Cell‐Type‐Resolved Proteomics Reveals Distinct Immune and Metabolic Programs Between Primary and Recurrent Ascites in HGSOC

ABSTRACT High‐grade serous ovarian carcinoma (HGSOC) frequently recurs after platinum–taxane therapy, yet recurrence‐associated changes within ascites remain unclear. We performed cell‐type‐resolved quantitative proteomics on paired ascites samples collected at primary diagnosis and at disease recurrence from three HGSOC patients, profiling unsorted cells alongside matched CD45 − tumor‐enriched and CD45 + immune‐enriched fractions. Conventional proteomic label‐free quantitative (LFQ) analysis yielded limited significant proteins due to inter‐patient heterogeneity. To address this, we applied Gene Set Enrichment Analysis (GSEA) to identify coordinated pathway‐level alterations associated with recurrence. Across all cellular compartments, recurrent samples exhibited consistent downregulation of interferon‐α/γ–associated pathways alongside enrichment of oxidative phosphorylation and stress‐adaptive metabolic programs. In the CD45 + immune compartment, these changes were accompanied by enhanced IL‐2/STAT5 signaling and reduced antigen‐presentation pathways. Together, these findings suggest that recurrent ascites is characterized by a shift toward oxidative metabolism and a more immunosuppressive microenvironment.