Microsatellite instability markers in breast cancer: A review and study showing MSI was not detected at 'BAT 25' and 'BAT 26' microsatellite markers in early-onset breast cancer

Microsatellite markers may provide evidence of faulty DNA mismatch repair ( MMR) via the detection of microsatellite instability (MSI). The choice of m icrosatellite markers may impact on the MSI detection rate. In hereditary n on-polyposis colon cancer (HNPCC), several informative microsatellite marke rs have been recommended. Two of these, BAT 25 and BAT 26, are quasi-homozy gous, enabling analysis of tumour DNA in the absence of paired normal DNA. Sixty-six breast cancer patients under 45 years of age at diagnosis were ex amined for MSI at BAT 25 and BAT 26. Tumour DNA was extracted from paraffin -embedded tissue. No MSI was detected at the BAT 25 or BAT 26 loci. An addi tional five microsatellite markers, known to be informative for HNPCC, were examined for MSI in these patients. Apparently-normal profiles were achiev ed. A tabulated survey of 306 microsatellite markers used to detect MSI in breast cancer revealed that only 35.5% of markers detected MSI at an averag e rate of 2.9%. The MSI detection rate at the specific HNPCC markers varied from 0% to 10% in breast cancer, with D175250 and TP53 being the HNPCC mar kers most suitable for analysis of breast cancer. The size of the microsate llite marker's repeat unit did not impact on MSI detection rates. Compiled data from large studies (n > 100) revealed D115988 as the marker with the h ighest MSI detection rate. Genomic instability pathways of carcinogenesis, characterised by MMR defects and MSI, appear to play a role in the genesis of some breast cancer types.