The Dual Roles of the CXCL10-CXCR3 Axis and Its Therapeutic Potential in Osteosarcoma

The CXCL10-CXCR3 axis is recognized for its dual role in tumor biology, promoting tumor growth and metastasis via autocrine signaling while also eliciting anti-tumor responses through paracrine signaling. However, its specific functions in osteosarcoma (OS), the most prevalent malignant bone tumor in children, remain poorly understood. Our previous research has demonstrated that elevated circulating CXCL10 levels correlate with poor prognosis in OS patients. Analysis of the TARGET OS RNAseq dataset revealed that high expression levels of CXCL10 or its receptor CXCR3 are associated with improved prognosis. Given the known role of CXCL10 in recruiting CXCR3+ immune cells to combat cancer, we further analyzed single-cell RNAseq data and found that CXCR3 is predominantly expressed in CD3+ T cell populations. These findings suggest that CXCL10 may also play a protective role in OS by recruiting anti-tumor immune cells. To elucidate the causal role of the CXCL10-CXCR3 axis in OS, we conducted in vitro phenotypic assays on three OS cell lines with and without CXCL10. The chemokine was found to enhance tumor cell migration and AKT phosphorylation. Utilizing a CRISPR-mediated CXCR3 deletion mutant, we demonstrated that the absence of CXCR3 significantly inhibited OS tumor growth and pulmonary metastasis in an orthotopic xenograft mouse model. Transfection with the CXCR3A isoform, but not the CXCR3B isoform, restored the migratory phenotype of the CXCR3 deletion mutant to levels comparable to the parental cell line. Additionally, pharmacological inhibition of CXCR3 with AMG487 markedly reduced OS cell migration in vitro and metastasis development in the orthotopic xenograft mouse model. Our research highlights the complex interplay of the CXCL10-CXCR3 axis in both tumor and immune cells. We propose a working model for the roles of the CXCL10-CXCR3 axis in OS, suggesting that targeting CXCR3 may be an effective strategy to inhibit OS metastasis, particularly in immune-cold OS subtypes.