ENHANCING THE EFFICACY OF INNATE CELL-BASED ADOPTIVE CELL THERAPY AGAINST SOLID TUMORS

Abstract

Adoptive cell therapies (ACT) have emerged as a powerful treatment option for cancer. Genetically modifying αβ T cells with a chimeric antigen receptor (CAR) to drive their anti-tumor responses against tumor associated antigens has achieved remarkable clinical success in hematologic malignancies. However, translating CAR-αβ T cells to solid tumors has been hindered due several challenges including difficulties in manufacturing autologous products, heterogenous or loss of antigen expression in the tumor, and the risk of severe adverse effects. Natural Killer (NK) cells and gamma delta (γδ) T cells are promising alternatives for off-the-shelf CAR-based ACT. These cells recognize and target cancer cells independently of major histocompatibility complex class I-mediated antigen presentation, enabling killing of heterogenous tumors with reduced risk of graft-versus-host disease. Among γδ T cell subsets, the Vδ1 subset is of particular interest for ACT due its tissue homing capacity and resistance to activation-induced cell death. Despite significant progress in NK cell therapies over the past decade, the clinical use of Vδ1 T cells has been limited by their low frequency in the peripheral blood and a lack of scalable expansion methods. We have previously shown that expansion with K562 feeder cells expressing membrane bound IL-21 (K562-mb-IL-21) generates highly activated, metabolically reprogrammed NK cells with elevated CD56 expression. In this work, we used CRISPR/Cas9 editing to investigate the functional role of CD56 in expanded NK cells. We found that CD56 deletion did not impair their tumor killing or tissue homing in vivo but increased their reliance on oxidative phosphorylation. Additionally, expression of a HER2-specific CAR enhanced the cytotoxicity of expanded NK cells against tumor cells but did not enhance killing against normal cells expressing HER2. Further, we demonstrate that K562-mb-IL-21 feeder cells enable long-term expansion of γδ T cells from peripheral blood, with enrichment of the Vδ1 T cell subset. These expanded γδ T cells are metabolically fit and exert broad innate cytotoxicity against solid tumor cells, which can be further enhanced through expression of a CAR. Overall, this work demonstrates the potential of metabolically fit, CAR-expressing expanded NK cells and Vδ1 T cells as safe and effective off-the-shelf treatments for solid tumors.