The effect of different doses of bevacizumab and irinotecan on tumor growth of nude mice bearing human colon cancer DLD-1.

Abstract

518 Background: Anti-angiogenic therapy is an important therapeutic strategy in advanced colorectal cancer. However, the anti-angiogenic drug,such as bevacizumab(avastin) is expensive. So, clarifying whether different doses of avastin play the same effect in vivo is urgently needed. The aim of the study was to observe the different doses of avastin in combination with irinotecan in human colon tumor growth in nude mice and tumor angiogenesis. Methods: 21 nude mice inoculated with DLD-1 human colon cancer cells were randomly divided into four groups: sterile saline control (group A), 5mg/kg avastin plus irinotecan chemotherapy group (group B), 10mg/kg avastin plus irinotecan group (group C), and irinotecan chemotherapy group (group D). Drugs were administered in the first 1,5,9 days, mice were sacrificed in the 10th day after treatment, the tumor growth inhibitory rate was calculated and the tumor microvessel density (MVD) were detected by immunohistochemistry. Results: The tumor inhibition rate in groups B, C, and D were 62.85%, 47.91%, 39.59% respectively. A, B, C, and D groups’ MVD were 7.000 ± 0.71, 4.940 ± 0.58, 5.080 ± 1.25, 5.557 ± 2.04, The MVD in group B and C were significant different compared with group A by Dunnett's test, and the MVD expression difference between D, A groups and B, C groups did not reach statistical significance (P values were 0.086,0.083). Tissue necrosis was found in each group after HE staining of tumor tissue. Among them, the control group, mostly mild to moderate necrosis, and the necrosis area were increased after drug treatment. But there were no statistical differences of the necrotic area in drug treated groups graded by rank sum test (χ2 = 4.73, P = 0.193). And cell apoptosis was obviously seen in treated groups. Conclusions: Different doses of avastin with irinotecan inhibited the tumor growth on DLD-1 xenografted nude mice, Synergistic effects were observed in combination therapy, From cell morphology changes after staining with HE, we speculated that the mechanism may be related to the inhibition of tumor angiogenesis, and cell apoptosis increasing. The effect of 5mg/kg and 10mg/kg bevacizumab on tumor volume and MVD had no significant differences.