| Popis: |
Microsatellite instability (MS1) is found in 15% of all human colorectal cancers and is due to mismatch repair (MMR) protein inactivation, most commonly MSH2 and MLH1. We used microRNA to generate three stable MMR protein knockdown cell lines with reduced MSH2, MLH1 and both MSH2 and MLH1. Despite protein reductions of up to about 90%, we found no increase in mutation in certain repetitive regions or within important oncogenes. A 15-fold increase in mutation frequency within a gene involved in purine metabolism was seen in MSH2 knockdown cells but no difference in sensitivity to 6-thioguanine was detected. MSH2 knockdown and control cells were exposed to ischemic conditions which caused down-regulation of all MMR proteins evaluated, but no mutations were found within certain repetitive regions or within important oncogenes. This study indicates that MMR proteins seem to be highly efficient at correcting DNA insertions, deletions and mismatches even under adverse conditions. |
