Early Translational I
It is now well accepted that the immune system, or its dysregulation, plays a central role in causing or worsening many of the most common and life-threatening diseases, such as cancer, HIV1 infection, and autoimmune disorders like diabetes. Recent research has raised the exciting possibility that cells of the immune system might be engineered to treat disease. The immune system is produced from blood-forming stem and progenitor cells (Hematopoietic Progenitor Cells/HPC) and consists of different types of lymphoid cells; of these, T cells are essential for immune-competence. In laboratory research, T cells have been engineered to kill cancer cells, become resistant to infections like HIV-1 and produce immune tolerance for autoimmune disease. In many cases, the use of adult sources of HPC or T cells (bone marrow and blood) is not optimal or even feasible. For example, HPC and T cells are absent after bone marrow transplantation and deficient after chemotherapy, they may be infected as in the case of HIV-1, or contaminated with malignant cells as in leukemia. In addition, adult HPC and T cells do not self-renew during culture and so the ability to engineer or expand them to target disease is very limited. Blood cells can be produced from pluripotent stem cells (PSC), i.e. human embryonic stem cells (hESC) and reprogrammed adult cells aka “induced pluripotent stem cells” (iPSC). Our group has shown that PSC-derived HPC can produce T cells after transplantation in mice. This finding opens up unlimited theoretical opportunities for immune cell therapy that would use banks of iPSC, perfectly matched to each patient, that can be expanded in culture indefinitely and can be engineered to produce T cells that target specific diseases, for example to treat cancer, restore the immune system after bone marrow transplantation, chemotherapy and severe infection, and produce immune tolerance to suppress autoimmune diseases and prevent organ rejection after transplantation. However, PSC-derived immune therapy cannot be brought to clinical translation because of the following bottleneck: Current methods of differentiating PSC produce a very low yield of HPC, and these HPC are inefficient at generating the cells of the immune system. In addition, the culture methods are not clinically useful as they involve the co-culture of human PSC with mouse cells. Our goal is to develop methods that can be used clinically to efficiently produce HPC that can in turn generate the cells (particularly T cells) of the immune system. This proposal brings together a multidisciplinary team of physicians and scientists with expertise in the biology of hESC, iPSC, HPC, the development of the immune system, clinical cell therapy and transplantation. These advances will have direct and immediate application for medical therapies that regenerate and regulate the immune system and open therapeutic possibilities for many serious diseases.
Statement of Benefit to California:
Development of methods for regenerative medicine using stem cells will have wide-spread applications to improve the health of millions of Californians and to provide novel, effective therapies for tens of millions of people world-wide. One major area of clinical promise involves the production of blood forming (hematopoietic) progenitors from pluripotent stem cells (PSC) to regenerate and regulate the immune system. Many severe medical conditions can be cured or improved by transplantation of blood-forming hematopoietic stem and progenitor cells (HPC), including cancer and leukemia, genetic diseases of blood cells, such as sickle cell disease and inborn errors of metabolism or of the immune system. HPC may be engineered to make them resistant to infections (e.g. HIV/AIDS) or to target specific cancers and leukemias. Additionally, transplants of HPC may induce states of immunological tolerance to provide new treatments for auto-immune diseases (e.g. Diabetes, rheumatoid arthritis, systemic lupus erythematosis) and to prevent rejection of transplanted cells or organs (e.g. kidney, liver, heart, lung). A major bottleneck to the use of PSC as a source of immune cell therapy is the low numbers of HPC that currently can be made from PSC and the relative inability of these HPC to produce the lymphocytes (T, B and NK cells) that comprise the immune system. This proposal brings together experts in the biology of stem cells, the mechanisms for development of the immune system, and the methods used to interrogate and to manipulate these cell systems. A logical series of milestones will be achieved to improve production of HPC from PSC using methods that can be used clinically and to improve the ability of HPC, in turn, to produce the immune system, These advances will have direct and immediate application for medical therapies that regenerate and regulate the immune system and will thus have wide-ranging application to the many diseases now known to be caused or worsened by immune dysregulation. All scientific findings and biomedical materials produced from our studies will be publicly available to non-profit and academic organizations in California, and any intellectual property developed by this Project will be developed under the guidelines of CIRM to benefit the people of the State of California.
This is a proposal that aims to improve the ability to generate T cells from induced pluripotent stem cells (iPSCs). The investigators propose a multipronged approach to improve the T cell developmental potential of hematopoietic stem cells (HSCs) derived from embryonic stem cells (ESCs) and iPSCs. Based on the observations from their laboratory that ESC-derived hematopoietic progenitor cells (HPCs) do not efficiently undergo T cell development, the investigators hypothesize that epigenetic changes associated with the origin cell influence the potentiality of iPSC and that the use of hematopoietic cells as the source for iPSC generation will lead to improved hematopoietic potential. Successful T cell development will be essential to the success of using HPCs derived from pluripotent stem cells (PSC) for any therapeutic application, and this proposal represents an attempt to overcome this bottleneck. Reviewers were generally enthusiastic about the concept and the potential impact of the proposed research. The proposal addresses an important need, as T cell development is often poor in adults receiving hematopoietic stem cell transplantation for hematologic malignancies, resulting in a high incidence of infection. The ability to use iPSCs as a source of T cell progenitors would allow the use of autologous T cells for improving immune reconstitution, treating tumors, and potentially generating regulatory cells to treat autoimmune diseases. Enthusiasm for the proposal was dampened, however, by a lack of proposed methods that seem likely to enhance T cell lymphopoiesis above that achieved with marrow- or mobilized peripheral blood-derived HSCs. Reviewers felt that a fundamental problem of poor lymphopoiesis in cancer or autoimmune disease patients is related to thymic function, and this study is not designed to address this bottleneck. The applicant did not propose methods to generate T cells from progenitors in vitro or enhance thymic homing potential. Instead, efforts are limited to an attempt at efficiently generating hematopoietic stem cells and T cell progenitors. Without demonstration of improved T cell generation ability, the rationale for using iPSC rather than autologous adult HSCs is weak. The stated milestones are generally reasonable, but the proposed timelines are particularly aggressive. Reviewers praised the system for single cell ES determination as well designed and thought it highly probable that the system could yield compounds that promote hematopoietic differentiation. The reviewers felt that, although the second aim, generation of iPSC with optimal hematopoietic differentiation potential, is based on a scientifically intriguing hypothesis, adequate preliminary data or literature support for the proposed approach is lacking. Since iPSCs produced from the cord blood cells may contain alloreactivity, reviewers thought it would have been desirable to emphasize use of adult HSCs for reprogramming. Cell signaling and transcription network studies outlined in the proposal were considered important and well designed, but they constitute basic studies that are unlikely to have immediate impact on the translational research. Finally, the review panel believed the proposal should have devoted more consideration for the issues relating to GMP-clinical reagents and media. The PI is a leader in this field and well qualified. The research team was judged to be excellent, and the research environment judged outstanding. Reviewers, however, believed the budget to be excessive considering the proposed scope of the work. The cost of supplies was judged to be high. Another reviewer considered the number of FTEs and consultants involved in this study to be an unnecessarily high number. Finally, concern was raised over possible overlap with an existing CIRM grant. Overall, the studies could eventually have a high impact, and the proposed science is intriguing. However, reviewers were uncertain on the rationale for some of the experimental design and approaches and had concerns about the project’s translational potential.