Identification of activated receptor tyrosine kinases that are important for motility, invasion, colony formation and proliferation in human osteosarcoma

Abstract

The prognosis for osteosarcoma (OS) remains poor, with 20‐30% of patients succumbing to pulmonary metastasis. Therefore, novel therapeutic agents are needed. In this study, we first screened for activated receptor tyrosine kinases (RTKs) in highly metastatic LM7 and 143B human osteosarcoma cell lines using a phospho‐RTK antibody array. In the LM7 cells, 12 of the 42 RTKs on the array were phosphorylated. Nine of the 12 RTKs were also phosphorylated in the 143B cells. siRNAs targeting the 12 RTKs found to be activated in the arrays were screened to identify the RTKs that are important for motility, invasion, colony formation and/or proliferation in OS cells. In 143B cells, Eph kinase B2 (EphB2) knockdown resulted in >85% inhibition of motility, invasion, colony formation and proliferation compared to cells treated with Luciferase control siRNA. Colony formation was also reduced by 70% in LM7 cells treated with EphB2 siRNA. Knockdown of EphA4 inhibited all 4 assays by >39% in the 143B cells. In the LM7 cell line, IGF‐1R silencing inhibited motility by 85%, colony formation by 58% and proliferation by 32%. Overall, EphB2, EphA4 and IG‐1R were activated in the metastatic cell lines and knockdown of these tyrosine kinases had the greatest effect on motility, invasion, colony formation and proliferation. These results indicate that EphB2, EphA4 and IGF‐1R may be valuable targets for the treatment of OS.