Purpose: This study aimed to explore the expression of the C-type lectin domain family 4 member G (CLEC4G) gene in the liver sinusoidal endothelial cells (LSECs) during liver pathogenesis, and to evaluate its correlation with CD34 and clinical significance in hepatocellular carcinoma patients.
Methods: We conducted bioinformatics analysis of the differential expression of CLEC4G in in various human organs, carcinomatous and adjacent tissues. Then, the differential expression in carcinomatous and adjacent tissues was verified by real-time quantitative reverse transcription PCR (qRT-PCR) and immunohistochemical (IHC) analyses in clinical HCC samples. The expression of CLEC4G in normal liver tissues and cirrhotic tissues was further detected. Besides, mRNA and protein expression levels of CD34 in HCC samples were detected via qRT-PCR and IHC, respectively. ELISA was applied to detect serum levels of CLEC4G in healthy controls, liver fibrosis and HCC patients. The correlation between the CLEC4G and CD34 expression was analyzed using the Spearman test, whereas the Chi-square test was applied to analyze the correlation between CLEC4G and clinicopathological characteristics of HCC patients. Furthermore, the Kaplan-Meier method was used to estimate the relationship between CLEC4G serum levels and survival.
Results: The expressions of mRNA and protein levels of CLEC4G were higher in normal liver tissues, moderately expressed in cirrhotic and para-cancerous tissues (P<0.001), and lowest in HCC tissues (P<0.001). We also found high CD34 expression in late tumors, which was negatively correlated with CLEC4G at both mRNA and protein levels (R=-0.830, P<0.001; R=-0.817, P<0.001, respectively). Compared to the healthy controls, the CLEC4G levels in liver fibrosis patients, and HCC patients were gradually lower (P<0.001). Furthermore, CLEC4G was highly associated with tumor size (P=0.023), tumor stage (P=0.046), and vascular metastasis (P=0.008; Table 1) in HCC patients. Notably, HCC patients expressing low CLEC4G levels were characterized by a shorter survival time (P=0.032).
Conclusions: The low expression of CLEC4G is potentially correlated with LSEC capillarization and the appearance of micro-vessels. Such a phenomenon may exert an endogenous protective effect against the progression of liver disease and serve as a reliable diagnostic marker for hepatocellular carcinoma.