Microsatellite instabilities at five chromosomes in primary breast tumors.

The microsatellite instabilities at nine loci of chromosomes 2p, 8p, 10p and 11p and the nm23-H1 locus on 17q21.3 were studied in primary breast tumors. Alterations in the short interspersed tandem repeats in tumor DNA in the form of either larger allele, smaller allele or LOH were observed. Significantly, a high occurrence of alterations in microsatellite polymorphisms at the ANK1, D8S135 and LPL loci of chromosome 8p (46-54%), the D2S119 locus of chromosome 2p (56%), the D10S197 locus at chromosome 10p (88%), and the nm23-H1 locus of chromosome 17q21.3 (46%) were observed in breast tumors. These results provide the first evidence for genomic instabilities at 2p, 8p and 10p in primary ductal and lobular breast carcinomas. No correlation has been found between the stage of the tumor and microsatellite instability, suggesting that microsatellite instability is an early genetic event in breast carcinogenesis.