title: Imatinib mesylate induces cisplatin hypersensitivity in Bcr-Abl+ cells by differential modulation of p53 transcriptional and proapoptotic activity.
abstract: Imatinib is highly effective in inducing remission in chronic myelogenous leukemia (CML). However, complete eradication of the malignant clone by imatinib is rare. We investigated the efficacy of combining imatinib with cisplatin. Inhibition of Bcr-Abl by imatinib induced a hypersensitive phenotype both in Bcr-Abl(+) cell lines and in CD34(+) cells from CML patients. Importantly, cisplatin sensitivity of leukemic cells harboring an inactive Bcr-Abl greatly exceeded that of Bcr-Abl(-) parental cells. The cisplatin response of Bcr-Abl(+) cells treated with imatinib was characterized by an impaired G(2)-M arrest and by rapid induction of mitochondrial cell death after the first passage through G(2). Imatinib abrogated ATM activation on cisplatin selectively in Bcr-Abl(+) cells. As a consequence, phosphorylation of p53 on Ser(15) and its activity as a transcription factor was significantly diminished. Furthermore, p53 accumulated predominantly in the cytoplasm in Bcr-Abl(+) cells treated with imatinib and cisplatin. Silencing of p53 significantly reduced sensitivity to cisplatin in imatinib-treated Bcr-Abl(+) cells, indicating that p53 retains its proapoptotic activity. Simultaneous downregulation of Bcl-x(L) was an additional requirement for cisplatin hypersensitivity, as p53-dependent cell death could be antagonized by exogenous Bcl-x(L). We conclude that imatinib sensitizes Bcr-Abl(+) cells to cisplatin by simultaneous inhibition of p53 transactivation, induction of p53 accumulation predominantly in the cytoplasm, and reduction of Bcl-x(L).
authors.affiliation: Dr Margarete-Fischer-Bosch Institute of Clinical Pharmacology and University of Tuebingen, Stuttgart, Germany.
authors.forename: Ioanna
authors.initials: I
authors.lastname: Skorta
authors.forename: Moshe
authors.initials: M
authors.lastname: Oren
authors.forename: Christiane
authors.initials: C
authors.lastname: Markwardt
authors.forename: Matthias
authors.initials: M
authors.lastname: Gutekunst
authors.forename: Walter E
authors.initials: WE
authors.lastname: Aulitzky
authors.forename: Heiko
authors.initials: H
authors.lastname: van der Kuip
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D064007:Ataxia Telangiectasia Mutated Proteins; D001549:Benzamides; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D002945:Cisplatin / Q000008:administration & dosage / Q000494:pharmacology*; D004249:DNA Damage / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D016044:Fusion Proteins, bcr-abl / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D000068877:Imatinib Mesylate; D020014:K562 Cells; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051379:Mice; D022423:Myeloid Cells / Q000187:drug effects; D010879:Piperazines / Q000008:administration & dosage / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011743:Pyrimidines / Q000008:administration & dosage / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D051020:bcl-X Protein / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: C494811:BCL2L1 protein, human; D001549:Benzamides; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D010879:Piperazines; D011743:Pyrimidines; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D051020:bcl-X Protein; D000068877:Imatinib Mesylate; D016044:Fusion Proteins, bcr-abl; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases; D002945:Cisplatin