Activation of the K-ras protooncogene in lung tumors from rats and mice chronically exposed to tetranitromethane

Dominant transforming genes were detected in lung tumors from Fischer 344 rats and C57BL/6 X C3H F1 mice chronically exposed by inhalation to tetranitromethane, a highly volatile compound used in several industrial processes. The rat lung neoplasms were classified as adenocarcinomas, squamous cell carcinomas (epidermoid carcinomas), or adenosquamous carcinomas. The mouse lung tumors were classified as papillary adenocarcinomas or adenomas. In both species, the tumors were morphologically similar to lung tumors in humans. The transfection assay using NIH/3T3 mouse fibroblasts detected transforming genes in 74% (14 of 19) of the rat lung tumors and in 100% (4 of 4) of the mouse lung tumors. Southern blot analysis indicated that transforming gene was an activated K-ras protooncogene in both species. The first exon of the K-ras gene in normal DNA and in DNA from two cell lines transformed by tumor DNA was compared by cloning and sequencing the gene. Experiments showed that there was a GC----AT transition in the second base of the 12th codon of the K-ras oncogene in the two transfectant DNAs. Oligonucleotide hybridization indicated that all of the rat and mouse transfectants had this activating lesion. Additional tumor DNA was then tested for the presence of a mutated allele with the GC----AT transition. All of the rat tumors tested and all of the mouse tumors tested had this mutation present. Hybridization using the normal oligonucleotide sequence around the 12th codon indicated that the normal allele was also present in the majority of the tumors, suggesting that the loss of normal allele is not necessary for the development of neoplasia. One rat lung tumor had no normal allele present, possibly suggesting that this tumor could have been in a more advanced stage than the other tumors. This is the first study to detect activated protooncogenes in rodent tumors induced under conditions which mimic human exposure to a chemical in the workplace. Tetranitromethane may exert its carcinogenic action by both activation of the K-ras oncogene and stimulation of cell proliferation by its irritant properties.     

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.     

Cellular protoonocogenes are infrequently amplified in untreated non-small cell lung cancer

To examine a potential contribution of protooncogene abnormalities other than point-mutational activation of the K-ras protooncogene in the classification of non-small cell lung cancer, amplification of cellular protooncogenes was studied in 47 lung tumour specimens obtained at thoracotomy and in four lung tumour cell lines. The primary tumours included 21 adenocarcinomas, nine large-cell carcinomas, 13 epidermoid carcinomas, one carcinoid and three metastases of primaries outside the lung. The copy numbers per haploid genome of 11 protooncogenes in every tumour sample were determined: H-ras, K-ras, N-ras, c-myc, N-myc, L-myc, erbB, mos, myb, ncu (erbB-2) and ral amplifications. The c-myc gene was amplified 5-7-fold in two adenocarcinomas, the H-ras gene 3 5-fold in one adenocarcinoma, while the K-ras and the neu gene were amplified in lung metastases from a colorectal and a breast cancer primary respectively. None of the tumours with an amplified protooncogene simultaneously harboured a mutationally activated K-ras gene. We conclude that amplification of the investigated protooncogenes is a rare event in non-small cell lung cancer. In view of the two c-myc amplifications detected, a systematic study of c-myc expression levels in non-small cell lung cancers appears worthwhile.     

Activation of K-ras by codon 13 mutations in C57BL/6 X C3H F1 mouse tumors induced by exposure to 1,3-butadiene

1,3-Butadiene has been detected in urban air, gasoline vapors, and cigarette smoke. It has been estimated that 65,000 workers are exposed to this chemical in occupational settings in the United States. Lymphomas, lung, and liver tumors were induced in female and male C57BL/6 X C3H F1 (hereafter called B6C3F1) mice by inhalation of 6.25 to 625 ppm 1,3-butadiene for 1 to 2 years. The objective of this study was to examine these tumors for the presence of activated protooncogenes by the NIH 3T3 transfection and nude mouse tumorigenicity assays. Transfection of DNA isolated from 7 of 9 lung tumors and 7 of 12 liver tumors induced morphological transformation of NIH 3T3 cells. Southern blot analysis indicated that the transformation induced by 6 lung and 3 liver tumor DNA samples was due to transfer of a K-ras oncogene. Four of the 7 liver tumors that were positive upon transfection contained an activated H-ras gene. The identity of the transforming gene in one of the lung tumors has not been determined but was not a member of the ras family or a met or raf gene. Eleven 1,3-butadiene-induced lymphomas were examined for transforming genes using the nude mouse tumorigenicity assay. Activated K-ras genes were detected in 2 of the 11 lymphomas assayed. DNA sequencing of polymerase chain reaction-amplified ras gene exons revealed that 9 of 11 of the activating K-ras mutations were G to C transversions in codon 13. One liver tumor contained an activated K-ras gene with mutations in both codons 60 and 61. The activating mutation in one of the K-ras genes from a lymphoma was not identified but DNA sequence analysis of amplified regions in proximity to codons 12, 13, and 61 demonstrated that the mutation was not located in or near these codons. Activation of K-ras genes by codon 13 mutations has not been found in any lung or liver tumors or lymphomas from untreated B6C3F1 mice. Thus, the K-ras activation found in 1,3-butadiene-induced B6C3F1 mouse tumors probably occurred as a result of genotoxic effects of this chemical. The oncogenes most frequently detected in human pulmonary adenocarcinomas are K-ras genes. Activated K-ras genes have also been found in some human lymphomas. This suggest that activation of K-ras may be important in the induction of human pulmonary adenocarcinomas and lymphomas.(ABSTRACT TRUNCATED AT 400 WORDS)     

Multiple K-ras codon 12 mutations in cholangiocarcinomas demonstrated with a sensitive polymerase chain reaction technique.

By using a modified polymerase chain reaction strategy, we have devised an approach to detect a K-ras oncogene mutated at codon 12 in the presence of 1000 normal alleles. This is a considerable improvement in sensitivity on previous assays. Application of this assay to 15 cholangiocarcinomas showed that all contained a K-ras mutation to codon 12 and that nine of the tumors contained two or more mutations. In 11 cases, mutations were present in less than 10% of the cells in the sample. In common with pancreatic adenocarcinomas, in which 75 to 95% of cases contain a mutation in K-ras, cholangiocarcinomas show a very high frequency of ras gene mutation, but within a tumor only a fraction of cells contain a ras mutation. The presence of multiple mutations and the low frequency of mutant alleles in the samples argue against K-ras mutations being the initiating genetic lesion in this tumor, but suggest that ras gene mutation is involved in the stepwise progression of neoplastic cells to full malignancy.     

The differential effects of mutant p53 alleles on advanced murine lung cancer

We report a direct comparison of the differential effects of individual p53 mutations on lung tumor growth and progression, and the creation of a murine model of spontaneous advanced lung adenocarcinoma that closely recapitulates several aspects of advanced human pulmonary adenocarcinoma. We generated compound conditional knock-in mice with mutations in K-ras combined with one of three p53 alleles: a contact mutant, a structural mutant, or a null allele. p53 loss strongly promoted the progression of K-ras-induced lung adenocarcinomas, yielding a mouse model that is strikingly reminiscent of advanced human lung adenocarcinoma. The influence of p53 loss on malignant progression was observed as early as 6 weeks after tumor initiation. Furthermore, we found that the contact mutant p53R270H, but not the structural mutant p53R172H, acted in a partially dominant-negative fashion to promote K-ras-initiated lung adenocarcinomas. However, for both mutants, loss-of-heterozygosity occurred uniformly in advanced tumors, highlighting a residual tumor-suppressive function conferred by the remaining wild-type allele of p53. Finally, a subset of mice also developed sinonasal adenocarcinomas. In contrast to the lung tumors, expression of the point-mutant p53 alleles strongly promoted the development of sinonasal adenocarcinomas compared with simple loss-of-function, suggesting a tissue-specific gain-of-function.     

K-ras activation in neoplasms of the human female reproductive tract

The role of cellular oncogenes in the development of epithelial tumors of the human female reproductive tract has not previously been extensively studied. DNAs isolated from ten human uterine, 13 ovarian, and four cervical neoplasms and from three cell lines derived from endometrial adenocarcinoma were investigated by dot blot hybridization after polymerase chain reaction amplification of ras gene sequences and in some cases by NIH 3T3 transfection. Transforming activity was found in two of nine endometrial adenocarcinomas, but none of seven ovarian carcinomas and none of four cervical carcinomas showed transforming activity. K-ras sequences with a GGT----GAT mutation in codon 12 were demonstrated in both transformants derived from endometrial carcinoma. K-ras codon 12 mutations were similarly detected in six of 13 endometrial carcinomas (one GAT and GCT, one GTT and GCT, two GAT, two GTT) and two of 13 ovarian tumors (GAT and GCT, GAT), both mucinous adenocarcinomas. Point mutation of K-ras in codon 12 is thus comparably frequent in uterine endometrial carcinomas and in colorectal carcinomas and may have similar significance as an event that contributes to progression of these tumors. Cervical carcinomas and ovarian tumors in general, with the possible exception of mucinous adenocarcinoma of the ovary, do not appear to have this characteristic.     

Modulation of tumor induction and progression of oncogenic K-ras-positive tumors in the presence of TGF- b1 haploinsufficiency

Oncogenic K-ras is one of the most common genetic alterations in human lung adenocarcinomas. In addition, inactivation of clusters of tumor suppressor genes is required to bring about classical characteristics of cancer including angiogenesis as a prelude to invasion and metastasis. Transforming growth factor-beta (TGF-beta) 1 is a tumor suppressor gene that is implicated in lung cancer progression. Although in vitro studies have shown that TGF-beta1 and Ras pathways cooperate during tumorigenesis, the biology of interaction of TGF-beta1 and Ras has not been studied in in vivo tumorigenesis. We hypothesized that inactivation of TGF-beta1 in addition to oncogeneic activation of K-ras would lead to early initiation and faster progression to lung adenocarcinoma and invasion and metastasis. Heterozygous (HT) TGF-beta1 mice were mated with latent activatable (LA) mutated K-ras mice to generate TGF-beta1(+/+), K-ras LA (wild-type (WT)/LA) and TGF-beta1(+/-), K-ras LA (HT/LA) mice. Both HT/LA and WT/LA mice developed spontaneous lung tumors, but HT/LA mice progressed to adenocarcinomas significantly earlier compared with WT/LA mice. In addition, WT/LA adenocarcinomas had significantly higher angiogenic activity compared with HT/LA adenocarcinomas. Thus, while oncogenic K-ras mutation and insensitivity to the growth regulatory effects of TGF-beta1 is essential for initiation and progression of mouse lung tumors to adenocarcinoma, a full gene dosage of TGF-beta1 is required for tumor-induced angiogenesis and invasive potential. This study identifies a number of genes not previously associated with lung cancer that are involved in tumor induction and progression. In addition, we provide evidence that progression to invasive angiogenic lesions requires TGF-beta1 responsiveness in addition to Ras mutation.     

Detection of activated K-ras in non-small cell lung cancer by membrane array: a comparison with direct sequencing

The ability to detect K-ras oncogene may provide additional information for the management of patients with non-small cell lung cancer (NSCLC). In the present study, we detected the K-ras oncogene in 76 patients with NSCLC by two methods: direct sequencing of K-ras in tumor tissues and membrane array detection of the gene overexpression specific for activated K-ras in peripheral blood. The results showed that 28 (36.8%) of the 76 Taiwanese NSCLC patients had K-ras mutations, with a frequency of 36.4% (20/55) in adenocarcinomas and 38.1% (8/21) in squamous cell carcinomas. The K-ras mutations were more frequently found in smokers than in non-smokers (51.4 vs. 24.4%, P=0.015). The incidences of K-ras mutation in the subgroups of non-smokers and squamous cell carcinomas are relatively higher in Taiwan than in other countries. On the other hand, the membrane array method could positively detect circulating activated K-ras in all of the 27 NSCLC patients with K-ras mutations at codons 12, 13 and 61, and in 4 of the 48 patients with wild-type K-ras. Our results suggest that the K-ras oncogene membrane array serves as a sensitive and convenient tool for the detection of K-ras oncogene, and therefore, has a great potential for clinical applications.     

融合基因阳性肺腺癌的病理组织学特征及与砂粒体的相关性研究

背景与目的：间变性淋巴瘤激酶(anaplastic lymphoma kinase,ALK)、c-ros原癌基因1酪氨酸激酶(c-ros oncogene 1 receptor tyrosine kinase,ROS1)和RET融合基因被陆续证实为肺腺癌的驱动基因突变,并可在靶向治疗中获益。该研究旨在阐述融合基因阳性肺腺癌病理组织学特征,并探讨砂粒体与融合基因阳性肺腺癌的相关性。方法：收集复旦大学附属肿瘤医院原发肺腺癌患者手术切除新鲜标本和石蜡固定标本,检测肺腺癌标本中表皮生长因子受体(epidermal growth factor receptor,EGFR)、鼠类肉瘤病毒癌基因(Kirsten rat sarcoma viral oncogene,K-ras)、ALK、RET和ROS1基因突变状态。选取融合基因阳性肺腺癌病例44例(9例ROS1阳性,20例K-ras阳性,15例RET阳性)和融合基因阴性肺腺癌111例(20例EGFR突变,20例K-ras突变,71例未检测出基因突变)用于本项研究。根据2015年世界卫生组织(World Health Organization,WHO)肺腺癌新分类评估融合基因组与无融合基因组的病理组织学形态特征,并观察肺腺癌组织中砂粒体的数量及其分布的特征,并探讨砂粒体与融合基因阳性肺腺癌的相关性。结果：融合基因组中主要组织学亚型为腺泡状亚型(19/44,43.2%)和实体亚型(13/44,29.5%),无融合基因组主要组织学亚型为腺泡状亚型(50/111,45.0%)。实体亚型更多见于融合基因组,但两组间主要组织学亚型差异无统计学意义(P=0.060)。含印戒细胞成分、微乳头结构、黏液筛状结构及细胞外黏液分泌在融合基因组中阳性率均显著高于无融合基因组(P=0.000,P=0.044,P=0.000,P=0.010)。砂粒体在融合基因组阳性率显著高于无融合基因组(P=0.000),并且砂粒体与微乳头及黏液筛状结构具有显著相关性(P=0.000)。结论：实体亚型及腺泡状亚型常见于融合基因阳性肺腺癌。砂粒体、微乳头、细胞外黏液分泌、黏液筛状结构及含印戒细胞成分等特征性组织学形态与融合基因阳性肺腺癌密切相关,并且砂粒体与微乳头结构和(或)黏液筛状结构往往同时存在。通过对肺腺癌的特征性形态学观察对肺腺癌基因检测的优先性筛选具有指导意义。     

Analysis of ras gene mutations in biliary and pancreatic tumors by polymerase chain reaction and direct sequencing

Ras gene is one of the oncogenes most commonly detected in human cancers and consists of three families (H-ras, K-ras, N-ras) that are converted to active oncogenes by point mutations occurring in codon 12, 13, or 61. The authors analyzed mutations of these codons in 12 extrahepatic bile duct carcinomas, nine gallbladder carcinomas, and 20 pancreatic tumors (18 pancreatic adenocarcinomas and two islet cell tumors) by a method to directly sequence nucleotides, using polymerase chain reaction and a direct sequencing method. Point mutations at K-ras codon 12 were found in all of 18 pancreatic adenocarcinomas and in one bile duct carcinoma, but there were no mutations in the remaining 11 bile duct carcinomas, in all of 9 gallbladder carcinomas, or in two islet cell tumors. A very high incidence of ras gene mutations may be used clinically for the diagnosis of debatable cases of pancreatic adenocarcinoma.     

Detection of k-ras mutation in normal and malignant colonic tissues by an enriched PCR method

ras oncogene mutations appear in over 50% of colon tumors in humans. Studies in animal systems have revealed that ras mutations are also present in preneoplastic lesions, suggesting the possibility of early detection of ras mutation in morphologically normal colon tissues for diagnostic purposes. An Enriched PCR, developed by us, eliminates most of the normal ras alleles prior to amplification; subsequent analysis via RFLP enables the detection of one mutant allele within 10(4) normal alleles. Using the Enriched PCR, we have determined the frequency of mutant ras alleles in normal mucosae and in adenomatous polyps of patients with or without adenocarcinoma. Of the 42 patients who had colon tumors, 15 were found to harbor K-ras oncogene mutation (35%). In two of the 14 cases with mutant K-ras in the tumor tissue we were able to identify mutations in tissues that had been obtained from a site at considerable distance from the tumor (13%); Analysis of 7 adenomas identified one as a carrier of the mutant ras allele (14%). Of 11 normal colonic mucosa obtained from patients without neoplasia, one specimen contained K-ras mutation. Thus, mutated alleles of K-ras may be present, at low frequency, throughout the 'normal appearing' tissue. Cells of normal appearance that harbor such mutation, have the potential to undergo further changes and to develop into the transformed phenotype. Overall, our findings suggest that mutant ras alleles can be detected in preneoplastic mucosa that is morphologically normal, and in adenomas, suggesting the occurrence of an initiation event, and possibly enabling the identification of patients who may be at high risk for developing malignant tumors.     

Inhibition of mammalian target of rapamycin reverses alveolar epithelial neoplasia induced by oncogenic K-ras

The serine/threonine kinase AKT and its downstream mediator mammalian target of rapamycin (mTOR) are activated in lung adenocarcinoma, and clinical trials are under way to test whether inhibition of mTOR is useful in treating lung cancer. Here, we report that mTOR inhibition blocked malignant progression in K-ras(LA1) mice, which undergo somatic activation of the K-ras oncogene and display morphologic changes in alveolar epithelial cells that recapitulate those of precursors of human lung adenocarcinoma. Levels of phospho-S6(Ser236/235), a downstream mediator of mTOR, increased with malignant progression (normal alveolar epithelial cells to adenocarcinoma) in K-ras(LA1) mice and in patients with lung adenocarcinoma. Atypical alveolar hyperplasia, an early neoplastic change, was prominently associated with macrophages and expressed high levels of phospho-S6(Ser236/235). mTOR inhibition in K-ras(LA1) mice by treatment with the rapamycin analogue CCI-779 reduced the size and number of early epithelial neoplastic lesions (atypical alveolar hyperplasia and adenomas) and induced apoptosis of intraepithelial macrophages. LKR-13, a lung adenocarcinoma cell line derived from K-ras(LA1) mice, was resistant to treatment with CCI-779 in vitro. However, LKR-13 cells grown as syngeneic tumors recruited macrophages, and those tumors regressed in response to treatment with CCI-779. Lastly, conditioned medium from primary cultures of alveolar macrophages stimulated the proliferation of LKR-13 cells. These findings provide evidence that the expansion of lung adenocarcinoma precursors induced by oncogenic K-ras requires mTOR-dependent signaling and that host factors derived from macrophages play a critical role in adenocarcinoma progression.     

Similar incidence of K-ras mutations in lung carcinomas of FVB/N mice and FVB/N mice carrying a mutant p53 transgene

Mutated p53 genes are capable of complementing activated ras genes in the transformation of primary rat embryo fibroblasts in vitro. Mutations in both genes have also been found in several human cancers, including lung carcinomas. We generated transgenic mice containing a p53 construct with a missense mutation in exon 5 (ala135val) to study the role of p53 mutations in lung tumorigenesis, and to facilitate identification of other genetic events that might complement p53 mutations in mouse lung carcinogenesis. The p53 transgenic lines exhibited a higher frequency of lethal lung tumors than the parental FVB/N strain. We examined the spontaneously-arising lung carcinomas from mice expressing the mutated p53 transgene for K-ras mutations using single-stranded conformation polymorphism (SSCP) and/or direct sequencing approaches. Fifteen of 29 (52%) carcinomas contained mutations in the K-ras oncogene. Six of 15 of the K-ras mutations were in codon 61 and 9/15 were in codon 12. Subsequent analysis of spontaneous lung carcinomas from mice of the FVB/N parental strain showed that 9/12 (75%) carcinomas examined contained K-ras mutations. Two of these were in codon 12, one in codon 13, and 6 were in codon 61. These results demonstrate that the frequency of ras mutations does not differ between the p53 FVB/N transgenic mice and their parental FVB/N strain but suggest that a high frequency of mutations K-ras can be correlated with lung tumorigenesis in both groups of mice.      

Activating mutation of the Ha-ras gene in chemically induced tumors of the hamster cheek pouch.

The presence of an activating mutation in the Ha-ras gene in hamster cheek pouch tumors induced by 7,12-dimethylbenz[a]anthracene (DMBA) complete carcinogenesis was investigated. The normal sequence of a fragment of genomic DNA encompassing codon 61 of the Ha-ras gene was amplified by the polymerase chain reaction using primers designed for a highly conserved region of the mouse Ha-ras-1 gene. The sequence of the amplified fragment was determined by a direct sequencing technique and exhibited 83.3% and 87.5% homology with the corresponding human and mouse sequences, respectively. At the amino acid level, the sequence was identical among the three species. Paraffin sections of 11 squamous cell carcinomas of the cheek pouch were used to detect mutated Ha-ras alleles. DNA sequencing of the tumors showed that six of 11 tumors presented an A----T transversion in the second position of codon 61, resulting in an amino acid change from glycine to leucine. As has been demonstrated in other systems, we have shown a specific mutation of the Ha-ras gene in chemically induced tumors of the hamster cheek pouch, further supporting the role of this oncogene in chemical carcinogenesis.     

Detection of K-ras mutations in pancreatic and hepatic neoplasms by non-isotopic mismatched polymerase chain reaction.

Mutations within codon 12 leading to activation of Kirsten-ras (K-ras) genes occur in a wide variety of human tumors, but have been reported most frequently in pancreatic carcinomas. We studied twenty-four paraffin-embedded pancreatic and hepatic tumors and two colon carcinoma cell lines with a rapid and simple approach that exploits allele-specific amplification of genomic DNA in a polymerase chain reaction (PCR). We extend the utility of this technique, which is dependent on an exact match at the 3' nucleotide between synthetic oligonucleotides and template DNA, to analyse paraffin-embedded tumor samples for the presence of point mutations at the first and second base of codon 12 of the K-ras gene. The PCR mismatch amplification technique demonstrated a 66% incidence of K-ras mutations at codon 12 in the group of pancreatic neoplasms as a whole. The percentage of mutations varied only slightly in the pancreatic cancer subcategories: 75% in ampullary, 66% in bile duct and 57% in the ductal adenocarcinomas. One islet cell carcinoma and normal tissues adjacent to the tumors revealed wild-type alleles only. One hepatoblastoma and one of six hepatocellular carcinomas also had codon 12 mutations. The PCR mismatch is a sensitive and rapid method that may be useful in screening neoplasms for K-ras point mutation and can be applied to archival material. This application allows a retrospective analyses of a wide range of pathological specimens to determine the role of K-ras mutations in human tumorigenesis.     

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.     

Expression of the neu gene-encoded protein (P185neu) in human non-small cell carcinomas of the lung

The neu protooncogene is a recently described transforming gene originally isolated from ethylnitrosourea-induced rat neuroblastomas. We have examined the expression of the neu gene in human non-small cell lung carcinomas using immunoprecipitation and immunohistochemistry. The neu protein product (p185neu) was present in eight of 22 non-small cell carcinoma cell lines derived from human lung tumors. Expression of p185neu was found in all histological subtypes of non-small cell carcinomas including large cell carcinomas, squamous cell carcinomas, and adenocarcinomas. Extension of these data to biopsy specimens of human lung tumors demonstrated that normal ciliated bronchial epithelium of the peripheral airways expressed p185neu at low levels. Neoplastic cells in four of 12 adenocarcinomas and three of five squamous cell carcinomas also expressed p185neu at levels higher than the normal ciliated bronchial epithelium. Together these studies indicate that p185neu expression is a common feature of human lung tumors.     

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.