Human T Cells Engineered To Express a Programmed Death 1/28 Costimulatory Retargeting Molecule Display Enhanced Antitumor Activity

Abstract

Adoptive transfer of T cells genetically modified to express cancer-specific receptors can mediate impressive tumor regression in terminally ill patients. However, T cell function and persistence over time could be hampered by the activation of inhibitory costimulatory pathways, such as programmed death 1 (PD1)/programmed death ligand 1, leading to T cell exhaustion and providing tumor cells with an escape mechanism from immunosurveillance. In addition, the lack of positive costimulation at the tumor site can further dampen T cell response. Thus, as T cell genetic engineering has become clinically relevant, we aimed at enhancing T cell antitumor activity by genetically diverting T cell–negative costimulatory signals into positive ones using chimeric costimulatory retargeting molecules and which are composed of the PD1 extracellular domain fused to the signaling domains of positive costimulatory molecules such as CD28 and 4-1BB. After characterizing the optimal PD1 chimera, we designed and optimized a tripartite retroviral vector that enables the simultaneous expression of this chimeric molecule in conjunction with a cancer-specific TCR. Human T cells, transduced to express a PD1/28 chimeric molecule, exhibited enhanced cytokine secretion and upregulation of activation markers upon coculture with tumor cells. These engineered cells also proliferated better compared with control cells. Finally, we tested the function of these cells in two xenograft models of human melanoma tumors and show that PD1/28-engineered human T cells demonstrated superior antitumor function. Overall, we propose that engineering T cells with a costimulatory retargeting molecule can enhance their function, which bears important implications for the improvement of T cell immunotherapy.

Chimeric PD-1:28 Receptor Upgrades Low-Avidity T cells and Restores Effector Function of Tumor-Infiltrating Lymphocytes for Adoptive Cell Therapy

“…PD-1:28 engineering invigorated TILs that were functionally disabled in human RCC environments. These TILs recovered Th1-cytokine secretion without unleashing Th2 or IL10 programs presumably based on restoration of ERK and AKT pathways as shown in our in vitro coculture system and previous work using similar receptors (25,26). PD-1:28 ameliorated T-cell inhibition that involved native PD-1/PD-L1 interactions and induced the costimulatory signaling pathway.…”

“…Harnessing them for the antitumor response would enlarge and enrich the spectrum of T cells for ATT. As previous data have shown that PD-1:28 receptors can improve TCR-and chimeric antigen receptor (CAR)-engineered T cells (25,26,38,39), we engineered low-avidity T cells with a PD-1:28 chimeric signaling receptor to explore whether their functional activity could be enhanced allowing their inclusion in a library of TCRs for ATT. We show that PD-1:28 chimeric receptor can be stably expressed on the surface of human T cells.…”

“…In challenging environments, costimulation has been shown to improve effector function as it enables refill of lytic granules and T-cell expansion (23,24). Thus, we generated chimeric receptors composed of the PD-1 extracellular domain and the CD28 signaling domain (PD-1:28) following published designs (25,26). PD-1:28-engineered T cells should receive costimulatory signals to support survival, proliferation, and TCR signaling when interacting with PD-1 ligand (PD-L1) on tumor cells.…”

T-cells “à la CAR-T(e)” – Genetically engineering T-cell response against cancer

“…It was suggested the role in CAR signal transduction via TM domain that comes into interaction with different membrane co-receptors [114]. We also recently showed that CD28 TM domain maybe superior to the native one in certain types of chimeric receptors [105,115]. Still, more research is required to obtain a more reliable understanding of TM domain impact on CAR stability and function [116].…”

T-cell–based Immunotherapy: Adoptive Cell Transfer and Checkpoint Inhibition

“…CTLA-4/CD28 chimera maximized T-cell antitumor function in preclinical lymphoma and melanoma syngenic mouse models (38). T cells modified to express PD-1/CD28 chimeric molecules exhibited enhanced cytokine secretion, upregulation of activation markers, and improved proliferation upon coculture with tumor cells in vitro when compared with control cells, and superior in vivo antitumor function in two xenograft models of human melanoma tumors (39). These innovative chimeric proteins can be cotransduced with tumor-targeting CARs to combine tumor T-cell specificity, T-cell activation, and abrogation of checkpoint inhibition in a single genetically modified T-cell.…”