title: Pim kinases phosphorylate Chk1 and regulate its functions in acute myeloid leukemia.
abstract: Phosphorylation by Akt on Ser 280 was reported to induce cytoplasmic retention and inactivation of CHK1 with consequent genetic instability in PTEN-/- cells. In acute myeloid leukemia cells carrying the FLT3-internal tandem duplication (ITD) mutation, we observed high rates of FLT3-ITD-dependent CHK1 Ser 280 phosphorylation. Pharmacological inhibition and RNA interference identified Pim1/2, not Akt, as effectors of this phosphorylation. Pim1 catalyzed Ser 280 phosphorylation in vitro and ectopic expression of Pim1/2-induced CHK1 phosphorylation. Ser 280 phosphorylation did not modify CHK1 localization, but facilitated its cell cycle and resistance functions in leukemic cells. FLT3, PIM or CHK1 inhibitors synergized with DNA-damaging agents to induce apoptosis, allowing cells to bypass the etoposide-induced G2/M arrest. Consistently, etoposide-induced CHK1-dependent phosphorylations of CDC25C on Ser 216 and histone H3 on Thr11 were decreased upon FLT3 inhibition. Accordingly, ectopic expression of CHK1 improved the resistance of FLT3-ITD cells and maintained histone H3 phosphorylation in response to DNA damage, whereas expression of unphosphorylated Ser 280Ala mutant did not. Finally, FLT3- and Pim-dependent phosphorylation of CHK1 on Ser 280 was confirmed in primary blasts from patients. These results identify a new pathway involved in the resistance of FLT3-ITD leukemic cells to genotoxic agents, and they constitute the first report of CHK1 Ser 280 regulation in myeloid malignancies.
authors.affiliation: Cancer Research Center of Toulouse, Inserm Unité Mixte de Recherche 1037, CNRS Equipe de Recherche labellisée 5294, Université de Toulouse, Centre Hospitalier Universitaire Purpan, Toulouse, France.
authors.forename: L L
authors.initials: LL
authors.lastname: Yuan
authors.affiliation: Institut Cochin, Université Paris Descartes, CNRS UMR 8104, INSERM U 1016, Paris, France.
authors.forename: A S
authors.initials: AS
authors.lastname: Green
authors.affiliation: 1] Cancer Research Center of Toulouse, Inserm Unité Mixte de Recherche 1037, CNRS Equipe de Recherche labellisée 5294, Université de Toulouse, Centre Hospitalier Universitaire Purpan, Toulouse, France [2] Service d'Hématologie, Centre Hospitalier Universitaire Purpan, Toulouse, France.
authors.forename: S
authors.initials: S
authors.lastname: Bertoli
authors.affiliation: Cancer Research Center of Toulouse, Inserm Unité Mixte de Recherche 1037, CNRS Equipe de Recherche labellisée 5294, Université de Toulouse, Centre Hospitalier Universitaire Purpan, Toulouse, France.
authors.forename: F
authors.initials: F
authors.lastname: Grimal
authors.affiliation: 1] Cancer Research Center of Toulouse, Inserm Unité Mixte de Recherche 1037, CNRS Equipe de Recherche labellisée 5294, Université de Toulouse, Centre Hospitalier Universitaire Purpan, Toulouse, France [2] Laboratoire d'Hématologie, Centre Hospitalier Universitaire Purpan, Toulouse, France.
authors.forename: V
authors.initials: V
authors.lastname: Mansat-De Mas
authors.affiliation: Cancer Research Center of Toulouse, Inserm Unité Mixte de Recherche 1037, CNRS Equipe de Recherche labellisée 5294, Université de Toulouse, Centre Hospitalier Universitaire Purpan, Toulouse, France.
authors.forename: C
authors.initials: C
authors.lastname: Dozier
authors.affiliation: Institut Cochin, Université Paris Descartes, CNRS UMR 8104, INSERM U 1016, Paris, France.
authors.forename: J
authors.initials: J
authors.lastname: Tamburini
authors.affiliation: 1] Cancer Research Center of Toulouse, Inserm Unité Mixte de Recherche 1037, CNRS Equipe de Recherche labellisée 5294, Université de Toulouse, Centre Hospitalier Universitaire Purpan, Toulouse, France [2] Service d'Hématologie, Centre Hospitalier Universitaire Purpan, Toulouse, France.
authors.forename: C
authors.initials: C
authors.lastname: Récher
authors.affiliation: Cancer Research Center of Toulouse, Inserm Unité Mixte de Recherche 1037, CNRS Equipe de Recherche labellisée 5294, Université de Toulouse, Centre Hospitalier Universitaire Purpan, Toulouse, France.
authors.forename: C
authors.initials: C
authors.lastname: Didier
authors.affiliation: Cancer Research Center of Toulouse, Inserm Unité Mixte de Recherche 1037, CNRS Equipe de Recherche labellisée 5294, Université de Toulouse, Centre Hospitalier Universitaire Purpan, Toulouse, France.
authors.forename: S
authors.initials: S
authors.lastname: Manenti
mesh_terms: D045744:Cell Line, Tumor; D000071877:Checkpoint Kinase 1; D020440:Gene Duplication; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D015470:Leukemia, Myeloid, Acute / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D021381:Protein Transport; D051573:Proto-Oncogene Proteins c-pim-1 / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction; D051941:fms-Like Tyrosine Kinase 3 / Q000378:metabolism
chemical_list: D012694:Serine; D011494:Protein Kinases; D051941:fms-Like Tyrosine Kinase 3; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; D051573:Proto-Oncogene Proteins c-pim-1; C406031:proto-oncogene proteins pim