TMIC-57. Inducing tumor associated tertiary lymphoid structures using cellular therapy

Abstract INTRODUCTION Targeting the tumor microenvironment (TME) to be more immune permissive is a potential strategy for enhancing immunotherapies, such as chimeric antigen receptor T cell (CAR-T) therapy, providing a promising avenue for treating aggressive tumors such as glioblastoma multiforme (GBM). Tertiary lymphoid structures (TLS) are ectopic lymphoid aggregates that arise in response to chronic inflammation and mimic the structure and function of secondary lymphoid organs. The spontaneous presence of TLS in some solid tumors, including GBM, is associated with improved clinical outcome and responsiveness to immunotherapy. We hypothesize that membrane tethered anti- LTβR Sc-Fv (mTa) T cells can function as lymphoid tissue inducer cells (LTi) and interact with lymphoid tissue organizer cells (LTo) in the TME, that express lymphotoxin-β receptor (LTβR), to nucleate TLS. METHODS We screened commercially available murine LTβR agonist antibodies to induce NFkB signaling by western blot and NFκB-GFP reporter assay. An immunocompetent murine glioma model was used to examine the formation of TLS-like lymphoid aggregates. Hematoxylin and eosin (H&E) and Opal multiplex immunofluorescence staining was performed for the detection and classification of TLS-like lymphoid aggregates. RESULTS We found multiple TLS-like lymphoid aggregates in brain sections from mice injected with the lead candidate from our screen. We cloned a membrane-tethered version of this antibody alongside a CAR construct to generate mTa-CAR-T cells. mTa-CAR T cells could activate LTβR in an NFκB-GFP reporter assay. We proceeded to intratumorally inject these cells into a syngeneic mouse GBM tumor model to evaluate TLS induction and assess the ability of mTa-CAR T cells to improve antitumor efficacy and survival. CONCLUSION This study attempts to identify strategies to remodel the TME of GBM and nucleate TLS using cellular therapy to improve the response to CAR-T therapy and survival of GBM patients.