Abstract
BackgroundMucins are key components of the mucosal barrier in the stomach that protects epithelia from carcinogenic effects of chronic inflammation. Analysis of The Cancer Genome Atlas database indicated that mucin-17 (MUC17) was more highly expressed in gastric cancer (GC) specimens, with favourable prognosis for patients. To explore the underlying mechanisms, we investigated the potential role of MUC17 in controlling chronic gastric inflammation.MethodsWe initially quantified the expression of MUC17 and inflammatory factor, as well as the association of MUC17 with survive in GC using immunohistochemistry. To establish how the inflammatory factors affect MUC17 expression, we explored luciferase reporter, chromatin immunoprecipitation (ChIP), and electrophoretic mobility shift (EMSA) assays. The role and mechanism that MUC17 plays in inflammation-induced cell proliferation was examined in AGS cells with reduced MUC17 expression and MKN45 cells overexpressing a truncated MUC17.ResultsWe found MUC17 was induced by inflammatory cytokines in GC cells via CDX1upregulation. MUC17 thus inactivated NFκB to inhibit GC cell proliferation in response to pro-inflammatory cytokines. We also revealed that the function of MUC17 was dependent on its conserved epidermal growth factor domain and on downstream sequences to enable its interaction with myosin-9, resulting in a sustained regulatory feedback loop between myosin-9, p53, and RhoA, and then activation of p38 to negatively regulate the NFκB pathway in GC cells. This mechanism was also confirmed in vivo.ConclusionsOur study demonstrates MUC17 as a GC suppressor protein which has the therapeutic potential for human GC.
Highlights
Mucins are key components of the mucosal barrier in the stomach that protects epithelia from carcinogenic effects of chronic inflammation
Most gastric cancer (GC) associates with dysfunction of the mucosal barrier in the stomach, the first line of defence against pathogens and inflammation
High MUC17 mRNA expression is associated with better prognosis of GC Our analysis of TCGA_GC database revealed that the mRNA levels of MUC1 (P = 0.019), MUC12 (P < 0.001), MUC13 (P < 0.001), MUC16 (P < 0.001), and MUC17 (P = 0.004) were more highly expressed in GC tissues compared to normal tissues (Fig. 1a and Additional file 1: Figure S1)
Summary
We initially quantified the expression of MUC17 and inflammatory factor, as well as the association of MUC17 with survive in GC using immunohistochemistry. To establish how the inflammatory factors affect MUC17 expression, we explored luciferase reporter, chromatin immunoprecipitation (ChIP), and electrophoretic mobility shift (EMSA) assays. The role and mechanism that MUC17 plays in inflammation-induced cell proliferation was examined in AGS cells with reduced MUC17 expression and MKN45 cells overexpressing a truncated MUC17. All GC samples were collected from the Beijing Cancer Hospital and were evaluated by a centralized pathological review group. Cell lines and transfection AGS cells were purchased from the American Type Culture Collection (ATCC, Manassas, VA, USA), MKN45 cells were purchased from the Cobioer (Nanjing, China). AGS and MKN45 cells were cultured in Dulbecco’s modified Eagle’s medium (Gibco, Grand Island, NY, USA) with 10% or 20% fetal bovine serum (Gibco).
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