Abstract 1310: Peptide delivery of siRNA in GBM

Glioblastoma Multiforme (GBM), a grade VI glioma, is an aggressive malignant tumorwith a poor prognosis. With an incidence rate of 3.19 per 100,000, GBM has a median survivalrate of 12-15 months and a five-year survival rate of less than 5%. Typical treatments involvesurgical removal, chemotherapy, and radiation; however, these treatments still result in a lowsurvival rate and can lead to potential harm to healthy cells. Therefore, a new therapeutic isneeded for GBM treatment to improve patient outcomes. RNAi, a naturally found process,utilizes siRNA to target specific mRNA for degradation to inhibit protein translation and hasshown clinical potential for targeting and silencing oncogenes. However, barriers to siRNAdelivery, such as cellular uptake, non-specificity, and lack of endosomal escape hinder clinicaltranslation of RNAi therapeutics. Peptides are a promising carrier for siRNAs and havedemonstrated the potential to overcome barriers to delivery. The purpose of this study is todesign a novel tandem peptide for siRNA delivery, evaluate ability to mediate knockdown of atarget oncogene, and compare the efficacy of the tandem peptide to the individual peptidesalone. The tandem peptide is a novel combination of a fusogenic peptide and a targetingpeptide. STAT3, the target gene, is an oncogene that plays a role in cell proliferation,differentiation, apoptosis, and angiogenesis in GBM. Initial results have confirmed basal expression of EGFR and STAT3 in all three GBM cell lines, LN18, U118, and T98G.Characterization of the fusogenic, targeting, and tandem peptides indicated formation of monodispere nanoparticles with diameters less than 150 nm when complexed with siRNA. Furthermore, gel shift assays were conducted and confirmed that the tandem peptide protectedthe siRNA from degradation in 50% FBS. MTS assays conducted in all three cell lines for eachpeptide confirmed that there was no significant cytotoxicity due to the vehicles alone. Finally, flow cytometry confirmed uptake of the tandem peptide in T98G cell line. Therefore, it ishypothesized that the tandem peptide composed of both fusogenic targeting peptide willenhance cell-specific uptake of STAT3 siRNA into glioblastoma cells for mediating endosomalescape, resulting in more effective gene silencing and associated downstream effects comparedto the fusogenic and targeting peptides alone. Future studies include immunofluorescence for uptake and endosomal escape, knockdown studies (MTS, Western Blot, a