Generally, upon binding the TGF-β-type receptor type I and type II, the TGF-β-receptor complex phosphorylates and activates SMAD2 or SMAD3 and forms complexes with SMAD4, then translocates into the nucleus, mediates various gene expressions and affects a range of biological functions in the tumor microenvironment. The gene discussed is SMAD2; the disease is neoplasm.