Detection of telomerase activity by the TRAP assay and its variants and alternatives. Clin Chim Acta. 2006;371:25-31. [PMID: 16616059 DOI: 10.1016/j.cca.2006.02.039]

Nonradioactive detection of telomerase activity using the telomeric repeat amplification protocol

The telomeric repeat amplification protocol (TRAP) is a two-step process for analyzing telomerase activity in cell or tissue extracts. Recent modifications of this sensitive assay include elimination of radioactivity by using a fluorescently labeled primer instead of a radiolabeled primer. In addition, the TRAP assay has been modified for real-time, quantitative PCR analysis. Here, we describe cost-effective procedures for detection of telomerase activity using a fluorescent-based assay as well as by using real-time PCR. These modified TRAP assays can be accomplished within 4 h (from lysis of samples to analysis of telomerase products).

Irradiation-induced telomerase activity and the risk of lung cancer: a pilot case-control study

BACKGROUND

Telomerase activity is undetectable in most normal somatic cells, but is up-regulated by various mechanisms during tumorigenesis. Telomerase activation enables cells to overcome replicative senescence and maintain telomere stability during cell proliferation. The aim of the study was to evaluate the association between irradiation-induced telomerase activity and the risk of lung cancer.

METHODS

A case-control design was used that measured the baseline and gamma-radiation-induced telomerase activity in cultured peripheral blood lymphocytes from 44 lung cancer patients and 44 healthy controls. The associations between gamma-radiation-inducible telomerase activity and the risk of lung cancer were then analyzed.

RESULTS

The baseline telomerase activity was lower in cases than in controls (0.956 vs 1.222, P = .126). After gamma-radiation the telomerase activity in cases experienced a significant increase over baseline (1.480 vs 0.956, P < .001); the telomerase activity in controls also increased, but on a smaller scale (1.485 vs 1.222, P = .0025). The relative gamma-radiation-induced telomerase activity, defined as the ratio of the net increase of telomerase activity (gamma-radiation induced minus baseline) to the baseline telomerase activity, was significantly higher in cases than in controls (0.730 vs 0.224, P = .0003). When dichotomized, the subjects at the 75th percentile of the relative gamma-radiation-induced telomerase activity in controls, a higher ratio was associated with a significantly increased lung cancer risk (odds ratio [OR], 4.71, 95% confidence interval [CI]: 1.37, 16.21). Moreover, a dose response was observed between the relative gamma-radiation-induced telomerase activity and lung cancer risk. Compared with individuals with the lowest tertile of the relative gamma-radiation-induced telomerase activity, individuals with the second and the highest tertiles of the relative telomerase activity exhibited significantly elevated risks of lung cancer, with adjusted ORs of 12.58 (95% CI: 1.08, 146.86) and 31.08 (95% CI: 2.71, 356.81), respectively (P for trend <.001).

CONCLUSIONS

The pilot-case control study suggested that the gamma-radiation-induced telomerase activation is associated with a significantly increased risk of developing lung cancer. Larger case-control studies and prospective studies are needed to confirm the findings.

Real-time PCR detection of telomerase activity using specific molecular beacon probes

Telomerase is a potentially important biomarker and a prognostic indicator of cancer. Several techniques for assessing telomerase activity, including the telomeric repeat amplification protocol (TRAP) and its modified versions, have been developed. Of these methods, real-time quantitative TRAP (RTQ-TRAP) is considered the most promising. In this work, a novel RTQ-TRAP method is developed in which a telomeric repeats-specific molecular beacon is used. The use of the molecular beacon can improve the specificity of the RTQ-TRAP assay, making the method suitable for studying the overall processivity results and the turnover rate of telomerase. In addition, the real-time, closed-tube protocol used obviates the need for post-amplification procedures, reduces the risk of carryover contamination, and supports high throughput. Its performance in synthetic telomerase products and cell extracts suggests that the developed molecular beacon assay can further enhance the clinical utility of telomerase activity as a biomarker/indicator in cancer diagnosis and prognosis. The method also provides a novel approach to the specific detection of some particular gene sequences to which sequence-specific fluorogenic probes cannot be applied directly. Figure Real-time PCR detection of telomerase activity using specific molecular beacon probes.

Automated capture and on-column detection of biotinylated DNA on a disposable solid support

This work comprises the development of a technique for the capture of single-stranded DNA on a solid support combined with in situ quantification. The capture is based on the strong and selective interaction between biotinylated DNA and streptavidin-coated agarose beads. Sequential Injection in the lab-on-valve format allows for automated manipulation of all components including the building and disposal of bead columns. Detection was accomplished using the OliGreen fluorescent dye and optimization of the assay achieved a limit of detection of 111 pg ssDNA, with a total assay time of roughly 2.5 min per sample.