Three human transforming genes are related to the viral ras oncogenes

Human colon carcinoma Ki-ras2 oncogene and its corresponding proto-oncogene

We isolated cDNA clones corresponding to the normal human Ki-ras2 gene and to the transforming allele of the Ki-ras2 gene present in the human colon carcinoma cell line SW480. These two cDNAs encode p21 proteins which differ only at the amino acid at position 12. The normal cDNA encodes a glycine at this position, and the transforming allele encodes a valine. Expression of these cDNAs indicates that this amino acid 12 alteration confers oncogenic activity on the mutated gene. Analysis of the relationship of the cDNAs and Kirsten sarcoma virus ras gene to a genomic clone allowed us to identify two alternative 3' coding exons for the Ki-ras2 gene, suggesting that the Ki-ras2 gene encodes two p21 proteins which differ at their carboxy termini. Our data also show that only one of the p21s is necessary to convert cells to a tumorigenic phenotype.

Epidermal growth factor stimulates guanine nucleotide binding activity and phosphorylation of ras oncogene proteins

Several human tumour cell lines contain genes that can transform NIH 3T3 cells into malignant cells. Certain genes have been classified as members of the ras oncogene family, namely, Ha-ras, Ki-ras or N-ras. The proteins encoded by the ras family are generally small (Ha-ras, for example, encodes a protein of molecular weight 21,000 named p21), and are associated with the inner surface of the plasma membrane. The only known biochemical property common to all forms of the ras proteins is the ability to bind guanine nucleotides, a property which may be closely related to the transforming ability of ras proteins. A GTP-dependent, apparent autophosphorylation (on threonine 59) activity has been identified only in the case of the v-Ha-ras protein. Although the role of these biochemical activities in the transformation process remains unclear, we have initiated studies to determine the possible biochemical interactions of ras proteins with other membrane components. We report here the evidence that epidermal growth factor enhances the guanine nucleotide binding activity of activated c-Ha-ras or v-Ha-ras p21, and phosphorylation of v-Ha-ras p21, suggesting that some mitogenic growth factors may regulate those activities.

Analysis of the transforming potential of the human H-ras gene by random mutagenesis

Some tumor cells contain mutant ras genes that are capable of transforming NIH 3T3 cells. Those genes that have been analyzed arise from the wild-type, non-transforming ras genes by mutations producing single amino acid substitutions at position 12 or 61 of the encoded protein. We have performed random bisulfite-induced mutagenesis on the cloned wild-type human H-ras gene to find if mutations at other positions can activate the transforming potential of that gene. Most mutations are not activating, but mutations that specify single amino acid substitutions at position 12, 13, 59, or 63 of the encoded protein do activate the transforming potential of the H-ras gene. Some, but not all, mutant ras proteins show an altered electrophoretic mobility in NaDodSO4/polyacrylamide gels.

Mechanism of activation of an N-ras oncogene of SW-1271 human lung carcinoma cells

An N-ras-related transforming gene was detected in the human lung carcinoma cell line SW-1271 and molecularly cloned. The lesion responsible for its acquisition of transforming activity was localized to a single nucleotide transition from A to G in codon 61 of the predicted protein. This lesion in the second exon results in the substitution of arginine for glutamine at this position. These findings, together with previous studies, indicate that the activation of ras oncogenes in human tumors is most commonly due to point mutations at one of two major "hot spots" in the ras coding sequence.

Characterization of a stable, anchorage-dependent clone obtained from a spontaneously transformed mouse cell line

A variant nontransformed clone, I21, was selected from the spontaneously transformed mouse fibroblast line, IT22. Selection was done by plating IT22 in methylcellulose and picking single cells after 2 d. Cultures derived from these single cells were selected again and one clone, I21, derived from the second round of selection was characterized extensively. I21 and IT22 have the same plating efficiency (PE) on plastic, but in agarose they differ by 1000-fold. In comparison to IT22, I21 has a normal morphological appearance, a lower saturation density, a higher viability in stationary phase, an increased doubling time, an increased chromosome content, and is unable to form tumors in nude mice. I21 has remained remarkably stable in culture and has not reverted to the transformed phenotype for at least 300 generations in culture. Over 100 clones of I21, expanded to 10(6) cells, failed to show an increased PE in agarose. Even expansion of the rare colonies of I21 that grow in agarose failed to produce clones similar to IT22.

Ha-ras oncogenes are activated by somatic alterations in human urinary tract tumours

DNA-mediated gene transfer (transfection) studies using NIH 3T3 cells as recipients have demonstrated the presence of transforming genes (oncogenes) in diverse human tumours. A large proportion of oncogenes so far detected by DNA transfection are related to the Ha-ras onc gene of Harvey (and BALB) murine sarcoma viruses (MSV), Ki-ras, the oncogene of Kirsten MSV, and a third member of the ras gene family, N-ras. Individual tumours of many different organs have been associated with the activation of members of the ras gene family. We now present the first systematic survey of human urinary tract tumours processed immediately after surgery, as well as normal tissues from the same patients, to detect the presence of such genes. We demonstrate activation of Ha-ras as an oncogene in around 10% of randomly selected urinary tract tumours as well as direct evidence that oncogene activation is the result of a somatic event which is selected for within the tumour cell population.

Photoaffinity labeling with GTP of viral p21 ras protein expressed in Escherichia coli

The v-ras oncogene of Harvey murine sarcoma virus encodes a 21,000-dalton protein, p21, which mediates transformation produced by that virus. Previous work has shown that both p21v-rasH and the cellular homolog p21c-rasH appear to bind guanine nucleotides. We report here the expression in Escherichia coli of v-rasH to produce a biochemically active p21 fusion protein which retains both guanine nucleotide binding and autophosphorylating activity. Furthermore, direct interaction of this protein with GTP is unequivocally demonstrated by photoaffinity labeling it with [alpha-32P]GTP.

Human oncogenes

The information published on human oncogenes up to the fall of 1983 is reviewed. Retroviral oncogenes, proto-oncogenes, and cellular transforming genes are compared. Transforming genes derived from the ras gene family are described in detail. The different mechanisms of activation of proto-oncogenes are summarized. Finally, the concerted or sequential action of cellular transforming genes in the multi-step process of carcinogenesis is discussed.

Isolation and characterization of a stage-specific transforming gene, Tlym-I, from T-cell lymphomas

A cellular transforming gene detected by transfection of mouse T-cell lymphoma DNA has been isolated by molecular cloning. This gene (designated Tlym-I) is homologous to a small conserved family of sequences present in normal mouse and human DNAs but is not related to any of the previously described viral or cellular transforming genes.

Saccharomyces cerevisiae synthesizes proteins related to the p21 gene product of ras genes found in mammals

A family of normal vertebrate genes and oncogenes has been called the ras gene family. The name ras was assigned to this gene family based on the species of origin of the viral oncogenes of the rat-derived Harvey and Kirsten murine sarcoma viruses. There are now three known functional members of the ras gene family, and genes homologous to ras genes have been detected in the DNA of a wide variety of mammals and in Drosophila melanogaster. Prior experiments have detected proteins coded for by ras genes in a large number of normal cells, cell lines, and tumors. We report here the detection of ras-related proteins in D. melanogaster, a result predicted by the earlier detection of ras-related genes in the Drosophila genome. We also report for the first time the detection of ras-related proteins in a single-cell eucaryocyte, Saccharomyces cerevisiae. These proteins, approximately 30K in size, are recognized by both a monoclonal antibody which binds to the p21 coded for by mammalian ras genes and a polyclonal rat serum made by transplanting a v-Ha-ras-induced tumor in Osborne-Mendel rats. The p21 of v-Ha-ras and the 30K proteins from S. cerevisiae share methionine-labeled peptides as detected by two-dimensional tryptic peptide maps. The results indicate that S. cerevisiae synthesizes ras-related proteins. A genetic analysis of the function of these proteins for yeast cells may now be possible.

A transforming ras gene in tumorigenic guinea pig cell lines initiated by diverse chemical carcinogens

Fetal guinea pig cells were transformed by treatment with four different chemical carcinogens including nitroso compounds and polycyclic hydrocarbons. As a consequence of this treatment, oncogenes capable of transforming NIH/3T3 cells became activated in each of five independently established clonal guinea pig cell lines. Molecular characterization of representative NIH/3T3 transformants revealed that the same oncogene was present in each of the cell lines tested. Moreover, detection of this transforming gene paralleled the acquisition of tumorigenic properties by these neoplastic cells.

Chromosome localization in normal human cells and neuroblastomas of a gene related to c-myc

Cellular oncogenes comprise a class of genes whose aberrant expression or function may be involved in the development of tumours. Indeed, several naturally occurring animal and human tumours are associated with consistent alterations in the structure or genomic position of particular cellular oncogenes. Recently, we isolated a DNA segment having limited similarity to c-myc (termed N-myc) from a human neuroblastoma cell line. Although N-myc was present as a single copy in normal cells, it was selectively amplified up to 140-fold in tumour cells from human neuroblastomas. Now, we have used somatic cell hybrids to show that N-myc is normally localized on the distal short arm of chromosome 2, and in situ hybridization to localize N-myc to chromosome 2p23-24. Further, in situ hybridization localizes amplified N-myc in neuroblastoma cells to homogeneously staining regions (HSRs) on different chromosomes. Thus, our results suggest that amplification and translocation of N-myc may be interrelated processes associated with human neuroblastoma, and demonstrate that the site of N-myc amplification is quite variable and bears no apparent relationship to either the normal single-copy locus or recognized sites of non-random chromosome alteration in human neuroblastoma.

Transforming ras genes from human melanoma: a manifestation of tumour heterogeneity?

Variability in the phenotype of cells comprising individual tumours is a striking feature of animal and human cancer and is generally referred to as tumour heterogeneity. Studies of clonally derived cell populations from tumours that originated presumably from a single transformed cell have shown that tumours are made up of cells that differ in a variety of traits, including drug resistance, antigen expression and metastatic potential. The origin and maintenance of tumour heterogeneity are unclear, but mutational and epigenetic mechanisms are thought to be involved. Here we report the results of a search for transforming genes in human melanoma which have raised the possibility that ras gene activation follows the same variable pattern as other traits involved in tumour heterogeneity. DNA from 4 of 30 melanoma cell lines yielded transforming ras genes in the NIH/3T3 assay. Of five cell lines originating from separate metastatic deposits of a single patient, only one contained activated ras, indicating heterogeneity in ras activation in this case and suggesting that ras activation was not involved in tumour initiation or maintenance in this patient.

The human c-Ha-ras2 is a processed pseudogene inactivated by numerous base substitutions

The human c-Ha-ras2 gene, one of two known members of the Harvey ras family, is reportedly located on the X-chromosome and has lost introns (1, 2). There has heretofore been no information on its precise gene structure and oncogenic potential. We have determined the nucleotide sequence of the c-Ha-ras2 and demonstrate that it is a processed pseudogene surrounded by several direct repeats and contains numerous base substitutions as well as a notable mutation (AGT at codon 12 of the p21 protein) responsible for oncogenic conversion of the known ras genes (3-8).

Somatic activation of rasK gene in a human ovarian carcinoma

A tumor isolate from a patient with serous cystadenocarcinoma of the ovary contained an activated rasK gene detected hy transfection of NIH/3T3 cells. In contrast, DNA from normal cells of the same patient lacked transforming activity, indicating that activation of this transforming gene was the consequence of somatic mutation in the neoplastic cells. The transforming gene product displayed an electrophoretic mobility in sodium dodecyl sulfate-polyacrylamide gels that differed from the mobilities of rasK transforming proteins in other tumors, indicating that a previously undescribed mutation was responsible for activation of rasK in this ovarian carcinoma.

Malignant activation of a K-ras oncogene in lung carcinoma but not in normal tissue of the same patient

A single genetic alteration, a guanine-to-cytosine transversion, is responsible for the acquisition of malignant properties by K-ras genes of two human tumor cell lines established from carcinomas of the bladder (A1698) and lung (A2182). As a consequence, arginine instead of the normal glycine is incorporated into the K-ras-coded p21 proteins at amino acid position 12. This mutation creates a restriction enzyme polymorphism that can be used to screen human cells for transforming K-ras genes. This approach was used to identify the mutational event responsible for the malignant activation of a K-ras oncogene in a squamous cell lung carcinoma of a 66-year-old man; this point mutation was not present in either the normal bronchial or parenchymal tissue or in the blood lymphocytes. Hence, malignant activation of a ras oncogene appears to be specifically associated with the development of a human neoplasm.

Presence of a Kirsten murine sarcoma virus ras oncogene in cells transformed by 3-methylcholanthrene

Oncogenes have previously been reported in the DNAs of mouse fibroblast lines which had become transformed after in vitro exposure to the carcinogen 3-methylcholanthrene. These oncogenes are now shown to be versions of the cellular Kirsten ras gene and are therefore homologous to oncogenes detected in a variety of human tumor DNAs.

Activation of N-ras gene in bone marrow cells from a patient with acute myeloblastic leukaemia

Human tumour cell lines of various histological origin contain genes that can transform NIH 3T3 cells in culture. Most frequently the gene is an activated K-ras gene, more rarely an activated H-ras gene, and sometimes the recently discovered N-ras. Other transforming genes, distinct from ras, have been found in B- and T-cell leukaemias. Since most of the transforming genes have been identified in cell lines, it is still unclear at what stage the genes become activated. We have therefore initiated a study to determine if the presence of a transforming gene correlates with the clinical course of a malignant disease. Here we demonstrate the presence of a transforming N-ras gene in bone marrow cells from a patient with acute myeloblastic leukaemia at the outbreak of the acute disease phase. Fibroblast DNA from the same patient was not transforming. In contrast to HL-60 cells, no alteration of the myc gene was detected.

Saccharomyces cerevisiae synthesizes proteins related to the p21 gene product of ras genes found in mammals

A family of normal vertebrate genes and oncogenes has been called the ras gene family. The name ras was assigned to this gene family based on the species of origin of the viral oncogenes of the rat-derived Harvey and Kirsten murine sarcoma viruses. There are now three known functional members of the ras gene family, and genes homologous to ras genes have been detected in the DNA of a wide variety of mammals and in Drosophila melanogaster. Prior experiments have detected proteins coded for by ras genes in a large number of normal cells, cell lines, and tumors. We report here the detection of ras-related proteins in D. melanogaster, a result predicted by the earlier detection of ras-related genes in the Drosophila genome. We also report for the first time the detection of ras-related proteins in a single-cell eucaryocyte, Saccharomyces cerevisiae. These proteins, approximately 30K in size, are recognized by both a monoclonal antibody which binds to the p21 coded for by mammalian ras genes and a polyclonal rat serum made by transplanting a v-Ha-ras-induced tumor in Osborne-Mendel rats. The p21 of v-Ha-ras and the 30K proteins from S. cerevisiae share methionine-labeled peptides as detected by two-dimensional tryptic peptide maps. The results indicate that S. cerevisiae synthesizes ras-related proteins. A genetic analysis of the function of these proteins for yeast cells may now be possible.

Tumor viruses, oncogenes, and human cancer

We review the biology of transforming retroviruses and their relationship to cellular transforming genes (tumor oncogenes). Evidence is discussed for the involvement of a retrovirus in a newly described syndrome, "adult T cell leukemia/lymphoma," which has a high incidence of skin involvement. This virus is related to the animal retroviruses which induce tumors in susceptible hosts after a long latent period. Cellular transforming genes encode proteins which directly change the oncogenic potential of a cell. These genes, which are altered forms of normal cellular genes, have been isolated from a wide variety of human tumors. Viral and cellular transforming genes produce their changes by at least two different mechanisms: abnormally high production of the normal protein encoded by these genes, or normal levels of an altered form of the protein.

Isolation of transforming sequences of two human lung carcinomas: structural and functional analysis of the activated c-K-ras oncogenes

Human lung tumors PR310 and PR371 maintained in nude mice contain activated c-K-ras oncogenes detectable by the ability of their DNAs to induce the morphological transformation of NIH 3T3 mouse fibroblasts. Using phage libraries constructed with DNA from NIH 3T3 mouse fibroblast transformants, we have isolated human sequences that span greater than 40 kilobase pairs of the c-K-ras oncogene. Based on the conservation of these human sequences in mouse fibroblast transformants, we conclude that the transforming ability of the oncogene activated in these tumors resides within a 43- to 46-kilobase-pair DNA region. No clear differences were observed between the structures of the PR310 and PR371 cloned oncogene sequences. Nucleotide sequence analysis in concert with DNA transfection experiments suggests that the PR371 oncogene has been activated by a single base change in the first exon, which results in the substitution of cysteine for glycine in position 12 of the predicted amino acid sequence. The genetic alteration responsible for the transforming activity of the PR310 oncogene, however, does not reside in the first exon. These results indicate that the activation of the c-K-ras oncogene in human lung cancer can occur by different mutational events.

Induction of mammary carcinomas in rats by nitroso-methylurea involves malignant activation of H-ras-1 locus by single point mutations

Each of nine mammary carcinomas induced by a single injection of nitroso-methylurea into 50-day-old Buf/N female rats, contained a transforming H-ras-1 gene. Molecular characterization of one of the genes revealed that the twelfth codon was GAA instead of GGA of the normal allele, encoding glutamic acid in place of glycine. These results indicate that chemical carcinogenesis represents an adequate model to study the role of transforming ras genes in human neoplasia.

Regional chromosomal localization of N-ras, K-ras-1, K-ras-2 and myb oncogenes in human cells

The identification of transforming genes in human tumor cells has been made possible by DNA mediated gene transfer techniques. To date, it has been possible to show that most of these transforming genes are activated cellular analogues of the ras oncogene family. To better understand the relationship between these oncogenes and other human genes, we have determined their chromosomal localization by analyzing human rodent somatic cell hybrids with molecularly cloned human proto-oncogene probes. It was possible to assign N-ras to chromosome 1 and regionally localize c-K-ras-1 and c-K-ras-2 to human chromosomes 6pter-q13 and 12q, respectively. These results along with previous studies demonstrate the highly dispersed nature of ras genes in the human genome. Previous reports indicated that the c-myb gene also resides on chromosome 6. It has been possible to sublocalize c-myb to the long arm of chromosome 6 (q15-q21). The non-random aberrations in chromosomes 1, 6 and 12 that occur in certain human tumors suggest possible etiologic involvement of ras and/or myb oncogenes in such tumors.

Transformation of Bloom's syndrome fibroblasts by DNA transfection

Nonmalignant diploid human fibroblast cells (GM3498B) derived from a skin biopsy of a patient with Bloom's syndrome have been transformed by transfection with DNA from a tumorigenic mouse cell line (Ha-8) carrying a single copy of the Harvey murine sarcoma virus (Ha-MuSV) genome. The transformed cell lines have an extended life-span, form colonies in agarose, and proliferate in nude mice--characteristics of neoplastic transformation. Like the parental cells, they also exhibit a high spontaneous level of sister chromatid exchanges. Finally, the transformed cells contain most, if not all, of the Ha-MuSV genome as well as the human rasH sequence. These experiments show that these diploid nonmalignant human cells can be used as recipients in transfection experiments for studying the genetic control of neoplastic transformation.

Presence of a Kirsten murine sarcoma virus ras oncogene in cells transformed by 3-methylcholanthrene

Oncogenes have previously been reported in the DNAs of mouse fibroblast lines which had become transformed after in vitro exposure to the carcinogen 3-methylcholanthrene. These oncogenes are now shown to be versions of the cellular Kirsten ras gene and are therefore homologous to oncogenes detected in a variety of human tumor DNAs.

Cellular oncogenes and multistep carcinogenesis

Two dozen cellular proto-oncogenes have been discovered to date through the study of retroviruses and the use of gene transfer. They form a structurally and functionally heterogeneous group. At least five distinct mechanisms are responsible for their conversion to active oncogenes. Recent work provides experimental strategies by which many of these oncogenes, as well as oncogenes of DNA tumor viruses, may be placed into functional categories. These procedures may lead to definition of a small number of common pathways through which the various oncogenes act to transform cells.

Localization of the c-ab1 oncogene adjacent to a translocation break point in chronic myelocytic leukaemia

The human c-ab1 oncogene maps within the region (q34-qter) of chromosome 9 which is translocated to chromosome 22, the Philadelphia (Ph') chromosome, in chronic myelocytic leukaemia (CML). The position of the Ph' chromosomal break point is shown to be variable and, in one CML patient, has been localized immediately 5' of, or within, the c-ab1 oncogene. A DNA restriction fragment corresponding to this site has been molecularly cloned and shown to represent a chimaeric fragment of DNA from chromosomes 9 and 22.

Amplified DNA with limited homology to myc cellular oncogene is shared by human neuroblastoma cell lines and a neuroblastoma tumour

Amplified cellular genes in mammalian cells frequently manifest themselves as double minute chromosomes (DMs) and homogeneously staining regions of chromosomes (HSRs). With few exceptions both karyotypic abnormalities appear to be confined to tumour cells. All vertebrates possess a set of cellular genes homologous to the transforming genes of RNA tumour viruses, and there is circumstantial evidence that these cellular oncogenes are involved in tumorigenesis. We have recently shown that DMs and HSRs in cells of the mouse adrenocortical tumour Y1 and an HSR in the human colon carcinoma COLO320 contain amplified copies of the cellular oncogenes c-Ki-ras and c-myc, respectively. Both DMs and HSRs are found with remarkable frequency in cells of human neuroblastomas. We show here that a DNA domain detectable by partial homology to the myc oncogene is amplified up to 140-fold in cell lines derived from different human neuroblastomas and in a neuroblastoma tumour, but not in other tumour cells showing cytological evidence for gene amplification. By in situ hybridization we found that HSRs are the chromosomal sites of the amplified DNA. The frequency with which this amplification appears in cells from neuroblastomas and its apparent specificity raise the possibility that one or more of the genes contained within the amplified domain contribute to tumorigenesis.

Identification and molecular cloning of the human Blym transforming gene activated in Burkitt's lymphomas

DNAs of six Burkitt's lymphoma cell lines contained an activated transforming gene detected by transfection of NIH 3T3 cells. This gene was cloned from a recombinant library of Burkitt's lymphoma DNA and identified as a human homologue of chicken Blym-1, the transforming gene detected by transfection of chicken B-cell lymphoma DNA.

Structure of the Ki-ras gene of the human lung carcinoma cell line Calu-1

The homologue of the viral Kirsten ras (v-Ki-ras) gene found in the human lung carcinoma cell line, Calu-1, has an intron-exon structure similar to that of the human homologue of the viral Harvey ras (v-Ha-ras) gene. A second, potential fourth coding exon is present in the human Ki-ras gene and similar sequences are found in the Kirsten murine sarcoma virus. Cysteine is encoded at the twelfth amino acid position, suggesting that the Calu-1 Ki-ras gene has undergone a mutational activation at the same position as the human Ha-ras gene of the bladder carcinoma cell line, T24. A comparison of their predicted amino acid sequences suggests that ras proteins have a 'constant' region and a 'variable' region. Here we propose a common modular structure for ras gene products in which the variable region forms a physiologically important combining site.

Structure and organization of the human Ki-ras proto-oncogene and a related processed pseudogene

Analysis of the organization and nucleotide sequence of two human loci related to the transforming gene of Kirsten murine sarcoma virus establishes one as a functional gene and the other as a processed pseudogene. The two final coding exons of the functional gene seem to have arisen by duplication. Differentially spliced mRNAs incorporating one or other of the duplicated exons probably served as the intermediates by which the viral transforming gene and the pseudogene were generated. This suggests that the functional gene may specify either of two related polypeptides depending on the pattern of RNA splicing.

Activation of Ki-ras2 gene in human colon and lung carcinomas by two different point mutations

Kirsten (Ki)-ras cDNA clones were prepared from human lung and colon carcinoma cell lines expressing an activated c-Ki-ras2 gene. DNA sequence analysis and transfection studies indicate that different point mutations at the same codon can activate the gene; that most human c-Ki-ras2 mRNA uses sequences from a fourth coding exon distinct from that of its viral counterpart; and that at least one cell line is functionally homozygous for the activated gene.

High efficiency DNA-mediated transformation of primate cells

Tissue culture cells from several mammalian species, including three primate lines, were transfected with recombinant vectors carrying Escherichia coli xanthine-guanine phosphoribosyltransferase or Tn5 aminoglycoside phosphotransferase dominant selectable markers. Human HeLa and SV40-transformed xeroderma pigmentosum cells exhibited stable transformation frequencies of at least 10(-3) (0.1 percent). CV-1, an African green monkey kidney cell line, could be stably transformed with the exceptionally high frequency of 6 X 10(-2) (6 percent).

Chromosomal assignment of a family of human oncogenes

A family of human transforming genes, previously shown to share homology with the ras family of viral oncogenes, maps to three different human chromosomes. A well-characterized mouse-human hybrid cell panel, combined with Southern blotting, was used in this study. The transforming gene of the T24 bladder carcinoma cell line maps to human chromosome 11. An oncogene isolated from the lung carcinoma cell line SK-Calu-1 maps to human chromosome 12. The third ras-related gene, cloned from SK-N-SH, a neuroblastoma cell line, maps to human chromosome 1.

Oncogenic genes and human malignancy

All vertebrates possess a series of genes which are homologs of the oncogenic genes of acute transforming retroviruses. Two lines of evidence suggest that these genes may play a role in the development of human malignancy: (1) DNA from a variety of human tumors transforms NIH 3T3 mouse fibroblasts and the transforming genes from a number of carcinomas, sarcomas, and hematological malignancies have been identified as members of a family of genes, the ras family, closely related to the oncogenic genes of the Harvey and Kirsten murine sarcoma viruses; and (2) correlations exist between the chromosomal localizations of certain oncogenes and the chromosomal breakpoints in specific translocations and deletions in certain human malignancies. In three separate hematological malignancies, alterations in more than one oncogenic gene may be involved in the neoplastic process.