Oleic acid enhances the proliferation of gallbladder cancer cells via the GPR120/ERK pathway

Gallbladder cancer (GBC) is a highly aggressive malignancy exhibiting a correlation between increased body mass index and increased risk of developing GBC. In obese individuals, the release of free fatty acids from the adipose tissue into the circulating blood is augmented. However, the role of oleic acid (OA), one of the most abundant monounsaturated fatty acids in the plasma, in GBC cell proliferation has not been determined. In this study, we investigated the effects of OA on the proliferation of GBC cells. We focused on the role of G protein-coupled receptor 120/free fatty acid receptor 4 (GPR120/FFAR4) and G protein-coupled receptor 40/free fatty acid receptor 1 (GPR40/FFAR1), which have a high affinity for long-chain fatty acids. OA significantly promoted the proliferation of human GBC cell lines (G-415 and GBC-SD) in vitro, with the highest increase observed at 200 μM OA. In vivo, OA-treated nude mice bearing G-415 xenografts exhibited enhanced tumor growth compared to controls. Immunohistochemical analysis revealed the expression of GPR120 and GPR40 in cultured GBC cells and patient tissues. OA-induced proliferation was mediated by GPR120, as evident from significantly reduced cell proliferation upon GPR120 silencing or inhibition, and no effect of GPR40 inhibition. Furthermore, OA-induced GPR120 activation enhanced ERK phosphorylation, implicating the GPR120/ERK signaling pathway in GBC cell growth. To our knowledge, this is the first study to elucidate the role of OA in GBC cell proliferation via GPR120, suggesting its potential as a therapeutic target for GBC treatment.