Once dubbed South Korea’s ‘king of cloning’, Woo Suk Hwang and his colleagues have requested the retraction of a landmark stem cell paper they published in a June 2005 edition of the journal Science. But he stands by the veracity of his findings in the face of a flurry of accusations that he fabricated the results.

The paper (Science, vol 308, p 1777), which outlines groundbreaking stem cell research in which 11 human embryonic stem cell lines were created specifically for patients, has become increasingly mired in controversy.

On Friday, the American Association for the Advancement of Science, which publishes Science confirmed that it had received Hwang’s request before a press briefing he gave earlier in the day.

“Science editorial received direct communication, by telephone, from Hwang and Dr Gerald Schatten, the lead authors of the 2005 paper. They said they wish to retract the paper,” says a statement from AAAS. All authors must agree to a retraction, it adds. “Dr Hwang has assured us that he is contacting his co-authors.”

“Science editorial continues to follow and encourage the official investigations now underway and will withhold comment on them until the investigations have been completed,” it says.

Data fabrication claims

Hwang's news conference in Seoul was in response to allegations of fabrication of data by colleague and co-author Sung Il Roh, at MizMedi Hospital, Seoul, circulating in the Korean media on Thursday.

“What I can say clearly is that we have produced patient-specific stem cells and we have the technology to do so,” Hwang maintained. The importance of the work, which claimed to have created 11 stem cell lines specific to each of 11 different patients, is that it showed stem cell therapies could be tailored to individuals, avoiding the immune rejection problems that usually hamper tissue transplants.

On Thursday, Roh reportedly told Korean media: “Of the 11 stem cell lines, at least nine are faked and the veracity of two others has yet to be confirmed.”

But Hwang says that of the original 11 stem cell lines, six died because of contamination and five others were frozen. He says these are being thawed and that he will validate his findings by testing them within 10 days. But he did admit “irretrievable mistakes in the photography” which accompanied the study.

He told Science last week that the paper contains four instances in which the same photographs were mistakenly used to represent cells cloned from different patients.

Questions have also been raised about the DNA fingerprint plots in the paper. This technique was used to verify the identity of the cloned cells – to show that the DNA in their nuclei matched the DNA of the original cells taken from the patients.

Cell mix-up

Speaking at a separate press conference on Friday, after Hwang had spoken, Roh said another researcher and co-author, Sun Jong Kim, then at MizMedi Hospital, told him that the results were fabricated and that Hwang and his colleague Sung Keun Kang, also at Seoul National University, ordered Kim to fake them, according to South Korean newspaper The Chosun Ilbo.

Hwang says the discrepancies in the documentation supporting his paper are probably due to a mix-up between the team’s stem cells and stem cells stored at MizMedi Hospital.

"I believe that one of my collaborators, who had access to both the laboratory at Seoul National University and the MizMedi Hospital, switched the stem cell lines,” said Hwang, according to The Korea Times. However, Roh denied the allegations, saying that he never authorised the provision of stem cell samples to Hwang’s research team.

But Kim, who is now at the University of Pennsylvania, US, defended the research on Friday and denied any falsification. He told KBS news that he had personally seen eight stem cell lines and another three being nurtured. "The stem cells were cultivated through normal procedures, and eight members of Hwang's research team verified them every morning," he said.

Ethical rules

The scandal surrounding Hwang’s work blew up in earnest in early November over allegations that the eggs of junior researchers on his team were used for the research. International ethical rules forbid the use of eggs from junior colleagues to avoid the possibility of coercion.

Hwang, based at Seoul National University, eventually admitted this was true, apologised and resigned from his official posts on 24 November. But then allegations that Hwang had fabricated results began to surface in the South Korean media.

Leading researchers told New Scientist that they wanted independent testing of Hwang’s results. And the team’s one US co-author, Gerald Schatten at the University of Pittsburgh, had already asked for his name to be taken off the paper.

Hwang’s team were also the first in the world to derive a human embryonic stem cell line from a cloned human embryo (Science March, vol 303, p 1669). And in August 2005, the team announced the first successful cloning of a dog.