Spondin 1 promotes metastatic progression through Fak and Src dependent pathway in human osteosarcoma

Spondin 1 (SPON1) is cell adhesion protein that involved in attachment of sensory neuron cells and outgrowth of neurites. Its cellular functions and related mechanisms in cancers, however, remain largely unexplored. In this study, we first identified that SPON1 acts a critical factor in the metastatic progression of osteosarcoma through analysis of a GEO dataset. Then we demonstrated that SPON1 was significantly up-regulated in 72 osteosarcoma specimens compared with benign osteochondroma samples and elevated SPON1 was positively correlated with MMP9 expression. Knockdown of SPON1 expression in two metastatic osteosarcoma cell lines, HKOS and KRIB, dramatically suppressed cell migration and invasion. Treatment with recombinant SPON1 protein in two non-metastatic osteosarcoma cell lines, HOS and U2OS, significantly promoted cell migration and invasion in vitro. Meanwhile, suppression of SPON1 in KHOS cells resulted in decreased pulmonary metastasis in vivo. Mechanistically, we determined that the effects of SPON1 on osteosarcoma cell motility were primarily mediated through Fak and Src dependent pathway. Taken together, our study provides evidence of the contributions of SPON1 and the Fak and Src signaling to the progression of osteosarcoma and suggests that this axis may represent a potential therapeutic target for osteosarcoma.