M Loos

The major bcr-abl fusion gene is presently seen as the hallmark of chronic myeloid leukemia (CML) and presumably as the cause of its development. Accordingly, long-term disappearance of bcr-abl after intensive therapy is considered to be a probable cure of CML. The nested reverse transcriptase-polymerase chain reaction (RT-PCR) provides a powerful tool for minimal residual CML detection. The RT-PCR was optimized by (1) increasing the amount of total RNA involved in the reverse transcription reaction to correspond to total RNA extracted from 10(8) cells, (2) using a specific abl primer in this reverse reaction, and (3) reamplifying 10% of the RT-PCR product in nested amplification. This optimized RT-PCR permitted us to detect up to 1 copy of RNA bcr-abl synthesised in vitro, mixed with yeast RNA in an equivalent quantity to 10(8) white blood cells (WBCs). Using this highly sensitive RT-PCR during the follow-up of CML patients, a signal was unexpectedly found in healthy controls. Therefore, a systematic study of the possible expression of bcr-abl RNA in the WBCs of healthy adults and children and in umbilical cord blood was undertaken. It showed the presence of bcr-abl transcript in the blood of 22 of 73 healthy adults and in the blood of 1 of 22 children but not in 22 samples of umbilical cord blood.

The major bcr-abl fusion gene is presently seen as the hallmark of chronic myeloid leukemia (CML) and presumably as the cause of its development. Accordingly, long-term disappearance of bcr-abl after intensive therapy is considered to be a probable cure of CML. The nested reverse transcriptase-polymerase chain reaction (RT-PCR) provides a powerful tool for minimal residual CML detection. The RT-PCR was optimized by (1) increasing the amount of total RNA involved in the reverse transcription reaction to correspond to total RNA extracted from 10(8) cells, (2) using a specific abl primer in this reverse reaction, and (3) reamplifying 10% of the RT-PCR product in nested amplification. This optimized RT-PCR permitted us to detect up to 1 copy of RNA bcr-abl synthesised in vitro, mixed with yeast RNA in an equivalent quantity to 10(8) white blood cells (WBCs). Using this highly sensitive RT-PCR during the follow-up of CML patients, a signal was unexpectedly found in healthy controls. Therefore, a systematic study of the possible expression of bcr-abl RNA in the WBCs of healthy adults and children and in umbilical cord blood was undertaken. It showed the presence of bcr-abl transcript in the blood of 22 of 73 healthy adults and in the blood of 1 of 22 children but not in 22 samples of umbilical cord blood.

We have compared the effect of alpha 2-C and gamma recombinant interferons (rIFNs) on normal myeloid progenitors (N-CFU-GM), chronic myeloid leukemia (CML) progenitors (CML-CFU-GM) and leukemic progenitors (L-CFU) of acute non-lymphoblastic leukemia (ANLL) patients. Within 14 days of continuous exposure in culture, a dose-dependent inhibition of CFU-GM was seen for most normal subjects. Resistance to rIFNs was frequent in leukemic patients and even more in acute leukemia than in CML. Stimulation of clonogenic cell growth was seen for a minority of leukemic patients. When only the sensitive cases were considered, no difference in sensitivity was noticed between normal, CML and ANLL patients. A good correlation was observed between the activity or the lack of activity of alpha and gamma rIFNs.