Absence of microsatellite instability in breast carcinomas with both p53 and c-erbB-2 alterations

Based on a previous finding that amplification of the c-erbB-2 oncogene and alteration of p53 are strongly associated in most aggressive breast tumour s, the present study investigated whether microsatellite instability (MI) m ight also be associated with this tumour phenotype, Nine polymorphic micros atellite markers, including six dinucleotide, one trinucleotide. and two te tranucleotide repeats, were amplified from paired normal and tumour DNA sam ples of 15 breast tumours that overexpressed both c-erbB-2 and p53 and of 1 5 control breast tumours that overexpressed neither protein, All 30 breast tumours analysed exhibited a replication error-negative phenotype, with onl y one sample showing MI in one of the nine loci. This suggests that the gen etic events underlying MI, which are critical in colorectal and gastric tum ours, are not involved in the pathogenesis of c-erbB-2/p53 double-altered b reast tumours and do not play a central role in breast tumour formation. Co pyright (C) 1999 John Wiley & Sans, Ltd.