Estudios científicos
Estrogenic effects of resveratrol in breast cancer cells expressing mutant and wild-type estrogen receptors: role of AF-1 and AF-2.
Abstract:
Resveratrol, a hydroxystilbene found in grapes and wine, has previously been shown to be a non-flavonoid phytoestrogen, and to act as an estrogen receptor (ER) superagonist in MCF-7 cells transiently transfected with estrogen-responsive reporter constructs. Several additional hydroxystilbenes, including diethylstilbestrol (DES) and piceatannol, were tested, and all showed ER agonism or partial agonism, but superagonism was specific to resveratrol. Moreover, superagonism was observed in cells carrying a stably integrated reporter gene, indicating that this phenomenon is not a result of transient transfection. To examine the role of the transcriptional activation function (AF) domains of ERalpha in resveratrol agonism, we compared the effects of resveratrol and estradiol (E2) on expression of exogenous reporter genes and an endogenous estrogen-regulated gene (TGFalpha) in MDA-MB-231 cells stably transfected with wild-type (wt) ERalpha or mutants with deleted or mutated AF domains. In reporter gene assays, cells expressing wtERalpha showed a superagonistic response to resveratrol. Deletion of AF-1 or mutation of AF-2 attenuated the effect of resveratrol disproportionately compared to that of E2, while deletion of AF-2 abrogated the response to both ligands. In TGFalpha expression assays, resveratrol acted as a full agonist in cells expressing wtERalpha. Deletion of AF-1 attenuated stimulation by E2 more severely than that by resveratrol, as did deletion of AF-2. In contrast, mutation of AF-2 left both ligands with a limited ability to induced TGFalpha expression. In summary, the effect of modifying or deleting AF domains depends strongly on the ligand and the target gene.
Comentarios divulgativos:
El resveratrol, un hidroxiestilbeno que se encuentra en las uvas y el vino, actua como un superagonista del receptor de estrógeno (ER) en células MCF-7 transfectadas transitoriamente con el reporter de estrógeno. Varios estilbenos adicionales, como dietilestilbestrol (DES) y el piceatannol, fueron probados, y todos mostraron ER agonista o agonista parcial, pero el superagonista era específico para el resveratrol. Para examinar el papel de la función de activación de la transcripción (AF) en los dominios de ERalpha resveratrol, se compararon los efectos del resveratrol y el estradiol (E2) en la expresión de genes exógenos reporteros y un gen endógeno de estrógeno-regulados (TGFalpha) en células MDA-MB -231 establemente transfectadas con el tipo salvaje (wt) ERalpha o mutantes donde han sido eliminados o mutados los dominios AF. En los ensayos de gen indicador, las células que expresan wtERalpha mostraron una respuesta superagonistica al resveratrol. En ensayos de expresión TGFalpha, el resveratrol actúa como un agonista total en células que expresan wtERalpha.. En cambio, la mutación de la FA-2 dejó a ambos ligandos con una capacidad limitada para la expresión inducida por TGFalpha. En resumen, el efecto de modificar o eliminar dominios AF depende en gran medida del ligando y del gen diana.
