UPLC-Q-TOF/MS-based serum metabolomics revealed anti-tumor mechanism of ethanol-soluble acidic components from Camellia oleifera cake and synergy with PD-1 inhibitor

This study aimed to explore the anti-tumor activity and mechanisms of the ethanol-soluble acidic components (ESAC) of Camellia oleifera cake through a combination of network pharmacology, in vitro and in vivo studies, and metabolomics based on UPLC-Q-TOF/MS. Additionally, the potential application of ESAC in combination with PD-1 inhibitors was explored. In this work, our results demonstrated that ESAC exhibited anti-tumor activities mediated by regulated cell death (RCD), which were associated with apoptosis, pyroptosis, and ferroptosis. UPLC-Q-TOF/MS-based serum metabolomics revealed that metabolic disorders were occurred in tumor group when compared to control group. In contrast, ESAC significantly inhibited abnormal energy metabolism including glycolysis, tricarboxylic acid cycle, and amino acid metabolism. Consequently, hexokinase and malate dehydrogenase, key enzymes of energy metabolism, were determined, and data showed that treatment of tumor mice with ESAC significantly suppressed activities of these metabolic enzymes when compared to tumor group, confirming that mitigating metabolic disorders contributed to the anti-tumor activities of ESAC. Moreover, ESAC could also reduced PD-L1 expression in tumor tissue, which was similar to the effect of PD-1 inhibitor. Furthermore, combination treatment with ESAC and PD-1 inhibitor was superior to either treatment alone, and it enhanced pyroptosis through the NLRP3/Caspase-1/GSDMD pathway. Together, we concluded that metabolic correction and PD-L1 inhibition were the critical mechanisms to exert anti-tumor activities of ESAC.