Generation of GM-CSF-producing antigen-presenting cells that induce a cytotoxic T cell-mediated antitumor response

Abstract

Immunotherapy using dendritic cells (DCs) is a promising treatment modality for cancer. However, the limited number of functional DCs from peripheral blood has been linked to the unsatisfactory clinical efficacies of current DC-based cancer immunotherapies. We previously generated proliferating antigen-presenting cells (APCs) by genetically engineering myeloid cells derived from induced pluripotent stem cells (iPSC-pMCs), which offer infinite functional APCs for broad applications in cancer therapy. Herein, we aimed to further enhance the antitumor effect of these cells by genetic modification. GM-CSF gene transfer did not affect the morphology, or surface phenotype of the original iPSC-pMCs, however, it did impart good viability to iPSC-pMCs. The resultant cells induced GM-CSF-dependent CD8 + T cell homeostatic proliferation, thereby enhancing antigen-specific T cell priming in vitro. Administration of the tumor antigen-loaded GM-CSF-producing iPSC-pMCs (GM-pMCs) efficiently stimulated antigen-specific T cells and promoted effector cell infiltration of the tumor tissues, leading to an augmented antitumor effect. To address the potential tumorigenicity of iPSCderived products, irradiation was applied and found to restrict the proliferation of GM-pMCs, while retaining their T cell-stimulatory capacity. Furthermore, the irradiated cells exerted an antitumor effect equivalent to that of bone marrow-derived DCs obtained from immunocompetent mice. Additionally, combination with immune checkpoint inhibitors increased the infiltration of CD8 + or NK1.1 + effector cells and decreased CD11b + /Gr-1 + cells without causing adverse effects. Hence, although GM-pMCs have certain characteristics that differ from endogenous DCs, our findings suggest the applicability of these cells for broad clinical use and will provide an unlimited source of APCs with uniform quality.

Improved safety of induced pluripotent stem cell-derived antigen-presenting cell-based cancer immunotherapy

“… 30 However, considering their actual clinical application, the cells should be equipped with safety switches that enable clinicians to immediately control the fates of cells in case of an unexpected adverse event, while retaining their optimal antitumor efficacy. Although increased serum GM-CSF level, tumorigenesis, and systemic adverse effects were not observed in our GM-pMC-based cancer vaccine experiments, 13 some concerns, such as tumor formation and unwanted immune-modulating effects, remain because GM-pMCs have a high proliferative potential and the GM-CSF they produce might cause unanticipated events. To address these issues, we attempted to further control the fate of GM-pMCs using two promising suicide gene systems, by comparing their efficacies.…”

“…These cells have the capacity to capture, process, and present extracellular antigen proteins in the context of MHC class I molecules, and the process is known as cross-presentation. 13 , 14 Moreover, the administration of GM-pMCs loaded with an MHC class I-restricted cancer antigen peptide or a cancer antigen protein stimulates antigen-specific cytotoxic T lymphocytes to inhibit tumor growth; this is comparable with the effect of functionally complete bone marrow-derived DCs. 13 These findings suggest that this GM-pMC system, using human leukocyte antigen (HLA)-matched iPSCs, enable a stable supply of functional APCs on a large scale without the need for repeated invasive blood samplings, thereby serving as an alternative to autologous DCs.…”

“…To overcome such issues, we established a technology for generating DC-like antigen-presenting cells (APCs) derived from induced pluripotent stem cells (iPSCs), which possess an unrestricted potential to proliferate and differentiate. 7 , 8 , 9 , 10 , 11 , 12 , 13 Myeloid lineage cells were initially induced from mouse embryonic stem cells (ESCs) or iPSCs, and then transfected with the pro-proliferative c-Myc gene to generate cytokine-dependent proliferating myeloid cells (ESC- or iPSC-pMCs). 10 By genetically engineering these iPSC-pMCs, we further expressed granulocyte macrophage colony-stimulating factor (GM-CSF), a growth factor for iPSC-pMCs, to establish GM-pMCs.…”

“… 10 By genetically engineering these iPSC-pMCs, we further expressed granulocyte macrophage colony-stimulating factor (GM-CSF), a growth factor for iPSC-pMCs, to establish GM-pMCs. 13 GM-pMCs express major histocompatibility complex (MHC) class I/II and costimulatory (CD80 and CD86) molecules and proliferate in a manner that depends on the self-produced GM-CSF. These cells have the capacity to capture, process, and present extracellular antigen proteins in the context of MHC class I molecules, and the process is known as cross-presentation.…”

“…Although GM-pMCs have a high proliferative capacity, they are not associated with either tumorigenicity or autoimmune-related organ dysfunction. 13 Moreover, even when irradiated before administration to suppress proliferation, GM-pMCs efficiently induce the proliferation of cancer-reactive T cells in vivo . 13 However, as all possible adverse events cannot be predicted, another safety net that is applicable even after administration might be needed.…”