Non-clinical efficacy, safety and stable clinical cell processing of induced pluripotent stem cell-derived anti-glypican-3 chimeric antigen receptor-expressing natural killer/innate lymphoid cells.

The use of allogeneic, pluripotent stem-cell-derived immune cells for cancer immunotherapy has been the subject of recent clinical trials. In Japan, investigator-initiated clinical trials will soon begin for ovarian cancer treatment using human leukocyte antigen (HLA)-homozygous-induced pluripotent stem cell (iPSC)-derived anti-glypican-3 (GPC3) chimeric antigen receptor (CAR)-expressing natural killer/innate lymphoid cells (NK/ILC). Using pluripotent stem cells as the source for allogeneic immune cells facilitates stringent quality control of the final product, in terms of efficacy, safety and producibility. In this paper, we describe our methods for the stable, feeder-free production of CAR-expressing NK/ILC cells from CAR-transduced iPSC with clinically relevant scale and materials. The average number of cells that could be differentiated from 1.8-3.6 × 106 iPSC within 7 weeks was 1.8-4.0 × 109 . These cells showed stable CD45/CD7/CAR expression, effector functions of cytotoxicity and interferon gamma (IFN-γ) production against GPC3-expressing tumor cells. When the CAR-NK/ILC cells were injected into a GPC3-positive, ovarian-tumor-bearing, immunodeficient mouse model, we observed a significant therapeutic effect that prolonged the survival of the animals. When the cells were injected into immunodeficient mice during non-clinical safety tests, no acute systemic toxicity or tumorigenicity of the final product or residual iPSC was observed. In addition, our test results for the CAR-NK/ILC cells generated with clinical manufacturing standards are encouraging, and these methods should accelerate the development of allogeneic pluripotent stem cell-based immune cell cancer therapies.

Induction of cytotoxic T lymphocytes against human cancer cell lines using dendritic cell-tumor cell hybrids generated by a newly developed electrofusion technique.

Recently, dendritic cells (DCs) and DC-tumor cell hybrids (DC-tumor hybrids) have been used for cancer vaccine therapy in a clinical trial. DC-tumor hybrids combine the potent antigen-presenting capacity of DCs with the ability to present all tumor antigens expressed on tumor cells to T cells. We used DC-tumor hybrids as stimulator cells to induce tumor-specific cytotoxic T lymphocytes (CTLs) in vitro. DC-tumor hybrids were generated from human monocyte-derived DCs and human cancer-cell lines (GT3TKB, lung cancer; GCIY, gastric cancer) by our newly developed electrofusion technique, established and refined with the use of mouse cells. To evaluate the capacity of DC-tumor hybrids generated by our method to induce tumor antigen-specific CTLs, we performed a cytotoxic assay and an interferon-gamma release assay using CD8-dominant effector lymphocytes induced by them. DC-tumor hybrids more effectively induced tumor-specific primary T-cell response than did stimulation with DCs co-cultured with irradiated tumor cells overnight, irradiated tumor cells alone, or a mixture of DCs and irradiated tumor cells. DC-tumor hybrids were generated at a high fusion rate by our electrofusion technique. When CTLs were induced by DC-tumor hybrids in vitro, the high fusion rate did not contribute to the induction of CTLs with increased tumor-specific cytotoxicity. The addition of interleukin-12 to the culture medium did not augment the cytotoxicity of CTLs. Overall, our results suggest that DC-tumor hybrids effectively induce human tumor-specific CTLs and may thus be applicable for clinical trials of adoptive immunotherapy.

A new strategy using autologous dendritic cells and lymphokine-activated killer cells for cancer immunotherapy: efficient maturation of DCs by co-culture with LAK cells in vitro.

Among a variety of antigen presenting cells (APCs), accumulating results support that the mature dendritic cell (DC) has the potential to induce efficient cytotoxic T lymphocyte (CTL) responses in the context of peptide-based immunotherapy. DCs have been known to assume the mature form by signaling through the CD40-CD40 ligand (CD40L) interaction, which may be provided by activated CD4+ T cells expressing abundant CD40L molecules on their surfaces. Here, we report that DCs generated from peripheral blood monocytes obtained from patients with advanced cancer exhibit a mature phenotype after co-culturing with autologous lymphokine-activated killer (LAK) cells generated by the stimulation of peripheral blood mononuclear cells with anti-CD3 monoclonal antibody (mAb) and interleukin (IL)-2. Part of this process appeared to be dependent on the expression of CD40L on the surface of LAK cells, although it was also suggested that some other humoral factors produced by LAK cells may be involved in this effect as well. DCs derived from the donors, of which LAK cells demonstrated a higher Th1/Th2 ratio upon activation determined by the intracellular detection of interferon-gamma and IL-4, showed more efficient maturation upon co-culture with LAK cells than DCs from donors with a low Th1/Th2 ratio. Importantly, these matured DCs induced a two-times stronger antigen-presenting capacity measured by an allo-reactive mixed lymphocytes reaction assay as compared to immature DCs. These results imply the use of the combination of DCs and LAK cells for immunotherapy against cancer.

[Immunogenic reactivity of CTLs induced by electrofusion cells of human dendritic cells and gastric cancer cells].

In tumor immunotherapy, there were several reports of attempts to induce anti-tumor immunity by fusion hybrid cells generated with dendritic and tumor cells. One of them reported that vaccination of hybrid cells resulted in a remarkable reduction of tumor cells in a lab mouse experiment. In our study, fusion cells were generated successfully with human matured dendritic and human gastric cancer cells by electrofusion technique and employed to induce CTLs. The evaluated fusion rate was 47.8% by FACS analysis. We tried to induce CTLs by co culture of effector and stimulator cells in the presence of IL-2, IL-7 and IL-12 for 4 weeks. Although it was not statistically significant in tumor cytotoxic assay, effector cells induced by the fusion cells as stimulator cells showed a few cytotoxic responses in an immunological tumor specific manner. Our data suggest that fusion hybrid cells may facilitate stimulation and expansion of tumor-specific T cells, but further investigation is required for clinical application of fusion cells in adoptive immunotherapy.