Washington

A compromise answer to the hot political question of whether the US government should fund research on human embryonic stem cells has received a chilly response from cell biologists.

The suggested compromise would allow government funding only for research on existing, privately derived stem-cell lines. Around a dozen such cell lines are thought to exist, half of them in the United States. The compromise was floated in the press by anonymous White House officials.

President George W. Bush is under mounting pressure from both sides of the stem-cell debate as he moves rapidly towards a decision. And with the administration and Republicans in the Congress openly split on the issue (see Nature 411, 979; 2001), he might welcome a compromise.

Compromised: biologists say that using only existing embryonic stem-cell lines will constrain research. Credit: UNIV. WISCONSIN

But many researchers dismiss the value of access only to existing stem-cell lines. James Thomson of the University of Wisconsin, Madison, who first derived stem cells from human embryos (Science 282, 1145–1147; 1998), calls the idea “a bad compromise” that would “in essence satisfy no one”.

“Research just based on the limited number of cell lines available might be biased,” says Rudolf Jaenisch, a professor of biology at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts. “You might miss some important information.” Jaenisch was the senior author on a recent paper (Science 293, 95–97; 2001) showing an undocumented instability in gene expression of mice cloned from embryonic stem cells.

Some researchers concede that federal funding for work on a small number of cell lines would be better than nothing. Irving Weissman, a biologist at Stanford University in California who has worked on mouse embryonic stem cells, says that, for basic developmental-biology studies, a few lines might suffice. “A lot of good research could go on” if the lines are of excellent quality, he says.

But the political usefulness of the compromise is doubted by some observers. “It doesn't make any sense, hold any water, or gain the administration anything ethically or politically,” says Tony Mazzaschi, associate vice-president for research at the Association of American Medical Colleges.

Gene Tarne, a spokesman for the Coalition of Americans for Research Ethics, a lobby group opposed to embryonic stem-cell research, calls the compromise objectionable. “The stem-cell lines are derived from destroying embryos, whether that was yesterday or next week,” he says.

Groups representing cell biologists say that different stem-cell lines vary in their ability to grow and differentiate, and that a dozen or so lines would be too few to promise therapies for many diseases. They also point out that several of the existing lines do not grow well in culture, rendering them impractical for research, and that the cells represent only a very narrow range of genetic variation.

Thomson, who produced five of the existing cell lines, notes that his lines were made for experimental purposes. “It's not clear that they were derived in a way that is appropriate for therapy,” he says.

Another obstacle is that Geron, the California-based biotech firm that funded Thomson's research, holds an exclusive licence for the use of his cell lines in many applications.