The prevention of the staurosporine‐induced apoptosis by Bcl‐XL, but not by Bcl‐2 or caspase inhibitors, allows the extensive differentiation of human neuroblastoma cells

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Abstract
Staurosporine is one of the best apoptotic inducers in different cell types including neuroblastomas. In this study we have compared the efficiency and final outcome of three different anti-apoptotic strategies in staurosporine-treated SH-SY5Y human neuroblastoma cells. At staurosporine concentrations up to 500 nm, z-VAD.fmk a broad-spectrum, noncompetitive inhibitor of caspases, reduced apoptosis in SH-SY5Y cells. At higher concentrations, z-VAD.fmk continued to inhibit caspases and the apoptotic phenotype but not cell death which seems to result from oxidative damage. Stable over-expression of Bcl-2 in SH-SY5Y protected cells from death at doses of staurosporine up to 1 microm. At higher doses, cytochrome c release from mitochondria occurred, caspases were activated and cells died by apoptosis. Therefore, we conclude that Bcl-2 increased the threshold for apoptotic cell death commitment. Over-expression of Bcl-X(L) was far more effective than Bcl-2. Bcl-X(L) transfected cells showed a remarkable resistance staurosporine-induced cytochrome c release and associated apoptotic changes and survived for up to 15 days in 1 microm staurosporine. In these conditions, SH-SY5Y displayed a remarkable phenotype of neuronal differentiation as assessed by neurite outgrowth and expression of neurofilament, Tau and MAP-2 neuronal specific proteins.