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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cellular oncogenes appear to be involved in the control of normal cell growth and differentiation. The abnormal activation of these genes in naturally occurring and experimentally induced cancers may have an important role in the expression of the malignant phenotype in cancer cells. Mechanisms for the activation of these genes include chromosomal translocation, point mutation, and DNA amplification. The amplification of specific oncogenes correlates with clinical prognosis in several human malignancies, including breast cancer and neuroblastoma. We examined 21 fresh-frozen human squamous cell carcinomas of the aerodigestive tract for amplification of 10 known cellular oncogenes (c-myc, N-myc, L-myc, N-ras, H-ras, K-ras, erb-B, erb-B2, raf, and int-2), using Southern blotting techniques. Eleven of 21 tumors demonstrated a two-fold to 11-fold amplification of the int-2 oncogene, one member of a family of genes related to basic fibroblast growth factor. Amplification of c-myc, a gene that codes for a DNA-binding protein involved in the regulation of cell growth, was seen in two tumors. None of the other eight genes studied were amplified in any of the tumor specimens.
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PMID:Oncogene amplification in squamous cell carcinoma of the head and neck. 224 38

By using anti-NHK-ras and K-ras monoclonal antibodies, paraffin-embedded tissue specimens of 70 cases of colorectal cancers were immunohistologically examined. Correlation between incidence of expression of these oncogenes and either of postoperative survival rate and stage of colorectal cancer were calculated. The positive rate of anti-NHK-ras and K-ras staining were correlated with maximum diameters of tumor, staging, degree of Dukes classification and depth of invasion. Positive and negative rates of between NHK-ras and K-ras staining were well coincident. The cumulative postoperative survival rate of negative cases for anti-K-ras staining showed a significantly higher survival rate than that of the positive cases.
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PMID:[Immunohistological study for the ras oncogene products in colorectal cancer]. 225 Mar 77

Recent studies of colon adenocarcinomas in humans and experimentally induced colonic tumors in rodents have demonstrated selective elevations in the level of N1-acetylspermidine in these malignant tissues. The exact relationship of these alterations in acetylated polyamine levels to the malignant transformation process, however, remains unclear. In order to clarify this issue, rats were given s.c. injections of 1,2-dimethylhydrazine (DMH; 20 mg/kg body wt/week) or diluent for up to 26 weeks. After 10 weeks of carcinogen treatment, one-half of the animals in each group were also concomitantly given i.p. injections of MDL 72527 (20 mg/kg body wt/week), a specific inhibitor of polyamine oxidase, until they were killed. Animals were killed after 15 weeks of DMH treatment and polyamine levels as well as the activities of polyamine oxidase, ornithine decarboxylase and spermidine-N1-acetyltransferase were measured and compared in rat proximal and distal colonic mucosa of each group. Polyamine levels were also assessed in each of these groups after 26 weeks of treatment with this carcinogen +/- MDL 72527. In addition, in view of recent studies that have indicated that polyamines may influence certain oncogenes in human colonic carcinoma cells, tumors from DMH +/- MDL 72527 were analyzed for K-ras mutations. The results of these experiments demonstrated for the first time that: (i) MDL 72527 was a specific inhibitor of polyamine oxidase in normal and malignant colonic tissue; (ii) concomitant administration of this agent with DMH enhanced the elevation of colonic N1-acetylspermidine and significantly reduced the mean colonic tumor burden, as assessed by total tumor area per rat, produced by this carcinogen alone; (iii) analysis of K-ras mutations revealed a similar incidence (62-69%) in adenocarcinomas for both groups (+/- MDL 72527); (iv) however, analysis of the K-ras-mutated and non-mutated tumors revealed that in both carcinogen-treated groups (+/- MDL 72527), tumors with such mutations were smaller than their counterparts without such genetic alterations. Moreover, MDL 72527 reduced the average size of tumors, with and without such mutations, to a similar extent.
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PMID:Effect of polyamine oxidase inhibition on the colonic malignant transformation process induced by 1,2-dimethylhydrazine. 226 65

Bladder tumors were induced in male F344/NCr rats by administration of N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) at 500 p.p.m. in their drinking water for 12 weeks. Twenty-one bladder tumors that developed between 25 and 50 weeks after BBN administration was begun were evaluated for immunoreactivity with polyclonal or monoclonal antibodies raised against ras p21, for amplification of ras genes by Southern blotting, and for activating point mutations in ras genes by selective oligonucleotide hybridization of products from polymerase chain reaction (PCR). Increased expression of ras p21 was detected by avidin-biotin immunohistochemistry in 18/21 (85%) of the neoplastic bladder lesions. By Southern analysis, there was no significant amplification of H-ras, K-ras or N-ras in any of the tumors except one that showed a 5-fold amplification of K-ras. Point mutations in ras genes were detected by selective oligonucleotide hybridization of the products of PCR. Of the 21 bladder tumors, three tumors were shown to have mutations in codon 12 (GGA----GAA), six tumors in codon 61 (two CAA----CTA, four CAA----CGA), and one in both codon 12 (GGA----GAA) and codon 61 (CAA----CGA), all in H-ras. Thus 10 of 21 tumors has ras gene mutations in a portion of the tumor cells. The variable pattern of point mutation in H-ras suggests that these mutations may not all be a direct consequence of interaction of BBN metabolites with H-ras. Enhanced expression of ras p21 was always focal and was not necessarily associated with transforming ras mutations. It is therefore suggested that tumorigenesis in BBN-initiated bladder cells might involve H-ras activation as part of a multistep pathway; however, H-ras involvement is not obligatory for tumor development.
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PMID:H-ras activation and ras p21 expression in bladder tumors induced in F344/NCr rats by N-butyl-N-(4-hydroxybutyl)nitrosamine. 226 74

Identifying the nature of the genetic mutations in thyroid neoplasms and their prevalence in the various tumor phenotypes is critical to understanding their pathogenesis. Mutational activation of ras oncogenes in human tumors occurs predominantly through point mutations in two functional regions of the molecules, codons 12, 13 (GTP-binding domain) or codon 61 (GTPase domain). We examined the prevalence of point mutations in codons 12, 13, and 61 of the oncogenes K-ras, N-ras, and H-ras in benign and malignant human thyroid tumors by hybridization of PCR-amplified tumor DNA with synthetic oligodeoxynucleotide probes. None of the eight normal thyroid tissues harbored point mutations. Four of nineteen nodules from multinodular goiters (21%), 6/24 microfollicular adenomas (25%), 3/14 papillary carcinomas (21%), and 0/3 follicular carcinomas contained ras point mutations. The predominant mutation was a valine for glycine substitution in codon 12 of H-ras. None of the multinodular goiter tumors known to be polyclonal (and thus due to hyperplasia) had point mutations, whereas one of the two monoclonal adenomas arising in nodular glands contained in H-ras codon 12 valine substitution, which was confirmed by sequencing the tumor DNA. These data show that ras activation is about equally prevalent in benign and malignant thyroid neoplasms, and thus may be an early event in the tumorigenic process.
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PMID:Point mutations of ras oncogenes are an early event in thyroid tumorigenesis. 228 98

Despite a considerable amount of information concerning chromosomal and molecular abnormalities found in gliomas in adults, relatively little is known regarding these abnormalities in pediatric brain tumors. We have analyzed DNA from 37 primary brain tumors and 4 tumor-derived cell lines for oncogene amplification. Probes utilized represent 11 known oncogenes (erbB1, gli, neu, myc, L-myc, N-myc, H-ras, K-ras, N-ras, sis, and src). Of 20 primary medulloblastomas studied, only one tumor was found to have erbB1 amplification. In contrast, of the 4 medulloblastoma cell lines studied, 1 had c-myc amplification, 1 had erbB1 amplification, and 1 had amplification of N-myc. Twelve glial brain tumors were analyzed, and only 1 case with amplification of the erbB1 oncogene was found. Other tumors studied include 1 meningioma, 2 ependymomas, 1 anaplastic ependymoma, and 1 cerebral primitive neuroectodermal tumor, none of which had oncogene amplification. These results suggest that oncogene amplification is relatively uncommon in primary medulloblastomas, but the frequency and diversity of oncogene amplification is greater in tumors that can be established as cell lines. The lower frequency of erbB1 amplification in glial brain tumors in children compared to adults is consistent with the generally lower grade of glial tumor histology seen in pediatric patients. However, the case with amplification of the erbB1 oncogene represented 1 of 2 cases of glioblastoma multiforme we studied, which suggests that pediatric glioblastoma multiforme may have a similar frequency of erbB1 oncogene amplification to glioblastomas seen in adults. Our results suggest that oncogene amplification is a relatively uncommon mechanism of oncogene activation in pediatric brain tumors, and they provide molecular evidence for heterogeneity in tumors classified as medulloblastomas.
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PMID:Oncogene amplification in pediatric brain tumors. 233 1

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.
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PMID:ras oncogenes in human cancer: a review. 254 13

A survey of a large series of radiation- or chemically induced thymic lymphomas in (AKR X RF)F1, RF/J, 129/J, and C57BL/6J mouse strains for activated ras oncogenes showed that of the tumors containing transforming activity, in more than 75% of the cases this activity segregated with either K-ras or the N-ras gene. H-ras activity was never detected. The genetic background of the host influenced susceptibility to tumor induction and oncogene activation. The K-ras gene was preferentially activated over the N-ras gene (approximately 2:1) whether the inducing agent was radiation or the chemical N-nitrosomethylurea. The activating mutation for the K-ras gene was consistently identified as a GGT to GAT transition in codon 12. In contrast, several different mutations of the N-ras gene were identified and localized to codons 12, 13, or 61. Assessment of the allelic composition of the ras locus shows that some proportion of the tumors lost the normal ras allele.
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PMID:Radiation and chemical activation of ras oncogenes in different mouse strains. 266 82

Lung and liver tumors were induced in female A/J mice after treatment for 7 weeks (3 times/week, i.p.) with either 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) (50 mg/kg) or nitrosodimethylamine (NDMA) (3 mg/kg). Both compounds can be activated via alpha-hydroxylation to methylating agents, while NNK may also undergo hydroxylation at the N-methyl carbon to form a pyridyloxobutylated adduct. The purpose of these studies was to identify and characterize the activated oncogenes present in tumors induced by NDMA and NNK. Following transfection of high molecular weight DNA onto NIH/3T3 mouse fibroblasts, transforming genes were detected in 90% of both NNK- (10 of 11) and NDMA- (9 of 10) induced lung tumors. In contrast, transformation of NIH/3T3 fibroblasts was observed only in 40% (2 of 5) and 13% (1 of 8) of the liver tumors from NNK- and NDMA-treated mice, respectively. Southern blot analysis indicated that the transforming gene present in all lung tumors was an activated K-ras oncogene. Both rearranged bands and amplified signals were detected in the transfectants. The one transformant from the NDMA-induced liver tumor contained an activated K-ras gene. In contrast, the two liver transformants from NNK-induced tumors did not contain an activated ras or raf gene. Hybridization with oligonucleotide probes that were centered around either codon 12 or 61 of the K-ras gene were utilized to localize the mutations. Activation of this gene appeared to occur largely via a mutation in codon 12 (15 of 20 transformants) and was observed with a similar frequency in pulmonary tumors induced by either compound. The remaining mutations were found in codon 61. The specific mutation within these two codons was determined by amplifying the exon containing the base change, followed by direct sequencing. With one exception the mutation observed in codon 12 was a GC to AT transition (GGT to GAT). One transformant contained a GC to TA transversion. The activating mutation detected in codon 61 was always an AT to GC transition of the middle A (CAA to CGA). The GC to AT mutation observed in codon 12 is consistent with the formation of the O6-methylguanine adduct. Similar concentrations (23 to 32 pmol/mumol deoxyguanosine) of this promutagenic adduct were detected in lungs during treatment with either NNK or NDMA.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Relationship between the formation of promutagenic adducts and the activation of the K-ras protooncogene in lung tumors from A/J mice treated with nitrosamines. 267 Feb 1

Ricin A chain immunotoxin (IT) 45-2D9-RTA mediates regression of spontaneous pulmonary metastases and lung colonies from K-ras transformed rat fibroblasts (TRF cells). However, residual metastases are frequently noted after IT therapy, and therefore, possible mechanisms mediating tumor cell escape were investigated. Individual lung colonies were dissected from lungs of BALB/c mice, and single-cell suspensions of fresh cells from short-term cultures (eight passages) were tested. Immunoperoxidase staining with 45-2D9 monoclonal antibody showed that stable loss of surface antigen by cells cultured from IT-treated mice did not occur after four injections of specific IT. Sensitivity to specific IT in vitro was equal for metastatic tumor cells from mice treated with either two or four doses of specific IT compared to cells from nonspecific IT-treated mice and to parental cells. Clones derived from metastases of IT-treated mice were not resistant to IT. Clones derived from metastases of specific IT-treated mice internalized bound antibody or IT at the same rate as untreated cells. Freshly disaggregated cells from specific IT-treated mice were as sensitive to specific IT as were cells from nonspecific IT-treated or untreated mice. Specific IT successfully mediated reduction of lung colonies derived from fresh suspensions of lung colony TRF cells from IT-treated mice. This reduction was equivalent to that seen for cells not previously exposed to specific IT. Immunoperoxidase stains of lung sections with 45-2D9 showed that colonies consisting entirely of unstained TRF cells were present in both specific IT and phosphate buffered saline-treated mice. There was a trend toward a higher percentage of antigen-negative colonies in mice treated with IT, although 9 days following specific IT therapy, greater than 80% of lung colonies expressed gp74 antigen. When TRF cells were grown on agar plugs, which promoted three-dimensional growth, groups of cells showing absence of immunoperoxidase staining with antibody to gp74 were identified during 2 weeks of growth. Thus, stability of antigen-negative variants is favored by three-dimensional growth conditions and the selective pressure of IT administration. Our results also suggest that impaired trafficking of IT to antigen-positive cells may also contribute to escape from IT therapy.
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PMID:Analysis of gp74 expression by transformed rat fibroblasts from experimental pulmonary metastases following specific ricin A-chain immunotoxin therapy. 267 48


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