ROR1 (Receptor tyrosine kinase-like orphan receptor 1), also known as neurotrophic tyrosine kinase receptor-related 1 (NTRKR1),? is a member of? the ROR family within receptor tyrosine kinases (RTK) superfamily. Two ROR family members (ROR1 and ROR2) have been identified and are characterized by the intracellular tyrosine kinase domains, highly related to those of the Trk-family receptor tyrosine kinases, and by the extracellular Frizzled-like cysteine-rich domains and kringle domains, which are common to receptors of the Wnt family members.