RESUMEN
A genome-wide screen for genetic alterations in radiation-induced thymic lymphomas generated from p53+/- and p53-/- mice showed frequent loss of heterozygosity (LOH) on chromosome 6. Fine mapping of these LOH regions revealed three non-overlapping regions, one of which was refined to a 0.2 Mb interval that contained only the gene encoding homeobox-interacting protein kinase 2 (Hipk2). More than 30% of radiation-induced tumors from both p53+/- and p53-/- mice showed heterozygous loss of one Hipk2 allele. Mice carrying a single inactive allele of Hipk2 in the germline were susceptible to induction of tumors by γ-radiation, but most tumors retained and expressed the wild-type allele, suggesting that Hipk2 is a haploinsufficient tumor suppressor gene for mouse lymphoma development. Heterozygous loss of both Hipk2 and p53 confers strong sensitization to radiation-induced lymphoma. We conclude that Hipk2 is a haploinsufficient lymphoma suppressor gene.
Asunto(s)
Proteínas Portadoras/metabolismo , Rayos gamma/efectos adversos , Linfoma/metabolismo , Neoplasias Inducidas por Radiación/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Neoplasias del Timo/metabolismo , Proteína p53 Supresora de Tumor/metabolismo , Animales , Proteínas Portadoras/genética , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/metabolismo , Transformación Celular Neoplásica/efectos de la radiación , Cromosomas de los Mamíferos , Regulación Neoplásica de la Expresión Génica , Pérdida de Heterocigocidad , Linfoma/genética , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Neoplasias Inducidas por Radiación/genética , Unión Proteica , Proteínas Serina-Treonina Quinasas/genética , Neoplasias del Timo/genética , Proteína p53 Supresora de Tumor/genéticaRESUMEN
Previous reports have provided evidence to support the view that the de novo synthesis of bradykinin (BK) B(1) receptor is involved in the induction of vascular responses in human umbilical vein (HUV). In the present study, we evaluated different pharmacological tools to further analyze this up-regulation process in HUV. Concentration-response curves to des-Arg(9)-BK, a selective BK B(1) receptor agonist, were performed after 5 h of incubation. Tumor necrosis factor-alpha potentiated BK B(1) receptor responses at 5 h without modifying the maximal response to des-Arg(9)-BK. Pyrrolidine dithiocarbamate, an inhibitor of nuclear factor-kappaB activation, produced a concentration-dependent decrease of the BK B(1) receptor sensitization. When tissues were continuously exposed to actinomycin D, a transcription inhibitor, or cycloheximide, a protein synthesis inhibitor, concentration-response curves to des-Arg(9)-BK were markedly diminished. On the other hand, transitory exposure to cycloheximide allowed the full recovery of BK B(1) receptor-sensitized responses at 5 h. Finally, continuous incubation with the N-linked glycosylation inhibitor, tunicamycin, almost completely abolished des-Arg(9)-BK-mediated responses. In summary, this sensitization process is potentiated by tumor necrosis factor-alpha and is selectively inhibited by pyrrolidine dithiocarbamate, suggesting that BK B(1) receptor up-regulation in HUV involves nuclear factor-kappaB activation. The effects of actinomycin D and tunicamycin provide evidence that the de novo synthesis of a transmembrane glycoprotein has an obligatory role in the BK B(1) up-regulation. The reversion of the cycloheximide effect on BK B(1) response indicates that the time necessary for synthesis, trafficking, and functional membrane expression of this receptor would be less than 1 h.