Chronic Helicobacter pylori infection triggers neoplastic transformation of the gastric mucosa in a small subset of patients, but the risk factors that induce progression to gastric metaplasia have not been identified. Prior to cancer development, the oxyntic gastric glands atrophy and are replaced by metaplastic cells in response to chronic gastritis. Previously, we identified schlafen 4 (Slfn4) as a GLI1 target gene and myeloid differentiation factor that correlates with spasmolytic polypeptide-expressing metaplasia (SPEM) in mice. Here, we tested the hypothesis that migration of SLFN4-expressing cells from the bone marrow to peripheral organs predicts preneoplastic changes in the gastric microenvironment. Lineage tracing in Helicobacter-infected Slfn4 reporter mice revealed that SLFN4+ cells migrated to the stomach, where they exhibited myeloid-derived suppressor cell (MDSC) markers and acquired the ability to inhibit T cell proliferation. SLFN4+ MDSCs were not observed in infected GLI1-deficient mice. Overexpression of sonic hedgehog ligand (SHH) in infected WT mice accelerated the appearance of SLFN4+ MDSCs in the gastric corpus. Similarly, in the stomachs of H. pylori–infected patients, the human SLFN4 ortholog SLFN12L colocalized to cells that expressed MDSC surface markers CD15+CD33+HLA-DRlo. Together, these results indicate that SLFN4 marks a GLI1-dependent population of MDSCs that predict a shift in the gastric mucosa to a metaplastic phenotype.
Authors
Lin Ding, Michael M. Hayes, Amanda Photenhauer, Kathryn A. Eaton, Qian Li, Ramon Ocadiz-Ruiz, Juanita L. Merchant
(A) Peritoneal myeloid cells from WT or Gli1+/– mice were treated with IFN-γ (800 U/ml), and Slfn4 mRNA was analyzed by RT-qPCR. (B) Slfn4 mRNA expression determined after treating peritoneal cells with IFN-α (800 U/ml) or IFN-β (200 ng/ml) for 24 hours. (C) Representative image of SLFN4-tdT+ cells visualized after culturing primary myeloid cells from Slfn4-tdT mice treated ex vivo with IFN-α but no Tx, Tx but no IFN-α, or Tx with IFN-α; or Slfn4-tdT+Gli1+/– cells treated with Tx and IFN-α. Scale bars: 20 μm. Replicated with 3 mice per genotype. (D) Schematic of Slfn4 promoter, with GLI1 and IRF binding sites indicated. Primary peritoneal myeloid cells collected from WT or Gli1–/– mice were treated with recombinant mouse SHH ligand (rSHH), 100 CFU live H. felis, or both. (E) Slfn4 mRNA in WT and Gli1–/– cells; (F) Gli1 mRNA or (G) Ifna mRNA in WT primary myeloid cells. Shown for A and B and E–G are the median and interquartile range for n = 3 experiments performed in triplicate per genotype. One-way ANOVA followed by Tukey’s multiple comparisons test on log-transformed values was performed. *P < 0.05, **P < 0.01.