Fig. 2.

Tumor interstitial fluids (TIFs) contain a diverse array of lipids that promote tumor growth and metastasis. The tumor interstitial fluid is rich in a diverse array of lipids, including free fatty acids (FAs), low-density lipoproteins (LDLs), oxidized LDLs (OxLDLs), cholesterol, cholesterol esters and triacylglycerols (TAGs). Tumor cells express a range of cell surface receptors to facilitate the uptake of lipids, including the scavenger receptor CD36 and the LDL receptor. Overexpression of Diglyceride acetyltransferase 1 (DGAT1) is a common feature of many tumors. DGAT1 is responsible for the synthesis of TAGs from FAs, which can then be stored in lipid droplets (LDs). Acyl cholesterol acyltransferase (ACAT) is also overexpressed in many tumors. ACAT plays a key role in cholesterol homeostasis by catalyzing the formation of cholesterol esters from free cholesterol and FAs. Together, TAGs and cholesterol esters form the major components of LDs. LDs are a feature of many tumor cells and promote lipid homeostasis by sequestering excess intracellular lipids to prevent lipotoxicity, peroxidation and ferroptosis. Fatty acids may also be synthesised endogenously from cytosolic acetyl-CoA. Fatty acid synthase (FASN) expression is a feature of many cancers and catalyses the production of palmitic acid. Palmitic acid can be converted to the monounsaturated fatty acid (MUFA) palmitoleic acid to protect against the toxic effects of saturated fatty acids (SFAs) such as palmitic acid