Constructing Hybrid Cytokine Receptors to Amplify CAR T Cell Anti-Tumor Potency

Abstract

Chimeric antigen receptors (CARs) have achieved remarkable therapeutic efficacy against cancer by linking natural circuits of T cell activation to the recognition of tumor-associated antigens, but optimal anti-tumor responses require an additional input: cytokine stimulation. Here, we explored cellular engineering approaches to deliver cytokine signals directly to CAR T cells to enhance T cell expansion and functional durability. First, we compared a set of engineered receptors providing constitutive gamma chain cytokine signaling (Ch. 1) and found that cytokine inputs promote distinct and potentially complementary behavior in CAR T cells. To investigate combinatorial cytokine signaling, we developed a hybrid IL-7 and IL-21 receptor platform (Ch. 2), which amplified CAR T cell anti-tumor potency and yielded insights into the roles of cytokine signaling outputs (Ch. 3). In some cases, cytokine-driven improvements in CAR T cell efficacy were accompanied by unrestricted T cell growth and subsequent toxicity in vivo. Therefore, we implemented strategies to safely deploy cytokine signaling technology, including drug-responsive molecular switches (Ch. 4) and a synthetic T cell activation-dependent promoter (Ch. 5).