IDENTIFICATION OF CRYPTIC SITES OF DNA-SEQUENCE AMPLIFICATION IN HUMAN BREAST-CANCER BY CHROMOSOME MICRODISSECTION

We have performed microdissection of 16 putative homogeneously stainin g regions (hsrs) from nine different breast cancer cell lines in order to determine their chromosomal origin and composition. As expected, t he most commonly amplified chromosomal band-region was 17q12 (containi ng ERBB2). However, regions not containing known oncogenes were also i dentified, including 13q31 (5/9 cases) and 20q12-13.2 (4/9 cases). The chromosomal composition of the integrated amplified DNA within each h sr was determined and in 13/16 cases (81%), hsrs were shown to be comp osed of two or more chromosomal regions. These studies shed light on t he mechanism of formation of hsrs, and identify chromosomal regions li kely to harbour genes amplified in breast cancer.