## Abstract Loss of DNA mismatch repair (MMR) occurs in 10–15% of sporadic colorectal cancer, is usually caused by hMLH1 hypermethylation, and has been shown to confer resistance to various chemotherapeutic reagents, including 5‐fluorouracil (5‐FU). We tested the hypothesis that demethylation of th
Role of ERCC1 promoter hypermethylation in drug resistance to cisplatin in human gliomas
✍ Scribed by Hua-Yun Chen; Cui-Jie Shao; Fu-Rong Chen; Aij-Lie Kwan; Zhong-Ping Chen
- Book ID
- 102862921
- Publisher
- John Wiley and Sons
- Year
- 2009
- Tongue
- French
- Weight
- 523 KB
- Volume
- 126
- Category
- Article
- ISSN
- 0020-7136
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✦ Synopsis
Abstract
Overexpression of ERCC1 mRNA is associated with drug resistance to cisplatin in human gliomas, but the role of the ERCC1 promoter in drug resistance has not been demonstrated. We have used sodium bisulfite sequencing to compare ERCC1 promoter methylation patterns in cisplatin‐sensitive and cisplatin‐resistant glioma cells. The levels of ERCC1 DNA methylation, mRNA and protein in 32 human glioma samples were examined by methylation specific PCR, real‐time RT‐PCR and immunohistochemistry, respectively. Meanwhile, cisplatin sensitivities to these human glioma samples were tested by histoculture drug response assay. Hypermethylation was observed in the upstream 5Kb region of the ERCC1 promoter of cisplatin‐sensitive glioma cell lines. ERCC1 DNA methylation levels were highly variable in 32 human glioma samples ranging from 0.1 to 0.87, which have shown significant difference between cisplatin‐sensitive samples and cisplatin‐resistant samples (p < 0.05). The relative expression levels of ERCC1 mRNA in 32 glioma samples were also variable from 0.01 to 5.71. No detectable or low expression of ERCC1 protein was shown in 7 glioma samples. ERCC1 promoter methylation was inversely correlated to mRNA expression (r = −0.903 p = 0.001) as well as protein expression (r = −0.884 p = 0.001). Moreover, ERCC1 mRNA expression was significantly associated with protein levels (r = 0.840 p = 0.001). In summary, the aberrant CpG island methylation in ERCC1 promoter region exists in human glioma cell lines as well as clinical glioma samples. ERCC1 DNA methylation could regulate the expression of downstream mRNA and protein, and was associated with cisplatin chemosensitivity.
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Human glioma cells were exposed to stepwise increasing concentrations of cisplatin and given a final, acute, high concentration treatment of cisplatin. From the surviving cells, eight cisplatin resistant clones were selected. These clones demonstrated a range of cisplatin sensitivities that were ret