Signaling Analyses of Therapeutic T cells Engineered with Synthetic Receptors

Abstract

Revolutionary new cancer therapies are harnessing the power of our immune systems. One type of cancer immunotherapy employs T cells that are genetically re-programmed to efficiently recognize and attack a patient’s tumor. Tumor recognition by T cells is normally mediated by T cell receptors (TCRs), but synthetic constructs called chimeric antigen receptors (CARs) are increasingly used in T cell therapies. In simple terms, CARs merge specific protein-binding antibody elements with TCR-related signaling moieties. Clinical trials demonstrate that CAR-engineered T cells can produce dramatic regressions in certain individuals with hematologic malignancies. However, relapses too often occur and, to date, CAR T cell therapy has rarely been effective against solid tumors. Successful cancer-killing activities require that specific activating signals are sent throughout the T cell when the CAR binds to certain proteins on a cancer cell. Enhancing these signals could optimize antitumor activity, but has proven challenging because we incompletely understand how receptor affinity, structural elements and signaling domains affect T cell effector functions. In my thesis-directed studies, I applied innovative cell signaling analyses to increase our understanding of the molecular events that promote CAR T cell efficacy. I developed an unbiased mass spectrometry technique to comprehensively interrogate signaling proteins in primary human T cells and applied this technique to describe synthetic CAR and natural TCR signaling in detail. By coupling signaling analyses to separate measures of gene transcription, protein-protein interactions, T cell function in vitro and therapeutic efficacy in mouse models of cancer, my work provides new insights into how signals delivered by synthetic receptors impact T cell function. Collectively, my findings enhance our understanding of the molecular underpinnings of successful CAR T cell therapy and provide a framework to guide the design of more effective therapeutic receptors.