Hispidulin suppresses osteosarcoma by directly targeting FABP4 to disrupt lipid metabolism and inhibit the PI3K/AKT pathway.

BACKGROUND: Osteosarcoma (OS), a prevalent primary bone malignancy, has a dismal prognosis in metastatic cases (5-year survival < 30%), highlighting the need for novel therapies. Hispidulin (HIS), a natural flavonoid, shows anticancer potential, but its precise mechanism and direct target in OS are uncharacterized. PURPOSE: This study aimed to delineate HIS's anti-neoplastic mechanisms in OS, focusing on its impact on lipid metabolism, associated signaling, and its direct molecular target. METHODS: In vitro anti-tumor effects of HIS were assessed (CCK-8, colony formation, Transwell, flow cytometry). RNA sequencing and molecular docking identified regulatory pathways and targets. Western blotting, lipid metabolism assays, and rescue experiments explored mechanisms. In vivo efficacy was evaluated using xenografts. RESULTS: HIS potently inhibited OS cell proliferation, colony formation, migration, and invasion, with minimal toxicity to normal osteoblasts. It induced G2/M arrest and apoptosis. HIS directly targeted Fatty Acid Binding Protein 4 (FABP4), modulating lipid metabolism and subsequently inhibiting the PI3K/AKT pathway. This reduced intracellular free fatty acids and fatty acid synthase activity. FABP4 overexpression abrogated HIS's anti-tumor effects. In vivo, HIS impeded tumor growth and reduced Ki67 and FABP4 expression. CONCLUSION: Hispidulin exerts robust anti-tumor activity in OS by directly targeting FABP4, thereby disrupting lipid metabolism and suppressing the oncogenic PI3K/AKT cascade. HIS is a highly encouraging therapeutic candidate for OS.