Immunoglobulin gene sequence analysis in chronic lymphocytic leukemia: the 2022 update of the recommendations by ERIC, the European Research Initiative on CLL

Abstract

The somatic hypermutation (SHM) status of the clonotypic immunoglobulin heavy variable (IGHV) gene is a critical biomarker for assessing the prognosis of patients with chronic lymphocytic leukemia (CLL). Importantly, independent studies have documented that IGHV SHM status is also a predictor of responses to therapy, including both chemoimmunotherapy (CIT) and novel, targeted agents. Moreover, immunogenetic analysis in CLL has revealed that different patients may express (quasi)identical, stereotyped B cell receptor immunoglobulin (BcR IG) and are classified into subsets based on this common feature. Patients in certain stereotyped subsets display consistent biology, clinical presentation, and outcome that are distinct from other patients, even with concordant IGHV gene SHM status. All of the above highlights the relevance of immunogenetic analysis in CLL, which is considered a cornerstone for accurate risk stratification and clinical decision making. Recommendations for robust immunogenetic analysis exist thanks to dedicated efforts by ERIC, the European Research Initiative on CLL, covering all test phases, from the pre-analytical and analytical to the post-analytical, pertaining to the analysis, interpretation, and reporting of the findings. That said, these recommendations apply to Sanger sequencing, which is increasingly being superseded by next generation sequencing (NGS), further underscoring the need for an update. Here, we present an overview of the clinical utility of immunogenetics in CLL and update our analytical recommendations with the aim to assist in the refined management of patients with CLL.

Chronic lymphocytic leukaemia/small lymphocytic lymphoma and mantle cell lymphoma: from early lesions to transformation

“…Large-scale sequencing has revealed 29 major stereotypes with an individual frequency > 0.2%, accounting for 41% of all CLL cases. Subset #8 is associated with increased risk for Richter transformation [20]. Subset #2 includes cases using the IGHV3-21/IGLV3-21 genes and has been associated with poor prognosis, regardless of the SHM mutation status [20].…”

“…Subset #8 is associated with increased risk for Richter transformation [20]. Subset #2 includes cases using the IGHV3-21/IGLV3-21 genes and has been associated with poor prognosis, regardless of the SHM mutation status [20]. Recently, a particular mutation, IGLV3-21 R110 , that induces autonomous IG signalling, has been detected in all stereotype #2 cases, but also in CLL without this BCR configuration.…”

Obinutuzumab plus chlorambucil versus ibrutinib in previously untreated chronic lymphocytic leukemia patients without TP53 disruptions: A real-life CLL campus study

“…Given that somatic hypermutation of the IGHV gene is one of the most important prognostic and predictive markers in CLL ( 24 , 25 , 29 , 30 ), we assessed the impact of the IGHV mutational status in our patients. In U-IGHV patients, the 30-month PFS and TTNT were 72% vs .…”

“…Cytogenetics by FISH ( 20 , 21 ), TP53 mutation ( 22 ), and IGHV mutational status ( 23 , 24 ) were performed in all recruited patients in local accredited laboratories, and their protocols are summarized in the supplementary materials. An IGHV gene sequence homology ≥98% was considered as unmutated (U-IGHV), as opposed to mutated (M-IGHV) ( 25 ). For MRD assessed by flow cytometry, mononuclear cells were marked according to the ERIC protocol ( 26 ) or its update.…”

Immunoglobulin Gene Sequence as an Inherited and Acquired Risk Factor for Chronic Lymphocytic Leukemia

“…Using both DNA sequencing and a novel antibody-based screening approach, our group showed for the first time that IGLV3-21 R110Gexpressing CLL cases have significantly lower OS, TTFS, and progression-free survival (PFS) and thus mostly follow the course of U-CLL, compared with IGLV3-21 R110G negative M-CLL cases [51]. Interestingly, IGLV3-21 R110G -positive cases belong to both U-CLL and M-CLL categories, but their prognosis was independent of an IGHV mutational status as the clinical parameters for IGLV3-21 R110G -positive M-CLL and IGLV3-21 R110G -positive U-CLL were virtually identical, indicating that IGLV3-21 R110G is a standalone prognostic marker [68]. Indeed, many of the IGLV3-21 R110G -positive cases actually possessed the favorable del13q genetic aberration, while the unfavorable del17p or del11q was rarely seen [51].…”