Abstract
The detection of microsatellite instability (MSI) is a standard part of mutational analysis in hereditary nonpolyposis colorectal cancers (HNPCC). A characteristic phenotypic feature of MSI indicates loss of mismatch repair (MMR) in tumour cells.
We studied MSI in 205 tumours from 152 patients with HNPCC. Of these, 37 patients fulfilled the Amsterdam criteria, 72 patients were familial and 43 were sporadic cases.
We used the method of fragmentation analysis (ABI Prism 310 Genetic Analyzer) with fluorescent labelled primers; three mononucleotide (BAT-RII, BAT-25, BAT-26) and five dinucleotide (D2S123, D3S1029, D5S346, D17S250, D18S58) repeat loci were analysed. We detected 75 tumours with a high degree of MSI (MSI-H), 12 tumours with a low degree of MSI (MSI-L) and 118 tumours with stable microsatellites (MSS).
We found a loss of heterozygozity (LOH) in 44 MSS tumours. In 30 patients with MSI-H tumours mutation in one of mismatch repair genes was detected.