p53 mutations and exposure to environmental tobacco smoke in a multicenter study on lung cancer.

Biomarker data may provide a way to strengthen the link between environmental tobacco smoke (ETS) exposure and lung cancer shown in epidemiological studies. We conducted a multicenter case-control study to investigate the association between ETS exposure and lung cancer in never-smokers using p53 mutations as a biomarker of tobacco-related carcinogenesis. Paraffin-embedded tissue or fresh tissue samples from 91 never-smokers and 66 smokers with histologically confirmed lung cancer and interview data about smoking habits and ETS exposure were analyzed for mutations in the p53 gene. Statistical analysis was performed using multivariate logistic regression. Among the lifelong nonsmokers, the overall mutation prevalence was 10% (nine cases). Among 48 never-smokers ever exposed to spousal ETS, 13% (six cases) showed mutations. Smokers exhibited 17 (26%) mutations. A 3-fold [odds ratio, 2.9; 95% confidence interval (CI), 1.2-7.2] increased risk of p53 mutation was observed for smokers as compared with all never-smokers combined (i.e., irrespective of ETS exposure). The increase was 4.4-fold (95% CI, 1.2-16.2) when compared with never-smokers without ETS exposure. Among never-smokers, the risk of mutation was doubled (odds ratio, 2.0; 95% CI, 0.5-8.7) for exposure to spousal ETS only, based on 6 exposed cases with mutation and 42 exposed cases without mutation. The risk was 1.5 (95% CI, 0.2-8.8) for those ever exposed to spousal or workplace ETS as compared with those never exposed to spousal or workplace ETS. For smokers, the most common mutation type was G:C to T:A transversion (31%), whereas G:C to A:T transitions were predominant among never smokers (57%). In conclusion, our study indicates a significant 3-4-fold increased risk of p53 mutation in smoking lung cancer cases, and it suggests that mechanisms of lung carcinogenesis in ETS-exposed never-smokers include mutations in the p53 gene, similar to that seen in smokers. However, the mutation patterns observed also suggest a difference between smokers and never-smokers. Clearly, additional investigations of the role of p53 mutation as a biomarker for tobacco-related carcinogenesis, including that related to ETS, are indicated.

Survival in operable non-small-cell lung cancer: role of p53 mutations, tobacco smoking and asbestos exposure.

Validated markers are needed to identify operable lung cancer patients with poor prognosis. About one-half of non-small-cell lung cancers (NSCLCs) carry a mutation in the p53 tumor-suppressor gene. We examined 101 NSCLC patients for surgical stage, completeness of resection, tobacco smoking, asbestos exposure, age, gender and p53 gene mutations as prognostic factors after a follow-up period of 4 years. Cox's multivariate regression model was applied to quantify the associations with overall and cancer-related survival. Patients with a wild-type p53 gene had an overall 4-year survival of 43% and those with a mutated p53 gene, 35%. In squamous-cell carcinoma, stage and heavy smoking, defined as the median of pack-years smoked, had prognostic significance for overall survival. Only stage was associated with poor cancer-related survival. Asbestos exposure was not associated with overall survival or cancer-related survival in squamous-cell carcinoma or adenocarcinoma. In adenocarcinoma, p53 mutation, in addition to stage, emerged as a significant predictor of poor cancer-related survival.

Lung cancer and past occupational exposure to asbestos. Role of p53 and K-ras mutations.

Studies on somatic mutations in lung cancers associated with cigarette smoking and asbestos exposure are few. We investigated prevalence of mutations in the p53 and K-ras genes in lung tumors from smokers with and without asbestos exposure at work. For K-ras mutations, the study was an extension of an earlier analysis. Nearly all of the 105 consecutive patients examined were smokers and had non-small-cell carcinoma of the lung with squamous-cell carcinoma or adenocarcinoma histology. Exposure to asbestos was estimated by pulmonary fiber counts and occupational histories. A pulmonary burden of >/= 1 x 10(6) asbestos fibers per gram of lung tissue, indicating work-related exposure, was found in 32% of the patients for whom fiber-analysis data were available (33 of 102 patients, all men). The statistical analysis showed pulmonary fiber count as the only significant predictor of adenocarcinoma histology, in contrast to squamous-cell carcinoma (smoking-adjusted odds ratio [OR] 3.0, 95% confidence interval [CI] 1.1 to 8.5). The frequency of p53 mutations was 39% (13 of 33) among the asbestos-exposed cases, as compared with 54% (29 of 54) among the nonexposed cases; the difference was not significant, however. In male ever-smokers, a long duration of smoking was associated with p53 mutation (OR 3.2, 95% CI 1.2 to 8.8). In adenocarcinoma, p53 mutations were less prevalent (10 of 30, 33%) as compared with squamous-cell carcinoma (28 of 46, 61%; P = 0.02), whereas a strong and significant association was found between adenocarcinoma and K-ras mutation (OR 37, 95% CI 5.8 to 232, adjusted for smoking and asbestos exposure). Asbestos exposure alone was not significantly associated with increased occurrence of K-ras mutations. In conclusion, the results may primarily reflect the observed excess of adenocarcinoma in the asbestos- exposed patients, and hence the decrease in p53 mutations and increase in K-ras mutations.

Mutations, tissue accumulations, and serum levels of p53 in patients with occupational cancers from asbestos and silica exposure.

In order to determine the relationship between mutations, tissue accumulations, and serum levels of p53 in occupational cancers, we used denaturing gradient gel electrophoresis and DNA sequencing of exons 5-9 of the p53 gene, immunohistochemical analysis for tissue identification of mutant p53 protein, and enzyme-linked immunosorbent assay for serum levels of mutant p53 protein to examine for such alteration in a cohort of individuals with workplace exposure to asbestos or silica, and resultant lung cancers or mesotheliomas. DNA analysis detected mutations in 5 of 18 (28%) tumors, and tissue accumulations of protein were detected in 7 of 20 (35%) tumors; the agreement between mutational and immunohistochemical analyses was significant (kappa = 0.62, P = 0.002). Serum elevations of protein were detected in 4 of 11 (36%) cases with available serum samples; the agreement between tissue alterations and serum elevations was also significant (kappa = 0.71, P = 0.017). In addition, based on the analysis of banked samples, serum results tended to be consistent over time prior to the diagnosis of disease (positive predictive value = 0.67, negative predictive value = 0.83). These results suggest that serum levels of p53 are reasonably accurate in reflecting tissue alterations in p53 at the gene and/ or protein level and may be early biomarkers of disease risk.

Cigarette smoking and p53 mutations in lung cancer and bladder cancer.

We report here a compilation of p53 mutation results from two smoking-related cancers, lung cancer and bladder cancer. The overall mutation frequencies reported for these two types of cancer were relatively similar--50% in lung cancer and 40% in bladder cancer. The compiled data from lung cancer and bladder cancer suggest an increasing proportion of patients with p53 mutations in nonsmokers, former smokers, and current smokers, in that order, in both cancer groups. Taken together, more than half (55% and 56% for lung cancer and bladder cancer, respectively) of the patients who continued smoking (CS), less than 40% (38% and 38%) of those who had stopped smoking before > or = 1 or > or = 5 years) clinical diagnosis (ES), and less than 30% (25% and 29%) of those who were nonsmokers (NS) had a p53 mutation. The differences seen in the mutation frequencies between the three smoking groups did not, however, reach statistical significance (lung cancer--CS vs ES: odds ratio [OR] = 2.0, 95% CI 0.7-5.4; CS vs NS: OR = 3.7, 95% CI 0.4-37; bladder cancer--CS vs ES: OR = 2.1, 95% CI 0.6-7.9; CS vs NS: OR = 3.1, 95% CI 0.7-13). Guanine to thymine transversions were the most common type in lung cancer followed by guanine to adenine transitions. In bladder cancer, on the contrary, G:C to A:T transitions at cytosine-guanine dinucleotide sites were the most frequently detected base substitutions. Analysis of the compiled p53 mutation data suggest that, in addition to lifetime cumulative exposure to cigarette smoke, also stopping smoking for years prior to clinical manifestation of the disease may affect the incidence of p53 mutations. The differences in the mutation profiles appear to support the view that the main genotoxic agents from cigarette smoke exposure may be different in bladder cancer as compared to lung cancer, as suggested previously by DNA adduct studies.

A molecular and epidemiological study on bladder cancer: p53 mutations, tobacco smoking, and occupational exposure to asbestos.

In this study, we found an unexpected association (crude odds ratio = 2.8; 95% confidence interval = 0.9-8.4) between definite work-related exposure to asbestos and carcinoma of the urinary bladder in a small group of patients (n = 28) initially recruited as referents for an epidemiological feasibility study on the occupational causes of lung cancer. We extended the study by using molecular methods to examine mutations in the p53 tumor suppressor gene in the same cases of bladder cancers. The same number of archival samples of transitional cell carcinoma, mainly of grade 3, were added to the analysis. We failed to show any association between occupational exposure to asbestos and p53 mutations among bladder cancer patients. We observed an increasing occurrence of p53 mutations in nonsmokers (5 of 17, 29%), former smokers (8 of 21, 38%), and current smokers (9 of 16, 56%) in that order; however, this was not statistically significant. The most prevalent type of mutation was G:C to A:T transition. Tumor grade was not associated with the frequency of mutations, but the higher stage (T3-T4) tumors appeared to have mutations more frequently than did the less invasive tumors (T1-T2).