Basic Biology III
Stem cell therapies have the potential to result in entirely new treatments for a vast variety of currently incurable diseases. The goal of these therapies is to regenerate lost cells or tissues through the use of established human embryonic stem cell lines or even from the patient's own cells. One major limitation of current stem cell therapy approaches is that they may give rise to cancer. Embryonic stem cells have a limitless potential to reproduce and if they remain in a undifferentiated state could give rise to tumors. This proposal seeks to make stem cell therapies safer by using two novel targets that can selectively kill undifferentiated stem cells while sparing differentiated cells or normal cells. We propose to use small molecule inhibitors of the cell cycle and inhibitors of specific small RNAs to kill embryonic stem cells that have remained in an undifferentiated state. If validated, these therapeutic approaches could be developed to make stem cell therapies safer and hasten stem cell based therapies to the clinic.
Statement of Benefit to California:
The State of California is committed to developing new approaches to treat currently incurable diseases through the application of stem cell biology technologies. While there is much excitement about the prospects for these new treatments, there is also potential concern, that current strategies may also increase the risk of developing cancer. This proposal seeks to use new strategies to block the growth of embryonic stem cells that pose the risk of developing into cancer. It is hoped that such approaches will make stem cell-based therapies safer for us all. Development of such approaches would be expected to advance the field of stem cell biology and speed delivery of new and safer treatments to the clinic.
Project Synopsis: The goal of this project is to develop methods to selectively eliminate undifferentiated human pluripotent stem cells (hPSC) that might persist after therapeutic implantation of hPSC-derived differentiated cell populations. The depletion of such cells is important for cellular therapy, since persistent hPSC could give rise to cancers. The specific aims are focused on two distinct approaches for killing undifferentiated hPSC. The first aim investigates hPSC killing by interfering with cell cycle pathways and the second aim focuses on killing hPSC by inhibiting the function of specific microRNAs. Significance and Innovation: - The elimination of hPSC from therapeutic cell populations was recognized as an important and major unsolved problem. If successful, the project would impact the potential applications of stem cell research to regenerative medicine. - Reviewers found the project’s approach in targeting cell cycle pathways and microRNAs to be innovative and logical. - The use of a candidate-based strategy for proposed knockdown studies (rather than a screen) will likely uncover already well-established regulators of cell death and therefore the extent of new mechanistic insight provided by these studies may be limited. Feasibility and Experimental Design: - The experimental approach was supported by significant and clearly presented preliminary data, obtained primarily from mouse studies. - Reviewer enthusiasm was lessened by a number of deficiencies in the experimental design and the absence of adequate detail in descriptions of proposed experiments. For example, due to the numerous conditions that will be tested, the proposal would have benefitted from details regarding the expected frequency of teratoma formation, how teratoma frequency might change as a consequence of the experimental conditions, and how long it will take to determine if there are differences in teratoma risk. Power calculations based on the above are needed to determine how many mice must be included in each experimental group. - Reviewers expressed concerns that the targets chosen for selective killing of hPSCs might be ineffective. In the case of the first aim, preliminary data indicate that as desired, differentiated cells remain viable after treatment with a cell cycle inhibitor, but so do 50% of hPSC. If this strategy is to be effective as a safety tool, the killing of hPSC will need to be almost complete. In the case of the second aim, the chosen miRNAs may not be specific to hPSC. Principal Investigator (PI) and Research Team: - The PI is well trained with experience in studying cell survival pathways. -The PI has a considerable record of achievement with several excellent publications and a track record for funding. However, he/she is senior (supervising) author on only one recent publication. - Collaborators are experienced, appropriate, and add strength to the proposal. Responsiveness to the RFA: - Although the focus on method development appears to be out-of-scope, experiments addressing mechanisms regulating viability of hPSC highlight the project’s responsiveness. - The project should provide new insights into basic cellular processes in hPSC.
- This application scored below the initial scientific merit funding line, no programmatic reason to fund the application was proposed, and the GWG voted to place the application in Tier 3, Not Recommended for Funding.