XB130 Knockdown Inhibits the Proliferation, Invasiveness, and Metastasis of Hepatocellular Carcinoma Cells and Sensitizes them to TRAIL-Induced Apoptosis

Background: XB130 is a recently discovered adaptor protein that is highly expressed in many malignant tumors, but few studies have investigated its role in hepatocellular carcinoma (HCC). Therefore, this study explored the relationship between this protein and liver cancer and investigated its molecular mechanism of action. Methods: The expression of XB130 between HCC tissues and adjacent nontumor tissues was compared by real-time polymerase chain reaction, immunochemistry, and Western blotting. XB130 silencing was performed using small hairpin RNA. The effect of silencing XB130 was examined using Cell Counting Kit-8, colony assay, wound healing assay, and cell cycle analysis. Results: We found that XB130 was highly expressed in HCC tissues (cancer tissues vs. adjacent tissues: 0.23 +/- 0.02 vs. 0.17 +/- 0.02, P < 0.05) and liver cancer cell lines, particularly MHCC97H and HepG2 (MHCC97H and HepG2 vs. normal liver cell line LO-2: 2.35 +/- 0.26 and 2.04 +/- 0.04 vs. 1.00 +/- 0.04, respectively, all P < 0.05). The Cell Counting Kit-8 assay, colony formation assay, and xenograft model in nude mice showed that silencing XB130 inhibited cell proliferative ability both in vivo and in vitro, with flow cytometry demonstrating that the cells were arrested in the G0/G1 phase in HepG2 (HepG2 XB130-silenced group [shA] vs. HepG2 scramble group [NA]: 74.32 +/- 5.86% vs. 60.21 +/- 3.07%, P < 0.05) and that the number of G2/M phase cells was decreased (HepG2 shA vs. HepG2 NA: 8.06 +/- 2.41% vs. 18.36 +/- 4.42%, P < 0.05). Furthermore, the cell invasion and migration abilities were impaired, and the levels of the epithelial-mesenchymal transition-related indicators vimentin and N-cadherin were decreased, although the level of E-cadherin was increased after silencing XB130. Western blotting showed that the levels of phosphorylated phosphoinositide 3-kinase (PI3K) and phospho-protein kinase B (p-Akt) also increased, although the level of phosphorylated phosphatase and tensin homolog increased, indicating that XB130 activated the PI3K/Akt pathway. Furthermore, we found that a reduction in XB130 increased liver cancer cell sensitivity to tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis. Conclusions: Our findings suggest that XB130 might be used as a predictor of liver cancer as well as one of the targets for its treatment.