Abstract: Background and purpose: B7-H3 is a newly identified member of the B7-family of co-stimulatory molecule, and however, its exact role in human osteosarcoma is still unclear. The purpose of this study was to examine the expression of B7-H3 in osteosarcoma tissues and to investigate its correlations with clinicopathological factors and overall survival in patients with osteosarcoma. Methods: The expression of B7-H3 and the intensity of tumorinfiltrating T lymphocytes (TILs) in pathologic specimens of osteosarcoma, osteochondroma and bone fibrous dysplasia tissues were evaluated by immunohistochemical assay. Results: The expression rate of B7-H3 was 91.8% (56/61) in osteosarcoma lesions, while B7-H3 was barely expressed in adjacent normal tissues and bone fibrous dysplasia tissues. The intensity of B7-H3 expression in osteochondroma was 56.8%, which was significantly decreased compared with osteosarcoma tissues. Tumor B7-H3 expression was associated with Ennecking stage and pulmonary metastasis, while inversely correlated with the number of tumor-infiltrating CD8⁺ T cells (P<0.05). Moreover, patients with high tumor B7-H3 levels had a significantly shorter survival time and recurrence time than patients with low tumor B7-H3 levels (P<0.05). Conclusion: B7-H3 is overexpressed in human osteosarcoma tissues, and B7-H3 expression is highly correlated with tumor development and overall patients’ prognosis. Moreover, overexpression of B7-H3 in tissues can reflect CD8⁺ T cell infiltration and may help tumor cells avoid immune surveillance.

Key words: B7-H3, Osteosarcoma, Immunohistochemistry