Frequency and distinctive spectrum of KRAS mutations in never smokers with lung adenocarcinoma

PURPOSE: KRAS mutations are found in approximately 25% of lung adenocarcinomas in Western countries and, as a group, have been strongly associated with cigarette smoking. These mutations are predictive of poor prognosis in resected disease as well as resistance to treatment with erlotinib or gefitinib. EXPERIMENTAL DESIGN: We determined the frequency and type of KRAS codon 12 and 13 mutations and characterized their association with cigarette smoking history in patients with lung adenocarcinomas. RESULTS: KRAS mutational analysis was done on 482 lung adenocarcinomas, 81 (17%) of which were obtained from patients who had never smoked cigarettes. KRAS mutations were found in 15% (12 of 81; 95% confidence intervals, 8-24%) of tumors from never smokers. Similarly, 22% (69 of 316; 95% confidence intervals, 17-27%) of tumors from former smokers, and 25% (21 of 85; 95% confidence intervals, 16-35%) of tumors from current smokers had KRAS mutations. The frequency of KRAS mutation was not associated with age, gender, or smoking history. The number of pack years of cigarette smoking did not predict an increased likelihood of KRAS mutations. Never smokers were significantly more likely than former or current smokers to have a transition mutation (G-->A) rather than the transversion mutations known to be smoking-related (G-->T or G-->C; P < 0.0001). CONCLUSIONS: Based on our data, KRAS mutations are not rare among never smokers with lung adenocarcinoma and such patients have a distinct KRAS mutation profile. The etiologic and biological heterogeneity of KRAS mutant lung adenocarcinomas is worthy of further study.     

p53 and K-ras mutations in lung cancers from former and never-smoking women

Somatic p53 mutations are common in lung cancer. Active cigarette smoking is positively correlated with the total frequency of p53 mutations and G:C to T:A transversions on the nontranscribed (DNA coding) strand. Mutational hotspots within the p53 gene, e.g., codon 157, have been identified for tobacco-related lung cancer, whereas these same mutations are found rarely in other cancers. Such data implicate specific p53 mutations as molecular markers of smoking. Because limited data exist concerning the p53 mutation frequency and spectra in ex-smokers and nonsmokers, we have analyzed p53 and K-ras mutations in 126 lung cancers from a population-based case-control study of nonsmoking (n = 117) or ex-smoking (n = 9) women from Missouri with quantitative assessments of exposure to environmental tobacco smoke. Mutations in the p53 gene were found in lung cancers from lifetime nonsmokers (19%) and ex-smokers (67%; odds ratio, 9.08; 95% confidence interval, 2.06-39.98). All deletions were found in tumors from patients who were either ex-smokers or nonsmokers exposed to passive smoking. The G:C to A:T transitions (11 of 28; 39%) were the most frequent p53 mutations found and clustered in tumors from lifetime nonsmokers without passive smoke exposure. The incidence of K-ras codon 12 or 13 mutations was 11% (14 of 115 analyzed) with no difference between long-term ex-smokers and nonsmokers. These and other results indicate that p53 mutations occur more commonly in smokers and ex-smokers than in never-smokers. Such comparisons provide additional evidence of genetic damage caused by tobacco smoke during lung carcinogenesis.     

Chromosomal alterations in lung adenocarcinoma from smokers and nonsmokers

The etiology of lung tumors arising in nonsmokers remains unclear. Although mutations in the K-ras and p53 genes have been reported to be significantly higher in smoking-related lung carcinomas, in the present study we performed a more comprehensive analysis in search of additional genetic changes between lung adenocarcinoma from tobacco- and non-tobacco-exposed patients. We selected a matched cohort of 18 lifetime nonsmoking and 27 smoking patients diagnosed with primary adenocarcinoma of the lung and searched for chromosomal alterations in each tumor by testing normal and tumor tissue with 54 highly polymorphic microsatellite markers located on 28 different chromosomal arms. Allelic losses or gains at chromosomal arms 3p (37 versus 6%), 6q (46 versus 12%), 9p (65 versus 22%), 16p (28 versus 0%), 17p (45 versus 11%), and 19p (58 versus 16%) were present significantly more often in adenocarcinomas from smokers than from nonsmokers. Chromosomal arms showing allelic imbalance in lung tumors from nonsmokers were rare but occurred more often at 19q (22%), 12p (22%), and 9p (22%). The FAL (fractional allelic loss or gain) is defined as the percentage of chromosomal arm losses/gains among the total informative chromosomal arms. Tumors from smokers harbored higher levels of FAL (13 (48%) of 27 showed FAL > or = 0.3) compared with the lung tumors from the nonsmoker patients (2 (11%) of 18 showed FAL > or = 0.3; P = 0.02; odds ratio, 0.13; 95% confidence interval, 0.01-0.79). Our data demonstrate that widespread chromosomal abnormalities are frequent in lung adenocarcinoma from smokers, whereas these abnormalities are infrequent in such tumors arising in nonsmokers. These observations support the notion that lung cancers in nonsmokers arise through genetic alterations distinct from the common events observed in tumors from smokers.     

Patterns of allelic loss differ in lung adenocarcinomas of smokers and nonsmokers

Cigarette smoking is the most important cause of lung cancer, however approximately 10% of patients with lung cancer have no history of smoking. While the molecular pathogenesis of smoking associated lung carcinogenesis is becoming well characterized, the pathogenesis of lung cancer in nonsmokers is not. We designed a study to examine the pathogenesis of adenocarcinoma in nonsmokers by determining if loss of heterozygosity (LOH) in tumors of nonsmokers differs from those of smokers. We evaluated six cases of primary adenocarcinoma in never smokers and six selected cases in smokers, matched by clinical and histological criteria. LOH in tumor DNA relative to nonmalignant lung DNA was determined at 52 microsatellites located on ten chromosomal loci. The extent of allelic loss in smokers, as measured by fractional allelic loss (FAL), was compared with nonsmokers. LOH was more frequent in the tumors of nonsmokers than of smokers with mean FAL of 46% in nonsmokers and 28% in smokers (P<0.05). Increased LOH in nonsmokers was most pronounced at chromosomes: 3p, 8p, 9p, 10p, and 18q. Since this study compared allelic loss between lung and tumor-bearing lung, less frequent LOH in smokers' tumors can be interpreted to suggest LOH was already present in the nonmalignant lung of smokers and fewer additional instances of allelic loss were present in the tumors of smokers. Our results suggest that the early steps of lung carcinogenesis differ in nonsmokers compared with smokers. In addition, the chromosomal sites of LOH may identify genes important for lung carcinogenesis in nonsmokers.     

Prevalence and spectrum of p53 mutations associated with smoking in breast cancer

To explore the role of smoking in breast cancer, we undertook a population-based study to evaluate the prevalence and spectrum of p53 mutations in the breast tumors of smokers and nonsmokers. We evaluated 456 archival invasive breast tumors for mutations in exons 4-8 of the p53 gene, using single-strand conformational polymorphism analysis and manual sequencing. Statistical analyses were performed to determine the association of p53 mutations with clinical and smoking characteristics. Of 108 mutations identified, 77 (71%) were point mutations and 31 (29%) were deletions or insertions. A higher prevalence of p53 mutations was found in the breast tumors of current smokers (36.5%; P = 0.02) compared with never smokers (23.6%), whereas fewer mutations were found in former smokers (16.2%; P = 0.09). After adjustment for age, race, menopausal status, clinical stage, tumor size, and family history of breast cancer, current smokers were significantly more likely to harbor any p53 mutation [odds ratio (OR), 2.11; 95% confidence interval (CI), 1.17-3.78], p53 transversions (OR, 3.37; 95% CI, 1.03-11.06), and G:C-->T:A transversions (OR, 10.53; 95% CI, 1.77-62.55) compared with never smokers. Stage at diagnosis did not account for the increase in p53 mutation-positive breast cancer among current smokers. Former smokers were also more likely than never smokers to harbor G:C-->T:A transversions (OR, 2.43; 95% CI, 0.37-15.73), although this association was not statistically significant. Among former smokers, the prevalence of p53 mutations varied with time since quitting: former smokers who quit smoking for longer than 1 year had a lower prevalence of p53 mutations (10.5% for 1-5 years and 12.9% for >5 years) than those who had stopped smoking within the year of their cancer diagnosis (26.3%). Our results indicate that cigarette smoking appears to modify the prevalence and spectrum of p53 mutations in breast tumors. Moreover, the difference in mutational spectra observed between smokers and nonsmokers is suggestive of the genotoxic effects of smoking in breast tissue.     

Mutations in the epidermal growth factor receptor gene are linked to smoking-independent, lung adenocarcinoma

Epidermal growth factor receptor (EGFR) mutations are a potential predictor of the effectiveness of EGFR inhibitors for the treatment of lung cancer. Although EGFR mutations were reported to occur with high frequency in nonsmoking Japanese adenocarcinoma patients, the exact nature has not been fully elucidated. We examined EGFR gene mutations within exons 18-21 and their correlations to clinico-pathological factors and other genetic alterations in tumour specimens from 154 patients who underwent resection for lung cancer at Kyoto University Hospital. Epidermal growth factor receptor mutations were observed in 60 tumours (39.0%), all of which were adenocarcinoma. Among the patients with adenocarcinoma (n=108), EGFR mutations were more frequently observed in nonsmokers than former smokers or current smokers (83.0, 50.0, 15.2%, respectively), in women than men (76.3 vs 34.0%), in tumours with bronchio-alveolar component than those without bronchio-alveolar component (78.9 vs 42.9%), and in well or moderately differentiated tumours than poorly differentiated tumours (72.0, 64.4, 34.2%). No tumours with EGFR mutations had any K-ras codon 12 mutations, which were well-known smoking-related gene mutations. In conclusion, adenocarcinomas with EGFR mutation had a distinctive clinico-pathological feature unrelated to smoking. Epidermal growth factor receptor mutations may play a key role in the development of smoking-independent adenocarcinoma.     

Relationship between K-ras oncogene activation and smoking in adenocarcinoma of the human lung

To investigate a possible relationship between the exposure to tobacco smoke and the presence of ras point mutations, we examined lung adenocarcinoma samples from 27 smokers and from 27 nonsmokers. Activating point mutations in K-ras (also known as KRAS2) and N-ras (also known as NRAS) were determined by using the polymerase chain reaction and oligonucleotide hybridization to detect the mutated sequences. Mutations were more often found in adenocarcinomas obtained from smokers (eight of 27) than in adenocarcinomas obtained from nonsmokers (two of 27) (P = .044, Fisher's exact test). All mutations were present in K-ras codon 12. None of the other parameters examined differed significantly between the ras-positive and ras-negative groups. We conclude that exposure to carcinogenic agents in tobacco smoke is an important factor in the induction of point mutations in K-ras in human lung adenocarcinomas, but that K-ras mutations may also infrequently occur in tumors of non-smokers.     

Expression of CYP1A1 gene in patients with lung cancer: evidence for cigarette smoke-induced gene expression in normal lung tissue and for altered gene regulation in primary pulmonary carcinomas

The major polycyclic aromatic hydrocarbon inducible-cytochrome P4501A1 gene (CYP1A1) is presumed to be important in pulmonary carcinogenesis and toxicology because its product, the cytochrome P4501A1-dependent (CYP1A1-dependent) monooxygenase, transforms selected xenobiotics (including polycyclic aromatic hydrocarbon procarcinogens in cigarette smoke) to potent carcinogenic metabolites. CYP1A1 messenger RNA (mRNA) expression has not, however, been previously demonstrated in human pulmonary tissue. This report defines CYP1A1 gene expression in normal lung tissue and primary pulmonary carcinoma tissue obtained at thoracotomy from 56 patients with lung cancer. When Northern blot hybridization analyses were performed, 17 of 19 (89%) and zero of five (0%) samples of normal lung tissue from active cigarette smokers and nonsmokers, respectively, expressed the normal 2.8-kilobase CYP1A1 mRNA. In addition, a time-dependent decrease in expression of the CYP1A1 gene was noted in normal lung tissue from individuals who were former smokers, with a decrease in expression occurring as early as 2 weeks following cessation of cigarette smoking. Expression became undetectable in all patients who had stopped smoking more than 6 weeks prior to study. When CYP1A1 gene expression was evaluated in lung cancers, mRNA levels were detectable in one of four (25%) tumors from nonsmokers; two of 24 (8%) tumors from former smokers; and seven of 15 (47%) tumors from cigarette smokers. In addition, an approximately 10-kilobase CYP1A1 RNA species, which was not detectable in normal lung tissue, was observed in five of ten (50%) of the lung cancers that expressed the CYP1A1 gene.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mutations within the tyrosine kinase domain of EGFR gene specifically occur in lung adenocarcinoma patients with a low exposure of tobacco smoking

Somatically acquired mutations in the epidermal growth factor receptor (EGFR) gene in lung cancer are associated with significant clinical responses to gefitinib, a tyrosine kinase inhibitor that targets EGFR. We screened the EGFR in 469 resected tumours of patients with lung cancer, which included 322 adenocarcinomas, 102 squamous cell carcinomas, 27 large cell carcinomas, 13 small cell carcinomas, and five other cell types. PCR with a specific condition was performed to identify any deletion in exon 19, while mutant-allele-specific amplification was performed to identify a mutation in codon 858 of exon 21. EGFR mutations were found in 136 cases (42.2%) with adenocarcinoma, in one case with large cell carcinoma, and in one case with pleomorphic carcinoma. An in-frame deletion in exon 19 was found in 62 cases while an L858R mutation was found in 77 cases. In the 322 cases with adenocarcinoma, these mutations were more frequently found in women than in men (P=0.0004), in well differentiated tumours than in poorly differentiated tumours (P=0.0014), and in patients who were never smokers than in patients who were current/former smokers (P<0.0001). The mutation was more frequently observed in patients who smoked 相似文献   

The relevance of "Nonsmoking-associated lung cancer" in India: A single-centre experience

Background: Lung cancer remains a major cause of morbidity and mortality worldwide, accounting for more deaths than any other cancer cause. Aim: The aim of this study was to analyze the clinical profile and the epidemiological trends in lung cancer patients from a single centre with an emphasis on the smoking practices. Materials and Methods: This is a retrospective analysis of prospectively collected data of 258 consecutive hospital in-patients with a proven diagnosis of lung cancer at a tertiary care oncology centre between 2003 and 2007. Results: The median age of patients in our study was 56 years; the male to female ratio was approximately 3.5:1. Non-small-cell lung cancer (NSCLC) was the predominant histology in 224 patients; the histology in the remaining 34 patients was small-cell carcinoma. Within NSCLC, the most common histology was adenocarcinoma followed by squamous cell carcinoma. One hundred and two patients were never-smokers as compared to 156 patients who were ever-smokers. Among the smokers, the majority of them were found to be cigarette smokers compared to 28.2% bidi smokers. There was a very significant correlation found with adenocarcinoma among nonsmokers, and with squamous cell carcinoma among the smokers compared to non-smokers. Conclusions: Our study suggests that the epidemiology of lung cancer in India is possibly changing, with close to 40% of our lung cancer patients being nonsmokers. More importantly, our study reflects the global trend of rise in adenocarcinoma histology. These observations need to be substantiated in similar studies of larger magnitude, preferably population-based.     

Promoter hypermethylation of the O6-methylguanine-DNA methyltransferase gene: more common in lung adenocarcinomas from never-smokers than smokers and associated with tumor progression

Adenocarcinoma (AC) is the most common type of lung cancer diagnosed in the United States, comprising up to 40% of tumors in smokers and 50-80% of tumors in never-smokers. Exposures to cigarette smoke, direct or second-hand, and radiation in the form of radon progeny are the major risk factors for lung AC in both smokers and never-smokers. The goal of the current study was to determine the prevalence for O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation in a large sample of central or peripheral ACs from smokers (n = 157), former uranium miners (n = 34), and never-smokers (n = 46). The mutation rate at codon 12 of the K-ras gene was determined to assess whether activation of this oncogene was associated with MGMT methylation. The overall prevalence for MGMT methylation was 51%. Significantly more tumors from never-smokers than smokers exhibited MGMT methylation (66 versus 47%, respectively). In contrast, exposure to radon through uranium mining did not affect the prevalence for methylation. The frequency of MGMT methylation was increased significantly in association with tumor stage. K-ras mutations were detected in 24% of all ACs and 22, 24, and 28% of tumors from never-smokers, smokers, and miners, respectively. Alterations in both the K-ras and MGMT genes were seen in only 11% of ACs. Kaplan-Meier survival estimates did not reveal any difference between patient survival with or without MGMT methylation. In contrast, survival was significantly reduced over the initial 60 months after diagnosis for patients with a transition mutation in the K-ras gene compared with those with a transversion mutation. This investigation demonstrates that MGMT promoter hypermethylation is a common event in the progression of early stage AC of the lung. We have shown that the incidence of MGMT methylation was significantly higher in never-smokers than smokers and have detected a higher frequency of mutations within the K-ras gene than previously reported in never-smokers. This study also suggests that K-ras activation is independent of MGMT methylation.     

Incidence and possible clinical significance of K-ras oncogene activation in adenocarcinoma of the human lung

47 tumor samples, 45 of which were obtained at thoracotomy for non-small cell lung cancer were examined for mutational activation of the oncogenes H-ras, K-ras, and N-ras. A novel, highly sensitive assay based on oligonucleotide hybridization following an in vitro amplification step was employed. ras gene mutations were present in nine of 35 adenocarcinomas of the lung (all K-ras), in two of two lung metastases of colorectal adenocarcinomas (1 x K-ras, 1 x N-ras) and in one adenocarcinoma sample obtained at autopsy (H-ras). All K-ras and H-ras mutations were in either position 1 or 2 of codon 12, while the N-ras mutation was in position 2 of codon 61. The potential clinical significance of K-ras activation was analyzed using the combined results of this and of our earlier study (S. Rodenhuis et al., New Engl. J. Med., 317: 929-935, 1987). Lung adenocarcinomas with K-ras mutations tended to be smaller and were less likely to have spread to regional lymph nodes at presentation. With a median follow up of 10 months, survival data are still immature. None of six adenocarcinomas of nonsmokers had a K-ras mutation and only one of four who had stopped smoking more than 5 years before. We conclude that mutational K-ras activation is present in about a third of adenocarcinomas of the lung and that the mutational event may be a direct result of one or more carcinogenic ingredients of tobacco smoke. Studies involving larger numbers of patients are required to confirm the association of K-ras activation with smoking and the inverse relation with tumor progression.     

Increased loss of chromosome 9p21 but not p16 inactivation in primary non-small cell lung cancer from smokers

Epidemiological studies have demonstrated a causal association between tobacco use and carcinoma of the lung, and some genetic targets of the carcinogens in cigarette smoke have been defined recently. We further examined the effect of cigarette smoking on the frequency of allelic losses on chromosome 9p21 and the incidence of p16 inactivation. Chromosomal loss at 9p21-24 was determined by microsatellite analysis using 14 markers in 47 patients with non-small cell lung cancer. In addition, p16 gene inactivation was determined by DNA sequence analysis, methylation-specific PCR, and immunohistochemistry. Tumors from a group of nonsmokers (n = 14) were compared with tumors from a group of smokers (n = 33) matched for cell type, tumor stage, and gender. Allelic loss encompassing the p16 locus was present significantly (P = 0.01) more often in smokers (23 of 33 smokers, 70%) than in nonsmokers (4 of 14 nonsmokers, 28%). No significant differences in the frequency of p16 inactivation were observed between smokers and nonsmokers (45% versus 36%). However, homozygous deletion of the p16 gene locus and point mutation of p16 gene were only observed in tumors from smokers, whereas the p16 gene was inactivated in tumors from nonsmokers only through promoter hypermethylation. Thus, inactivation of the p16 gene is a common event in all non-small cell lung cancer, but the mechanism of gene alteration differs between smokers and nonsmokers. The significant link between tobacco and loss of the p16 locus identifies additional genetic targets of smoking in the pathogenesis of lung cancer.     

Distribution of p53 and K-ras mutations in human lung cancer tissues

Studies were performed to examine the mutational pattern of K-ras exons 1 and 2 and p53 exons 5-8 in lung cancer tissues from 27 Chinese patients (10 smokers, 17 non-smokers) using single-stranded conformational polymorphism and DNA sequencing. K-ras mutations were found in 13/27 tumors (48%); all mutations were clustered in exon 1 and distributed between codons 9 and 32. The frequency and number of patients with K-ras mutations between smokers and non-smokers were not different, except that a high frequency of G --> A transitions (11/11) was found in non-smokers. Among cell types, K-ras mutations were found in 7/13 (54%) squamous cell carcinoma (SC) and 5/12 (42%) adenocarcinoma (AC) patients. A --> T transversions (all six transversions) were present only in SC. In p53, 18/27 (67%) tumors contained mutations in exons 7 and 8, frequently at codons 226, 270, 275 and 281. The number of tumors with p53 mutations in smokers (70%) and in non-smokers (65%) was similar, and the mutation frequency did not differ except for a higher number of G --> A (6/7) and T --> C (5/6) transitions in non-smokers. Among cell types, the number of tumors with p53 mutations was 9/13 (69%) in SC and 8/12 (67%) in AC. The A --> G (11/16) transitions and A --> C (4/4) transversions in p53 were more frequent in SC than in AC (P < 0.04 for A --> G; P < 0.02 for A --> C). The varying mutation patterns in both the K-ras and p53 genes between smokers and non-smokers and among cell types suggest that other than cigarette smoke, environmental and dietary factors may also be involved in the genesis of lung cancer among these patients.      

Distinct epidermal growth factor receptor and KRAS mutation patterns in non-small cell lung cancer patients with different tobacco exposure and clinicopathologic features.

PURPOSE: This study evaluated the mutational profile of epidermal growth factor receptor (EGFR) and KRAS in non-small cell lung cancers in Hong Kong and determined their relation with smoking history and other clinicopathologic features. EXPERIMENTAL DESIGN: Mutational profile of exons 18 to 21 of EGFR and codons 12, 13, and 61 of KRAS were determined in 215 adenocarcinomas, 15 squamous cell (SCC), and 11 EBV-associated lymphoepithelioma-like carcinomas (LELC). RESULTS: EGFR mutations were prevalent in adenocarcinomas (115 of 215), uncommon in LELC (1 of 11), and not found in SCC (P < 0.001). Among adenocarcinomas, mutations were associated with nonsmokers (83 of 111; P < 0.001), female gender (87 of 131; P < 0.001), and well-differentiated (55 of 86) compared with poorly differentiated (11 of 41) tumors (P < 0.001). Decreasing mutation rates with increasing direct tobacco exposure was observed, with 74.8% (83 of 111) in nonsmokers, 61.1% (11 of 18) in passive, 35.7% (10 of 28) in previous, and 19.0% (11 of 58) in current smokers. There were 53% amino acid substitutions, 43% in-frame deletions, and 4% insertions. Complex patterns with 13% double mutations, including five novel substitutions, were observed. For KRAS, mutations occurred in adenocarcinoma only (21 of 215) and were associated with smokers (11 of 58; P = 0.003), men (14 of 84; P = 0.009) and poorly differentiated (7 of 41) compared with well-differentiated (4 of 86) tumors (P = 0.037). EGFR and KRAS mutations occurred in mutually exclusive tumors. Regression analysis showed smoking history was the significant determinant for both mutations, whereas gender was a confounding factor. CONCLUSION: This study shows EGFR mutations are prevalent in lung adenocarcinoma and suggests that it plays an increasing oncogenic role with decreasing direct tobacco damage.     

GSTM1, P53 and K-ras molecular detection in resectable non-small cell lung cancer by denaturing gradient gel electrophoresis-bronchoalveolar lavage fluid analysis

BACKGROUND: Understanding molecular abnormalities could potentially lead to novel investigational approaches in the molecular epidemiology of lung cancer. These might include the identification of patients at high risk for primary NSCLC and the surveillance of patients with known NSCLC who are being treated using lung-sparing surgical strategies. MATERIALS AND METHODS: The PCR-Denaturing Gradient Gel Electrophoresis (DGGE) strategy was used for primary tumors and corresponding bronchalveolare lavage (BAL) samples. RESULTS: We recruited 36 consecutive patients with NSCLC, 28 (77.7%) males and 8 females (22.3%). DGGE showed a good rate of accuracy in the genetic screening of K-ras and p53 mutations in BAL specimens. Specific mutations were more often detected in BAL fluid from patients with not peripheral tumors than parenchymal or peripheral tumors (p53: 85.7%, p=0.0004; K-ras: 75%, p=0.001). p53 mutations were more frequent in BAL fluid from squamous cell carcinomas (22%) than from adenocarcinomas (15%). A significant correlation was observed between null GST-Ml genotype and p53 overall mutations (p=0.0003), K-ras mutations (p=0.02), non peripheral tumors (p=0.04) and smoking habits (p=0.002). CONCLUSIONS: We observed that null GSTMl genotype is strongly related to p53 mutations. Individuals at high risk for primary NSCLC, such as heavy smokers or individuals exposed to occupational carcinogens, could be screened by BAL-analysis for cancer biomarkers of susceptibility like GSTM-1 in large scale molecular epidemiology studies.     

Implications and prognostic value of K-ras mutation for early-stage lung cancer in women

BACKGROUND: Because there is no clear consensus as to the predictive value of K-ras gene mutation for survival in patients with lung cancer, we examined the occurrence of K-ras mutations in a large, prospective case series of non-small-cell lung cancer (NSCLC). Our goals were to define the patient characteristics associated with K-ras mutation and to determine whether mutation of this gene might be a biomarker of patient prognosis. METHODS: Consecutive, newly diagnosed patients with lung cancer treated with potentially curative resection over a 4-year period were recruited for study. The mutation status of K-ras codon 12 in each patient's tumor DNA was determined by means of polymerase chain reaction-restriction fragment length polymorphism analysis of archived pathology specimens. Analyses were restricted to adenocarcinoma. RESULTS: There was a statistically significant association between female sex and K-ras mutation after adjustment for carcinogen exposures (odds ratio = 3.3; 95% confidence interval [CI] = 1.3-7.9); mutations were found only in smokers. Comparison of Kaplan-Meier curves indicated a strong association between K-ras mutation and decreased patient survival (two-sided P =.009); analysis stratified by pathologic staging groups revealed that this association was statistically significant only for stage I tumors (two-sided P =.002). Cox proportional hazards modeling indicated that K-ras codon 12 mutation was a statistically significant predictor of patient survival, after adjustment for the effects of age, sex, and stage (risk ratio = 1.8; 95% CI = 1.1-3.1). CONCLUSIONS: After adjustment for environmental exposures, non-small-cell lung tumors in women appear to be more likely than those in men to harbor K-ras mutations, suggesting a possible role of estrogen exposure in either the initiation or the selection of K-ras mutant clones in adenocarcinoma. In addition, our data suggest that K-ras codon 12 mutation is a marker of aggressive NSCLC, as evidenced by its association with decreased patient survival, particularly for early-stage disease.     

Mutations in the tyrosine kinase domain of the epidermal growth factor receptor in non-small cell lung cancer.

We evaluated somatic genetic alterations in the kinase domain of the EGFR gene in the tumors of 219 non-small cell lung cancer patients of primarily Caucasian and African American origins. We identified 26 patients (12%) whose tumors had a mutation in the EGFR gene, and 11 (5%) patients carried novel genomic variations consistent with germ-line polymorphisms. All but one mutation were identified in Caucasian patients affected with adenocarcinoma. EGFR mutations were more frequent in women and in nonsmokers, but a significant portion of the affected patients were men (12 of 26) and current or past smokers accounted for half of the patients affected (13 of 26). Screening subjects with EGFR mutations may identify patients whose tumors could respond to targeted therapy using tyrosine kinase inhibitors.     

Genetic alterations in p53 and k-ras in lung-cancer in relation to histopathology of the tumor and smoking history of the patient

The inactivation of the p53 suppressor gene and the activation of the ras proto-oncogenes are frequent events in non-small cell lung cancer as well as in many other solid neoplasms in man. Somatic mutations in exons 5-8 of the p53 gene were detected in 59% (30/51) of the squamous cell carcinoma and in 38% (14/37) of the adenocarcinoma tumors using GC-clamped, non-radioactive denaturing gradient gel electrophoresis (DGGE). The mutations in the exons 5 and 8 represented larger proportion of the alterations in squamous cell carcinoma tumors (p=0.04; Fisher's exact test, two-tailed); in the adenocarcinoma tumors, mutations were most common in the exon 7 of p53. Most of the identified mutations (25/39; 64%) are predicted to cause an amino acid substitution. Mutations leading to the premature termination of translation were more frequent in adenocarcinoma (6/14) than in squamous cell carcinoma (3/30) tumors (p=0.02). In adenocarcinoma, also base substitutions in the K-ras gene were detected more often (18/37; 49%) than in squamous cell carcinoma (p<0.01). However, a mutation both in p53 and Kras was detected in only 4% of the lung tumors which does not support importance of co-operation between the genes in vivo. Mutations in p53 and K-ras did not correlate with tumor differentiation in either histological type. In squamous cell carcinoma, mutations in p53 showed relation to pack years smoked whereas in adenocarcinoma, mutations in the K-ras gene were associated with cigarette consumption. G to T transversion was the most common type of base substitution in both genes (31% in p53 and 53% in K-ras).