Effects of Cyclooxygenase-2 in Canine Melanoma-derived Extracellular Vesicles on Tumor Microenvironment in Vitro

Background/Aim: Tumor cell-derived extracellular vesicles (TEVs) promote tumor growth and metastasis; thus, they have drawn the attention of researchers. TEVs regulate the tumor microenvironment by facilitating crosstalk between immune and stromal cells. Macrophages are one of the key components involved in malignant behavior in melanomas. Generally, when activated, macrophages polarize into M1 (pro-inflammatory) or M2 (anti-inflammatory, pro-tumor) phenotypes. However, the role of canine melanoma-derived EVs in macrophage polarization is elusive. In this study, we aimed to analyze the pro- and anti-inflammatory cytokines that are common markers for M1 or M2 macrophages in vitro. Materials and Methods: The analysis was performed under coculture conditions of canine melanoma-derived (LMeC) EVs with canine macrophages (DH82). Quantitative reverse transcription polymerase chain reaction, western blotting, and immunofluorescence were used. Results: Canine melanoma-derived EVs polarized M1 macrophages (inducible nitric oxide synthase, tumor necrosis factor α) into M2 macrophages [cluster of differentiation (CD)206, interleukin-10] and cyclooxygenase-2 is a major factor in macrophage polarization in canine melanoma-derived EVs. Furthermore, we also found that melanoma-derived EVs induced the expression of angiogenic cytokines (vascular endothelial growth factor, transforming growth factor β) in endothelial cells. Conclusion: Melanoma-derived EVs perform an immunomodulatory function and can be used as targets in anti-inflammatory treatment.