Tenascin-C as a prognostic biomarker in osteosarcoma? Treating metastatic osteosarcoma has been challenged in past decades. Extracelluar matrix (ECM) proteins play an important role in the progression of osteosarcoma as they are pivotal components of the tumor microenvironment. Here, we identified potential genes belonging to the ECM and characterized the roles of these genes in the progression of osteosarcoma and their association with outcomes.Osteosarcoma parental cell line MG63 and its derivative MG63-A1 with a high metastatic potential underwent oligonucleotide microarray analysis. Gene ontology analysis was used to screen deregulated genes between the 2 cell lines which were either upregulated or downregulated by more than 4 fold, particularly focusing on mRNAs encoding extracellular matrix proteins. The expression of resulting candidate genes was then validated by reverse transcription-PCR for mRNA expression as well as Western blotting for protein expression. Immunohistochemistry was performed on 37 osteosarcoma specimens to examine the potential role of the candidate genes in a clinical context.Microarray data and gene ontology analysis showed that Tenascin-C, a critical component of the ECM, is significantly down-regulated in the highly metastatic cell line MG63-A1 compared with the parental osteosarcoma cell line MG63-wt. This finding was validated at mRNA and protein levels. Immunohistochemical analysis found that Tenascin-C is located in the intercellular space in osteosarcoma specimens. Furthermore, low-grade Tenascin-C expression (less than 20%) in osteosarcoma specimens was associated with poor survival.Tenascin-C expression level correlates with the survival of osteosarcoma patients. Its biological functional role and underlying molecular mechanisms in the progression of osteosarcoma needs further investigation.