RESUMEN
BACKGROUND: Hepatocellular carcinoma (HCC) is one of the deadliest tumors. The majority of HCC is detected in the late stage, and the clinical results for HCC patients are poor. There is an urgent need to discover early diagnostic biomarkers and potential therapeutic targets for HCC. METHODS: The GSE87630 and GSE112790 datasets from the Gene Expression Omnibus (GEO) database were downloaded to analyze the differentially expressed genes (DEGs) between HCC and normal tissues. R packages were used for Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analyses of the DEGs. A Search Tool for Retrieval of Interacting Genes (STRING) database was used to develop a protein-protein interaction (PPI) network, and also cytoHubba, Molecular Complex Detection (MCODE), EMBL-EBI, CCLE, Gene Expression Profiling Interactive Analysis (GEPIA), and Oncomine analyses were performed to identify hub genes. Gene expression was verified with a third GEO dataset, GSE25097. The Cancer Genome Atlas (TCGA) database was used to explore the correlations between the hub genes and clinical indexes of HCC patients. The functions of the hub genes were enriched by gene set enrichment analysis (GSEA), and the biological significance of the hub genes was explored by real-time polymerase chain reaction (qRT-PCR), western blot, immunofluorescence, CCK-8, colony formation, Transwell and flow cytometry assays with loss-of-function experiments in vitro. RESULTS: Centromere protein N (CENPN) was screened as a hub gene affecting HCC tumorigenesis. Evaluation by Cox regression showed that a high level of CENPN expression was an independent danger variable for poor prognosis of HCC. GSEA showed that high CENPN expression was linked to the following pathways: liver cancer subclass proliferation, cell cycle, p53 signaling pathway, Rb1 pathway, positive regulation of cell cycle G1/S phase transition, and DNA damage response signal transduction by p53 class moderators. Further cell experiments showed that knocking down CENPN expression decreased the proliferation and colony-forming abilities of HepG2 and Huh7 cells as well as Ki67 expression in these cell lines. The cell cycle was arrested in G1 phase, which is consistent with previous experiments on CENPN downregulation., but neither migration nor invasion were significantly affected. Western blot results revealed that the expression of p53, p27, p21, CDK4, cyclin D1, CDK2, cyclin E, pRb, E2F1 and c-myc decreased after CENPN knockdown, but there was no significant change in total Rb levels. In addition, CENPN-knockdown cells subjected to irradiation showed significantly enhanced of γ-H2AX expression and reduced colony formation. CONCLUSION: CENPN functions as an oncogene in HCC and may be a therapeutic target and promising prognostic marker for HCC.
RESUMEN
Centromere protein N (CENP-N), an important member of the centromere protein family, is essential for kinetochore assembly and chromosome segregation; however, the relevance of CENP-N in cancers remains unknown. The aim of this study was to investigate CENP-N expression and its functional mechanisms in oral squamous cell carcinoma (OSCC). CENP-N expression was up-regulated significantly in vitro and in vivo in OSCCs. Overexpressed CENP-N was closely (p < 0.05) correlated with tumor growth using quantitative reverse transcriptase-polymerase chain reaction, immunoblot analysis, and immunohistochemistry. CENP-N knockdown (shCENP-N) cells showed depressed cellular proliferation by cell-cycle arrest at the G1 phase with up-regulation of p21Cip1 and p27Kip1 and down-regulation of cyclin D1, CDK2, and CDK4. Interestingly, we newly discovered that calcitriol (1, 25-dihydroxyvitamin D3) controlled the CENP-N expression level, leading to inhibition of tumor growth similar to shCENP-N cells. These results suggested that CENP-N plays a critical role in determining proliferation of OSCCs and that calcitriol might be a novel therapeutic drug for OSCCs by regulating CENP-N.