Expression of Carbonic Anhydrase IX Correlates with Histologic Grade and Metastasis in Osteosarcoma

ABSTRACT

BACKGROUND: Carbonic anhydrase IX (CA9) is reportedly overexpressed in several types of carcinomas, but little is known about the expression pattern of CA9 in osteosarcoma. We aimed to assess the prevalence of CA9 expression and its prognostic implications in osteosarcoma patients. METHODS: We compared immunohistochemical expression of CA9 between conventional, high-grade and low-grade, central osteosarcomas. Specimens were obtained before chemotherapy and stained with anti-human CA9 antibody. We also evaluated the histologic grade, presence of metastasis, and patient prognosis. RESULTS: Among 38 samples of conventional high-grade osteosarcoma, 22 (57.9%) tumors displayed CA9 overexpression. Twenty-five cases of low-grade central osteosarcomas were all negative (p < 0.0001). CA9 expression was significantly associated with the presence of metastasis (p = 0.0010). The overall survival rate was significantly reduced with increased CA9 expression (p = 0.0012), higher histologic grade (p < 0.0001), and younger age (p = 0.0140). However, the overall survival rate was not significantly correlated with gender, tumor size, or American Joint Committee on Cancer stage. CONCLUSIONS: CA9 expression is a frequent and tumor-specific event in osteosarcoma. CA9 expression is associated with higher grade tumors, metastasis and poor prognosis for the osteosarcoma patients.