Detection of specific chromosome translocation by interphase FISH method and its clinical appication

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Human leukemic cells had disease-specific chromosome translocations which are t (9 ; 22) in chronic myelocytic leukemia, t (8 ; 21), t (15 ; 17), inv (16), t (3 ; 21) and t (12 ; 21) in acute myelocytic leukemia. We established detection method to identify these translocations on interphase nuclei using fluorescence in situ hybridization (FISH) method. Several cosmid and YAC probes spanning on breakpoint region of each chromosome translocation were used for detecting each translocation. We applied this FISH method for clinical use to make diagnosis and to detect remaining residual leukemic cell after chemotherapy and bone marrow transplantation (BMT). The detection levels were about three to five percent, but in sex mismatched BMT cases the levels were increased to 10^<-3> levels by FISH using mixture probes of translocation and Y chromosome. Comparative study on the detection rates between FISH and conventional G-banding analyzes were revealed that G-banding method could not identify the aberrant cells containing less than 20 % of the cell population. The t (15 ; 17) and monosomy 7 abnormalities were specially difficult to detect. Interphase FISH method was helpful detect these masked chromosome aberrations. Futhermore we developed simultaneous FISH analysis for detecting gene alteration and protein expression. The method was applied to reveal the relationship between protein expressions of BCR-ABL,p53, IRF-1 and t (9 ; 22) and deletions of chromosomes 5 and 17. It was also helpful to know the relationship between TRF-1 telomere protein and telomerase activities and chromosome alterations, apoptosis and gene alteration. The qualitative FISH analysis will be more applicable for pathological study and clinical use in leukemia.