Melatonin enhances the efficacy of anti-PD-L1 by improving hypoxia in residual tumors after insufficient radiofrequency ablationOA

The hypoxic microenvironment and inflammatory state of residual tumors caused by insufficient radio-frequency ablation(iRFA)are major reasons for rapid tumor progression and pose challenges for immu-notherapy.We retrospectively analyzed the clinical data of patients with hepatocellular carcinoma(HCC)treated with RFA and observed that iRFA was associated with poor survival outcomes and progression-free survival.Using an orthotopic HCC mouse model and a colorectal liver metastasis model,we observed that treatment with melatonin after iRFA reduced tumor growth and metastasis and achieved the best out-comes when combined with anti-programmed death-ligand 1(anti-PD-L1)therapy.In mechanism,melatonin inhibited the expression of epithelial-mesenchymal transitions,hypoxia-inducible factor(HIF)-1 α,and PD-L1 in tumor cells after iRFA.Flow cytometry revealed that melatonin reduced the proportion of myeloid-derived suppressor cells and increased the proportion of CD8+T cells.Transcriptomic analysis revealed an upregulation of immune-activated function-related genes in residual tumors.These findings demonstrated that melatonin can reverse hypoxia and iRFA-induced inflammation,thereby overcoming the immunosuppressive tumor microenvironment(TME)and enhancing the efficacy of immunotherapy.