采用PCR—RFLP技术分析石蜡包埋胃癌组织ras和p53基因点突变

采用多聚酶链延伸反应一限制性片段长度多态性分析（ＰＣＲ—ＲＦＬＰ）法对福尔马林固定、石蜡包埋胃癌组织ｒａｓ和ｐ５３基因点突变进行分析，结果表明，Ｃ—Ｈａ—ｒａｓ第１２位密码子突变率为１３．６％（１２／８８），第６１位密码子为３．８％（３／８０）；Ｃ—Ｋｉ—ｒａｓ第１２位密码子点突变率为７．２％（５／６９），第１３位密码子未发现有点突变者；Ｎ—ｒａｓ第１２位密码子点突变率为１．４％（１／６８）。ｐ５３基因第２４８位密码子点突变率为７．４％（５／６８），第２４９位密码子未见有点突变者。以上提示采用ＰＣＲ—ＲＦＬＰ技术可对多数从石蜡包埋胃癌组织提取的ＤＮＡ进行ｒａｓ和ｐ５３基因点突变分析。     

ras mutations in endocrine tumors: mutation detection by polymerase chain reaction-single strand conformation polymorphism.

To elucidate the molecular basis for endocrine tumorigenesis, ras mutations in human endocrine tumors were analyzed using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. Mutations of the H-, K-, N-ras genes were examined in genomic DNAs from 169 successfully amplified primary endocrine tumors out of 189 samples. Four out of 24 thyroid follicular adenomas analyzed contained mutated N-ras codon 61, and one contained the mutated H-ras codon 61. One of the 19 pheochromocytomas revealed mutation of the H-ras codon 13. No mutations of the ras gene were detected in pituitary adenomas, parathyroid tumors, thyroid cancers, endocrine pancreatic tumors, and adrenocortical tumors. Based on these findings we conclude that activation of the ras gene may play a role in the tumorigenesis of a limited number of thyroid follicular adenomas and pheochromocytomas, and that mutation of the ras gene is not frequent in other human endocrine tumors.     

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.      

ras Mutations in Endocrine Tumors: Mutation Detection by Polymerase Chain Reaction-Single Strand Conformation Polymorphism

To elucidate the molecular basis for endocrine tumorigenesis, ras mutations in human endocrine tumors were analyzed using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. Mutations of the H-, K-, N- ras genes were examined in genomic DNAs from 169 successfully amplified primary endocrine tumors out of 189 samples. Four out of 24 thyroid follicular adenomas analyzed contained mutated N- ras codon 61, and one contained the mutated H- ras codon 61. One of the 19 pheochromocytomas revealed mutation of the H- ras codon 13. No mutations of the ras gene were detected in pituitary adenomas, parathyroid tumors, thyroid cancers, endocrine pancreatic tumors, and adrenocortical tumors. Based on these findings we conclude that activation of the ras gene may play a role in the tumorigenesis of a limited number of thyroid follicular adenomas and pheochromocytomas, and that mutation of the ras gene is not frequent in other human endocrine tumors.     

Site-specific Mutation of the Human c-Ha-ras Transgene Induced by Dimethylbenzanthracene Causes Tissue-specific Tumors in Mice

Forestoraach squamous cell carcinomas, lung adenocarcinomas and spleen angiosarcomas were induced by dimethylbenzanthracene (DMBA) in the rasH2 transgenic mouse line carrying human c-Ha-ras genes with their own promoter, encoding the prototype p21 gene product. Fifteen out of 21 mice (71%) developed forestomach squamous cell carcinomas, while 15 out of 21 (71%) had lung adenocarcinomas and 3 out of 21 (14%) showed spleen angiosarcomas within 8 weeks after a single administration of 50 mg/kg DMBA intraperitoneally. Somatic mutation at the 61st codon of the transgenes, from CAG(Gln) to CTG(Len), was detected in all these newly developed tumors. However, non-transgenic littermates demonstrated no tumors at all. These findings provide strong evidence that the somatic mutational activation of human c-Ha- ras genes is a critical event in tumorigenesis and a close relationship is therefore strongly suggested between the tissue-specific development of tumors and the somatic mutation of human c-Ha-ras genes in these rasH2 transgenic mice.     

Aristolochic acid activates ras genes in rat tumors at deoxyadenosine residues

Aristolochic acid I (AAI), a nitrophenanthrene derivative, is the major component of the carcinogenic plant extract aristolochic acid, which has been used as a medicine since antiquity. Long term oral administration of AAI to male Wistar rats induces multiple tumors, mainly in the forestomach, ear duct, and small intestine. The presence of activated transforming genes was investigated in various tumors of 18 AAI treated rats, namely in 14 squamous cell carcinomas of the forestomach, 7 squamous cell carcinomas of the ear duct, 8 tumors of the small intestine, 3 tumors of the pancreas, 1 adenocarcinoma of the kidney, 1 lymphoma, and 2 metastases in the lung and the pancreas. By utilizing the tumorigenicity assay and Southern blot analysis, we have detected an activated c-Ha-ras gene in the DNAs of 5 of 5 squamous cell carcinomas of the forestomach. Direct sequencing of amplified material revealed an AT----TA transversion mutation at the second position of codon 61 of the c-Ha-ras gene (CAA to CTA) in all transfectants as well as in the 5 original rat tumors. Enzymatic amplification of ras sequences followed by selective oligonucleotide hybridization detected identical mutations in 93% (13 of 14) of forestomach tumors, in 100% (7 of 7) of ear duct tumors, and in the lung metastasis. Among those tumors tested, we had 4 cases in which the forestomach tumors and the ear duct tumors originated from the same rat, showing the same mutation in both tissues. Moreover, similar mutations were demonstrated at c-Ki-ras codon 61 in 1 of 7 ear duct tumors (CAA to CAT) and in 1 of 8 tumors of the small intestine (CAA to CTA) as well as at c-N-ras 61 (CAA to CTA) in a pancreatic metastasis. Additional transfection experiments of some tumors scoring negative for ras gene mutations in dot blot analyses revealed a CAA to CTA transversion at codon 61 of the c-Ha-ras gene in 1 forestomach tumor as well as at codon 61 of the c-N-ras in 1 hyperplasia of the pancreas and in 1 lymphoma. The apparent selectivity for mutations at adenine residues in AAI induced tumors is consistent with the identification of an N6-deoxyadenosine-AAI adduct formed by reaction of AAI with DNA in vitro, suggesting that carcinogen-deoxyadenosine adducts are the critical lesions in the tumor initiation by aristolochic acid.     

Glycine to aspartic acid mutations at codon 13 of the c-Ki-ras gene in human gastrointestinal cancers

Point mutations of c-ras genes were analyzed in human gastrointestinal cancers. DNA obtained from the tissues was amplified by polymerase chain reaction and then analyzed by dot blot hybridization assay with oligonucleotide probes to detect mutations at codons 12, 13, and 61 of c-Ki-ras, c-Ha-ras, and c-N-ras. In two of 25 cases of stomach cancer point mutations at codon 13 of c-Ki-ras were found. In colorectal cancer, eight of 30 cases showed mutations: four cases of codon 12 and one case at codon 13 of c-Ki-ras and two cases at codon 61 and one case at codon 13 of c-N-ras. These results may indicate involvement of a wide variety of c-ras gene point mutations, in addition to those at codon 12 of c-Ki-ras, in oncogenesis of human gastrointestinal cancers. In all three mutations of c-Ki-ras at codon 13 which had been seldom found in human cancers, glycine to aspartic acid mutations due to identical G to A transition at the second nucleotide were observed.     

Activation of c-K-ras is frequent in pancreatic carcinomas of Syrian hamsters, but is absent in pancreatic tumors of rats.

We have investigated the presence of mutations in ras genes at codons 12, 13 and 61 in chemically induced pancreatic tumors of rats and Syrian hamsters. Mutations were detected by means of allele-specific oligonucleotide hybridization to ras sequences amplified in vitro by the polymerase chain reaction. No mutations were observed in the c-K-ras gene or the c-H-ras gene of nine azaserine-induced adenomas and 15 carcinomas of the rat pancreas. This indicates that activated ras genes are not commonly involved in rat pancreatic cancer evolving from acinar cells. However, in 19 out of 20 ductular adenocarcinomas of hamster pancreas (95%), either codon 12 or 13 of the c-K-ras gene was mutated. This indicates that the activation of c-K-ras is a frequent event in the multistep process of pancreatic carcinogenesis induced by the alkylating carcinogen N-nitrosobis(2-oxopropyl)amine (BOP). The mutations of both codons were G----A transitions of the second base which is consistent with the type of mutation to be expected from DNA alkylation. Activation of the c-K-ras gene, therefore, may not only be a frequent but also an early event in hamster pancreas carcinogenesis. The frequent activation of the c-K-ras gene in both human and hamster pancreatic cancer emphasizes the relevance of BOP-induced pancreatic adenocarcinomas in Syrian hamsters as an experimental model system for studying human pancreatic cancer.     

Analysis of ras gene mutations in rainbow trout liver tumors initiated by aflatoxin B1.

The suspect human hepatocarcinogen aflatoxin B1 (AFB1) is a well-known potent initiator of hepatic tumors in rainbow trout (Oncorhynchus mykiss). Both hepatocellular carcinomas and mixed hepatocellular/cholangiocellular carcinomas are induced by AFB1 in trout, with the mixed form predominating. We previously isolated two c-ras genes from trout liver cDNA, and in the present study we analyzed DNA from 14 AFB1-induced trout liver tumors for point mutations in exon 1 of both genes. Using the polymerase chain reaction (PCR) and oligonucleotide hybridization methods, a high proportion (10/14) of the AFB1-initiated tumor DNAs showed evidence of activating point mutations in the trout c-Ki-ras gene. Of the 10 mutant ras genotypes, seven were codon 12 GGA----GTA transversions, two were codon 13 GGT----GTT transversions, and one was codon 12 GGA----AGA transition. Nucleotide sequence analysis of cloned PCR products from four of these tumor DNAs provided definitive evidence for two codon 12 GGA----GTA mutations, one codon 12 GGA----AGA mutation, and one codon 13 GGT----GTT mutation, in complete agreement with the oligonucleotide hybridization results. No mutations were detected in exon 1 of a second trout ras gene also expressed in liver, nor in DNA from control livers. This is the first report of experimentally induced ras gene point mutations in a lower vertebrate fish model. The results indicate that the hepatocarcinogen AFB1 induces c-Ki-ras gene mutations in trout similar to those in rat liver tumors.     

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.     

ras oncogenes in human cancer: a review

Mutations in codon 12, 13, or 61 of one of the three ras genes, H-ras, K-ras, and N-ras, convert these genes into active oncogenes. Rapid assays for the detection of these point mutations have been developed recently and used to investigate the role mutated ras genes play in the pathogenesis of human tumors. It appeared that ras gene mutations can be found in a variety of tumor types, although the incidence varies greatly. The highest incidences are found in adenocarcinomas of the pancreas (90%), the colon (50%), and the lung (30%); in thyroid tumors (50%); and in myeloid leukemia (30%). For some tumor types a relationship may exist between the presence of a ras mutation and clinical or histopathological features of the tumor. There is some evidence that environmental agents may be involved in the induction of the mutations.     

Topographic analysis of K- ras mutations in histologically normal lung tissues and tumours of lung cancer patients.

Mutations in the K- ras gene are very common in lung tumours and are implicated in the development of lung cancer, but the timing of their occurrence remains poorly understood. We investigated K- ras mutations in cell samples microdissected by laser capture microscopy at multiple sites from lung tissue sections representing tumour tissue and matched histologically normal tissue obtained from 48 lung cancer patients. K- ras mutations were detected in cell samples from 10 of 38 (26.3%) lung adenocarcinomas and in none of the histologically normal or tumour cell samples taken from 10 lung squamous cell carcinomas. Of the K- ras mutation-positive adenocarcinomas, in 4 cases a mutation was found in only the tumour tissue, in 1 case a mutation was found only in the histologically normal tissue, and in 5 cases mutations were found in both the tumour tissue and histologically normal tissue. Among these 5 cases, 2 had identical mutations in both the tumour tissue and histologically normal tissue, 2 had 1 mutation in the tumour tissue and 2 mutations in the histologically normal tissue, 1 of which was identical to the mutation found in the tumour, and 1 case had 2 codon 12 mutations in tumour tissue and 2 mutations, in codons 9 and 11, in histologically normal tissue. These results showed that K- ras mutations are frequent in histologically normal cells taken from outside lung adenocarcinomas and suggest that some of these mutations may represent early events which could pave the way of lung carcinogenesis.     

Detection of activating mutations in the ras family genes in cytological specimens from lung-tumors

Mutations in the ras family genes (K-ras mainly) represent a common event in lung tumorigenesis which is frequently associated with poor clinical outcome. In order to investigate whether K-ras mutations are detectable in cytological material obtained from patients with lung cancer, 37 cytological specimens (16 fine needle aspiration and 21 bronchoscopy) were assessed for codon 12 point mutations in the H-, K- and N-ras genes by combined polymerase chain reaction-restriction fragment length polymorphism. K-ras codon 12 point mutations were found in 8 out of 37 (22%) specimens while no mutations were found in the H-ras and N-ras genes. Mutations were found in 27% (3 out of 11) of adenocarcinomas while in squamous cell carcinomas the incidence of mutations was 18% (3 out of 17). In addition, a K-ras codon 12 point mutation was found in one (12%) among 8 small cell carcinomas and in the only Hodgkin's lymphoma with metastasis in the lung. Our results are in agreement with previous results that recognise high incidence of K-ras activation in lung carcinomas, and indicate that detection of mutant ras alleles is possible in cytological material.     

ras gene mutations in non-small cell lung cancers are associated with shortened survival irrespective of treatment intent.

We analyzed 66 non-small cell lung cancer cell lines for mutations at codons 12, 13, and 61 of all three ras genes and correlated the findings with patient survival. We used designed restriction fragment-length polymorphisms to detect mutations after amplification of ras-specific sequences by the polymerase chain reaction. We found 19 mutations of ras genes (29%), and 11 of these 19 (58%) were at codon 12 of the K-ras gene. By univariate analysis, the presence of any ras mutation in cell lines from patients who received curative intent treatment was associated with a shorter survival (P2 = 0.002). For patients who received only palliative treatment, detection of K-ras mutations at codon 12 was associated with a shortened survival (P2 = 0.0103), but this analysis was not statistically significant for the group with any ras mutation (P2 = 0.093). The Cox proportional hazards model also predicted a higher risk for patients with any type of ras mutations. We conclude that ras mutations, present in a subset of non-small cell lung cancers, are independently associated with the shortened survival of patients, irrespective of treatment intent.     

Frequency of active ras oncogenes in human bladder cancers associated with schistosomiasis

The frequency of active ras oncogenes in human bladder cancers associated with schistosomiasis, the cause of which is suspected to be a chemical carcinogen(s) in urine, was examined. Of 9 squamous cell carcinomas of the bladder surgically obtained in Egypt, none scored as positive in the regular DNA transfection assay using NIH/3T3 cells as recipients. The restriction fragment length polymorphism assay at codon 12 of the H-ras gene confirmed the absence of an activating mutation at this site in all of them. Western blotting analysis of electrophoretic mobilities of the ras p21 proteins, a method which can detect at least some of the point mutations within codons 12 and 61 of ras genes, suggested a point mutation within codon 61 in one out of the 7 tumors analyzed. In contrast to the low frequency of detection of mutationally activated ras oncogenes, enhanced expression of the ras p21 proteins was demonstrated in 4 of them by this analysis. The carcinogenic process involved in the endemic bilharzial bladder cancers is thus not associated with detectable point mutations within ras genes at a higher frequency than those in non-bilharzial bladder cancers in Japan or the USA.     

K-ras activation in premalignant and malignant epithelial lesions of the human uterus

We previously reported (Cancer Res., 50:6139-6145, 1990) a significant frequency of activating point mutations in codon 12 of the K-ras oncogene in endometrial adenocarcinomas of the uterine corpus (series 1). To further define the role of ras activation in the development of endometrial adenocarcinoma, we surveyed cystic, adenomatous, and atypical hyperplasias of uterine endometrium and additional cases of endometrial and cervical carcinoma (series 2) for the presence of activating mutations in cellular protooncogenes of the ras family. Polymerase chain reaction was performed from deparaffinized sections of formalin-fixed paraffin-embedded tissue. We screened for point mutations in codons 12, 13, and 61 of the K-, H-, and N-ras genes by dot blot hybridization analysis with mutation-specific oligomers. Mutations in K-ras were also confirmed by direct genomic DNA sequencing. Of 19 endometrial adenocarcinomas in series 2, point mutations in ras genes were found in 7 tumors. Six contained single-base substitutions, five in codon 12 of K-ras and one in codon 12 of N-ras. The seventh tumor contained two different point mutations in codon 12 of K-ras. In one endometrial adenocarcinoma, tumor cells with point mutations in K-ras were predominantly localized to a portion that had a more aggressive histological pattern. In endometrial hyperplasia, K-ras mutations, one in codon 12 and one in codon 13, were found in 2 of 16 hyperplasias histologically classified as atypical and clinically considered premalignant. None of 6 adenomatous hyperplasias and none of 12 cystic hyperplasias, the latter of which is considered clinically benign, contained any detectable ras mutations. No mutations in H-ras were detected in either carcinomas or hyperplastic tissue.     

Structure and expression of oncogenes in surgical specimens of human breast carcinomas

We have performed an analysis of ras, c-myc, c-myb, c-erbB1 and c-erbB2 oncogenes in 100 surgical samples of human breast carcinomas. No point mutations have been detected at the 12th codon of c-Ha-ras and c-Ki-ras in 40 and 65 breast cancer DNAs, respectively. One out of 65 samples showed a 50-fold amplification of c-Ha-ras that, however, was not overexpressed. Alterations in the structure of c-myc, c-myb c-erbB1 and c-erbB2 oncogenes were sporadically observed. In 20 tumour samples, the study of expression of a series of oncogenes revealed that c-Ha-ras was the predominantly transcribed gene among the ras gene family whereas c-fos appeared the most constantly and significantly expressed nuclear oncogene.     

Analysis of K-ras gene mutations in human pancreatic cancer cell lines and in bile samples from patients with pancreatic and biliary cancers

The ras family of oncogenes are the most frequently activated group of dominant transforming genes in both human and experimental cancers. The ras family of genes encode highly similar proteins with molecular weights of 21 kDa which are thought to play a key role in signal transduction. Activation in vivo by point mutations results in the ras p21 protein being maintained in the activated form and stimulating cellular proliferation autonomously. Point mutations at codon 12 of K-ras have been observed in >75% of cases of adenocarcinomas of the exocrine pancreas. The type and frequency of K-ras gene mutations in pancreatic cancer cell lines and in bile samples from patients with cytologically-proven biliary tract malignancies and from patients with non-malignant disorders of the biliary tract were determined. Codons 12, 13 and 61 of the K-ras gene were analysed by using restriction fragment length polymorphisms created through mismatched primers during polymerase chain reaction (PCR) of genomic DNA. A mutation of codon 12 of K-ras was detected in 10 of 13 (77%) human pancreatic cancer cell lines. The amino-acid substitutions were glycine to aspartate (5 samples), arginine (2), valine (2) and cysteine (1). No mutations were found at codons 13 or 61. A mutation at codon 12 of K-ras was detected in 9 of 18 (50%) of bile samples analysed. Eleven bile samples had positive cytology for malignancy of pancreaticobiliary origin, and 4 (36%) of these had a codon 12 mutation. Mutations were detected in 5 of the 7 (71%) cytologically-negative bile samples, although malignancy was subsequently diagnosed in 2 of these patients on further histology, and was suspected in 3 other cases on clinical and radiological criteria. This method provides a rapid determination of K-ras gene mutations in bile samples for patients with pancreatic and biliary tract diseases, which may be useful when considering future therapy directed at inhibition of activated ras-induced signal transduction pathways.     

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.     

Incidence of ras oncogene activation in lung carcinomas in Hong Kong.

BACKGROUND. In Hong Kong, lung carcinomas contribute to the majority of cancer deaths among Chinese. Point mutational activation of ras oncogenes has been observed in several populations. The incidence of these mutations in Hong Kong lung carcinomas was investigated. METHODS. Lung resections obtained from 52 Chinese patients whose conditions were newly diagnosed as non-small cell lung cancer, paraffin sections from 29 Chinese patients with previously diagnosed adenocarcinoma of the lung, and paraffin sections from 49 squamous cell carcinomas were examined for the presence of point mutations in Ki-ras codon 12, N-ras codon 61, and Ha-ras codon 12 oncogenes by allele-specific hybridization after specific amplification of appropriate regions of the DNA using the polymerase chain reaction. RESULTS. Among the 130 lung carcinomas investigated, Ki-ras point mutations were detected in seven cases, of which six were adenocarcinomas and one a squamous cell carcinoma. No mutations were detected in the N-ras and Ha-ras codons. CONCLUSIONS. The incidence of Ki-ras codon 12 point mutational activation in Chinese patients with adenocarcinomas was 6 of 63 (9.5%). The incidence of Ki-ras 12 point mutational activation among men with lung adenocarcinomas in Hong Kong (6 of 32 patients, 18.8%) is significantly different from that in women in Hong Kong (0 of 31 patients, 0%). Although ras oncogenes are implicated as having a role in the development of lung adenocarcinomas, especially among smokers, it is clear from these data that they are not associated with the unusually high incidence of lung adenocarcinomas among women in Hong Kong.