Combination therapy with Chicoric acid and PD-1/PD-L1 blockade improves the immunotherapy response in patient-derived ovarian cancer xenograft model.

PURPOSE: Limited treatment options exist for refractory ovarian cancer (OC) due to its poor response to immune therapies. Therefore, there is an urgent need to develop new effective treatment strategies. Chicoric acid (CA) is reported to have immune-enhancing properties, but its efficacy in cancer treatment is not well understood. We hypothesize that CA might improve the efficacy of PD-1/PD-L1 blockade immunotherapy in refractory OC patients. METHODS: Patient-derived xenograft (PDX) models were constructed from chemoresistant advanced high-grade serous ovarian cancer patients. These models were treated with CA, aPD-1/aPD-L1 antibodies, or a combination of both. Single-cell RNA sequencing was performed to analyze the cellular composition of the tumor microenvironment (TME), evaluate treatment efficacy, and explore therapeutic mechanisms. Variations in peripheral blood lymphocytes were analyzed via fluorescence-activated cell sorting. Immunohistochemistry confirmed the variations in tumor-infiltrating lymphocytes and tumor cells. RESULTS: Immunocompetent peripheral blood mononuclear cell (PBMC)-PDX models were successfully constructed using malignant ascites fluid and PBMCs. After treatment, 158,734 cells from 15 samples were categorized into epithelial cells, T lymphocytes, myeloid cells, fibroblasts, and endothelial cells. CA enhanced the antitumor ability of immune cells against OC cells. Notably, CA stimulated the proliferation of CD45 + and CD3 + cells and promoted the migration of CD8 + and CD4 + T cells from peripheral blood to infiltrate the TME. Additionally, CA enhanced the response of OCs to aPD-L1/aPD-1 treatment, strengthened the interaction between tumor and nontumor cells, and identified APP/CD74 as a critical ligand‒receptor pair. CHI3L1 was also found to be a potential marker for predicting immunotherapy efficacy in OC. CONCLUSION: This study demonstrated that combination therapy with CA and aPD-1/aPD-L1 might be a promising strategy for treating OC effectively.