VEGF-Mediated Survivin Expression in Neuroblastoma Cells

Abstract

Vascular endothelial growth factor (VEGF) up-regulates a number of cellular survival signals in endothelial cells. We hypothesize that VEGF will up-regulate survivin, a member of the IAP family of anti-apoptotic proteins, via the PI3K/Akt cell signaling pathway in human neuroblastoma cells. IMR-32 human neuroblastoma cells are cultured with VEGF at varying times and in escalating doses. A specific inhibitor of PI3-kinase, LY294002, is used to block Akt phosphorylation. Immunoblot is used to measure protein expression, and Hoechst staining is used to detect apoptosis. Stimulation of IMR-32 neuroblastoma cells with VEGF results in an increase in survivin protein expression in both a dose- and a time-dependent fashion. Akt phosphorylation is also increased after stimulation with exogenous VEGF. Blockade of Akt phosphorylation with LY294002 abrogates the effects of VEGF upon survivin and phosphorylated Akt protein expression. VEGF has been shown to up-regulate a number of survival signals in endothelial cells. We have found that exposure of human neuroblastoma cells to exogenous VEGF results in an increased expression of survivin protein and phosphorylated Akt, and inhibition of PI3-kinase abrogates those effects. It appears that VEGF is important for promotion of neuroblastoma cellular survival through the up-regulation of survival proteins, and not only through its angiogenic properties.