RET (REarranged during Transfection) is a receptor protein tyrosine kinase, which activates multiple signal transduction pathways. RET protein is composed of three domains: an extracellular ligand-binding domain, a transmembrane domain, and a cytoplasmic tyrosine kinase domain. The RET receptor tyrosine kinase (RTK) regulates key aspects of cellular proliferation and survival by regulating the activity of the mitogen- activated protein kinase (MAPK) and PI3K/Akt signaling pathways. RET also interacts directly with other kinases such as the epidermal growth factor receptor (EGFR) and hepatocyte growth factor receptor (MET) and the focal adhesion kinase (FAK). Furthermore, BRAF and p38MAPK are downstream targets of RET. Kinase inhibitors that simultaneously inhibit RET and its downstream targets.

RET tyrosine kinase receptor presents an attractive therapeutic target for the treatment of certain cancer subsets. Deregulated RET activity has been identified as a causative factor in the development, progression and response to therapy of thyroid carcinoma. Elevated RET expression has been associated with the development of endocrine resistance in human breast cancer.