Upregulation of vascular endothelial growth factor by hydrogen peroxide in human colon cancer

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Abstract
AIM: To evaluate the effect of reactive oxygen species such as hydrogen peroxide on the progression of human colon cancer. METHODS: Human colon carcinoma cell lines, LS174T and HCT8, were treated respectively with 10-5, 10-7 or 10-9 mol·L-1 hydrogen peroxide for 24 h, and co-cultured with human endothelial cell line ECV-304. The migration of ECV-304 induced by cancer cells was calculated and the expression level of vascular endothelial growth factor in cancer cells was determined by RT-PCR analysis and ELISA. Dactinomycin of 1.5 mg·L-1 which could block transcription of cancer cells was applied to observing the effects of H2O2 on transcriptional activity and the relative half-life of VEGF mRNA. Finally, to evaluate the effect of H2O2 on NF-κB activity in colon cancer cells, NF-κB in cytoplasm and nucleus of the cells were detected with FITC-tagged antibody and its presence in the nucleus(Fn) vs cytoplasm(Fc) was monitored by measuring the green fluorescence integrated over the nucleus by laser scanning cytometry(LSC) RESULTS: Exogenouse hydrogen peroxide of low concentration increased the migration of endothelial cell induced by colon cancer cells. When cancer cells were treated with 10-5 mol·L-1 H2O2, the migration number of endothelial cells induced by LS174T cells was 203 ± 70, and the number induced by HCT8 cells was 145 ± 65. The two values were significantly higher than those treated with other concentrations of H2O2 (P < 0.01).The expression of vascular endothelial growth factor in cancer cells, which could be blocked by dactinomycin, were increased to a certain degree, while the relative half-life of VEGF mRNA was not prolonged after treatment with hydrogen peroxide. The activity of NF-κB in colon cells rose after the cells were exposed to hydrogen peroxide for 24 h.The Fn values in HCT8 cells were 91 ± 13 (0 mol·L-1 H2O2) and 149 ± 40 (10-5 mol·L-1 H2O2) (P < 0.05),in LS174T cells were 127 ± 35 (0 mol·L-1 H2O2) and 192 ± 11 (10-5 mol·L-1 H2O2) (P < 0.05). It is similar to the case of VEGF expression in cancer cells. CONCLUSION: Hydrogen peroxide increases vascular endothelial growth factor expression in colon cancer cells, and it is likely that reactive oxygen species such as hydrogen peroxide facilitates the development of colon cancer.