Multiplex-polymerase chain reaction assay for the detection of prognostically significant translocations in acute...

The presence of specific chromosomal translocations in acute lymphoblastic leukemias (ALL) plays an important role in determining the prognosis of the patients. Our aim is to develop a highly sensitive and specific method to screen simultaneously for the four most frequent translocations in ALL: t(9;22), t(1;19), t(4;11), t(12;21).

Our approach uses a multiplex-polymerase chain reaction (PCR) method, which involves two rounds of PCR using fluorescence-labeled nested primers. The chimeric transcripts resulting from these translocations can be identified by agarose gel electrophoresis or by fluorescence analysis. To validate this method we carried out the analysis in 42 pediatric ALL samples previously studied by cytogenetic and fluorescent in situ hybridization (FISH) techniques.

In all samples with a known translocation detected by cytogenetic or FISH techniques, the same translocation was identified by the multiplex-PCR assay. Moreover, with this method we detected rearrangements in five patients in clinical remission and in two patients at diagnosis for whom karyotypes were normal and rearrangements had not been detected. The application of this multiplex-PCR assay was also useful in cases without cytogenetic results.

These results show that the multiplex-PCR method allows reliable, sensitive and rapid detection of the prognostically significant translocations in ALL. We believe that this assay combined with cytogenetic analysis should be the strategy of choice for the initial diagnostic phase of acute lymphoblastic leukemia, and that it could be used not only at diagnosis but also to follow-up these alterations in remission samples without previous controls.