The protein tyrosine kinases (PTKs) are a group of enzyme proteins that can phosphorylate substrate protein tyrosine residues,and are involved in many signal transduction pathways.They also play an important role in the control of cell differentiation,proliferation,and spreading.A recent study has found that Syk,as a tumor suppressor of PTKs,is closely related to tumor invasion and metastasis [1].Syk has been also showed to have potential inhibitory effect in breast,gastric,and pancreatic cancers [2-4].Sung et al.[5]found that in the mouse mammary gland,loss of one Syk allele profoundly increased proliferation,ductal branching,and invasion of epithelial cells through the mammary fat pad during puberty,and that mammary carcinoma developed after 1 year.An increasing number of clinical studies have revealed a correlation between reduced Syk expression and increased risk of metastasis formation,and Syk is assigned as a potential new prognostic marker in different tumor types [6].In this study,we examined the expression of Syk in non-small-cell lung cancer (NSCLC) and analyzed its association with the prognosis.