Fetal stem cell injections have caused benign brain tumours

Neural fetal stem cell injections, administered to a boy in Russia in an attempt to treat a rare genetic condition, have caused benign brain tumours to grow. This is the first documented example of such a complication in a human, although there have been reports of tumours developing in rodents following similar procedures. Researchers from the Sheba Medical Center in Tel Aviv, Israel, have published the case in the journal PLoS Medicine.

The unnamed Israeli boy has the rare neurodegenerative disease Ataxia Telangiectasia (AT), which affects areas of the brain that control speech and muscle movement. Symptoms include slurred speech, an impaired immune system, and poor balance. Patients are usually wheelchair-bound and have a short life expectancy, typically only living to their late teens or early twenties.

Trials of therapeutic stem cell transplantation are carefully regulated in many countries, including the UK, but to a far lesser degree in countries such as Russia and China. This could explain the decision of the boy's parents to seek out such a highly experimental treatment for his condition in Moscow. The boy received injections of fetal neural stem cells into various regions of his brain and spinal cord at the ages of 9, 10 and 12, presumably with the hope that the injected cells would slow his disease's progression, or perhaps restore some function to his brain.

It is not clear whether the injections aided his condition at all but by age 13 he was admitted to the Sheba Medical Center complaining of recurrent headaches. An examination discovered two non-cancerous tumours located at injection sites in the spine and brain. The spinal cord tumour was surgically removed the following year, and analysis showed that it could not have arisen from the patient's own tissues and must have come from at least two different fetuses. It contained both XX (female) and XY (male) cells and had two normal copies of the ATM gene (that causes AT when mutated in a patient). Although the growth in the brain could not be sampled it seems probable that it was also a result of the stem cell injections.

Stem cell transplantation is widely considered to have great potential as a possible future treatment for a plethora of serious diseases and injuries. But one major concern has always been that the stem cells may give rise to tumours as, by their very nature, they have a tendency to proliferate and differentiate into other specialised cell types. However, the fact that AT often results in a weakened immune system may be a mitigating factor in these findings, warns the research team leader Gideon Rechavi.