【Objective】 Spleen tyrosine kinase (SYK) has two isoforms

full-length form SYK(L) and short form SYK(S)

which has different roles in human malignant tumor. The reports of SYK(L) in HCC are few. This study was to generate SYK(L)-specific antibody

and investigate the correlation between the expression pattern of SYK(L) protein in HCC and clinicopathological characteristics and prognosis. 【Methods】 SYK(L)-specific antibody was generated by a biotech company. The expression of SYK(L) was detected in 162 cases of HCC tissues and adjacent non-tumor liver tissues by immunohistochemistry. The relationship between the expression statues of SYK(L) and clinicopathological characteristics and prognosis was analyzed. 【Results】 The specificity of SYK(L)-specific antibody (SYK-23) was well. The positive rate of SYK(L) was significantly lower in HCC tissues [64.8% (105/162)] than that in adjacent non-tumor tissues [98.1% (159/162)](P < 0.001); moreover

SYK(L) expression was significantly associated with the tumor size

tumor differentiation

satellite nodule and vascular invasion (all P < 0.05). After resection of primary HCC

the patients with SYK(L)-positive tumors had a significant longer recurrence-free survival (RFS) and overall survival (OS) than those with SYK(L)-negative tumors. The multivariate cox proportional hazards regression analysis of prognostic factors for RFS and OS showed that the expression of SYK(L) was an independent factor for prognosis of HCC. 【Conclusion】 Down-regulation of SYK(L) protein expression may be involved in the carcinogenesis and metastasis of HCC

and is a powerful molecular marker to predict the HCC prognosis.