Evaluation of GITRL coexpression on the therapeutic efficiency of anti-GD2 CAR-T cells in a preclinical model of glioblastoma multiforme

Abstract

The adoptive therapy of T lymphocytes expressing chimeric antigen receptors (CAR) has demonstrated impressive results in the treatment of some hematological malignancies. However, the therapeutic efficacy of CAR-T cells is still low or non-existent against solid tumors, which make up the vast majority of neoplasms. One of the main reasons for this failure is the presence of ligands and immunosuppressive cells in the tumor microenvironment. The complete activation of T cells requires the engagement of co-stimulatory molecules whose expression is temporally segregated and whose nature of biochemical signals are complementary. This is the case of CD28, expressed constitutively, and GITR, expressed right after the initial activation of T cells. Therefore, our hypothesis is that the combined expression of a CAR containing the co-stimulatory domain CD28 and the GITR ligand (GITRL) modified for secretion will potentiate the antineoplastic action of CAR-T cells. In addition to providing complementary co-stimulatory signals for effector CAR-T cells, secreted GITRL can suppress the action of regulatory T cells in the tumor microenvironment, thus possibly reducing local immunosuppression. In this project, we will use as a model a CAR against the ganglioside GD2, which is highly immunogenic and expressed in tumors of neuroectodermal origin. To test our hypothesis, human T cells will be modified to express a CAR.GD2 or CAR.GD2 and GITRL fused to a signal peptide for constitutive secretion. These CAR-T cells will be evaluated for specificity, antineoplastic potential and in vivo persistence in an orthotopic model of human glioblastoma multiforme. This is a neoplasm known to be aggressive, representing about 60% cases of brain tumors. The development of this construction in human T lymphocytes will be an important opportunity to expand treatment possibilities within the Cell Therapy Center (project CEPID 013/08135-2) with the inclusion of solid neoplasms. We are confident that the potential results of this project will foster the development of a new advanced cellular immunotherapy strategy for the treatment of solid GD2+ neoplasms and will pave the way to increase the antineoplastic efficiency of T-CAR cells against other malignancies. (AU)