RESUMO
Embryonic stem cells (ESCs) have adopted an accelerated cell-cycle program with shortened gap phases and precocious expression of cell-cycle regulatory proteins, including cyclins and cyclin-dependent kinases (CDKs). We examined the effect of CDK inhibition on the pathways regulating proliferation and survival of ESCs. We found that inhibiting cyclin-dependent kinase 1 (CDK1) leads to activation of the DNA damage response, nuclear p53 stabilization, activation of a subset of p53 target genes including NOXA, and negative regulation of the anti-apoptotic protein MCL1 in human and mouse ESCs, but not differentiated cells. We demonstrate that MCL1 is highly expressed in ESCs and loss of MCL1 leads to ESC death. Finally, we show that clinically relevant CDK1 inhibitors prevent formation of ESC-derived tumors and induce necrosis in established ESC-derived tumors. Our data demonstrate that ES cells are uniquely sensitive to CDK1 inhibition via a p53/NOXA/MCL1 pathway.
Assuntos
Proteína Quinase CDC2/antagonistas & inibidores , Transformação Celular Neoplásica , Células-Tronco Embrionárias/metabolismo , Proteína de Sequência 1 de Leucemia de Células Mieloides/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Transdução de Sinais/efeitos dos fármacos , Teratoma/etiologia , Proteína Supressora de Tumor p53/metabolismo , Animais , Apoptose/genética , Proteína Quinase CDC2/genética , Diferenciação Celular , Linhagem Celular , Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/metabolismo , Ciclina A/genética , Ciclina B1/genética , Ciclina B2/genética , Dano ao DNA/efeitos dos fármacos , Resistência a Medicamentos/efeitos dos fármacos , Resistência a Medicamentos/genética , Células-Tronco Embrionárias/citologia , Células-Tronco Embrionárias/efeitos dos fármacos , Células-Tronco Embrionárias/patologia , Regulação da Expressão Gênica , Técnicas de Inativação de Genes , Humanos , Camundongos , Proteína de Sequência 1 de Leucemia de Células Mieloides/genética , Fator 3 de Transcrição de Octâmero/genética , Fator 3 de Transcrição de Octâmero/metabolismo , Inibidores de Proteínas Quinases/farmacologia , Proteínas Proto-Oncogênicas c-bcl-2/genética , Interferência de RNA , Teratoma/patologia , Proteína Supressora de Tumor p53/genéticaRESUMO
A family of conserved serine/threonine kinases known as cyclin-dependent kinases (CDKs) drives orderly cell cycle progression in mammalian cells. Prior studies have suggested that CDK2 regulates S-phase entry and progression, and frequently shows increased activity in a wide spectrum of human tumors. Genetic KO/knockdown approaches, however, have suggested that lack of CDK2 protein does not prevent cellular proliferation, both during somatic development in mice as well as in human cancer cell lines. Here, we use an alternative, chemical-genetic approach to achieve specific inhibition of CDK2 kinase activity in cells. We directly compare small-molecule inhibition of CDK2 kinase activity with siRNA knockdown and show that small-molecule inhibition results in marked defects in proliferation of nontransformed cells, whereas siRNA knockdown does not, highlighting the differences between these two approaches. In addition, CDK2 inhibition drastically diminishes anchorage-independent growth of human cancer cells and cells transformed with various oncogenes. Our results establish that CDK2 activity is necessary for normal mammalian cell cycle progression and suggest that it might be a useful therapeutic target for treating cancer.
Assuntos
Transformação Celular Neoplásica , Quinase 2 Dependente de Ciclina/fisiologia , Oncogenes , Animais , Adesão Celular , Linhagem Celular Tumoral , Proliferação de Células , Neoplasias do Colo/enzimologia , Neoplasias do Colo/patologia , Quinase 2 Dependente de Ciclina/antagonistas & inibidores , Quinase 2 Dependente de Ciclina/química , Quinase 2 Dependente de Ciclina/genética , Técnicas de Silenciamento de Genes , Humanos , Camundongos , RNA Interferente PequenoRESUMO
Estrogen, progesterone, and HER2 receptor-negative triple-negative breast cancers encompass the most clinically challenging subtype for which targeted therapeutics are lacking. We find that triple-negative tumors exhibit elevated MYC expression, as well as altered expression of MYC regulatory genes, resulting in increased activity of the MYC pathway. In primary breast tumors, MYC signaling did not predict response to neoadjuvant chemotherapy but was associated with poor prognosis. We exploit the increased MYC expression found in triple-negative breast cancers by using a synthetic-lethal approach dependent on cyclin-dependent kinase (CDK) inhibition. CDK inhibition effectively induced tumor regression in triple-negative tumor xenografts. The proapoptotic BCL-2 family member BIM is up-regulated after CDK inhibition and contributes to this synthetic-lethal mechanism. These results indicate that aggressive breast tumors with elevated MYC are uniquely sensitive to CDK inhibitors.
