Overexpression of centromere protein K (CENP-K) gene in hepatocellular carcinoma promote cell proliferation by activating AKT/TP53 signal pathway

Hepatocellular carcinoma (HCC) is one of the high-incidence malignant tumors with very poor prognosis. Identification of potential oncogenes is critical to discovering novel therapeutic targets for many cancers, including HCC. In our previous studies, using microarray technology, we conformed that CENP-K was overexpressed in HCCs. However, whether the overexpression of CENP-K contributes to hepatocarcinogenesis remains unclear. In this study, we found that CENP-K was significantly up-regulated in 60% (63 of 105) of HCC specimens at the mRNA level compared to adjacent non-cancerous liver specimens, as determined by RT-qPCR. Immunohistochemical staining confirmed similar results at the protein level. Interestingly, we found that the DNA methylation status of the CENP-K promoter was significantly reduced in HCC specimens with increased CENP-K expression. In addition, CENP-K mRNA expression level was positively correlated with the level of alpha-fetoprotein (AFP) (>= 400 ng/ml) and tumor size (>= 3 cm) (p < 0.05). CENP-K overexpression promoted proliferation and migration in SMMC7721 and Focus cells. In contrast, knock down of CENP-K significantly inhibited the growth of MHCC-LM3 and QGY7703 cells. Furthermore, we found that overexpression of CENP-K stimulated the tyrosine phosphorylation of the AKT and MDM2 proteins, but inhibited tyrosine phosphorylation of the TP53 protein. Our data suggest that the up-regulation of CENP-K, a potential oncotarget gene, may be modulated by epigenetic events and can contribute to hepatocarcinogenesis.