Quantification of minimal residual disease in children with oligoclonal B-precursor acute lymphoblastic leukemia indicates that the clones that grow out during relapse already have the slowest rate of reduction during induction therapy

Abstract

Antigen receptor gene rearrangements are applied for the PCRbased minimal residual disease (MRD) detection in acute lymphoblastic leukemia (ALL). It is known that ongoing rearrangements result in subclone formation, and that the relapsing subclone(s) can contain antigen receptor rearrangement(s) that differ from the rearrangements found in the major clone(s) at diagnosis. However, the mechanism leading to this so-called clonal evolution is not known, particularly at which time point in the disease the relapsing subclone obtains its (relative) therapy resistance. To obtain insight in clonal evolution, we followed the kinetics of several subclones in three oligoclonal ALL patients during induction therapy. Clone-specific nested PCR for immunoglobulin heavy chain or T cell receptor ␦ gene rearrangements were performed in limiting dilution assays on bone marrow samples taken at diagnosis, at the end of induction therapy and at possible relapse in three children with oligoclonal B-precursor ALL. We demonstrated that in all three patients the subclones were behaving differently in response to therapy. Moreover, in the two patients who relapsed, the clones that grew out during relapse showed the slowest regression or even evoluated during induction therapy and the clones that were not present at relapse showed good response to induction therapy. These results support the hypothesis that at least in some patients already at diagnosis or in the very first weeks, subclones have important differences in respect to resistance. Hence, these data give experimental evidence for the need to develop, during the first months after diagnosis, quantitative PCR assays for at least two different Ig/TCR gene rearrangement targets for every ALL patient. Leukemia (2001) 15, 134-140.

DNA microarrays for comparison of gene expression profiles between diagnosis and relapse in precursor-B acute lymphoblastic leukemia: choice of technique and purification influence the identification of potential diagnostic markers

“…The design of the GeneChips is such that expression of a gene is interrogated by several (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) 25-mer oligonucleotides that span a part of the gene (Figure 2). In addition to these perfect-match oligonucleotides, each 25 mer comes with a negative control oligonucleotide that contains a mismatch at position 13.…”

“…Such emersion of subclones has been shown before using RQ-PCR of the rearranged Ig genes. 13, 14 The single statistically significant downregulated gene WASF1 concerns a member of the Wiskott Aldrich syndrome protein (WASP) gene family that is involved in actin filament reorganization and changes in cell shape. WASP expression is regulated by the small GTPases Rac and cdc42, which are related to Ras.…”

Assessing minimal residual disease (MRD) in leukemia: a changing definition and concept?

“…1,[10][11][12][13] Furthermore, distinct kinetics of reduction of molecular subclones resulting in the selective persistence or evolution of minor clones contribute to the diversity of postinduction disease. 13,14 Observations with qualitative 15,16 or quantitative 11 PCR indicating that molecular residual disease at the end of induction therapy is prognostically not informative must be viewed in the context of both this heterogeneity of postinduction patients with respect to the level of residual disease and the inherent variability of PCR determinations.…”

“…2 Most importantly, in ALL there is the possibility to monitor monoclonality based on immunoglobulin or T cell receptor gene rearrangements, although this approach may harbor its own challenges. 13,43,44 Bone Marrow Transplantation…”

Chromosome 14 copy number-dependent IGH gene rearrangement patterns in high hyperdiploid childhood B-cell precursor ALL: implications for leukemia biology and minimal residual disease analysis

“…5 However, the encountered high frequency of oligoclonal IGH rearrangement patterns at diagnosis together with the instability of the individual rearrangements at relapse has questioned its use as a clonal marker for MRD detection. [6][7][8][9][10][11][12][13][14][15] IGH genes are rearranged in an ordered fashion during lymphoid development starting with a DJ H rearrangement on both alleles. Then, a V H segment is joined to one of the DJ H rearrangements.…”