title: Downregulation of c-Jun expression and cell cycle regulatory molecules in acute myeloid leukemia cells upon CD44 ligation.
abstract: In the present study, we investigated the mechanism of CD44 ligation with the anti-CD44 monoclonal antibody A3D8 to inhibit the proliferation of human acute myeloid leukemia (AML) cells. The effects of A3D8 on myeloid cells were associated with specific disruption of cell cycle events and induction of G0/G1 arrest. Induction of G0/G1 arrest was accompanied by an increase in the expression of p21, attenuation of pRb phosphorylation and associated with decreased Cdk2 and Cdk4 kinase activities. Since c-Jun is an important regulator of proliferation and cell cycle progression, we analysed its role in A3D8-mediated growth arrest. We observed that A3D8 treatment of AML patient blasts and HL60/U937 cells led to the downregulation of c-Jun expression at mRNA and protein level. Transient transfection studies showed the inhibition of c-jun promoter activity by A3D8, involving both AP-1 sites. Furthermore, A3D8 treatment caused a decrease in JNK protein expression and a decrease in the level of phosphorylated c-Jun. Ectopic overexpression of c-Jun in HL60 cells was able to induce proliferation and prevent the antiproliferative effects of A3D8. In summary, these data identify an important functional role of c-Jun in the induction of cell cycle arrest and proliferation arrest of myeloid leukemia cells because of the ligation of the cell surface adhesion receptor CD44 by anti-CD44 antibody. Moreover, targeting of G1 regulatory proteins and the resulting induction of G1 arrest by A3D8 may provide new insights into antiproliferative and differentiation therapy of AML.
authors.affiliation: Medicine III, University of Munich Hospital Grosshadern and GSF-Hematologikum, Germany.
authors.forename: Abdul A Peer
authors.initials: AA
authors.lastname: Zada
authors.forename: Sheo M
authors.initials: SM
authors.lastname: Singh
authors.forename: Venkateshwar A
authors.initials: VA
authors.lastname: Reddy
authors.forename: Annika
authors.initials: A
authors.lastname: Elsässer
authors.forename: Alexander
authors.initials: A
authors.lastname: Meisel
authors.forename: Torsten
authors.initials: T
authors.lastname: Haferlach
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Tenen
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hiddemann
authors.forename: Gerhard
authors.initials: G
authors.lastname: Behre
mesh_terms: D000208:Acute Disease; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000502:physiology*; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000096:biosynthesis / Q000235:genetics; D016213:Cyclins / Q000096:biosynthesis / Q000235:genetics; D016193:G1 Phase / Q000187:drug effects; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D016758:Genes, jun; D018922:HL-60 Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D018960:Hyaluronan Receptors / Q000276:immunology / Q000502:physiology*; D048031:JNK Mitogen-Activated Protein Kinases; D007951:Leukemia, Myeloid / Q000378:metabolism* / Q000473:pathology; D020928:Mitogen-Activated Protein Kinases / Q000096:biosynthesis / Q000235:genetics; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D014411:Neoplastic Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000235:genetics; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000235:genetics; D011518:Proto-Oncogene Proteins; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000502:physiology; D016192:Resting Phase, Cell Cycle / Q000187:drug effects; D018808:Transcription Factor AP-1 / Q000378:metabolism; D020298:U937 Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D018960:Hyaluronan Receptors; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D016755:Proto-Oncogene Proteins c-jun; D011993:Recombinant Fusion Proteins; D018808:Transcription Factor AP-1; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495900:CDK4 protein, human; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases