APPLICATION OF FLUORESCENCE IN-SITU HYBRIDIZATION TO DETECT RESIDUAL LEUKEMIC-CELLS WITH 9-22-TRANSLOCATIONS AND 15-17-TRANSLOCATIONS

We performed fluorescence in situ hybridization (FISH) upon 9;22 and 1 5;17 translocation-positive bone marrow cells to monitor the clinical course of 46 patients with chronic myelocytic leukemia (CML) and nine with acute promyelocytic leukemia (AML M3) who received chemotherapy a nd/or bone marrow transplantation (BMT). M-BCR-ABL and PML-RAR alpha p robes were used to detect translocations of t(9;22) and t(15;17), resp ectively. Signals from CML patients treated with interferon (17 patien ts) or BMT (29 patients) were 0.5-15% positive for the 9;22 translocat ion. Among nine M3 patients who received extensive chemotherapy or BMT , 1-5% were positive for the 15;17 translocation. A highly sensitive F ISH procedure using both translocation probes and a whole chromosome Y probe was established and applied to eight sex-mismatched BMT patient s (seven CML and one AML M3), in which 0.1-0.6% of signals positive fo r the specific translocations were detected. These results suggested t hat interphase FISH is powerful enough to identify minor cell populati ons of 9;22 or 15;17 translocations after therapy, as well as to detec t specific chromosome abnormalities at diagnosis.