Identification of RRAS gene related to nasopharyngeal carcinoma based on pathway and network-based analyses

BACKGROUND: Nasopharyngeal carcinoma (NPC) is a highly aggressive neoplasm mainly distributed in the eastern and southeastern parts of Asia. NPC has a poor prognosis among head and neck cancers, and molecular-targeted therapies showed limited clinical efficacy. METHODS: We reviewed publications in the PubMed database and extracted genes associated with NPC. The online tool WebGestalt was used to perform Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis for these genes. Next, the two parameters, Jaccard Coefficient (JC) and Overlap Coefficient (OC), were used to analyze the crosstalk of each pair of selected pathways. The new NPC-related genes were predicted by protein-protein interaction (PPI) network combined with hub genes extraction. Western blotting, qRT-PCR, and immunohistochemistry (IHC) were used to detect the expression of candidate genes in NPC cells and tissues, and cellular function assays were used to explore the effects of genes on NPC cells. RESULTS: A total of 552 genes were identified and used to build an NPC-related gene set (NPCgset). Pathways enriched in KEGG pathway analysis were further used for crosstalk analysis and were grouped into two modules: one was related to the carcinogenesis process, and the other was correlated with the immune response. Eight genes from the NPCgset were selected to build a PPI network, and two hub genes PIK3CA and AKT1 were chosen. Proteins interacting with PIK3CA were analyzed; among them, the expression of RRAS was down-regulated in NPC and associated with poor prognosis of NPC patients. Furthermore, RRAS suppressed proliferation, invasion and the epithelial-mesenchymal transformation (EMT) of the HK1 and 5-8F cell lines. CONCLUSIONS: Our study may help to explore the biological processes underlying NPCgset and suggests that RRAS may act as a tumor suppressor gene in NPC.