Adoptive immunotherapy with functional T cells is a potentially effective therapeutic strategy against various types of cancers and viral infections. A major challenge however lies with the “exhaustion” (loss of cytotoxic and proliferative capacities) of antigen-specific T cells during expansion in culture. For an effective adoptive immunotherapy, what we need is not the “exhausted” T cells, but large number of “young and active” CD8+ T cells that can kill tumors or virus infected cells efficiently. To address this issue, we generated induced pluripotent stem cells (iPSCs) from EBV-specific CD8+ T cells from an EBV-infected patient. We then redifferentiated these iPSCs into CD8+ T cells or we like to call them “rejuvenated” T cells since they are newly generated and highly proleferative. These rejT cells possessed antigen-specific killing activity and exhibited TCR gene rearrangement patterns identical to those of the original T cell clone from the patient. In order to confirm in vivo efficacy of these rejT cell, we innoculated EBV-induced tumors into immunodeficient mice and after confimation of tumor growth, we injected these rejT cells. Results indicated that these rejT cells eliminated tumors more efficiently than the original EBV-specific CD8+ T cells, thus confirming in vivo efficacy of these T cells.
Another aspect we worked on is generation of a functional organ in livestock animals. In the past, we have demonstrated generation of rat pancreas in mouse utilising a method called “blastocyst complementation”. In ancillary work, we successfully generated exogenous-pig pancreata using the same principle. Whilst these studies prepared us to examine the feasibility of generating human PSC-derived pancreata in pancreatogenesis-disabled pigs, some ethical issues on making such “admix chimeras” have yet to be solved. A part of the concern comes from the possibility that human iPSC-derived cells contribute to neural or germ cells in chimeric animals. To overcome this issue, we attempted to restrict differentiation of PSC-derived cells into endodermal organs by introducing a gene that is important for the development of internal organs. When the expression of this gene was induced after transfer of embryo to foster mother, differentiation of ES-derived cells were directed toward interenal organs avoiding contribution of those cells in germ cells, skin and nervous systems. We termed this type of organ generation as “Targeted organ generation” and this should, in principle, reduce the ethical concern when making human-livestock chimeras.
In addition, we found that the inhibition of nuclear translocation of a molecule called b-CATENIN enhances conversion of mouse EpiSCs (non-chimera forming) to naive-like PSCs (chimera forming). Since most human ES/iPSCs are considered EpiSCs and non-chimera forming, the finding is of importance for the generation of human organs in ivestock animals.