Metastasis associated in colon cancer 1 (MACC1) is a key regulator of the hepatocyte growth factor (HGF)-HGF receptor (MET) pathway, which is involved in cellular growth, epithelial-mesenchymal transition, angiogenesis, cell motility, invasiveness, and metastasis. MACC1 protein consists of four domains: ZU5, SH3, and two C-terminal death domains (DD). Expression of MACC1 was found significantly upregulated in malignant tissues (colon cancer of all stages as well as liver and lung metastases) compared to normal tissues or adenomas. MACC1 represents an early and crucial prognostic indicator for colon cancer metastasis that is independent of age, sex, tumor infiltration, nodal status, and lymph vessel invasion. Besides its involvement in signal transduction with the MET receptor, MACC1 also links MET signaling and apoptosis. MACC1 may also be an important therapeutic target for colorectal cancer treatment. At least two isoforms of MACC1 are known to exist.