A ligand for ALK

Abstract

The receptor tyrosine kinase ALK (anaplastic lymphoma kinase), as its name suggests, is aberrantly activated, mutated, or abundant in multiple cancers. Although widely studied in the context of cancer, the ligand that normally binds to and activates ALK in vertebrates has remained elusive. In this issue of Science Signaling, Murray and colleagues identify heparin as an ALK ligand.