MOLECULAR CYTOGENETIC ANALYSIS OF A NONTUMORIGENIC HUMAN BREAST EPITHELIAL-CELL LINE THAT EVENTUALLY TURNS TUMORIGENIC - VALIDATION OF AN ANALYTICAL APPROACH COMBINING KARYOTYPING, COMPARATIVE GENOMIC HYBRIDIZATION, CHROMOSOME PAINTING, AND SINGLE-LOCUS FLUORESCENCE IN-SITU HYBRIDIZATION

The immortalized, nontumorigenic human breast epithelial cell line HMT -3522 has been used as a model for premalignant and, eventually, malig nant development. During cultivation, the karyotype evolution was foll owed. At an early stage, a very long constant phase showed a near-dipl oid karyotype, with only five marker chromosomes. DNA from this phase was used for comparative genomic hybridization (CGH) analysis, confirm ing a previously known MYC amplification, and the integration sites we re subsequently determined by single-locus fluorescence in situ hybrid ization (FISH). Furthermore, gains of 5q22-qter and 20q11-qter and del etion of most of chromosome 6 (6p23-qter) were detected by CGH. Becaus e of uncertainty about some of the indicated changes, including a dele tion of 1p35-pter, the CGH findings were investigated more closely by chromosome painting, leading to a revision of the karyotype: 1)(p35),- 6,dup(8)(pter-->qter::qter-->q24),der(12) t(6;12)(p23; ter::8q24-->8qt er::8q23-->8q24.1::20q11-->20qter). Some karyotypic changes were confi rmed by CGH; others had to be revised; and, in the 1p35 region, classi cal cytogenetics seems superior to CGH. However, CGH revealed a karyot ypically unsuspected dup(20q) that might be of special relevance to br east tumor initiation or progression. Our study confirms that CGH is s upplementary to current technologies, e.g., karyotyping and Southern a nalysis, but cannot replace them. In addition, our cell line turned ou t to be an excellent model for comparison among the different methods. The results imply that future cytogenetic analyses of complex karyoty pes should be based on a combination of karyotyping, CGH, and FISH. (C ) 1997 Wiley-Liss, Inc.