Letter to the president cites recent research making new uncontaminated lines possible
April 25, 2003
By Ted Agres
Citing recent research advances, Sen. Arlen Specter (R-Penn.) and other senators are urging President Bush to expand eligibility requirements for federal funding of human embryonic stem cells (HESC).
"With the discovery of a way to grow human stem cells without mouse cells, it is possible to use new stem cell lines that have never been exposed to mouse cells and are safe for use in humans," Specter wrote in an April 21 letter to the president.
Under existing policy, federal funds for HESC research are available only for a limited number of cell lines established before August 9, 2001. Of some 78 stem cell lines initially identified as meeting the eligibility criteria, only 11 lines are presently available for researchers, Specter noted. Many scientists and politicians have argued that this number inhibits meaningful research. And because the currently qualified stem cell lines have been grown using mouse feeder cells, there is the potential for mouse viruses and other contaminating proteins to be passed to human cells, making potential clinical trials risky and difficult to conduct.
However, in the March issue of Stem Cells, Linzhao Cheng, an oncology professor at the Johns Hopkins University School of Medicine in Baltimore, and his colleagues describe growing HESC using a culture of adult human bone marrow cells. This method "may provide a clinically and ethically feasible method to expand HESC for novel cell therapies," they concluded.
Last September, Mark Richards and other researchers at the National University of Singapore reported use of human fetal and adult fibroblast feeders to support prolonged growth of existing HESC in Nature Biotechnology.
"These recent developments underscore the need to expand your August 9, 2001 policy so that doctors and scientists can use these new safer stem cell lines and realize the promise of stem cell research to cure diseases," Specter wrote to Bush.
Specter is chairman of the Senate Appropriations Subcommittee on Labor, Health and Human Services, and Education and has been a prominent research supporter. He, Sen. Tom Harkin (D-Iowa), and Sen. Orrin Hatch (R-Utah) hope to hold hearings next month on the matter.
The three are among senators who have sponsored legislation to permit research cloning to develop therapies (S 303). In February, the House passed a bill prohibiting cloning for any purpose, including for research (HR 534). Companion legislation (S 245) has been introduced by Sen. Sam Brownback (R-Kan.). Neither Senate bill has been acted upon.
Specter's letter demonstrates that "we're beginning to see some political pressure based on what scientists had predicted all along — that the president's policy of August 2001 is inadequate to move the research forward," said Sean Tipton, spokesman for the Coalition for the Advancement of Medical Research (CAMR), an advocacy group for stem cell research and somatic cell nuclear transfer.
But Jim Battey, director of the stem cell task force at the National Institutes of Health (NIH), said there is no need to change the administration's funding policy because more basic research is needed before any clinical trials can begin. "I think we're years away from any clinical trials involving cells derived from HESC," he told The Scientist. "There's just too much basic biology that we'll need to understand to do these clinical studies safely and carefully."
Some of the basic issues include directing differentiation toward specific cell types, controlling cell proliferation after transplantation, and insuring proper cell functioning and immune response survival, said Battey. "These are basic science questions that can be as easily addressed with cells that are grown on mouse feeder layers as the cells that are grown on human feeder layers."
Additionally, NIH is supporting research that would make existing, federally
available cell lines in a completely "feeder-free" medium. "In the long
run, that is the best thing to do in terms of culturing cells that ultimately
will be used in clinical trials," Battey said. "The last thing the stem
cell research field needs is to have a disaster because somebody proceeded
too fast without enough available basic information."
Copyright © 2003, The Scientist Inc.