Genomic instability during culturing of human embryonic stem cells

Funding Type:

Basic Biology III

Grant Number:

RB3-05020

Investigator:

Name:

John Murnane

Institution:

University of California, San Francisco

Type:

Funds Committed:

$1,074,355

Stem Cell Use:

Embryonic Stem Cell

Status:

Active

Public Abstract:

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.

Progress Report:

Year 1

The first year of our CIRM project was highly successful in that we met our goals of establishing the necessary genetically engineered human embryonic stem cells (hESC) clones and assay systems that are required to perform our proposed experiments on how culture conditions in the laboratory can influence the stability of hESCs chromosomes. The hESC clones that we developed will allow us to monitor how culture conditions influence the caps on the ends of chromosomes, called telomeres, which are essential for maintaining the stability of chromosomes. Our earlier studies in mouse embryonic stem (ES) cells and human cancer cells using this same system have shown that telomere loss can result in many of the chromosome rearrangements found to result in cancer. Therefore, having these genetically engineered hESC clones will help to determine culture conditions that prevent telomere loss and cancer by hESCs. We have also devoted a large amount of time adapting various assay systems to monitor how culture conditions influence oxidative stress, telomere loss, chromosome stability, and differentiation of hESCs. This initial phase of our study was very time consuming, because the unique characteristics and culture conditions of hESCs required that each assay system be tailored specifically for hESCs. However, these assay systems are now in hand and we have initiated our studies to monitor the status of these various endpoints periodically during culturing of the hESCs under different conditions in the laboratory. These studies will allow us to determine whether telomere loss and chromosome instability in hESCs can result in chromosome changes leading to cancer, and will provide critical information on how to culture hESCs to avoid specific alterations that could lead to cancer during hESC therapy.

Publications

Front Oncol (2012) Mechanisms of telomere loss and their consequences for chromosome instability. (PubMed: 23061048)

Current RFAs

CIRM funds grants through directed Requests for Applications (RFAs).

Workshop Reports

CIRM holds regular scientific workshops and meetings to update the scientific staff and CIRM grantees about particular areas of stem cell and related research.

Cerebral Palsy Workshop Report [pdf]
Human iPS Cell Banking Workshop [pdf]
SCNT Workshop Report [pdf]