In recent days, the media have left unchallenged Senate Majority Leader Bill Frist's (R-TN) July 29 announcement of support for expanding federal funding for embryonic stem cell research beyond the restrictions currently imposed by the Bush administration, even though the justifications Frist provided for shifting his position have been publicly known for years. Some reports failed to even track the evolution of Frist's views, such as an August 1 report by USA Today that did not note Frist's public opposition to expanding stem cell research as recently as June, and an August 1 article in The Wall Street Journal that neglected to mention that Frist's position had ever changed.

Frist had reaffirmed his opposition to expanding federal funding for embryonic stem cell research less than a month before declaring his support for the Stem Cell Research Enhancement Act. That bill, passed by the House of Representatives in May, would undo President Bush's restrictions against federal funding for stem cell lines derived from excess embryos produced after 2001. As the Associated Press reported on June 30, Frist had said that research that "[stops] short of destruction of an embryo for experimental purposes" is the “direction I think we should explore.” Frist voiced even more direct support for Bush's policy two weeks earlier, during a June 15 press conference:

FRIST: The question is whether I believe the president's [stem cell] policy should be expanded. I do not at this juncture believe it should be expanded. The president has drawn a bright line. He believes that the human embryo, which is living, which is biologically human, which is genetically distinct, should not be destroyed for experimental purposes.

I think it is time to look at the science, how has the science progressed since that policy was put in place, but I agree with that ethical guideline.

But on July 29, Frist claimed that he had changed his position on restricting funding for embryonic stem cell research. The principal reason he gave for the change was that it had become increasingly apparent that there is a smaller number of stem cell lines available for federally funded research than first thought. He emphasized that Bush's policy should be “modified” because “unexpectedly, after several generations” the cell lines have become “less stable and less replicative,” and the existing federally funded cell lines are “also grown on mouse feeder cells, which we have learned since will likely limit their future potential for clinical therapy in humans.”

From Frist's speech on the Senate floor:

Now, when the president announced his policy four years ago, it was widely believed, and stated again and again, that there would be 78 embryonic stem cell lines available for federal funding.

This has proven not to be the case. Today, only 22 lines are eligible. Moreover, those lines, unexpectedly, after several generations, are starting to become less stable and less replicative than initially thought. They're acquiring and losing chromosomes. They're losing what is called the normal carrier type and are potentially losing growth control.

They're also grown on mouse feeder cells, which we have learned since will likely limit their future potential for clinical therapy in humans. And in part that's because of the potential for viral contamination or retroviral contamination.

While human embryonic stem cell research is still at a very, very early stage, the limitations that were put in place in 2001 will over time slow our ability to bring potential new treatments for certain diseases.

Therefore, I believe the president's policy should be modified. We should expand federal funding and the accompanying NIH oversight and current guidelines governing stem cell research, carefully and thoughtfully staying within ethical bounds.

Major news outlets have largely failed to challenge Frist's purported reasons for now supporting the bill. For example, while Frist noted that “Today, only 22 lines are eligible,” this number has been publicly known since at least August 24, 2004, when it was reported by The New York Times. Similarly, Frist described the findings regarding problems with the existing stem cell lines as “unexpected” and said those findings differed from what was “initially thought.” In fact, stem cell experts have voiced those concerns for years.

The Washington Post reported on August 12, 2001, that, according to Harvard University researcher Douglas A. Melton "[human embryonic stem cells'] properties will degrade with time. Everyone is fearful that the more you grow them in the dish, the more they lose their properties." The Chicago Tribune reported a similar assessment by Princeton University president Shirley Tilghman, a professor of molecular biology, on August 10, 2001: “We know from many years of experience working with mouse embryonic stem cells that these lines have a limited life span--that although they can reproduce for many generations in culture, they eventually will become less useful even under the best of circumstances.”

A January 2004 report by the President's Council on Bioethics included “mutation during DNA replication” and “chromosome changes” among the “numerous challenges to obtaining and preserving the uniform and stable preparations of stem cells necessary for reliable research and, eventually, for safe and effective possible therapies.” Further, an August 13, 2004, report on stem cell research by the Congressional Research Service (CRS) noted that scientists question the “quality, longevity, and availability” of the outdated stem cell lines currently eligible for federal funding, noting that lines “developed in the early days of human stem cell research using older 1990s techniques ... are harder to work with, not well characterized, and somewhat unstable.”

The CRS report also detailed scientists' concerns about the use of nonhuman -- in this case mouse -- cells for “transplantation, implantation, or infusion into a human recipient.” The problems associated with the use of mouse feeder cells -- which were used for all the federally funded stem cell lines -- have been widely reported; Sen. John Kerry (D-MA) even mentioned that the cell lines were “contaminated by mouse cells” in a 2004 presidential debate. In 2003, a John Hopkins University medical ethics panel determined that treating human patients with the available stem cell lines would be unethical and risky. According to the panel's press release: “Ethically and scientifically, potentially exposing study participants to a mouse virus -- which people's immune systems might be unable to combat -- is not a risk worth taking in the face of safer alternatives, the panel unanimously agreed.”

Finally, some media reported on Frist's announcement without even noting that it represented a significant -- and recent -- change in position. For example, an August 1 report by The Wall Street Journal failed to mention that Frist previously supported Bush's August 9, 2001, decision to ban federal funding for any stem cell lines derived from excess embryos produced after that date, while both the Journal and an August 1 USA Today article failed to report that Frist reaffirmed that position as recently as June 2005.