SHORT REPORT Chromosomal 20q gain in the DNA diploid component of aneuploid colorectal carcinomas

The order of appearance of different genetic aberrations duringthe shift from diploidy/near-diploidy to aneuploidy in colorectalcancers is not yet clear. We studied genetic alterations in flowcytometrically-sorted DNA diploid and corresponding aneuploidepithelial cell populations from each of 20 colorectal tumors usingcomparative genomic hybridization, FISH, and PCR. Analysis ofthe 19 cases in which aberrations were found in the flow-sorteddiploid population indicated that large-scale aneuploidization incolorectal cancer was preceded by amplification of oncogene(s)localized to chromosome 20q13.2 and by KRAS mutations, but notby TP53 deletions or losses of large chromosomal regions such as4q, 8p and 18q.