e the most frequently detected form. The p65 subunit may be regulated by ubiquitination, prolyl-isomerization, monomethylation and phosphorylation. Phosphorylation of p65 at Ser536 is produced in response to a variety of proinflammatory stimuli. Phosphorylation of p65 at Ser536 has been shown to favor binding of TATA-binding associated factor II31, a component of TFIID, thus enhancing transcription of NFkB target genes. Our results show that AAP not only induced p65 subunit translocation to the nucleus in a time-dependent manner, but also induced p65 activation by promoting p65 phosphorylation at Ser536. This result suggests that NFkB activation may play a central role in AAP-induced neuroblastoma cell death. Along these lines, inhibition of NFkB active complex nuclear translocation by the cell-permeable peptide SN-50 significantly prevented AAP-induced neuroblastoma cell death. The molecular mechanism involved in p65 translocation appears to be related to AAPinduced ROS production because MnTBAP, at a concentration that completely blocked ROS production, prevented p65 translocation to the nucleus to the same extent as SN50. However, the role of NFkB in apoptosis is complex. Both apoptosis suppression and induction have been reported. Thus, many atypical inducers of NFkB such as UV radiation, H2O2 and some MLN1117 anticancer drugs have been associated with the proapoptotic function of NFkB. Moreover, NFkB activation has been recently implicated in the MPP+-induction of neuroblastoma apoptotic cell death. Under our experimental conditions, NFkB nuclear translocation was found to induce apoptosis, probably through IL-1b production. Various sources of experimental data support this hypothesis: IL-1b production increased after p65 activation, SN-50 reduced IL-1b to basal levels in AAP-treated cells and neuroblastoma treatment with similar amounts of IL-1b as those produced by AAP treatment, slightly but significantly reduced neuroblastoma viability through caspase 3 activation. In addition, we found that AAP increased caspase-1 activity, the unique caspase that processes pro-IL-1b into mature IL-1b, in neuroblastoma cells. We have not yet elucidated the mechanism by which AAP induces caspase1 activation. However, considering that mutant SOD1 promotes apoptosis in oxidatively stressed neuroblastoma N2a cells by activating caspase-1 and increasing mature IL-1b secretion, we postulate that AAP-induced ROS production may be responsible for caspase-1 activation. Thus, our results clearly show that AAP-induced ROS generation, NFkB activation and subsequent IL-1b production play a central role in activating the intrinsic apoptotic pathway in neuroblastoma cells. Accordingly, co-treatment of SH-SY5Y with both MnTBAP and the SN50 peptide that block NFkB translocation to the nucleus also prevented IL-1b production, Bax translocation to the mitochondria, and cytochrome c release to the cytosol from the mitochondria. However, it has been reported that the anticancer compound betulinic acid is able to induce NFkB translocation to the nucleus in SH-EP and SH-SY5Y cells. However, unlike in our study, they found that inhibition of NFkB had 
no impact on Bet A-induced apoptosis in the SH-SY5Y cell line. A possible explanation for this discrepancy is that while it has been reported that Bet A activates both caspase-8 and caspase-3 in different tumor cells no Bet A-mediated activation of caspase-1 has been described. Thus, we postulate that the combination of p65 acti
