The two facets of autophagy in cancer. At early stages, autophagy acts as a tumor suppressor mechanism by enhancing the degradation of damaged proteins and organelles, mostly mitochondria. In doing so, autophagy acts as a quality control system that decreases ROS production and genomic instability. Moreover, autophagy prevents necrotic cell death in apoptosis-defective cells, thereby reducing local inflammation and tumor growth. Also, autophagy may serve (in some cases) as a mechanism that leads to cell death. On the other hand, at later stages of tumor development, activation of autophagy supplies tumor cells under metabolic stress conditions with nutrients and also maintains mitochondrial metabolism by providing metabolic intermediates, which promote cell survival and tumor growth. Finally, autophagy acts as a mechanism that promotes resistance to cancer therapy.
