ABSTRACT
A specific chromosomal abnormality, the Philadelphia chromosome, is present in 90 - 95% of patients with chronic myeloid leukemia. The aberration results from a reciprocal translocation of chromosomes 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 transcript b2a2 or b3a2 codes for a p210 protein. Other fusion gene leads to the expression of an e1a2 transcript, which codes for a p190 protein. Other less common fusion genes are b3a3 or b2a3 [p203] and e19a2 [p230]. The incidence of one or other rearrangement in chronic myeloid leukemia patients varies in different reports. In general, fusion transcripts are determined individually, a process which is labor- intensive in order to detect all major fusion transcripts. The objective of this study was to set up a multiplex RT-PCR assay for detection and to determine the frequency of different fusion genes in 75 Iranian patients with chronic myeloid leukemia. Peripheral blood samples were analyzed by multiplex RT-PCR from 75 adult Iranian chronic myeloid leukemia patients to detect different types of BCR-ABL transcripts of the t[9;22]. All patients examined were positive for some type of BCR/ABL rearrangement. The majority of the patients [83%] expressed one of the p210BCR-ABL transcripts [b3a2, 62% and b2a2, 20%], while the remaining showed one of the transcripts of b3a3, b2a3, e1a2 or co-expression of b3a2 and b2a2. The rate of co-expression of the b3a2 and b2a2 was 5%. In contrast to other reports, we did not see any co-expression of p210/p190. Co-expression may be due to alternative splicing or to phenotypic variation, with clinical course different from classic chronic myeloid leukemia