Role of M2 Macrophages in Chemoresistance of Epithelial Ovarian Cancer

OBJECTIVE: One of the hallmark characteristics of ovarian cancer is the development of resistance to chemotherapeutics. The mutual interactions with tumor cells and stromal microenvironment contribute to phenotypically polarization of tumor associated macrophages. Macrophages consist of at least two subgroups, M1 and M2. M2 macrophages are endowed with a repertoire of tumor-promoting capabilities involving immuno-suppression, angiogenesis and neovascularization, as well as stromal activation and remodeling. Therefore, there is a need for more practical targets to inhibit chemotherapeutic drug resistance and cancer progression due to ovarian cancer-macrophage interactions. To better understand the mechanism of chemoresistance in ovarian cancer cells, we aimed to investigate the influence of macrophages on the tumor cell response to carboplatin and identify the genes associated with chemoresistance. METHODS: Macrophages were differentiated into M1 and M2 macrophages by cytokine treatment of monocytes. The tumor microenvironment (TME) was modified by transwell co-culture assay. We treated the carboplatin and tested chemoresistance. We also examined expression of key genes associated with EMT (Epithelial-Mesenchymal Transition), PD-L1 and chemoresistance. Nanostring analysis identified gene expression changes in tumor signaling pathways in ovarian cancer cells co-cultured with M2 macrophages compared to single-cultures. Functional study (proliferation, migration, invasion, wound healing) were performed to determine the role of the M2 macrophage in ovarian cancer. RESULTS: Compared to single-cultured ovarian cancer cells, iNOS was downregulated in co-cultured with M2 macrophages, while PD-L1,CD206,TGF-b,MDR1,CSF-1 and Arg1 were upregulated. PD-L1 was also upregulated in M2 macrophages. Ovarian cancer cells co-cultured with M2 macrophages showed higher carboplatin resistance compared to single-cultured ovarian cancer cells. EMT-promoting related genes CD2,VIM, ZEB1 and SNAIL1 were upregulated in ovarian cancer cells co-cultured with M2 macrophages. Nanostring analysis revealed changes in the expression levels of genes associated with tumor signaling pathway activation and EMT. Ovarian cancer cells co-cultured with M2 macrophages performed functional study, we found that the functional abilities of the cancer cells were all significantly increased. CONCLUSION: We identified changes in the expression of various genes in ovarian cancer cells which were co-cultured with M2 macrophages, and identified upregulation of PD-L1 as a key factor in chemoresistance. We have also conducted additional nanostrings to refine the impact of M2 macrophage and ovarian cancer cell interactions on tumour signalling pathways as well as chemoresistance in the tumour microenvironment, and will be analysing these data and conducting further experiments. Citation Format: Jaesung Ryu, Baek MooJun, HyoWook Gil, Eunjung Yang, Kwangseock Kim, Taewan Kim, Kong Hyejeong, Beamjun Park, Seob Jeon. Role of M2 macrophages in chemoresistance about the tumor microenvironment of epithelial ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3432.