Abstract PR015: Tumor-derived IL-4 links chemotherapy to immunotherapy resistance in ovarian cancer

Abstract Ovarian cancer (OvCa) remains largely refractory to immune checkpoint blockade (ICB), owing to a profoundly immunosuppressive tumor microenvironment (TME). Single-cell RNA sequencing (scRNA-seq) of patient tumors has revealed a TME enriched in immunosuppressive macrophages and characterized by exclusion of T cells from the tumor core, features strongly associated with ICB resistance. However, the molecular mechanisms underlying the establishment of this immune landscape remain poorly understood. To identify regulators of OvCa immunity, we employed Perturb-map, a first-of-its-kind spatial functional genomics platform that enables multiplexed CRISPR/Cas9 knockout of candidate genes while preserving the spatial context of tumor–TME interactions in situ. We targeted 35 genes, prioritized through ligand–receptor interaction analysis of human OvCa scRNA-seq data, in an immunocompetent OvCa mouse model. Among these, IL-4 emerged as a key driver of ICB resistance. While IL-4 knockout did not affect tumor growth in untreated animals, it substantially remodeled the local TME and rendered tumors responsive to anti-PD-1 therapy. Unexpectedly, we found that both mouse and human ovarian cancer cells are a source of IL-4, a cytokine traditionally restricted to immune cells. Analysis of patient tumors revealed that tumor-associated macrophages exhibit a robust IL-4, induced transcriptional signature, implicating IL-4 in shaping the immunosuppressive TME in human disease, consistent with our preclinical findings (Cell, 2024). Furthermore, we observed that standard-of-care chemotherapy regimens, including carboplatin, paclitaxel, and cisplatin—induce a dose-dependent increase in IL-4 expression in both murine and human OvCa cell lines. This chemotherapy-induced IL-4 upregulation may contribute to immune evasion and recurrence following initial therapeutic response. Therapeutically, combined blockade of IL-4Rα and PD-1 significantly delayed tumor progression in vivo compared to monotherapy, suggesting that IL-4 signaling is both a necessary and targetable mechanism of immune resistance. These findings are clinically actionable, as Dupilumab, an FDA-approved anti-IL-4Rα antibody, is already in clinical use and well-tolerated. Our results uncover a previously unrecognized, chemotherapy-induced immunoregulatory axis in ovarian cancer and provide a strong rationale for therapeutic strategies that combine IL-4 pathway inhibition with ICB to overcome resistance and improve patient outcomes. Citation Format: Gurkan Mullaoglu, Hunter Potak, Paula Guerrero Gonzalez, Gardner Davlin, Joshua Leinwand, Dmitriy Zamarin, Brian Brown, Alessia Baccarini. Tumor-derived IL-4 links chemotherapy to immunotherapy resistance in ovarian cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Ovarian Cancer Research; 2025 Sep 19-21; Denver, CO. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl):Abstract nr PR015.