Abstract B67: Metadherin mediates osteosarcoma invasion and metastasis

Abstract

Abstract Osteosarcoma is the most common type of bone malignancy in children. It is a highly invasive mesenchymal tumor in which metastasis accounts for the vast majority of mortality and morbidity in patients. Understanding the mechanisms controlling metastasis in osteosarcoma and developing novel therapeutic options targeting metastasis are essential for improving patient survival in this disease. Recent studies have shown that Metadherin (MTDH) plays a key role in mediating metastasis in a variety of human cancers. This study examined the role of MTDH in osteosarcoma metastasis and elucidated the mechanisms underlying its oncogenic activity. We used western blot, qPCR, and flow cytometry to measure the expression of MTDH in a panel of osteosarcoma cell lines. Patient-derived osteosarcoma samples were also examined for MTDH expression using immunohistochemistry. In parallel experiments we used MTDH-specific shRNA to down-regulate endogenous MTDH expression, and blocked cell surface MTDH by anti-MTDH antibodies. The impact of MTDH inhibition was assessed in vitro using migration assays and matrigel invasion assays. We also developed an osteosarcoma orthotopic xenograft model of NOD/SCID/IL2Rγ-deficient mice through intratibial injection of osteosarcoma cells with or without MTDH knockdown to study the relationship between MTDH expression and pulmonary metastatic potential of osteosarcoma cells. Compared to normal human osteoblasts, all osteosarcoma cell lines tested displayed elevated MTDH expression as shown by western blot, qPCR and flow cytometry analyses. MTDH knockdown reduced migration and decreased invasion in matrigel. Inhibition of cell surface MTDH with an anti-MTDH antibody targeting the extracellular domain of MTDH also profoundly impeded osteosarcoma cell motility and invasiveness in vitro. In an orthotopic xenograft mouse model using CCHD cells, inhibition of MTDH delayed primary tumor growth and prohibited pulmonary metastasis. All mice in the control group developed lung metastases while fewer than 20% of the mice in the MTDH-knockdown group showed sign of metastasis at six weeks after inoculation. MTDH knockdown also reduced mean lung weight and mean number of pulmonary metastasis. Immunohistochemical analysis of tumor samples showed that lung metastases had elevated MTDH expression level compared to primary tumors. Altogether these studies suggested that MTDH plays a critical role in promoting pulmonary metastasis of osteosarcoma and may serve as an attractive target for therapeutic intervention. Citation Format: Limin Zhu, Adrianna S. Buford, Yanwen Yang, Pingyu Zhang, Wei-Lien Wang, Dennis P. Hughes. Metadherin mediates osteosarcoma invasion and metastasis. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr B67.