| Research Abstract |
We tried to detect minimal residual disease (MRD) in bone marrow of childhood leukemiain completeremission, for evaluating the effects of therapies, by polymerase chain reaction (PCR) followed by Southern blot analysis using specific primers and probes for complementarity-determiningregion III (CDR III) of the immunoglobulinheavy chain. For obtaining CDR III fragments, PCR was carried out on DNA samples prepared from 6 cases of common ALL with rearrangements of IgH gene at the onset of the disease. After the unique CDR III sequences was determinedby sequencing of the PCR products from 4 cases, specific oligonucleotidesprimers were synthesized for each samples, and examined MRD in marrow samples obtainedin remission by PCR and Southern blot analysis. In 3 out of 4 cases tested, the results of MRD analysis were coincident with their clinicalcourses. However, MRD has been constantly detectedin one case, which showed long-termremission clinically. We speculated it as a falsepositive caused by low-specificity of the probe, because DH region, in this case, was very small size, and any unique mutation was not detected. There was no case of relapse, hence, we have not be able to evaluate usefulness of this method for early detection of relapse. Even though our preliminary studies provide fairy promising results, it should be suggested that there are still problems on rechnicalcomplexity as well as on specificity of CDR III itself in some cases.
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