SMAD4 (MAD homologue 4 (Drosophila)), also known as DPC4 (deleted in pancreatic cancer), is a tumour suppressor gene that encodes a central mediator of transforming growth factor-β signalling1,2,3,4. Germline mutations in SMAD4 are found in over 50% of patients with familial juvenile polyposis, an autosomal dominant disorder characterized by predisposition to hamartomatous polyps and gastrointestinal cancer5,6. Dense inflammatory cell infiltrates underlay grossly normal appearing, non-polypoid colonic and gastric mucosa of patients with familial juvenile polyposis7. This prominent stromal component suggests that loss of SMAD4-dependent signalling in cells within the epithelial microenvironment has an important role in the evolution of intestinal tumorigenesis in this syndrome. Here we show that selective loss of Smad4-dependent signalling in T cells leads to spontaneous epithelial cancers throughout the gastrointestinal tract in mice, whereas epithelial-specific deletion of the Smad4 gene does not. Tumours arising within the colon, rectum, duodenum, stomach and oral cavity are stroma-rich with dense plasma cell infiltrates. Smad4-/- T cells produce abundant TH2-type cytokines including interleukin (IL)-5, IL-6 and IL-13, known mediators of plasma cell and stromal expansion. The results support the concept that cancer, as an outcome, reflects the loss of the normal communication between the cellular constituents of a given organ8, and indicate that Smad4-deficient T cells ultimately send the wrong message to their stromal and epithelial neighbours.
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The authors thank A. B. Roberts for her thoughtful reading of this manuscript and considerate support of this research. Author Contributions B.-G.K. and J.J.L. are responsible for developing the hypothesis, planning and executing experiments, including analysis of models with T-cell-specific deletion of Smad4, and for preparation of the manuscript. C.L., W.Q., X.-Y.F. and C.D. are responsible for the development of models with epithelial-specific deletion of the Smad4 gene. S.-J.K. and S.H. developed and analysed the ITF-dnS4 transgenic model. M.M. established mouse colonies with T-cell-restricted deletion of Smad4. E.M. and M.P. provided immunohistochemical analysis of plasma cell infiltrates. M.A. provided analysis of histopathology and B.K. developed immunohistochemical procedures for Smad4. L.W. contributed in the preparation of the manuscript and in the evaluation of the data.
About this article
Nature Communications (2017)