GM-CSF disruption in CART cells modulates T cell activation and enhances CART cell anti-tumor activity (original) (raw)

Inhibitory myeloid cells and their cytokines play critical roles in limiting chimeric antigen receptor T (CART) cell therapy by contributing to the development of toxicities and resistance following infusion. We have previously shown that neutralization of granulocyte-macrophage colony-stimulating factor (GM-CSF) prevents these toxicities and enhances CART cell functions by inhibiting myeloid cell activation. In this report, we study the direct impact of GM-CSF disruption during the production of CD19-directed CART cells on their effector functions, independent of GM-CSF modulation of myeloid cells. In this study, we show that antigenspecific activation of GM-CSF KO CART19 cells consistently displayed reduced early activation, enhanced proliferation, and improved anti-tumor activity in a xenograft model for relapsed B cell malignancies. Activated CART19 cells significantly upregulate GM-CSF receptors. However, the interaction between GM-CSF and its upregulated receptors on CART cells was not the predominant mechanism of this activation phenotype. GM-CSF KO CART19 cell had reduced BH3 interacting-domain death agonist (Bid), suggesting an interaction between GM-CSF and intrinsic apoptosis pathways. In conclusion, our study demonstrates that CRISPR/Cas9-mediated GM-CSF knockout in CART cells directly ameliorates CART cell early activation and enhances anti-tumor activity in preclinical models. Despite the remarkable activity of CD19-directed chimeric antigen receptor T cell (CART19) therapy in treating B-cell hematologic malignancies, 1, 2 limitations include 1) the development of potential life-threatening complications such as neurotoxicity (NT) and cytokine release syndrome (CRS) 3, 4 and 2) lack of durable response. 5-8 Emerging literature suggests that inhibitory myeloid cells and their cytokines play an important role in inducing CART cell toxicities and contribute to CART inhibition. 9-12 Specifically, and of relevance to the work presented in this manuscript, granulocyte-macrophage colony-stimulating factor (GM-CSF) is implicated in the development of NT and CRS after CART19 therapy based on correlative studies from pivotal clinical trials. 13, 14 Cox et al.