A Point Mutation R122C in RUNX3 Promotes the Expansion of Isthmus Stem Cells and Inhibits Their Differentiation in the Stomach. (Cell Mol Gastroenterol Hepatol, Jan 2022)

Daisuke Douchi 1Akihiro Yamamura 1Junichi Matsuo 2Jung-Won Lee 3Napat Nuttonmanit 2Yi Hui Melissa Lim 2Kazuto Suda 4Mitsuhiro Shimura 1Sabirah Chen 2ShuChin Pang 2Kazuyoshi Kohu 2Mari Kaneko 5Hiroshi Kiyonari 5Atsushi Kaneda 6Hideyuki Yoshida 7Ichiro Taniuchi 8Motomi Osato 2Henry Yang 2Michiaki Unno 9Jimmy Bok-Yan So 10Khay Guan Yeoh 11Linda Shyue Huey Chuang 12Suk-Chul Bae 3Yoshiaki Ito 13

Affiliations

1Cancer Science Institute of Singapore, National University of Singapore, Singapore; Department of Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
2Cancer Science Institute of Singapore, National University of Singapore, Singapore.
3Department of Biochemistry, School of Medicine, and Institute for Tumor Research, Chungbuk National University, Cheongju, South Korea.
4Cancer Science Institute of Singapore, National University of Singapore, Singapore; Department of Pediatric General and Urogenital Surgery, Juntendo University School of Medicine, Tokyo, Japan.
5Laboratory for Animal Resources and Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan.
6Department of Molecular Oncology, Graduate School of Medicine, Chiba University, Chiba, Japan.
7YCI Laboratory for Immunological Transcriptomics, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan.
8Laboratory for Transcriptional Regulation, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan.
9Department of Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
10Department of Surgery, National University Health System, National University of Singapore, Singapore.
11Department of Medicine, National University of Singapore, Singapore.
12Cancer Science Institute of Singapore, National University of Singapore, Singapore. Electronic address: csicshl@nus.edu.sg.
13Cancer Science Institute of Singapore, National University of Singapore, Singapore. Electronic address: csiitoy@nus.edu.sg.

Abstract

Background & aims: RUNX transcription factors play pivotal roles in embryonic development and neoplasia. We previously identified the single missense mutation R122C in RUNX3 from human gastric cancer. However, how RUNX3R122C mutation disrupts stem cell homeostasis and promotes gastric carcinogenesis remained unclear.

Methods: To understand the oncogenic nature of this mutation in vivo, we generated the RUNX3R122C knock-in mice. Stomach tissues were harvested, followed by histological and immunofluorescence staining, organoid culture, flow cytometry to isolate gastric corpus isthmus and non-isthmus epithelial cells, and RNA extraction for transcriptomic analysis.

Results: The corpus tissue of RUNX3R122C/R122C homozygous mice exhibited a precancerous phenotype such as spasmolytic polypeptide-expressing metaplasia (SPEM). We observed mucous neck cell hyperplasia, massive reduction of pit, parietal, and chief cell populations, as well as a dramatic increase in the number of rapidly proliferating isthmus stem/progenitor cells in the corpus of RUNX3R122C/R122C mice. Transcriptomic analyses of the isolated epithelial cells showed that the cell cycle-related MYC target gene signature was enriched in the corpus epithelial cells of RUNX3R122C/R122C mice compared with the wild-type corpus. Mechanistically, RUNX3R122C mutant protein disrupted the regulation of the restriction point where cells decide to enter either proliferative or quiescent state, thereby driving stem cell expansion and limiting the ability of cells to terminally differentiate.

Conclusions: RUNX3R122C missense mutation is associated with the continuous cycling of isthmus stem/progenitor cells, maturation arrest and development of a precancerous state. This work highlights the importance of RUNX3 in prevention of metaplasia and gastric cancer.

Keywords: Enhanced Stem Cell Activity; Gastric Carcinogenesis; Isthmus; Preneoplastic State; Stem/Progenitor Cell.