PROJECT SUMMARY Glioblastoma (GBM) is a devastating disease that kills about 18,000 Americans every year. GBM patients are treated with temozolamide and ionizing radiation (IR), but the tumor invariably recurs. The molecular mechanisms driving treatment resistance in GBM are unknown. Molecular targeted therapies including EGFR and VEGF inhibitors, have failed to extend the dismal (15 month median) survival in GBM. Based on our previous work, a direct oncogenic role of NF-B signaling and radio-resistance in some subtypes of GBM has been uncovered. Recently, an independent study validated the efficacy of inhibiting NF-B signaling in GBM. Therefore, we hypothesize that inhibition of NF-B signaling improves survival in GBM. Nonetheless, there is a gap in knowledge regarding the efficacy of NF-B inhibitors and the mechanisms by which they inhibit growth of the various molecular subtypes of GBM. The premise of the application is to test the mechanism of action, efficacy, and the therapeutic benefit of a novel autocatalytic brain tumor-targeted (ABTT) nanoparticle delivery of a NF-B pathway inhibitor, DTP3. In Aim1 we will examine the apoptotic effects of a tripeptide, DTP3, in GBM preclinical models and investigate its mechanism of action. Because DTP3 functions by inhibiting interaction of the NF-κB-regulated anti-apoptotic factor GADD45β with MKK7, we will examine the activation of caspase 3 and the phosphorylation of JNK as a read out of MKK7 activation. In Aim 2 we will test the therapeutic benefits of ABTT-DTP3 as a single agent as well as a combination with fractionated radiation in molecular subtypes of GBM. Primary end-points will be overall survival and bioluminescence-image-guided tumor volume measurement. Mechanism of action will be determined by quantitative assessment of in vivo tumor proliferation, in vivo tumor invasion, histopathological examination of fixed tissue, and examination of JNK phosphorylation. A critical strength of this proposal is that we will utilize a nanoparticle mediated delivery of a peptide to specifically target anti-apoptotic functions of NF- B in brain tumors. This first comprehensive characterization of cancer specific blockade of NF-B using clinical relevant patient derived models of glioma will provide the foundation for clinical trials using NF-B blockade in GBM.