Effects of Fatty Acid Synthase Inhibition by Orlistat on Proliferation of Endometrial Cancer Cell Lines

Objective: Fatty acid synthase (FAS) is a key lipogenic enzyme that is highly expressed in endometrial cancer. Orlistat is a weight loss medication that has been shown to be a potent inhibitor of FAS. The goal of this study was to evaluate the anti-tumorigenic potential of orlistat in endometrial cancer cell lines. Methods: The endometrial cancer cell lines ECC-1 and KLE were used. Cell proliferation was assessed by MTT assay after treatment with orlistat. Cell cycle progression was evaluated by Cellometer and apoptosis was assessed using the Annexin V assay. Reactive oxygen species (ROS) was measured using the DCFH-DA assay. Western immunoblotting was performed to determine changes in FAS, cellular stress, cell cycle progression, and the AMPK/mTOR pathways. Results: Orlistat inhibited cell proliferation by 61 % in ECC-1 cells and 57 % in KLE cells at a dose of 500 μM. Treatment with orlistat at this concentration resulted in G1 arrest (p < 0.05) but did not affect apoptosis. Orlistat increased ROS and induced the expression of BIP (1.28-fold in ECC-1 compared to control, p < 0.05; 1.92-fold in KLE, p < 0.05) and PERK (2.25-fold in ECC-1, 1.4-fold in KLE, p < 0.05). Western immunoblot analysis demonstrated that orlistat decreased expression of important proteins in fatty acid metabolism including FAS (67 % in ECC-1, 15 % in KLE), acetyl-CoA carboxylase (40 % in ECC-1, 35 % in KLE), and carnitine palmitoyltransferase 1A (CPT1A) (65 % in ECC-1, 25 % in KLE) in a dose-dependent manner. In addition, orlistat at a dose of 500 μM increased expression of phosphorylated-AMPK (1.9-fold in ECC-1, p < 0.01; 1.5-fold in KLE, p < 0.05) and decreased expression of phosphorylated-Akt (25 % in ECC-1, p < 0.05; 37 % in KLE, p < 0.05) and phosphorylated-S6 (68 % in ECC-1, 56 % in KLE). Conclusions: Orlistat inhibits cell growth in endometrial cancer cell lines through inhibition of fatty acid metabolism, induction of cell cycle G1 arrest, activation of AMPK and inhibition of the mTOR pathway. Given that patients with endometrial cancer have high rates of obesity, orlistat should be further investigated as a novel strategy for endometrial cancer treatment. [Figure not available: see fulltext.]