Autophagy is a catabolic process involving lysosomal turnover of
proteins and organelles for maintenance of cellular homeostasis and mitigation of metabolic stress. Autophagy defects are linked to diseases, such as
liver failure, neurodegeneration,
inflammatory bowel disease, aging and
cancer. The role of autophagy in
tumorigenesis is complex and likely context-dependent. Human breast, ovarian and
prostate cancers have allelic deletions of the essential autophagy regulator BECN1 and Becn1(+/-) and other autophagy-deficient transgenic mice are
tumor-prone, whereas
tumors with constitutive Ras activation, including human
pancreatic cancers, upregulate basal autophagy and are commonly addicted to this pathway for survival and growth; furthermore, autophagy suppression by Fip200 deletion compromises PyMT-induced mammary
tumorigenesis. The double-edged sword function of autophagy in
cancer has been attributed to both cell- and non-cell-autonomous mechanisms, as autophagy defects promote
cancer progression in association with oxidative and ER stress, DNA damage accumulation,
genomic instability and persistence of
inflammation, while functional autophagy enables
cancer cell survival under stress and likely contributes to treatment resistance. In this review, we will focus on the intimate link between autophagy and
cancer cell metabolism, a topic of growing interest in recent years, which has been recognized as highly clinically relevant and has become the focus of intense investigation in translational
cancer research. Many
tumor-associated conditions, including intermittent
oxygen and nutrient deprivation, oxidative stress, fast growth and cell death suppression, modulate, in parallel and in interconnected ways, both cellular metabolism and autophagy to enable
cancer cells to rapidly adapt to environmental stressors, maintain uncontrolled proliferation and evade the toxic effects of radiation and/or
chemotherapy. Elucidating the interplay between autophagy and
tumor cell metabolism will provide unique opportunities to identify new therapeutic targets and develop synthetically lethal treatment strategies that preferentially target
cancer cells, while sparing normal tissues.