RESUMO
Specific cytogenetic abnormalities predict prognosis in childhood acute myeloid leukemia (AML). However, it is unknown why they are predictive and whether this is related to drug resistance. We previously reported that Down syndrome (DS) AML was associated with favorable resistance profiles. Here, we successfully analyzed drug resistance and (cyto-) genetic abnormalities of 109 untreated childhood AML samples using the 4-day total cell-kill methyl-thiazolyl tetrazolium (MTT) assay. Patients were classified according to the genetic abnormalities in the leukemic cells: t(8;21), inv(16), t(15;17), t(9;11), other 11q23 translocations, abnormalities of chromosome 5/7, trisomy 8 alone, normal karyotype, single random, and multiple (defined as 2 or more) abnormalities. The DS AML samples were excluded from the subgroup analysis. Samples with chromosome 5/7 abnormalities were median 3.9-fold (P =.01) more resistant to cytarabine than other AML samples. The t(9;11) samples were more sensitive to cytarabine (median 2.9-fold, P =.002), etoposide (13.1-fold, P =.001), the anthracyclines (2.9- to 8.0-fold, P <.01), and 2-chlorodeoxyadenosine (10.0-fold, P =.002) than other AML samples. The trisomy 8 and t(15;17) groups were too small for meaningful analysis. All other genetic subgroups did not show specific resistance profiles. Overall, we found no differences in drug resistance in samples taken at diagnosis between patients remaining in continuous complete remission (CCR) versus the refractory/relapsed patients. Within several genetic subgroups, however, relapsed/refractory patients were more cytarabine resistant when compared with patients remaining in CCR, but numbers were small and the results were not significant. We conclude that some, but not all, cytogenetic subgroups in childhood AML display specific drug-resistance profiles.
Assuntos
Antineoplásicos/farmacologia , Aberrações Cromossômicas , Resistencia a Medicamentos Antineoplásicos/genética , Leucemia Mieloide/genética , Doença Aguda , Adolescente , Antibióticos Antineoplásicos/farmacologia , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Criança , Pré-Escolar , Inversão Cromossômica , Cromossomos Humanos/ultraestrutura , Cladribina/farmacologia , Citarabina/farmacologia , Resistência a Múltiplos Medicamentos/genética , Etoposídeo/farmacologia , Feminino , Humanos , Lactente , Leucemia Mieloide/classificação , Leucemia Mieloide/tratamento farmacológico , Leucemia Mieloide/patologia , Masculino , Células-Tronco Neoplásicas/efeitos dos fármacos , Recidiva , Indução de Remissão , Sais de Tetrazólio , Tiazóis , Translocação Genética , TrissomiaRESUMO
Infant acute lymphoblastic leukemia (ALL) with MLL gene rearrangements is characterized by a proB phenotype and a poor clinical outcome. We analyzed an infant proB ALL with t(2;11)(p15;p14) and an MLL rearrangement on Southern blot analysis. Rapid amplification of cDNA ends-polymerase chain reaction (PCR) and reverse transcriptase-PCR identified the LAF4 gene mapped on chromosome region 2q11.2-q12 as a fusion partner of the MLL gene. The LAF4 gene was identified previously by its high sequence homology to the AF4 protein and encodes a protein of 1,227 amino acids. The t(4;11)(q21;q23), creating the MLL-AF4 chimeric transcripts, is the predominant 11q23 chromosome translocation in infant ALL and is associated with an extremely poor prognosis. Our findings further suggest that fusion of MLL to one of the AF4 family members (AF4/LAF4/AF5Q31) might determine a proB-cell phenotype in infant leukemia.
