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Chronic lymphocytic leukemia (CLL) is characterized by the existence of subsets of patients with (quasi)identical, stereotyped B-cell receptor (BcR) immunoglobulins. Patients in certain major stereotyped subsets often display remarkably consistent clinicobiological profiles, suggesting that the study of BcR immunoglobulin stereotypy in CLL has important implications for understanding disease pathophysiology and refining clinical decision-making. Nevertheless, several issues remain open, especially pertaining to the actual frequency of BcR immunoglobulin stereotypy and major subsets, as well as the existence of higher-order connections between individual subsets. To address these issues, we investigated clonotypic IGHV-IGHD-IGHJ gene rearrangements in a series of 29 856 patients with CLL, by far the largest series worldwide. We report that the stereotyped fraction of CLL peaks at 41% of the entire cohort and that all 19 previously identified major subsets retained their relative size and ranking, while 10 new ones emerged; overall, major stereotyped subsets had a cumulative frequency of 13.5%. Higher-level relationships were evident between subsets, particularly for major stereotyped subsets with unmutated IGHV genes (U-CLL), for which close relations with other subsets, termed “satellites,” were identified. Satellite subsets accounted for 3% of the entire cohort. These results confirm our previous notion that major subsets can be robustly identified and are consistent in relative size, hence representing distinct disease variants amenable to compartmentalized research with the potential of overcoming the pronounced heterogeneity of CLL. Furthermore, the existence of satellite subsets reveals a novel aspect of repertoire restriction with implications for refined molecular classification of CLL. Key Points: • In a series of 29 856 CLL patients, the incidence of BcR stereotypy peaked at 41%. • Higher-order relations exist between stereotyped subsets, particularly for those from U-CLL, for which satellite subsets were identified.

Chronic lymphocytic leukemia (CLL) stereotyped subsets #6 and #8 include cases expressing unmutated B cell receptor immunoglobulin (BcR IG) (U-CLL). Subset #6 (IGHV1-69/IGKV3-20) is less aggressive compared to subset #8 (IGHV4-39/IGKV1(D)-39) which has the highest risk for Richter's transformation among all CLL. The underlying reasons for this divergent clinical behavior are not fully elucidated. To gain insight into this issue, here we focused on epigenomic signatures and their links with gene expression, particularly investigating genome-wide DNA methylation profiles in subsets #6 and #8 as well as other U-CLL cases not expressing stereotyped BcR IG. We found that subset #8 showed a distinctive DNA methylation profile compared to all other U-CLL cases, including subset #6. Integrated analysis of DNA methylation and gene expression revealed significant correlation for several genes, particularly highlighting a relevant role for the TP63 gene which was hypomethylated and overexpressed in subset #8. This observation was validated by quantitative PCR, which also revealed TP63 mRNA overexpression in additional nonsubset U-CLL cases. BcR stimulation had distinct effects on p63 protein expression, particularly leading to induction in subset #8, accompanied by increased CLL cell survival. This pro-survival effect was also supported by siRNA-mediated downregulation of p63 expression resulting in increased apoptosis. In conclusion, we report that DNA methylation profiles may vary even among CLL patients with similar somatic hypermutation status, supporting a compartmentalized approach to dissecting CLL biology. Furthermore, we highlight p63 as a novel prosurvival factor in CLL, thus identifying another piece of the complex puzzle of clinical aggressiveness. What's new? In chronic lymphocytic leukemia (CLL), cases with unmutated immunoglobulin receptors (U-CLL) are generally associated with inferior outcome, albeit still displaying considerable heterogeneity. Might such differences in CLL progression be explained by epigenetics? In this study, the authors found that an unusually aggressive subset of CLLs called subset #8 has a distinctive DNA-methylation profile. They also found that p63 is a novel pro-survival factor for CLL cells. These molecular studies may lead to new prognostic biomarkers, and possibly new therapeutic targets, for CLL.

Chronic lymphocytic leukemia patients with differential somatic hypermutation status of the immunoglobulin heavy variable genes, namely mutated or unmutated, display fundamental clinicobiological differences. Considering this, we assessed prognosis separately within mutated and unmutated chronic lymphocytic leukemia in 3015 patients, hypothesizing that the relative significance of relevant indicators may differ between these two categories. Within Binet-A mutated chronic lymphocytic leukemia patients, besides TP53 abnormalities, trisomy 12 and stereotyped subset #2 membership were equivalently associated with the shortest time-to-first-treatment and a treatment probability at 5- and 10-years after diagnosis of 40% and 55%, respectively; the remaining cases exhibited 5-year and 10-year treatment probability of 12% and 25%, respectively. Within Binet-A unmutated chronic lymphocytic leukemia patients, besides TP53 abnormalities, del(11q) and/or SF3B1 mutations were associated with the shortest time-to-first-trearment (5- and 10-year treatment probability: 78% and 98%, respectively); in the remaining cases, males had a significantly worse prognosis than females. In conclusion, the relative weight of indicators that can accurately risk stratify early-stage chronic lymphocytic leukemia patients differs depending on the somatic hypermutation status of the immunoglobulin heavy variable genes of each patient. This finding highlights the fact that compartmentalized approaches based on immunogenetic features are necessary to refine and tailor prognostication in chronic lymphocytic leukemia.

on behalf of ERIC, the European Research Initiative on CLL; International audience; We report on markedly different frequencies of genetic lesions within subsets of chronic lymphocytic leukemia patients carrying mutated or unmutated stereotyped B-cell receptor immunoglobu-lins in the largest cohort (n=565) studied for this purpose. By combining data on recurrent gene mutations (BIRC3, MYD88, NOTCH1, SF3B1 and TP53) and cytogenetic aberrations, we reveal a subset-biased acquisition of gene mutations. More specifically, the frequency of NOTCH1 mutations was found to be enriched in subsets expressing unmutated immunoglobu-lin genes, i.e. #1, #6, #8 and #59 (22-34%), often in association with trisomy 12, and was significantly different (P

// Nikos Papakonstantinou 1,2,* , Stavroula Ntoufa 1,2,* , Elisavet Chartomatsidou 1 , Konstantia Kotta 1 , Andreas Agathangelidis 3 , Lefki Giassafaki 1 , Tzeni Karamanli 1 , Panagiota Bele 1 , Theodoros Moysiadis 1 , Panagiotis Baliakas 2 , Lesley Ann Sutton 2 , Niki Stavroyianni 4 , Achilles Anagnostopoulos 4 , Antonios M. Makris 1 , Paolo Ghia 3 , Richard Rosenquist 2 and Kostas Stamatopoulos 1,2,4 1 Institute of Applied Biosciences, Center for Research and Technology Hellas, Thessaloniki, Greece 2 Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden 3 Division of Experimental Oncology and Department of Onco-Hematology, IRCCS San Raffaele Scientific Institute and Universita Vita-Salute San Raffaele, Milan, Italy 4 Hematology Department and HCT Unit, G. Papanicolaou Hospital, Thessaloniki, Greece * These authors have contributed equally to this work Correspondence to: Kostas Stamatopoulos, email: // Keywords : CLL, EZH2, apoptosis, proliferation, inhibitors Received : November 09, 2015 Accepted : April 24, 2016 Published : May 14, 2016 Abstract The histone methyltransferase EZH2 induces gene repression through trimethylation of histone H3 at lysine 27 (H3K27me3). EZH2 overexpression has been reported in many types of cancer and associated with poor prognosis. Here we investigated the expression and functionality of EZH2 in chronic lymphocytic leukemia (CLL). Aggressive cases with unmutated IGHV genes (U-CLL) displayed significantly higher EZH2 expression compared to indolent CLL cases with mutated IGHV genes (M-CLL); furthermore, in U-CLL EZH2 expression was upregulated with disease progression. Within U-CLL, EZH2 high cases harbored significantly fewer ( p = 0.033) TP53 gene abnormalities compared to EZH2 low cases. EZH2 high cases displayed high H3K27me3 levels and increased viability suggesting that EZH2 is functional and likely confers a survival advantage to CLL cells. This argument was further supported by siRNA-mediated downmodulation of EZH2 which resulted in increased apoptosis. Notably, at the intraclonal level, cell proliferation was significantly associated with EZH2 expression. Treatment of primary CLL cells with EZH2 inhibitors induced downregulation of H3K27me3 levels leading to increased cell apoptosis. In conclusion, EZH2 is overexpressed in adverse-prognosis CLL and associated with increased cell survival and proliferation. Pharmacologic inhibition of EZH2 catalytic activity promotes apoptosis, highlighting EZH2 as a novel potential therapeutic target for specific subgroups of patients with CLL.