Telomere length and telomerase expression in atypical adenomatous hyperplasia and small bronchioloalveolar carcinoma of the lung.

Telomeres are located at the ends of every human chromosome and are subject to shortening at each cycle of cell division in cell senescence and early carcinogenesis. We examined the expression of telomeric DNA in 21 atypical adenomatous hyperplasias (AAHs) and 40 bronchioloalveolar carcinomas (BACs) measuring 2 cm or less in greatest diameter using fluorescent in situ hybridization and the expression of human telomerase reverse transcriptase (hTERT) messenger RNA (mRNA) in 35 AAHs and 37 BACs. The mean numbers of telomeric signals per nucleus were 5.0 in AAH and 7.4 in BAC, each significantly less than for normal cells (14.7; P < .0001), but the mean number of telomeric signals for AAH and BAC was not statistically different (P = .22). In "benign" lung samples, the pattern of expression of hTERT mRNA was barely detected in the nonciliated cells of the bronchioles and alveolar type II cells. Positive expression of hTERT mRNA was recognized in 66% of AAHs and 97% of BACs. Our results demonstrate telomere shortening, indicating its presence in the earliest phase of pulmonary carcinogenesis. Telomere length and telomerase may be involved in carcinogenesis in the lung.