RESUMO
Strategies to induce p53 activation in wtp53-retaining tumors carry high potential in cancer therapy. Nutlin, a potent highly selective MDM2 inhibitor, induces non-genotoxic p53 activation. Although Nutlin shows promise in promoting cell death in hematopoietic malignancies, a major roadblock is that most solid cancers do not undergo apoptosis but merely reversible growth arrest. p53 inhibition by unopposed MDMX is one major cause for apoptosis resistance to Nutlin. The Hsp90 chaperone is ubiquitously activated in cancer cells and supports oncogenic survival pathways, many of which antagonize p53. The Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17AAG) is known to induce p53-dependent apoptosis. We show here that in multiple difficult-to-kill solid tumor cells 17AAG modulates several critical components that synergize with Nutlin-activated p53 signaling to convert Nutlin's transient cytostatic response into a cytotoxic killing response in vitro and in xenografts. Combined with Nutlin, 17AAG destabilizes MDMX, reduces MDM2, induces PUMA and inhibits oncogenic survival pathways, such as PI3K/AKT, which counteract p53 signaling at multiple levels. Mechanistically, 17AAG interferes with the repressive MDMX-p53 axis by inducing robust MDMX degradation, thereby markedly increasing p53 transcription compared with Nutlin alone. To our knowledge Nutlin+17AAG represents the first effective pharmacologic knockdown of MDMX. Our study identifies 17AAG as a promising synthetic lethal partner for a more efficient Nutlin-based therapy.
Assuntos
Apoptose/efeitos dos fármacos , Benzoquinonas/farmacologia , Proteínas de Choque Térmico HSP90/antagonistas & inibidores , Imidazóis/farmacologia , Lactamas Macrocíclicas/farmacologia , Proteínas Nucleares/antagonistas & inibidores , Piperazinas/farmacologia , Proteínas Proto-Oncogênicas/antagonistas & inibidores , Proteína Supressora de Tumor p53/antagonistas & inibidores , Animais , Proteínas Reguladoras de Apoptose/genética , Proteínas Reguladoras de Apoptose/metabolismo , Caspases/metabolismo , Proteínas de Ciclo Celular , Linhagem Celular Tumoral , Inibidor de Quinase Dependente de Ciclina p21/genética , Inibidor de Quinase Dependente de Ciclina p21/metabolismo , Sinergismo Farmacológico , Ativação Enzimática , Humanos , Masculino , Camundongos , Camundongos Nus , Transplante de Neoplasias , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Ligação Proteica , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas c-mdm2/genética , Proteínas Proto-Oncogênicas c-mdm2/metabolismo , Transplante Heterólogo , Carga Tumoral/efeitos dos fármacos , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismoRESUMO
The p53 family member p73 is essential for brain development, but its precise role and scope remain unclear. Global p73 deficiency determines an overt and highly penetrant brain phenotype marked by cortical hypoplasia with ensuing hydrocephalus and hippocampal dysgenesis. The ΔNp73 isoform is known to function as a prosurvival factor of mature postmitotic neurons. In this study, we define a novel essential role of p73 in the regulation of the neural stem cell compartment. In both embryonic and adult neurogenesis, p73 has a critical role in maintaining an adequate neurogenic pool by promoting self-renewal and proliferation and inhibiting premature senescence of neural stem and early progenitor cells. Thus, products of the p73 gene locus are essential maintenance factors in the central nervous system, whose broad action stretches across the entire differentiation arch from stem cells to mature postmitotic neurons.
