RESUMO
Although the majority of patients with acute myeloid leukemia (AML) initially respond to chemotherapy, many of them subsequently relapse, and the mechanistic basis for AML persistence following chemotherapy has not been determined. Recurrent somatic mutations in DNA methyltransferase 3A (DNMT3A), most frequently at arginine 882 (DNMT3AR882), have been observed in AML and in individuals with clonal hematopoiesis in the absence of leukemic transformation. Patients with DNMT3AR882 AML have an inferior outcome when treated with standard-dose daunorubicin-based induction chemotherapy, suggesting that DNMT3AR882 cells persist and drive relapse. We found that Dnmt3a mutations induced hematopoietic stem cell expansion, cooperated with mutations in the FMS-like tyrosine kinase 3 gene (Flt3ITD) and the nucleophosmin gene (Npm1c) to induce AML in vivo, and promoted resistance to anthracycline chemotherapy. In patients with AML, the presence of DNMT3AR882 mutations predicts minimal residual disease, underscoring their role in AML chemoresistance. DNMT3AR882 cells showed impaired nucleosome eviction and chromatin remodeling in response to anthracycline treatment, which resulted from attenuated recruitment of histone chaperone SPT-16 following anthracycline exposure. This defect led to an inability to sense and repair DNA torsional stress, which resulted in increased mutagenesis. Our findings identify a crucial role for DNMT3AR882 mutations in driving AML chemoresistance and highlight the importance of chromatin remodeling in response to cytotoxic chemotherapy.
Assuntos
Antraciclinas/uso terapêutico , Montagem e Desmontagem da Cromatina/genética , DNA (Citosina-5-)-Metiltransferases/genética , Resistencia a Medicamentos Antineoplásicos/genética , Leucemia Mieloide Aguda/genética , Animais , Antineoplásicos/uso terapêutico , Linhagem Celular Tumoral , Proliferação de Células/genética , Sobrevivência Celular , DNA Metiltransferase 3A , Daunorrubicina/uso terapêutico , Células-Tronco Hematopoéticas , Humanos , Immunoblotting , Imunoprecipitação , Leucemia Mieloide Aguda/tratamento farmacológico , Espectrometria de Massas , Camundongos , Mutação , Proteínas Nucleares/genética , Nucleofosmina , Nucleossomos/metabolismo , Tirosina Quinase 3 Semelhante a fms/genéticaRESUMO
The identification of somatic activating mutations in JAK2 (refs 14) and in the thrombopoietin receptor gene (MPL) in most patients with myeloproliferative neoplasm (MPN) led to the clinical development of JAK2 kinase inhibitors. JAK2 inhibitor therapy improves MPN-associated splenomegaly and systemic symptoms but does not significantly decrease or eliminate the MPN clone in most patients with MPN. We therefore sought to characterize mechanisms by which MPN cells persist despite chronic inhibition of JAK2. Here we show that JAK2 inhibitor persistence is associated with reactivation of JAKSTAT signalling and with heterodimerization between activated JAK2 and JAK1 or TYK2, consistent with activation of JAK2 in trans by other JAK kinases. Further, this phenomenon is reversible: JAK2 inhibitor withdrawal is associated with resensitization to JAK2 kinase inhibitors and with reversible changes in JAK2 expression. We saw increased JAK2 heterodimerization and sustained JAK2 activation in cell lines, in murine models and in patients treated with JAK2 inhibitors. RNA interference and pharmacological studies show that JAK2-inhibitor-persistent cells remain dependent on JAK2 protein expression. Consequently, therapies that result in JAK2 degradation retain efficacy in persistent cells and may provide additional benefit to patients with JAK2-dependent malignancies treated with JAK2 inhibitors.
