Dataset Information

DDIT4 Licenses Only Healthy Cells to Proliferate During Injury-induced Metaplasia.

ABSTRACT:

Background and aims

In stomach, metaplasia can arise from differentiated chief cells that become mitotic via paligenosis, a stepwise program. In paligenosis, mitosis initiation requires reactivation of the cellular energy hub mTORC1 after initial mTORC1 suppression by DNA damage induced transcript 4 (DDIT4 aka REDD1). Here, we use DDIT4-deficient mice and human cells to study how metaplasia increases tumorigenesis risk.

Methods

A tissue microarray of human gastric tissue specimens was analyzed by immunohistochemistry for DDIT4. C57BL/6 mice were administered combinations of intraperitoneal injections of high-dose tamoxifen (TAM) to induce spasmolytic polypeptide-expressing metaplasia (SPEM) and rapamycin to block mTORC1 activity, and N-methyl-N-nitrosourea (MNU) in drinking water to induce spontaneous gastric tumors. Stomachs were analyzed for proliferation, DNA damage, and tumor formation. CRISPR/Cas9-generated DDIT4^-/- and control human gastric cells were analyzed for growth in vitro and in xenografts with and without 5-fluorouracil (5-FU) treatment.

Results

DDIT4 was expressed in normal gastric chief cells in mice and humans and decreased as chief cells became metaplastic. Paligenotic Ddit4^-/- chief cells maintained constitutively high mTORC1, causing increased mitosis of metaplastic cells despite DNA damage. Lower DDIT4 expression correlated with longer survival of patients with gastric cancer. 5-FU-treated DDIT4^-/- human gastric epithelial cells had significantly increased cells entering mitosis despite DNA damage and increased proliferation in vitro and in xenografts. MNU-treated Ddit4^-/- mice had increased spontaneous tumorigenesis after multiple rounds of paligenosis induced by TAM.

Conclusions

During injury-induced metaplastic proliferation, failure of licensing mTORC1 reactivation correlates with increased proliferation of cells harboring DNA damage, as well as increased tumor formation and growth in mice and humans.

SUBMITTER: Miao ZF

PROVIDER: S-EPMC7857017 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background & aimsAdult zymogen-producing (zymogenic) chief cells (ZCs) in the mammalian gastric gland base are believed to arise from descending mucous neck cells, which arise from stem cells. Gastric injury, such as from Helicobacter pylori infection in patients with chronic atrophic gastritis, can cause metaplasia, characterized by gastric cell expression of markers of wound-healing; these cells are called spasmolytic polypeptide-expressing metaplasia (SPEM) cells. We investigated differentiation and proliferation patterns of neck cells, ZCs, and SPEM cells in mice.MethodsC57BL/6 mice were given intraperitoneal injections of high-dose tamoxifen to induce SPEM or gavaged with H pylori (PMSS1) to induce chronic gastric injury. Mice were then given pulses of 5-bromo-2'-deoxyuridine (BrdU) in their drinking water, followed by chase periods without BrdU, or combined with intraperitoneal injections of 5-ethynyl-2'-deoxyuridine. We collected gastric tissues and performed immunofluorescence and immunohistochemical analyses to study gastric cell proliferation, differentiation, and turnover.ResultsAfter 8 weeks of continuous BrdU administration, fewer than 10% of homeostatic ZCs incorporated BrdU, whereas 88% of neck cells were labeled. In pulse-chase experiments, various chase periods decreased neck cell label but did not increase labeling of ZCs. When mice were given BrdU at the same time as tamoxifen, more than 90% of cells were labeled in all gastric lineages. After 3 months' recovery (no tamoxifen), ZCs became the predominant BrdU-labeled population, whereas other cells, including neck cells, were mostly negative. When we tracked the labeled cells in such mice over time, we observed that the proportion of BrdU-positive ZCs remained greater than 60% up to 11 months. In mice whose ZCs were the principal BrdU-positive population, acute injury by tamoxifen or chronic injury by H pylori infection resulted in SPEM cells becoming the principal BrdU-positive population. After withdrawal of tamoxifen, BrdU-positive ZCs reappeared.ConclusionsWe studied mice in homeostasis or with tamoxifen- or H pylori-induced SPEM. Our findings indicated that mucous neck cells do not contribute substantially to generation of ZCs during homeostasis and that ZCs maintain their own census, likely through infrequent self-replication. After metaplasia-inducing injury, ZCs can become SPEM cells, and then redifferentiate into ZCs on injury resolution.