ATG5 and cancer: Interestingly, autophagy was first described as a tumour-suppressive mechanism, based on the fact that heterozygous deletion of mammalian Beclin1 (the orthologue of Atg6) led to the development of malignant neoplasms in various organs in mice.16,17 However, this partial autophagy deletion phenotype was not seen in mouse models that were totally autophagy deficient (in ATG5−/− mice, for example):18 these mice spontaneously developed only benign liver tumours.