Induction of telomerase activity and chromosome aberrations in human tumour cell lines following X-irradiation.

Telomerase, a ribonucleoprotein enzyme, has been detected in immortalised cells and in majority of human cancers. Numerical and structural chromosome aberrations are commonly observed in tumour cell lines. To study the expression of telomerase and its influence on the formation of chromosomal aberrations, human colon carcinoma cell line (SW480) and human nonpolyposis colorectal carcinoma (HNPCC) cell lines (NA50600, NA59 and NA61) were exposed to 2 or 4 Gy X-rays. Increased telomerase activity was observed in all these cell lines at 24 h postirradiation and a 3 to 7 fold increase was seen at 4 Gy dose as detected by Telomere Repeat Amplification Protocol. Chromosomal rearrangements (dicentrics, translocations and breaks/fragments) analysed by Giemsa staining and chromosome painting were increased significantly following X- Quantitative fluorescence in situ hybridisation using a peptide nucleic acid telomeric probe to measure telomere length at irradiation chromosomal level revealed that all cell lines have very short telomeres in the range of 0.29 to 2.1 kb. Following X-irradiation, an increase in the chromosome end-to-end (telomere) associations was observed. The present results demonstrate that presence or upregulation of telomerase activity did not prevent the formation of chromosome aberrations and/or telomere associations in tumour cell lines after X-irradiation.