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) Schematic diagram of Slfn4-tdT (Slfn4-CreERT2 Rosa26-LSL-tdTomato) mice generated. (B) Protocol to lineage trace SLFN4-expressing cells from the bone marrow to peripheral organs. WT versus pCMV-Shh chimeric mice reconstituted with Slfn4-tdT bone marrow were treated with Tx 2 weeks prior to euthanization. Shown is the percentage of SLFN4+ cells in the (C) bone marrow, (D) spleen, and (E) corpus by flow cytometry, plotted as the median and interquartile range for n = 8–10 mice per group over 3 experiments. Kruskal-Wallis ANOVA with Dunn’s test of multiple comparisons was performed for C–E; *P < 0.05. The corpus was analyzed for (F) Slfn4 mRNA by RT-qPCR and (G) tdT, SLFN4, and GAPDH protein by Western blot for n = 8–10 mice. One-way ANOVA followed by Tukey’s multiple comparisons test on log-transformed RT-qPCR values was performed for F; **P < 0.01. UT, untreated. (H) Representative images from n = 5 pCMV-Shh mouse corpora infected for 4 months showing SLFN4-tdT red+ cells with E-cadherin (green) and DAPI. Left: original magnification, ×200. White box region enlarged in the middle (tdT and DAPI) and right (DAPI only) panels (magnification, ×1,000). Asterisks indicate granulocytic nuclear morphology. (I) Giemsa stain of SLFN4-tdT+ cells sorted from n = 3 infected pCMV-Shh mouse stomachs (original magnification, ×600) showing granulocytic and monocytic cells enumerated per 100 cells. Black box indicates enlarged region (original magnification, ×1,000).