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PubMed1988

Viruses, oncogenes, and cancer.

Our current theories of virus-induced cellular transformation have changed with the emerging recognition that all normal cells contain proto-oncogenes which convert to oncogenes and induce transformation when activated and/or amplified. Cellular oncogenes have been identified by homology to the transforming genes of acute retroviruses and by the transforming activity of tumor cell DNA in transfection assays. More than two dozen cellular oncogenes identified to date constitute a heterogeneous group of genes which are remarkably conserved among highly diverse species. Expression of proto-oncogenes is linked to normal growth and development; whereas their expression as oncogenes due to gene mutation, rearrangement, amplification or other processes leading to altered or overexpression is associated with the development of tumors. Functions of oncogene proteins are being identified. These include unique protein kinase activity, growth factor/growth factor receptor properties, and the presence of DNA-binding polypeptides. It also appears that cooperation between several activated cellular oncogenes may be required in the multistep process of oncogenesis. Our recent in vitro experimental evidence supports that human cell carcinogenesis is indeed a multistep process. In addition, the involvement of the activated cellular transforming genes met and H-ras in chemically induced human cell carcinogenesis has been shown. Advancement in molecular biology of oncogenes and their products is likely to result in improvements in cancer diagnosis and cancer therapy.

Cell Transformation, Neoplastic↗
PubMedDate not supplied

The myc family of oncogenes and their presence and importance in small-cell lung carcinoma and other tumour types.

The myc family of cellular oncogenes, c-myc, N-myc, encodes three highly related, cell cycle specific, nuclear phospho-proteins. All are able to transform primary rat embryo fibroblasts when cotransfected with the c-ras oncogene. Myc family genes are differentially expressed with respect to tissue type and developmental stage and dramatic changes in their expression coincide with critical developmental transitions in many cell lineages. Their conservation as distinct genes over a large phylogenetic distance and their unique pattern of expression in developing embryos support the view that each member of the myc family may have an important and discrete biological activity. The nuclear localization and the presence of contiguous regions containing the basic region/helix-loop-helix/leucine zipper motifs suggest that myc-encoded proteins are involved in gene expression during growth and differentiation. The role of myc-oncogene amplification and/or overexpression in tumourigenesis is still not clear, but application of new biotechnological tools as transfection vectors and the antisense strategy may lead to a better understanding of the importance of the myc family of oncogenes. Transfection of cells with oncogenes in expression vectors conferring high levels of oncoprotein are used to analyze the influence of overexpression of the oncogene, while incubation with an appropriate antisense oligonucleotide leading to an inhibition of oncogene expression may give some clues to the necessity, function and importance of the oncogene. These two techniques have proven to be useful tools in the illumination of the function of these ubiquitous (proto-) oncogenes and probably will help to clarify at least a part of their role in, for instance, apoptosis, tumourigenesis and the development of resistance to antitumour drugs.

Apoptosis↗
PubMedDate not supplied

Differential implications of the oncogene-tumor suppressor gene complex in the geneses of 19 human neoplasias. Evidence in support of the steroid carcinogenesis hypothesis.

The cancer risk changes of 19 human neoplasias over time and space, as expressed in terms of the logarithm of age-adjusted incidence rate (log AAIR), were found to hold a linear correlation with each other--a finding suggesting that the distribution pattern of log AAIR data sets of 2 cancers, when plotted on a two dimension diagram, may show a good fitness to the chemical equilibrium model a product of the law of mass action. On the basis of the statistical analysis of the data, we reached the conclusion that the risk changes of a given neoplasia in space represents the function of the centripetal force of an activated oncogene and the centrifugal force of an inactivated tumor suppressor gene, both of which should cooperate with each other to create a thermodynamic equilibrium under the law of mass action. The purpose of this study was to test the contribution of the oncogene-tumor suppressor gene complex to the sex discrimination of cancer risk in 19 human neoplasias. The results obtained are as follows: a) the correlation coefficient r seq of the sequential regression analysis, as applied to 47 log AAIR data sets of one tumor pair, served as a criterion in testing the balance of power between oncogene activation and tumor suppressor gene inactivation. Sole activation of the oncogene should give an r seq value of -1.0, whereas sole inactivation of the tumor suppressor gene should give an r seq value of +1.0. b) Esophageal cancer and laryngeal cancer, two sex-discriminating tumors with distinct male predominance were each associated with differential implications of the oncogene-tumor suppressor gene complex between the male and female populations: in both tumors, the male populations were associated with a complex of activated oncogene and inactivated tumor suppressor gene, whereas the female population was associated with another complex of weakly activated (esophageal cancer) or non-activated (laryngeal cancer) oncogene and inactivated tumor suppressor gene, as assessed by the r seq criteria. c) The intersex correlation of cancer risk in both esophageal cancer and laryngeal cancer for 47 populations throughout the world, was rather weak, when compared with other members of human neoplasias. The intersex difference of r seq as expressed in terms of t value of Student's t test for each of 19 human neoplasias, was negatively correlated with the correlation coefficient r of the intersex regression analysis with the same 47 populations. It was indicated that a change in the intersex linkage of cancer risk may be related to the differential implication of the oncogene-tumor suppressor gene complex in carcinogenesis. In summary, we conclude that the hormonal milieu of the host plays a cardinal role as the modifier of the oncogene-tumor suppressor gene impact.

Esophageal Neoplasms↗
PubMed1992

Oncogenes and cell growth.

In this short overview of oncogenes and cell growth, the protein products have been divided into two classes, proto-oncogenes and oncogenes. Proto-oncogenes can be activated by point mutations and deletions. Two classes exist: the dominant, which leads to cell growth and the suppressor, which by definition suppresses growth. The mechanism of action is multiplex--duplication of hormone action, resemblance to receptors, or kinases and DNA binding proteins. It is clear that the regulation of cell growth and differentiation is very complex and that the products of proto-oncogenes play important roles in this regulation. Their functions appear to be at two levels. The first level is that of transduction of signals to the nucleus where the signals can be acted upon. The second is at the level of specific gene regulation, where incoming signals are turned into a response by the cell through activation of specific genetic programs. Nuclear proto-oncogene products play intimate roles in activation of these programs. The nature of the specific target genes regulated in response to these oncogene and proto-oncogene products however, remains a critical area of intensive research.

Cell Division↗
PubMed2005

A newly identified RET proto-oncogene polymorphism is found in a high number of endocrine tumor patients.

Multiple RET proto-oncogene transcripts, due to genomic variations and alternate splicing, have been described. To investigate endocrine tumor tissue characteristic RET proto-oncogene expression, we performed quantitative RT-PCR, Northern blot and Southern blot analyses of benign and malignant endocrine-derived tissues. We newly describe RET proto-oncogene expression in carcinoid-, gastrinoma- and insulinoma-derived tissue samples. In addition, the presence of a 3'-terminally truncated RET proto-oncogene mRNA variant in benign and malignant thyroid neoplasias, as well as in a pheochromocytoma, an ovarian carcinoma and a medullary thyroid carcinoma, is demonstrated. Southern blot analysis revealed no evidence of gross RET proto-oncogene rearrangements or deletions. As the underlying cause for a bi-allelic TaqI restriction fragment length polymorphism (RFLP), a C (allele 1)/T (allele 2) transition within intron 19, was characterized. This polymorphism is close to a recently described polyadenylation site and lies within a binding site for the nucleic acid binding protein Pbx-1. Screening of healthy subjects and of patients suffering from various endocrine malignancies revealed exclusively allele 1 homozygous and allele 1/allele 2 heterozygous genotypes. Heterozygous genotypes were found in a significantly higher percentage in samples derived from endocrine tumor patients when compared with those from healthy control subjects. Homozygosity for allele 2 was found exclusively in somatic DNA derived from endocrine tumors with high malignant potential. Analysis of DNA derived from varying regions within individual anaplastic thyroid carcinomas revealed an allele 1/allele 2 switch of the RFLP banding pattern, indicating loss of heterozygosity at the RET proto-oncogene locus. In conclusion, our data demonstrate presence of a 5'-terminal RET proto-oncogene transcript in endocrine tissues and reveal a bi-allelic RET proto-oncogene polymorphism. A heterozygous genotype for this polymorphism is found in a considerable number of endocrine tumor patients.

3' Untranslated Regions↗
PubMed1987

Immortalization by c-myc, H-ras, and Ela oncogenes induces differential cellular gene expression and growth factor responses.

Early-passage rat kidney cells were immortalized or rescued from senescence with three different oncogenes: viral promoter-driven c-myc, H-ras (Val-12), and adenovirus type 5 E1a. The normal c-myc and H-ras (Gly-12) were unable to immortalize cells under similar conditions. Quantitation of RNA in the ras-immortalized lines demonstrated that the H-ras oncogene was expressed at a level equivalent to that of the normal H-ras gene in established human or rat cell lines. Cell lines immortalized by different oncogenes were found to have distinct growth responses to individual growth factors in a short-term assay. E1a-immortalized cells were largely independent of serum growth factors, whereas c-myc-immortalized cells responded to serum better than to epidermal growth factor and insulin. H-ras-immortalized cells responded significantly to insulin alone and gave a maximal response to epidermal growth factor and insulin. Several cellular genes associated with platelet-derived growth factor stimulation, including c-myc, were expressed at high levels in the H-ras-immortalized cells, and c-myc expression was deregulated, suggesting that the H-ras oncogene has provided a "competence" function. H-ras-immortalized cells could not be morphologically transformed by secondary transfection with a long terminal repeat-c-myc oncogene, but secondary transfection of the same cells with H-ras (Val-12) produced morphologically transformed colonies that had 20- to 40-fold higher levels of H-ras oncogene expression. Thus, transformation in this system is dependent on high levels of H-ras oncogene expression rather than on the presence of activated H-ras and c-myc oncogenes in the same cell.

Adenovirus Early Proteins↗
PubMedDate not supplied

Oncogene expression in the peri-articular osteophytes.

OBJECTIVE: The aim of this study was to ascertain the proliferative and probably reparative potentials of the periarticular osteophytes by evaluating the sites of expression of c-myc, c-jun and c-fos oncogenes in this neoplastic repair tissue. MATERIALS AND METHODS: Sections of osteophytes were obtained from knees of patients undergoing total knee arthroplasty for osteoarthritis. Decalcified sections of osteophytes were stained for c-myc and c-jun oncogenes using the avidin HRP technique. Sections of breast carcinoma were used as positive controls. Undecalcified or frozen sections of osteophytes were stained for c-fos oncogene using the avidin alkaline phosphatase technique. Sections of the human skin were used as positive control. For both techniques, sections of normal articular cartilage were used as negative controls. RESULTS: The chondrocytes of the entire cartilage mantle of the peri-articular osteophyte had positive staining for c-myc oncogene but no staining for c-jun oncogene. The basal chondrocytes of the deep layer of the cartilage mantle of the peri-articular osteophyte had positive staining for c-fos oncogene. The normal articular cartilage sections had no staining for any of the oncogenes evaluated. CONCLUSION: The expression of c-myc oncogene in the osteophytic chondrocytes suggests that these cells are actively proliferating. However, c-fos expression in the basal chondrocytes implies that these cells are capable of transformation. This result confirms the proliferative ability of the peri-articular osteophytes and this may suggest that this osteochondral repair tissue, which is apparently wrongly sited, may be a source of tissue for osteochondral grafting for full thickness articular cartilage defects.

Cartilage, Articular↗
PubMed1994

Transformation by Raf and other oncogenes renders cells differentially sensitive to growth inhibition by a dominant negative c-jun mutant.

In NIH3T3 cells expressing active Raf-1 protein serine/threonine kinase (PSK) c-jun expression is constitutive while c-fos expression is attenuated. This alteration prompted us to determine whether oncogene transformation would render cells differentially sensitive to growth inhibition by a dominant negative mutant of c-jun, TAM 67. Growth inhibition was observed in three types of assays: (1) transfection of TAM 67 into cells stably transformed by a variety of oncogenes, (2) cotransfection of TAM 67 with oncogene expression plasmids into NIH3T3 cells and (3) titration of oncogene-expressing retroviruses on cells stably expressing TAM 67. The results clearly demonstrate that Raf-1 dependent oncogenes, which include receptor protein tyrosine kinases (PTKs)-, intracellular PTKs- and Ras-derived genes share the Raf phenotype of constitutive c-jun expression, attenuated c-fos induction, and high sensitivity to growth suppression by TAM 67. Additionally, the intracellular PSK oncogene, mos and the nuclear oncogenes c-myc, c-fos, and SV40 T antigen were TAM 67-sensitive for transformation. This universal pattern of altered growth regulation in oncogene transformed fibroblast cell lines highlights the potential usefulness of c-jun based inhibitors for control of tumor cell growth.

3T3 Cells↗
PubMed1996

Mutations in ras oncogenes: rare events in ultraviolet B radiation-induced mouse skin tumorigenesis.

The activation of ras proto-oncogenes by point mutation in a broad spectrum of clinical malignancies and experimentally induced tumors suggests their critical role in cancer induction. To determine whether the activation of ras proto-oncogenes by point mutation also contributes to ultraviolet B radiation (UVB)-induced skin tumorigenesis and whether this event is responsible for the different tumorigenic potentials of UVB radiation in different mouse strains, we analyzed the skin tumors induced by UVB in SKH-1 hairless and C3H mice for specific mutations in the Ha-, Ki-, and N-ras oncogenes. With the same UVB irradiation protocol, the latency period for tumor appearance was longer in C3H mice than in SKH-1 hairless mice. In addition, tumor incidence and multiplicity were also significantly higher (P<0.001, chi square and Wilcoxon rank sum tests) in SKH-1 hairless mice compared with C3H mice. None of the 30 skin tumor specimens (15 from each mouse strain) analyzed by polymerase chain reaction (PCR) amplification of specific codons followed by dot-blot hybridization with specific probes contained mutation in codons 13 of Ha-ras; 12, 13, and 61 of Ki-ras; or 12 and 13 of N-ras. However, three of the 15 tumors in SKH-1 hairless mice showed either a G35-->A or G35-->T transition at second position of Ha-ras codon 12. Interestingly, one of these tumors (with a G35-->A transition) also harbored an A182-->G mutation at second position of Ha-ras codon 61. None of the tumors from C3H mice showed mutations in codons 12 or 61 of the Ha-ras oncogene. With regard to codon 61 of the N-ras oncogene, six tumors from SKH-1 hairless mice and 10 tumors from C3H mice showed an A183-->T transversion. While G35-->A or G35-->T transition detected by PCR and dot-blot hybridization was confirmed by sequencing, the mutations identified similarly at codon 61 in either the Ha- or N-ras oncogenes could not be verified by sequencing of PCR-amplified products subcloned into plasmid vectors. With the exception of the low incidence of Ha-ras oncogene mutations at codon 12 in SKH-1 hairless mouse skin tumors induced by UVB, the striking absence of mutations in the Ha-, Ki-, and N-ras oncogenes in UVB-induced mouse skin tumors suggests that ras oncogene mutations are rare and thus are not an initiating event in photocarcinogenesis.

Amino Acid Sequence↗
PubMed1994

Immunity to the HER-2/neu oncogenic protein.

The study of oncogenic viruses led to the discovery that transforming retroviruses contain oncogenes homologous with and/or derived from cellular proto-oncogenes. In humans malignant transformation is often the result of the activation of proto-oncogenes. Normal proto-oncogenes can be activated to transforming proto-oncogenes by a variety of mechanisms including point mutation, translocation and amplification. Development of successful strategies for the immunotherapy of human cancers is an area of intense investigation. Part of the problem in developing cancer-specific immunotherapy has been the lack of well-defined tumour antigens. Our laboratory has focused on the question of whether oncogenic proteins expressed by transforming proto-oncogenes can serve as targets for immune attack. Some patients with HER-2/Neu-positive breast cancer have an existent immune response to the HER-2/neu protein with no clinical signs of autoimmunity, supporting the idea that overexpressed oncogenic proteins can be targeted in therapy without fear of destructive autoimmunity. The identification of candidate cytotoxic T lymphocyte epitopes might allow the generation of tumour-specific cytotoxic T lymphocytes for use in therapy and identify potential epitopes for peptide vaccines.

Amino Acid Sequence↗
PubMed1996

DNA damage and repair in oncogenic transformation by heavy ion radiation.

Energetic heavy ions are present in galactic cosmic rays and solar particle events. One of the most important late effects in risk assessment is carcinogenesis. We have studied the carcinogenic effects of heavy ions at the cellular and molecular levels and have obtained quantitative data on dose-response curves and on the repair of oncogenic lesions for heavy particles with various charges and energies. Studies with repair inhibitors and restriction endonucleases indicated that for oncogenic transformation DNA is the primary target. Results from heavy ion experiments showed that the cross section increased with LET and reached a maximum value of about 0.02 micrometer2 at about 500 keV/micrometer. This limited size of cross section suggests that only a fraction of cellular genomic DNA is important in radiogenic transformation. Free radical scavengers, such as DMSO, do not give any effect on induction of oncogenic transformation by 600 MeV/u iron particles, suggesting most oncogenic damage induced by high-LET heavy ions is through direct action. Repair studies with stationary phase cells showed that the amount of reparable oncogenic lesions decreased with an increase of LET and that heavy ions with LET greater than 200 keV/micrometer produced only irreparable oncogenic damage. An enhancement effect for oncogenic transformation was observed in cells irradiated by low-dose-rate argon ions (400 MeV/u; 120 keV/micrometer). Chromosomal aberrations, such as translocation and deletion, but not sister chromatid exchange, are essential for heavy-ion-induced oncogenic transformation. The basic mechanism(s) of misrepair of DNA damage, which form oncogenic lesions, is unknown.

Animals↗
PubMed1991

The v-abl, c-fms, or v-myc oncogene induces gamma radiation resistance of hematopoietic progenitor cell line 32d cl 3 at clinical low dose rate.

A variety of viral and cellular oncogenes have been described with differing mechanisms of action but with the common property of inducing morphologic alteration of cells in culture. Subclonal lines of oncogene expressing cells have been shown to produce tumors in vivo. Expression of the N-ras oncogene in embryo fibroblast NIH/3T3 cells has been demonstrated to increase radioresistance in vitro, and these results have been confirmed and extended to human cell lines expressing the c-raf oncogene. In the present report, we have examined the effects of expression of the c-fms, v-abl, or v-myc oncogene in a clonal hematopoietic progenitor cell line 32D cl 3. The 32D cell line is nonmalignant in vivo and is dependent upon a source of Interleukin-3 (IL-3) for growth in vitro. The radiation survival of 32D cl 3 cells transfected and expressed in the c-fms oncogene showed significant increase in the radioresistance at both 5 cGy/min and 116 cGy/min. A clone of 32D cl 3 transfected and expressing the v-myc oncogene demonstrated increased radioresistance at both dose rates. Results of split dose experiments suggested significant repair of sublethal irradiation damage of 32D-v-abl cells. Results were compared with expression of the same v-abl oncogene in the NIH/3T3 embryo fibroblast cell line. The data demonstrate that gamma irradiation resistance is significantly increased by each oncogene expressed in 32D cl 3 cells. The data on cell line 32D cl 3 may correlate with the radioresistance of v-abl expressing human hematopoietic cell malignancies treated by irradiation therapy.

Animals↗
PubMed1992

[Human papillomaviruses and cellular oncogenes (c-myc, c-Ha-ras) in cutaneous and mucosal lesions in transplantation recipients].

Transplant recipients develop numerous benign and malignant cutaneous and mucosal lesions in which histological signs of human papillomavirus (HPV) infection are observed. To investigate the role of HPV and c-myc and c-Ha-ras cellular oncogenes' activation in transplanted patients lesions, we used in situ hybridization with biotinylated probes and Southern blot to detect HPV and oncogenes DNA. We analyzed 36 lesions from grafted patients: 11 common warts, 10 actinic keratoses, 13 squamous cell carcinomas and 2 anogenital papillomas. With in situ hybridization, HPV DNA was detected in 14/36 lesions, 10 of which contained several HPV types. Benign and potentially oncogenic HPV types were detected in warts as well as in squamous cell carcinomas. The Southern blot technique confirmed the distribution of HPV types. Group specific viral antigen was detected in 12 lesions, mainly warts. C-Ha-ras oncogene was amplified in 13 lesions and c-myc oncogene in 10 lesions, 9 of which showed both oncogene amplification. The results obtained with in situ hybridization for c-myc gene amplification were confirmed with the Southern blot technique in 11/14 cases. Ras and/or myc amplification was more frequent in squamous cell carcinomas and anogenital papillomas than in warts and actinic keratoses. The amplification was not always linked to the presence of HPV DNA; however, it was more frequent in lesions infected by potentially oncogenic HPV types than in lesions containing only benign HPV types. Myc and p21 oncoproteins were respectively localized in the nucleus and on the membrane of epithelial cells by immunofluorescence. Most lesions showed a good concordance between the detection of oncogene DNA and proteins. Our results suggest than c-Ha-ras and c-myc cellular oncogenes' activation and HPV infection could play a role in the cancerization of cutaneous lesions from transplant recipients.

Genes, myc↗
PubMed1991

Modulation of differentiation in PA-1 human teratocarcinoma cells after N-ras oncogene-induced tumorigenicity.

We have been studying the effect of oncogenes on differentiation using the human ovarian teratoma-derived cell line PA-1. From this study we have characterized variants representing four stages relevant to multistage carcinogenesis, two non-tumorigenic and two tumorigenic. The two non-tumorigenic cell variants differ in that one is resistant to transformation by ras oncogenes whereas the other can be transformed to tumorigenicity. When these non-tumorigenic PA-1 variants are treated with retinoic acid (RA), a morphogen, they stop dividing, begin to express homeobox genes, and change in morphology. Transfection of an activated N-ras oncogene into ras-resistant non-tumorigenic PA-1 cells does not alter the RA responsiveness of the cells, indicating that expression of the activated oncogene is not sufficient for blocking RA-induced differentiation. Spontaneous activation of an N-ras oncogene leading to tumorigenic transformants and gene transfer-induced N-ras transformants are resistant to these effects of RA. However, another spontaneous transformant of PA-1 cells that does not contain an activated N-ras is responsive to RA. We prepared somatic cell hybrids of the RA-non-responsive, N-ras-transformed and tumorigenic PA-1 cell and the RA-responsive, ras-resistant non-tumorigenic PA-1 cell; the hybrid cell lines continue to express the oncogene but are non-tumorigenic. These non-tumorigenic hybrids are responsive to RA with regard to morphological changes, growth arrest and induction of homeobox gene expression. Tumorigenic revertants of these hybrids arise as a result of the loss of some chromosomes; these hybrid cells express the oncogene but have lost RA responsiveness. These results indicate that tumorigenic transformation in general is not sufficient to induce RA resistance, and resistance to differentiation may be oncogene-specific. In addition, the expression of an activated N-ras oncogene alone is insufficient to induce resistance to RA and ras-induced tumorigenicity is necessary. Therefore, some feature of cellular metabolism that is altered by and discordantly segregates with tumorigenic transformation controls responsiveness to RA. This controlling element is presumably a tumor suppressor.

Blotting, Northern↗
PubMed2006

Molecular mechanisms underlying the tumorigenesis of colorectal adenomas: correlation to activated K-ras oncogene.

Mutations of K-ras gene have been demonstrated in 40-50% of colorectal cancer and large adenoma (>1 cm). This study was intended to clarify the correlation between the existence of K-ras oncogene and the pathological features of colorectal adenomas using our recently developed membrane arrays. Moreover, the downstream genes regulated by K-ras oncogene were explored to serve as potential biomarkers in the early diagnosis and risk assessment of patients with colorectal adenoma. Specimens were collected from 70 patients with colorectal adenoma. The alterations of K-ras oncogene were analyzed by direct sequencing and our constructed membrane arrays, respectively. The results of direct sequencing showed that 21 of 70 samples (30%) had K-ras gene mutations. The most frequently mutated sites included codons 12, 13, 15 and 18. Furthermore, activated K-ras oncogene was identified in 18 of 70 (25.7%) adenoma by membrane arrays. Statistical analyses showed that the membrane array had the accuracy of 90.0%, sensitivity of 88.9%, and specificity of 90.4%. The frequency of the mutational sites of K-ras gene was located as follows: codon 12, 100% (4/4); codon 13, 100% (4/4); codon 15, 75% (6/8); and codon 18, 100% (2/2). The analysis of the correlation between the experimental data and pathological characteristics of adenoma showed that activated K-ras oncogenes were significantly associated with the size, number and histology of adenomas (all P<0.001). Finally, we found the downstream genes activated by K-ras oncogene, including B-cell CLL/lymphoma 2 (BCL2), Homo sapiens H2A histone family, member Z (H2AFZ), Homo sapiens RAP1B, member of RAS oncogene family (RAP1B), Homo sapiens T-box 19 (TBX19), Homo sapiens E2F transcription factor 4, p107/p130-binding (E2F4) and matrix metallopeptidase 1 (MMP1), of which were overexpressed in most of all examined adenomas. These genes were then suggested to have functions involved in cell growth. The preliminary results indicated that the accuracy of membrane arrays was comparable to conventional DNA sequencing in the detection of activated K-ras oncogenes. Therefore, we propose that activated K-ras oncogene in colorectal adenomas may play an important role in the subsequent colorectal carcinogenesis through a group of K-ras-related molecular targets.

Adenoma↗
PubMed1992

Prolonged inhibition by X-rays of DNA synthesis in cells obtained by transformation of primary rat embryo fibroblasts with oncogenes H-ras and v-myc.

Transfection of primary rat embryo fibroblasts with the H-ras oncogene plus the cooperating oncogene v-myc results in the development of foci of morphologically altered tumorigenic cells. We examined radiation (X-rays) induced inhibition of DNA synthesis in cell lines derived from such transformed clones and compared the results to those obtained with the nontransformed parental cells, rat embryo fibroblasts, as well as with cells immortalized either spontaneously, or after transfection with nuclear oncogenes (v-myc, E1A). Inhibition by X-rays of DNA synthesis was higher and persisted for longer periods of time in the H-ras- plus v-myc-transformed cell lines as compared to their nontrasformed counterparts. When the rate of DNA synthesis was measured as a function of dose 3 h after irradiation, biphasic curves were observed in all cell lines tested with a radiation sensitive and a radiation resistant component, known to correspond to inhibition of replicon initiation and chain elongation, respectively. A substantially larger inhibition of DNA synthesis was observed between 0 and 30 Gy in H-ras- plus v-myc-transformed cell lines, as compared to their nontransformed counterparts, presumably caused by sustained inhibition of replicon initiation. Hypersensitive DNA synthesis to X-rays was also observed in a transformed cell line obtained by transfection of rat embryo fibroblasts with H-ras in cooperation with the oncogene E1A, but normosensitive DNA synthesis in a rare transformant obtained by transfection with H-ras alone. These results suggest a direct or indirect involvement of the oncogene H-ras in cooperation with the oncogene v-myc (or other nuclear oncogenes such as E1A) in the control of DNA synthesis in irradiated cells. This control of DNA synthesis may be mediated via a trans-acting mechanism that involves the production of a diffusible factor in response to the radiation insult, or, by a cis-acting mechanism that directly affects the replication machinery. Circumstantial evidence for possible involvement of oncogenes of the ras and myc families in DNA synthesis support this hypothesis. There was an inverse correlation between sensitivity to radiation-induced killing and prolonged inhibition by radiation of DNA synthesis, with radioresistant cell lines displaying longer inhibition of DNA synthesis. However, inhibition by radiation of DNA synthesis was similar in normal human fibroblasts (W138) and cells derived from a radiation-resistant human carcinoma cell line (SQ-20B) suspected to carry an abnormal c-raf-1 oncogene.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

[Activation of ras oncogene in myelodysplastic syndrome and acute myelogenous leukemia].

N-ras oncogenes activated by point mutation have been frequently detected in various types of human leukemias. Analysis of a large number of leukemias revealed that activated N-ras oncogenes were observed preferentially in AML, AMoL, T-ALL and Null-ALL but rarely in CML and B-cell leukemia. These results suggest that N-ras oncogene plays an important role in human leukemogenesis. Activated N-ras oncogenes were also detected in myelodysplastic syndrome (MDS) that is considered to be a preleukemic disease. MDS patients bearing an activated N-ras oncogene frequently showed leukemic progression of the disease, suggesting that an activated N-ras oncogene can be a critical factor for prognosis of MDS patients. Thus, detection of an activated N-ras oncogene is useful for diagnosis, prognostic evaluation and therapeutic decision. Recently, we demonstrated that detection of the minimal residual disease by analysis of N-ras oncogene can lead to improvement of the remission rate in leukemias. Moreover, we made it possible to screen N-ras oncogene by a sensitive non-radioactive method. Our research procedure seems to be a good model for clinical application of the molecular biological technique.

Base Sequence↗
PubMedDate not supplied

Expression of HER-2/neu oncogene in normal, hyperplastic, and malignant endometrium.

HER-2/neu oncogene is believed to be involved in tumorigenesis of several human malignancies. To assess the pattern of expression of this oncogene in normal, hyperplastic, and neoplastic endometrium, immunocytochemistry was applied to paraffin-embedded tissue sections obtained from 146 patients with endometrial adenocarcinoma. A spectrum of hyperplastic changes ranging from simple hyperplasia to atypical hyperplasia was seen in 15 percent (22/146) of cases. Expression for HER-2/neu oncogene was demonstrated as cell membrane staining. Normal, hyperplastic and neoplastic epithelial cells showed a heterogeneous expression for HER-2/neu oncogene. The intensity of the immunostaining and the number of cells stained for HER-2/neu oncogene had no significant association with surgical stage or histologic grade, although the proportion of patients demonstrating overexpression increased significantly as the histologic grade of their tumor increased (p = 0.030). Furthermore, in a multivariate analysis, a statistically significant correlation was found between the level of expression of HER-2/neu oncogene and overall survival (p = 0.025). This study demonstrated that HER-2/neu oncogene expression is variably present in normal and hyperplastic endometrium. Association between HER-2/neu oncogene expression, higher grade lesions and poor survival in patients with endometrial cancer may also justify assessment of HER-2/neu oncogene as a reliable prognostic indicator.

Adult↗