Study on aldo-keto reductases as potential targets of antitumor agents : its involvement in the drug resistance of cancer cells

点击翻译按钮获取中文摘要

An aldo-keto reductase, AKR1B10 has been shown to be induced in the human non-small cell lung carcinoma. In this study, we studied the regulatory mechanisms of gene expression of AKR1B10 for the purpose of developing the drug metabolizing enzyme-targeting antitumor agents. First, we examined the AKR1B10 expression in human non-small cell lung carcinoma cell lines, A549 and H23 with RT-PCR technique. While significant AKR1B10 expression was observed in A549 cells, very little expression was detected in H23 cells, showing that these two cell lines can be useful research tools to study the gene regulation of AKR1B10 because of the remarkable contrast in the AKR1B10 expression. In order to identify the regulatory region upon AKR1B10 gene, the 5'-flanking region was isolated from A549 cells and analyzed. There is a microsatellite raging from -720 to -588 with CCTT repeats between the two alleles. However, this microsatellite was shown not to be involved in the regulation of basal AKR expres … More sion in luciferase reporter assay. There are several potential regulatory consensus sequences within the 5'-flanking region. Among them, there is a consensus sequence of antioxidant response element (ARE), which is related to the redox regulation of gene expression. Then, ethoxyquin, a reagent that enhances the ARE-mediated expression, was test for the AKR1B10 induction in H23 cells, and was shown to increase the AKR1B10 expression. Since transcription factor Nrf2 binds to ARE and enhances the gene expression, an Nrf2 expressing plasmid was co-introduced in the luciferase reporter assay. Co-expression of Nrf2 significantly increased the transcriptional activity of AKR1B10 gene, suggesting that ARE and Nrf2 can be involved in the AKR1B10 gene regulation. In addition, hydrogen peroxide, an active oxygen species, could induce the AKR1B10 expression in H23 cells with RT-PCR. These results suggest that AKR1B10 expression is regulated by oxidative stress that is tightly related to carcinogenesis. These findings are expected to be fundamental information to clarify the implication of aldo-keto reductases in the carcinogenesis and drug resistance of cancer cells, and to develop the aldo-keto reductase-targeting antitumor agents. Less