Measurement of Immunoglobulin Intraclonal diversification refines the clinical impact of IGHV mutational status in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) cells may bear mutations in IGHV genes, the 2%-cutoff allowing to discriminate two subsets, unmutated (U)- or mutated (M)-CLL, with different clinical course. IGHV genes may also incorporate additional ongoing mutations, a phenomenon known as intraclonal diversification (ID). Here, through an original bioinformatic workflow for NGS data, we used the inverse Simpson Index (iSI) as diversity measure among IGHV sequences to dichotomize cases with different ID levels into ID<sub>high</sub> (iSI ≥ 1.2) vs. ID<sub>low</sub> (iSI < 1.2) both in CLL (n = 983) and in other lymphoproliferative disorders (LPD; n = 127). In CLL, ID<sub>high</sub> cases accounted for 14.6%, overrepresented in M-CLL (P = 0.0028), while higher percentages were documented in GC-derived LPD. In M-CLL (n = 396), ID<sub>high</sub> patients (n = 69) experienced longer time-to-first treatment than ID<sub>low</sub> patients (P = 0.015), and multivariate analyses (n = 299) confirmed ID as independent variable. IGHV gene mutations of ID<sub>high</sub> cases had molecular signatures indicating ongoing activity of the AID)/Polη-dependent machinery; consistently, ID<sub>high</sub> M-CLL expressed higher levels of AID transcripts than ID<sub>low</sub> M-CLL (P = 0.012). In conclusion, we propose a robust NGS protocol to quantitatively evaluate ID in CLL, demonstrating that: i) all CLL patients presented ID although at various degree; ii) high degree of ID has clinical relevance identifying a M-CLL subset with better outcome.

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Journal
Leukemia
Published
2025-06-18
DOI
https://doi.org/10.1038/s41375-025-02650-2
Primary Topic
Chronic Lymphocytic Leukemia Research
Type
article
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article

Measurement of Immunoglobulin Intraclonal diversification refines the clinical impact of IGHV mutational status in chronic lymphocytic leukemia

Paola Varaschin, Giovanni D’Arena, Federico Pozzo, Agostino Tafuri et al.
Leukemia
Chronic Lymphocytic Leukemia Research
article

Measurement of Immunoglobulin Intraclonal diversification refines the clinical impact of IGHV mutational status in chronic lymphocytic leukemia

Paola Varaschin, Giovanni D’Arena, Federico Pozzo, Agostino Tafuri, Robel Papotti, Massimo Gentile, Massimiliano Postorino, Eva Zaina, Massimo Degan, Annalisa Biagi, Tamara Bittolo, Antonella Zucchetto, Robert J. Kreitman, Michele Berton, Pietro Bulian, Luca Laurenti, Filippo Vit, Francesco Di Raimondo, Alberto Zamò, Annalisa Chiarenza, Erika Tissino, Francesca Maria Rossi, Maria Ilaria Del Principe, Andreas Rosenwald, Paola Nanni, Annalisa Gaglio, Marco Rossi, Jacopo Olivieri, Alessandra Braida, Roberta Laureana, Valter Gattei, Evgeny Arons, Ellen Leich, Ilaria Cattarossi, Jerry Polesel, Riccardo Bomben, Francesco Zaja, Andrea Stacchetti
article en

Abstract

Chronic lymphocytic leukemia (CLL) cells may bear mutations in IGHV genes, the 2%-cutoff allowing to discriminate two subsets, unmutated (U)- or mutated (M)-CLL, with different clinical course. IGHV genes may also incorporate additional ongoing mutations, a phenomenon known as intraclonal diversification (ID). Here, through an original bioinformatic workflow for NGS data, we used the inverse Simpson Index (iSI) as diversity measure among IGHV sequences to dichotomize cases with different ID levels into ID<sub>high</sub> (iSI ≥ 1.2) vs. ID<sub>low</sub> (iSI < 1.2) both in CLL (n = 983) and in other lymphoproliferative disorders (LPD; n = 127). In CLL, ID<sub>high</sub> cases accounted for 14.6%, overrepresented in M-CLL (P = 0.0028), while higher percentages were documented in GC-derived LPD. In M-CLL (n = 396), ID<sub>high</sub> patients (n = 69) experienced longer time-to-first treatment than ID<sub>low</sub> patients (P = 0.015), and multivariate analyses (n = 299) confirmed ID as independent variable. IGHV gene mutations of ID<sub>high</sub> cases had molecular signatures indicating ongoing activity of the AID)/Polη-dependent machinery; consistently, ID<sub>high</sub> M-CLL expressed higher levels of AID transcripts than ID<sub>low</sub> M-CLL (P = 0.012). In conclusion, we propose a robust NGS protocol to quantitatively evaluate ID in CLL, demonstrating that: i) all CLL patients presented ID although at various degree; ii) high degree of ID has clinical relevance identifying a M-CLL subset with better outcome.

LeukemiaVol. 39(8)
University of Rome Tor Vergata (IT), University of Trieste (IT), University of Würzburg (DE), Fondazione Roma (IT), Dulbecco Telethon Institute (IT), Ferrarotto Hospital (IT), Presidio Ospedaliero (IT), Azienda Ospedaliera S.Maria (IT), Centro di Riferimento Oncologico (IT), Ospedale Annunziata di Cosenza (IT), Ospedale Santa Maria Goretti (IT), National Cancer Institute (US), Center for Cancer Research (US), Istituti di Ricovero e Cura a Carattere Scientifico (IT), University of Calabria (IT), Sapienza University of Rome (IT)
Ministero della Salute, Associazione Italiana per la Ricerca sul Cancro, Associazione Italiana Contro le Leucemie - Linfomi e Mieloma
Reduced inequalities
Openalex Percentile: Top 80%
Chronic Lymphocytic Leukemia Research
DOIOpen Access PDFOpenAlex
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