Detection of major bcr-abl gene expression at a very low level in blood cells of some healthy individuals

Abstract

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.

BCR‐ABL positive cells and chronic myeloid leukemia in immune suppressed organ transplant recipients

“…The frequency of 5 ⁄ 100 BCR-ABL positive individuals in the study group as well as the rate of BCR-ABL transcript positivity in our control group are lower than in previous articles that studied exclusively healthy individuals and identified 4 ⁄ 15 and 23 ⁄ 117 transcript carriers, respectively (7,8) (Table 2). The higher rate of BCR-ABL transcripts in these previous observations is primarily linked to technical differences in the PCR methods that were used (7,8). These studies pushed the sensitivity of their PCR protocol by use of higher amounts of template, high numbers of replicates or use of an increased sample volume.…”

“…Although the presence of p210 bcr-abl is a prerequisite for the development of CML, it is unclear if it is exclusively sufficient as well. In previous reports, highly sensitive PCR techniques detected low levels of BCR-ABL transcripts in healthy volunteers, supporting the concept that additional genetic alterations are required for leukemogenesis (7,8). There also is evidence that p210 bcr-abl kinase activity stimulates the generation of reactive oxygen species resulting in enhanced oxidative DNA…”

Leukaemic stem cells

“…The fusion gene can be detected in over 90% of cases by molecular methods and its transcription can be studied by PCR. Recent findings that detectable levels of BCR-ABL transcripts, however, are present in cells from over 30% of normal adults, suggest that formation of the BCR-ABL gene alone may not be the sole causative factor in this malignancy (Biernaux et al, 1995;Bose et al, 1998). This is in accordance with the paradigm of a multihit model of leukaemogenesis.…”

Magnetic Nanoparticles PCR Enzyme‐Linked Gene Assay for Quantitative Detection of BCR/ABL Fusion Gene in Chronic Myelogenous Leukemia

“…The data indicate that BCR/ABL is found in <1% of newly diagnosed AML cases; the fusion gene is also the most frequent karyotypic aberration found in 20-30% of adult ALL patients (43)(44)(45)(46). Low BCR/ABL levels were observed in healthy individuals, but only a small percentage developed CML (47,48).…”