Development of five dual-color, double-fusion fluorescence in situ hybridization assays for the detection of common MLL translocation partners.
Chromosomal rearrangements involving the mixed lineage leukemia (MLL) gene at 11q23 are frequent in adult and childhood acute leukemia and have been associated with an unfavorable prognosis. Recent evidence suggests that MLL gene partners may influence prognosis. Five translocations account for approximately 80% of MLL rearrangements: t(4;11)(q21;q23), AFF1/MLL; t(6;11)(q27;q23), MLLT4/MLL; t(9;11)(p22;q23), MLLT3/MLL; t(11;19)(q23;p13.1), MLL/ELL; and t(11;19)(q23;p13.3), MLL/MLLT1. We have designed dual-color, double-fusion fluorescence in situ hybridization (D-FISH) probe sets to identify these translocations. A blinded study was performed for each probe set using 25 normal bone marrow samples, 25 t(4;11), 20 t(6;11), 20 t(9;11), 18 t(11;19p13.1), and 20 t(11;19p13.3) leukemia specimens as defined by chromosome analysis. The findings demonstrated abnormal D-FISH results for 24 of 25 AFF1/MLL, 19 of 20 MLLT4/MLL, all 20 MLLT3/MLL, all 18 MLL/ELL, and all 20 MLL/MLLT1 samples, confirming the efficacy of these D-FISH assays in detecting these common MLL/partner translocations. Our D-FISH assays were more accurate than chromosome analysis at distinguishing disruption of 19p13.1/ELL from that of 19p13.3/MLLT1. We also demonstrated a statistically significant increase in complex/unbalanced MLL/partner translocations occurring in pediatric patients versus adult patients (P = 0.02). A normal cutoff of 0.6% was established, suggesting an application for these assays in minimal residual disease detection and disease monitoring.
Department of Laboratory Medicine and Pathology, Division of Laboratory Genetics, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
Jeannette G
JG
Keefe
William R
WR
Sukov
Ryan A
RA
Knudson
Lai P
LP
Nguyen
Cynthia
C
Williamson
Jason P
JP
Sinnwell
Rhett P
RP
Ketterling
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001681:Biological Assay / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D002877:Chromosomes, Human / Q000235:genetics; D003116:Color; D020732:Cytogenetic Analysis; D015342:DNA Probes; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D007223:Infant; D007399:Interphase / Q000235:genetics; D008875:Middle Aged; D051788:Myeloid-Lymphoid Leukemia Protein / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics; D015203:Reproducibility of Results; D014178:Translocation, Genetic; D055815:Young Adult
D015342:DNA Probes; D009687:Nuclear Proteins; D051788:Myeloid-Lymphoid Leukemia Protein