12/11/02 News Release

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STANFORD, Calif. ­ The Stanford University School of Medicine is not engaged in human reproductive cloning, contrary to some news reports on Tuesday.

At a news conference Tuesday evening, Irving Weissman, MD, Karel and Avice Beekhuis Professor of Cancer Biology, clarified the nature of the work that will be taking place at the newly formed Institute for Cancer/Stem Cell Biology and Medicine, which Weissman will direct. “We want to be able to understand some of the most devastating genetic diseases in man,” he said.

Weissman said human stem cells are able to divide indefinitely – a quality that cancerous cells also possess but that normal cells do not. They hope that by understanding the details of how stem cells continue dividing they may home in on molecules that go awry in cancer biology.

Philip Pizzo, MD, dean of the medical school, said that cancer is a multi-step process. “By understanding those steps using stem cells, we can identify targets and can develop therapies based on those targets,” he said.

The initial $12-million in seed funding for the institute comes from a private donor. Weissman said the school will continue to recruit new funding for the institute. He said federal funding can also be used for all work in mice and some of the human work, adding that it would be many years in the future before researchers at the institute began to work with human cell lines. “When and if we get to that point we will find out what the current funding guidelines are,” Weissman said. He added that research labs are committed to tracking the use of federal and private funds.

The institute will take a unique approach to studying cancer and other genetic disease. Researchers plan to form human embryonic stem cell lines that carry DNA with disease-causing mutations. By studying how these cell lines grow, divide and respond to such outside influences as drugs the researchers may be better able to understand – and eventually treat – the diseases.

It’s how these new stem cells lines will be produced that caused confusion in the media. Weissman said there are two ways that the new institute might generate these stem cell lines. The first is by transferring a nucleus into the cell of an existing stem cell line, thus generating a new stem cell line with the DNA of interest.

The second way to generate the stem cell lines is through a process called nuclear transfer – also known as therapeutic cloning. In this process, researchers transfer a nucleus to an egg that has had its nucleus removed. That cell divides seven or eight times to form a small cluster of cells called a blastocyst. The researchers then remove cells from the blastocyst. It’s these cells that go on to be the embryonic stem cell line while the developing blastocyst is then destroyed.

Weissman said the institute would choose which approach to use based on initial work in mice. “We want to establish stem cell lines in the best possible way,” he said. Until his group has studied those methods in mice, they won’t know which way will work best in humans.

If the group decides that the best way to generate useful embryonic stem cells lines is by using a human egg, that work would be subject to review and approval by an Institutional Review Board made up of doctors, scientists and bioethicists. “They would analyze risks and benefits and decide if we can go forward,” Weissman said. He also said that the group would go through a review board to approve any approach to getting human eggs, and that the egg donor would have to give consent to the research.

Whether nuclear transfer into a human egg is used, the question remains: Is this cloning? Weissman was clear on one point. “We are unanimously opposed to human reproductive cloning,” he said.

Still, some people consider the process of generating a blastocyst by nuclear transfer to be equivalent to cloning a human embryo. Weissman pointed out that two national scientific panels that reviewed nuclear transfer – one of which Weissman chaired – considered the wording “human embryonic cloning” to be an inaccurate way to describe this procedure. These panels along with all major scientific associations call the procedure “nuclear transplantation to produce human pluripotent stem cell lines.”

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