Background/purpose: Both the expression of Bcl-2 and the amount of vascular endothelial growth factor (VEGF) are increased in neuroblastoma cells cocultured with hepatocytes. The authors hypothesize that VEGF upregulates Bcl-2 expression by the neuroblastoma cells and protects them from apoptotic stimuli.
Methods: To determine whether VEGF will induce Bcl-2 expression in neuroblastoma cells, the cells are plated with standard media (control) or media supplemented with VEGF. After 24 hours, Bcl-2 expression is measured. To determine whether VEGF protects neuroblastoma cells from apoptosis, the cells are subjected to tumor necrosis factor alpha (TNF-alpha) or serum starvation to induce apoptosis either with or without VEGF added to the culture media. The cells are collected and apoptosis measured using the deoxynucleotidyltransferase-mediated dUTP neck end labeling (TUNEL) method.
Results: VEGF increases Bcl-2 expression by 33% over cells cultured in standard media. Serum starving the tumor cells or adding TNF-alpha significantly increases the percentage of apoptotic cells. The addition of VEGF significantly protects the neuroblastoma cells from the apoptotic effects of both serum starvation and TNF-alpha.
Conclusions: VEGF increases the expression of Bcl-2 and also abrogates TNF-alpha and serum starvation-induced apoptosis in neuroblastoma cells in vitro. VEGF may promote neuroblastoma survival not only through angiogenesis, but also by altering apoptosis and its regulating proteins.
Copyright 2002 by W.B. Saunders Company.