BAT-26 and BAT-40 instability in colorectal adenomas and carcinomas and germline polymorphisms

Analysis of the mononucleotide repeats BAT-26 and BAT-40 has reportedly rev ealed significant microsatellite instability in sporadic colorectal adenoma s, whereas studies with dinucleotide and tetranucleotide repeats have not. In addition, BAT-26 has been reported to be "quasimonomorphic" in the germl ine. We evaluated BAT-26 and BAT-40 in a series of colorectal tumors previo usly analyzed with a panel of tetranucleotide repeats. Instability in BAT-2 6 or BAT-40 was significantly associated with tetranucleotide repeat instab ility in sporadic adenomas and carcinomas (P < 0.0001) and was similarly mu ch less common in adenomas than in carcinomas. Germline polymorphisms in bo th BAT-40 and BAT-26 were Identified, and the frequency of BAT-26 polymorph isms was significantly higher in African Americans than in Caucasians (7.7% versus 0.08%, P < 0.001), BAT-26 and BAT-40 may be very useful in evaluati ng instability in small tumors, as sufficient DNA to be amplified by large panels of microsatellites is not always available from such lesions. Polymo rphisms in these microsatellites, however, limit their utility in determina tions of microsatellite instability without corresponding normal DNA.