CX3CR1-Dependent Macrophages Drive Ovarian Cancer Progression Through MMP-2 and TGF-β Production

Background: Epithelial ovarian cancer (EOC) is characterized by aggressive peritoneal dissemination and an immunosuppressive tumor microenvironment in which tumor-associated macrophages (TAMs) play a central role. Chemokine signaling pathways regulate macrophage recruitment and function; however, the contribution of the CX3CL1-CX3CR1 axis to ovarian cancer progression and TAM-mediated effector mechanisms remains unclarified. This study aimed to clarify the role of CX3CL1-CX3CR1 signaling in ovarian cancer progression, focusing on macrophage-derived pro-tumorigenic factors. Methods: CX3CL1 and CX3CR1 expression was examined in human EOC and healthy ovarian tissues by real-time polymerase chain reaction and immunohistochemistry. Functional effects of CX3CL1 on ovarian cancer cells were evaluated via migration and proliferation assays in the murine ID8 cell line. An intraperitoneal syngeneic ovarian cancer model was established by injecting ID8 cells into wild-type and Cx3cr1-deficient mice. Tumor burden, ascites formation, survival, macrophage infiltration, and expression levels of matrix metalloprotease-2 (MMP-2) and transforming growth factor-β (TGF-β) were assessed by histological, immunohistochemical, and molecular analyses. Results: CX3CL1 and CX3CR1 expression was significantly upregulated in human EOC tissues and associated with marked macrophage infiltration. CX3CL1 stimulation enhanced migration, but not proliferation, of ID8 cells. Cx3cr1 deficiency significantly suppressed intraperitoneal tumor growth, reduced ascitic fluid volume, and prolonged survival. This was accompanied by reduced CX3CR1⁺ TAM accumulation and decreased MMP-2 and TGF-β expression, which were predominantly produced by infiltrating macrophages. Conclusions: The CX3CL1-CX3CR1 axis promotes ovarian cancer progression by recruiting MMP-2- and TGF-β-producing macrophages. Targeting CX3CR1-dependent TAM functions may represent a therapeutic strategy for limiting peritoneal dissemination in ovarian cancer.