Osteosarcoma (OS) mainly occurs in children and adolescents, and has a high propensity for lung metastasis. Little is known about the role of SDF-1/CXCR4 axis in OS progression. AMD3100 is a specific CXCR4 antagonist. Triptolide can induce apoptosis and proliferation inhibition in various cancer cell lines.

This work aimed to investigate the effects of AMD3100 plus triptolide on the proliferation, apoptosis, invasion and metastasis of OS cells.

The expression levels of SDF-1 and CXCR4 in five OS cell lines was analyzed by qRT-PCR, western blotting and ELISA assays. The effect of AMD3100 and triptolide on the proliferation, apoptosis and invasion of U2OS cells was evaluated by CCK-8, flow cytometry and transwell assay, respectively. Orthotopic intra-tibial growth and lung metastasis mouse model of OS were employed to evaluate the inhibition effect of AMD3100 and triptolide on primary OS growth and lung metastasis.

CXCR4 protein expression was detected in HOS-8603, MG-63, U2OS and 143B but not Saos2 cells, and all these cell lines expressed SDF-1. AMD3100 plus triptolide induced proliferation inhibition and apoptosis of U2OS cells, which was attributed to the downregulation of c-Myc, survivin, cyclin D1 and increased cleaved caspase-3 and PARP. AMD3100 and triptolide also suppressed SDF-1 induced invasion of CXCR4+ U2OS cells, which was validated by decreased expression of MMP-2 and 9, VEGF, m-Calpain and β-catenin. Moreover, the phosphorylation levels of Erk1/2, Akt and STAT3, as well as the nuclear translocation and phosphorylation of NF-κB p65 in U2OS cells were also reduced by AMD3100 and triptolide. In vivo, AMD3100 and triptolide significantly reduced primary tumor growth and lung metastasis of U2OS cells.

AMD3100 combined with triptolide can reduce proliferation and metastasis, and induce apoptosis of U2OS cells, which may be related to the Erk1/2, Akt, STAT3 and NF-κB pathways.