ACSVL3 depletion in U87 glioma cells affects both fatty acid and cholesterol homeostasis

Abstract

Human malignant gliomas overexpress ACSVL3, a member of the very long‐chain fatty acyl‐CoA synthetase family. Depletion of ACSVL3 in cultured human U87 glioma cells by RNA interference decreased both their malignant growth properties in vitro and their ability to produce tumors in mice. To understand how ACSVL3 knockdown (KD) in U87 cells promotes these beneficial effects, we investigated fatty acid and cholesterol homeostasis. Incorporation of [14C]C16:0 into several lipids, including phosphatidylinositol, phosphatidylethanolamine, and non‐hydroxy ceramide, was reduced in KD U87 cells. Although the mass of triacylglycerol (TAG) in U87 cells was barely detectable, [14C]C16:0 incorporation into TAG was robust, and was decreased in KD glioma cells. Surprisingly, the mass of free cholesterol was reduced by ~40% in ACSVL3 KD cells. This was due, in part, to decreased de novo cholesterol synthesis, as measured by [14C]acetate incorporation. Acetate incorporation into free fatty acids was also reduced, indicating that ACSVL3 depletion also affects de novo fatty acid synthesis. We hypothesize that ACSVL3 depletion affects fatty acid and cholesterol homeostasis via a common mechanism. Studies to elucidate this mechanism are in progress. Supported by NIH grant NS062043 and a grant from the National Brain Tumor Society.