Fatty acid synthesis supports tumor progression through facilitating the activity of TORC1 signaling

Biosynthesis of lipids and fatty acids (FAs) is essential for the normal functioning of cellular processes, and lipid availability determines the progression of multiple malignant tumor types. To date, the roles of individual steps in lipid biosynthesis during tumor growth and their interaction with intracellular signaling pathways are not well understood. Our study demonstrates that upregulation of de novo FA and lipid synthesis is a conserved characteristic of malignant tumors. In vivo tumor cell-specific silencing of components of the neutral lipid biosynthetic apparatus revealed that loss of several enzymes involved in FA and diacylglycerol synthesis inhibited tumor growth. Specifically, acetyl-CoA carboxylase (ACC), which catalyzes the first step of FA synthesis, drives late-stage tumor growth. FA synthesis perturbation led to inactivation of TORC1 (mechanistic Target of Rapamycin Complex 1)-accompanied by activation of the catabolic process autophagy. Moreover, TORC1 activity cannot be fully restored by hyperactivation of upstream Insulin/PI3K signaling or inhibition of AMP-activated kinase (AMPK) in ACC-deficient tumor cells, but supplementation with ectopic oleic acid can partially increase TORC1 activity and tumor progression. In addition to their metabolic value, the role of FAs in promoting TORC1 gives us new insight into cancer cell dependence on de novo FA synthesis.