RESUMO
Two classes of oncogenic mutations of the c-kit tyrosine kinase have been described: the juxtamembrane domain V560G mutation, which is preferentially found in gastrointestinal stromal tumors (GISTs), and the kinase domain D816V mutation, which is highly representative of systemic mastocytosis (SM). Here we show that both mutations constitutively activate the mammalian target of rapamycin (mTOR) signaling pathway. Surprisingly, the mTOR inhibitor rapamycin induces only apoptosis in HMC-1 cells bearing the D816V but not the V560G mutation. In support of this unexpected selectivity, rapamycin inhibits the phosphorylation of 4E-BP1, a downstream substrate of the mTOR pathway, but only in D816V HMC-1 cells. Importantly, D816V mast cells isolated from SM patients or from transgenic mice are sensitive to rapamycin whereas normal human or mouse mast cells are not. Thus, rapamycin inhibition appears specific to the D816V mutation. At present there is no effective cure for SM patients with the D816V mutation. The data presented here provide a rationale to test whether rapamycin could be a possible treatment for SM and other hematologic malignancies with the D816V mutation.
Assuntos
Mastocitose Sistêmica/tratamento farmacológico , Mastocitose Sistêmica/genética , Mutação de Sentido Incorreto , Farmacogenética , Proteínas Proto-Oncogênicas c-kit/genética , Sirolimo/farmacologia , Animais , Apoptose/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Humanos , Mastócitos/efeitos dos fármacos , Mastócitos/patologia , Mastocitose Sistêmica/patologia , Camundongos , Camundongos Transgênicos , Proteínas Quinases/metabolismo , Transdução de Sinais , Serina-Treonina Quinases TOR , Células Tumorais CultivadasRESUMO
The growth factor-independent erythroleukemic cell line ERY-1 was established from the peripheral blood of a 87-year-old woman with chronic myeloid leukemia (CML) in the acute phase. Immunophenotyping showed that fresh leukemic cells were positive for CD13, CD33, CD36 and CD235a (glycophorin A), a phenotype compatible with that of erythroblastic cells. Cytogenetic and fluorescence in situ hybridization (FISH) analysis demonstrated classical t(9;22)(q34;q11) chromosomic translocation associated with a duplication of the BCR-ABL fusion gene. Other cytogenetic abnormalities were detected in all analyzed mitosis, the most frequent being a trisomy of chromosome 8. The established ERY-1 cell line retains these immunophenotypic and cytogenetic features, and light and electron microscopy confirmed the relatively mature erythroblastic phenotype of the cells. In addition, ERY-1 cell line expressed beta-globin mRNA and a non-phosphorylable form of the erythropoietin receptor, even in presence of erythropoietin. Of note, the proliferation of ERY-1 cells was inhibited by TGFbeta1 or STI-571 (Gleevec), without significant induction of further differentiation. In conclusion, ERY-1 is a new growth factor-independent human erythroleukemic cell line with a relatively mature phenotype that may be useful to study the molecular events involved in erythroblastic differentiation.
Assuntos
Linhagem Celular Tumoral , Leucemia Eritroblástica Aguda/patologia , Idoso , Idoso de 80 Anos ou mais , Antígenos CD/análise , Benzamidas , Cromossomos Humanos Par 8 , Feminino , Proteínas de Fusão bcr-abl/genética , Duplicação Gênica , Globinas/genética , Humanos , Mesilato de Imatinib , Imunofenotipagem , Leucemia Mielogênica Crônica BCR-ABL Positiva/patologia , Fenótipo , Piperazinas/farmacologia , Pirimidinas/farmacologia , Receptores da Eritropoetina/metabolismo , Fator de Crescimento Transformador beta/farmacologia , Fator de Crescimento Transformador beta1 , Translocação Genética , TrissomiaRESUMO
Two patients with Ph-positive chronic myelocytic leukemia in erythroblastic transformation and rearrangement of the short arm of chromosome 18 are reported. Fluorescence in situ hybridization studies showed that the 18p rearrangement resulted from translocation of the main part of chromosome 22 long arm to 18p, including BCR-ABL1 fusion. The 18p abnormality resulted, thus, in loss of 18p and duplication of BCR-ABL1 in both patients. The possible relation to the erythroblastic type of blastic phase is briefly discussed. In addition an apparently intact germline ABL1 gene was duplicated and inserted into chromosome 6 at band p21 in one of these patients.
Assuntos
Transformação Celular Neoplásica , Cromossomos Humanos Par 18/genética , Eritrócitos/patologia , Proteínas de Fusão bcr-abl/genética , Duplicação Gênica , Leucemia Mielogênica Crônica BCR-ABL Positiva/genética , Leucemia Mielogênica Crônica BCR-ABL Positiva/patologia , Idoso , Idoso de 80 Anos ou mais , Aberrações Cromossômicas , Cromossomos Humanos Par 22/genética , Feminino , Humanos , Hibridização in Situ Fluorescente , Cariotipagem , Pessoa de Meia-Idade , Translocação GenéticaRESUMO
Mastocytosis is a heterogeneous group of hematopoietic disorders characterized by abnormal growth and accumulation of mast cells (MC) in one or more organs. Clinical symptoms occur as a result of the release of chemical mediators and/or of pathologic infiltration of MC in various tissues. Although the initial events leading to mastocytosis have not yet been unraveled, acquired alterations in the c-kit gene coding for the receptor of stem cell factor (SCF), a major cytokine involved in MC growth, have been described in a significant number of patients. Of particular interest are point mutations resulting in a constitutively activated SCF receptor. Such mutations are probably involved in the abnormal (SCF-independent) proliferation of MC in these patients. New therapeutic strategies may be envisaged to inhibit the deregulated kinase activity of these mutant forms of c-kit.
