WASHINGTON: A US stem cell expert who lent his name and credibility to South Korean cloning pioneers asked that his name be removed from their landmark scientific paper on Tuesday and questioned whether the work had been falsified.

Dr Gerald Schatten of the University of Pittsburgh asked the journal Science to take his name off a human cloning study published by Woo Suk Hwang and colleagues at Seoul National University in May 2005.

Hwang and colleagues made history in 2004 when they reported they had cloned the first human embryo not to make a baby, but to derive embryonic stem cells for scientific and medical research.

In May 2005 they reported they had cloned cells from people with diseases, to make batches of cells useful for studying those diseases. And in August they cloned the first dog, Snuppy.

The accomplishments put Hwang and South Korea at the forefront of cloning and stem cell research at a time when US politics and a debate over the ethics of cloning humans are limiting efforts.

"My careful re-evaluations of published figures and tables, along with new problematic information, now casts substantial doubts about the paper's accuracy," Schatten said in a letter to Science.

"Over the weekend, I received allegations from someone involved with the experiments that certain elements of the report may be fabricated."

Science said it was declining to remove Schatten's name from the paper. "There is no method for retracting authorship," Science said in a statement.

"As of this writing, Science is not aware of any scientists claiming that the data are fraudulent."

But Dr Robert Lanza of Massachusetts-based Advanced Cell Technology, who is also trying to clone human embryos, said he had doubts. "Why are the Koreans refusing to have their samples retested? This doesn't smell right," Lanza said.

Lanza signed a letter to Science along with other cloning researchers, including the scientists who cloned Dolly the sheep in 1997, calling on Hwang to submit his work for scientific confirmation.

"Accusations made in the press about the validity of the experiments published in South Korea are, in our opinion, best resolved within the scientific community," the scientists, including Dolly cloners Ian Wilmut of Edinburgh University and Keith Campbell of Nottingham University, wrote.

Doubts about cloning

Stem cell scientists hope to clone embryos to extract stem cells in order to better learn how diseases develop and even perhaps rejuvenate failing organs. The basic idea of cloning is to take a patient's genetic material and inject it into an unfertilized human egg. The implanted DNA then drives the egg to develop into an embryo.

Hwang is considered a national hero in South Korea for his cloning prowess. Hwang defended his work as scientifically sound.

However, some scientists noted that the first reports about Dolly, the first mammal cloned from an adult cell, were also questioned.

Seoul National University official Roe Jung-hye said on Monday that experts from the university would lead an investigation and conduct DNA tests on Hwang's tailored stem cell lines.

(China Daily 12/15/2005 page6)