frequency of bcr-abl fusion transcript in iranian patients with chronic myeloid leukemia

introduction: reverse transcriptase-polymerase chain reaction (rt-pcr) assay is a useful tool for the detection of fusion transcript resulting from specific chromosomal translocation of the leukemia cells. a specific chromosomal abnormality, the philadelphia chromosome (ph), is present in 90% to 95% of cml patients.the aberration results from a reciprocal translocation between chromosome 9 and 22, creating a bcr-abl fusion gene.there are two major forms of the bcr/abl fusion gene,  involving abl exon 2, but including different exons of bcr gene. the transcripts b2a2 or b3a2 code for a p210 protein. another fusion gene leads to the expression of an e1a2 transcript, which codes for a p190 pro-tein. another, less common fusion genes are b3a3 or b2a3 (p203) and e19a2 (p230). the incidence of one or other rearrangement in chronic myeloid leukemia (cml) patients varies in different reported se-ries. in general, fusion transcripts are determined individually, a process which is labor intensive in or-der to detect all major fusion transcripts. methods: this study was designed to determine the frequency of different fusion genes in 75 iranian patients with cml. peripheral blood samples were analyzed by multiplex reverse transcriptase poly-merase chain reaction (rt-pcr) from adult patients to detect all types of bcr-abl transcripts of the t (9:22) and found that all cases were positive for some type of bcr/abl rearrangement. results: most of our patients showed b3a2 fusion gene (62%), while the remaining showed one of the transcripts of b2a2, b3a3, b2a3, e1a2 or coexpression of b3a2 and b2a2. the rate of coexpression of the b3a2 and b2a2 was 5%. conclusion: in contrast to the other reports, we did not see any coexpression of p210/p190. this may reflect either the sensitivity of the detection techniques used or the possibility of genetic differences be-tween the populations studied. coexpression may be due to alternative splicing or to phenotypic varia-tion, with clinical course different from classical cml.