RESUMO
Cytogenetic analysis of mantle cell lymphoma (MCL), characterized by the presence of t(11;14)(q13;q32) translocation, is often difficult because of the low proliferating rate of MCL cells and the presence of normal cells in bone marrow which may interfere with growth of MCL cells. We describe herein a TPA (12-O-tetradecanoylphorbol 13-acetate) stimulated culture to improve detection of t(11;14)(q13;q32) in 20 MCL patients regardless of the samples used.
Assuntos
Cromossomos Humanos Par 11 , Cromossomos Humanos Par 14 , Linfoma de Célula do Manto/genética , Translocação Genética , Adulto , Idoso , Técnicas de Cultura de Células/métodos , Feminino , Humanos , Linfoma de Célula do Manto/diagnóstico , Masculino , Pessoa de Meia-Idade , Acetato de Tetradecanoilforbol/farmacologia , Células Tumorais CultivadasRESUMO
Targeting the tyrosine kinase activity of BCR-ABL represents a very promising therapeutic strategy in chronic myeloid leukemia (CML). Despite strong efficacy of the tyrosine kinase inhibitor STI571, resistance has been observed in a significant proportion of patients in advanced CML stage or in Ph-positive acute lymphoid leukemia (ALL). We investigated in this study the mechanism of resistance to STI571 through point mutations in the tyrosine kinase domain and/or BCR-ABL gene amplification in 24 patients (16 in chronic phase and 8 in accelerated phase of the disease) who obtained no cytogenetic response to STI571 treatment. Screening for the already-described Thr315Ile point mutation in the ABL domain using a reverse transcription polymerase chain reaction restriction fragment length polymorphism (RT-PCR-RFLP) technique, 3 patients showed a proportion of mutated transcript at the time of resistance. The same technique failed to detect mutation at diagnosis, but a specific allele-specific oligonucleotide (ASO)-PCR on DNA for the Thr315Ile mutation and, after sequencing, for 2 newly described Phe311Leu and Met351Thr substitutions, showed the presence of rare mutated cells prior to STI571 therapy. Furthermore, the increased proportion of mutated cells during treatment detected by ASO-PCR strongly suggested clonal selection by the functional inhibiting effect of these mutations. Finally, no BCR-ABL gene amplification was detected by fluorescent in situ hybridization (FISH) in the 24 STI571-resistant patients. Our data support that in CML patients treated with STI571, ABL mutations are not restricted to the accelerated phase of the disease and that, at least in some cases, mutations seem to occur prior to STI571 therapy, probably as second mutational events during the course of CML.
Assuntos
Resistencia a Medicamentos Antineoplásicos/genética , Genes abl/genética , Leucemia Mielogênica Crônica BCR-ABL Positiva/genética , Mutação , Piperazinas/uso terapêutico , Pirimidinas/uso terapêutico , Alelos , Substituição de Aminoácidos , Benzamidas , Divisão Celular , Células Clonais/patologia , Análise Mutacional de DNA , Feminino , Genes abl/fisiologia , Humanos , Mesilato de Imatinib , Leucemia Mielogênica Crônica BCR-ABL Positiva/tratamento farmacológico , Masculino , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase/métodos , Proteínas Tirosina Quinases/genética , Estudos RetrospectivosRESUMO
The core-binding factor (CBF) complex is a heterodimeric transcription factor composed of 2 subunits, CBFalpha and CBFbeta, that play a major role in hematopoiesis. Both members of the CBF complex are frequently altered in acute myeloid leukemia (AML) by translocation, most commonly t(8;21), t(12;21), and t(3;21) for CBFalpha, located in 21q22, and inv(16)(p13;q22) for CBFbeta, located on 16q22. Recently, a new mechanism of alteration of CBFalpha, by point mutation, has been reported in myeloid malignancies, particularly in M0 AML. In the present study, we found no point mutation of the CBFbeta gene in 30 myelodysplastic syndromes and 100 AMLs, suggesting a limited role, if any, of CBFbeta point mutations in those disorders.
