REVERSE TRANSCRIPTION-POLYMERASE CHAIN-REACTION FOR PML-RAR-ALPHA FUSION TRANSCRIPTS IN ACUTE PROMYELOCYTIC LEUKEMIA AND ITS APPLICATION TOMINIMAL RESIDUAL LEUKEMIA DETECTION

Chromosome translocation t(15;17) specifically found in acute promyelo cytic leukemia (APL) results in cleavage in the introns of PML gene on chromosome 15 and in the intron of the retinoic acid receptor alpha ( RARalpha) gene on chromosome 17, creation and expression of PML-RARalp ha and RARalpha-PML fusion genes. Reverse transcription-polymerase cha in reaction (RT-PCR) was applied to detect the PML-RARalpha fusion tra nscripts rapidly in APL patients. The fusion transcripts could be dete cted in all of the 10 APL patients studied. Of the two breakpoints in the PML gene so far reported, seven APL patients had the fusion transc ript compatible with the downstream (3') breakpoint, and the other thr ee APL patients were considered to have the upstream (5') breakpoint. RT-PCR could detect the fusion transcripts from as little as 50 pg bon e marrow RNA, and from as little as 0.5 pg bone marrow RNA with the ne sted PCR. This method was applied to detect minimal residual leukemia cells in an APL patient who had undergone allogeneic bone marrow trans plantation, in whom the RT-PCR could not detect the PML-RARalpha fusio n transcripts at several post-transplant time points. This system coul d be useful to detect minimal residual leukemia cells and accordingly modify the treatment strategy, as well as to make a quick diagnosis wi th a small amount of clinical sample.