The telomere length dynamic and methods of its assessment

Abstract

Human telomeres are composed of long repeating sequences of TTAGGG, associated with a variety of telomere‐binding proteins. Its function as an end‐protector of chromosomes prevents the chromosome from end‐to‐end fusion, recombination and degradation. Telomerase acts as reverse transcriptase in the elongation of telomeres, which prevent the loss of telomeres due to the end replication problems. However, telomerase activity is detected at low level in somatic cells and high level in embryonic stem cells and tumor cells. It confers immortality to embryonic stem cells and tumor cells. In most tumor cells, telomeres are extremely short and stable. Telomere length is an important indicator of the telomerase activity in tumor cells and it may be used in the prognosis of malignancy. Thus, the assessment of telomeres length is of great experimental and clinical significance. This review describes the role of telomere and telomerase in cancer pathogenesis and the dynamics of the telomeres length in different cell types. The various methods of measurement of telomeres length, i.e. southern blot, hybridization protection assay, fluorescence in situ hybridization, primed in situ, quantitative PCR and single telomere length analysis are discussed. The principle and comparative evaluation of these methods are reviewed. The detection of G‐strand overhang by telomeric‐oligonucleotide ligation assay, primer extension/nick translation assay and electron microscopy are briefly discussed.

Telomeres: Prognostic markers for solid tumors

“…Hybridization with a telomere-specific probe (e.g., radioactively labeled) is performed and telomere length is usually assessed by densitometric analysis of the highest peak TRF signal after exposure of the blot to light-sensitive film or to a phosphorimager. 39,40 However, this well-established methodology harbors several inherent disadvantages. For example, Southern blots require relatively large amounts (i.e.…”

“…Several methods have been developed to measure telomere length, or its proxies, and have been recently reviewed by Lin and Yan 39 and by Baird. 40 These include the well-established Southern blot method, the telomere DNA content (TC) titration assay 41,42 and telomere fluorescence in situ hybridization (FISH).…”

“…In addition, Southern blot radiographs often display multiple peaks, leading to a high variability in interpretation. 39,40 A method for assessing the total content of telomere DNA sequences (TC), a surrogate for telomere length, in genomic DNA was recently reported. 41,42 Briefly, genomic DNA is immobilized on membranes in a slot blot format and titrated by hybridization with a telomere-specific probe, either normalized to centromeric DNA 41 or to total genomic DNA in the same sample.…”

Correlation of telomere length shortening with promoter methylation profile of p16/Rb and p53/p21 pathways in breast cancer

“…23,24 In this study, we explored the feasibility of using paraffin-embedded tissues for the quantitative assessment of telomere length together with highthroughput methylation quantification on MALDI-TOF silico-chips. 20,21 Before carrying out telomere length analysis, yield of extracted DNA from formalin-fixed paraffin-embedded tissues was quantified using NanoDrop ND-1000 spectrophotometer (Biolab, Mulgrave, Vic, Australia).…”

The role of telomere biology in bone marrow failure and other disorders

“…Numerous methods are available to determine telomere length in blood and other cell types, and have been reviewed elsewhere (Baird 2005;Lin and Yan 2005). Telomere length in genomic DNA is often determined by terminal restriction fragment (TRF) measurement on Southern blots, or by quantitative polymerase chain reaction (QPCR).…”