title: Detection of tyrosine protein kinase substrates in fresh leukemia cells and normal blood cells using an immunoblotting technique.
abstract: Kinases which phosphorylate proteins on tyrosine residues are of importance in the control of both normal and malignant cell proliferation. The receptors for a number of growth factors have intracellular domains with tyrosine protein kinase activity and several viral oncogenes code for tyrosine protein kinases. An abnormal tyrosine protein kinase has been implicated in the pathogenesis of chronic granulocytic leukemia. Using an immunoblot method and an antiphosphotyrosine antibody, we have detected substrates of tyrosine protein kinases in fresh human leukemia cells and normal blood and bone marrow cells. These substrates were present in all types of cells examined. Cells from patients with acute lymphoblastic leukemia, acute myeloid leukemia, and chronic lymphocytic leukemia contain prominent phosphotyrosine-containing protein bands with molecular weights in excess of 95 kDa. By contrast, chronic granulocytic leukemia cells, as well as normal bone marrow cells, lymphocytes, and monocytes, contain predominantly low molecular weight (less than 95 kDa) tyrosine kinase substrates. When lymphocytes were stimulated to enter cell cycle, however, high molecular weight substrates of similar molecular weights to those detected in acute lymphoblastic leukemia, acute myeloid leukemia, and chronic lymphocytic leukemia became prominent. The implications of these findings in the control of normal and malignant cell proliferation and differentiation are discussed.
authors.affiliation: Department of Haematology, Royal Free Hospital School of Medicine, London, U.K.
authors.forename: J P
authors.initials: JP
authors.lastname: Evans
authors.forename: R G
authors.initials: RG
authors.lastname: Wickremasinghe
authors.forename: A V
authors.initials: AV
authors.lastname: Hoffbrand
mesh_terms: D002469:Cell Separation; D006801:Humans; D007163:Immunosorbent Techniques; D007938:Leukemia / Q000097:blood / Q000201:enzymology*; D007945:Leukemia, Lymphoid / Q000201:enzymology; D015470:Leukemia, Myeloid, Acute / Q000201:enzymology; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism; D010835:Phytohemagglutinins / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*
chemical_list: D010835:Phytohemagglutinins; D011505:Protein-Tyrosine Kinases