title: Development of an NPM1/MLF1 D-FISH probe set for the detection of t(3;5)(q25;q35) identified in patients with acute myeloid leukemia.
abstract: The t(3;5)(q25;q35) NPM1/MLF1 fusion has an incidence of approximately 0.5% in acute myeloid leukemia (AML) and has an intermediate prognosis at diagnosis. We have developed a dual-color, dual-fusion fluorescence in situ hybridization (D-FISH) assay to detect fusion of the MLF1 and NPM1 genes. A blinded investigation was performed using 25 normal bone marrow specimens and 26 bone marrow samples from patients with one or more metaphases with a t(3;5)(q21-q25;q31-q35) or a der(5)t(3;5)(q21-q25;q31-q35) previously identified by chromosome analysis. Once unblinded, the results indicate our D-FISH method identified NPM1/MLF1 fusion in 15 of the 26 fully evaluated patient samples. Excluding three samples with a single abnormal t(3;5) metaphase, 15 of 17 (88%) patient samples with a balanced t(3;5) demonstrated NPM1/MLF1 fusion, and 0 of 6 patient samples with a der(5)t(3;5) demonstrated NPM1/MLF1 fusion, suggesting only the balanced form of this 3;5 translocation as observed by karyotype is associated with NPM1/MLF1 fusion. Overall, the FISH results demonstrated five different outcomes (NPM1/MLF1 fusion, MLF1 disruption, MLF1 duplication, NPM1 deletion, and normal), indicating significant molecular heterogeneity when the 3;5 translocation is identified. The development of this sensitive D-FISH strategy for the detection of NPM1/MLF1 fusion adds to the AML FISH testing repertoire and is effective in the detection of this translocation at diagnosis as well as monitoring residual disease in AML patients.
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Umut
authors.initials: U
authors.lastname: Aypar
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Ryan A
authors.initials: RA
authors.lastname: Knudson
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Pearce
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Anne E
authors.initials: AE
authors.lastname: Wiktor
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota. Electronic address: ketterling.rhett@mayo.edu.
authors.forename: Rhett P
authors.initials: RP
authors.lastname: Ketterling
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001854:Bone Marrow Cells / Q000378:metabolism; D018797:Cell Cycle Proteins; D002648:Child; D002893:Chromosomes, Human, Pair 3; D002895:Chromosomes, Human, Pair 5; D015342:DNA Probes; D004268:DNA-Binding Proteins; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods; D015470:Leukemia, Myeloid, Acute / Q000175:diagnosis* / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D009687:Nuclear Proteins / Q000235:genetics*; D000090243:Nucleophosmin; D015514:Oncogene Proteins, Fusion / Q000235:genetics; D011506:Proteins / Q000235:genetics*; D014178:Translocation, Genetic; D055815:Young Adult
chemical_list: D018797:Cell Cycle Proteins; D015342:DNA Probes; D004268:DNA-Binding Proteins; C100852:MLF1 protein, human; C000716967:NPM1 protein, human; D009687:Nuclear Proteins; D015514:Oncogene Proteins, Fusion; D011506:Proteins; D000090243:Nucleophosmin