Previously, we observed p53 mutations in the noncancerous tissue that differed from those in lung tumors using the highly sensitive p53 mutation load assay.
Moreover, the reverse correlation between p16INK4a immunostaining and p16INK4a promoter hypermethylation was also only observed in nonsmoking female lung tumors.
Three different patterns in the distribution of p53 mutations in double lung tumours were observed: [A] mutation in only one of the tumours (four cases), [B] different mutations in the tumours (two cases), and [C] same mutation in both tumours (one case).
Secondly, genetic resistance to lung tumor formation appears to segregate with one particular haplotype, which also is deleted preferentially in lung adenocarcinomas of Cdkn2a heterozygous mice.
Western blot analysis showed that stromal cells of lung tumours were characterised by a statistically significantly lower expression level of the p16 protein as compared with that in normal lung stromal cells.
Lung tumors from 204 smokers with non-small cell lung cancer (NSCLC) were analyzed for mutations in exons 5-8 of the p53 gene and genotypes of XPD and XRCC1. p53 mutations were found in 20% (40/204) of the patients.
Alterations of p53 are one of the most common molecular changes found in all types of lung tumors, suggesting a crucial role for p53 in bronchial carcinogenesis.
The mean in vitro bleomycin-induced breaks per cell (a marker of cancer susceptibility) was significantly higher (0.92) for patients who overexpressed p53 in lung tumour tissue than that for patients with no detectable p53 expression in lung tumour tissue (0.65).
In two cases, the lung tumors exhibited a p53 mutation not present in the previously removed primary tumor and were therefore classified as new primary lung cancers.
There was, in general, an excellent concordance between the lung tumor cell lines and their corresponding tumor tissues for morphology (100%), the presence of aneuploidy (100%), immunohistochemical expression of HER2/neu (100%) and p53 proteins (100%), loss of heterozygosity at 13 chromosomal regions analyzed (97%) using 37 microsatellite markers, microsatellite alterations (MAs, 75%), TP53 (67%), and K-ras (100%) gene mutations.
In multivariate analysis, p16 hypermethylation was more prevalent in lung tumours from male than female patients (P = 0.018) and in squamous cell carcinomas than in adenocarcinomas (P = 0.025).
In conclusion, common genetic variation in TP53 could modulate lung cancer pathways, as suggested by the association with lung cancer in African Americans and somatic TP53 mutation frequency in lung tumors.
Analysis of genetic changes in lung tumors showed that the incidence of mutations in the TP53 and KRAS genes and the incidence of LOH in the FHIT gene were significantly greater in smokers versus non-smokers (P < 0.01).
Although all mice developed lung tumors, only 7% of lung tumors were adenocarcinomas in wild-type mice, whereas 22 and 26% of lung tumors were adenocarcinomas in p53 transgenic or K-ras heterozygous deficient mice.
Losses of heterozygosity on chromosome 11 were observed at several loci surrounding the p53 tumor-suppressor gene (Trp53) in 12 of 17 mammary tumors and 2 of 8 lung tumors.
Previous studies have suggested that certain genetic polymorphisms, specifically the Xeroderma pigmentosum group D (XPD) gene codon 751 and the X-ray repair cross-complementing group 1 (XRCC1) gene codon 399 polymorphisms, were associated with an increased risk of lung cancer, and, in some studies, with a greater risk for mutations in the p53 tumor suppressor gene in lung tumors.
We evaluated the potential of two common Type I (273H, contact) and Type II (175H, conformational) TP53 mutations to induce lung tumors in transgenic mice, as well as K-ras status, and other driver mutations in these tumors.
Herein, we review the epidemiologic connection between tobacco exposure and cancer, the molecular basis of p53 mutation in lung cancer, and the normal molecular and cellular roles of p53 that are abrogated during lung tumor development and progression as defined by in vitro and in vivo studies.