Telomere Length of Human Adult Bronchial Epithelium and Bronchogenic Squamous Cell Carcinoma Measured Using Tissue Quantitative Fluorescence in situ Hybridization

Background: Telomeres are repetitive DNA sequences located at the ends of chromosomes. Chromosomal and genomic instability due to telomere dysfunction has been known to play an important role in the carcinogenesis of some organs. Objectives: The aim of this study was to examine the correlation between smoking and the telomere length of human bronchial epithelial cells in individuals with and without lung cancer. Patients and Methods: We examined 68 non-lung cancer adult autopsy cases and 24 surgically resected cases of lung squamous cell carcinoma. Telomere lengths of the basal cells of bronchial epithelium were measured using the tissue quantitative fluorescence in situ hybridization method and were expressed in normalized telomere-to-centromere ratios (NTCRs). Results: The autopsied individuals included 27 current smokers (CuS), 33 never-smokers (NeS), and 8 ex-smokers (ExS). The NTCRs in the central bronchi of CuS, NeS, and ExS were 1.515, 1.372, and 1.204, respectively. The bronchial epithelial telomeres of CuS were significantly longer than those of non-CuS (NeS + ExS). When the analysis was conducted separately for females and males, a significant difference between CuS and NeS + ExS was recognized only for males. The NTCRs of the bronchial epithelium of lung cancer cases and lung cancer tissue are 1.514 and 1.385, respectively. Conclusions: Our findings suggest that smoking causes telomeric elongation in the bronchial epithelium. Therefore, it appears that the mechanism of carcinogenesis in smoking-related carcinomas may differ from that of many other carcinomas in which genetic instability due to aging-related telomeric shortening is assumed to play a role.