EXTH-09. GENE MODIFICATION OF HEMATOPOIETIC STEM AND PROGENITOR CELLS FOR IMPROVEMENT OF IMMUNOTHERAPIES FOR MALIGNANT GLIOMAS

Abstract Patients living with high-grade gliomas have a poor survival prognosis. Furthermore, standard of care treatment for these malignant gliomas has not significantly improved in the past decades. Our laboratory previously demonstrated that the combination of two different immunotherapies with HSPCs provided a significant survival benefit in preclinical brain tumor models, however, this therapeutic combination is still not 100% curative. We hypothesized that gene modification of HSPCs could add additional therapeutic benefit to immunotherapies for the treatment of resistant gliomas. Hematopoietic stem and progenitor cells (HSPCs) have been widely used in different clinical settings due to their ability to self-renew and differentiate into all immune cell lineages. In recent years, HSPCs have been the target of a variety of gene editing research efforts to decipher the most effective method for gene modification to use for therapeutic purposes. After comparison with previously established methods, we optimized a protocol for the successful editing of murine HSPCs and human CD34+ cells. Using Cas9 mRNA and sgRNAs in HSPCs, we achieved up to 80% reduction in gene expression. This method is superior to others due to its efficient, quick, inexpensive, and reliable nature. We also showed that, by knocking-down IL-6R in HSPCs, we can drive their differentiation into dendritic cells, while decreasing MDSCs and macrophages. Furthermore, gene-modified HSPCs are also capable of bone marrow reconstitution of lethally irradiated mice. Currently, we are testing whether the combination of gene-modified HSPCs with immunotherapy provides additional survival benefit to unmodified HSPCs with immunotherapy in a resistant murine glioma model.