ABSTRACT
Considerable interest has been focused on telomerase because of its potential use in assays for cancer diagnosis, and for anti-telomerase drugs as a strategy for cancer chemotherapy. A number of assays based on the polymerase chain reaction (PCR) have been developed for evaluation of telomerase activity. To overcome the disadvantages of the conventional telomerase assay [telomeric repeat amplification protocol (TRAP)] related to PCR artifacts and troublesome post-PCR procedures, we have developed a telomeric repeat elongation (TRE) assay which directly measures telomerase activity as the telomeric elongation rate by biosensor technology using surface plasmon resonance (SPR). 5'-Biotinylated oligomers containing telomeric repeats were immobilized on streptavidin-pretreated dextran sensor surfaces in situ using the BIACORE apparatus. Subsequently, the oligomers associated with the telomerase extracts were elongated in the BIACORE apparatus. The rate of TRE was calculated by measuring the SPR signals. We examined elongation rates by the TRE assay in 18 cancer and three normal human fibroblast cell lines, and 12 human primary carcinomas and matching normal tissues. The elongation rates increased in a concentration- and time-dependent manner. Those of cancer cells were two to 10 times higher than fibroblast cell lines and normal tissues. Telomerase activities and its inhibitory effects of anti-telomerase agents as measured by both the TRE and TRAP assays showed a good correlation. Our assay allows precise quantitative comparison of a wide range of human cells from somatic cells to carcinoma cells. TRE assay is suitable for practical use in the assessment of telomerase activity in preclinical and clinical trials of telomerase-based therapies, because of its reproducibility, rapidity and simplicity.
Subject(s)
Repetitive Sequences, Nucleic Acid/genetics , Surface Plasmon Resonance/methods , Telomerase/metabolism , Telomere/genetics , Cell Line , Estrogen Antagonists/pharmacology , Humans , Polymerase Chain Reaction/methods , Reproducibility of Results , Reverse Transcriptase Inhibitors/pharmacology , Tamoxifen/pharmacology , Telomerase/antagonists & inhibitors , Telomere/metabolism , Tumor Cells, Cultured , Zidovudine/pharmacologyABSTRACT
Extraskeletal Ewing's sarcoma is a rare tumor. The most common sites of occurrence are on the trunk, extremities, and retroperitoneum. This type of tumor is well characterized by recurrent chromosomal translocation such as t (11;22) (q24;q12) (EWSR1/FLI1) or t (21;22) (q22;q12) (EWSR1/ERG) and overexpression of MIC2/CD99 on tumor cell membrane. We describe the first reported case of an esophageal extraskeletal Ewing's sarcoma with confirmation from immunohistochemical and molecular diagnoses. A 56-year-old man developed a polypoid tumor located in the lower part of the esophagus. The tumor was composed of small-sized round cells showing prominent fibrillar cytoplasmic processes. Intracytoplasmic glycogen was detected in all the tumor cells. Immunoreactivity for MIC2/CD99 was positive on the membrane of all tumor cells. A reverse transcriptase-polymerase chain reaction followed by sequencing revealed an EWSR1/ERG chimeric transcript, which combined EWSR1 exon 10 with ERG exon 6. The present report added a new entity of esophageal small round cell tumor.
