Transgene-enforced co-stimulation of CD4+ T cells leads to enhanced and sustained anti-tumor effector functioning.

Background The role of co-stimulation in CD4+ T cell activation by professional APC is well established, while less is known of the role co-stimulation plays when CD4+ T cells interact directly with tumor cells. Methods Through genetic engineering of human CD4+ T cells, we tested the hypothesis that integration of co-stimulatory signaling domains within a tumor-targeting chimeric Ag receptor (CAR), the IL-13Ralpha2-specific IL-13-zetakine (IL13zeta), would enhance CD4+ T cell mediated responses against tumors that fail to express ligands for co-stimulatory receptors. Results Compared with CD3zeta-mediated activation alone, CD4+ effector T cells expressing the IL13-CD28-41BBzeta CAR exhibited augmented/sustained MAPK and AKT activity, up-regulated Th1 cytokine production, and enhanced cytolytic potency against tumor targets. Moreover, upon recursive stimulation with tumor, the IL13-CD28-41BBzeta+ cells retained/recycled their lytic function, whereas IL-13zeta+ CD4+ cells became anergic/exhausted. These in vitro observations correlated with enhanced in vivo control of established orthotopic CNS glioma xenografts in immunodeficient mice mediated by adoptively transferred ex vivo-expanded CD4+ T cells expressing the co-stimulatory CAR. Discussion Together these studies demonstrate the importance of integrating co-stimulation with CD3zeta signaling events to activate fully CD4+ anti-tumor effector cells for sustained function in the tumor microenvironment.