RESUMO
The mechanism of bFGF-induced cell death in tumours of the Ewing's sarcoma family (ESFT) has been investigated. bFGF-induces phosphorylation of FGFr 1 and activation of Ras/ERK in ESFT cells that die when exposed to bFGF. Induction of cell death was associated with activation of both initiator (caspases-2, -8 and -10) and effector (caspases-3, -6 and -7) caspases. Moreover, the general caspase inhibitor Z-VAD-FMK protected cells from bFGF-induced cell death. After treatment with bFGF, a loss of mitochondrial transmembrane potential was accompanied by down-regulation of Bcl-2. However, the observed cell death was not associated with release of cytochrome c from the mitochondria. Furthermore, expression of wild-type p53 was not required for bFGF-induced cell death. These observations suggest that bFGF-induced cell death may be mediated through a cell death receptor mechanism, supported by up-regulation of the p75 neurotrophin receptor. bFGF-induced cell death was associated with up-regulation of p21 and p53, down-regulation of PCNA and cyclin A and a decrease in active pRb1, changes consistent with accumulation of cells in G1. These data demonstrate that bFGF-induced cell death is effected through a caspase-dependent and p53-independent mechanism, that may be mediated through a cell death receptor pathway.