Clinical significance and biological function of co-stimulation molecule B7 homolog 6 expression in human hepatocellular carcinoma

Abstract

Objective To investigate the clinical significance and biological function of co-stimulatory molecule B7 homolog 6 (B7-H6) in human hepatocellular cancer. Methods The immunohistochemistry assay and the tissue micro-array were used to examine the B7-H6 expression in hepatocellular cancer tissues. The correlation between the expression level of B7-H6 and patients’ clinic pathological parameters was evaluated by using chi-square test. Down-regulation of B7-H6 was performed by using RNA interference (RNAi) method to investigate the role of B7-H6 in regulation of biological behaviors in human hepatocellular cancer cell lines HepG2 and SMMC-7721. The cell counting kit-8 (CCK-8) assay, wound healing assay, and Transwell assay were used to examine the cellular function after B7-H6 knockdown of these cells. Results The B7-H6 expression level in hepatocellular cancer tissues was significantly correlated with patients’ age (χ2=5.943, P<0.05) and tumor size (χ2=4.519, P<0.05). Next, to investigate the functions of B7-H6 in human hepatocellular cancer, we successfully constructed B7-H6 knockdown expression human hepatocellular cell lines using the RNA interference technology. CCK-8 assay showed that decreased B7-H6 expression in human hepatocellular cancer lines HepG2 and SMMC-7721 significantly attenuated cell proliferation (HepG2, 48 h: 0.413±0.020 vs. 0.572 ±0.025, t=4.951, P<0.05; 72 h: 0.503±0.014 vs. 0.691±0.018, t=8.372, P<0.01; SMMC-7721, 48 h: 0.534± 0.001 vs. 0.656±0.021, t=5.869, P<0.05; 72 h: 0.650± 0.044 vs. 0.856±0.025, t=4.069, P<0.05). The wound healing assay showed that decreased B7-H6 expression in human hepatocellular cancer lines HepG2 and SMMC-7721 significantly attenuated cell migration (HepG2, 24 h: t=4.581, P<0.05, 36 h: t=5.040, P<0.01; SMMC-7721, 36 h: t=5.118, P<0.01). The Transwell assay showed that decreased B7-H6 expression in human hepatocellular cancer lines HepG2 and SMMC-7721 significantly attenuated cell invasion (HepG2, 24 h: t=6.824, P<0.01, 36 h: t=11.030, P<0.001; SMMC-7721, 24 h: t=10.180, P<0.001, 36 h: t=10.340, P<0.001). Conclusion B7-H6 had important effect in initiation and development of human hepatocellular cancer. Key words: B7 homolog 6; Liver cancer; Immunohistochemistry; RNA interference; Tissue microarray