Scientists may be growing impatient, but President Obama has been rightly taking his time in addressing a campaign promise to lift the ban on federal funding for research using new lines of stem cells to be taken from human embryos. Even for strong backers of embryonic stem cell research, the decision is no longer as self-evident as it was, because there is markedly diminished need for expanding these cell lines for either patient therapy or basic research. In fact, during the first six weeks of Obama’s term, several events reinforced the notion that embryonic stem cells, once thought to hold the cure for Alzheimer’s, Parkinson’s, and diabetes, are obsolete. The most sobering: a report from Israel published in PLoS Medicine in late February that shows embryonic stem cells injected into patients can cause disabling if not deadly tumors.
The report describes a young boy with a fatal neuromuscular disease called ataxia telangiectasia, who was treated with embryonic stem cells. Within four years, he developed headaches and was found to have multiple tumors in his brain and spinal cord that genetically matched the female embryos used in his therapy.
His experience is neither an anomaly nor a surprise, but one feared by many scientists. These still-mysterious cell creations have been removed from the highly ordered environment of a fast-growing embryo, after all. Though they are tamed in a petri dish to be disciplined, mature cells, research in animals has shown repeatedly that sometimes the injected cells run wildly out of control—dashing hopes of tiny, human embryos benignly spinning off stem cells to save grown-ups, without risk or concern.
That dream was still alive only a few weeks before this report. Within days of Obama’s inauguration, the Food and Drug Administration approved its first-ever embryonic stem cell study in humans: the biotech company Geron’s plan to inject highly purified human embryonic cells into eight to 10 patients with acute spinal cord injuries. (The cells are from a stem cell line approved by Bush because it predated his ban.) The FDA should now be compelled to take another look: Are eight to 10 patients enough, or one year of monitoring sufficient, to assess safety? And doctors who participate in the trial will have to ask what every doctor must ask before performing research on a human subject: Were I this patient, would I participate? Would I encourage my loved ones to do so?
Even as the future of embryonic stem cells has dimmed, adult stem cell research has scored major wins evident just in the past few months. These advances involve human stem cells that are not derived from human embryos. In fact, adult stem cells, which occur in small quantities in organs throughout the body for natural growth and repair, have become stars despite great skepticism early on. Though this is a more difficult task, scientists have learned to coax them to mature into many cell types, like brain and heart cells, in the laboratory. (Such stem cells can be removed almost as easily as drawing a unit of blood, and they have been used successfully for years in bone marrow transplants.)
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