RESUMO
BCL-2 proteins are critical for cell survival and are overexpressed in many tumors. ABT-737 is a small-molecule BH3 mimetic that exhibits single-agent activity against lymphoma and small-cell lung cancer in preclinical studies. We here report that ABT-737 effectively kills acute myeloid leukemia blast, progenitor, and stem cells without affecting normal hematopoietic cells. ABT-737 induced the disruption of the BCL-2/BAX complex and BAK-dependent but BIM-independent activation of the intrinsic apoptotic pathway. In cells with phosphorylated BCL-2 or increased MCL-1, ABT-737 was inactive. Inhibition of BCL-2 phosphorylation and reduction of MCL-1 expression restored sensitivity to ABT-737. These data suggest that ABT-737 could be a highly effective antileukemia agent when the mechanisms of resistance identified here are considered.
Assuntos
Apoptose/fisiologia , Compostos de Bifenilo , Resistencia a Medicamentos Antineoplásicos/fisiologia , Leucemia Mieloide Aguda , Nitrofenóis , Proteínas Proto-Oncogênicas c-bcl-2/antagonistas & inibidores , Sulfonamidas , Animais , Compostos de Bifenilo/metabolismo , Compostos de Bifenilo/uso terapêutico , Linhagem Celular , Dimerização , Células-Tronco Hematopoéticas/fisiologia , Humanos , Leucemia Mieloide Aguda/tratamento farmacológico , Leucemia Mieloide Aguda/metabolismo , Camundongos , Proteína de Sequência 1 de Leucemia de Células Mieloides , Proteínas de Neoplasias/metabolismo , Nitrofenóis/metabolismo , Nitrofenóis/uso terapêutico , Piperazinas/metabolismo , Piperazinas/uso terapêutico , Conformação Proteica , Estrutura Terciária de Proteína , Proteínas Proto-Oncogênicas c-bcl-2/química , Proteínas Proto-Oncogênicas c-bcl-2/genética , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Sulfonamidas/metabolismo , Sulfonamidas/uso terapêutico , Proteína Killer-Antagonista Homóloga a bcl-2/genética , Proteína Killer-Antagonista Homóloga a bcl-2/metabolismo , Proteína X Associada a bcl-2/química , Proteína X Associada a bcl-2/genética , Proteína X Associada a bcl-2/metabolismoRESUMO
BACKGROUND: Imatinib mesylate induces high rates of hematologic and cytogenetic response in patients with chronic myelogenous leukemia (CML). During therapy with imatinib, up to 45% of patients with CML reportedly experience myelosuppression > or = Grade 3, requiring interruption of therapy and/or dose reductions. The significance of myelosuppression for response to imatinib is unknown. METHODS: The authors analyzed 143 patients with late chronic-phase CML who were treated with imatinib after failing interferon. Univariate and multivariate analyses were performed to determine patient characteristics that were correlated with myelosuppression response and the association between myelosuppression and cytogenetic response. RESULTS: Neutropenia > or = Grade 3 (according to National Cancer Institute Common Toxicity Criteria) occurred in 64 patients (45%), and thrombocytopenia > or = Grade 3 occurred in 31 patients (22%). Any myelosuppression > or = Grade 3 was associated with a lower rate of major (P = 0.04) or complete (P = 0.01) cytogenetic responses. This was more pronounced with myelosuppression that lasted > 2 weeks. The major cytogenetic response rate was 58% with Grade > or = 3 myelosuppression compared with a rate of 75% without Grade > or =3 myelosuppression (P = 0.03); the complete cytogenetic response rates were 36% and 63%, respectively (P = 0.001). In a multivariate analysis, pretreatment platelet count, imatinib dose reductions, and duration of myelosuppression were associated significantly with response. CONCLUSIONS: Myelosuppression is an independent adverse factor for achieving cytogenetic response with imatinib in patients with CML. Intervention with hematopoietic growth factors in patients with CML who are treated with imatinib should be investigated.