Telomerase is a ribonucleoprotein that synthesizes telomeric DNA onto chromosomal ends using an RNA component as a template. Extension of telomeric repeats by telomerase prevents telomere shortening with cell divisions and contributes to chromosomal stability, possibly leading to immortalization of the cells. In the present study, we used a telomerase assay to detect primary lung cancer in broncho-alveolar lavage fluid (BALF). A total of 58 BALF samples were examined by telometric repeat amplication protocol assay. Thirty-five (29 cancers, 2 salcoidoses, 2 pulmonary tuberculoses and 2 normal samples) of 58 (60.3%) cases were found to be positive for telomerase activity. The sensitivity of telomerase activity was 78.4%, compared with 64.7% of BALF cytology. Among 37 primary lung cancer patients diagnosed histopathologically, 24 had positive cytology and 29 had positive telomerase activity. The number increased to 32 patients when cytodiagnosis and telomerase activity were considered. Of patients in whom the presence of primary lung cancer was strongly suspected clinically, although there was no histopathological evidence, two were telomerase-positive, initially diagnosed as normal by cytological examination and histological examination but finally diagnosed as primary lung cancer (adenocarcinoma) in subsequent histological examination using operation specimens. These findings suggest that telomerase assay using BALF samples might be a useful screening method for primary lung cancer especially when combined with BALF cytology.

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