CHROMOSOME PAINTING AND QUANTITATIVE KARYOTYPING OF COLON ADENOCARCINOMA CELL-LINES, DLD-1 AND HCT-15

Chromosome painting by fluorescence in situ hybridization (FISH) was u sed to examine abnormalities identified by G-banding in colon cancer l ines, DLD-1 (ATCC CCL 221) and HCT-15 (CCL 225). DNA libraries from ch romosomes comprising these abnormalities (i.e., N2, N8, N11, N16, N17 and N20) were used to prepare paint probes by PCR amplification. Of th ese paint probes, N2 and N8 exhibited additional chromosome-specific h ybridization signals on centromeres there were also useful as a marker for chromosome identification. Results from FISH-painting and G-band analysis were consistent and permitted our quantitative analysis on ka ryotype evolution in vitro. In DLD-1, predominant cells having trisomi c N20 in early passages were replaced by others with disomic N20 in la te passages resulting in the trisomic 2p13-23 segment as the only devi ation from the diploid content. In HCT-15, predominant cells having t( 16;16) and double Y chromosome copies in early passages were replaced by those bearing the paired N16 and single Y chromosome in later passa ges. Thus cultures changed from the predominant hyperdiploidy to the s ole pseudodiploidy with increased number of normal chromosomes.