Some of stem cell researcher Hwang Woo-suk's high-profile human cloning work announced earlier this year may have been fabricated, a former top collaborator charged as he attempted to distance himself from the groundbreaking research.
University of Pittsburgh researcher Gerald Schatten has demanded that the journal Science remove him as the senior author of a report it published in June to international acclaim that detailed how individual stem cell colonies were created for 11 patients through cloning.
"My careful re-evaluations of published figures and tables, along with new problematic information, now casts substantial doubts about the paper's accuracy," Schatten wrote in a letter to Science released late on Tuesday by the university. "Over the weekend, I received allegations from someone involved with the experiments that certain elements of the report may be fabricated."
Hwang could not immediately be reached for comment.
An e-mail sent to his office at the start of the business day in Seoul was not returned.
Pitt spokeswoman Jane Duffield said Schatten wouldn't make any further comment while the university investigated the matter.
Schatten's highly unusual demand, in a letter that Science confirmed receiving on Tuesday, adds to growing skepticism over Hwang's findings and places the entire cloning and stem cell field under a cloud.
"It's a very serious step. It's not good," said Rudolf Jaenisch, a leading stem cell scientist at the Whitehead Institute for Biomedical Research located in Cambridge, Massachusetts.
Many stem cell scientists had stood by Hwang's work even as he admitted to ethical lapses and minor data reporting errors.
Now, a significant number, such as Jaenisch, are calling on Hwang to submit his cloning research to independent analysts to bolster public confidence, which they perceive as eroding because of the continued controversy over Hwang's work.
Schatten set off the ethics furor last month when he publicly accused Hwang of collecting eggs from subordinate scientists, a practice many consider unethical, and lying about it to him.
But until now, even Schatten has maintained that the main findings of the paper -- that tailor-made stem cells were extracted from embryos cloned from the DNA of sick volunteers -- were valid.
Science acknowledged receiving Schatten's demand, but spokeswoman Ginger Pinholster declined to release Schatten's letter because "it contains unsubstantiated allegations."
Schatten's name was listed last among the 25 authors, signifying that he was the senior researcher on the project.
"No single author, having declared at the time of submission his full and complete confidence in the contents of the paper, can retract his name unilaterally, after publication," the journal said in a statement.
The journal has said it has no reason to believe Hwang's primary finding "is any way fraudulent or questionable."
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 a national hero in South Korea for his cloning prowess. He has publicly apologized for the ethical lapses and quit as head of the World Stem Cell Hub, an international project he had launched in October that envisioned California and British labs in addition to a facility in South Korea.