RESUMEN
Mutations in the BRCA1 and BRCA2 genes predispose individuals to the development of breast and ovarian cancers. As a result, biochemical functions of BRCA1 and BRCA2 proteins are being characterised in great detail. These studies have prompted the use of PARP inhibitors to treat BRCA1 and BRCA2-deficient ovarian cancers. This example of synthetic lethality represents a conceptual progress made recently in the approach to cancer treatment and is being currently tested in multiple clinical trials. Other than BRCA1 and BRCA2, many other factors might influence the survival of ovarian cancer patients. Currently, ovarian cancer remains the fifth most common cancer in the United Kingdom among women. Recent evidence suggests benefit in the modulation of the ubiquitin-proteasome system for the treatment of ovarian cancer. In this manuscript, we review the role of Cullin-Ring ubiquitin Ligases (CRLs) in the pathogenesis of ovarian cancer and their potential therapeutic exploitation. CRLs comprise a large family of proteins that, like kinases, might represent ideal candidates for targeted therapy and provide a large repertoire for the development of new anti-cancer compounds.
Asunto(s)
Proteínas Cullin/metabolismo , Neoplasias Ováricas/enzimología , Ubiquitina-Proteína Ligasas/metabolismo , Ubiquitina/metabolismo , Animales , Proteína BRCA1/genética , Proteína BRCA2/genética , Proteínas Cullin/genética , Femenino , Predisposición Genética a la Enfermedad , Humanos , Mutación , Neoplasias Ováricas/genética , Ubiquitina/genética , Ubiquitina-Proteína Ligasas/genéticaRESUMEN
Mitosis requires cyclin-dependent kinase (cdk) 1-cyclin B activity [1]. Exit from mitosis depends on the inactivation of the complex by the degradation of cyclin B [2]. Cdk2 is also active during mitosis [3, 4]. In Xenopus egg extracts, cdk2 is primarily in complex with cyclin E, which is stable [5]. At the end of mitosis, downregulation of cdk2-cyclin E activity is accompanied by inhibitory phosphorylation of cdk2 [6]. Here, we show that cdk2-cyclin E activity maintains cdk1-cyclin B during mitosis. At mitosis exit, cdk2 is inactivated prior to cdk1. The loss of cdk2 activity follows and depends upon an increase in protein kinase A (PKA) activity. Prematurely inactivating cdk2 advances the time of cyclin B degradation and cdk1 inactivation. Blocking PKA, instead, stabilizes cdk2 activity and inhibits cyclin B degradation and cdk1 inactivation. The stabilization of cdk1-cyclin B is also induced by a mutant cdk2-cyclin E complex that is resistant to inhibitory phosphorylation. P21-Cip1, which inhibits both wild-type and mutant cdk2-cyclin E, reverses mitotic arrest under either condition. Our findings indicate that the proteolysis-independent downregulation of cdk2 activity at the end of mitosis depends on PKA and is required to activate the proteolysis cascade that leads to mitosis exit.