Enhancing effect of CpG on sensitivity of Lewis lung cancer to X-ray radiation in mice

Objective: To explore the role of cytosine-phosphate-guanine oligodeoxynucleotide(CpG ODN)in enhan- cing the radiosensitivity to X-ray in mouse with Lewis lung cancer.Methods: The tumor-bearing mouse model was in- duced by injevting Lewis lung cancer cells into the right infra-axillary dermis.Thirty-two C57BL/6J mice were evenly ran- domized into 4 groups.Group A: the control group;Group B: the X-Ray radiation group;Group C: the CpG group; Group D: the CpG plus X-Ray radiation group.Group B was treated with X-Ray radiation only(3 Gy/F,on day 1,3,5, 8,10,and 12;the total dose was 18 Gy);group C was administered with CpG ODN 0.05 mg on day 1,3,5,8,10, and 12;group D was administered with CpG ODN 6h before X-ray radiation.The tumor growth and tumor growth delay (TGD)were observed in all groups.Meanwhile,the pathological change of the tumor tissue was observed with H-E staining method and the apoptosis of tumor cells were examined with the method of TUNEL.Results: The Lewis hmg cancer-bearing model was successfolly established in mice.The tumor volumes of the treatment groups were smaller than that in lhe control group(P0.01),and the tumor volume of group D was the smallest.The tumor growth delays were 2.1 d in group B,2.3 d in group C,and 4.8 d in group D.The sensitization enhancement ratio of CpG ODN was 2.09. H-E staining showed that tumor necrosis in group B,C and D was more severe than that of control group,with the most se- vere one found in group D.TUNEL results revealed that the apoptosis rate were(2.75±0.89)% in group A,(4.87±1.13)% in group B,(7.63±1.41)% in group C,and(32.63±4.66)% in group D;the apnptosis rate of every therapy group was higher than that in the control group,and that of the group D significantly higher than those of group B and C(P0.01).Conclusion: CpG ODN can dramatically increase the radiosensitivity of tumor cells and promntetheir apoptosis.