Abstract

Generation of CTLs from iPSCs Transduced with TCR Genes: Toward the Development of “Off-the-Shelf T Cells”

Hiroshi Kawamoto, Professor, Laboratory of Immunology, Institute for Frontier Life and Medical Sciences, Kyoto University

We have proposed a strategy to use iPSC technology for expansion of tumor antigen specific CTLs; iPSCs produced from T cells (T-iPSCs) inherit rearranged TCR genes, and thus all regenerated T cells from T-iPSCs express the same TCR. Based on this idea, we have succeeded in regenerating MART1-specific CTLs from a melanoma patient (Vizcardo et al, Cell Stem Cell, 2013). Recently we have developed a culture method by which CTLs expressing CD8alpha-beta heterodimer with high antigen specific cytotoxicity can be regenerated.

To apply this approach in allogeneic setting, we thought of a method in which non-T cell derived iPSCs are transduced with exogenous TCR genes (TCR-iPSCs). As a source of iPSCs, we decided to use HLA-haplotype homo iPSCs; regenerated cells from such iPSCs could be transplanted to HLA-hetero recipients. At present, top three frequent HLA-homo iPSC lines are available, covering 30% of the Japanese population. To test the idea of TCR-iPSCs, we lentivirally transduced non-T cell derived iPSCs with WT1-specific TCR gene cloned by our group from CTLs regenerated from WT1-T-iPSCs, which had originally been established from WT1-specific CTLs expanded from peripheral T cells of a healthy volunteer. Regenerated CTLs from TCR-iPSCs were found to exhibit cytotoxicity comparable to those from T-iPSCs carrying the same WT1-TCR, indicating that this strategy works well.

We applied this system to the TCRs that have been used in clinical trials in Japan. We transduced HLA-homo iPSCs with WT1-specific TCR that has been used in clinical trial of TCR gene transfer therapy against leukemia (Ehime University). Regenerated CTLs from WT1-TCR-iPSCs suppressed growth of WT1-expressing renal cell carcinoma cells in patient-derived xenograft model. We also applied this system to NY-ESO1-TCR that has been used in clinical trial targeting synovial sarcoma or melanoma (Mie University). Regenerated NY-ESO1-CTLs showed cytotoxicity against myeloma cells in xenograft model. These results collectively demonstrate the feasibility of the TCR-iPSC strategy against various types of cancer, including solid tumor.