Early Translational I
Pluripotent cells, specifically human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs), have the potential to differentiate into all of the more than 200 cell types in the body. This furnishes the possibility of providing a large supply of cells to replace or repair damaged or malfunctioning tissues within the body, and thereby opening a new and potentially much more efficacious method for treatment of chronic illness such as cardiovascular, diabetic, and neurodegenerative diseases. However, only differentiated cells can be safely transplanted into the human body. Trace amounts of pluripotent cells resident among the differentiated cells can form teratomas, ill-organized and proliferative cell masses, post-transplantion. Currently, methods to prevent and eliminate teratoma formation are not available. As a result, teratoma formation has become a major roadblock to the clinical usage of pluripotent cell derivatives. The proposed research will study the mechanism of teratoma formation, establish risk evaluation methods, and develop and identify antibodies and small molecules to eliminate and prevent teratoma formation. The results of this research will open the gate to move basic stem cell research into viable stem cell based clinical therapies.
Statement of Benefit to California:
The proposed researches target one of the major issues of stem cell based therapy--teratoma formation. This research: 1). will establish risk evaluation methods for teratoma formation; 2). will establish in vitro teratoma formation model which will greatly facilitate studies of its mechanism; 3). develop antibodies and chemicals that can be used to prevent teratoma formation; 4). develop teratoma formation eliminating methods. These works will advance all the pluripotent cell based clinical cell therapies. Results from these works will provide commercializable items which can benefit California citizens' economy and health.
Eliminating the potential for teratoma formation is central to any future cell therapy based on human embryonic stem cell (hESC)-derived products. Even trace amounts of undifferentiated hESC can pose a risk. The applicants address this issue by focusing on the detection and the removal of pluripotent cells from differentiated cell products before transplantation. They propose to utilize microfluidic technology to develop methods for detecting pluripotent cells (Aim1) and for modeling their differentiation and teratoma formation in vitro (Aim2). In order to eliminate pluripotent stem cells from cell preparations, they then propose to develop cytotoxic antibody approaches (Aim3) and to identify apoptotic (death-inducing) small molecules (Aim4) targeted toward undifferentiated hESC. The reviewers supported the attempt to solve an important safety bottleneck for the translation of cell therapies, but were not convinced by the scientific rationale or the proposed efforts. The applicant takes a technology driven approach, centered heavily on microfluidic systems, to identify single pluripotent cells. Therefore, Aims 1 and 2 are focused on detecting and describing pluripotent cells at the single cell level, rather than pursuing a sensitive and specific method for detecting tumorigenic cells in a potential cell therapy product – the key bottleneck. Furthermore, the applicant makes the assumption that undifferentiated pluripotent cells are the only cells in a mixed population that constitute a tumorigenic risk, and the proposed identification of potentially tumorigenic cells relies on the expression of pluripotency markers without adequate validation through in vivo assays. Although there is mention of in vivo teratoma assays, no details are provided, and no funds have been requested for animal work, calling the applicability of the marker analysis into question. Since in vivo teratoma assays are expensive and subjective, reviewers did appreciate the goal of developing a highly sensitive and accurate in vitro model for teratoma formation, but felt that this endeavor was poorly described and still in the early development stage. Similar criticisms of poor rationale, weak experimental design and lack of in vivo validation studies were raised against the goals of Aims 3 and 4, i.e. to design antibody- and small molecule-based teratoma prevention strategies. Overall, the attempt to develop an in vitro safety tool without correlating the findings to in vivo tumor biology studies represents a major flaw of this proposal. In addition, reviewers expressed concern that the preliminary data were not sufficient to suggest a high probability of success. The reviewers felt that the applicant has good research training but lacks the requisite experience to lead a large-scale translational project. The applicant’s role is merely stated as being the “Principal Investigator” and thus does not detail how s/he would ensure progress and ultimate success of the project. The collaborating institutions bring substantial resources to bear and the assembled team members are qualified to perform the proposed work; reviewers expressed particular confidence in the collaborator who brings stem cell and high through put screening expertise to the team. Overall, though, reviewers judged the size of the team to be extremely large and potentially difficult to manage, with some key personnel committed to only very low percent efforts. It thus remains to be shown that the team can work together on focused goals. Reviewers further thought that the budget was excessive and had not been satisfactorily justified. In summary, reviewers felt that the proposed research addressed an important safety bottleneck with implications for translating stem cell research to the clinic. The applicant presented a set of potentially useful technologies but failed to substantiate the feasibility of this effort. As a result, enthusiasm for this proposal was very moderate.