TGF-β1 Potentiates Adoptive Immunotherapy of Hematological and Solid Tumors Using ex vivo Expanded γδ T-Cells

Despite their role in cancer surveillance, adoptive immunotherapy using γδ T-cells has achieved limited efficacy. To enhance trafficking to bone marrow, circulating γδ T-cells were expanded in serum-free medium containing TGF-β1 and IL-2 (γδ[T2] cells).Unexpectedly, the yield and viability of γδ[T2] cells were also increased by TGF-β1,when compared to γδ[2] controls (IL-2 alone). γδ[T2] cells were less differentiated and yet displayed increased cytolytic activity, cytokine release and anti-tumor activity in several leukemic and solid tumor models. Efficacy was further enhanced by cancer cell sensitization using amino bisphosphonates or cytarabine, or by CAR re-programming. A number of contributory effects of TGF-β1 were identified, including prostaglandinE2 receptor downmodulation, upregulation of CD103 and enhanced IL-9 production by γδ[T2] cells. Biological relevance is supported by the identification of a favorable γδ[T2] signature in acute myeloid leukemia. Given their enhanced therapeutic activity and compatibility with allogeneic use, γδ[T2] cells warrant evaluation in cancer immunotherapy.