title: Novel anti-c-Mpl monoclonal antibodies identified multiple differentially glycosylated human c-Mpl proteins in megakaryocytic cells but not in human solid tumors.
abstract: Thrombopoietin and its cognate receptor, c-Mpl, are the primary molecular regulators of megakaryocytopoiesis and platelet production. To date the pattern of c-Mpl expression in human solid tumors and the distribution and biochemical properties of c-Mpl proteins in hematopoietic tissues are largely unknown. We have recently developed highly specific mouse monoclonal antibodies (MAb) against human c-Mpl. In this study we used these antibodies to demonstrate the presence of full-length and truncated human c-Mpl proteins in various megakaryocytic cell types, and their absence in over 100 solid tumor cell lines and in the 12 most common primary human tumor types. Quantitative assays showed a cell context-dependent distribution of full-length and truncated c-Mpl proteins. All forms of human c-Mpl protein were found to be modified with extensive N-linked glycosylation but different degrees of sialylation and O-linked glycosylation. Of note, different variants of full-length c-Mpl protein exhibiting differential glycosylation were expressed in erythromegakaryocytic leukemic cell lines and in platelets from healthy human donors. This work provides a comprehensive analysis of human c-Mpl mRNA and protein expression on normal and malignant hematopoietic and non-hematopoietic cells and demonstrates the multiple applications of several novel anti-c-Mpl antibodies.
authors.affiliation: Department of Hematology and Oncology, Amgen Inc., Thousand Oaks, California 91320, USA.
authors.forename: Jinghui
authors.initials: J
authors.lastname: Zhan
authors.forename: Barbara
authors.initials: B
authors.lastname: Felder
authors.forename: Aaron R
authors.initials: AR
authors.lastname: Ellison
authors.forename: Aaron
authors.initials: A
authors.lastname: Winters
authors.forename: Hossein
authors.initials: H
authors.lastname: Salimi-Moosavi
authors.forename: Sheila
authors.initials: S
authors.lastname: Scully
authors.forename: James R
authors.initials: JR
authors.lastname: Turk
authors.forename: Ping
authors.initials: P
authors.lastname: Wei
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology*; D001792:Blood Platelets; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D006031:Glycosylation; D006801:Humans; D008533:Megakaryocytes / Q000276:immunology / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000276:immunology*; D009369:Neoplasms / Q000276:immunology / Q000378:metabolism; D053628:Receptors, Thrombopoietin / Q000276:immunology*; D034061:Thrombopoiesis; D013926:Thrombopoietin
chemical_list: D000911:Antibodies, Monoclonal; D009363:Neoplasm Proteins; D053628:Receptors, Thrombopoietin; C082218:MPL protein, human; D013926:Thrombopoietin