New Data Spark Retraction Request for Chronic Fatigue Virus Study

by Jon Cohen 

You cannot un-ring a bell, but you can retract a scientific study. Then again, as a raging debate over a Science paper that linked a mouse retrovirus to chronic fatigue syndrome (CFS) makes clear, retractions can be a tall order, too.

In conjunction with their decision to publish two additional papers that strongly question the link between the virus, known as XMRV, and CFS, editors at Science last week privately requested the retraction of the study that 2 years ago first made this connection. Replying on behalf of the original paper's authors, Judy Mikovits of the Whittemore Peterson Institute for Neuro-Immune Disease in Reno, Nevada, yesterday declined the request in a letter to Science, calling the action "premature." Today, after The Wall Street Journal published leaked details of the exchange, Science released online the two new papers along with an Editorial Expression of Concern about the 2009 paper written by Editor-in-Chief Bruce Alberts.

On 26 May, Alberts and Executive Editor Monica Bradford wrote Mikovits and noted they were "extremely concerned" about the validity of the original paper given "the growing number of research papers from independent investigators who have either failed to replicate your original finding that XMRV is associated with chronic fatigue syndrome and/or who have provided evidence that laboratory reagents are widely contaminated with the virus." They asked Mikovits and her co-authors to voluntarily retract their paper, known as Lombardi et al., writing that "it would be in the best interest of the scientific community." CFS patients, who have no treatment for their baffling condition, have paid intense attention to the XMRV findings with some already taking antiretroviral drugs marketed to combat HIV.

Mikovits, who supplied the Science letter and her subsequent responses to ScienceNOW, says the retraction request "came out of nowhere" late on Thursday afternoon before a holiday weekend and did not include the new papers Science planned to publish. "We were all just pretty well stunned," she says, noting that all but one of the co-authors of the original paper joined a conference call Friday morning and agreed not to retract. In her 30 May letter to Alberts and Bradford, Mikovits wrote that she and her co-authors shared the "deep concern" over the number of studies that have not been able to replicate their findings. But she warned that publishing the expression of concern would have a "disastrous impact on the future of this field of science" and maintained that their original report that found evidence of the virus in 67% of CFS patients and only 3.7% of controls was accurate.

The two new papers published online by Science today both point to contamination as the most likely explanation for the results from Mikovits's 2009 paper and from one other high-profile report that found a link between CFS and XMRV-related mouse retroviruses. One study, led John Coffin of Tufts University in Boston and Vinay Pathak of the U.S National Cancer Institute in Frederick, Maryland, describes how laboratories in the 1990s accidentally created XMRV while working with mice and a human prostate tumor to make an immortalized cell line to study prostate cancer. The first reports of XMRV came in 2006 from labs studying prostate cancer. The links to that disease are now in question, too. (ScienceNOW reported on Pathak's presentation of his origin findings at a meeting in March.)

Retrovirologist Jay Levy of the University of California, San Francisco, headed the group behind the second paper released today, which failed to find XMRV in 61 patients who had confirmed diagnoses of CFS. Although other studies have not found XMRV in CFS patients, this one included 43 people who were notified earlier by Mikovits's group that they were infected with the virus. The researchers further showed that mouse retroviruses routinely contaminate many commonly used lab reagents. "The net is really closing around" the 2009 paper, says Jos van der Meer of Radboud University in the Netherlands, who pointed out several shortcomings in the study in a 2010 comment in Science and whose own study of 32 Dutch CFS patients failed to find any trace of XMRV.

Mikovits says neither of the new studies undermines her group's original report. Anyone who reads the new papers, she asserts, will conclude that they "have nothing to do with Lombardi et al." The original study only speaks to labs that have used a specific prostate cancer cell line or its derivatives, she contends. As her letter to Alberts and Bradford explains in detail, the human cell lines in her group's lab repeatedly tested negative for XMRV, and they have no mouse lines. As for the Levy study, Mikovits insists that her team carefully controlled for contamination of reagents. She also claims the work fails to faithfully replicate their methods. "They didn't do one thing we did," she says. Levy disagrees, saying, "We did it exactly the way they did it."

Jonathan Stoye, a retrovirologist at the MRC National Institute for Medical Research in London who co-authored a perspective in Science supportive of the original work when it first appeared, now believes that contamination explains those results. He says Mikovits and her team have offered "an endless succession" of criticisms about the way other labs have conducted studies. "This isn't a conspiracy against them: Tens of labs have tried to reproduce their findings without success," Stoye says. "There are some very smart people in this, and they would not have got this wrong. It's an insult to us all. My lab will not do any more XMRV research."

Stoye may be abandoning the topic, but two multilab studies organized by the U.S. National Institutes of Health are now evaluating blinded blood samples from CFS patients and controls to determine whether XMRV indeed has links to the disease. Mikovits's team is participating, and results are expected by the end of the year. "Science eagerly awaits the outcome of these further studies and will take appropriate action when their results are known," concludes Alberts's expression of concern.

Farming Conquered Europe at Least Twice

by Michael Balter 

The rise of agriculture in the Middle East, nearly 11,000 years ago, was a momentous event in human prehistory. But just how farming spread from there into Europe has been a matter of intense research. A new study of ancient DNA from 5000-year-old skeletons found in a French cave suggests that early farmers entered the European continent by at least two different routes and reveals new details about the social structures and dairying practices of some of their societies.

Scientists studying the spread of farming into Europe have numerous questions: Was agriculture brought in primarily by Middle Eastern farmers who replaced the resident hunter-gatherers? Or did agriculture advance through the spread of technology and ideas rather than people? And was there just one wave of farming into the continent or multiple waves and routes?

Until recently, researchers had to rely on the genetic profiles of modern-day Europeans and Middle Easterners for clues. Numerous such studies, especially of Y chromosomes, which are transmitted via the paternal line, suggest that actual farmers, not just their ideas, spread westward over the millennia, eventually reaching the British Isles. Yet other studies, based on mitochondrial DNA (mtDNA), which is inherited maternally, have come to the opposite conclusion, suggesting that farmers had local European ancestry.

Now, new studies have begun to resolve these issues by sequencing the DNA of the prehistoric farmers themselves. Some of this research, most notably in Germany, suggests that male farmers entering central Europe mated with local female hunter-gatherers—thus possibly resolving the contradiction between the Y chromosome and mtDNA results.

The new paper, published online this week in the Proceedings of the National Academy of Sciences, backs up that idea. A team led by molecular anthropologist Marie Lacan of the Paul Sabatier University in Toulouse, France, reports work on ancient DNA—both mitochondrial and Y-chromosomal—from more than two dozen skeletons found in the 1930s in a cave called Treilles in southern France. Archaeologists think Treilles is a communal grave site because the bones add up to 149 individuals, 86 adults and 63 children. The team took DNA in such a way as to ensure that each individual was sampled only once (using teeth that were still attached to a lower jaw) and was able to obtain ancient DNA from 29 people.

They found that the female and male lineages seemed to have different origins. The mtDNA showed genetic markers previously identified as having deep roots in ancient European hunter-gatherer populations, but the Y chromosomes showed the closest affinities to Europeans currently living along the Mediterranean regions of southern Europe, such as Turkey, Cyprus, Portugal, and Italy. The team concludes that, in addition to the spread of farming into Central Europe suggested by the German studies, there appears to have been at least one additional route via southern Europe.

The communal grave also yielded additional intriguing details about these ancient Europeans. Most of the skeletons were males, and many appeared to be very closely related: At least two pairs of individuals were almost certainly father and son, and another pair were brothers. That suggests that the incoming male farmers established a so-called patrilocal society, in which the men stay put on their land but mate with women who come in from surrounding regions, the team concludes.

The study also showed that, in contrast to ancient DNA findings from central Europe, the people from Treilles lacked a key genetic variant that allows the body to digest lactose into adulthood. That’s consistent with other archaeological evidence that central European farmers herded dairy cows, whereas Mediterranean farmers herded sheep and goats and drank fermented milk, which has much lower lactose levels.

Lounès Chikhi, a geneticist at Paul Sabatier University who has studied the spread of farming for many years, praises the team for getting both Y chromosome and mtDNA from the same skeletal collection. “We have been calling for exactly this kind of data,” Chikhi says, “so I am very excited.” Colin Renfrew, an archaeologist at the University of Cambridge in the United Kingdom, agrees that the findings support a second, southern European spread of farming. “They do indeed suggest a significant population influx from the Eastern Mediterranean.”

But Wolfgang Haak, a geneticist at the University of Adelaide in Australia, says that Treilles may be too young to provide reliable information about the spread of farming in southern Europe, which began at least 2000 years earlier. While these earlier migrations “should have left a genetic mark in later periods,” Haak says, Treilles might not be the “best candidate” for tracing them. The ancient DNA Lacan is now extracting from skeletons across France and Spain, Haak says, should provide more “piece[s] of the enormous puzzle we are trying to put together.”

Do Cell Phones Cause Cancer? An Explosive 'Maybe'

by Jennifer Couzin-Frankel 

Whether or not cell phones cause brain cancer is a question that's been debated (but not answered) for years, and today the World Health Organization (WHO) stepped into the fray. A WHO committee that evaluates various potential cancer-causing agents concluded that radiofrequency electromagnetic fields, including cell phones, are "possibly carcinogenic" to people. The announcement was seized upon and published in dozens of news outlets within minutes.

The International Agency for Research on Cancer (IARC) arrived at the conclusion of possible carcinogenicity after an 8-day review of the literature by 31 experts, in Lyon, France. The classification falls in the middle of IARC's hierarchy of risk, joining a group of more than 250 potential carcinogens that also includes lead, engine exhaust, and occupational exposure to dry cleaning. In a sign of how tough it is to determine that something doesn't cause cancer, just one of the 900 or so agents that IARC has evaluated, caprolactam, a component of fibers and plastics, falls in the "probably not carcinogenic" category.

When it comes to cell phones, "we found some threads of evidence telling us how cancer might occur, but I think there are acknowledged gaps and uncertainties," said Jonathan Samet, chairperson of the IARC Working Group and a physician and public health expert at the University of Southern California in Los Angeles, during a press conference. The working group was particularly influenced by an international study called Interphonethat's examining whether exposure to radiofrequency electromagnetic fields from cell phones causes cancer. Last year, the Interphone study group wrote in the International Journal of Epidemiology that it saw "no increase in risk of glioma or meningioma." It continued: "There were suggestions of an increased risk of glioma at the highest exposure level, but biases and errors" make it tough to show that the phones were the cause. "The possible effects of long-term heavy use of mobile phones require further investigation," they concluded.

IARC would like more research as well. Samet noted that at this point there are almost 5 billion cell phone subscriptions worldwide, and "we anticipate an ever larger population that is exposed for longer and longer." That said, shifting cell phones from the "possible" category to a more definitive one won't be easy. Epidemiologic studies like Interphone tend to match healthy people with those who have brain cancer and ask both to recall their cell phone use. "We know that is inherently imperfect," said Samet. And because all these studies take time to conduct, they inevitably examine older technology. Animal studies looking at the risk from radiofrequency electromagnetic fields have been mixed, both in whether they see a danger and in why that might be.

Whether IARC re-evaluates cell phone hazards, the committee says, will depend on what new research comes out.