Involvement of cancer biomarker C7orf24 in the growth of human osteosarcoma. Up-regulation of the expression of the gene C7orf24, encoding γ-glutamyl cyclotransferase, is a common event in cancers derived from various tissues, but its involvement in osteosarcomas (OS) has not yet been demonstrated.The expression of C7orf24 was analyzed in human OS cell lines and primary tumor samples. The biological effects of C7orf24 on growth, motility, and invasion in the OS cell lines were investigated using siRNA for C7orf24. Genes related to the function of C7orf24 were sought by genome-wide gene expression profiling.The level of C7orf24 expression was much higher in the OS cell lines and OS primary tumors than in normal osteoblasts. Down-regulation of C7orf24 expression inhibited the growth of the cell lines in association with enhancement of cell-clustering. Treatment with C7orf24-siRNA inhibited cell motility and invasion. Gene ontology suggested the function of C7orf24 to be related to cell adhesion and protein transport.C7orf24 is also involved in the growth of OS, and is a potential biomarker for this type of tumor.