RESUMEN
The epidermal growth factor receptor (EGFR) is commonly upregulated in multiple cancer types, including breast cancer. In the present study, evidence is provided in support of the premise that upregulation of the EGFR/MEK1/MAPK1/2 signaling axis during antiestrogen treatment facilitates the escape of breast cancer cells from BimELdependent apoptosis, conferring resistance to therapy. This conclusion is based on the findings that ectopic BimEL cDNA overexpression and confocal imaging studies confirm the proapoptotic role of BimEL in ERα expressing breast cancer cells and that upregulated EGFR/MEK1/MAPK1/2 signaling blocks BimEL proapoptotic action in an antiestrogenresistant breast cancer cell model. In addition, the present study identified a prosurvival role for autophagy in antiestrogen resistance while EGFR inhibitor studies demonstrated that a significant percentage of antiestrogenresistant breast cancer cells survive EGFR targeting by prosurvival autophagy. These preclinical studies establish the possibility that targeting both the MEK1/MAPK1/2 signaling axis and prosurvival autophagy may be required to eradicate breast cancer cell survival and prevent the development of antiestrogen resistance following hormone treatments. The present study uniquely identified EGFR upregulation as one of the mechanisms breast cancer cells utilize to evade the cytotoxic effects of antiestrogens mediated through BimELdependent apoptosis.
Asunto(s)
Apoptosis , Neoplasias de la Mama , Resistencia a Antineoplásicos , Moduladores de los Receptores de Estrógeno , Femenino , Humanos , Apoptosis/efectos de los fármacos , Proteína 11 Similar a Bcl2/efectos de los fármacos , Proteína 11 Similar a Bcl2/metabolismo , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/genética , Neoplasias de la Mama/metabolismo , Línea Celular Tumoral , Resistencia a Antineoplásicos/fisiología , Receptores ErbB/genética , Receptores ErbB/metabolismo , Moduladores de los Receptores de Estrógeno/farmacología , Moduladores de los Receptores de Estrógeno/uso terapéutico , Proteína Quinasa 1 Activada por Mitógenos/genética , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Regulación hacia Arriba , Transducción de SeñalRESUMEN
The disruption of retinal pigment epithelial (RPE) function and the degeneration of photoreceptors are cardinal features of age related macular degeneration (AMD); however there are still gaps in our understanding of underlying biological processes. Excess homocysteine (Hcy) has been reported to be elevated in plasma of patients with AMD. This study aimed to evaluate the direct effect of hyperhomocysteinemia (HHcy) on structure and function of RPE. Initial studies in a mouse model of HHcy, in which cystathionine-ß-synthase (cbs) was deficient, revealed abnormal RPE cell morphology with features similar to that of AMD upon optical coherence tomography (OCT), fluorescein angiography (FA), histological, and electron microscopic examinations. These features include atrophy, vacuolization, hypopigmentation, thickened basal laminar membrane, hyporeflective lucency, choroidal neovascularization (CNV), and disturbed RPE-photoreceptor relationship. Furthermore, intravitreal injection of Hcy per se in normal wild type (WT) mice resulted in diffuse hyper-fluorescence, albumin leakage, and CNV in the area of RPE. In vitro experiments on ARPE-19 showed that Hcy dose-dependently reduced tight junction protein expression, increased FITC dextran leakage, decreased transcellular electrical resistance, and impaired phagocytic activity. Collectively, our results demonstrated unreported effects of excess Hcy levels on RPE structure and function that lead to the development of AMD-like features.