Detection of bcr/abl fusion transcripts by semiquantitative multiplex RT-PCR combined with a colormetric assay in Ph positive leukemia

Abstract

We studied the feasibility of the clinical application of a new bcr/abl analysis system, C-TRAK t(9;22), consisting of a multiplex RT-PCR and a colormetric assay. With this system, bcr/abl transcripts could be detected in all of 24 cytogenetic Philadelphia chromosome (Ph) positive leukemia patients and in none of eight Ph negative patients. Multiple bcr/abl transcripts could be detected in three of the 24 Ph positive patients, the fusion of bcr exon 1 to abl exon 2 (e1a2 junction) dominated that of bcr exon 13 to abl exon 2 (b2a2 junction) in two cases and that of bcr exon 14 to abl exon 2 (b3a2 junction) and b2a2 dominated e1a2 in one case. This system was sensitive enough to be able to detect even one bcr/abl transcript-producing cell in 50 000 bcr/abl negative background cells, thus making it suitable for semiquantitative evaluation. Minimal residual disease (MRD) was monitored in one Ph positive leukemia patient who underwent allogenic bone marrow transplantation (allo-BMT). After allo-BMT, a weak positivity of the bcr/abl transcript continued with no clinical relapse; this result was consistent with that of a conventional nested PCR assay using ethidium bromide staining. Including all the procedures for RNA extraction, it took only about 10 h to detect the bcr/abl transcripts. Our findings indicate that this bcr/abl analysis system provides a quick and sensitive method for screening bcr/abl transcripts and possibly for monitoring MRD in Ph positive leukemia patients.