Molecular identification of individuals at high risk for lung cancer

Genotoxicity of tobacco smoke and tobacco smoke condensate: a review

This report reviews the literature on the genotoxicity of mainstream tobacco smoke and cigarette smoke condensate (CSC) published since 1985. CSC is genotoxic in nearly all systems in which it has been tested, with the base/neutral fractions being the most mutagenic. In rodents, cigarette smoke induces sister chromatid exchanges (SCEs) and micronuclei in bone marrow and lung cells. In humans, newborns of smoking mothers have elevated frequencies of HPRT mutants, translocations, and DNA strand breaks. Sperm of smokers have elevated frequencies of aneuploidy, DNA adducts, strand breaks, and oxidative damage. Smoking also produces mutagenic cervical mucus, micronuclei in cervical epithelial cells, and genotoxic amniotic fluid. These data suggest that tobacco smoke may be a human germ-cell mutagen. Tobacco smoke produces mutagenic urine, and it is a human somatic-cell mutagen, producing HPRT mutations, SCEs, microsatellite instability, and DNA damage in a variety of tissues. Of the 11 organ sites at which smoking causes cancer in humans, smoking-associated genotoxic effects have been found in all eight that have been examined thus far: oral/nasal, esophagus, pharynx/larynx, lung, pancreas, myeoloid organs, bladder/ureter, uterine cervix. Lung tumors of smokers contain a high frequency and unique spectrum of TP53 and KRAS mutations, reflective of the PAH (and possibly other) compounds in the smoke. Further studies are needed to clarify the modulation of the genotoxicity of tobacco smoke by various genetic polymorphisms. These data support a model of tobacco smoke carcinogenesis in which the components of tobacco smoke induce mutations that accumulate in a field of tissue that, through selection, drive the carcinogenic process. Most of the data reviewed here are from studies of human smokers. Thus, their relevance to humans cannot be denied, and their explanatory powers not easily dismissed. Tobacco smoke is now the most extreme example of a systemic human mutagen.

Genetic abnormalities in plasma DNA of patients with lung cancer and other respiratory diseases

The detection of tumour-associated genetic alterations in plasma DNA has been proposed as a simple method for the early diagnosis of lung cancer and for identifying individuals at high risk of lung cancer who might be included in screening or chemoprevention programmes. To evaluate the practicality of this approach, we screened a panel of 16 plasma DNA markers in a lung cancer population to identify those with the highest genetic alteration rate. These were then used to study plasma DNA in 206 hospital outpatients with lung cancer and other respiratory diseases. Plasma and lymphocyte DNA were isolated from blood samples collected from hospital outpatients. Polymerase chain reaction was carried out with 16 microsatellite markers covering chromosomal regions 3p, 8p, 9p, 13q and 17p, using DNA from 32 lung cancer patients. The 3 markers most commonly affected were selected for use in a larger study of 86 lung cancer patients and 120 patients with other respiratory diseases. In the pilot study, 3 primer pairs (D3S1300, D3S1560, D8S201) together detected genetic alterations in plasma DNA in 60% of lung cancer patients. In the larger study, significantly higher genetic alteration rates were observed in lung cancer patients than in patients with other respiratory diseases for the two markers D3S1560 and D8S201. The overall genetic alteration rate was 69% in the lung cancer patients and 42% in the patients with other respiratory diseases (p < 0.001). Analysis of plasma and lymphocyte DNA to detect genetic alterations typical of lung cancer is possible in large studies. The genetic alteration rate we found in lung cancer patients was comparable with other studies. Although the genetic alteration rate was significantly higher in the lung cancer than the respiratory disease patients, it did not have good positive predictive value in this population. Longitudinal studies are required to determine whether genetic changes in plasma DNA of non-cancer patients indicate a high risk of later lung cancer.

Preneoplastic lesions of the lung

Lung cancer is the leading cause of cancer deaths worldwide. If we can define and detect preneoplastic lesions, we might have a chance of improving survival. The World Health Organization has defined three preneoplastic lesions of the bronchial epithelium: squamous dysplasia/carcinoma in situ; atypical adenomatous hyperplasia; and diffuse idiopathic pulmonary neuroendocrine cell hyperplasia. These lesions are believed to progress to squamous cell carcinoma, adenocarcinoma and carcinoid tumors, respectively. In this review we summarize the data supporting the preneoplastic nature of these lesions, and delve into some of the genetic changes found in atypical adenomatous hyperplasia and squamous dysplasia/carcinoma in situ.

Perspective: cell differentiation theory may advance early detection of and therapy for lung cancer

Many of these deaths could be prevented if there were better screening methods to uncover the disease when it is limited and most responsive to intervention. Novel biomarkers of early-stage disease are therefore needed. By applying the principle of "oncology recapitulates ontogeny", we have discovered three homeobox (HOX) genes that are inappropriately expressed in the majority of lung tumors. Understanding the role of these inappropriately expressed genes in lung epithelial cell carcinogenesis may not only augment early detection, but may also offer new avenues of treatment of this disease.