ABSTRACT
Chronic myelogenous leukemia (CML) is a clonal bone marrow disease characteristics of CML is the presence of the Philadelphia (Ph1) chromosome which involves rearrangement of BCR-ABL genes as a result of reciprocal translocation between chromosomes 9 and 22. Cytogenetic analysis requires sufficient numbers of well-spread metaPhases, but, the recently described fluorescent in situ hybridization (FISH) technique can also be used on poorly spread metaPhases and on interPhase cells to identify the Ph1 chromosome. We have performed cytogenetic as well as FISH analyses using ber-abl probe to determine if 1) the two methods of analyses complement each other, and 2) FISH analysis is more sensitive in detecting the Ph1. Cytogenetic analysis on 23 patients with clinical diagnosis of CML, showed the presence of Ph1 chromosome in 15 patients, whereas 8 patients were Ph1 negative. Specimens from all the 23 patients were independently studied for the presence of Ph1 chromosome using FISH. A reliable correlation was seen between patients with Ph1 chromosome and hybrid signal in all the patients studied. In addition, 3 cytogenetically Ph1 negative patients showed significant numbers of cells with hybrid signal by FISH analysis. ber-abl hybrid was also seen in all the patients with Ph' + ve cells. These results underscore the significance of the FISH technique in identifying the ber/abl hybrids in cells from patients with normal karyotype and, therefore, has tremendous application in detecting minimal residual disease following chemotherapy or monitoring the persistence of leukemic cells after bone marrow transplantation.