LAMP3 promotes the invasion of osteosarcoma cells via SPP1 signaling.

Osteosarcoma is the most common type of primary bone cancer in children and young adults. The prognosis of osteosarcoma is very poor when it is diagnosed with metastasis. Lysosomal‑associated membrane protein 3 (LAMP3) is a tumor‑specific protein induced by hypoxia, which stimulates invasion and metastasis of various cancer cells via hypoxia‑inducible factor (HIF). A previous study from our group has reported that expression of LAMP3 is significantly increased in lung metastatic osteosarcoma compared with primary osteosarcoma using microarray analysis, suggesting that LAMP3 may be involved in metastatic osteosarcoma. The present study therefore aimed to investigate the role of LAMP3 in osteosarcoma metastasis. Knockdown of LAMP3 decreased the invasion of two osteosarcoma cell lines in vitro. Furthermore, knockdown of LAMP3 increased the expression of secreted phosphoprotein 1 (SPP1), cadherin 1, and keratin 19, while it decreased the expression of matrix metallopeptidase 2, collagen type III α 1, twist family bHLH transcription factor 1 and cadherin 2. Concurrent knockdown of SPP1 and LAMP3 attenuated the changes in gene expression profile induced by LAMP3 knockdown alone. Gene ontology and KEGG analysis demonstrated that SPP1 was involved in cell adhesion, focal adhesion, and extracellular matrix‑receptor interaction. In conclusion, the present results suggest that LAMP3 may be involved in the invasion and metastasis of osteosarcoma via regulating signaling downstream of SPP1. Thus, LAMP3/SPP1 signaling may serve as a potential target in the future to prevent osteosarcoma metastasis.