Acquisition of full effector function in vitro paradoxically impairs the in vivo antitumor efficacy of adoptively transferred CD8+ T cells

Abstract

T cell differentiation is a progressive process characterized by phenotypic and functional changes. By transferring tumor-specific CD8 + T cells into tumor-bearing mice at various stages of differentiation, we evaluated their efficacy for adoptive immunotherapy. We found that administration of naive and early effector T cells, in combination with active immunization and IL-2, resulted in the eradication of large, established tumors. Despite enhanced in vitro antitumor properties, more-differentiated effector T cells were less effective for in vivo tumor treatment. Several events may underlie this paradoxical phenomenon: (a) downregulation of lymphoid-homing and costimulatory molecules; (b) inability to produce IL-2 and access homeostatic cytokines; and (c) entry into a proapoptotic and replicative senescent state. While the progressive acquisition of terminal effector properties is characterized by pronounced in vitro tumor killing, in vivo T cell activation, proliferation, and survival are progressively impaired. These findings suggest that the current methodology for selecting T cells for transfer is inadequate and provide new criteria for the generation and the screening of optimal lymphocyte populations for adoptive immunotherapy. IntroductionAdoptive cell transfer therapy (ACT), the administration of ex vivoactivated and -expanded autologous tumor-reactive T cells, is currently one of the few immunotherapies that can induce objective clinical responses in significant numbers of patients with metastatic solid tumors (1-3). In a previous study, ACT after lymphodepleting conditioning caused objective responses in 46% of patients with metastatic melanoma refractory to other therapeutic modalities (4). We have now tripled the size of the original study (4), and the objective response rate exceeds 50%, and 11% of all patients treated are complete responders (5).There are several theoretical advantages to the use of ACT in treatment of cancer. Tumor-specific T cells can be activated and expanded to large numbers ex vivo, independently of the immunogenic properties of the tumor. Perhaps most important, the functional and phenotypic qualities of T cells can be selected prior to their adoptive transfer.Much progress has been made in the understanding of the properties of T cell subpopulations associated with states of T cell differentiation in mice and humans, especially those states that are related to the generation of memory T cells capable of protecting against viral challenge (6-9). However, little progress has been made in identifying the characteristics of cell states that are associated with the successful treatment of large, established tumors in mice or in humans.

Efficacy of IL‐2‐ versus IL‐15‐stimulated CD8 T cells in adoptive immunotherapy

“…2C). These data are well in line with previous reports that exposure of antigenstimulated P14 or pmel-1 T cells to IL-2 or IL-15 generates effector or central memory-like CD8 T cells, respectively [6,[8][9][10]12]. We also noted that P14 IL-2 and P14 IL-15 cells differed in functional CD95L/Fas ligand expression since co-culture of P14 IL-2 cells and L1210 target cells expressing CD95/Fas resulted in antigen-independent cell killing whereas co-culture of the same target cells and P14 IL-15 cells had no effect (Fig.…”

“…The degree of specific target cell lysis and the amount of antigen-triggered IFN-g production are frequently used to predict the efficacy of CD8 T cells in vivo. However, several recent studies in the pmel-1 TCR-tg model specific for the self/tumor antigen gp100 of B16 melanoma cells indicated that antigen-stimulated CD8 T cells with a less differentiated phenotype were superior in anti-tumor activity compared with more differentiated cells [8][9][10]. In these studies, in vitro activated pmel-1 CD8 T cells were transferred into sublethally irradiated …”

“…The ability of CD8 T cells to kill target cells or to release IFN-g is often used to predict in vivo efficacy. However, Restifo and co-workers [8][9][10] made the important observation in the pmel-1 TCR-tg model that adoptively transferred CD8 T cells with full effector functions in vitro were less effective in B16 tumor cell elimination in vivo compared with less-differentiated T cells. The results reported here are well in line with these findings, although our regimen of adoptive T-cell therapy was notably different since it did not involve lymphodepletion, additional antigen boostering or cytokine treatment.…”

“…The results reported here are well in line with these findings, although our regimen of adoptive T-cell therapy was notably different since it did not involve lymphodepletion, additional antigen boostering or cytokine treatment. In the pmel-1 transfer model, the low in vivo efficacy of pmel-1 effector cells was explained by impaired priming of the transferred T cells due to inefficient trafficking to secondary lymphoid tissues [10] and due to their terminal-differentiation stage [8].In the transfer systems described here, P14 T cells cultured in saturate amounts of IL-2 (P14 IL-2 cells) were inefficient in eliminating tumor cells or reducing LCMV titers in contrast to P14 cells that exhibited high efficacy in vivo. Moreover, the experiments revealed that P14 IL-2 cells disappeared rapidly in the recipient mice after transfer whereas P14 IL-15 cells persisted for prolonged time.…”

Ex vivo AKT-inhibition facilitates generation of polyfunctional stem cell memory-like CD8+ T cells for adoptive immunotherapy

“…1-3,5-9,25,29,32,34 This perspective should promote further research and clinical translation of adoptive T cell therapy with interference of the PI3K/AKT/mTOR or Wnt-signalling pathway. 15-19,21,33 Here we show that AKT-inhibition can be used for the generation of a unique T SCM -like CD8 + T cell product for adoptive transfer.…”