Special to The Interim

Human embryonic stem cells have long been known to be unstable and difficult to control. In some cases, where they have been used directly in therapeutic trials, the use of embryonic stem cells has been disastrous for patients. Now, a researcher from Johns Hopkins University, an institution that has backed the use of embryos for research, has found that embryonic stem cells cultured in the lab accumulate genetic changes that may be linked to cancer.

Like a genetic game of “telephone,” the longer the cells are cultivated, the more the genetic errors grow. Says Dr. Aravinda Chakravarti, a geneticist at the Institute of Genetic Medicine of Johns Hopkins University in a report in the journal Nature Genetics, “These mutations we are finding are a much bigger problem.”

Chakravarti’s research team found that, as they were cultured, stem cell lines went through 35 cell divisions and that 90 per cent showed changes in patterns of methylation -– the process in which certain genes in a cell are turned on or off – 22 per cent had mutations in mitochondrial DNA and 50 per cent had major deletions or amplifications in the DNA. Moreover, it was the connection between the particular genetic problems the cells developed and the formation of tumours that was most worrying.

Chakravarti said that if it turns out these cells really do become unstable over time, “then that would put limits on the practical life spans of the cells and their usefulness for therapeutic purposes.”

Chakravarti told the New Scientist that a possible solution would be to use the cells only when they are new and before extensive cultivation and division. However, the use of embryonic stem cells for disease treatment depends upon a long process of cultivation and differentiation into particular tissue types. Chakravarti’s discovery may end any lingering hopes of using embryo stem cells directly in therapeutic applications.

This discovery of the degradation of the genome of cultured stem cells comes at the same time a member of the U.K.’s House of Lords has decried the hype surrounding embryonic stem cells. The news media and certain factions in the scientific community have long promised that the use of cells derived from embryos and aborted fetuses will cure diseases, usually  identified as Parkinson’s, Alzheimer’s and diabetes. Meanwhile, all the news regarding real cures and treatments for these and other serious diseases from adult stem cells goes largely unreported.

Speaking on the eve of this year’s British Association Festival of Science, and saying that the business of science is not one of certainty but rather uncertainty, one of the U.K.’s leading fertility experts and a supporter of embryo research, Lord Robert Winston, said, “I think we need to be considerably more modest about our science. We do tend to hype up so many activities. The latest one in biology is the issue of embryonic stem cells. I view the current wave of optimism about embryonic stem cells with growing suspicion.”

Lord Winston pointed out, at nearly the same moment as the discovery at Johns Hopkins, that one of the biggest problems with embryonic stem cells was the fact that “cultured stem cells are inherently unstable. When grown in the laboratory, they often produced cells with chromosomal abnormalities.”

This story originally appeared Sept. 6, at  and is reprinted with permission.