The metastatic role of the CXCL10-CXCR3 axis and its therapeutic potential in osteosarcoma.

The CXCL10-CXCR3 axis regulates immunity, tumorigenesis, and metastasis in multiple cancers. Yet, its roles in osteosarcoma (OS), the predominant pediatric malignant bone tumor, are not fully defined. Our prior work has shown that elevated serum CXCL10 levels correlate with poor OS prognosis. The current study delves deeper by investigating how CXCL10-mediated CXCR3 signaling influences OS growth and metastatic spread. In vitro, CXCL10 and related CXCR3 ligands (CXCL4, CXCL9, and CXCL11) enhanced OS tumor cell migration. In an orthotopic xenograft mouse model with a newly created CXCR3 knockout (KO) mutant, tumor growth and lung metastasis decreased significantly when compared with the parental cell line. Transfecting the transcript isoform CXCR3A, but not CXCR3B, into KO cells restored metastatic phenotypes in mice, highlighting isoform specificity. Pharmacological CXCR3 inhibition reduced OS cell migration in vitro and metastasis in vivo. Mechanistically, CXCL10 triggered AKT (S473) and PAK1 (S144) phosphorylation in OS cell lines, but not in the KO mutant, implicating the role of these kinases in CXCL10-mediated metastasis. Collectively, our data indicate the CXCL10-CXCR3 axis as a key metastatic driver in OS, suggesting CXCR3 as a viable therapeutic target for treating OS metastasis.