Glioblastoma Stem Cell Targeting Chimeric Antigen Receptor T Cells Modified Using Phage Display Isolated Peptides

Abstract Glioblastoma (GBM) is the most aggressive primary brain tumor with high mortality rates and resistance to conventional therapy. Their resistance to conventional therapy has been attributed to the presence of cancer stem cells (CSCs), a sub-population of tumor cells capable of self-renewal and tumor initiation. Developing novel strategies to specifically target GSCs may allow more effective therapeutic strategies. Using in vivo phage display biopanning, we have identified several peptides with the potential to selectively target and bind GSCs. We wished to leverage the GSC targeting properties of the peptides to augment therapeutic delivery vehicles for the development of novel targeting strategies. We used a combination of GSC targeting peptides to modify the antigen-binding domain of chimeric antigen receptors, by arranging the peptides in tandem at the N-terminus of the CAR molecule. These tandem peptides were tested for binding to GSCs in vitro and in vivo. The functionality of the CAR-T cells was evaluated by measuring cytokine release in the supernatant after overnight co-culture through ELISA. Apoptosis was evaluated by flow cytometry with Annexin V staining. Two different GSC-targeting peptide CAR-T cells demonstrated specific targeting GSCs. Following co-culture with GSCs, GSC targeting CAR-T cells were activated with release of Interferon gamma and subsequently induced GSCs specific apoptosis. These results demonstrate the use of phage display biopanning to isolate GSC targeting peptides which may be used to develop novel GBM specific cytotoxic therapies.