title: Mitogen-activated protein kinase kinase inhibition enhances nuclear proapoptotic function of p53 in acute myelogenous leukemia cells.
abstract: Activation of the Raf/MEK/ERK pathway and inactivation of wild-type p53 by Mdm2 overexpression are frequent molecular events in acute myelogenous leukemia (AML). We investigated the interaction of Raf/MEK/ERK and p53 pathways after their simultaneous blockades using a selective small-molecule antagonist of Mdm2, Nutlin-3a, and a pharmacologic MEK-specific inhibitor, PD98059. We found that PD98059, which itself has minimal apoptogenic activity, acts synergistically with Nutlin-3a to induce apoptosis in wild-type p53 AML cell lines OCI-AML-3 and MOLM-13. Interestingly, PD98059 enhanced nuclear proapototic function of p53 in these cells. In accordance with the activation of transcription-dependent apoptosis, PD98059 treatment promoted the translocation of p53 from the cytoplasm to the nucleus in OCI-AML-3 cells, in which p53 primarily initiates transcription-independent apoptosis when cells are treated with Nutlin-3a alone. The critical role of p53 localization in cells with increased p53 levels was supported by enhanced apoptosis induction in cells cotreated with Nutlin-3a and the nuclear export inhibitor leptomycin B. PD98059 prevented p53-mediated induction of p21 at the transcriptional level. The repressed expression of antiapototic p21 also seemed to contribute to synergism between PD98059 and Nutlin-3a because (a) the synergistic apoptogenic effect was preserved in G(1) cells, (b) p53-mediated induction of p21 was preferentially seen in G(1) cells, (c) PD98059 strongly antagonized p21 induction by Nutlin-3a, and (d) cells with high p21 levels were resistant to apoptosis. This is the first report showing that the Raf/MEK/ERK pathway regulates the subcellular localization of p53 and the relative contribution of transcription-dependent and transcription-independent pathways in p53-mediated apoptosis.
authors.affiliation: Section of Molecular Hematology and Therapy, Department of Stem Cell Transplantation and Cellular Therapy, M. D. Anderson Cancer Center, The University of Texas, Houston, Texas, USA.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Kojima
authors.forename: Marina
authors.initials: M
authors.lastname: Konopleva
authors.forename: Ismael J
authors.initials: IJ
authors.lastname: Samudio
authors.forename: Vivian
authors.initials: V
authors.lastname: Ruvolo
authors.forename: Michael
authors.initials: M
authors.lastname: Andreeff
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000201:enzymology / Q000502:physiology; D004357:Drug Synergism; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors*; D010879:Piperazines; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism / Q000502:physiology*; D048490:raf Kinases / Q000378:metabolism
chemical_list: D005231:Fatty Acids, Unsaturated; D005419:Flavonoids; D007093:Imidazoles; D010879:Piperazines; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C482205:nutlin 3; D051736:Proto-Oncogene Proteins c-mdm2; D048490:raf Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; C038753:leptomycin B