IMMU-56. CXCR1/2 MODIFIED CARs CO-OPT RADIATION-INDUCED IL-8 FOR ENHANCED CHEMOTAXIS OF THE CAR T CELLS AND MAXIMAL ANTI-TUMOR EFFICACY

Glioblastomas (GBM) are heterogeneous brain tumors with capacity for malignant propagation. The treatment options are confined to surgery and chemo/radiation with marginal efficacy, thus, identifying novel markers/targets and development of novel targeted therapeutics is requisite. Cancer immunotherapy provides a unique tumor-specific therapy with exquisite precision; however, very few glioma-specific targets have been discovered. We demonstrated that CD70 is ectopically overexpressed on adult and pediatric gliomas. The expression on glial tumor cells is a markedly poor prognostic marker, mediates the recruitment of immunosuppressive myeloid cells through upregulated chemokine networks in GBM tumor cells, and results in the deletion of CD8+ cytotoxic lymphocytes. As such, this molecule plays an important role in glioma-induced immunosuppression and makes the elimination of CD70+ tumor cells an attractive axis for therapeutic targeting.

To address the key obstacle in treating solid tumors using CAR-T cells, we have developed CD70 CAR-2.0 to co-opt the IL-8 chemokine pathway upregulated in CD70+ gliomas by radiation to enhance CNS tropism and persistence in preclinical glioma models.

The CD70 CAR-1.0 was respectively linked with IL-8 receptors, CXCR1 and CXCR2 and cloned into a retroviral vector. The CAR-transduced T cells were tested against GBM lines (including primary tumors) in vitro and human GBM xenograft. The CAR-T cell tumor trafficking/persistence, phenotype, and antitumor efficacy were evaluated.

Radiation markedly enhanced the secretion of IL-8 by glioma cells. While mice receiving unmodified CD70 CAR-T cells undergo gradual disease progression with anergic/exhausted phenotypes, the IL-8R-modified CAR-T cells illustrate markedly enhanced tumor migration and persistence and induce complete tumor regression and long-lasting immunologic memory.

We have co-opted IL-8 release from radiated malignant gliomas, to enhance intra-tumoral T cell trafficking through a new CAR design for maximal anti-tumor activity, thus provide a novel strategy for CAR-T therapy targeting these tumors.