Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0026986 (myelodysplastic syndrome)
 14,926 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mutational activation of ras oncogenes is frequently encountered in human tumors. For unexplained reasons, K-ras mutations are predominantly found in pancreatic cancer, colorectal cancer and adeno-carcinoma of the lung, N-ras is predominantly found in a subset of acute leukemias and in myelodysplastic syndromes, while H-ras mutations are rare. In most tumors, ras mutations are not clearly associated with specific clinical or biological features, but in lung cancer, childhood lymphoblastic leukemia and possibly in myelodysplastic syndromes ras mutations may predict a poor prognosis. Accumulating evidence suggests that exposure to chemical carcinogens is responsible for many ras mutations in humans.
 ...
PMID:ras and human tumors. 142 Nov 68

We analyzed activating mutations of N-ras and K-ras by the polymerase chain reaction and oligonucleotide hybridization in hematological disorders. Activating mutations of these codons were detected in 4 of 20 cases of myelodysplastic syndrome (MDS) and 15 of 77 cases of acute myelogenous leukemia (AML). Our of 19 cases of MDS and AML who carried active mutations, 7 cases were found to have two or more distinct mutations in activating codons of N-ras and K-ras. Ras mutation was found preferentially in progressive disease such as refractory anemia with excess of blasts (RAEB) of RAEB in transformation (RAEB-t). A relatively high incidence of ras mutation was found in M5 AML (40%). No ras mutations were found in other hematological disorders, such as acute lymphoblastic leukemia and chronic myelogenous-leukemia. The most frequent amino acid substitution was that of an aspartate for glycine at codon 12 of N-ras resulting from G to A mutation (11/35). The survival of AML patients who carried ras mutations showed no significant differences from those without ras mutations calculated by Kaplan-Meier. Seven cases of MDS and 7 cases of AML patients could be investigated at various points during their clinical course. Among these 14 cases, we found 2 interesting cases of MDS. The first case lost multiple clones carrying ras mutations during disease progression, the second case acquired mutation of the ras gene during disease progression. These results suggested that multiple point mutations of ras genes may not be initiating events but may contribute to a clonal evolution of MDS and AML.
 ...
PMID:Multiple point mutation of N-ras and K-ras oncogenes in myelodysplastic syndrome and acute myelogenous leukemia. 157 46

Tumorigenesis in humans and experimental animals appears to involve the activation of ras protooncogenes for a number of organ systems and seems to be important to the development of the metastatic phenotype in several model systems. Clinically, the presence of activated ras protooncogenes has been reported to be a negative prognostic factor in the myelodysplastic syndrome and in adenocarcinoma of the lung. In the present study we examined 49 cases of endometrial carcinoma for mutations in the first exon of K-ras using the polymerase chain reaction and direct sequencing. Mutations in codon 12 or 13 of K-ras were detected in 6 of 49 cases (12.2%). These six cases consisted of five endometrioid endometrial carcinomas, each of which had a mutation in codon 12, and one case of clear cell carcinoma, which had a mutation in codon 13. In our study the presence of mutations in K-ras appeared to be an unfavorable prognostic factor. Three of six patients with the mutation died during follow-up, while only 7% of the 43 patients without K-ras mutations expired during this same period. In multivariate analysis using the Cox proportional hazard model, K-ras activation appeared to be an independent risk factor when compared with clinical stage, depth of myometrial invasion, and patient age. Thus, our findings support the hypothesis that K-ras protooncogene activation plays an important role in determining the aggressiveness of endometrial carcinoma.
 ...
PMID:Clinical implications of K-ras mutations in malignant epithelial tumors of the endometrium. 158 90

The presence of activated transforming genes was investigated in four patients with therapy-related leukemia and in three with therapy-related myelodysplastic syndrome. DNA of bone marrow cells from six of the patients exhibited transforming activity in the tumorigenicity assay. Five of the six patients who were positive in the tumorigenicity assay contained activated N-ras oncogenes, and three contained activated K-ras oncogenes. Thus, concurrent activation of N-ras and K-ras oncogenes was observed in two patients. In vitro DNA amplification followed by oligonucleotide dot-blot analysis was used to investigate mutations in codons 12, 13, and 61 of the N-ras and K-ras oncogenes. Two patients exhibited an N-ras mutation, substituting aspartic acid (GAT) for glycine (GGT), and three patients exhibited an N-ras codon 13 mutation, substituting valine (GTT) for glycine. Two patients exhibited K-ras codon 12 mutations, substituting aspartic acid (GAT) or cysteine (TGT) for glycine (GGT), respectively, and one case exhibited a K-ras codon 61 mutation, substituting lysine (AAA) for glutamic acid (CAA). Cytogenetic analysis revealed that loss of chromosome 7 was frequent (four patients: 57%). Our data indicate that activation of N-ras and K-ras genes, as well as loss of heterozygosity for specific alleles on chromosome 7, plays a more important role in the leukemogenesis of both therapy-related leukemia and myelodysplastic syndrome.
 ...
PMID:Transforming genes and chromosome aberrations in therapy-related leukemia and myelodysplastic syndrome. 185 83

ras gene mutations are the most frequent molecular changes found in the preleukemic syndromes of adults and may play a role in initiating these diseases and in their progression to acute leukemia. However, little is known about the incidence or importance of these genetic mutations in childhood myeloproliferative states (MPS). The bone marrow (BM) monosomy 7 syndrome accounts for a large percentage of childhood MPS. Although the duration of the MPS is quite variable, children with monosomy 7 eventually develop acute myeloid leukemia (AML). We investigated 20 children (13 with MPS, 7 with AML) with BM monosomy 7 or 7q- for the presence of ras gene mutations using the polymerase chain reaction and hybridization with mutation-specific oligonucleotides. Mutations of N-ras and K-ras were detected in three children. Two patients carrying a ras mutation were in the myeloproliferative phase, and one had acute leukemia. All three patients with ras mutations either died of their disease or relapsed after BM transplantation as compared with 8 of 17 without ras mutations. However, this difference is not statistically significant (P = .14, not significant). We conclude that ras mutations are observed in childhood monosomy 7, though less frequently than in adult MDS, and may play a limited role in the progression of this disease to acute leukemia. More patients are needed to address the prognostic role of ras mutations in this rare disease.
 ...
PMID:Mutations of the ras proto-oncogenes in childhood monosomy 7. 199 Nov 70

We have screened a large series of primary human leukemias for activating point mutations at codons 12, 13 and 61 of the N-ras and K-ras proto-oncogenes and at codons 12 and 61 of the H-ras proto-oncogene by using panels of oligonucleotide probes in conjunction with polymerase chain reaction gene amplification. 13 of 64 (20%) acute lymphoblastic leukemia cases had ras gene mutations mostly involving N-ras codon 12/13, G-A (gly-asp) transitions. Consistent with previous studies, a comparable pattern and frequency of ras mutation was found amongst 45 cases of acute myeloid leukemia and myelodysplasia. By contrast, of 30 cases of mature B cell chronic lymphocytic leukemia, only one in terminal prolymphocytoid transformation harboured an activated ras gene. These patterns of mutation did not correlate with ras gene methylation state, a finding not obviously compatible with differential gene accessibility being an important determinant of ras gene mutation patterns in leukemogenesis. Our data suggest that activated ras is more important in tumourigenesis of immature than mature lymphocyte progenitors whilst similar mechanisms associated with aetiology and/or target cell susceptibility probably underlie the similar patterns of ras gene mutations seen in acute leukemias of both myeloid and lymphoid cell lineages.
 ...
PMID:Analysis of ras gene mutations and methylation state in human leukemias. 266 44

Activation of the cellular oncogene c-N-ras has been frequently observed in DNA from leukemic cells in acute myeloid leukemia (AML). Ras gene activation sufficient to mediate in vitro transformation and rodent tumorigenesis usually results from point mutations and amino acid substitutions in the 12th or 61st codons. In AML and the related myelodysplastic syndromes, amino acid substitution at the 13th codon has been observed. An activated c-N-ras gene from a 45-year-old patient with AML was isolated by transfection analysis and subjected to molecular cloning and sequence analysis. A point mutation of the 12th codon (GGT to GAT) resulting in aspartic acid substitution for glycine was observed. In other neoplasms such as colon cancer, specific ras mutations occur predominantly (e.g., K-ras, codon 12). This predominance has been of demonstrable value in analyzing large cohorts for ras activation with techniques that are rapid and economical, such as oligonucleotide hybridization. It had previously been thought that such a predominance for activation of c-N-ras at codon 13 existed in AML; however, this study in concert with others underscores the importance of 12th codon c-N-ras mutations, along with 13th and 61st codon mutations in the molecular pathogenesis of AML. Guanylate to adenylate transition mutations are commonly observed in AML and may provide insight into potential environmental leukemogens. Addressing all commonly prevalent ras activating mutations bears impact in the future design of molecular surveys of the role of ras activation in leukemogenesis.
 ...
PMID:12th codon mutation resulting in c-N-ras activation in acute myelogenous leukemia. 327 72

Somatic mutation of the N-ras oncogene occurs frequently in de novo acute myeloid leukemia (AML). By virtue of their relation to AML, myelodysplastic syndromes (MDS) provide an in vivo model of human leukemogenesis. By using a strategy for analysis of gene mutation based on in vitro amplification of target sequences by the polymerase chain reaction (PCR) and selective oligonucleotide hybridization we analyzed the mutational status of codons 12, 13, and 61 of Ha-ras, K-ras, and N-ras in peripheral blood (PB) and/or bone marrow (BM) in 34 cases of primary MDS. Mutations at codon 12 of Ki-ras or N-ras were detected in three cases (9%): one of six cases of refractory anemia with excess blasts (RAEB) and two of nine cases of chronic myelomonocytic leukemia (CMML). The nucleotide substitution differed in each. In all cases the mutant allele was detectable in PB cells. A sustained hematologic remission was achieved after low-dose cytarabine therapy in the case of RAEB. Neither case of CMML exhibited signs of disease progression during follow-up at 7 and 12 months. In contrast, four of 31 patients without the ras mutation underwent transformation to AML within 12 months of genetic analysis. We conclude that ras mutations in MDS are heterogeneous and may develop at an early stage during the evolution of MDS. Their detection in PB cells illustrates the potential utility of ras mutation as a clonal marker in myeloid malignancy.
 ...
PMID:Mutation of Ki-ras and N-ras oncogenes in myelodysplastic syndromes. 328 9

Activation of the N- and K-ras proto-oncogenes is the most common molecular abnormality in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). In retrospective studies, approximately 3-36% of MDS patients were reported to harbor a mutated ras proto-oncogene, with some series suggesting the presence of ras-mutations are associated with progressive disease and a poor prognosis. Since hematopoietic growth factors such as granulocyte colony-stimulating factor (G-CSF) are currently used for therapy in MDS but may stimulate the proliferation of leukemic cells, we assessed the frequency and significance of ras mutations in 27 MDS patients, 15 of whom underwent G-CSF therapy. Patients were analyzed for the presence of mutations in codons 12, 13, and 61 of the N- and K-ras proto-oncogenes. Only three patients (11%, two refractory anemia with excess of blasts (RAEB), one RAEB in transformation (RAEB-T)) harbored activated ras oncogenes with the mutations localized in N-ras codons 12 and 61. Patients were followed for periods of up to 4 years or until death supervened. Patients exhibiting ras mutations were no more likely to develop AML compared to ras-negative patients (1/3 vs. 10/24) or to have decreased survival (p = 0.64). These data indicate that, in this group of MDS patients, ras mutations do not appear to correlate with a poor prognosis, and do not adversely interact with exogenously administered G-CSF.
 ...
PMID:Mutations in the ras proto-oncogenes in patients with myelodysplastic syndromes. 751 75

Mutations of the N- and K-ras genes are the most frequent genetic aberrations in acute myeloid leukemia (AML) and their detection in preleukemic conditions such as the myelodysplastic syndrome (MDS) suggests a role in the earliest phases of leukemogenesis. Despite these observations, little is known about the clinical importance of ras mutations in AML. We studied the clinical impact of ras mutations in 99 patients with de novo AML. All patients were treated in two prospective multicenter trials. The polymerase chain reaction was used to amplify areas surrounding the codons 12, 13, and 61 of the three ras genes N-, K-, and H-ras from DNA from bone marrow cells, ras mutations were detected by an algorithm based on allele-specific oligonucleotide hybridization. Eighteen of 99 (18%) patients harbored mutations in either N- or K-ras. All of the observed mutations occurred in N-ras (N = 10) and K-ras (N = 5) or concurrently in both N- and K-ras (N = 3). There were no significant differences between ras-negative and ras-positive patients according to age, sex, blood counts, cytogenetic abnormalities, or French-American-British classification. However, univariate analysis suggested a longer survival in ras-positive patients (P = .11). When adjusted for age, which was the most important factor affecting outcome, the presence of a ras mutation emerged as a significant predictor for improved survival (P = .03) and along with lower bone marrow blast counts (P = .02) and better cytogenetic category (P = .01). However, the presence of an aberrant ras allele was strongly correlated with lower bone marrow blast counts (P = .007). Thus, whether a mutation in the N-ras or K-ras proto-oncogenes directly affects treatment outcome or indirectly through an association with lower leukemic burden remains to be determined. Nevertheless, these findings counter the prevailing bias that oncogene mutations lead to more aggressive behavior in human malignancies.
 ...
PMID:Prognostic importance of mutations in the ras proto-oncogenes in de novo acute myeloid leukemia. 812 51


1 2 Next >>