Analysis of telomeric repeats and telomerase activity in human colon carcinoma cells with gene amplification

COLO320DM and COLO320HSR are cell lines derived from a human malignant neur oendocrine colon carcinoma. Both lines have a 30-40-fold amplification of a large DNA domain containing the MYC oncogene. By using fluorescence in sit u hybridization techniques with a A MYC probe, we could demonstrate that MY C amplicons are contained in a large marker chromosome in COLO320HSR cells, in double minutes (dmin) of COLO320DM cells, and in the interstitial regio ns of 3-4 additional chromosomes in both cell lines. Amplicons in homogeneo us staining regions (HSRs) comprise normal MYC genes, while dmin chromosome s contain PVT/MYC chimeras. Although both cell lines showed similar levels of telomerase activity, the telomere length and telomere distribution in ch romosomal termini were considerably lower in COLO320DM than in COLO320HSR c ells. This indicates that the average telomere length in cancer cells is re gulated no only by the rates of telomerase activity but also by some other non-enzymatic mechanisms. (C) 2000 Elsevier Science Inc. All rights reserve d.