ALK

ALK (anaplastic lymphoma kinase) is a receptor tyrosine kinase family that in humans contains ALK and its close relative LTK. ALK is a single-pass receptor with a large extracellular segment rich in glycine and MAM domains and an intracellular kinase domain. Its activating ligands belong to the ALKAL family. Physiologically ALK regulates nervous system development, including sympathetic neuron and neuromuscular junction formation. ALK is a major cancer gene: chromosomal rearrangements such as EML4-ALK define a lung adenocarcinoma subtype, ALK fusions occur in anaplastic large-cell lymphoma and inflammatory myofibroblastic tumors, and activating point mutations arise in neuroblastoma. ALK inhibitors, including crizotinib, alectinib and lorlatinib, deliver durable responses in ALK-driven cancers.