Osteopontin derived from tumor-associated macrophages modulates radiosensitivity of oral squamous cell carcinoma via reactive oxygen species production

This study investigated the role of osteopontin (OPN), a secreted phosphoglycoprotein, in radioresistance in oral squamous cell carcinoma (OSCC). Samples were collected from 66 patients with OSCC. Immunohistochemistry and double staining were performed on tissue sections to assess OPN levels in stromal and tumor cells and OPN and CD163 colocalization, respectively. Cell lines were treated to simulate cancer-associated environments. Macrophage and fibroblast differentiation were induced; enzyme-linked immunosorbent assays, in situ hybridization, and western blotting were performed; and reactive oxygen species (ROS) were detected to evaluate protein levels and cell responses. Cells were also irradiated for survival analysis. Immunohistochemical analysis of OSCC tissue samples revealed OPN localization predominantly in the tumor stroma, particularly in tumor-associated macrophages (TAMs). In vitro experiments demonstrated that TAM-like cells differentiated from THP-1 monocytes secreted higher OPN levels compared with cancer-associated fibroblast-like cells. Clinicopathological analysis revealed a significant correlation between high OPN expression and poor chemoradiotherapy response. The addition of recombinant OPN to OSCC cell lines decreased radiosensitivity, which was reversed by blocking OPN signaling using anti-CD44 and anti-integrin αVβ3 antibodies. Furthermore, OPN treatment reduced radiation-induced DNA double-strand breaks and ROS production and increased glutathione levels, which were inhibited by blocking OPN-CD44 and OPN-integrin αVβ3 pathways. OPN secreted by the tumor stroma, particularly TAMs, contributes to OSCC radioresistance by regulating ROS and GSH levels via the OPN-CD44 and OPN-integrin αVβ3 axes. Therefore, targeting OPN signaling may represent a novel therapeutic strategy for overcoming radioresistance in OSCC.