PTK2B and chronic myelogenous leukemia, BCR-ABL1 positive: Some neoplastic conditions arise from excessive activity of a single PTK, for example Bcr-Abl in chronic myeloid leukaemia [5], or c-kit or platelet-derived growth factor receptor-α in gastrointestinal stromal cell tumours [6], and these conditions are effectively treated using the PTK inhibitor Gleevec (Imatinib mesylate) [7].