Signaling by LTK in cancer

Signaling by LTK in cancer LTK is a member of the anaplastic lymphoma kinase (ALK)/LTK subfamily within the insulin receptor superfamily of RTKs. LTK encodes an 864-amino-acid protein consisting of extracellular, transmembrane, and tyrosine kinase domains and a short carboxy terminus. The LTK kinase domain shares 80% identity with ALK (Roll and Reuther, 2012). The biological role of LTK is not well defined under normal physiological conditions, and unlike ALK, a clear role for LTK in cancer is also not yet well established. LTK is overexpressed in leukemia, and high expression of LTK in early-stage non-small cell lung cancer (NSCLC) has been associated with greater risk of metastasis (Mueller-Tidow et al, 2005; Roll and Reuther, 2012). More recently, a novel CLIP1-LTK fusion protein has been identified in a small proportion of NSCLC cases (Izumi et al, 2021).