This work was supported by Fundación Universidad de Oviedo and Instituto Asturiano de Odontología. C.G.V. was financed by Fundación Universidad de Oviedo and L.S. was a recipient of Beca de Colaboración from Ministerio de Educación, Cultura y Deporte of Spain. This work was also partially supported by a grant from the Instituto de Salud Carlos III (Spain) (FISS PI11/00371) and Fondos FEDER. The Instituto Universitario de Oncología is supported by Obra Social Cajastur.