Enhanced UV Resistance Role of Death Domain-Associated Protein in Human MDA-MB-231 Breast Cancer Cells by Regulation of G2 DNA Damage Checkpoint.

PURPOSE: Death domain-associated protein (DAXX) is a multifunctional nuclear protein involved in apoptosis, transcription, deoxyribonucleic acid damage response, and tumorigenesis. However, the role of DAXX in breast cancer development and progression remains elusive. In this study, we examined the expression patterns and function of DAXX in human breast cancer samples and cell lines. METHODS: Immunohistochemistry was used to analyze the expression and localization patterns of DAXX. Additionally, we investigated whether DAXX played an intrinsic role in the cellular response to damage induced by ultraviolet (UV) irradiation in MDA-MB-231 breast cancer cells (isolated at M D Anderson from a pleural effusion of a patient with invasive ductal carcinoma). RESULTS: Our results showed that nucleus size, chromatin organization, and DAXX localization were altered in breast cancer tissues compared with those in control tissues. Compared with cytoplasmic and nuclear expression in benign breast tissues, DAXX was colocalized with promyelocytic leukemia in nuclei with a granular distribution. Endogenous DAXX messenger ribonucleic acid levels were upregulated upon UV radiation in MDA-MB-231 cells. DAXX-deficient cells tended to be more sensitive to irradiation than control cells. Conversely, DAXX-overexpressing cells exhibited reduced phosphorylated histone H2AX (γ-H2AX) accumulation, increased cell survival, and resistance to UV-induced damage. The protective effects of DAXX may be related to the activation of the ataxia telangiectasia mutated (ATM)-checkpoint kinase 2 (ATM-CHK2)-cell division cycle 25c (CDC25c) signaling pathways in Gap2/Mitosis (G2/M) checkpoint and ultimately cell cycle arrest at G2/M phase. CONCLUSIONS: Taken together, these results suggested that DAXX may be an essential component in breast cancer initiation, malignant progression, and radioresistance.

Screening Hub Genes as Prognostic Biomarkers of Hepatocellular Carcinoma by Bioinformatics Analysis.

Hepatocellular carcinoma (HCC) is a widespread, common type of cancer in Asian countries, and the need for biomarker-matched molecularly targeted therapy for HCC has been increasingly recognized. However, the effective treatment for HCC is unclear. Therefore, identifying additional hub genes and pathways as novel prognostic biomarkers for HCC is necessary. In this study, the expression profiles of GSE121248, GSE45267 and GSE84402 were obtained from the Gene Expression Omnibus (GEO), including 132 HCC and 90 noncancerous liver tissues. Differentially expressed genes (DEGs) between HCC and noncancerous samples were identified by GEO2 R and Venn diagrams. In total, 109 DEGs were identified in these datasets, including 24 upregulated genes and 85 downregulated genes. Subsequently, Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) preliminary analyses of the DEGs were performed using DAVID. The protein-protein interaction (PPI) network of the DEGs was constructed with the Search Tool for the Retrieval of Interacting Genes (STRING) and visualized in Cytoscape. Module analysis of the PPI network was performed using MCODE to get hub genes. Moreover, the influence of the hub genes on overall survival was determined with Kaplan-Meier plotter. All hub genes were analyzed by Gene Expression Profiling Interactive Analysis (GEPIA) and KEGG. Overall, the hub genes DTL, CDK1, CCNB1, RACGAP1, ECT2, NEK2, BUB1B, PBK, TOP2A, ASPM, HMMR, RRM2, CDKN3, PRC1, and ANLN were upregulated in HCC, and the survival rate was lower for HCC with increased expression of these hub genes. CCNB1, CDK1, and RRM2 were enriched in the p53 signaling pathway, and CCNB1, CDK1, and BUB1B were enriched in the cell cycle. In brief, we screened 15 hub genes and pathways to identify potential prognostic markers for HCC treatment. However, the specific occurrence and development of HCC with expression of the hub genes should be verified in vivo and in vitro.