In May 2001 at the age of 9 years, again in March 2002 and once more in July 2004 at the age of 12 years, a boy was taken by his parents to be treated in a Moscow hospital with a procedure involving a transplant of fetal stem cells into his brain.
The boy suffers from a neurodegenerative hereditary disorder, ataxia telangiectasia (AT). AT is a childhood disease that causes degeneration of those parts of the brain controlling muscle movements and speech. As a result of headaches an MRI was performed in an Israeli hospital in 2005 and a multifocal tumor was found in the boy's brain. Subsequent analysis proved the tumor could not have been generated by the boy's own cells and therefore had to originate with the transplanted stem cells. The following is from the story in TheScientist.com.
"The case study raises a number of questions," said Uri Tabori, a pediatric hematologist and oncologist at the Hospital for Sick Children in Toronto, Canada. "Because the patient's immune system was impaired, it's not yet clear whether the increased risk of cancer is specific to patients with suppressed immune systems, something particular to the procedure done in Moscow, or a danger with neural stem cell transplantation in general, This is a case report. It has its role in saying it can happen, but we don't know if it's common, if it's uncommon."
"However, it's premature to translate these findings to studies conducted in the US," said Aileen Anderson, a neuroscientist who studies stem cells at the University of California, Irvine. "The researchers who conducted the transplant followed the protocol of a group that has published only one other paper in an international, peer-reviewed journal, and the cells used are a mixture of glial cells, neurons, and progenitors -- a sort of cell mush. These are completely uncharacterized populations, populations that would never be accepted in the US or any first-world country."
Stem Cells, Inc., one of our Sector Companies, is in clinical trials to test the safety of a highly purified, expandable population of human neural stem cells. Stem Cells Inc. recently issued a statement regarding the tumor finding in the Russian transplant case. The following is an excerpt:
"Based on the article and references cited therein, StemCells understands that the transplants in the case comprised an uncharacterized and poorly defined mixture of cells from multiple donors. It is unclear what preclinical safety testing was done, if any, on these cells. In contrast, our HuCNS-SC cells comprise a highly purified, well characterized, neural stem cell product that has undergone rigorous preclinical safety testing, including testing for tumorigenic potential. To date, there has been no evidence of abnormal cell growth in several thousand test animals. In addition, our HuCNS-SC cells entered a Phase I clinical trial in 2006 under an IND authorized by the FDA and StemCells has been able to compile and analyze over two years of extensive human safety data. There has been no evidence of abnormal cell growth in any of the patients in this recently completed clinical trial, the transplantations have been well-tolerated and there have been no significant safety or toxicity concerns."
While the evidence suggests that the proper care was not taken to prepare the stem cells used in the Russian transplant, the event nevertheless suggests the degree of care that must be taken to insure the highest possible safety for clinical tests involving embryonic stem cells.