Gene expression profiles and protein-protein interaction networks during tongue carcinogenesis in the tumor microenvironment

Oral tongue squamous cell carcinoma (OTSCC) has a high incidence and is associated with a high mortality rate. Studies regarding the potential molecular mechanism of OTSCC in the tumor microenvironment (TME) are required. The present study aimed to perform bioinformatic analysis to identify important nodes, clusters and functional pathways during tongue carcinogenesis in the TME. After downloading the gene expression data of GSE42780, differentially expressed genes (DEGs) among carcinoma, dysplastic and normal samples in epithelia and fibroblasts were identified using the affy and limma packages with R version 3.3. Subsequently, the Database for Annotation, Visualization and Integrated Discovery was employed to perform Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Furthermore, a protein-protein interaction (PPI) network was constructed by using the Search Tool for the Retrieval of Interacting Genes/Proteins and analyzed by Cytoscape software. In total, 85 DEGs were identified for tongue epithelia and 46 DEGs were identified for fibroblasts. Neutrophil chemotaxis and inflammatory response from GO, and cytokine-cytokine receptor interaction from KEGG were enriched for epithelia and fibroblasts. The PPI network revealed that C-X-C motif chemokine ligand (Cxcl)1, Cxcl10, Cxcl13, Cxcl2 and pro-platelet basic protein were a key cluster for epithelia, and interleukin (Il)1, Il1 receptor 2, Il1a and Il1 receptor antagonist were a key cluster for fibroblasts. Therefore, the results indicate that fibroblasts and cytokines associated with an inflammatory immune response contributed substantially to tongue carcinogenesis in the TME, which is useful for the development of OTSCC targeted therapy. However, further investigation is required to elucidate the molecular and cellular mechanisms underlying the inflammatory immune network in the TME.