RESUMO
Cdk7, the CDK-activating kinase and transcription factor IIH component, is a target of inhibitors that kill cancer cells by exploiting tumor-specific transcriptional dependencies. However, whereas selective inhibition of analog-sensitive (AS) Cdk7 in colon cancer-derived cells arrests division and disrupts transcription, it does not by itself trigger apoptosis efficiently. Here, we show that p53 activation by 5-fluorouracil or nutlin-3 synergizes with a reversible Cdk7as inhibitor to induce cell death. Synthetic lethality was recapitulated with covalent inhibitors of wild-type Cdk7, THZ1, or the more selective YKL-1-116. The effects were allele specific; a CDK7as mutation conferred both sensitivity to bulky adenine analogs and resistance to covalent inhibitors. Non-transformed colon epithelial cells were resistant to these combinations, as were cancer-derived cells with p53-inactivating mutations. Apoptosis was dependent on death receptor DR5, a p53 transcriptional target whose expression was refractory to Cdk7 inhibition. Therefore, p53 activation induces transcriptional dependency to sensitize cancer cells to Cdk7 inhibition.
Assuntos
Antineoplásicos/farmacologia , Quinases Ciclina-Dependentes/antagonistas & inibidores , Fenilenodiaminas/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Pirimidinas/farmacologia , Proteína Supressora de Tumor p53/metabolismo , Apoptose , Quinases Ciclina-Dependentes/genética , Quinases Ciclina-Dependentes/metabolismo , Resistencia a Medicamentos Antineoplásicos , Fluoruracila/farmacologia , Regulação Neoplásica da Expressão Gênica , Células HCT116 , Humanos , Imidazóis/farmacologia , Piperazinas/farmacologia , Ativação Transcricional , Proteína Supressora de Tumor p53/genética , Quinase Ativadora de Quinase Dependente de CiclinaRESUMO
Eukaryotic cell division is controlled by cyclin-dependent kinases (CDKs), which require phosphorylation by a CDK-activating kinase (CAK) for full activity. Chemical genetics uncovered requirements for the metazoan CAK Cdk7 in determining cyclin specificity and activation order of Cdk2 and Cdk1 during S and G2 phases. It was unknown if Cdk7 also activates Cdk4 and Cdk6 to promote passage of the restriction (R) point, when continued cell-cycle progression becomes mitogen independent, or if CDK-activating phosphorylation regulates G1 progression. Here we show that Cdk7 is a Cdk4- and Cdk6-activating kinase in human cells, required to maintain activity, not just to establish the active state, as is the case for Cdk1 and Cdk2. Activating phosphorylation of Cdk7 rises concurrently with that of Cdk4 as cells exit quiescence and accelerates Cdk4 activation in vitro. Therefore, mitogen signaling drives a CDK-activation cascade during G1 progression, and CAK might be rate-limiting for R point passage.
