Enhancing effect of CpG ODN on sensitivity of Lewis lung cancer to carboplatin in mice

OBJECTIVE:To explore the role of cytosine-phosphate oligodeoxynucleotides (CpG ODN) in enhancing the sensitivity to carboplatin in mouse with Lewis lung cancer. METHODS: The tumor-bearing mouse model was induced by injecting Lewis lung cancer cells into the right infra-axillary dermis. 32 C57BL mice were evenly randomized into 4 groups. Group A: control group; Group B: carboplatin group; Group C: CpG group; Group D: CpG plus carboplatin group. Group B was treated with carboplatin only(0.32mg/d, on day1,2,3,4,5). Group C received CpG ODN 0.05 mg on day 1,2,3,4,5. Group D was treated with CpG ODN 6 h before carboplatin. Tumor growth and tumor weight were observed in all groups. The pathological change of the tumor was evaluated with HE staining and apoptosis of tumor cells were examined with TUNEL method. RESULTS: The Lewis lung cancer-bearing model was successfully established in mice. The tumor volumes of treatment groups were smaller than that in control group (P0.01),and the tumor volumes of group D was the smallest. The rates of tumor were 23.35% in group B, 21.47% in group C, and 48.43% in group D. HE staining showed that tumor necrosis in group B, C, and D was more severe than that of control group, with the most severe one in group D. The apoptosis rates were (2.75±0.89)% in group A,(8.88±1.13)% in group B, (7.63±1.41)% in group C, and (31.13±4.67)% in group D. The apoptosis rate of every treated group was higher than that in the control group, with group D significantly higher than those of group B and C(P0.01). CONCLUSION: CpG ODN could dramatically increase the chemo-sensitivity of tumor cells and promote their apoptosis.