Transcriptional inhibition of Notch signaling using cell penetrating fusion proteins.

Abstract

e13525 Background: Notch signalling is deregulated in a number of cancers and is possibly involved in cancer stem cell development. It is postulated that cancers such as breast can become addicted to Notch signalling presenting opportunities for tumour-specific intervention. Due to the presence of at least 4 cell surface receptors that mediate Notch signalling, conventional targeting agents such as monoclonal antibodies cannot inhibit them all. As all the signalling cascades converge on the Notch transcriptional complex (NTC) in the nucleus, inhibition of gene expression by disrupting this machinery is an attractive strategy to overcome this redundancy. Methods: Towards this, we have developed a fusion protein based on the potent cell penetrating protein (CPP) antennapedia (Antp) recombinantly fused to a dominant-negative truncated mastermind-like protein (DN-MAML) called TR4. We have also developed a method of incorporating CPP to deliver intracellular antibody fragments against nuclear targets such as Notch and mastermind. Results: The Antp-DN-MAML protein (TR4) has similar potency to many of the gamma-secretase inhibitors being developed against this pathway but more specific for the NTC.TR4 can inhibit tumour cells in vitro and in vivo and provide some insight into the mechanism of action. Also such intracellular targets are accessible to antibodies, provided they are delivered using CPP such as antennapedia. Conclusions: .As a model system, scFvs have been raised to key epitopes in the NTC which can lead to complex inhibition and the same downstream effects as TR4.In addition, we further demonstrate that there is a more general approach to trascription factor inhibition using single-chain Fvs fused to Antp