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RL1-00657-1: Creating the next generation of human iPS cells with global screens for and use of novel pluripotency factors

Recommendation: Not recommended for funding

Public Abstract (provided by applicant)

The recent discovery of a method to turn non-stem cells into stem cells represents a major leap forward for stem cell based regenerative medicine. These new stem cells, termed induced pluripotent stem (iPS) cells, open doors to new, patient specific stem cell therapies in the future. In theory skin cells from any patient—for example those with Alzheimer’s or Parkinson’s diseases as well as cardiac, liver or spinal cord injury—could be isolated and turned into iPS cells, then given back to the patient as a therapy. However, two major hurdles stand in our way for the use of these cells: safety and efficiency of generation. At this time, these exciting new stem cells cannot be used due to risk of the transplanted iPS cells giving the patient cancer and current methods are very inefficient as well, likely to most often fail in patients. Our goal is to solve these problems with innovative new approaches to making human iPS cells. In order to develop these methods we must identify new genes that can give the process a boost and also find substitutes for some of the currently used genes, particularly Myc, which is one of the most common genes mutated in human cancer. This one gene paradoxically is also required for strong efficiency of iPS generation. Here we propose to discover new pluripotency and self-renewal modifiers via unbiased, global screening methods. We will also tackle the complex role of Myc in iPS formation, with the objective of finding ways to replace Myc or finding a lower level of Myc that eliminates the cancer causing ability of iPS cells, while retaining or replacing its positive role in the process. If the aims of this proposal are achieved, we will have made several key contributions. We will have generated new iPS cells lines available to the stem cell field for further study with distinct and improved properties compared to existing iPS cells. We will have identified novel inducers as well as suppressors of iPS formation using unbiased global screens. The use and manipulation of these new regulators may play key roles in improved iPS protocols, paving the way for the production of yet additional new and further improved iPS lines. The goal of discovering iPS suppressors is a very innovative but logical approach. This novel strategy may pave the way to safer, non-genetic ways of efficiently inducing pluripotency using pharmacological inhibitors of these iPS cell suppressors such as drugs or growth factors. Finally, we will have also determined how to best deal with Myc’s role in iPS formation, a key step toward safe and efficient iPS methodology. Our overall goal is to produce the next generation of iPS cells that are efficient to make and safe to use. Longer term our goal is to work with our neural (Alzheimer’s disease, Parkinson’s disease, and spinal cord injury), cardiac, and liver disease teams to generate safe and effective iPS cells tailored for each patient.

Statement of Benefit to California (provided by applicant)

The proposed studies will provide new induced pluripotent stem (iPS) cell lines and methods for generation of iPS cell lines. Such cells hold great promise for treating patients here in California, benefiting the state both in terms of improving the lives of patients as well as enhancing the knowledge of the stem cell field. It will also further the development of regenerative medicine leading to a new, valuable biotechnology. California should be a leader in developing safe, effective regenerative medicine.

Review

This proposal is focused on the development of improved procedures for the generation of induced pluripotent stem (iPS) cells. The first objective is to eliminate or reduce the risk of tumor formation by iPS cells. This will be addressed by screening cDNA libraries to identify genes whose expression could replace Myc, a known oncogene, in the iPS induction process. The second goal of the project is to overcome the low efficiency of existing procedures for iPS cell derivation. RNA interference screens will identify genes whose suppression leads to pluripotent stem cell induction and support of self-renewal. In an alternative approach, cells with conditional Myc expression will be analyzed for improved induction efficiency and reduced tumorigenicity.

The stated goal of improved clinical safety and efficiency in the generation of iPS cells is significant and important for the field. The approach appears innovative and likely to add new insights into the biology of pluripotent cells. However, reviewers had strong reservations about the project’s potential to improve iPS procedures and yield clinically useful cell lines. A particular concern was the use of integrating vectors which will create a problem for the subsequent clinical application of the derived cells. In addition, some of the suggested candidate genes selected to be targeted for suppression in the proposed studies are known to be tumor suppressors, thus the goal for reduced tumorigenicity of resultant cell lines may not be realized.

The PI is a young researcher with expertise with the Myc gene and decent productivity. The institutional environment and facilities appeared to be excellent. However, the project’s feasibility appears limited. Defined methods for evaluating the pluripotency of the derived cell lines were not presented, and criteria for iPS cell colony selection were not addressed. This was considered to be particularly problematic because the PI has no previous experience in the generation of iPS cells and reviewers stated that the addition of a robust collaboration with an iPS cell expert would have made this a stronger application.

In conclusion, although its goal is to improve procedures for the generation of clinically safe pluripotent cell lines, the experimental design would likely yield cells of questionable value for clinical use. It is unclear that the proposed research would make a major contribution in moving iPS cell generation toward the clinic.

The following Working Group members had a conflict of interest with this application and were therefore recused from participating in review of, discussion of, and voting on the application:

• None