HLA-C and cancer: High levels of genetic diversity at MHC genes play a critical role in protecting populations of vertebrate species from contagious cancer, of which two forms do exist, which are either transmitted by biting (as in the Devil Facial Tumor Disease, DFTD) or by sexual contact (as in case of the Canine Transmissible Venereal Tumor, CTVT, e.g., in Bernadine dogs) (Mello Martins et al., 2005).