Measurable residual disease does not preclude prolonged progression-free survival in CLL treated with ibrutinib.

E1912 was a randomized phase 3 trial comparing indefinite ibrutinib plus 6 cycles of rituximab (IR) to 6 cycles of fludarabine, cyclophosphamide, and rituximab (FCR) in untreated younger patients with CLL. We describe measurable residual disease (MRD) levels in E1912 over time and correlate them with clinical outcome. Undetectable MRD rates (<1 CLL cell per 104 leukocytes) were 29.1%, 30.3%, 23.4%, and 8.6% at 3, 12, 24, and 36 months for FCR, and significantly lower at 7.9%, 4.2%, and 3.7% at 12, 24, and 36 months for IR, respectively. Undetectable MRD at 3, 12, 24, and 36 months was associated with longer progression-free survival (PFS) in the FCR arm, with hazard ratios (MRD detectable/MRD undetectable) of 4.29 (95% confidence interval [CI], 1.89-9.71), 3.91 (95% CI, 1.39-11.03), 14.12 (95% CI, 1.78-111.73), and not estimable (no events among those with undetectable MRD), respectively. In the IR arm, patients with detectable MRD did not have significantly worse PFS compared with those in whom MRD was undetectable; however, PFS was longer in those with MRD levels <10-1 than in those with MRD levels above this threshold. Our observations provide additional support for the use of MRD as a surrogate end point for PFS in patients receiving FCR. In patients on indefinite ibrutinib-based therapy, PFS did not differ significantly by undetectable MRD status, whereas those with MRD <10-1 tended to have longer PFS, although continuation of ibrutinib would very likely be necessary to maintain treatment efficacy.

Higher-order connections between stereotyped subsets: implications for improved patient classification in CLL.

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.

Clonotypic Light Chain Peptides Identified for Monitoring Minimal Residual Disease in Multiple Myeloma without Bone Marrow Aspiration.

BACKGROUND: Analytically sensitive techniques for measuring minimal residual disease (MRD) in multiple myeloma (MM) currently require invasive and costly bone marrow aspiration. These methods include immunohistochemistry (IHC), flow cytometry, quantitative PCR, and next-generation sequencing. An ideal MM MRD test would be a serum-based test sensitive enough to detect low concentrations of Ig secreted from multifocal lesions. METHODS: Patient serum with abundant M-protein before treatment was separated on a 1-dimensional SDS-PAGE gel, and the Ig light-chain (LC) band was excised, trypsin digested, and analyzed on a Q Exactive mass spectrometer by LC-MS/MS. We used the peptide's abundance and sequence to identify tryptic peptides that mapped to complementary determining regions of Ig LCs. The clonotypic target tryptic peptides were used to monitor MRD in subsequent serum samples with prior affinity enrichment. RESULTS: Sixty-two patients were tested, 20 with no detectable disease by IHC and 42 with no detectable disease by 6-color flow cytometry. A target peptide that could be monitored was identified in 57 patients (91%). Of these 57, detectable disease by LC-MS/MS was found in 52 (91%). CONCLUSIONS: The ability to use LC-MS/MS to measure disease in patients who are negative by bone marrow-based methodologies indicates that a serum-based approach has more analytical sensitivity and may be useful for measuring deeper responses to MM treatment. The method requires no bone marrow aspiration.

Proteomic detection of immunoglobulin light chain variable region peptides from amyloidosis patient biopsies.

Immunoglobulin light chain (LC) amyloidosis (AL) is caused by deposition of clonal LCs produced by an underlying plasma cell neoplasm. The clonotypic LC sequences are unique to each patient, and they cannot be reliably detected by either immunoassays or standard proteomic workflows that target the constant regions of LCs. We addressed this issue by developing a novel sequence template-based workflow to detect LC variable (LCV) region peptides directly from AL amyloid deposits. The workflow was implemented in a CAP/CLIA compliant clinical laboratory dedicated to proteomic subtyping of amyloid deposits extracted from either formalin-fixed paraffin-embedded tissues or subcutaneous fat aspirates. We evaluated the performance of the workflow on a validation cohort of 30 AL patients, whose amyloidogenic clone was identified using a novel proteogenomics method, and 30 controls. The recall and negative predictive values of the workflow, when identifying the gene family of the AL clone, were 93 and 98%, respectively. Application of the workflow on a clinical cohort of 500 AL amyloidosis samples highlighted a bias in the LCV gene families used by the AL clones. We also detected similarity between AL clones deposited in multiple organs of systemic AL patients. In summary, AL proteomic data sets are rich in LCV region peptides of potential clinical significance that are recoverable with advanced bioinformatics.

Monitoring M-proteins in patients with multiple myeloma using heavy-chain variable region clonotypic peptides and LC-MS/MS.

Multiple myeloma is a disease characterized by a clonal expansion of plasma cells that secrete a monoclonal immunoglobulin also referred to as an M-protein. In the clinical laboratory, protein electrophoresis (PEL), immunofixation electrophoresis (IFE), and free light chain nephelometry (FLC) are used to detect, monitor, and quantify an M-protein. Here, we present an alternative method based on monitoring a clonotypic (i.e., clone-specific) peptide from the M-protein heavy chain variable region using LC-MS/MS. Tryptic digests were performed on IgG purified serum from 10 patients with a known IgG M-protein. Digests were analyzed by shotgun LC-MS/MS, and the results were searched against a protein database with the patient specific, heavy chain variable region gene sequence added to the database. In all 10 cases, the protein database search matched multiple clonotypic peptides from each patient's heavy chain variable region. The clonotypic peptides were then used to quantitate the amount of M-protein in patient serum samples using selected reaction monitoring (SRM) on a triple quadrupole mass spectrometer. The response for the clonotypic peptide observed by SRM correlated with the M-protein observed by PEL. In addition, the clonotypic peptide was clearly observed by SRM in samples that were negative by IFE and FLC. Monitoring clonotypic peptides using SRM has the capacity to redefine clinical residual disease because of its superior sensitivity and specificity compared with current analytical methods.

Phenotyping polyclonal kappa and lambda light chain molecular mass distributions in patient serum using mass spectrometry.

We previously described a microLC-ESI-Q-TOF MS method for identifying monoclonal immunoglobulins in serum and then tracking them over time using their accurate molecular mass. Here we demonstrate how the same methodology can be used to identify and characterize polyclonal immunoglobulins in serum. We establish that two molecular mass distributions observed by microLC-ESI-Q-TOF MS are from polyclonal kappa and lambda light chains using a combination of theoretical molecular masses from gene sequence data and the analysis of commercially available purified polyclonal IgG kappa and IgG lambda from normal human serum. A linear regression comparison of kappa/lambda ratios for 74 serum samples (25 hypergammaglobulinemia, 24 hypogammaglobulinemia, 25 normal) determined by microflowLC-ESI-Q-TOF MS and immunonephelometry had a slope of 1.37 and a correlation coefficient of 0.639. In addition to providing kappa/lambda ratios, the same microLC-ESI-Q-TOF MS analysis can determine the molecular mass for oligoclonal light chains observed above the polyclonal background in patient samples. In 2 patients with immune disorders and hypergammaglobulinemia, we observed a skewed polyclonal molecular mass distribution which translated into biased kappa/lambda ratios. Mass spectrometry provides a rapid and simple way to combine the polyclonal kappa/lambda light chain abundance ratios with the identification of dominant monoclonal as well as oligoclonal light chain immunoglobulins. We anticipate that this approach to evaluating immunoglobulin light chains will lead to improved understanding of immune deficiencies, autoimmune diseases, and antibody responses.

Patients with chronic lymphocytic leukaemia and clonal deletion of both 17p13.1 and 11q22.3 have a very poor prognosis.

Detection of a 17p13.1 deletion (loss of TP53) or 11q22.3 deletion (loss of ATM), by fluorescence in situ hybridization (FISH), in chronic lymphocytic leukaemia (CLL) patients is associated with a poorer prognosis. Because TP53 and ATM are integral to the TP53 pathway, we hypothesized that 17p13.1- (17p-) and 11q22.3- (11q-) occurring in the same cell (clonal 17p-/11q-) would confer a worse prognosis than either 17p- or 11q-. We studied 2184 CLL patients with FISH (1995-2012) for the first occurrence of 17p-, 11q-, or clonal 17p-/11q-. Twenty (1%) patients had clonal 17p-/11q-, 158 (7%) had 17p- (including 4 with 17p- and 11q- in separate clones), 247 (11%) had 11q-, and 1759 (81%) had neither 17p- nor 11q-. Eleven of 15 (73%) tested patients with clonal 17p-/11q- had dysfunctional TP53 mutations. Overall survival for clonal 17p-/11q- was significantly shorter (1·9 years) than 17p- (3·1 years, P = 0·04), 11q- (4·8 years, P ≤ 0·0001), or neither 17p- nor 11q- (9·3 years, P ≤ 0·0001). Clonal 17p-/11q- thus conferred significantly worse prognosis, suggesting that loss of at least one copy of both TP53 and ATM causes more aggressive disease. Use of an ATM/TP53 combination FISH probe set could identify these very-high risk patients.

AXL Inhibition Improves the Antitumor Activity of Chimeric Antigen Receptor T Cells.

The receptor tyrosine kinase AXL is a member of the TYRO3, AXL, and proto-oncogene tyrosine-protein kinase MER family and plays pleiotropic roles in cancer progression. AXL is expressed in immunosuppressive cells, which contributes to decreased efficacy of immunotherapy. Therefore, we hypothesized that AXL inhibition could serve as a strategy to overcome resistance to chimeric antigen receptor T (CAR T)-cell therapy. To test this, we determined the impact of AXL inhibition on CD19-targeted CAR T (CART19)-cell functions. Our results demonstrate that T cells and CAR T cells express high levels of AXL. Specifically, higher levels of AXL on activated Th2 CAR T cells and M2-polarized macrophages were observed. AXL inhibition with small molecules or via genetic disruption in T cells demonstrated selective inhibition of Th2 CAR T cells, reduction of Th2 cytokines, reversal of CAR T-cell inhibition, and promotion of CAR T-cell effector functions. AXL inhibition is a novel strategy to enhance CAR T-cell functions through two independent, but complementary, mechanisms: targeting Th2 cells and reversing myeloid-induced CAR T-cell inhibition through selective targeting of M2-polarized macrophages.

Platelet-derived growth factor (PDGF)-PDGF receptor interaction activates bone marrow-derived mesenchymal stromal cells derived from chronic lymphocytic leukemia: implications for an angiogenic switch.

Malignant cells are capable of influencing the microenvironment in a manner that facilitates tumor cell survival. Bidirectional crosstalk between chronic lymphocytic leukemic (CLL) cells and marrow-derived mesenchymal stromal cells (MSCs) activates both cell types. In this study, we observed that the conditioned medium (CM) obtained from CLL cells was able to induce Akt activation in MSC. Subsequent studies investigated the mechanism of MSC activation mediated by CLL-CM. Platelet-derived growth factor receptors (PDGFRs) were selectively activated in MSCs by CLL-CM and found to be critical receptors for CLL-CM-driven MSC proliferation and MSC Akt activation. The known ligands of PDGFR, platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF), were detected in CLL-CM, but PDGF was the predominant ligand involved in the CM-mediated PDGFR activation. Both PDGF and VEGF were found to be elevated in the plasma of CLL patients with a positive association for high-risk factors and more advanced stage. Finally, we demonstrated that PDGF induced MSC VEGF production through a phosphatidylinositol 3-kinase (PI3K)-dependent mechanism. These results show that PDGF-PDGFR signaling influences at least the MSC in the microenvironment of CLL and may play a role in the induction of an angiogenic switch known to be permissive for disease progression.

LEF-1 is a prosurvival factor in chronic lymphocytic leukemia and is expressed in the preleukemic state of monoclonal B-cell lymphocytosis.

The canonical Wnt signaling pathway is pathogenic in a variety of cancers. We previously identified aberrant expression of the Wnt pathway transcription factor and target gene lymphoid enhancer binding factor-1 (LEF1) in chronic lymphocytic leukemia (CLL). This suggested that the Wnt signaling pathway has a role in the biology of CLL. In this study, we performed a Wnt pathway analysis using gene expression profiling and identified aberrant regulation of Wnt pathway target genes, ligands, and signaling members in CLL cells. Furthermore, we identified aberrant protein expression of LEF-1 specifically in CLL but not in normal mature B-cell subsets or after B-cell activation. Using the T cell-specific transcription factor/LEF (TCF/LEF) dual luciferase reporter assay, we demonstrated constitutive Wnt pathway activation in CLL, although the pathway was inactive in normal peripheral B cells. Importantly, LEF-1 knockdown decreased CLL B-cell survival. We also identified LEF-1 expression in CD19(+)/CD5(+) cells obtained from patients with monoclonal B-cell lymphocytosis, suggesting a role for LEF-1 early in CLL leukemogenesis. This study has identified the constitutive activation and prosurvival function of LEF-1 and the Wnt pathway in CLL and uncovered a possible role for these factors in the preleukemic state of monoclonal B-cell lymphocytosis.

Extracellular vesicle proteomic analysis leads to the discovery of HDGF as a new factor in multiple myeloma biology.

Identifying factors secreted by multiple myeloma (MM) cells that may contribute to MM tumor biology and progression is of the utmost importance. In this study, hepatoma-derived growth factor (HDGF) was identified as a protein present in extracellular vesicles (EVs) released from human MM cell lines (HMCLs). Investigation of the role of HDGF in MM cell biology revealed lower proliferation of HMCLs following HDGF knockdown and AKT phosphorylation following the addition of exogenous HDGF. Metabolic analysis demonstrated that HDGF enhances the already high glycolytic levels of HMCLs and significantly lowers mitochondrial respiration, indicating that HDGF may play a role in myeloma cell survival and/or act in a paracrine manner on cells in the bone marrow (BM) tumor microenvironment (ME). Indeed, HDGF polarizes macrophages to an M1-like phenotype and phenotypically alters naïve CD14+ monocytes to resemble myeloid-derived suppressor cells which are functionally suppressive. In summary, HDGF is a novel factor in MM biology and may function to both maintain MM cell viability as well as modify the tumor ME.

Stage-Specific Non-Coding RNA Expression Patterns during In Vitro Human B Cell Differentiation into Antibody Secreting Plasma Cells.

The differentiation of B cells into antibody secreting plasma cells (PCs) is governed by a strict regulatory network that results in expression of specific transcriptomes along the activation continuum. In vitro models yielding significant numbers of PCs phenotypically identical to the in vivo state enable investigation of pathways, metabolomes, and non-coding (ncRNAs) not previously identified. The objective of our study was to characterize ncRNA expression during human B cell activation and differentiation. To achieve this, we used an in vitro system and performed RNA-seq on resting and activated B cells and PCs. Characterization of coding gene transcripts, including immunoglobulin (Ig), validated our system and also demonstrated that memory B cells preferentially differentiated into PCs. Importantly, we identified more than 980 ncRNA transcripts that are differentially expressed across the stages of activation and differentiation, some of which are known to target transcription, proliferation, cytoskeletal, autophagy and proteasome pathways. Interestingly, ncRNAs located within Ig loci may be targeting both Ig and non-Ig-related transcripts. ncRNAs associated with B cell malignancies were also identified. Taken together, this system provides a platform to study the role of specific ncRNAs in B cell differentiation and altered expression of those ncRNAs involved in B cell malignancies.

B cell receptor signaling drives APOBEC3 expression via direct enhancer regulation in chronic lymphocytic leukemia B cells.

Constitutively activated B cell receptor (BCR) signaling is a primary biological feature of chronic lymphocytic leukemia (CLL). The biological events controlled by BCR signaling in CLL are not fully understood and need investigation. Here, by analysis of the chromatin states and gene expression profiles of CLL B cells from patients before and after Bruton's tyrosine kinase inhibitor (BTKi) ibrutinib treatment, we show that BTKi treatment leads to a decreased expression of APOBEC3 family genes by regulating the activity of their enhancers. BTKi treatment reduces enrichment of enhancer marks (H3K4me1 and H3K27ac) and chromatin accessibility at putative APOBEC3 enhancers. CRISPR-Cas9 directed deletion or inhibition of the putative APOBEC3 enhancers leads to reduced APOBEC3 expression. We further find that transcription factor NFATc1 couples BCR signaling with the APOBEC3 enhancer activity to control APOBEC3 expression. We also find that enhancer-regulated APOBEC3 expression contributes to replication stress in malignant B cells. In total we demonstrate a novel mechanism for BTKi suppression of APOBEC3 expression via direct enhancer regulation in an NFATc1-dependent manner, implicating BCR signaling as a potential regulator of leukemic genomic instability.

Immunoglobulin diversity gene usage predicts unfavorable outcome in a subset of chronic lymphocytic leukemia patients.

Survival of patients with B cell chronic lymphocytic leukemia (B-CLL) can be predicted by analysis of mutations in the immunoglobulin heavy chain variable gene (IGHV). Patients without mutations (unmutated [UM]) are at greater risk for disease progression and death than patients with mutations (M). Despite this broad prognostic difference, there remains wide intragroup variation in the clinical outcome of UM patients, especially those with low/intermediate Rai risk disease. We evaluated UM B-CLL patients with low/intermediate Rai risk to determine the relationship between IGHV, IGH diversity (IGHD), and IGH joining (IGHJ) gene usage and time to treatment (TTT). Irrespective of IGHV usage, UM patients whose B-CLL cells expressed the IGHD3-3 gene had a significantly shorter TTT than other UM B-CLL patients, and specifically, use of the IGHD3-3 gene in reading frame 2 (RF2) predicted shorter TTT. As expected, Rai risk was the best single prognostic factor for TTT; however, IGHD usage was also a significant variable for TTT. Therefore, both IGHD gene and IGHD RF usage have prognostic relevance in UM B-CLL patients with low/intermediate Rai risk disease. In addition, these data support the concept that antigen-driven selection of specific Ig receptors plays a role in the clinical course of B-CLL.

Mcl-1 expression predicts progression-free survival in chronic lymphocytic leukemia patients treated with pentostatin, cyclophosphamide, and rituximab.

Myeloid cell leukemia-1 (Mcl-1) is an antiapoptotic member of the Bcl-2 protein family. Increased Mcl-1 expression is associated with failure to achieve remission after treatment with fludarabine and chlorambucil in patients with chronic lymphocytic leukemia (CLL). However, the influence of Mcl-1 expression has not been examined in CLL trials using chemoimmunotherapy. We investigated Mcl-1 protein expression prospectively as part of a phase 2 study evaluating the efficacy of pentostatin, cyclophosphamide, and rituximab in patients with untreated CLL. No significant difference by Mcl-1 expression was noted in pretreatment or response parameters. However, in patients with higher Mcl-1 expression, both minimal residual disease-negative status and progression-free survival was found to be significantly reduced (57% vs 19%, P = .01; 50.8 vs 18.7 months; P = .02; respectively). Mcl-1 expression may therefore be useful in predicting poor response to chemoimmunotherapy. These findings further support pursuing treatment strategies targeting this important antiapoptotic protein. (Because the trials described were conducted before the requirement to register them was implemented, they are not registered in a clinical trial database.).

Biologic and genetic characterization of the novel amyloidogenic lambda light chain-secreting human cell lines, ALMC-1 and ALMC-2.

Primary systemic amyloidosis (AL) is a rare monoclonal plasma cell (PC) disorder characterized by the deposition of misfolded immunoglobulin (Ig) light chains (LC) in vital organs throughout the body. To our knowledge, no cell lines have ever been established from AL patients. Here we describe the establishment of the ALMC-1 and ALMC-2 cell lines from an AL patient. Both cell lines exhibit a PC phenotype and display cytokine-dependent growth. Using a comprehensive genetic approach, we established the genetic relationship between the cell lines and the primary patient cells, and we were also able to identify new genetic changes accompanying tumor progression that may explain the natural history of this patient's disease. Importantly, we demonstrate that free lambda LC secreted by both cell lines contained a beta structure and formed amyloid fibrils. Despite absolute Ig LC variable gene sequence identity, the proteins show differences in amyloid formation kinetics that are abolished by the presence of Na(2)SO(4). The formation of amyloid fibrils from these naturally secreting human LC cell lines is unprecedented. Moreover, these cell lines will provide an invaluable tool to better understand AL, from the combined perspectives of amyloidogenic protein structure and amyloid formation, genetics, and cell biology.

Role of long non-coding RNAs in disease progression of early stage unmutated chronic lymphocytic leukemia.

Predicting disease progression in chronic lymphocytic leukemia (CLL) remains challenging particularly in patients with Rai Stage 0/I disease that have an unmutated immunoglobulin heavy chain variable region (UM IGHV). Even though patients with UM IGHV have a poor prognosis and generally require earlier treatment, not all UM IGHV patients experience more rapid disease progression with some remaining treatment free for many years. This observation suggests biologic characteristics other than known prognostic factors influence disease progression. Alterations in long non-coding RNA (lncRNA) expression levels have been implicated in diagnosis and prognosis of various cancers, however, their role in disease progression of early Rai stage UM CLL is unknown. Here we use microarray analysis to compare lncRNA and mRNA profiles of Rai 0/I UM IGHV patients who progressed in <2 years relative to patients who had not progressed for >5 years. Over 1,300 lncRNAs and 940 mRNAs were differentially expressed (fold change ≥ 2.0; p-value ≤ 0.05). Of interest, the differentially expressed lncRNAs T204050, NR_002947, and uc.436+, have known associated genes that have been linked to CLL. Thus, our study reveals differentially expressed lncRNAs in progressive early stage CLL requiring therapy versus indolent early Rai stage UM CLL. These lncRNAs have the potential to impact relevant biological processes and pathways that influence clinical outcome in CLL.

CD49d expression is an independent predictor of overall survival in patients with chronic lymphocytic leukaemia: a prognostic parameter with therapeutic potential.

In vitro studies have demonstrated that surface expression of CD49d on chronic lymphocytic leukaemia (CLL) B cells facilitates leukaemic cell-stromal interactions by binding to fibronectin. This interaction reduces both spontaneous and drug-induced apoptosis. The present study measured CD49d expression by flow cytometry in a cohort of untreated CLL patients previously accrued to a prospective observational study and evaluated the relationship with overall survival (OS). Among the 158 CLL patients tested, the percentage of leukaemic B cells expressing CD49d ranged from 0 to 100%. When all risk factors were treated as continuous variables, CD49d expression showed moderate correlation with expression of ZAP-70 (r = 0.54; P < 0.0001) and CD38 (r = 0.58; P < 0.0001) but not %IGHV mutation. As a continuous variable, CD49d expression strongly correlated with OS (P < 0.0001). Recursive partitioning analysis suggested the 45% threshold of CD49d expression best predicted OS. Multivariate analysis, controlling for disease stage, ZAP-70, IGHV status and fluorescent in situ hybridization defects identified CD49d as an independent predictor of OS and was a better predictor of clinical outcome than ZAP-70, IGHV, or cytogenetics. This observational cohort study suggests that CLL B-cell expression of CD49d is an easily measurable and independent predictor of OS and CD49d expression in CLL. Importantly, anti-CD49d antibodies are already approved for treatment of other human diseases. Clinical testing of anti-CD49d therapy in CLL appears warranted.

The prognostic significance of cytopenia in chronic lymphocytic leukaemia/small lymphocytic lymphoma.

The development of cytopenia in chronic lymphocytic leukaemia (CLL) patients can predict poor prognosis. All CLL patients seen in the Division of Hematology at Mayo Clinic Rochester from 1 January 1995 to 31 December 2004 (n = 1750) were evaluated for cytopenia, aetiology of cytopenia and clinical outcome. Cytopenia occurred in 423 (24.2%) patients and was attributable to CLL in 303 (17.3%) cases, with 228 (75%) of these having bone marrow (BM) failure and 75 (25%) having autoimmune disease (AID). Survival from onset of cytopenia was significantly better for patients with AID (median 9.1 years) compared to patients with BM failure (median 4.4 years, P < 0.001). Patients with AID diagnosed within 1 year of the diagnosis of CLL (n = 35) had similar survival from diagnosis compared to patients without CLL-related cytopenia (median 9.3 vs. 9.7 years, P = 0.881). Although cytopenia caused by BM failure predicted a poorer prognosis in CLL, cytopenia caused by AID was not an adverse prognostic factor. These findings suggest that patients with cytopenia due to AID cannot be meaningfully classified by the current clinical staging systems. Revisions of the National Cancer Institute Working Group 96 criteria should consider the aetiology of cytopenia in staging CLL patients.