Detection of Minimal Residual Disease in B-Lineage Leukemia by Immunoglobulin Gene Fingerprinting

Abstract

Immunoglobulin and/or T-cell-receptor gene rearrangement occur in the vast majority of lymphoid malignancies and can be readily detected by molecular genetic approaches [1, 2]. Since an identical immunoglobulin or T-cell-receptor gene rearrangement occurs in all members of a single clone, detection of such rearrangements provides a useful marker of clonality. Until recently, the standard means of demonstrating these clonal gene rearrangements has been analysis of the gene structure by Southern hybridisation. The advent of the polymerase chain reaction (PCR) technology has prompted several groups to develop PCR-based strategies as an alternative rapid and simple means of demonstrating lymphoid clonality [3–6]. These methods can be used to detect clonal populations at a sensitivity comparable to that of Southern blotting (1%–5%) [7]. This level of sensitivity, though useful in assessing clonality, is not sufficient to monitor residual disease following treatment. Several groups have therefore developed highly sensitive methods of detecting clonal populations by initially characterising the clonal rearrangement of interest and generating clonespecific primers of probes which can then be used in subsequent PCR and/or hybridisation steps [8–12]. Though two groups have applied such approaches in detection and quantitation of residual disease in acute lymphoblastic leukemia (ALL) [13, 14], the widespread application of such methods is limited by their laborious and complex technology. Because of the paucity of clinical studies applying these sensitive methods, the frequency of occurrence and clinical relevance of very low levels of residual leukemia detected by molecular methods in remission is not known. However, immunophenotypic studies analysing leukemia-specific combination of surface markers, expressed in over 30% of cases of B-lineage ALL, suggest that detection of residual disease at levels of 0.01% or more is predictive of relapse, although absence of such findings cannot exclude this [15]. The immunoglobulin heavy chain (IgH) gene fingerprinting method is a technically simple PCR-based method which allows discrimination of clonal B-cell populations on the basis of size of their clonal IgH gene rearrangements and has a level of sensitivity comparable to that of surface marker analysis (0.01%–0.1%) [16]. Since the majority of cases of B-lineage ALL are amenable to analysis using this approach, it could potentially provide a means of selecting a group of patients with a high probability of relapse, thereby enabling the effect of therapeutic intervention to be evaluated.KeywordsAcute Lymphoblastic LeukemiaMinimal Residual DiseaseGene RearrangementClonal RearrangementImmunoglobulin Gene RearrangementThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.