K-ras and rho A mutations in malignant pleural effusion

Mutations of the Kristen ras (K-ras) gene have been implicated in the pathogenesis of human lung cancer, especially adenocarcinoma, and have been proposed to be a prognostic factor. The K-ras mutation in codon 12 is detectable even in cell-free fluids by using the enriched polymerase chain reaction (PCR) technique. On the other hand, based on experimental results, the rho A mutation in codon 14 is also proposed to be oncogenic as observed in the K-ras mutation. Malignant pleural effusion is a common complication of lung cancer. We studied the point mutation of K-ras codon 12 and rho A codon 14 using enriched PCR in specimens of pleural effusion. Forty patients with pleural effusion were enrolled in this study. The causes of pleural effusion were non-small cell lung cancer (18 cases), small cell lung cancer (6 cases), malignant mesothelioma (2 cases), metastatic lung tumor (5 cases), thymoma (1 case), malignant lymphoma (1 case), and pleuritis tuberculosa (7 cases). The K-ras mutation was detected in 4 of 14 cases with adenocarcinoma, 1 of 3 cases with squamous cell carcinoma, 1 of 1 case with large cell carcinoma, and 1 of 5 cases with metastatic lung tumor, respectively. The rho A mutation was not detected in any pleural effusion examined in this study. Our study demonstrates the usefullness of pleural effusion as a clinical specimen for a search of point mutation of oncogenes. The K-ras codon 12 mutation is readily detected in pleural effusion, and the demonstration of this mutation has potentially important implications for the diagnosis of malignant pleural effusion.     

High frequency of K-ras mutations in normal appearing lung tissues and sputum of patients with lung cancer

To evaluate the possible use of mutant ras as a biomarker for lung cancer, we have analyzed “normal appearing” lung tissue, lung tumor, lung metastases and sputum samples from patients with non-small cell lung cancer (NSCLC). As a control, we used lung tissue and sputum samples from patients without oncological diseases or lung disorders. Our analyses were performed with the aid of enriched PCR (EPCR), a method which enables detection of ras mutation even if present at low incidence. EPCR identified K-ras codon 12 mutations in 10% of lung tissues obtained from patients with no lung diseases, whereas the same mutation was detected in 60% of samples of normal appearing lung tissues obtained from patients with NSCLC, 62% of NSCLC tumors and 80% of metastases. Analysis of sputum samples of patients with NSCLC identified 47% to harbor mutant ras allele, whereas 12.5% of controls diagnosed with non-oncological lung diseases carried this mutation. Most of these mutations were detected with the aid of EPCR only, indicating that a minority of cells in a given sample harbor this mutation. The ability to detect K-ras codon 12 mutation in 60% of lung tissue samples and in 47% of sputum samples taken from patients with lung cancer (as compared with 10% and 12.5% of respective controls) points to the potential use of ras mutation as a biomarker for exposure and possible identification of patients who may be at a higher risk of developing lung cancer. © 1995 Wiley-Liss, Inc.     

K-ras activation in non-small cell lung cancer in the dog.

To investigate the role of K-ras mutations in canine non-small cell lung cancer, we first determined the nucleotide sequence of the normal canine K-ras gene and then examined 21 canine lung tumors for activating K-ras mutations. Canine K-ras was analyzed by direct sequencing of polymerase chain reaction products generated with oligonucleotide primers derived from the human K-ras sequence. Four nucleotide differences were found between the canine and human K-ras sequence from position 5 to 211. The deduced amino acid sequence of the canine gene was identical to that of the human. Activated K-ras alleles were detected in 5 of the 21 canine lung tumors examined. The activating lesions were point mutations, predominantly in codon 12. Of the 14 adenocarcinomas examined, 2 (14%) had K-ras mutations. Two of 5 (40%) adenosquamous carcinomas and the only large cell carcinoma also contained activated alleles. The overall frequency of K-ras point mutation in non-small cell lung cancer (25%) is similar to that reported in human non-small cell lung cancer. We conclude that K-ras activation by point mutation is associated with, but not necessary for, non-small cell lung cancer development in the dog.     

肺癌患者组织和痰液中p53基因、K-ras基因突变

 目的　探讨p53、K-ras基因在肺癌患者癌组织及相应痰液中改变情况及其联合检测在肺癌早期诊断中的价值。方法　对59例肺癌组织和14例肺部良性组织及相应痰液,应用PCR-SSCP-银染法检测了p53基因第5～8外显子突变情况;应用PCR-RFLP法对K-ras基因突变进行了检测。结果　p53基因在肺癌组织中突变率为37.3%,K-ras基因在肺腺癌突变率为48.0%,其它类型肺癌突变率仅为8.8%。相应痰液中两基因突变率分别为33.8%和44.0%,与组织中的突变率无明显差异,P<0.01。良性组织及相应痰液中两基因均无突变。吸烟患者的突变率(48.7%,68.5%)明显高于非吸烟患者的突变率(15.0%,11.1%),P<0.01;两基因的联合检测在肺癌的早期诊断中的价值(54.2%)明显优于单基因的检测,P<0.05。结论　痰液和组织中的基因突变率基本相似,即痰液中脱落细胞的分子遗传学改变能反映肺组织情况。因此以痰液为目标多基因的联合检测可能有助于肺癌的诊断。     

Detection of K-ras mutations of bronchoalveolar lavage fluid cells aids the diagnosis of lung cancer in small pulmonary lesions.

An increased prevalence of K-ras oncogene mutation in lung adenocarcinoma has been shown by PCR-primer-introduced restriction with enrichment for mutation alleles (PCR-PIREMA) experiments. In the present study we investigated whether this method is useful for the diagnosis of lung cancer in small pulmonary lesions, which are difficult to diagnose cytologically as lung cancer by bronchoscopic examination. We examined bronchoalveolar lavage fluid (BALF) cells from 33 patients with single nodular pulmonary lesions of less than 2 cm in diameter (measured on chest computed tomography scans) for K-ras (codon 12) mutation, by PCR-PIREMA. Transbronchial fiberscopic examinations had not revealed lung cancer cytologically in any of the patients. The final diagnoses for the 33 lesions were 20 adenocarcinomas, 5 cases of focal fibrosis, 5 cases of pneumonia, 1 case of tuberculosis, 1 hamartoma, and 1 case of lymph node swelling. BALF cell lysates were amplified and digested with a restriction enzyme to detect the K-ras oncogene. Only the normal K-ras was observed after the first amplification and digestion for each of the 33 patients. Three amplifications and digestions were performed for each sample. We detected mutation of K-ras in BALF cells from 15 (75%) of 20 lung cancer patients and in cells from only 4 (31%) of 13 patients with nonmalignant lesions. The detection rate of the K-ras mutation in lung cancer was significantly greater than that in nonmalignant lesions (P = 0.012). Our results indicate that the detection of the codon 12 K-ras mutation in BALF cells by PCR-PIREMA aids the diagnosis of lung cancer in patients with small pulmonary lesions with negative cytological findings.     

Differential activation of ras genes by point mutation in human colon cancer with metastases to either lung or liver

To study the possible role of ras oncogene activation in the dissemination of colon cancer, we determined point mutations in codons 12, 13 and 61 in K- and N-ras in 3 groups of tumors: (A) primary tumors of patients who had undergone surgery for Dukes' B (early-stage) colon cancer, (B) primary tumors and metastases from patients undergoing resection of isolated lung metastases and (C) primary tumors and metastases from patients undergoing resection of isolated liver metastases. In 129 samples from 93 patients, 54 (42%) were positive for point mutations in either K- or N-ras. Most mutations (89%) were found in the K-ras gene. In group A (n = 50) ras point mutations were detected in 16 cases (32%) (15 in K-ras and 1 in N-ras). Thirteen out of 23 cases in group B (57%) were positive for a ras point mutation: 10 in K-ras and 3 in N-ras. In group C (n = 20), point mutations in codon 12 of K-ras, but none in H- or N-ras, were found in 10 cases (50%). In 31 cases the primary tumors from the metastases in groups B and C were available for analysis and 15 contained a ras point mutation (48%). Not all mutations were present in both the primary tumor and the metastasis. In 3 instances, a mutation was detected in the metastasis but not in the primary tumor, whereas in 1 case a mutation was found in the primary tumor.     

癌基因K-ras、C-myc、erbB-2的激活与非小细胞肺癌组织学类型相关性研究

为探讨癌基因突变、扩增与非小细胞肺癌发生及类型间的关系，应用核酸杂交的方法检测了63伤1肺手术标本中（腺癌19例，鳞癌23例，腺鳞癌3例，大细胞癌3例，小细胞癌3例，其它12例）三种癌基因（c－myc、K－ras、erbB－2）的扩增及突变。实验结果显示：50％（24／48）的非小细胞癌分别出现三种癌基因的激活；31．6％（6／19）的腺癌出现K－ras12密码子突变及K－ras扩增；30．4％（7／23）的鳞癌有erbB－2扩增；10．4％（5／48）的非小细胞癌存在c－myc扩增。提示K－ras突变可能为肺腺癌所特有，而erbB－2扩增是肺鳞癌发生的重要因素。     

K-ras oncogene mutation in cancer and precancerous lesions of the gallbladder

BACKGROUND AND OBJECTIVES: To determine whether K-ras mutation plays any role in the development and progression of gallbladder cancer, or has any clinical or pathological significance in gallbladder cancer patients, we investigated the presence and incidence of this mutation in the normal mucosa, and precancerous and cancerous lesions of the gallbladder. METHODS: DNA was obtained from normal mucosa, dysplastic mucosa, primary cancer tissues, and metastatic lymph nodes that were identified and microdissected from the paraffin blocks of 20 gallbladder cancer cases. K-ras codon 12 mutations were investigated using a modified two-step polymerase chain reaction and the restriction fragment length polymorphism method, and by direct sequencing with an automated sequencer. RESULTS: K-ras mutations were detected in the tissues of 10 out of the 20 patients. A mutation was present in the dysplastic epithelium associated with the primary carcinoma in 3 out of 12 specimens, in metastatic carcinoma in 1 out of 5 patients, and in primary carcinoma in 8 out of 20 patients. Mutation was found only once in the dysplastic, noncancerous epithelium, and only once in a metastatic tumor although not detectable in the primary cancer. Direct sequencing showed that the mutations were G to C substitutions (GGT-->CGT) at the first site of codon 12, except in two cases (GGT-->TGT). There were no correlations between K-ras mutations and clinicopathological factors. CONCLUSIONS: K-ras mutations were detected in half of the gallbladder cancer cases. We suggest that K-ras mutation may play a role in the development of premalignant lesions or early carcinogenesis in some gallbladder cancers. We were unable to find any evidence that K-ras mutation plays any role in tumor progression or metastasis, or that it has any clinicopathological significance.     

非小细胞肺癌中EGFR和K-ras基因突变检测

目的:探讨不同类型非小细胞肺癌的EGFR和K-ras基因突变情况及其与肺癌相关临床病理特征的关系。方法:用厦门艾德ADxARMS试剂盒进行98例非小细胞肺癌患者肿瘤组织中EGFR（18,19,20,21外显子）基因和K-ras（12,13,61密码子）基因突变的检测。所有患者均未接受过吉非替尼的治疗。结果:98例样本中31例发生了EGFR基因突变,突变率为31.6%（31/98）,其中15例为19外显子缺失,13例为21 L858R外显子点突变,3例为20外显子突变,1例为18外显子突变。其中1例既有19外显子缺失突变,又有20外显子突变。腺癌中EGFR基因突变率较鳞癌、腺鳞癌、大细胞癌高。女性患者EGFR基因突变率较男性高。不吸烟患者EGFR基因突变率较吸烟患者高。低分化腺癌患者EGFR基因突变率较中、高分化患者高。21例发生了K-ras基因突变（21.4%）,其中12、13、61密码子均发现突变。突变率腺癌较鳞癌、腺鳞癌、大细胞癌高,与是否吸烟、患者性别、分化程度均无相关性。结论:非小细胞肺癌患者EGFR基因突变检出率较高,K-ras基因突变率较低,且两者不存在同时突变,EGFR基因突变与肺癌组织学类型、分化程度、性别等相关。K-ras基因突变与组织学类型相关。     

Detection of human papilloma virus (HPV) and K-ras mutations in human lung carcinomas

The purpose of our study was to assess the prevalence and prognostic significance of HPV infection as well as K-ras codon 12 point mutations in lung cancer. Patients diagnosed with lung carcinoma between 1988 and 1992 (N=99) were selected. HPV detection and typing was performed by PCR from paraffin-embedded tissues, while mutations in codon 12 of K-ras gene were detected using the restriction fragment length polymorphism (RFLP) analysis. The prevalence of HPV infection was 15%, while K-ras codon 12 point mutations were found in 18% of the specimens examined. In 50% of the HPV-positive cases, K-ras gene mutation coexisted. HPV 18 was the most frequent type. No correlation was found between K-ras mutation and HPV infection with sex, age and clinical outcome of the patient, or the histological type and the differentiation grade of the tumor. An association was found between K-ms codon 12 point mutations and the stage of the tumor, occurring more frequently at stage III (p=0.037). Infection with potentially oncogenic HPV types could co-operate with K-ras gene activation in the progression of the disease, since K-ras activation by point mutations seems to be a late event in lung carcinogenesis.     

Mutational analysis of ras gene family in lung cancer in Thai

H-, K- and N-ras gene mutations were analyzed in lung cancer from Thai patients. Thirteen out of 58 cases (22%) harbored the mutations. Ten cases showed K-ras gene mutations at codon 12, 1 case presented a mutation at codon 13 and another case exhibited a mutation at codon 63. Silent mutations of N-ras gene in codons 57 and 62 were seen in one patient, whilst no H-ras mutation was found in these patients. Bases change in K-ras gene were G right curved arrow T transversion (62%), G right curved arrow A transition (15%) and G right curved arrow C transition (15%), whereas T right curved arrow G transversion and A right curved arrow G transition were detected in N-ras mutant gene.     

Detection of p53 and K-ras mutations in sputum of individuals exposed to smoky coal emissions in Xuan Wei County, China

Lung cancer mortality rates in the Xuan Wei County population are among the highest in China and are associated with exposure to indoor emissions from the burning of smoky coal. Previous studies of lung tumors from both non-smoking women and smoking men in this region showed high frequencies of mutations, consisting mostly of G-->T transversions in the p53 tumor suppressor gene and K-ras oncogene, suggesting that these mutations were caused primarily by polycyclic aromatic hydrocarbons. In this study sputum samples from 92 individuals with no evidence of lung cancer from Xuan Wei County were screened for p53 and K-ras mutations. Sputum cells were collected on glass slides by sputum cytocentrifugation, stained and cytopathologically analyzed. Cytologically non-malignant epithelial cells were taken from each sputum sample using a laser capture microdissection microscope and molecularly analyzed. Cells taken from the sputum of 15 (16.3%) individuals were mutation positive, including 13 (14.1%) individuals each with a p53 mutation, 1 (1.1%) individual with a K-ras mutation and 1 (1.1%) individual with a p53 and a K-ras mutation. p53 mutations were found in both the sputum of individuals with evidence of chronic bronchitis (3 of 46 or 6.5%) and those without evidence of this disease (11 of 46 or 23.9%). Therefore, mutations in the p53 gene and, to a lesser extent, the K-ras gene were frequent in non-malignant epithelial cells taken from the sputum of individuals without evidence of lung cancer who were exposed to smoky coal emissions in Xuan Wei County and were at a high risk for developing the disease.     

Frequent RASSF1A promoter hypermethylation and K-ras mutations in pancreatic carcinoma

Recently, we have characterized the Ras association domain family 1A gene (RASSF1A) at the segment 3p21.3, which is frequently lost in variety of human cancers and epigenetically inactivated in many types of primary tumors, such as lung, breast, kidney, prostate and thyroid carcinomas. Here, we investigated the methylation status of the RASSF1A CpG island promoter in the pathogenesis of pancreatic cancer. RASSF1A hypermethylation was detected in 29 out of 45 (64%) primary adenocarcinomas, in 10 out of 12 (83%) endocrine tumors and in eight out of 18 (44%) pancreatitis samples. In seven out of eight pancreas cancer cell lines, RASSF1A was silenced and was retranscribed after treatment with 5-aza-2'-deoxycytidine. Additionally, we analysed the aberrant methylation frequency of cell cycle inhibitor p16(INK4a) and K-ras gene mutations in the pancreatic samples. p16 inactivation was detected in 43% of adenocarcinomas, in 17% of neuroendocrine tumors, in 18% of pancreatitis and in 63% of pancreas cancer cell lines. K-ras mutations were detected in 16 out of 45 (36%) primary adenocarcinomas. Pancreatic adenocarcinomas with K-ras mutation have significantly less RASSF1A methylation and vice versa (P=0.001, chi(2) test). In conclusion, our data indicate that inactivation of the RASSF1A gene is a frequent event in pancreatic cancer and suggest an inverse correlation between RASSF1A silencing and K-ras activation.     

Low frequency of p53 and k-ras codon 12 mutations in non-small cell lung carcinoma (NSCLC) tumors and surgical margins

AIMS AND BACKGROUND: Lung cancer is one of the most common cancers and has became a predominant cause of cancer-related death throughout the world. The k-ras codon 12 mutation, which is the most common lung cancer mutation, is found in 15 to 30% of all lung cancers. Furthermore, the p53 gene has a very important role in the biological properties of tumor cells, and it is mutated in about 50% of non-small cell lung cancers. Residual tumor cells remain in surgical margins diagnosed as tumor free by histopathological techniques, and they can play a role in forming any local recurrence. Molecular methods may be exploited that are sensitive enough to detect small numbers of tumor cells. METHODS: In the present study, we examined p53 gene mutations and k-ras codon 12 mutations from the tumor samples and surgical margins of 34 non-small-cell lung cancer patients. P53 gene mutations were analyzed by single strand conformational polymorphism analysis, heterodublex analysis and DNA sequencing. K-ras codon 12 mutations were analyzed by the mutagenic PCR-restricted fragment length polymorphism method. RESULTS: A p53 mutation was detected only in primary tumors of 3 out of 34 patients (8.82%). These mutations were clustered in exon 5. Moreover, a k-ras codon 12 mutation was detected in both the primary tumor and the surgical margin tissues of 2 out of 34 patients (5.88%). CONCLUSIONS: The detected mutation rate was low, in the range given in the literature. We think that different mechanisms related to other genes and individual genetic differences might play a role in cancer formation in our study group. We believe that molecular studies are necessary to identify biomarkers and to determine genetic alterations in histopathologically normal surgical margins.     

Application of the p53 and K-ras gene mutation patterns for cytologic diagnosis of recurrent lung carcinomas

BACKGROUND: Cytologic specimens are one of the most important materials for lung carcinoma diagnosis, because they can be used in mass screening for lung carcinoma and early detection of cancer recurrence by examination of sputum and pleural fluid. METHODS: To prove the potentiality of the cytologic specimens to be subjected to molecular detection of recurrent lung carcinomas, the authors enrolled 16 patients who had undergone surgical treatment for lung carcinoma with recurrence detected by malignant pleural fluid. First, they examined K-ras gene and p53 tumor suppressor gene abnormalities in resected tumors by polymerase chain reaction-based single-strand conformation polymorphism (PCR-SSCP) analysis. Next, using a microdissection method, they investigated the use of cytologic specimens such as pleural fluid for the detection of recurrence by finding the same mutations observed in the initially resected tumor. RESULTS: Seven abnormally shifted bands were detected among six patients by PCR-SSCP analysis of surgical materials. Five of 7 abnormally shifted bands (71.4%) also were detected from microdissected malignant cells in cytologic smears. In two cases, they detected mutations by using single malignant cells in pleural fluid. CONCLUSIONS: The authors successfully detected the same mutations in recurrent cytologic specimens as those in the initially resected tumors by PCR-SSCP analysis. These findings suggest that the p53 and K-ras gene mutation patterns are effective markers for the detection of recurrent lung carcinoma in cytologic specimens. Cancer (Cancer Cytopathol) Copyright 2000 American Cancer Society.     

Overexpression of p53 protein and point mutation of K-ras genes in primary carcinoma of the small intestine

Primary carcinoma of the small intestine is rare and represent about 0.5% of all gastrointestinal malignancies. The aim of this study was to examine the biological characteristics of primary carcinoma of the small intestine by immunohistochemical and nested polymerase chain reaction methods. Thirty-five primary carcinomas (12 in the duodenum and 23 in the jejunum or ileum) from 35 patients were studied clinicopathologically and examined for overexpression of p53 protein. In 22 of these 35 cases, point mutation at codon 12 of the K-ras gene was detected by the nested polymerase chain reaction and restriction fragment length polymorphism method. All the duodenal carcinomas were well-differentiated type and the rate of these carcinomas was significantly higher than that of jejunal or ileal carcinomas (100% vs. 65%). Fourteen cases showed overexpression of p53 (40%), and p53 tended to be expressed more frequently in poorly-differentiated type (71%) compared to well-differentiated type (30%). Only 2 out of 22 carcinoma cases showed K-ras gene mutation, and both were duodenal carcinomas. These findings suggest that p53 plays a major role in the progression of carcinoma of the small intestine, whereas the role of K-ras mutation is much less significant.     

Detection of codon 61 point mutations of the K-ras gene in lung and colorectal cancers by enriched PCR

Mutation of the Kirsten ras (K-ras) gene is one of most common alterations in solid tumors including lung and colorectal cancers. We developed new enriched PCR-RFLP assay to detect mutations of K-ras codon 61 at the 1st and 2nd letters and non-enriched PCR-RFLP assay to detect the 3rd letter mutation. One mutant allele among 10(3) wild-type alleles was detected by enriched PCR-RFLP assay, while one mutant in 10 wild-type alleles was detected by non-enriched PCR-RFLP assay for codon 61 3rd letter. We then examined K-ras codon 12, 13 and 61 mutations in lung and colorectal cancers using these assays. K-ras codon 12 mutation was detected in 10 of 109 (9%) lung cancer and 19 of 83 (23%) colorectal cancer cases. K-ras codon 13 mutation was detected in 2 of 83 (2%) colorectal and 0 of 109 NSCLC cases, respectively. There was no K-ras codon 61 mutation in either type of cancer. Our results demonstrate that enriched PCR-RFLP is a sensitive assay to detect K-ras codon 61 mutation, however, it was extremely rare in lung and colorectal cancers, suggesting organ-specific pathways in mutagenesis of the ras gene family.     

结直肠癌原发灶与转移灶K-ras基因突变的比较分析

背景与目的：K-ras基因突变是抗表皮生长因子受体(epidermal growth factor receptor,EGFR)靶向治疗的重要负性预测因子。本研究拟对结直肠癌原发灶与转移灶中K-ras基因状态的一致性进行比较,以探讨目前临床K-ras检测的科学性与严谨性。方法：收集复旦大学附属肿瘤医院手术切除的结直肠癌原发灶及转移灶石蜡包埋组织76对,提取DNA,经过PCR扩增后,对产物进行基因序列分析,检测结直肠癌中K-ras基因外显子2基因序列。结果：76例患者中有15例结直肠癌原发灶与转移灶的K-ras基因突变情况不一致。76例结直肠癌原发灶有31例发生突变,突变率为40.8%,其中第13号密码子突变16例,第12号密码子突变15例;76例结直肠癌转移灶有31例发生突变,突变率为40.8%,其中第13号密码子突变15例,第12号密码子突变16例。结论：结直肠癌原发灶和转移灶中K-ras基因状态并不一致,且存在19.7%的表达差异率,提示通过检测原发灶K-ras基因表达状态来确定针对转移灶的西妥昔单克隆抗体药物选择存在不严谨性,需要进一步完善。     

肺癌患者吸烟量与痰液细胞p53和Ki—ras基因突变的关系

目的　了解痰液细胞癌基因突变是否与肺癌患者的吸烟量有相关性。方法　将痰液 0 .5毫升加入痰处理液制备细胞沉淀液 ,酚氯仿提取DNA ;应用SSCP PCR银染和RFLP PCR方法对痰液中p5 3、K ras突变情况进行检测。统计肺癌患者的香烟消耗量 ,分析p5 3、K ras突变与吸烟量的关系。结果　在确诊的 110例肺癌中 ,存在p5 3或K ras基因突变者有 76例 ,突变率达 69.1% ,其中 16例为p5 3和K ras基因均有突变。全组中有 71例重度吸烟者吸烟指数 (≥ 40 0支·年 ) ,71例中 5 5例有p5 3或K ras基因突变 ,突变率达 77.5 % ,显著高于非吸烟组 (P <0 .0 0 1) ;p5 3和K ras突变患者的平均吸烟指数分别达到 861和 63 0支·年 ;而未突变的平均吸烟指数为 2 84和 5 5 4支·年 ,二者之间有显著性差异 ( χ2 =3 6.5 6,P =0 .0 0 2 ,双尾检验 )。结论　痰液细胞癌基因突变检测具有简便、实用、可行的特点 ,吸烟的肺癌患者中癌基因突变率显著高于非吸烟的肺癌患者 ,提示吸烟尤其是重度吸烟可能是支气管癌基因突变的主要原因之一 ,值得临床进一步开展深入的研究。