TAM receptor tyrosine kinases: expression, disease and oncogenesis in the central nervous system.

Receptor tyrosine kinases (RTKs) are cell surface proteins that tightly regulate a variety of downstream intra-cellular processes; ligand-receptor interactions result in cascades of signaling events leading to growth, proliferation, differentiation and migration. There are 58 described RTKs, which are further categorized into 20 different RTK families. When dysregulated or overexpressed, these RTKs are implicated in disordered growth, development, and oncogenesis. The TAM family of RTKs, consisting of Tyro3, Axl, and MerTK, is prominently expressed during the development and function of the central nervous system (CNS). Aberrant expression and dysregulated activation of TAM family members has been demonstrated in a variety of CNS-related disorders and diseases, including the most common but least treatable brain cancer in children and adults: glioblastoma multiforme.