CpG oligodeoxynucleotide 1826 enhances the Lewis lung cancer response to radiotherapy in murine tumor

CpG oligodeoxynucleotides (ODNs) are synthetic DNA sequences containing unmethylated cytosine-guanine motifs with potent immune modulatory effects. Via Toll-like Receptor 9 agonists of dendritic cells and B cells, CpG ODNs induce cytokines, activate natural killer cells, and elicit vigorous T-cell responses that lead to significant antitumor effects. On the basis of these properties of CpG ODNs, a previous study has tested that they could enhance tumor response to single-dose radiotherapy. The present study extended this finding to the fractionated radiotherapy of the Lewis lung Cancer and assessed the ability of CpG ODN 1826 to increase the immune function of mice and the effect of CpG ODN 1826 on the Apoptosis of Lewis lung Cancer. First, tumor growth delay was observed, and the enhancement ratio of CpG ODN 1826 was found to be 2.4; decreased tumor weight was found after combined treatments with CpG ODN 1826 and X-ray radiation compared with either treatment alone (P < 0.01). Second, enhanced cell apoptotic index was found after combined treatments with CpG ODN 1826 and X-ray radiation compared with either treatment alone (p < 0.01). Increased tumor necrosis factor-α and decreased interleukin-10 concentration in serum and enhanced spleen exponent were observed after combined treatments with CpG ODN 1826 and X-ray radiation compared with X-ray radiation treatment alone (p < 0.01). Results suggest that CpG-ODN1826 can increase the radiosensitivity of Lewis lung Cancer, which may be associated with stimulation of immune system and enhanced cell Apoptosis.