A controversial paper purporting to show a link between genetically modified corn and tumors in rats is poised to be retracted by the journal that published it following a storm of critics from scientists over the past year.

University of Caen biologist Gilles-Eric Seralini and colleagues published their findings on GMO corn and rats in September 2012 in the journal Food and Chemical Toxicology. They reported that rats fed genetically modified corn or water spiked with glyphosate, the herbicide used in conjunction with GM corn, were more prone to tumors and multiple organ failures. But there were odd signs surrounding the paper from the start: Seralini allowed some journalists early access to the paper, but only on the condition that they sign a confidentiality agreement that reporters not seek comments from other scientists on the paper before publication, an extremely unusual move. Once the research was released, scientists criticized almost every element of the paper: the experiment’s design, the use of a strain of rats prone to tumors, the lack of standard controls, and conclusions that did not seem fully supported by the data.

“This paper as it is now, presents poor quality science and dubious ethics,” scientists from the Brazilian Biosafety Association wrote in a letter to the journal.

On Thursday, French newspaper Le Figaro reported that Food and Chemical Toxicology editor-in-chief A. Wallace Hayes had sent Seralini a letter saying the paper will be retracted if he and his colleagues do not agree to withdraw it.

The proposed retraction notice contained in the letter [PDF] says, in part, that while Hayes found “no evidence of fraud or intentional misrepresentation of the data… there is legitimate cause for concern regarding both the number of animals in each study group and the particular strain selected… Given the known high incidence of tumors in the Sprague-Dawley rat, normal variability cannot be excluded as the cause of the higher mortality and incidence observed in the [rats fed GM corn].”

On Friday, Seralini and colleagues stood by their conclusions and paper in a response to Hayes’ letter. They pointed out that Sprague-Dawley rats are used by the U.S. national toxicology program and some of Monsanto’s own studies of GM corn (though Monsanto’s studies with Sprague-Dawley rats only went on for 90 days, while the rats used in the Seralini study were observed over two years). Seralini’s team also claimed a double standard was at play:

“All previous studies finding adverse effects of GE crops have been treated by regulators with the attitude: only those studies showing adverse effects receive a rigorous evaluation of their experimental and statistical methods, while those that claim proof of safety are taken at face value,” Seralini and colleagues wrote.

"The major flaws in this paper make its retraction the right thing to do," Cathie Martin, a biologist at the U.K.’s John Innes Centre, a plant research institute, told Reuters. "The strain of rats used is highly susceptible to tumors after 18 months with or without GMO in their diets."

But even if scientists have heavily criticized the paper, some may question if retraction is the right step at this stage of publication. Ivan Oransky of Retraction Watch, an online publication that monitors controversial papers and retractions, noted that Hayes’ letter does not offer any of the usual criteria for retraction, instead implying that the paper never should have been published.

“This will likely be quite controversial, and it will be interesting to see how the scientific community reacts… many scientists say that retraction should be reserved for fraud and serious error,” Oransky wrote. “Does that hold for a paper that many criticized as deeply flawed — and which challenged GMOs, whose use is supported by many scientists?”

RELATED STORIES