6th ESACP Congress, Heidelberg, April 7-11, 1999

A025
ACCUMULATION OF CHROMOSOMAL IMBALANCES BY CGH DURING DEVELOPMENT AND PROGRESSION OF BREAST CANCER
Aubele M 1, Walch A 1, Mattis A 2, Zitzelsberger H 3,4, Kremer M 2, Höfler H 1,2, Werner M 2

1 GSF-Institute of Pathology, 2 TU München, Institute of Pathology, 3 GSF-Institute of Radiobiology, 4 LMU München, Institute of Radiobiology, München, Germany

One model of breast tumorigenesis postulates a sequential evolution from normal to proliferative epithelium (hyperplasia without and with atypia) and occasionally to neoplasia, but genetic data to support this progression are limited. To characterize the sequence of early chromosomal alterations and their accumulation during further progression we have carried out comparative genomic hybridization (CGH) on different stages of breast cancer development in the same patients. Formalin fixed, paraffin-embedded tissue sections from 5 patients were investigated. Lesions consisted of normal ducts as control (n=5), ductal hyperplasias (DH, n=5), atypical ductal hyperplasias (ADH, n=3), intraductal carcinomas (dCIS, n=5), and invasive ductal carcinomas (IDC, n=5). For CGH, cell groups consisting of 300 to 500 cells of a defined histopathological entity were laser-microdissected, the DNA was amplified using DOP-PCR, and used for CGH analyses. Separate analysis of DH and/or ADH, dCIS, and IDC components in the same patients revealed an increasing number of alterations with increasing malignancy. A mean of 7.0 (±4.0) chromosomal changes was identified in DH, 9.3 (±4.9) in ADH, 11.4 (±1.8) in dCIS, and 16.6 (±2.9) in IDC. Several consistent chromosomal changes were identified at all histopathological entities: gains on 8q, 10q,16p,19q,20q,22q, and loss on 13q. In DH we already identified with high frequency (4/5 samples) gains on 19q,20q, and loss on 13q. Alterations additionally occuring in ADH were gains on 1q,6p,7q,11q13,14q,15q,16q,17, and loss on 16q. The transition to dCIS was characterized by DNA gain on 10p and losses on 5q and 9p, in IDC gain on 21q as well as loss on 6q were additionally identified. In conclusion, several chromosomal imbalances were identified already in DH and, therefore, can be considered as early events in development of breast cancer. Particularly DNA gain on 20q13, already present in DH, indicates an early involvement of onco-genes (e.g. AIB amplification score). Most of the alterations identified in DH persist during further malignancy development suggesting clonal origin. The alterations additonally identified, may possibly play an important role in transition to the more malignant stage.