Abstract
The efficacy of T-cell therapy is inhibited by various tumor-associated immunosuppressive ligands and soluble factors. Such inhibitory signals turn specific T-cell signaling pathways on or off, impeding the anticancer functions of T cells. Many studies have focused on PD-1 or CTLA-4 blockade to invigorate T-cell functions through CD28/B7 signaling, but obtaining robust clinical outcomes remains challenging. In this study, we use CRISPR/Cas9 to potentiate T-cell function by increasing CD3 signaling via knockout of diacylglycerol kinase (DGK), an enzyme that metabolizes diacylglycerol to phosphatidic acid. Knockout of DGK augmented the effector functions of CAR-T cells in vitro via increased TCR signaling. DGK knockout from CAR-T cells rendered them resistant to soluble immunosuppressive factors such as TGFβ and prostaglandin E2 and sustained effector functions under conditions of repeated tumor stimulation. Moreover, DGK knockout caused significant regression of U87MGvIII glioblastoma tumors through enhanced effector functions in a xenograft mouse model. Collectively, our study shows that knockout of DGK effectively enhances the effector functions of CAR-T cells, suggesting that CRISPR/Cas9-mediated knockout of DGK could be applicable as part of a multifaceted clinical strategy to treat solid cancers.Significance: This novel study demonstrates efficient ablation of diacylglycerol kinase in human CAR-T cells that leads to improved antitumor immunity and may have significant impact in human cancer immunotherapy. Cancer Res; 78(16); 4692-703. ©2018 AACR.
Highlights
Chimeric antigen receptor (CAR) T cells have emerged as the leading paradigm for treating various hematologic malignancies
We examined whether PD-1 blockade would further increase the effector function of diacylglycerol kinase (DGK) KO 139 CAR-T cells by using PD-L1–positive U87vIII cells (Supplementary Fig. S5A)
Based on the data showing that DGK KO effectively invigorated T-cell receptor (TCR) distal signaling, we examined whether DGK KO could reduce the sensitivity of 139 CAR-T cells to signal1 inhibitors
Summary
Chimeric antigen receptor (CAR) T cells have emerged as the leading paradigm for treating various hematologic malignancies. Treatment with CD19-targeting CAR-T cells resulted in complete remission (CR) rates of 82% to 94% and 50% to 75% for B-cell acute lymphoblastic leukemia (ALL) and chronic lymphoblastic leukemia (CLL), respectively [1]. Despite this success in blood cancers, CAR-T therapy has not shown efficient antitumor activity against solid cancers, such as lung, colon, breast, and brain cancers, except for a promising clinical outcome of anti-GD2 CAR-T cells against neuroblastoma [2]. Even if CAR-T cells reach inside the tumors, their anticancer activities can be compromised by multiple layers of immunosuppressive mechanisms induced by a range of checkpoint
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