RESUMEN
Insulin-like growth factor-1 (IGF-1) is known to promote proliferation in many cell types including c-kit(pos) cardiac stem cells (CSCs). Downstream signaling pathways of IGF-1 induced CSC proliferation have not been investigated. An important downstream target of IGF-1/Akt-1 signaling is FoxO3a, a key negative regulator of cell-cycle progression. We studied the effect of IGF-1 on proliferation of c-kit(pos) murine CSCs and found that IGF-1-mediated cell proliferation is associated with FoxO3a phosphorylation and inactivation of its transcriptional activity. PI3 inhibitors LY294002 and Wortmannin abolished the effect of IGF-1 on FoxO3a phosphorylation indicating that FoxO3a phosphorylation is mediated by PI3/Akt-1 pathway. In cells with FoxO3a translocation to the cytoplasm, there is decreased expression of cell-cycle inhibitors such as p27(kip1) and p57(kip2) and increased expression of CyclinD1. Our study provides evidence that IGF-1 induced CSC proliferation could be the result of FoxO3a inactivation and its downstream effect on cell-cycle regulators.
Asunto(s)
Factores de Transcripción Forkhead/metabolismo , Factor I del Crecimiento Similar a la Insulina/farmacología , Miocardio/citología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Células Madre/metabolismo , Transporte Activo de Núcleo Celular , Androstadienos/farmacología , Animales , Ciclo Celular , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Cromonas/farmacología , Ciclina D1/biosíntesis , Inhibidor p27 de las Quinasas Dependientes de la Ciclina/biosíntesis , Inhibidor p57 de las Quinasas Dependientes de la Ciclina/biosíntesis , Proteína Forkhead Box O3 , Factores de Transcripción Forkhead/biosíntesis , Factores de Transcripción Forkhead/genética , Ratones , Ratones Endogámicos BALB C , Morfolinas/farmacología , Fosfatidilinositol 3-Quinasas/metabolismo , Inhibidores de las Quinasa Fosfoinosítidos-3 , Fosforilación , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Proto-Oncogénicas c-kit/biosíntesis , Transducción de Señal/efectos de los fármacos , Células Madre/citología , WortmaninaRESUMEN
Chemotherapy is one of the common treatment modalities for cancer. Some of the antineoplastic drugs have, however, been found to be toxic for vascular endothelium, resulting in complications such as endothelial dysfunction, thromboembolism, heart failure, and cardiomyopathy. In this study, we investigated the cytotoxic effect of widely used antitumor agents doxorubicin, camptothecin, and thapsigargin on primary and immortalized porcine endocardial endothelial cells and compared with the effects of these agents on human umbilical vein endothelial cells, human aortic endothelial cells, and EA.hy926 cells. Our study revealed that endocardial endothelial cells are relatively resistant to apoptosis induced by these drugs. Interestingly, our study indicates that response to antitumor agents greatly differs depending on the site of origin of endothelial cells. Doxorubicin, camptothecin, and thapsigargin induce mitochondrial-dependent cell death following loss of mitochondrial membrane potential (MMP) in vascular endothelial cells, with subsequent increase in sub-G0 population. In endocardial endothelial cells, there was no MMP loss; and only cell cycle arrest either at G1 or S phases was observed when the cells were treated with doxorubicin, camptothecin, and thapsigargin.