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Shirai N, Choudhary S, Houle C. Gastric Neuroendocrine Tumors With Parietal Cell Atrophy in a Long-term Carcinogenicity Study in Rats. Toxicol Pathol 2022; 50:507-511. [PMID: 35510893 DOI: 10.1177/01926233221095445] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Malignant neuroendocrine tumors were diagnosed in the stomach of two out of sixty female Sprague-Dawley rats treated for 89 weeks with a high dose of a novel, small molecule, cannabinoid-1 antagonist. The tumors were associated with parietal cell atrophy accompanied by foveolar hyperplasia of the glandular stomach mucosa. Parietal cell atrophy/foveolar hyperplasia was considered test article related at the high dose, given the higher incidence and severity relative to untreated controls, although the precise mechanism of the parietal cell atrophy was undetermined. Spontaneous gastric neuroendocrine tumors are very rare in rats, and the current cases were considered secondary to parietal cell atrophy causing reduced gastric acid secretion and subsequent overstimulation of gastrin release through a feedback loop.
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Affiliation(s)
- Norimitsu Shirai
- Drug Safety Research and Development, Pfizer Inc., Groton, Connecticut, USA
| | | | - Christopher Houle
- Drug Safety Research and Development, Pfizer Inc., Groton, Connecticut, USA
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Yoshida M. Chloroacetanilide herbicide-induced rat enterochromaffin cell tumors: a case study within the context of the IPCS framework, for analyzing the relevance of a cancer mode of action for humans. J Toxicol Pathol 2021; 34:213-222. [PMID: 34290475 PMCID: PMC8280306 DOI: 10.1293/tox.2021-0009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 03/03/2021] [Indexed: 12/31/2022] Open
Abstract
The WHO International Programme on Chemical Safety (IPCS) framework for analyzing the
relevance of a cancer mode of action (MoA) for humans (IPCS cancer-HRF) is an application
to assess human relevance of tumorigenic hazards found through rodent bioassays. The
chloroacetanilide herbicides, butachlor and alachlor, induced enterochromaffin-like (ECL)
cell tumors in rat stomachs, at the highest doses. This study analyzed the human relevance
of this tumor by applying the IPCS cancer-HRF using published data. In a postulated MoA,
early key events (KEs) included decreased mucosal thickness in the fundic region, due to
reduced parietal cells. The following KEs included increased pH of gastric acid and
hypergastrinemia, leading to enhanced cell proliferation and hyperplasia, and resulting in
the outcome of an ECL cell tumor. The data showed consistencies in dose-response and
temporal concordance with the KEs and specificity in the tumor response, providing
strengthened evidence of the KEs. While the early KE was not the same, similar MoAs have
already been established for omeprazole and ciprofloxacin. The integrated data indicated
that the postulated MoAs were biologically plausible. Alternative MoAs were excluded..
Based on sufficient evidence, an MoA was established in rats. When addressing chemically
inducible MoAs of human relevance, KEs of hypergastrinemia and trophic ECL cell
hyperplasia were judged to not be qualitatively and quantitatively plausible in humans.
The MoA in rats is unlikely to be present in humans; however, the potential effects on
parietal cells cannot be excluded. Thus, the IPCS cancer-HRF is very useful for assessing
human relevance.
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Affiliation(s)
- Midori Yoshida
- Food Safety Commission, Cabinet Office of Japan, Akasaka Park Bld 22F, 5-2-20 Akasaka, Minato-ku, Tokyo 107-6122, Japan
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Cheng M, Yan X, He J, Qiu J, Chen Q. Comparative genome analysis reveals the evolution of chloroacetanilide herbicide mineralization in Sphingomonas wittichii DC-6. Arch Microbiol 2019; 201:907-918. [PMID: 30997539 DOI: 10.1007/s00203-019-01660-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 04/11/2019] [Accepted: 04/12/2019] [Indexed: 12/13/2022]
Abstract
The environmental fate of the extensively used chloroacetanilide herbicides (CH) has been a cause of increasing concern in the past decade because of their carcinogenic properties. Although microbes play important roles in CH degradation, Sphingomonas wittichii DC-6 was the first reported CH-mineralizing bacterium. In this study, the complete genome of strain DC-6 was sequenced and comparative genomic analysis was performed using strain DC-6 and other three partial CH-degrading bacteria, Sphingobium quisquiliarum DC-2, Sphingobium baderi DE-13, and Sphingobium sp. MEA3-1. 16S rDNA phylogenetic analysis indicated that strain DC-2, MEA3-1, and DE-13 are closely related and DC-6 has relatively distant genetic relationship with the other three strains. The identified CH degradation genes responsible for the upstream and downstream pathway, including cndA, cmeH, meaXY, and meaAB, were all located in conserved DNA fragments (or genetic islands) in the vicinity of mobile element proteins. Protein BLAST in the NCBI database showed that cndA and cmeH were present in the genomes of other sequenced strains isolated from various habitats; however, the gene compositions in these host strains were completely different from those of other sphingomonads, and codon usage of genes for upstream pathway were also different from that of downstream pathway. These results showed that the upstream and downstream pathways of CH degradation in strain DC-6 have evolved by horizontal gene transfer and gene combination. In addition, the genes of the ring-cleavage pathway were not conserved and may have evolved directly from bacterial degradation of hydroxyquinol. The present study provides insights into the evolutionary strategy and microbial catabolic pathway of CH mineralization.
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Affiliation(s)
- Minggen Cheng
- Key Laboratory of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, Life Sciences College of Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China
| | - Xin Yan
- Key Laboratory of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, Life Sciences College of Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China
| | - Jian He
- Key Laboratory of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, Life Sciences College of Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China
| | - Jiguo Qiu
- Key Laboratory of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, Life Sciences College of Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China.
| | - Qing Chen
- Key Laboratory of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, Life Sciences College of Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China. .,College of Life Sciences, Zaozhuang University, Zaozhuang, 277160, Shandong, China.
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