Radiosensitization by CpG ODN7909 in an epidermoid laryngeal carcinoma Hep-2 cell line

OBJECTIVE: To evaluate the radiosensitivity effect of CpG oligodeoxyribonucleotide (ODN) 7909 on human epidermoid cancer strain-2 (Hep-2) cells in vitro and discuss the potential for improved radiotherapy treatment in patients with laryngeal squamous cell carcinoma. METHODS: Toll-like receptor (TLR) 9 expression was assessed in Hep-2 cells using Western blots and reverse transcription polymerase chain reaction. Cell Counting Kit-8 was used to detect Hep-2 cell viability at 24 and 48 h following treatment with different CpG ODN7909 concentrations. Cellular colonization was evaluated using microscopy. Cell cycle distribution and apoptosis rate was determined with flow cytometry. Interleukin (IL)-12 and tumour necrosis factor (TNF)-α concentrations were detected by enzyme-linked immunosorbent assay. RESULTS: Hep-2 cells were found to express TLR9, and CpG ODN7909 treatment suppressed Hep-2 cell viability in a dose- and time-dependent manner. Cell survival curve analyses revealed a sensitivity enhancement ratio of the mean death dose of 1.225 for CpG ODN7909 plus irradiation versus irradiation alone. Furthermore, the population of Gap 2/mitotic-phase cells, apoptosis rate and secreted IL-12 and TNF-α levels were significantly increased in Hep-2 cells treated with CpG ODN7909 plus irradiation versus IR alone. CONCLUSION: CpG ODN7909 enhanced the radiosensitivity of Hep-2 cells in vitro.