Supplementary Material for: Germline Missense Mutation of Deleted in Malignant Brain Tumor 1 (DMBT1) in Familial Mediastinal Neuroendocrine Cancer and in vitro Effects in Thyroid Cancer Cells

Background: Neuroendocrine tumors (NETs) rarely occur in the mediastinum and their etiology and pathogenesis are still unclear. Objectives: This study assessed inherited or de novo mutations in familial mediastinal NETs. Method: DNA samples from 4 patients were subjected to the whole-exome sequencing, and Sanger sequencing was used to identify Deleted in malignant brain tumor 1 (DMBT1) mutations in all 45 family members. Results: All patients showed a germline DMBT1 mutation at 4971C. Sanger sequencing data showed that 4 NETs and 2 carriers in the first patient’s family and 2 NETs and 4 carriers in the second patient’s family, respectively, had this DMBT1 mutation. The in vitro data showed that the ectopic expression of DMBT1 reduced tumor cell viability and migration by arresting the G1/S phase of the cell cycle. Conclusions: We identified a germline missense mutation in DMBT1^D1657E as a susceptibility gene for familial mediastinal NETs.