Tumor necrosis factor α promotes HEp-2 cell proliferation via toll-like receptor 4 and NF-κB signaling pathways

Laryngeal carcinoma is a serious, life-threatening disease. Tumor necrosis factor α (TNF-α), a proinflammatory cytokine, has complex effects on the proliferation and growth of cancer cells. Previously, we treated a laryngeal cancer cell line (HEp-2) with TNF-α and demonstrated that this treatment suppressed polycystin-2, a transient receptor potential cation channel expression and ATP-induced Ca²⁺ release but increased HEp-2 cell proliferation and growth. However, the mechanisms and signaling pathways underlying the TNF-α effects on the HEp-2 cells were unclear. Therefore, we here used RNA-seq techniques to examine the effect of TNF-α on the gene transcript expression profile in these cells. We found that TNF-α treatment (100 ng/mL, 24 h) upregulated 2,811 genes and downregulated 1,128 genes. The IRAK1 gene encoding an effector protein downstream of toll-like receptor 4 (TLR4) was ranked 19th in the upregulated differentially expressed genes. In a gene ontology (GO) analysis, 168 GO terms were identified in the biological process domain for the upregulated differentially expressed genes, and cell cycle and DNA replication functions were enriched. In a Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, TNF-α treatment enhanced the NF-κB pathway in HEp-2 cells. Moreover, both the transcript and protein expression levels of TLR4 as well as the expression of genes encoding downstream TLR4 effectors were significantly increased in TNF-α-treated HEp-2 cells. We concluded that TNF-α increased HEp-2 cell proliferation and growth likely via enhancing TLR4- and NF-κB-associated signaling pathways and that TNF-α may play an important role in the development of laryngeal cancer.