Despite the improvement, approximately 60% of patients with relapsed or refractory (r/r) aggressive B cell lymphoma (B-NHL) do not achieve durable benefit from CAR-T cell therapy. To elucidate factors associated with CAR-T therapy resistance, we conducted high-dimensional analyses of pre- and post-CAR-T cell specimens. In patients with non-durable response, we identified a prognostically relevant lymphoma-associated myeloid-monocytic (LAMM) gene signature. In-depth profiling revealed a distinct CSF1R+CD14+CD68+ LAMM cell population in both human and murine B-NHL that inhibits CAR-T cell function and correlates with poor outcome. Cell-cell inference analysis uncovered that LAMM cells impair CAR-T cell function through a direct LAMM-T cell interaction via the PGE2-EP2/EP4 axis. In an autochthonous lymphoma mouse model, combined anti-CD19 CAR-T cell therapy with CSF1R blockade exhibited synergistic effects and improved survival. These findings provide strong rationale for combining anti-CD19 CAR-T cells with CSF1R inhibitors in treating r/r aggressive B-NHL patients.

Introduction: Chimeric antigen receptor (CAR) T cell therapy has substantially improved the outcome of patients suffering from relapsed and/or refractory (r/r) aggressive B cell lymphoma. However, around 60% of patients do not show long-term remissions after CAR-T cell therapy. Recent studies have indicated a relevant role of the lymphoma microenvironment (LME) in response and resistance to CAR-T cell therapy. However, targeting the LME in aggressive B cell lymphoma to boost CAR-T cell efficacy has not yet been sufficiently explored. We therefore aimed to unravel the immunosuppressive capacity of the LME and its myelo-monocytic cell compartment with the ultimate goal to identify potential therapeutic targets and enhance CAR-T cell response. Methods: To elucidate hallmarks associated with an immunosuppressive LME and CAR-T cell resistance in patients with r/r B cell lymphoma, we applied multi-dimensional analyses to pre- and post-CAR-T cell-treated human lymphoma specimens (n = 41), including bulk RNA sequencing, single-cell RNA sequencing of 47,078 live cells and Imaging Mass Cytometry (IMC). To validate our findings and explore the potential of new therapeutic targets, we utilized ex vivo co-culture experiments, a fully murine CD19 CAR-T cell therapy platform in an immunocompetent, autochthonous DLBCL mouse model and performed bulk RNA sequencing and IMC of diseased spleens. Results: In our cohort of CAR-T cell treated patients (n = 104) durable response, defined as complete remission six months after CAR-T cell therapy, resulted in prolonged progression-free and overall survival. In CAR-T cell non-durable responding lymphoma patients, we identified a prognostically relevant lymphoma-associated myelo-monocytic (LAMM) signature including genes such as CD14, CD68, MARCO, ITGAM, IL1B, IL10 and S100A9. Furthermore, non-durable response was characterized by increased hypoxia and reduced (CD8+) T cell infiltration. In particular, in-depth profiling using single-cell RNA sequencing and IMC revealed a distinct CSF1R+CD14+CD68+ LAMM cell population associated with non-durable response and poor clinical outcome in CAR-T cell-treated patients with r/r B cell lymphoma. Importantly, high LAMM and low CD8+ T cell infiltration prior to CAR-T cell therapy showed a reduced progression-free survival when compared to low LAMM and high CD8+ T cell infiltration in r/r B cell lymphoma samples. Next, in ex vivo co-culture experiments we demonstrated that CSF1R+ LAMM cells strongly inhibit the proliferation and the cytotoxic capacity of CAR-T cells. To elaborate on LAMM-T cell interaction at a molecular level, we performed inference analysis of cell-cell communication in our single-cell RNA sequencing dataset using CellphoneDB which revealed that LAMM cells exert their immunosuppressive function by direct interaction with T cells via prostaglandin E2 (PGE2) and EP2/EP4 receptor signaling. Most strikingly, applying a fully autochthonous DLBCL CAR-T cell mouse model, we demonstrated that the combination of CD19 CAR-T cell therapy with CSF1R blockade switches an immunosuppressive LME into a T cell-enriched LME, which was accompanied by a follicular architecture and blood vessel normalization of diseased spleens indicated by IMC analysis. Finally, we showed that the combination of CSF1R inhibition and CD19 CAR-T cell therapy displayed synergistic treatment effects and prolonged survival with long-lasting, complete remissions. Conclusion: Our multiomic data and preclinical models provide strong evidence that CSF1R+ LAMM cells contribute to CAR-T cell failure in r/r aggressive B cell lymphoma and that CSF1R inhibition synergistically improves CD19 CAR-T cell response, promotes an immunosupportive microenvironment and restores anti-lymphoma immunity. Given that CSF1R inhibitors have already been clinically evaluated and FDA-approved in other malignancies, this therapeutic combination has the potential for rapid clinical translation. Based on our findings, we propose to test the combination of CAR-T cell therapy and CSF1R inhibitors in patients with r/r aggressive B cell lymphoma within prospective clinical trials.

Macrophages in the B cell lymphoma microenvironment represent a functional node in progression and therapeutic response. We assessed metabolic regulation of macrophages in the context of therapeutic antibody-mediated phagocytosis. Pentose phosphate pathway (PPP) inhibition induces increased phagocytic lymphoma cell clearance by macrophages in vitro, in primary human chronic lymphocytic leukemia (CLL) patient co-cultures, and in mouse models. Addition of the PPP inhibitor S3 to antibody therapy achieves significantly prolonged overall survival in an aggressive B cell lymphoma mouse model. PPP inhibition induces metabolic activation and pro-inflammatory polarization of macrophages while it decreases macrophages' support for survival of lymphoma cells empowering anti-lymphoma function. As a mechanism of macrophage repolarization, the link between PPP and immune regulation was identified. PPP inhibition causes decreased glycogen level and subsequent modulation of the immune modulatory uridine diphosphate glucose (UDPG)-Stat1-Irg1-itaconate axis. Thus, we hypothesize the PPP as a key regulator and targetable modulator of macrophage activity in lymphoma to improve efficacy of immunotherapies and prolong survival.

Supplementary Table S1. 782 genes identified by piggyBac transposon mutagensis in HG3 cell line after fludarabine selection Supplementary Table S2. Gene Symbol/Gene Description Supplementary Table S3A. Molecular characteristics of BRAF mutant cases in the Spanish cohort. Supplementary Table S3B. Molecular characteristics of BRAF mutant cases in the UK LRF CLL4 cohort. Supplementary TableS 4. Genes differentially regulated in HG3 cells after fludarabine selection. Supplementary Table S5. Gene Set Name [# Genes (K)] Supplementary Table S6. Distribution of mutations in the BRAF gene in CLL.

Supplementary Material and Methods in Word format

Supplementary Figure S1. schematic illustration of piggyBac transposon and transposase vectors used. PB IR refers to piggyBac inverted repeats. FRT is flippase recognition target. Supplementary Figure S2. Real-time quantitative PCR analysis confirms efficient depletion of BMP2K and DCK. Supplementary Figure S3. TP53 deficient HCT116 cell line exhibits reduced sensitivity to F-ara-A. Supplementary Figure S4. Protein expression following transient transfection of the putative fludarabine resistance genes DCK, NUDCD3, ARID5B and LARS in HCT116 cell line. Supplementary Figure S5. Vemurafinib normalizes the response to F-ara-A in cells expressing V600E mutant BRAF. Supplementary Figure S6. Hierarchical clustering of differentially expressed genes in pools of HG3 cells resistant to fludarabine. Supplementary Figure S7. Increased phosphorylation of ERK in HG3 pool resistant to fludarabine. Supplementary Figure S8. Distribution of mutations in the BRAF gene in CLL.

Targeting the PI3K isoform p110δ against B cell malignancies is at the mainstay of PI3K inhibitor (PI3Ki) development. Therefore, we generated isogenic cell lines, which express wild type or mutant p110δ, for assessing the potency, isoform-selectivity and molecular interactions of various PI3Ki chemotypes. The affinity pocket mutation I777M maintains p110δ activity in the presence of idelalisib, as indicated by intracellular AKT phosphorylation, and rescues cell functions such as p110δ-dependent cell viability. Resistance owing to this substitution consistently affects the potency of p110δ-selective in contrast to most multi-targeted PI3Ki, thus distinguishing usually propeller-shaped and typically flat molecules. Accordingly, molecular dynamics simulations indicate that the I777M substitution disturbs conformational flexibility in the specificity or affinity pockets of p110δ that is necessary for binding idelalisib or ZSTK474, but not copanlisib. In summary, cell-based and molecular exploration provide comparative characterization of currently developed PI3Ki and structural insights for future PI3Ki design.

Upregulation of the proto-oncogene T-cell leukemia/lymphoma 1A (TCL1A) is causally implicated in various B-cell and T-cell malignancies. High-level TCL1A correlates with aggressive disease features and inferior clinical outcomes. However, the molecular and cell biological consequences of, particularly nuclear, TCL1A are not fully elucidated. We observed here in mouse models of subcellular site-specific TCL1A-induced lymphomagenesis that TCL1A exerts a strong transforming impact via nuclear topography. In proteomic screens of TCL1A-bound molecules in chronic lymphocytic leukemia (CLL) cells and B-cell lymphoma lines, we identified regulators of cell cycle and DNA repair pathways as novel TCL1A interactors, particularly enriched under induced DNA damage and mitosis. By functional mapping and in silico modeling, we specifically identified the mitotic checkpoint protein, cell division cycle 20 (CDC20), as a direct TCL1A interactor. According to the regulatory impact of TCL1A on the activity of the CDC20-containing mitotic checkpoint and anaphase-promoting complexes during mitotic progression, TCL1A overexpression accelerated cell cycle transition in B-cell lymphoma lines, impaired apoptotic damage responses in association with pronounced chromosome missegregation, and caused cellular aneuploidy in E mu-TCL1A mice. Among hematopoietic cancers, CDC20 levels seem particularly low in CLL. CDC20 expression negatively correlated with TCL1A and lower expression marked more aggressive and genomically instable disease and cellular phenotypes. Knockdown of Cdc20 in TCL1A-initiated murine CLL promoted aneuploidy and leukemic acceleration. Taken together, we discovered a novel cell cycle-associated effect of TCL1A abrogating controlled cell cycle transition. This adds to our concept of oncogenic TCL1A by targeting genome stability. Overall, we propose that TCL1A acts as a pleiotropic adapter molecule with a synergistic net effect of multiple hijacked pathways.

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Introduction: Adoptive immunotherapies such as chimeric antigen receptor (CAR) T cell therapy have strongly improved the outcome of patients with diffuse large cell lymphoma (DLBCL) that are relapsed or refractory after standard chemo-immunotherapy. However, approx. 50% of patients with DLBCL are not durably responding to CAR T cell therapy. CAR T cell expansion is associated with durable responses. However, the molecular mechanisms that mediate suppression of CAR T cells leading to resistance still remain elusive. Methods: We performed bulk RNA sequencing of DLBCL patients before CAR T cell therapy. We performed gene set enrichment analysis (GSEA) using signatures derived from published genes associated with an immunosuppressive lymphoma microenvironment. To investigate CAR T cell therapy in an immunocompetent autochthonous mouse model we established murine CD19-redirected CAR-T cells that were generated using splenic T cells isolated from mice harbouring a C57BL/6N background. We treated DLBCL derived from PPMBC (PRDM1-KO, Myd88 + BCL2 overexpression, CD19: Cre) mice with this murine CD19 CAR-T cells in combination with an anti-CSF1R targeted antibody compared to controls. Results: We found increased immunosuppressive metabolic characteristics in CD19 CAR T refractory DLBCL patients indicated by increased glycolysis, hypoxia and elevated reactive oxygen species (ROS) in GSEA analysis. This metabolic signature was associated with an enriched monocytic-myeloid cell signature and a lack of expansion of effector T cells in CD19 CAR T refractory DLBCL. CSF1-CSFR1 (CD115) signaling is one major pathway that mediates the differentiation of myeloid derived cells into immunosuppressive MSCs. CD115-positive MSCs are important immune regulators in the tumor microenvironment that mediate inhibition of T cells and induce the proliferation of Tregs. We therefore hypothesize that combined treatment with a CSFR1 inhibitor will enhance CAR T cell expansion and thus improve CAR T cell response. We show that CSF1R blockade shifts the immunosuppressive lymphoma microenvironment into an proinflammatory environment in CD19 CAR T cell treated mice with DLBCL and abrogation of the expansion of lymphoma associated myelo-monocytic suppressor cells (LAMMs). This shift into an immunosupportive lymphoma microenvironment was accompanied with an increase of T cell expansion within the tumor and expansion of CD19-CAR T cells. We next evaluated whether the combination of CD19-CAR T cell therapy with CSF1R inhibition improves therapeutic outcome PPMBC DLBCL mice. Strikingly, we show that CSF1R Inhibition displays synergistic efficacy in combination with CD19 CAR T cell therapy. Conclusions: Our data strongly indicates that CSF1R inhibition improves CD19-CAR T expansion, promotes an immunosupportive microenvironment and could enhance CD19-CAR T cell therapy efficacy in patients with DLBCL. Keywords: Aggressive B-cell non-Hodgkin lymphoma, Cellular therapies, Microenvironment No conflicts of interests pertinent to the abstract.

Genetic alterations in the DNA damage response (DDR) pathway are a frequent mechanism of resistance to chemoimmunotherapy (CIT) in B-cell malignancies. We have previously shown that the synergy of CIT relies on secretory crosstalk elicited by chemotherapy between the tumor cells and macrophages. Here, we show that loss of multiple different members of the DDR pathway inhibits macrophage phagocytic capacity in vitro and in vivo. Particularly, loss of TP53 led to decreased phagocytic capacity ex vivo across multiple B-cell malignancies. We demonstrate via in vivo cyclophosphamide treatment using the Em-TCL1 mouse model that loss of macrophage phagocytic capacity in Tp53-deleted leukemia is driven by a significant downregulation of a phagocytic transcriptomic signature using small conditional RNA sequencing. By analyzing the tumor B-cell proteome, we identified a TP53-specific upregulation of proteins associated with extracellular vesicles (EVs). We abrogated EV biogenesis in tumor B-cells via clustered regularly interspaced short palindromic repeats (CRISPR)-knockout (KO) of RAB27A and confirmed that the EVs from TP53-deleted lymphoma cells were responsible for the reduced phagocytic capacity and the in vivo CIT resistance. Furthermore, we observed that TP53 loss led to an upregulation of both PD-L1 cell surface expression and secretion of EVs by lymphoma cells. Disruption of EV bound PD-L1 by anti-PD-L1 antibodies or PD-L1 CRISPR-KO improved macrophage phagocytic capacity and in vivo therapy response. Thus, we demonstrate enhanced EV release and increased PD-L1 expression in TP53-deficient B-cell lymphomas as novel mechanisms of macrophage function alteration in CIT resistance. This study indicates the use of checkpoint inhibition in the combination treatment of B-cell malignancies with TP53 loss.

Causes of death, in particular deaths due to infection, have not been widely studied in randomised trials in chronic lymphocytic leukaemia. With long-term follow-up (median 13 years) we examined the cause of death in 600/777 patients in the LRF CLL4 trial. Blood samples, taken at randomisation from 499 patients, were available for identifying gene mutations. Infection was a cause of death in 258 patients (43%). Patients dying of infection were more likely than those who died of other causes to have received ≥2 lines of treatment (194/258 [75%] versus 231/342 [68%], P = 0.04) and to have died in the winter months (149/258 [58%] versus 166/342 [49%], P = 0.03), respectively. In patients with mutation data, the factors significantly associated with death from infection versus all other deaths were 11q deletion (47/162 [29%] versus 40/209 [19%], P = 0.03) and mutations of the BRAF, FBXW7, NRAS and XPO1 genes. Death was caused by an infection in 46/67 assessable patients (69%) who had a mutation of one or more of these four genes versus only 129/333 patients (39%) without any of these mutations (odds ratio: 3.46 [95% CI 1.98–6.07] P < 0.0001). Careful management of infection risk, including prophylaxis against infection, may be important in patients who carry these mutations.

The ability of regulatory T (Treg) cells to migrate into inflammatory sites is reduced in autoimmune diseases, including rheumatoid arthritis (RA). The reasons for impaired Treg cell migration remain largely unknown. We performed multiplex human kinase activity arrays to explore possible differences in the post-translational phosphorylation status of kinase related proteins that could account for altered Treg cell migration in RA. Results were verified by migration assays and Western blot analysis of CD4+ T cells from RA patients and from mice with collagen type II induced arthritis. Kinome profiling of CD4+ T cells from RA patients revealed significantly altered post-translational phosphorylation of kinase related proteins, including G-protein-signaling modulator 2 (GPSM2), protein tyrosine kinase 6 (PTK6) and vitronectin precursor (VTNC). These proteins have not been associated with RA until now. We found that GPSM2 expression is reduced in CD4+ T cells from RA patients and is significantly downregulated in experimental autoimmune arthritis following immunization of mice with collagen type II. Interestingly, GPSM2 acts as a promoter of Treg cell migration in healthy individuals. Treatment of RA patients with interleukin-6 receptor (IL-6R) blocking antibodies restores GPSM2 expression, thereby improving Treg cell migration. Our study highlights the potential of multiplex kinase activity arrays as a tool for the identification of RA-related proteins which could serve as targets for novel treatments.

Richter's transformation (RT) is an aggressive lymphoma which occurs upon progression from chronic lymphocytic leukemia (CLL). Transformation has been associated with genetic aberrations in the CLL-phase involving TP53, CDKN2A, MYC, and NOTCH1, however a significant proportion of RT cases lack CLL-phase associated events. Here, we report that high levels of AKT phosphorylation occurs both in high-risk CLL patients harboring TP53 and NOTCH1 mutations as well as in RT patients. Genetic over-activation of Akt in the murine Eµ-TCL1 CLL mouse model resulted in CLL to RT with significantly reduced survival and an aggressive lymphoma phenotype. In the absence of recurrent mutations, we identified a profile of genomic aberrations intermediate between CLL and DLBCL. Multi-omics assessment by phosphoproteomic/proteomic and single-cell transcriptomic profiles of this Akt-induced murine RT revealed a S100-protein-defined subcluster of highly aggressive lymphoma cells, which developed from CLL cells, through activation of Notch via Notch ligand expressed by T cells. Constitutively active Notch1 similarly induced RT of murine CLL. We identify Akt activation as an initiator of CLL transformation towards aggressive lymphoma by inducing Notch signaling between RT cells and microenvironmental T cells.

Despite advances in chronic lymphocytic leukaemia (CLL) treatment, globally chemotherapy remains a central treatment modality, with chemotherapy trials representing an invaluable resource to explore disease-related/genetic features contributing to long-term outcomes. In 499 LRF CLL4 cases, a trial with >12 years follow-up, we employed targeted resequencing of 22 genes, identifying 623 mutations. After background mutation rate correction, 11/22 genes were recurrently mutated at frequencies between 3.6% (NFKBIE) and 24% (SF3B1). Mutations beyond Sanger resolution (<12% VAF) were observed in all genes, with KRAS mutations principally composed of these low VAF variants. Firstly, employing orthogonal approaches to confirm <12% VAF TP53 mutations, we assessed the clinical impact of TP53 clonal architecture. Whilst ≥ 12% VAF TP53mut cases were associated with reduced PFS and OS, we could not demonstrate a difference between <12% VAF TP53 mutations and either wild type or ≥12% VAF TP53mut cases. Secondly, we identified biallelic BIRC3 lesions (mutation and deletion) as an independent marker of inferior PFS and OS. Finally, we observed that mutated MAPK-ERK genes were independent markers of poor OS in multivariate survival analysis. In conclusion, our study supports using targeted resequencing of expanded gene panels to elucidate the prognostic impact of gene mutations.

Targeted inhibition of Bruton’s Tyrosine Kinase (BTK) with ibrutinib and other agents has become important treatment options in chronic lymphocytic leukemia, Waldenström’s Macroglobulinemia, Mantle cell lymphoma, and non-GCB DLBCL. Clinical trials combining small molecule inhibitors with monoclonal antibodies have been initiated at rapid pace, with the biological understanding between their synergistic interactions lagging behind. Here, we have evaluated the synergy between BTK inhibitors and monoclonal antibody therapy via macrophage mediated antibody dependent cellular phagocytosis (ADCP). Initially, we observed increased ADCP with ibrutinib, whilst second generation BTK inhibitors failed to synergistically interact with monoclonal antibody treatment. Kinase activity profiling under BTK inhibition identified significant loss of Janus Kinase 2 (JAK2) only under ibrutinib treatment. We validated this potential off-target effect via JAK inhibition in vitro as well as with CRISPR/Cas9 JAK2−/− experiments in vivo, showing increased ADCP and prolonged survival, respectively. This data supports inhibition of the JAK-STAT (Signal Transducers and Activators of Transcription) signaling pathway in B-cell malignancies in combination with monoclonal antibody therapy to increase macrophage-mediated immune responses.

Summary Chemoimmunotherapy (CIT) is the standard of care in B-cell malignancies. It is relying on synergistic effects of alkylating chemotherapy and monoclonal antibodies via secretory crosstalk with effector macrophages. Here, we observed that loss of p53 function mediates resistance to CIT by suppressing macrophage phagocytic function. Loss of p53 leads to an upregulation of PDL1 and an increased formation of extracellular vesicles (EVs). EVs directly inhibit macrophage phagocytosis by PDL1 surface expression. Suppression of phagocytic function by lymphoma cell-derived EVs could be abrogated by pre-incubation of EVs with anti-PDL1 antibodies, CRISPR-KO of PDL1 and abrogation of EV formation by RAB27A -KO in lymphoma cells. Immune checkpoint inhibition represents a viable strategy to overcome EV-mediated resistance to chemoimmunotherapy in lymphoma. Significance Loss of TP53 mediates cell autonomous resistance to genotoxic chemotherapy, moreover non-cell autonomous effects may cause therapy resistance mediated by the tumor microenvironment. We identify a TP53 -dependent mechanism that mediates resistance to synergistic chemoimmunotherapy by increasing formation of EVs and expression of the PDL1 immune checkpoint. PDL1 on EVs is directly responsible for macrophage suppression, preventing the exertion of the essential effector function of antibody-dependent cellular phagocytosis. This novel mechanism of resistance is in turn targetable by PDL1 checkpoint inhibition. Enhanced EV-release and immune checkpoint expression in lymphoma are novel mechanisms of macrophage modulation in the lymphoma microenvironment. We provide a novel principle of resistance to chemoimmunotherapy (CIT) representing of immediate relevance to treatment of refractory B-cell lymphoma. Highlights Loss of TP53 in B-cell lymphoma induces resistance towards chemoimmunotherapy (CIT) by inhibition of macrophage effector function through PDL1 upregulation Loss of TP53 increases formation of extracellular vesicles (EVs) carrying PDL1 EVs inhibit antibody-mediated cellular phagocytosis (ADCP), a key macrophage effector function in CIT Targeting PDL1 on EVs with immune checkpoint inhibitors overcomes TP53 -mediated resistance to CIT

Chronic lymphocytic leukemia patients with mutated immunoglobulin heavy-chain genes (IGHV-M), particularly those lacking poor-risk genomic lesions, often respond well to chemoimmunotherapy (CIT). DNA methylation profiling can subdivide early-stage patients into naive B-cell-like CLL (n-CLL), memory B-cell-like CLL (m-CLL), and intermediate CLL (i-CLL), with differing times to first treatment and overall survival. However, whether DNA methylation can identify patients destined to respond favorably to CIT has not been ascertained. We classified treatment-naive patients (n = 605) from 3 UK chemo and CIT clinical trials into the 3 epigenetic subgroups, using pyrosequencing and microarray analysis, and performed expansive survival analysis. The n-CLL, i-CLL, and m-CLL signatures were found in 80% (n = 245/305), 17% (53/305), and 2% (7/305) of IGHV-unmutated (IGHV-U) cases, respectively, and in 9%, (19/216), 50% (108/216), and 41% (89/216) of IGHV-M cases, respectively. Multivariate Cox proportional analysis identified m-CLL as an independent prognostic factor for overall survival (hazard ratio [HR], 0.46; 95% confidence interval [CI], 0.24-0.87; P = .018) in CLL4, and for progression-free survival (HR, 0.25; 95% CI, 0.10-0.57; P = .002) in ARCTIC and ADMIRE patients. The analysis of epigenetic subgroups in patients entered into 3 first-line UK CLL trials identifies m-CLL as an independent marker of prolonged survival and may aid in the identification of patients destined to demonstrate prolonged survival after CIT.

Even in the era of the targeted therapies, there remains clinical value in exploring the impact of disease characteristics in chemo-immunotherapy (CIT) trials, namely to identify features that contribute most to long-term outcomes, thereby pinpointing patients destined to benefit from these therapies. One such feature is the CLL DNA methylome, that recapitulates normal B cell maturation, with IGHV mutated (M-CLL) and unmutated CLL (U-CLL) retaining an imprint of the DNA methylation signature of memory (m-CLL) and naive B cells (n-CLL), respectively, with a third intermediate epigenetic subgroup (i-CLL) with borderline mutation status. The pyrosequencing analysis of 5 CpG sites can divide CLL into these three subgroups (Queiros 2015, Leukemia 29:598-605), each with different clinico-biological features.