No abstract

Glioblastomas, the most common primary brain cancers, respond poorly to current treatment modalities and carry a dismal prognosis. In this study, we demonstrated that the transcription factor nuclear factor (NF)-B is constitutively activated in glioblastoma surgical samples, primary cultures, and cell lines and promotes their growth and survival. Sulfasalazine, an anti-inflammatory drug that specifically inhibits the activation of NF-B, blocked the cell cycle and induced apoptosis in several glioblastoma cell lines and primary cultures, as did gene therapy with a vector encoding a super-repressor of NF-B. In vivo, sulfasalazine also significantly inhibited the growth of experimental human glioblastomas in nude mice brains. Given the documented safety of sulfasalazine in humans, these results may lead the way to a new class of glioma treatment.

Pro-inflammatory cytokines trigger signalling cascades leading to NF-kappaB (nuclear factor-kappaB)-dependent gene expression through IKK [IkappaB (inhibitory kappaB) kinase]-dependent phosphorylation and subsequent degradation of the IkappaB proteins and via induced phosphorylation of p65. These signalling pathways rely on sequentially activated kinases which are assembled by essential and non-enzymatic scaffold proteins into functional complexes. Here, we show that the pro-inflammatory cytokine TNFalpha (tumour necrosis factor alpha) promotes TANK [TRAF (TNF receptor-associated factor) family member associated NF-kappaB activator] recruitment to the IKK complex via a newly characterized C-terminal zinc finger. Moreover, we show that TANK is phosphorylated by IKKbeta upon TNFalpha stimulation and that this modification negatively regulates TANK binding to NEMO (NF-kappaB essential modulator). Interestingly, reduced TANK expression by RNA interference attenuates TNFalpha-mediated induction of a subset of NF-kappaB target genes through decreased p65 transactivation potential. Therefore the scaffold protein TANK is required for the cellular response to TNFalpha by connecting upstream signalling molecules to the IKKs and p65, and its subsequent IKKbeta-mediated phosphorylation may be a mechanism to terminate the TANK-dependent wave of NF-kappaB activation.

Activation of transcription factors such as NF-kappa B occurs through signaling pathways involving sequential phosphorylation of a variety of substrates by distinct kinases. Proper assemby and activation of these kinases require interaction with non-enzymatic and essential partners named scaffold proteins. Here, we describe how the NF-kappa B activating scaffold proteins involved in the signaling pathways triggered by the pro-inflammatory cytokines TNF alpha, IL-1 beta and by the CD40 ligand play such roles. We also illustrate the human genetic diseases that are linked to mutations affecting genes coding for these proteins. We suggest that these scaffold proteins may be specifically targeted by novel therapeutical agents for the treatment of inflammation or cancers.