The Light Chain IgLV3-21 Defines a New Poor Prognostic Subgroup in Chronic Lymphocytic Leukemia: Results of a Multicenter Study

Abstract

Unmutated (UM) immunoglobulin heavy chain variable region (IgHV) status or IgHV3-21 gene usage is associated with poor prognosis in chronic lymphocytic leukemia (CLL) patients. Interestingly, IgHV3-21 is often co-expressed with light chain IgLV3-21, which is potentially able to trigger cell-autonomous BCR-mediated signaling. However, this light chain has never been characterized independently of the heavy chain IgHV3-21. We performed total RNA sequencing in 32 patients and investigated IgLV3-21 prognostic impact in terms of treatment-free survival (TFS) and overall survival (OS) in 3 other independent cohorts for a total of 813 patients. IgLV3-21 presence was tested by real-time PCR and confirmed by Sanger sequencing. Using total RNA sequencing to characterize 32 patients with high-risk CLL, we found a high frequency (28%) of IgLV3-21 rearrangements. Gene set enrichment analysis revealed that these patients express higher levels of genes responsible for ribosome biogenesis and translation initiation ( < 0.0001) as well as MYC target genes ( = 0.0003). Patients with IgLV3-21 rearrangements displayed a significantly shorter TFS and OS ( < 0.05), particularly those with IgHV mutation. In each of the three independent validation cohorts, we showed that IgLV3-21 rearrangements-similar to UM IgHV status-conferred poor prognosis compared with mutated IgHV ( < 0.0001). Importantly, we confirmed by multivariate analysis that this was independent of IgHV mutational status or subset #2 stereotyped receptor ( < 0.0001). We have demonstrated for the first time that a light chain can affect CLL prognosis and that IgLV3-21 light chain usage defines a new subgroup of CLL patients with poor prognosis. .

IGLV3-21 * 01 is an inherited risk factor for CLL through the acquisition of a single-point mutation enabling autonomous BCR signaling

“…Therefore, the total IGLV3-21 frequency in AC III was only 8.89%, but the IGLV3-21 R110 CLL cases were distributed through M-CLL (3 cases) and UM-CLL (4 cases) classification (SI Appendix, Fig. S4) (18,28). Similarly, different IGHV genes were found to be effectively pairing with the IGLV3-21 R110 LC and only 2 of the 7 IGLV3-21 R110 cases were annotated as conventional subset 2, confirming again that subset 2 represents only a minor subgroup of IGLV3-21 R110 -expressing CLL (SI Appendix, Table S10).…”

“…Fig. 1C and D)(13,18,20). Several other IGHV genes were found to be effectively pairing with the IGLV3-21 LC (SI Appendix,Table S2), indicating that CLL subset 2 represents a minor subgroup of IGLV3-21R110 expressing CLL, while the majority have hitherto not been recognized as an immunobiologically related CLL subset.…”

“…Additionally, CLL subset 2 is also known to express a light chain (LC) of the lambda isotype that utilizes the IGLV3-21 gene. Expression of IGLV3-21 has also been associated with poor prognosis of CLL (18), although no mechanistic explanation of this observation has been provided (14).…”

Chronic lymphocytic leukemia: from molecular pathogenesis to novel therapeutic strategies

“…24 This change is present in 7-18% of CLL and seems responsible for the adverse outcome associated with the use of IGLV3-21 independently of the mutational status of the IGHV. 24,25 Epigenetic studies have shown that, although both CLL subtypes are antigen-experienced, M-CLL keeps a methylation signature of germinal center-experienced cells (memory-like B cells), whereas U-CLL has a pre-germinal center, naïve-like methylation signature .5,26 Of note, these epigenetic studies also identified a third subtype with an intermediate profile made of cases with moderate IGHV mutation levels. All three epigenetic subsets have different usage of IGHV genes, stereotypes, genomic aberrations and clinical outcome ( Table 1).…”

The diagnostic chronic lymphocytic leukaemia genome by nanopore sequencing

“…Our study cohort was recruited from our own CLL database, and was selected by the presence of TP53 mutations and del17p13.1. The 11 samples included both mutated (n=5) and unmutated (n=6) IgHV genes (including three cases with two rearrangements each), seven mutations in TP53 (five missense, one stop gain and one frameshift deletion) and four del17p13.1events (table 1), previously identified through at least one of either short-read whole genome sequencing 23 (WGS), whole transcriptome sequencing 23,24 (WTS), targeted deep-sequencing 25 or Sanger sequencing 24 . Genomic DNA was extracted from peripheral blood samples of the 12 untreated CLL patients using a Qiagen DNA Blood mini kit (Qiagen, Hilden, Germany).…”