SMAD4 and neoplasm: For stomach cancer, Kumar et al. reviewed risk factors including age, Helicobacter pylori infection, tobacco use, and gender [40], while Slavin et al. reported that typical tumor suppressors for this cancer type included cadherin 1 (CDH1), serine/threonine kinase 11 (STK11), and SMAD family member 4 (SMAD4) [41].