One doesn't have to go to Wikileaks to find out about U.S. advocacy of GMOs to the Vatican. It has been a consistent effort: Colin Powell as Secretary of State tried to have the Vatican silence Jesuit Fr. Peter Henriot who helped the Zambian government reject GMO grain during a food crisis in Zambia.
The first thing that Condaleeza Rice told the Vatican on her first visit was to support GMOs The U.S. mission to the Holy See has always supported the moral imperative to have the Vatican support GMOs and convinced the Pontifical Academy of Sciences to host two conferences on this topic, one in 2004 and one in 2008. The second meeting only included supporters of GMOs, including among the speakers was Nino Fodoroff, biotechnology advisor to Secretary of State Hilary Clinton.