METHODS: Gastroscopies were performed in 23 monkeys assigned to 4 groups: controls; nitrosating carcinogen ethyl-nitro-nitrosoguanidine administration alone; and inoculation of a virulent H pylori strain alone (H), or in combination with ethyl-nitro-nitrosoguanidine (EH). Follow-up gastroscopies and biopsies were performed at 3-month intervals for 5 years for pathologic and molecular studies. RESULTS: Postinoculation, H and EH groups showed persistent infection and antral gastritis. Starting at 2 and 5 years, respectively, gastric intestinal metaplasia and intraepithelial neoplasia developed in 3 EH monkeys but in no other groups. Transcriptional analysis of biopsies at 5 years revealed group-specific expression profiles, with striking changes in EH monkeys, plus a neoplasia-specific expression profile characterized by changes in multiple cancer-associated genes. Importantly, this neoplastic profile was evident in nonneoplastic mucosa, suggesting that the identified genes may represent markers preceding cancer. CONCLUSIONS: Gastric intraglandular neoplasia is induced in primates when H pylori infection is associated with consumption of a carcinogen similar to the nitrosaminesfound in pickled vegetables, suggesting that H pylori and the carcinogen synergistically induce gastric neoplasia in primates. Monkey arrays used for analysis of the affect of Helicobacter pylori and diet on development of gastric cancer. Each RNA was hybridized against a common reference. Biopsy numbers represent the following in terms of descriptions used in publication of the paper... Each set of numbers/descriptions is organized in the following order: Biopsy#; Monkey#; Group Code on Fig 5 Biopsy #4674; AB24; E; E1 Biopsy #4684; 16G; E; E2 Biopsy #4716; 89G; H; H1 Biopsy #4724; 54H; H; H2 Biopsy #4720; 20G; H; H3 Biopsy #4710; 92F; C; C1 Biopsy #4714; 26G; C; C2 Biopsy #4712; 92G; C; C3 Biopsy #4726; 08G; H; H4 Biopsy #4722; 57G; H; H5 Biopsy #4718; 85G; H; H6 Biopsy #4694; 48H; HE NON; HE1 Biopsy #4686; 59H; HE NON; HE2 Biopsy #4690; 81G; HE NEO; HE3 Biopsy #4696; 36G; HE NEO; HE4 Biopsy #4692; 63G; HE NEO; HE5 Biopsy #4680; 76G; E; E3 Biopsy #4682; 52G; E; E4 Biopsy #4678; 15G; E; E5 Biopsy #4676; 93G; E; E6 Biopsy #4688; 47H; HE NON; HE6 A pathogenicity experiment design type is where an infective agent such as a bacterium, virus, protozoan, fungus etc. infects a host organism(s) and the infective agent is assayed. Infection: Rhesus monkeys were infected with H. pylori (+/-) Compound Based Treatment: Rhesus monkeys were treated with ENNG (N-ethyl-N-nitrosoguanidine) (+/-)

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?-Difluoromethylornithine reduces gastric carcinogenesis by causing mutations in Helicobacter pylori cagY.

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α-Difluoromethylornithine reduces gastric carcinogenesis by causing mutations in <i>Helicobacter pylori cagY</i>.

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