Defective autophagy leads to cancer.

Cellular proteins are degraded within two distinct compartments: the proteasome and the lysosome. Alterations in proteasomal degradation can contribute to carcinogenesis. In contrast, alterations in autophagic protein degradation through the lysosome have not been linked to cancer. Now two reports demonstrate that the autophagic gene, Beclin 1, is a haploinsufficient tumor suppressor gene. These new data suggest that autophagic degradation provides an important mechanism to prevent cellular transformation.