Distinct ongoing Ig heavy chain rearrangement processes in childhood B- precursor acute lymphoblastic leukemia

Abstract

Acute lymphoblastic leukemia (ALL) is thought to arise from the clonal expansion of a single transformed precursor cell. However, an oligoclonal Ig heavy chain (IgH) rearrangement pattern has been observed in 30% of ALL patients and was shown to be the result of ongoing rearrangement events. The extent and nature of these ongoing rearrangement processes in individual patients has so far remained obscure. We performed a detailed analysis of leukemic VHDJH rearrangements in three children with B-precursor ALL at diagnosis and one B-lymphoid blast crisis of a child with Ph+ chronic myeloid leukemia at diagnosis and relapse. The children were selected because they presented with multiple IgH rearrangements on Southern blot analysis. Polymerase chain reaction analysis of leukemic cells from two B-precursor ALL patients showed exclusively two groups of related sequences resulting from VH gene replacement events. Most VH gene replacements involved 3′ located acceptor VH genes. Analysis of cells from the other B-precursor ALL patient showed exclusively related sequences as a result of VH gene joinings to a pre-existing DJH rearrangement. In the B-lymphoid blast crisis, a single germline precursor cell had generated multiple unrelated rearrangements and additional groups of related rearrangements resulting from VH to DJH joinings. Direct proof for the VH to DJH joining mechanism was obtained by amplification of the expected preexisting DJH rearrangements. Our findings suggest that the pattern of ongoing rearrangements in an individual patient reflects the IgH rearrangement status of the precursor cell at the time of malignant transformation. Sequence analysis of VHDJH rearrangements at diagnosis may therefore allow a prediction of the reliability of complementarity determining region 3 probes for the detection of minimal residual disease.

Concurrent presence of inv(14)(q11q32) and t(4;11)(q21;q23) in Pre‐B Acute Lymphoblastic leukemia

“…Although both the v H 3 segment and the V62 segment had retained "cryptic" 3 heptamer sequences (see Fig. 5) that potentially allowed serial rearrangements to occur (Steenbergen et al, 1993), it seems unlikely that either of these two clones evolved from the other. For the inv( 14)(qllq32.3) to evolve into a V62-DS3 rearrangement, a re-inversion of chromosome 14 would be required.…”

VH replacement in rearranged immunoglobulin genes

“…Nadel et al 17 did not detect recombination in pre-B cells transfected with plasmids containing the complete nonamer-spacer-heptamer 'embedded RSS' present in the 3¢ end of several of the mouse V H genes, and concluded that V H replacement must be an infrequent event, unlikely to contribute significantly to receptor editing. However, numerous examples of V H replacement continued to be observed in pre-B-cell lines (endogenous genes and introduced substrates), lymphomas and leukaemias 15,[18][19][20][21][22][23][24][25][26][27][28][29] and in transgenic mice. 16,30,31 The reported Type 1 V H replacements fall into three subtypes.…”

Simplified strategies for minimal residual disease detection in B‐cell precursor acute lymphoblastic leukaemia

“…These AJO methods usually enable the detection of one residual clonal cell in 10 4 -10 6 normal cells (sensitivity level 10 ÿ 4 -10 ÿ 6 ), but are labour intensive and costly, thus limiting their application to large-scale clinical studies. In addition, clonal evolution, as evidenced by relapse with a clone demonstrating a different V-D-J junction, has been described in approximately 10-50% of IgH alleles (Baruchel et al, 1995;Beishuizen et al, 1994;Steenbergen et al, 1993), leading to false negative results with AJO probes. Alternative strategies, based either on the incorporation of 32 P-labelled nucleotides in the PCR step and analysis on high-resolution denaturing PAGE ('fingerprinting'), or the use of 32 P-labelled IgH CDR3 PCR product as a patient-specific probe, avoid the sequencing step and achieve a level of sensitivity of detection of 10 ÿ 3 -10 ÿ 4 Nizet et al, 1993).…”