RESUMO
Although oncogenic Ras commonly contributes to the development of cancer, in normal primary cells it induces cell cycle arrest rather than transformation. Here we analyze the additional genetic changes required for Ras to promote cell cycle progression rather than arrest. We show that loss of p53 is sufficient for oncogenic Ras to stimulate proliferation in the absence of extrinsic mitogens in attached cells. However, surprisingly, we find that p53 loss is not sufficient for Ras to overcome anchorage dependence or contact inhibition. In contrast, expression of simian virus 40 (SV40) large T antigen (LT) allows Ras to overcome these additional cell cycle controls. Mutational analysis of SV40 LT shows that this action of SV40 LT depends on its ability to inactivate the retinoblastoma (Rb) family of proteins, in concert with the loss of p53. Importantly, we show that inactivation of the Rb family of proteins can be mimicked by loss of the cyclin-dependent kinase inhibitor p16(INK4A). p16(INK4A) is commonly lost in human tumors, but its contribution to the transformed phenotype is unknown. We demonstrate here a role for p16(INK4A) in the loss of cell cycle controls required for tumorigenesis and show how accumulating genetic changes cooperate and contribute to the transformed phenotype.
Assuntos
Transformação Celular Neoplásica/genética , Inibidor p16 de Quinase Dependente de Ciclina/metabolismo , Proteína do Retinoblastoma/genética , Proteínas ras/metabolismo , Animais , Antígenos Virais de Tumores/biossíntese , Antígenos Virais de Tumores/genética , Adesão Celular/fisiologia , Divisão Celular/genética , Transformação Celular Neoplásica/metabolismo , Células Cultivadas , Inibição de Contato/genética , Inibidor p16 de Quinase Dependente de Ciclina/deficiência , Inibidor p16 de Quinase Dependente de Ciclina/genética , Vetores Genéticos , Proteínas de Fluorescência Verde , Proteínas Luminescentes/genética , Ratos , Proteína do Retinoblastoma/antagonistas & inibidores , Células de Schwann/citologia , Células de Schwann/metabolismo , Transfecção , Proteína Supressora de Tumor p53/deficiência , Proteína Supressora de Tumor p53/genética , Proteínas ras/genéticaRESUMO
Fatty acid binding protein 6 (FABP6) is a potential drug discovery target, which, if inhibited, may have a therapeutic benefit for the treatment of diabetes. Currently, there are no published inhibitors of FABP6, and with the target believed to be amenable to fragment-based drug discovery, a structurally enabled program was initiated. This program successfully identified fragment hits using the surface plasmon resonance (SPR) platform. Several hits were validated with SAR and were found to be displaced by the natural ligand taurocholate. We report the first crystal structure of human FABP6 in the unbound form, in complex with cholate, and with one of the key fragments.