Morusin, a novel inhibitor of ACLY, induces mitochondrial apoptosis in hepatocellular carcinoma cells through ROS-mediated mitophagy

Objective: Morusin (Mor), a prenylated flavonoid isolated from the root bark of Morus alba L., exhibits potent anti-tumour effects; however, the molecular target of Mor is still not entirely clear. This study aimed to elucidate the mechanism of Mor against hepatocellular carcinoma (HCC) and identify potential molecular targets. Methods: Mitochondrial function was assessed by measuring the mitochondrial membrane potential, mitochondrial ultrastructure, oxygen consumption, and ATP levels. Mor-induced mitophagy was confirmed using western blotting, immunofluorescence, and fluorescent probes. Transcriptomics, flow cytometry, western blotting, qRT-PCR and biochemical assays were used to reveal the molecular mechanisms and targets of Mor against HCC. We further validated the interaction between Mor and the target proteins using molecular docking and biolayer interferometry (BLI). The inhibitory effect of Mor in vivo was evaluated using a Hep3B murine xenograft model. Results: Mor significantly reduced the ATP citrate lyase (ACLY) expression and inhibited ACLY activity in HCC cells. BLI analysis demonstrated a direct interaction between Mor and the ACLY active domain. Mor-induced ACLY inhibition led to ROS accumulation in HCC cells, which caused mitochondrial damage, triggered PINK1/Parkin-mediated mitophagy, and ultimately induced mitochondrial apoptosis. We further verified that ROS is crucial in the apoptotic action of Mor through experiments regarding an ROS scavenger. Mor also significantly inhibited tumour xenograft growth in vivo. In addition, analysis of human liver cancer clinical samples revealed elevated ACLY levels positively correlated with histologic grade. Conclusion: Collectively, our findings highlight Mor as a potent bioactive inhibitor of ACLY and a promising candidate for HCC therapy.