Basic Biology III
Human embryonic stem cells (hESCs) have important potential in the treatment of human disease. Because they can change into a large number of different cell types, they may be useful in restoring a variety of damaged tissues. One potentially harmful side effect of hESC therapy is cancer due to unregulated growth of the hESCs introduced in the body. hESCs have the potential to grow almost indefinitely. Therefore if they should become "transformed" into cancer cells while being cultured in the laboratory, they may cause cancer in the individuals into which they are injected. Transformation of normal cells into cancer cells can occur through changes in their DNA, which contains the information telling cells to grow or not to grow. Because multiple changes must occur for cells to begin the unchecked growth of cancer cells, the likelihood of cancer is low. However, some cellular changes can increase the rate at which subsequent changes occur, which greatly increases the probability that a cell will acquire all of the changes necessary to become a cancer cell. This increased rate of changes in DNA is called genomic instability, which is proposed to be an early step in many cancers. One mechanism by which genomic instability can occur is through the loss of the caps that protect the ends of chromosomes that contain the DNA. Loss of these caps, called telomeres, can make the DNA highly unstable. This proposal will study whether the loss of telomeres is a cause of instability in hESCs during their growth in the laboratory. Information on this process will allow steps to be taken to avoid this potential harmful effect during hESC therapy.
Statement of Benefit to California:
Human embryonic stem cells (hESCs) have important potential in the treatment of human disease. Because they can change into a large number of different cell types, they may be useful in restoring a variety of damaged tissues. This study will investigate a potentially harmful side-effect involving genetic changes that may occur during growth of hESCs in the laboratory that could lead to cancer when they are introduced into people. Understanding how culture conditions can influence genetic changes in hESCs will allow scientists to avoid these changes and limit the likelihood of complications resulting from hESC therapy.
Project Synopsis: The goal of this proposal is to investigate how culture conditions influence telomere loss and chromosomal instability in human embryonic stem cells (hESC), and to determine whether telomere loss in hESC can lead to cancer. To achieve these ends, the applicant has proposed two specific aims. First, a set of established tools will be applied towards characterizing the effects of various culture parameters and cell stress on telomere length, stability, and activity. Second, the applicant will assess how telomere loss affects chromosome behavior in hESC and whether such changes lead to the formation of malignant teratocarcinomas. Significance and Innovation: - The proposed research seeks to define the relationship between culture conditions and genomic instability, a question of fundamental importance for understanding the cancer risks associated with use of hESC in regenerative medicine. If successful, the project may yield insights towards eventually mitigating some of these risks, although no strategies are presented in the proposal to alleviate these barriers. - The project makes use of clever tools and techniques for studying telomere loss and chromosomal behavior. However, the overall level of innovation is minimal, as these same studies have been performed in murine embryonic stem cells (mESC) and human cancer cells. Feasibility and Experimental Design: - A strong body of prior work supports the feasibility of the proposed approaches and the capabilities of the applicant team, although there were no preliminary data provided to document their ability to clone hESC and detect spontaneous telomere loss and chromosomal rearrangements in those cells. - The research plan is logical and achievable but would have benefitted from a clearer presentation of the underlying rationale. For example, why are the specific culture conditions expected to impact on telomere loss? - Reasonable pitfalls and alternative strategies have been considered. - Certain experimental details were inadequately described, particularly with respect to controls and data analysis methods to be employed. For example, it is not clear how many hESC lines would need to be assayed before findings could be generalized. From a practical standpoint, it is unclear how selection against differentiated cells with silenced telomere reporter gene might impact the number of hESC with telomere loss that could be reasonably assessed. Principal Investigator (PI) and Research Team: - The principal investigator (PI) has an excellent track record of productivity in telomere research and is well qualified to direct this project. - The research team is fairly junior but appears well suited to carry out the proposed research. No concerns were raised about budget, resources or environment. Responsiveness to the RFA: - The proposed study addresses fundamental molecular mechanisms relating to the nature and consequences of genetic instability in hESC, and is thus responsive to the RFA.