Characterization of clonal immunoglobulin heavy (IGH) V-D-J gene rearrangements and the complementarity-determining region in South Indian patients with precursor B-cell acute lymphoblastic leukemia

Abstract

BackgroundThis study characterized clonal IG heavy V-D-J (IGH) gene rearrangements in South Indian patients with precursor B-cell acute lymphoblastic leukemia (precursor B-ALL) and identified age-related predominance in VDJ rearrangements.MethodsIGH rearrangements were studied in 50 precursor B-ALL cases (common ALL=37, pre-B ALL=10, pro-B ALL=3) by polymerase chain reaction (PCR) heteroduplex analysis. Twenty randomly selected clonal IGH rearrangement sequences were analyzed using the IMGT/V-QUEST tool.ResultsClonal IGH rearrangements were detected in 41 (82%) precursor B-ALL cases. Among the IGHV1-IGHV7 subgroups, IGHV3 was used in 25 (50%) cases. Among the IGHD1-IGHD7 genes, IGHD2 and IGHD3 were used in 8 (40%) and 5 (25%) clones, respectively. Among the IGHJ1-IGHJ6 genes, IGHJ6 and IGHJ4 were used in 9 (45%) and 6 (30%) clones, respectively. In 6 out of 20 (30%) IGH rearranged sequences, CDR3 was in frame whereas 14 (70%) had rearranged sequences and CDR3 was out of frame. A somatic mutation in Vmut/Dmut/Jmut was detected in 14 of 20 IGH sequences. On average, Vmut/Dmut/Jmut were detected in 0.1 nt, 1.1 nt, and 0.2 nt, respectively.ConclusionThe IGHV3 gene was frequently used whereas lower frequencies of IGHV5 and IGHV6 and a higher frequency of IGHV4 were detected in children compared with young adults. The IGHD2 and IGHD3 genes were over-represented, and the IGHJ6 gene was predominantly used in precursor-B-ALL. However, the IGH gene rearrangements in precursor-B-ALL did not show any significant age-associated genotype pattern attributed to our population.

Next-generation sequencing for MRD monitoring in B-lineage malignancies: from bench to bedside

“…ALL is considered to originate from pre-B cells, which are aberrantly blocked at the transition to immature B cells. This mechanism explains the unmutated or low-mutated status due to lack of SHM, the high frequency of unproductive IGH rearrangements due to continuously active recombinase enzyme, and the initiation of IGK/IGL rearrangements that go against allelic exclusion rules due to improper in-frame selection [ 40 , 41 , 47 , 59 ]. Clonal evolution can’t be ignored in ALL and likely occurs by continuing rearrangement processes (successive VH to DJH or secondary rearrangements) [ 40 , 41 ] and selection pressure mediated by treatments [ 60 ].…”

“…This mechanism explains the unmutated or low-mutated status due to lack of SHM, the high frequency of unproductive IGH rearrangements due to continuously active recombinase enzyme, and the initiation of IGK/IGL rearrangements that go against allelic exclusion rules due to improper in-frame selection [ 40 , 41 , 47 , 59 ]. Clonal evolution can’t be ignored in ALL and likely occurs by continuing rearrangement processes (successive VH to DJH or secondary rearrangements) [ 40 , 41 ] and selection pressure mediated by treatments [ 60 ]. Measurements of the IG gene repertoire exhibited biased VH usage toward VH3 and VH1 families, most frequently involving the VH6-1, VH1-2, VH3-11, VH3-13, and VH3-15 segments.…”

“…JH4 and JH6 were more frequently selected in JH families. In the Vκ family, Vκ1 and Vκ2 are preferentially used [ 40 , 47 ]. Unfortunately, there is no obvious evidence indicating an association between IG gene characteristics and prognosis, but this conclusion is not yet validated due to the lack of large-scale studies.…”

“…During adaptive immune responses, B cells react to antigenic stimulation and rapidly proliferate, forming clones with the same V(D)J pattern and possible intraclonal diversity at the nucleotide level attributed to SHM. Similarly, after malignant transformation at a certain time point during B cell differentiation triggered by either activation of oncogenes or inactivation of tumor suppressor genes, B-lineage cancer cells carrying the same complete V(D)J or incomplete DJ rearrangement unlimitedly multiply with possible subclone characteristics caused by ongoing SHM or ongoing V(D)J recombination, respectively [40][41][42]. Given that the rearranged IG gene is unique and the quantification of these specific sequences will dramatically increase to a level far beyond the background of the normal IG gene repertoire when malignant cells proliferate, it is convincing and feasible to consider the IG V(D)J rearrangement pattern as an alternative for both clonality assessment of diagnosis and targets of MRD monitoring.…”

“…The deletion-recombination reactions of V(D)J rearrangement, SHM, and CSR require a double-strand break (DSB) at a specific locus, introducing potential aberrant translocation events that can serve as distinguishing signs in fluorescence in situ hybridization or IG-based clonality assessment [43][44][45][46]. Characteristics associated with the abnormal IG repertoire, such as biased V-J usage [40,47], stereotyped CDR3 [48][49][50][51][52], the tendency to mutate frequently [18,45,53] or retain germline configuration [40,54,55], ongoing SHM [56][57][58] or lack of intraclonal diversification [46], were further confirmed in many hematology studies based on the sequencing of IG genes. Detailed information is exhibited in Table 1 and Fig.…”