Figure 3.

Understanding energy transfer in cancer metabolism: Stromal autophagy and cancer-associated cachexia. Diagram summarizing that autophagy in the tumor stroma is used by adjacent epithelial cells to fuel tumor growth via oxidative mitochondrial metabolism. This local phenomenon may spread systemically and explains the onset of cancer-associated cachexia, characterized by systemic wasting and a negative net energy balance. A⁺ signifies stromal autophagy, which results in fuel production. A⁻ signifies an absence of autophagy in cancer cells. A^R signifies genetic resitance to autophagy in cancer cells, e.g., when Beclin1 gene expression is silenced. Both A⁻ and A^R would be associated with fuel consumption by cancer cells. The direction of energy flow, from the autophagic tumor stroma to the anabolic cancer cells, is indicated by the direction of a blue arrow.