A novel tricolor, dual-fusion fluorescence in situ hybridization method to detect BCR/ABL fusion in cells with t(9;22)(q34;q11.2) associated with deletion of DNA on the derivative chromosome 9 in chronic myelocytic leukemia.
Dual-color, dual-fusion fluorescence in situ hybridization (D-FISH) can accurately detect and quantify cells with BCR/ABL fusion in <1% of 500 nuclei in 80% of patients with chronic myelocytic leukemia (CML) and t(9;22)(q34;q11.2). The remaining patients have one of three forms of atypical D-FISH patterns; these patterns have different sensitivities to detect disease. Neoplastic cells with one ABL, one BCR, and one BCR/ABL fusion are particularly problematic, because normal cells with coincidental overlap have the same pattern. For these patients, the normal cutoff for D-FISH is >23%. We tested a new method that incorporates an aqua-labeled probe for the argininosuccinate synthetase (ASS) gene into the conventional BCR/ABL D-FISH probe set. This tricolor D-FISH (TD-FISH) method takes advantage of the aqua-labeled ASS probe to distinguish between neoplastic and normal cells. We used TD-FISH to study 20 normal specimens and 35 specimens from 20 patients with known loss of both BCR and ABL from the derivative chromosome 9. The results show that TD-FISH effectively discriminates between cells with overlapping BCR and ABL signals from cells with true BCR/ABL fusion and improves the ability to quantify minimal residual disease from >23% to >1% of 500 interphase nuclei.
Smoley
Stephanie A
SA
Division of Laboratory Genetics, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
Brockman
Stephanie R
SR
Paternoster
Sarah F
SF
Meyer
Reid G
RG
Dewald
Gordon W
GW
D002892:Chromosomes, Human, Pair 22; D002899:Chromosomes, Human, Pair 9; D016044:Fusion Proteins, bcr-abl / Q000235:genetics*; D017353:Gene Deletion; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000235:genetics*; D014178:Translocation, Genetic
D016044:Fusion Proteins, bcr-abl