Biological characteristics of a
tumor are primarily affected by its genomic alterations. It is thus important to ascertain whether there are genomic changes linked with
DNA ploidy and/or
chromosomal instability (CIN). In the present study, using fresh-frozen samples of 46 invasive breast
cancers,
laser scanning cytometry, array-based comparative genomic hybridization, and chromosome fluorescence in situ hybridization were performed to assess
DNA ploidy,
DNA copy number aberrations (DCNAs), and CIN status. Both ploidy and CIN status were examined in 36
tumors, resulting in 23
aneuploid/CIN+
tumors, 1
aneuploid/CIN-, 2 diploid/CIN+, and 10 diploid/CIN-
tumors. Comparison of the aCGH data with the
DNA ploidy and CIN status identified cytogenetically 11 characteristic breast
cancers with distinctive DCNAs. The 11
tumors were classified into two types; one type is diploid/CIN- phenotype containing 4 DCNAs, and the other
aneuploid/CIN+ phenotype containing 7 DCNAs. In 30 (65.2%) of the 36 breast
cancers, the status of
DNA ploidy and CIN depended on the type of DCNAs. Furthermore, the
DNA ploidy phenotype depended on the dominant type of DCNAs even in
tumors with a mixture of multiple DCNAs of one type and a single
DCNA of the other type.
Tumors with multiple DCNAs of both types represented
aneuploidy and over three quarters of breast
cancers carry at least one type of the DCNAs. These results suggested that, in breast
cancers, the status of
DNA ploidy and CIN was likely to determine at the beginning of
carcinogenesis.