Isatin inhibits proliferation and induces apoptosis of SH-SY5Y neuroblastoma cells in vitro and in vivo

The purpose of this study was to investigate the anti-tumor effects of the isatin in vitro and in vivo. Human neuroblastoma cells (SH-SY5Y) were exposed to isatin at various concentrations (0, 50, 100, 200 μmol/l) for 48 h. Bcl-2 and Bax mRNA were analyzed via RT-PCR. Bcl-2, Bax, the inhibitor of caspase-activated DNase (ICAD) and cytochrome c protein were analyzed via western blot. Apoptosis, caspase-9, 3 activation and mitochondrial depolarization were assayed by flow cytometry. SH-SY5Y cells were injected into the right side of the mouse armpit. When the neoplasm was detected, the nude mice were randomly divided into four groups and received an injection of DMEM (negative control), 25 or 50 mg/kg isatin, or cyclophosphamide (positive control). The inhibitory effects of isatin on the murine xenograft were determined using a growth curve and Bcl-2 and Bax mRNA and protein were studied using RT-PCR and western blot, respectively. The results showed that apoptosis of SH-SY5Y cells was induced by isatin. Furthermore, Bcl-2 expression was decreased and the ratio of Bcl-2 to Bax was significantly decreased by isatin. The mitochondrial transmembrane potential was markedly reduced and the release of cytochrome c into the cytosol was increased after treatment with isatin. Simultaneously, caspase-9, 3 was activated, followed by degradation of ICAD, a caspase-3 substrate. Finally, tumor xenograft growth was markedly suppressed and a decrease was found in Bcl-2 and Bax expression in vivo. These results suggest that isatin can induce apoptosis and inhibit the growth of neuroblastoma cells via the mitochondrial pathway.