Fetal Stem Cells Cause Tumors in Human Patient: Should Geron ESCR Human Trial License be Reconsidered?
Posted Feb 19 2009 6:05pm
This story is disturbing and raises questions about whether the FDA's license to Geron to conduct human embryonic stem cell experiments should be suspended pending further studies. In Israel, a child treated with fetal stem cells developed tumors four years after receiving fetal stem cell treatments. From the story:
The boy, now 17, received the stem cells in 2001 at a Moscow hospital and four years later scans showed brain and spinal tumours, PLoS Medicine reports. Israeli doctors removed the abnormal growth from his spine and tests suggest it sprouted from the stem cells...
The boy in question was treated for a condition called Ataxia Telangiectasia--a genetic disease that attacks the brain region controlling movement and speech. He received three courses of foetal stem cell injections to the brain and the fluid surrounding the spine. Four years after his first injection he was investigated for recurrent headaches and his doctors at the Sheba Medical Centre in Tel Aviv found two tumours--one in the spine and one in the brain at the same sites the injections had been given.
A year later, when the boy was 14, the doctors removed the non-cancerous tumour from his spine and it was found to contain cells that could not have arisen from the patient's own tissue and had in all probability grown from the donated stem cells. Although they were unable to sample the growth in the boy's brain, the scientists believe this probably arose from the injected stem cells too.
It is worth noting that this particular condition impairs the immune system. Nonetheless, a reason embryonic stem cells cause tumors in animal models is their hyper activity,which makes their proliferation hard to control. Adult stem cells don't seem to have this problem. Fetal stem cells are less "youthful"than embryonic, but more than adult, and thus this tumor finding raises renewed questions about using ES cells in humans at the present time--a worry expressed by supporters as well as opponents of ESCR:
They [commenting scientists] say the findings "do not imply that the research in stem cell therapeutics should be abandoned." Nonetheless, they say more work should be done to assess the safety of this therapy.
Which brings us to the Geron license from the FDA. Geron's work with its product has been exclusively with mice, which were not kept alive nearly the four years it took for this patient to develop stem cell-caused tumors. This raises a question of whether, in light of this report, the FDA should revisit its go ahead to Geron to use ES cell-derived cells in human beings,particularly since it might take years to learn whether the product causes tumors.
And while we are on the subject, it is important that the patient-subject consent forms that will be used in these experiments--which have not yet been made public--be carefully reviewed. The paralyzed patients who will participate in Geron's safety trials are full ambulatory at this moment. But these unknown persons will be seriously injured sometime soon. Within a week or two of their injuries, facing potential paralysis from spinal cord injury, they will be approached by Geron to be test subjects, since the product designed for acute cases, not people with long-term paralysis. This will be a very emotional time in which these patients will be in deep emotional distress at the prospect of never walking again. In such an urgent crisis situation, it will be particularly important that all participants be made unequivocally aware of the potential risks, that these adverse events might take years to develop, and indeed, that being the subjects of such potentially risky experiments, that they might have to be monitored for the rest of their lives. Or to put it more succinctly: the consent, when given, must be fully informed.