IMPORTANT MICROSATELLITE MARKERS IN THE INVESTIGATION OF REPLICATION ERRORS (RER) IN COLORECTAL CARCINOMAS

Background: DNA replication errors (RER) have been found in hereditary nonpolyposis colorectal carcinomas and in sporadic colorectal carcino mas. The incidence of RER depends on which and how many markers are ex amined. The main purpose of the present study was to determine the key markers for detecting RER most efficiently. Methods: The RER status o f 76 sporadic advanced colorectal carcinomas in the proximal colon wer e investigated. Seven microsatellite markers (D2S123, D3S1029, D3S1611 , D2S72, TP53, Mfd26 and BAT26) were chosen to determine the RER statu s by PCR using the non-RI method, because these seven markers have fre quently been used in other studies and also detect RER. Results: It wa s found that 44.7% of sporadic colorectal advanced carcinomas in the p roximal colon (34 of 76) showed RER at one or more loci. Among these 3 4 cases, RER was present at three or more markers (severe RER) in 22. All 22 of these cases showed RER at BAT26 and TP53. The other 12 cases with RER showed RER at one or two markers (mild RER). Eleven of these 12 cases (91%) showed RER at Mfd26 and there were one or two cases wi th mild RER at each of the other loci. Conclusions: When one intends t o analyze routinely a large number of cases, an analysis of two or thr ee markers (Mfd26 and BAT26 or TP53) is considered to be sufficient fo r detecting mild and severe RER.