Tumor growth factor alpha (TGF-α) is a member of the epidermal growth factor (EGF) family. TGF-α function is mediated through binding the EGF receptor (EGFR) to activate receptor tyrosine kinase signaling. TGF-α functions as a mitogen to activate epithelial cell proliferation, growth, and differentiation. In the gastric mucosa, TGF-α production inhibits gastric acid secretion and therefore plays a central role in the pathogenesis of the stomach disease. TGF-α is also produced in adult macrophages, brain cells, keratinocytes, and is widely expressed in cancer cells.