Higher incidence of co-expression of BCR-ABL fusion transcripts in an Eastern Indian population

Abstract

Abstract Background Chronic myeloid leukaemia (CML) is a haematopoietic stem cell disorder, caused by a balanced reciprocal translocation (t(9;22) (q34;q11)) that leads to the formation of BCR (Breakpoint Cluster Region)-ABL (Abelson) fusion transcripts known as Philadelphia (Ph) chromosome. The prevalence of BCR-ABL fusion transcripts in Indian CML population is poorly understood, and few studies have been reported from India. The aim of the present study was to determine the frequencies as well as prognostic effects of the three fusion transcripts, i.e. b2a2, b3a2 and e1a2 in an Indian population. Methods RNA was isolated from total 123 samples, 27 bone marrow (BM) samples and 96 peripheral blood (PB) samples, of CML patient followed by cDNA synthesis. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) was performed using TaqMan® assay (ABI, CA, USA) to monitor BCR-ABL transcript. Results Ph' chromosome was observed in 103 patients whereas it was not detected in 20 cases. qRT-PCR revealed that the b3a2 fusion transcripts were the most common transcript in CML patients (63.41%) while b2a2 fusion transcript was present in 16.26% cases. Co-expression of b3a2 + b2a2 fusion transcript was observed in 0.81% cases whereas co-expression of b3a2 + e1a2 fusion transcript was found in 1.63% cases. There was no correlation observed between b3a2 fusion transcript and platelet count. The fusion transcript b2a2 was observed in relatively younger patients compared to b3a2 fusion transcript. Although this correlation was not statistically significant. Conclusion The co-expression of BCR-ABL fusion transcripts was higher (63.41% aggregate of b3a2) in the present population in contrast with other populations reported. This finding was consistent with the frequency data reported from Sudan.

Keywords

• CML
• Fusion transcripts
• Translocation
• qRT-PCR
• Co-expression
• Philadelphia chromosome