RESUMEN
Residual leukemia is demonstrable by reverse transcriptase-polymerase chain reaction in most patients with chronic myeloid leukemia who obtain a complete cytogenetic response (CCR) to imatinib. In patients who relapse during imatinib therapy, a high rate of mutations in the kinase domain of BCR-ABL have been identified, but the mechanisms underlying disease persistence in patients with a CCR are poorly characterized. To test whether kinase domain mutations are a common mechanism of disease persistence, we studied patients in stable CCR. Mutations were demonstrated in eight of 42 (19%) patients with successful amplification and sequencing of BCR-ABL. Mutation types were those commonly associated with acquired drug resistance. Four patients with mutations had a concomitant rise of BCR-ABL transcript levels, two of whom subsequently relapsed; the remaining four did not have an increase in transcript levels and follow-up samples, when amplifiable, were wild type. BCR-ABL-kinase domain mutations in patients with a stable CCR are infrequent, and their detection does not consistently predict relapse. Alternative mechanisms must be responsible for disease persistence in the majority of patients.
Asunto(s)
Antineoplásicos/farmacología , Resistencia a Antineoplásicos/genética , Proteínas de Fusión bcr-abl/genética , Leucemia Mielógena Crónica BCR-ABL Positiva/enzimología , Proteínas Mutantes/fisiología , Mutación , Piperazinas/farmacología , Inhibidores de Proteínas Quinasas/farmacología , Pirimidinas/farmacología , Adulto , Anciano , Anciano de 80 o más Años , Antineoplásicos/uso terapéutico , Benzamidas , Cromatografía Líquida de Alta Presión , Codón/genética , Análisis Mutacional de ADN , ADN de Neoplasias/genética , Femenino , Estudios de Seguimiento , Proteínas de Fusión bcr-abl/fisiología , Humanos , Mesilato de Imatinib , Leucemia Mielógena Crónica BCR-ABL Positiva/tratamiento farmacológico , Leucemia Mielógena Crónica BCR-ABL Positiva/genética , Masculino , Persona de Mediana Edad , Proteínas Mutantes/genética , Piperazinas/uso terapéutico , Inhibidores de Proteínas Quinasas/uso terapéutico , Estructura Terciaria de Proteína/genética , Pirimidinas/uso terapéutico , ARN Mensajero/genética , ARN Neoplásico/genética , Inducción de Remisión , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Negativa del Paciente al TratamientoRESUMEN
BACKGROUND: Differentiating gastrointestinal stromal tumors (GISTs) from other intramural mesenchymal tumors of the GI tract on fine-needle aspiration biopsies (FNABs) is difficult. Recent studies have shown that GISTs are immunophenotypically and genetically distinct. GISTs exhibit consistent immunohistochemical expression of CD-117 (KIT) and often express activating mutations of this protooncogene. The aim of the current study was to employ immunocytochemistry and mutational analysis of the c-kit gene to aid in the diagnosis of GISTs on FNAB. METHODS: Five endoscopic ultrasound-guided FNABs of gastrointestinal spindle cell neoplasms performed at the Veterans Affairs Medical Center (VAMC) in Portland, Oregon, from 1998-1999 were reviewed. A panel of immunocytochemical stains was performed on each cellblock including CD-117 (KIT), smooth muscle actin (SMA), desmin, S-100, and CD34. Genomic DNA (gDNA) was extracted, and amplification of exons 9, 11, 13 and 17 of c-kit was performed by polymerase chain reaction (PCR) on CD-117 (KIT) and CD34 positive cases. Direct sequencing of amplicons identified the mutations. RESULTS: Five patients were diagnosed with GISTs based on morphology and immunocytochemical positivity for CD-117 and CD34. PCR analysis of c-kit exon 11 revealed three cases with novel-sized PCR bands in addition to the expected wild-type-sized PCR product. Amplicons from these cases contained an in-frame deletion mutation. One of the two cases with wild-type-;sized exon 11 amplicons was found to be heterozygous for a point mutation producing an amino acid substitution (W557R). No mutations in exon 9, 11, 13, or 17 of c-kit were found in the remaining case. CONCLUSIONS: Ancillary techniques such as immunocytochemistry and c-kit gene mutational analysis may aid in the diagnosis of GISTs on FNABs.