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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transgenic mice bearing a mutant, activated N-ras oncogene directed to express within hematopoietic cells by an immunoglobulin enhancer (E mu) sporadically develop T-cell lymphomas and non-lymphoid tumors that may be of macrophage origin. To identify genes that can collaborate with N-ras in hematopoietic neoplasia, Moloney murine leukemia virus was used as an insertional mutagen. Infection of newborn E mu-N-ras mice with the virus greatly accelerated tumorigenesis, and nearly all the tumors proved to be T-cell lymphomas. Their variable surface phenotype (CD4+CD8-, CD4+CD8+ and CD4-CD8-) suggested that cells at several stages of T-cell development were susceptible to tumorigenesis. Southern blot analysis revealed that 68% of the tumors bore a proviral insert 5' to the c-myc gene, while 13% had an insert within the 3' untranslated region of the N-myc gene. Insertion was associated with elevated expression of these genes. Hence, activation of a myc gene appears to be the dominant pathway to tumorigenesis by insertional mutagenesis in lymphoid cells expressing a mutant ras gene. However, since many of the tumors were not transplantable, even the partnership of myc and ras may not suffice for full lymphoid malignancy.
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PMID:Retroviral infection accelerates T lymphomagenesis in E mu-N-ras transgenic mice by activating c-myc or N-myc. 157 Jan 58

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.
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PMID:[Activation of ras oncogene in myelodysplastic syndrome and acute myelogenous leukemia]. 205 67

The only ras oncogene as yet identified in cells from human fibrosarcomas is N-ras, but the relationship between N-ras oncogene expression and the malignant state of these cell lines is not known. To determine if expression of an N-ras oncogene causes human cells to become malignant, we transfected the N-ras oncogene from human leukemia cell line 8402, cloned into a high expression vector pSV N-ras, into MSU-1.1 cells, a nontumorigenic, infinite life span fibroblast cell strain with a normal morphology and a stable near-diploid karyotype. The transformants formed distinct foci composed of morphologically transformed cells. Cells from such foci expressed higher than normal levels of N-ras protein, exhibited growth factor independence, and formed large colonies in soft agar at a high frequency. Injection of progeny of these focus-derived cells s.c. into athymic mice resulted in progressively growing, invasive malignant tumors (round cell, spindle cell, or giant cell sarcomas) which reached a diameter of 6 mm in 3 to 4 weeks. Injection of focus-derived or tumor-derived cells i.v. resulted in tumors in various organs of the mice. The focus-derived cell strain tested, as well as the majority of the cells derived from the tumor it produced, exhibited the same near-diploid karyotype as the parental MSU-1.1 cells. Cells transfected with an N-ras oncogene that was expressed at a normal level formed only a single, indistinct focus, and cells from that focus were not malignant.
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PMID:Malignant transformation of human fibroblasts by a transfected N-ras oncogene. 220 39

Results of our study on the activation of N-ras oncogene by point mutation in human leukemia and myelodysplastic syndrome have been described in this article. Point mutation was observed mainly on the 12th, 13th and 61st amino acid codon of ras genes. Therefore, oligomers containing mutations at these codons were used as probes for dot blot analysis of DNA derived from patient's bone marrow cells or leukemia cells. Polymerase chain reaction technique was used to amplify the DNA of ras genes containing 12th, 13th and 61st codons. By this technique, sensitivity of the method to detect the point mutations in ras oncogene was remarkably increased. Detection of the mutation in ras gene is considered to be very useful for the diagnosis, determination of remission and finding of relapse at an early stage. Study on the fused gene of bcr-abl, its mRNA and protein in chronic myelogenous leukemia is a good and reliable method to prove the existence of Ph1 positive chromosome by gene technology. Identification of the Ph1 acute lymphoblastic leukemia (ALL) has become possible by studying abl oncogene in Ph1 positive ALL. This method can be used also for the diagnosis of Ph1 ALL.
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PMID:[Oncogenes in human leukemia]. 265 Jun 33

To determine if diploid human fibroblasts can be transformed by the N-ras oncogene found in human tumors, early passage cell lines were transfected with an N-ras oncogene from human leukemia cell line 8402 cloned into a high expression plasmid (pSV N-ras), with the N-ras oncogene from human fibrosarcoma cell line HT1080 cloned into pNR-MG1, or with pSV2neo as a control. Each plasmid carries the neo gene coding for Geneticin resistance, but in pSV N-ras, the endogenous promoter of the N-ras gene has been eliminated, and the gene has been inserted between the viral long-terminal repeat (LTR) and the neo gene so that transcription initiated from the LTR must transcribe the N-ras gene before transcribing neo. In pNR-MG1, transcription of the N-ras gene is driven from its endogenous promoter, and the neo gene is transcribed from an SV40 viral promoter, as in pSV2neo. When the transfectants were selected for Geneticin resistance, 70% of the colonies formed with pSV N-ras consisted of morphologically altered cells. Less than 5% of the drug resistant colonies formed with pNR-MG1 had cells with altered morphology, and the change in morphology was much less distinct than with pSV N-ras. No colonies of morphologically-transformed cells were found with pSVneo. If the transfected populations were not selected in Geneticin, but were simply allowed to grow to confluence, very distinct foci composed of morphologically-altered cells could be seen against a contact-inhibited monolayer with pSV N-ras. Foci formed by the pNR-MG1 population were subtle and much less distinct. No foci were found with pSV2neo. Representative colonies and foci of morphologically-transformed cells were isolated. Those from pNR-MG1 transfection reverted to a normal morphology after 5-10 population doublings. Most of those from pSV N-ras transfection either reverted or senesced after 5-10 population doublings. However, progeny of two colonies expressed stable morphological transformation throughout a normal life span equal to that of age-matched pSV2neo controls. Both of these stably transformed cell strains exhibited anchorage independence and formed distinct foci. Immunoprecipitation analysis showed that these cells produced much larger amounts of N-ras protein than did pSV2neo-transfected control cells. However, these two cell strains did not exhibit an infinite life span in culture and were unable to form tumors in athymic mice.
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PMID:Transformation of diploid human fibroblasts by transfection of N-ras-oncogenes. 270 11

Three cases of idiopathic myelofibrosis were screened for the presence of mutations at codon 12, 13, or 61 of the ras gene family by a rapid method based on polymerase chain reaction and hybridization to mutation-specific oligonucleotides. PB cells of one patient showed a point mutation at codon 12 of the N-ras oncogene. This molecular genetic hallmark was used to investigate the clonal relationship of different cell lineages by cell separation analysis. Presence of the N-ras 12 mutation in granulocytes, monocytes, B cells, and T lymphocytes, as well as erythroblasts, indicates that idiopathic myelofibrosis originates from a pluripotent stem cell, at least in this patient.
Leukemia 1988 Oct
PMID:Evidence for pluripotent stem cell origin of idiopathic myelofibrosis: clonal analysis of a case characterized by a N-ras gene mutation. 305 Feb 94

The relationship between chromosomal abnormality and oncogene activation was investigated during leukemic progression in two patients with myelodysplastic syndrome (MDS). Both patients had partial or complete deletion of chromosome 5 in metaphase cells obtained throughout the progression to leukemia. Analysis with specific oligonucleotide probes revealed that bone marrow cells containing an activated N-ras oncogene proliferated in a dominant manner during the process of leukemic conversion in both patients. These observations suggest that the chromosomal abnormality may precede activation of the N-ras gene in these patients, and that both the chromosomal abnormality and the activated N-ras oncogene contribute to the development of leukemia.
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PMID:Relationship between an activated N-ras oncogene and chromosomal abnormality during leukemic progression from myelodysplastic syndrome. 327 73

Patients with a myelodysplastic syndrome (MDS) which has a risk of leukaemic change exhibit a variable clinical course. It has been suggested that the development of leukaemia in patients with MDS may be related to chromosomal abnormalities or genetic alterations: somatic mutation of the N-ras gene is now considered to be a critical step in the genetic basis of human leukaemogenesis. Here we report that DNAs of bone-marrow cells from three out of eight patients with MDS contained an activated N-ras oncogene, as detected by an in vivo selection assay in nude mice with transfected NIH 3T3 cells. Molecular analysis revealed the same single nucleotide substitution at codon 13 in all three transforming N-ras genes. Each of the three patients showed a progression of the disease and a resulting leukaemic change within the following year. Our observation of the mutation at codon 13 in leukaemic cell DNAs from all three cases suggests that activation of the N-ras gene is important in the development of leukaemia in some MDS cases.
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PMID:A point mutation at codon 13 of the N-ras oncogene in myelodysplastic syndrome. 329 62

We have studied by means of DNA-mediated gene transfer the activation of protooncogenes in human myeloid leukemias that represent various stages of myeloid differentiation. DNA from three cell lines, HL-60 (promyelocytic leukemia), Rc2a (myelomonocytic leukemia), and KG-1 (acute myeloblastic leukemia), was capable of transforming NIH/3T3 cells. Hybridization analysis indicated that, in all three tumor cell lines, the N-ras oncogene was activated. The cell lines U-937 ("histiocytic lymphoma") and K-562 (erythroblastic leukemia) yielded no transforming DNA. Fresh leukemia cells derived from an acute myelomonocytic leukemia patient and from a juvenile chronic myelogenous leukemia patient contained an activated N-ras and c-Ki-ras oncogene, respectively. DNA from some other myelogenous leukemia patients was not able to transform NIH/3T3 cells. Our results indicate that hematopoietic tumors of the myeloid lineage may contain oncogenes active in NIH/3T3 cell transformation and that, in particular, the N-ras oncogene may be activated in tumors representing various stages of maturation.
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PMID:Oncogene activation in human myeloid leukemia. 385 67

DNA from human T-cell leukemia cell lines was tested for focus-inducing activity on cultures of NIH 3T3 cells. Three leukemias yielded DNA active in this assay; restriction enzyme sensitivity of this activity indicated that similar, relatively large DNA sequences were involved. Southern blot analysis revealed conserved size classes of restriction fragments containing human repetitive (Alu) sequences in serially transfected foci derived from the active DNAs. Similar blot hybridizations with a probe specific for the human N-ras oncogene detected a 9-kilobase EcoRI fragment in all cases. DNA containing this fragment from one of the leukemias, molecularly cloned in bacteriophage lambda, displayed highly amplified focus-inducing activity in transfection assays. Thus, the N-ras oncogene appears to be active in these three human leukemias of T-cell origin.
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PMID:Identification by transfection of transforming sequences in DNA of human T-cell leukemias. 660 34


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