In contrast, both CTVT and DFTD have retained the ability to express MHC in certain contexts and for CTVT this may have been an evolutionary advantage; eventual MHC expression allows the dog immune system to control tumour growth, preventing death of the host and allowing sufficient time for the tumour to be transmitted.35 Although the epigenetic mechanisms responsible for MHC loss in DFTD are not yet understood, they may be indicative of global changes of chromatin remodelling and/or methylation patterns that occurred in these cells when they transformed to malignancy. This evidence concerns the gene HLA-C and neoplasm.