Bush rejects second stem cell bill; veto override is unlikely

Washington -- Congressional backers of embryonic stem cell research continue to pressure President Bush on the issue, despite the lack of a veto-proof majority in Congress.

Bush vetoed the Stem Cell Enhancement Act of 2007 on June 20. The bill would have ended his ban on using federal funding for research on new human embryonic stem cell lines, in place since Aug. 9, 2001.

One day after the veto, a Senate committee approved a Dept. of Health and Human Services 2008 spending bill 26-3 with language allowing federal funding for research on stem cell lines derived before June 15, 2007. The language was inserted by Sen. Tom Harkin (D, Iowa), who said in a statement there is "no substitute for this type of research."

However, advances of the last couple of years are changing the debate over the ban on federal support of human embryonic stem cell research. These advances -- such as reprogramming adult cells into pluripotent form -- are allowing Bush and other opponents of research that destroys human embryos to argue that science may one day allow scientists to bypass this thorny moral issue.

Bush issued an executive order, also on June 20, instructing the HHS secretary to develop a plan to support research using alternative methods of deriving pluripotent stem cell lines. "Destroying human life in the hopes of saving human life is not ethical -- and it is not the only option before us," Bush said.

However, maintaining a ban on federal funding of human embryonic stem cell research while endorsing other, less-established methods of stem cell research isn't allowing scientists to do all the work they could, according to Leo Furcht, MD, president of the Federation of American Societies for Experimental Biology. "We've been, frankly, as a country, hindered by the policies of the White House," Dr. Furcht said.

A veto override is unlikely. Although 66 senators support legislation ending Bush's ban -- one short of overriding a veto -- the House needs at least 35 more votes to reach the two-thirds majority. No one expects that many representatives to change their votes, said a spokesperson for Rep. Mike Castle (R, Del.), who has championed legislation to end the stem cell funding ban.

More than one way to get a stem cell

The new Bush policy is rooted in a few recent advances in changing cells from their adult, or somatic, form to their earlier pluripotent state, from which a variety of cells can develop. The ultimate goal of such research is to be able to grow healthy tissue to replace tissue that doesn't work, such as neurons in people with disabilities or the insulin-producing cells in the pancreases of people with diabetes.

Perhaps the most significant recent development in nonembryonic stem cell research was announced last month when a team at the Whitehead Institute for Biomedical Research in Cambridge, Mass., said it had reprogrammed adult mice skin cells back to pluripotent form, identical to embryonic stem cells and then grew a mouse from those cells.

One of the members of that team, Marius Wernig, MD, a postdoctoral fellow at the institute, cautioned that the method is crude and not yet applicable to humans.

The team changed the skin cells by inserting four genes, two of which were oncogenes. "You don't really want to have a cell in your brain which carries an oncogene," he said. The work's significance is showing that such reprogramming is possible.

Other newer methods of deriving pluripotent stem cells are:

• Altered nuclear transfer, in which the nucleus is genetically modified so that when placed in a new egg it would produce stem cells but could not produce an embryo.
• Taking of healthy live cells from "naturally dead" embryos that are no longer developing, much in the way organs can be harvested from the recently deceased.
• Taking of a cell from a morula, an eight-celled embryo, and altering it to develop stem cells, although this raises moral concerns for some because of potential harm to the embryo.

Still, understanding embryonic cells is going to be important, even to those using newer methods of deriving stem cells, as human stem cell research progresses, Dr. Wernig said.

AMA policy encourages public support for federal funding of research on embryonic stem cells, among other types of pluripotent cells.

Public opinion

A poll of American scientists would likely reveal that a significant number, if not a majority, support human embryonic stem cell research, scientists said. However, a member of the president's Council on Bioethics cautioned that many researchers have moral concerns about working with human embryos.

"A great many people object to this. It's not just religious people," said William Hurlbut, MD, a consulting professor of neuroscience at Stanford University. "The truth is that the country is very deeply divided."

Public support of embryonic stem cell research depends on how the question is phrased in polls. If the question mentions curing diseases, up to 70% of Americans support the research. If it mentions the destruction of human embryos, support drops to just below 50%, said Daniel W. Foster, MD, professor of internal medicine at the University of Texas Southwestern Medical Center in Dallas and also a member of the president's council.

In the absence of alternative methods of stem cell research, the political grounds will shift the day a scientist creates a therapy for a disease with human embryonic stem cells, said Donald W. Landry, MD, PhD, interim chair of the department of medicine at Columbia University in New York. It's difficult for politicians to know what's going on in stem cell research. "If they're not really sure, they may tend to err on the side of not destroying embryos. If they think they can actually save a child and they think they're really unsure, they'll go with saving the child," he said.

Meanwhile, it's difficult to argue against scientists pursuing alternative forms of deriving stem cells, Dr. Foster said. But it also doesn't make sense to allow the 900,000 or so frozen embryos in fertility clinics to die, he said.