Project Grant R01CA284604

OPTIMIZING TCR-CD3 SIGNALING FOR IMMUNOTHERAPY OF CANCER - ABSTRACT THE RECENT DEVELOPMENT OF T CELL-BASED CANCER IMMUNOTHERAPIES, INCLUDING CHECKPOINT BLOCKADE (ANTI-PD-1, ANTI-CTLA-4 AND OTHERS) OR ADOPTIVE T CELL THERAPY (ACT) USING MODIFIED PATIENT T CELLS, HAS LED TO IMPROVED PATIENT OUTCOMES FOR A VARIETY OF CANCERS. HOWEVER, DURABLE RESPONSES ARE OBSERVED IN ONLY A FRACTION OF PATIENTS. FURTHER PROGRESS CAN BE MADE BY STUDYING AND TARGETING DIFFERENT T CELL SIGNALING PATHWAYS, SUCH AS THE T CELL RECEPTOR (TCR)-CD3 SIGNALING PATHWAY. T CELL RECOGNITION OF ANTIGEN BY THE TCR AND THE RESULTING PROXIMAL SIGNALING THROUGH SURROUNDING CD3 SUBUNITS ARE KEY STEPS IN THE INITIATION OF TUMOR-KILLING. PREVIOUS STUDIES THAT TARGETED THE ANTIGEN BINDING SITE OF THE TCR FOR ENHANCING T CELL RESPONSES TO TUMOR ANTIGENS OFTEN LEAD TO OFF- TARGET EFFECTS AND TOXICITY. INSTEAD, IDENTIFICATION OF THE SPECIFIC EXTRACELLULAR INTERACTIONS BETWEEN THE TCR AND CD3 SUBUNITS COULD OFFER PRECISE GUIDANCE FOR THE DEVELOPMENT OF IMMUNOTHERAPEUTIC STRATEGIES THAT MODULATE T CELL IMMUNITY BY TARGETING SIGNALING THROUGH THE TCR-CD3 COMPLEX WITHOUT ALTERING ANTIGEN-SPECIFICITY. OUR PRELIMINARY DATA SHOWED THAT MUTATING RESIDUES IN THE CONSTANT DOMAIN OF THE TCR RESULTED IN ALTERED T CELL CYTOKINE RESPONSES. BASED ON OUR PRELIMINARY DATA, OUR HYPOTHESIS IS THAT BY MODULATING TCR-CD3 SIGNALING, IMMUNE-MEDIATED CYTOTOXICITY TO TUMOR ANTIGENS CAN BE ENHANCED WITHOUT LOSING SPECIFICITY FOR THE CANCER ANTIGEN. TO TEST OUR HYPOTHESIS, IN AIM 1 WE WILL USE AN IN VITRO RETROVIRAL TCR DISPLAY METHOD, A NOVEL CD3- TETRAMER ASSAY, AND AN IN-SILICO STRUCTURE-BASED TCR DESIGN APPROACH TO IDENTIFY SIGNAL-ENHANCING TCR MUTANTS THAT ENABLE T CELLS TO MEDIATE MORE EFFECTIVE IN VITRO TUMOR KILLING. IN AIM 2, WE WILL IDENTIFY THE MECHANISMS THAT DRIVE ALTERED SIGNALING EVIDENCED IN SELECT TCR SIGNAL-ENHANCING AND SIGNAL-HAMPERING MUTANTS. IN AIM 3, IDENTIFIED MUTATIONS WILL BE INTRODUCED INTO GP100-SPECIFIC TCRS WITH DIFFERENT ANTIGEN AFFINITIES AND THEIR IN VITRO AND IN VIVO TUMOR KILLING EFFICACY WILL BE ANALYZED TO CHARACTERIZE THE TUMOR KILLING POTENTIAL, T CELL DIFFERENTIATION, AND T CELL EXHAUSTION PATTERNS OF NEW SIGNAL-ENHANCING T CELL CLONES WITH THE GOAL OF DEVELOPING A NEW STRATEGY FOR EFFECTIVE T CELL THERAPIES AGAINST CANCER.