Fundamental Research of the Function of Angiogenesis Inhibitors to Colon Cancer Stem Cells in Mice and Analysis of Related Mechanism
|School||Dalian Medical University|
|Keywords||Cancer stem cells Colorectal cancer Wnt signal path way Angiogenesis inhibitor|
Colorectal cancer, including colon cancer and rectal cancer, is one of the most common malignant tumors. Its incidence and mortality in china increased significantly in the past 30 years. Efficiency of traditional chemotherapy for advanced colorectal cancer was poor. With the development of new drugs such as oxaliplatin and irinotecan, the response rate and survival of advanced colorectal cancer were increased greatly. The emergence of target medicine improved the treatment of advanced colorectal cancer to a new level. However tumor recurrence and metastasis is still the main reason for treatment failure. Studies suggest that there is a small group of cells in tumors with self-renewal and differentiation potential called cancer stem cells, which may be the source of tumor metastasis and recurrence. In cancer stem cells, some signal transduction pathway are abnormally activated, which regulates transcription of downstream target gene resulting in self-renewal of cancer stem cell ,enhanced invasion, tumor recurrence and metastasis.Bevacizumab is one of the target drugs for advanced colorectal cancer, It’s a human monoclonal antibody, blocking the vascular endothelial growth factor and inhibiting tumor angiogenesis and tumor growth. Currently Endostar is used for target treatment of non-small cell lung cancer by inhibiting the migration of endothelial cells, further inhibiting tumor angiogenesis, thus choking off the supply of nutrients to inhibit tumor proliferation or migration. Because they have the similar mechanism, in this study, we compare the inhibitory effect of the two drugs on colorectal cancer and preliminarily discuss the function of drugs to colorectal cancer stem cells and the related mechanism. Objective: To compare inhibitory effect of endostar and bevacizumab in mice implanted colon cancer and to discuss the feasibility of endostar in the treatment of colorectal cancer. To discuss inhibitory effect of drugs on colon cancer stem cells marked by CD44 and to investigate whether the mechanism is related to Wnt signaling path way, which is involved in the maintenance of cancer stem cell by detecting expression of CD44,β-catenin and VEGF.Methods: CT26.wt colon cancer cell were cultured in logarithmic growth phase, then the cell concentration was adjusted to 6×10~6/mL, and 0.2ml cell suspension was injected subcutaneously in the right lower limb per mice, when the tumor volume reached 200mm3, we began drug intervention. The mice were randomly divided into 3 groups, (n = 8). The control group: NS 0.2ml d1-14 intraperitoneal injection. Bevacizumab group: 5mg/kg d1,8 intraperitoneal injection. Endostar group: 3mg/kg d1-14 intraperitoneal injection. During treatment, implanted tumor volume, body weight, food intake, mental status of mice was observed and recorded. The mice were sacrificed within 24 hours after final medication, the tumor growth curve and tumor weight inhibitory rate were described. Finally, CD44,β-catenin and VEGF protein expression were detected by immunohistochemistry.Results: The general status of mice: The control group on day 7 of the administration appeared apathetic, and water consumption was reduced.Two experimental groups also had the similar symptoms, but to a less extent; Changes in tumor volume: On day 6 of drug intervention, tumor volume in three groups was similar. On day 9, the difference in tumor size appeared between the drug groups and the control group, but the difference was not seen in two drug groups. On day 12 significant differences appeared among the three groups. Bevacizumab group<Endostar group<control group. Tumor inhibition rate in bevacizumab group was 47.22%. Tumor inhibition rate in endostar group was 22.22%; Immunohistochemical results: We detected expression of VEGF, CD44 and B-catenin. Compared with the control group, the expression of the three indicators were reduced in endostar and bevacizumab group, expression decreased obviously in bevacizumab group (P<0.05). Application spearman rank correlation analysis showed a positive correlation between CD44 andβ-catenin (P<0.05). a positive correlation between VEGF andβ-catenin(P<0.05).Conclusions: Endostar and bevacizumab can inhibit growth of CT26.wt colon cancer implanted tumor in mice, and bevacizumab has a stronger effect; Endostar and bevacizumab can inhibit tumor angiogenesis, and bevacizumab has a stronger effect; Endostar and bevacizumab can inhibit CD44~+ colon cancer cell and the abnormal activated Wnt pathway which is involved in the maintenance of cancer stem cells , and bevacizumab also showed a stronger effect.