Hepatocyte growth factor (HGF) is a potent mitogen for hepatocytes and a variety of other cells, including endothelial and epithelial cells, melanocytes, and keratinocytes. It also mediates epithelial morphogenesis. HGF is the ligand for a receptor encoded by the c-met proto-oncogene. c-Met expression has been observed in tumors from many sources, including stomach, lung, breast, kidney colon, liver, and melanoma, and is associated with tumor progression and metastasis.