B-cell chronic lymphocytic leukemia, a clonal disease of B lymphocytes with receptors that vary in specificity for (auto)antigens

Adenosine 2A Receptor Activation Amplifies Ibrutinib Antiplatelet Effect; Implications in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia patients have an increased bleeding risk with the introduction of Bruton tyrosine kinase (BTK) inhibitors. BTK is a signaling effector downstream of the platelet GPVI receptor. Innate platelet dysfunction in CLL patients and the contribution of the leukemia microenvironment to the anti-platelet effect of BTK inhibitors are still not well defined. Herein, we investigated platelet function in stable, untreated CLL patients in comparison to age-matched healthy subjects as control. Secondly, we proposed a novel mechanism of platelet dysfunction via the adenosinergic pathway during BTK inhibitor therapy. Our data indicate that the nucleotidase that produces adenosine, CD73, was expressed on one-third of B-cells in CLL patients. Inhibition of CD73 improved platelet response to ADP in the blood of CLL patients ex vivo. Using healthy platelets, we show that adenosine 2A (A2A) receptor activation amplifies the anti-platelet effect of ibrutinib (10 nM). Ibrutinib plus an A2A agonist-but not ibrutinib as a single agent-significantly inhibited collagen (10 µg/mL)-induced platelet aggregation. Mechanistically, A2A activation attenuated collagen-mediated inhibition of p-VASP and synergized with ibrutinib to inhibit the phosphorylation of AKT, ERK and SYK kinases. This manuscript highlights the potential role of adenosine generated by the microenvironment in ibrutinib-associated bleeding in CLL patients.

Frequency, variations, and prognostic implications of chromosome 14q32 deletions in chronic lymphocytic leukemia

The clinical implications of deletions within chromosome 14q32 in CLL pathogenesis remain unclear. We examined the frequency of 14q32 deletions among CLL cases by karyotype and FISH, categorized the variation using genomic microarray, and assessed the prognostic impact by time-to-first-treatment (TTFT) analysis. A 14q32 abnormality was detected in 35 % (245/698) of cases, with the majority containing a 5' partial telomeric 14q32 deletion. These deletions within the IGH variable region (35/40) ranged from 236 kb to 1.4 Mb involving FAM30A, ADAM6, LINC00226, and LINC00221. The 214 kb minimum deleted region implicated in CLL pathogenesis encompassed LINC00221. Cases with a 14q32 deletion had a shorter median TTFT compared to cases with a sole deletion/nullisomy 13q, a good prognostic indicator, and longer than cases with a sole deletion of 11q or 17p, conferring an unfavorable prognosis. This investigation underscores the importance of comprehensive testing to apprehend the implications of 14q32 deletions in CLL.

The Traf2DNxBCL2-tg Mouse Model of Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma Recapitulates the Biased IGHV Gene Usage, Stereotypy, and Antigen-Specific HCDR3 Selection of Its Human Counterpart

Chronic lymphocytic leukemia (CLL)/Small lymphocytic lymphoma (SLL) is a heterogeneous disease consisting of at least two separate subtypes, based on the mutation status of the immunoglobulin heavy chain variable gene (IGHV) sequence. Exposure to antigens seems to play a role in malignant transformation and in the selection and expansion of more aggressive CLL clones. Furthermore, a biased usage of particular IGHV gene subgroups and the existence of stereotyped B-cell receptors (BCRs) are distinctive characteristics of human CLL. We have previously described that Traf2DN/BCL2 double-transgenic (tg, ^+/+) mice develop CLL/SLL with high incidence with aging. In this model, TNF-Receptor Associated Factor (TRAF)-2 deficiency cooperates with B cell lymphoma (BCL)-2 in promoting CLL/SLL in mice by specifically enforcing marginal zone (MZ) B cell differentiation and rendering B cells independent of BAFF for survival. In this report, we have performed the sequencing of the IGHV-D-J rearrangements of B cell clones from the Traf2DN/BCL2-tg^+/+ mice with CLL/SLL. The results indicate that these mice develop oligoclonal and monoclonal B cell expansions. Allotransplantation of the oligoclonal populations into immunodeficient mice resulted in the preferential expansion of one of the parental clones. The analysis of the IGHV sequences indicated that 15% were mutated (M) and 85% unmutated (UM). Furthermore, while the Traf2DN/BCL2-tg^-/- (wild-type), ^-/+ (BCL2 single-tg) and ^+/- (Traf2DNDN single-tg) littermates showed the expression of various IGHV gene subgroups, the CLL/SLL expanded clones from the Traf2DN/BCL2-tg^+/+ (double-transgenic) mice showed a more restricted IGHV gene subgroup usage and an overrepresentation of particular IGHV genes. In addition, the HCDR3-encoded protein sequence indicates the existence of stereotyped immunoglobulin (Ig) in the BCRs and strong similarities with BCR recognizing autoantigens and pathogen-associated antigens. Altogether, these results highlight the remarkable similarities between the CLL/SLL developed by the Traf2DN/BCL2-tg^+/+ mice and its human counterpart.

Analysis of the Targets and Glycosylation of Monoclonal IgAs From MGUS and Myeloma Patients

Previous studies showed that monoclonal immunoglobulins G (IgGs) of “monoclonal gammopathy of undetermined significance” (MGUS) and myeloma were hyposialylated, thus presumably pro-inflammatory, and for about half of patients, the target of the monoclonal IgG was either a virus—Epstein–Barr virus (EBV), other herpes viruses, hepatitis C virus (HCV)—or a glucolipid, lysoglucosylceramide (LGL1), suggesting antigen-driven disease in these patients. In the present study, we show that monoclonal IgAs share these characteristics. We collected 35 sera of patients with a monoclonal IgA (6 MGUS, 29 myeloma), and we were able to purify 25 of the 35 monoclonal IgAs (6 MGUS, 19 myeloma). Monoclonal IgAs from MGUS and myeloma patients were significantly less sialylated than IgAs from healthy volunteers. When purified monoclonal IgAs were tested against infectious pathogens and LGL1, five myeloma patients had a monoclonal IgA that specifically recognized viral proteins: the core protein of HCV in one case, EBV nuclear antigen 1 (EBNA-1) in four cases (21.1% of IgA myeloma). Monoclonal IgAs from three myeloma patients reacted against LGL1. In summary, monoclonal IgAs are hyposialylated and as described for IgG myeloma, significant subsets (8/19, or 42%) of patients with IgA myeloma may have viral or self (LGL1) antigen-driven disease.

Origin and Pathogenesis of B Cell Lymphomas

Immunoglobulin (IG) gene remodeling by V(D)J recombination plays a central role in the generation of normal B cells, and somatic hypermutation and class switching of IG genes are key processes during antigen-driven B cell differentiation. However, errors of these processes are involved in the development of B cell lymphomas. IG locus-associated translocations of proto-oncogenes are a hallmark of many B cell malignancies. Additional transforming events include inactivating mutations in various tumor suppressor genes and also latent infection of B cells with viruses, such as Epstein-Barr virus. Many B cell lymphomas require B cell antigen receptor expression, and in several instances, chronic antigenic stimulation plays a role in lymphoma development and/or sustaining tumor growth. Often, survival and proliferation signals provided by other cells in the microenvironment are a further critical factor in lymphoma development and pathophysiology. Many B cell malignancies derive from germinal center B cells, most likely because of the high proliferation rate of these cells and the high activity of mutagenic processes.

Fludarabine-resistance associates with ceramide metabolism and leukemia stem cell development in chronic lymphocytic leukemia

Fludarabine (flu) -containing regimens such as flu, cyclophosphamide and rituximab have been established as one of the standard first line therapy in medically-fit chronic lymphocytic leukemia (CLL) patients. Therefore, flu-refractory (primary flu-insensitivity or flu-caused relapse) remains a major problem causing treatment failure for CLL patients. We isolated the peripheral blood mononuclear cells (PBMCs) from CLL patients and treated with flu to find flu-refractory cases, and established flu-resistant clonal cells to study molecular mechanism of flu-resistance. By comparing parental MEC-2 cells, a human CLL cell line, we found that flu-resistant clonal cells were significantly increased lethal dose 50 of flu concentration, and up-regulated expression of P-glycoprotein, a drug-resistant marker, glucosylceramide synthase (GCS), an enzyme that can convert ceramide to glucosylceramide, and CD34, a leukemia stem cell marker. Overexpression of GCS leads to promptly elimination of cellular ceramide levels and accumulation of glucosylceramide, which reduces apoptosis and promotes survival and proliferation of flu-resistant clonal cells. Furthermore, we demonstrated that the accumulation of glucosylceramide can be blocked by PDMP to restore flu-sensitivity in flu-resistant clonal cells. We also found that elevating glucosylceramide levels in flu-resistant clonal cells was associated with up-regulation of GCS and CD34 expression. Importantly, overexpression of GCS or CD34 was also determined in flu-refractory PBMCs. Our results show that flu-resistance is associated with the alteration of ceramide metabolism and the development of leukemia stem cell-like cells. The flu-resistance can be reversed by GCS inhibition as a novel strategy for overcoming drug resistance.

Chronic Lymphocytic Leukemia: Diagnosis and Treatment

The complexity of the treatment of patients with chronic lymphocytic leukemia has increased substantially over the past several years as a consequence of the advent of novel biological agents such as ibrutinib, idelalisib, and venetoclax, as well as increasingly potent anti-CD20 monoclonal antibodies. In addition, the identification of molecular predictive markers and the introduction of more sensitive and sophisticated techniques to assess minimal residual disease have allowed optimization of the use of chemoimmunotherapy and targeted therapies and may become standard of care in the future. This review summarizes the diagnosis, prognostication, and treatment of patients with chronic lymphocytic leukemia with emphasis on new prognostic and predictive factors and novel treatment strategies.

Molecular control of B-cell homeostasis in health and malignancy

Altered B-cell homeostasis underlies a wide range of pathologies, from cancers to autoimmunity and immunodeficiency. The molecular safeguards against those disorders, which also allow effective immune responses, are therefore particularly critical. Here, we review recent findings detailing the fine control of B-cell homeostasis, during B-cell development, maturation in the periphery and during activation and differentiation into antibody-producing cells.

Ibrutinib inhibits free fatty acid metabolism in chronic lymphocytic leukemia

Unlike normal B-cells, and similar to fat cells, chronic lymphocytic leukemia (CLL) cells aberrantly express lipoprotein lipase (LPL), which contributes to free fatty acids (FFAs) metabolism. Here we show that, in CLL cells, the B-cell receptor (BCR) inhibitor ibrutinib reduced LPL mRNA and protein levels and inhibited FFA metabolism in vitro. Likewise, in CLL cells from ibrutinib-treated patients, FFA metabolism was reduced and eventually stopped. Because ibrutinib disrupts CLL cells' ability to use FFAs for energy production, and because various BCR-dependent cellular functions rely on a continuous supply of chemical energy, ibrutinib interrupts several pathways imperative for cellular function in CLL cells.

Anti-leukemic activity of microRNA-26a in a chronic lymphocytic leukemia mouse model

Dysregulation of microRNAs (miRNAs) plays an important role in the pathogenesis of chronic lymphocytic leukemia (CLL). The Eμ-TCL1 transgenic mouse develops a form of leukemia that is similar to the aggressive type of human B-CLL, and this valuable model has been widely used for testing novel therapeutic approaches. Here, we adopted this model to investigate the potential effects of miR-26a, miR-130an and antimiR-155 in CLL therapy. Improved delivery of miRNA molecules into CLL cells was obtained by developing a novel system based on lipid nanoparticles conjugated with an anti-CD38 monoclonal antibody. This methodology has proven to be highly effective in delivering miRNA molecules into leukemic cells. Short- and long-term experiments showed that miR-26a, miR-130a and anti-miR-155 increased apoptosis after in vitro and in vivo treatment. Of this miRNA panel, miR-26a was the most effective in reducing leukemic cell expansion. Following long-term treatment, apoptosis was readily detectable by analyzing cleavage of PARP and caspase-7. These effects could be directly attributed to miR-26a, as confirmed by significant downregulation of its proven targets, namely cyclin-dependent kinase 6 and Mcl1. The results of this study are relevant to two distinct areas. The first is related to the design of a technical strategy and to the selection of CD38 as a molecular target on CLL cells, both consenting efficient and specific intracellular transfer of miRNA. The original scientific finding inferred from the above approach is that miR-26a can elicit in vivo anti-leukemic activities mediated by increased apoptosis.

FBXO10 deficiency and BTK activation upregulate BCL2 expression in mantle cell lymphoma

Targeting Bruton tyrosine kinase (BTK) by ibrutinib is an effective treatment for patients with relapsed/refractory mantle cell lymphoma (MCL). However, both primary and acquired resistance to ibrutinib have developed in a significant number of these patients. A combinatory strategy targeting multiple oncogenic pathways is critical to enhance the efficacy of ibrutinib. Here, we focus on the BCL2 anti-apoptotic pathway. In a tissue microarray of 62 MCL samples, BCL2 expression positively correlated with BTK expression. Increased levels of BCL2 were shown to be due to a defect in protein degradation because of no or little expression of the E3 ubiquitin ligase FBXO10, as well as transcriptional upregulation through BTK-mediated canonical nuclear factor-κB activation. RNA-seq analysis confirmed that a set of anti-apoptotic genes (for example, BCL2, BCL-XL and DAD1) was downregulated by BTK short hairpin RNA. The downregulated genes also included those that are critical for B-cell growth and proliferation, such as BCL6, MYC, PIK3CA and BAFF-R. Targeting BCL2 by the specific inhibitor ABT-199 synergized with ibrutinib in inhibiting growth of both ibrutinib-sensitive and -resistant cancer cells in vitro and in vivo. These results suggest co-targeting of BTK and BCL2 as a new therapeutic strategy in MCL, especially for patients with primary resistance to ibrutinib.

HIF-1α regulates the interaction of chronic lymphocytic leukemia cells with the tumor microenvironment

Hypoxia-inducible transcription factors (HIFs) regulate a wide array of adaptive responses to hypoxia and are often activated in solid tumors and hematologic malignancies due to intratumoral hypoxia and emerging new layers of regulation. We found that in chronic lymphocytic leukemia (CLL), HIF-1α is a novel regulator of the interaction of CLL cells with protective leukemia microenvironments and, in turn, is regulated by this interaction in a positive feedback loop that promotes leukemia survival and propagation. Through unbiased microarray analysis, we found that in CLL cells, HIF-1α regulates the expression of important chemokine receptors and cell adhesion molecules that control the interaction of leukemic cells with bone marrow and spleen microenvironments. Inactivation of HIF-1α impairs chemotaxis and cell adhesion to stroma, reduces bone marrow and spleen colonization in xenograft and allograft CLL mouse models, and prolongs survival in mice. Of interest, we found that in CLL cells, HIF-1α is transcriptionally regulated after coculture with stromal cells. Furthermore, HIF-1α messenger RNA levels vary significantly within CLL patients and correlate with the expression of HIF-1α target genes, including CXCR4, thus further emphasizing the relevance of HIF-1α expression to CLL pathogenesis.

Targeting cholesterol synthesis increases chemoimmuno-sensitivity in chronic lymphocytic leukemia cells

Background

Cholesterol plays an important role in cancer development, drug resistance and chemoimmuno-sensitivity. Statins, cholesterol lowering drugs, can induce apoptosis, but also negatively interfere with CD-20 and rituximab-mediated activity. Our goal is to identify the alternative targets that could reduce cholesterol levels but do not interfere with CD-20 in chemo immunotherapy of chronic lymphocytic leukemia (CLL).

Methods

MEC-2 cells, a CLL cell line, and the peripheral blood mononuclear cells (PBMCs) from CLL patients were treated with cholesterol lowering agents, and analyzed the effect of these agents on cholesterol levels, CD-20 expression and distribution, and cell viability in the presence or absence of fludarabine, rituximab or their combinations.

Results

We found that MEC-2 cells treated with cholesterol lowering agents (BIBB-515, YM-53601 or TAK-475) reduced 20% of total cellular cholesterol levels, but also significantly promoted CD-20 surface expression. Furthermore, treatment of cells with fludarabine, rituximab or their combinations in the presence of BIBB-515, YM-53601 or TAK-475 enhanced MEC-2 cell chemoimmuno-sensitivity measured by cell viability. More importantly, these cholesterol lowering agents also significantly enhanced chemoimmuno-sensitivity of the PBMCs from CLL patients.

Conclusion

Our data demonstrate that BIBB-515, YM53601 and TAK-475 render chemoimmuno-therapy resistant MEC-2 cells sensitive to chemoimmuno-therapy and enhance CLL cell chemoimmuno-sensitivity without CD-20 epitope presentation or its downstream signaling. These results provide a novel strategy which could be applied to CLL treatment.

The novel kinase inhibitor PRT062070 (Cerdulatinib) demonstrates efficacy in models of autoimmunity and B-cell cancer

The heterogeneity and severity of certain autoimmune diseases and B-cell malignancies warrant simultaneous targeting of multiple disease-relevant signaling pathways. Dual inhibition of spleen tyrosine kinase (SYK) and Janus kinase (JAK) represents such a strategy and may elicit several benefits relative to selective kinase inhibition, such as gaining control over a broader array of disease etiologies, reducing probability of selection for bypass disease mechanisms, and the potential that an overall lower level suppression of individual targets may be sufficient to modulate disease activity. To this end, we provide data on the discovery and preclinical development of PRT062070 [4-(cyclopropylamino)-2-({4-[4-(ethylsulfonyl)piperazin-1-yl]phenyl}amino)pyrimidine-5-carboxamide hydrochloride], an orally active kinase inhibitor that demonstrates activity against SYK and JAK. Cellular assays demonstrated specific inhibitory activity against signaling pathways that use SYK and JAK1/3. Limited inhibition of JAK2 was observed, and PRT062070 did not inhibit phorbol 12-myristate 13-acetate-mediated signaling or activation in B and T cells nor T-cell antigen receptor-mediated signaling in T cells, providing evidence for selectivity of action. Potent antitumor activity was observed in a subset of B-cell lymphoma cell lines. After oral dosing, PRT062070 suppressed inflammation and autoantibody generation in a rat collagen-induced arthritis model and blocked B-cell activation and splenomegaly in a mouse model of chronic B-cell antigen receptor stimulation. PRT062070 is currently under evaluation in a phase I dose escalation study in patients with B-cell leukemia and lymphoma (NCT01994382), with proof-of-concept studies in humans planned to assess therapeutic potential in autoimmune and malignant diseases.

The PI3-kinase delta inhibitor idelalisib (GS-1101) targets integrin-mediated adhesion of chronic lymphocytic leukemia (CLL) cell to endothelial and marrow stromal cells

CLL cell trafficking between blood and tissue compartments is an integral part of the disease process. Idelalisib, a phosphoinositide 3-kinase delta (PI3Kδ) inhibitor causes rapid lymph node shrinkage, along with an increase in lymphocytosis, prior to inducing objective responses in CLL patients. This characteristic activity presumably is due to CLL cell redistribution from tissues into the blood, but the underlying mechanisms are not fully understood. We therefore analyzed idelalisib effects on CLL cell adhesion to endothelial and bone marrow stromal cells (EC, BMSC). We found that idelalisib inhibited CLL cell adhesion to EC and BMSC under static and shear flow conditions. TNFα-induced VCAM-1 (CD106) expression in supporting layers increased CLL cell adhesion and accentuated the inhibitory effect of idelalisib. Co-culture with EC and BMSC also protected CLL from undergoing apoptosis, and this EC- and BMSC-mediated protection was antagonized by idelalisib. Furthermore, we demonstrate that CLL cell adhesion to EC and VLA-4 (CD49d) resulted in the phosphorylation of Akt, which was sensitive to inhibition by idelalisib. These findings demonstrate that idelalisib interferes with integrin-mediated CLL cell adhesion to EC and BMSC, providing a novel mechanism to explain idelalisib-induced redistribution of CLL cells from tissues into the blood.

A role for IRF4 in the development of CLL

Interferon regulatory factor 4 (IRF4) is a critical transcriptional regulator of B-cell development and function. A recent genome-wide single-nucleotide polymorphism (SNP) association study identified IRF4 as a major susceptibility gene in chronic lymphocytic leukemia (CLL). Although the SNPs located in the IRF4 gene were linked to a downregulation of IRF4 in CLL patients, whether a low level of IRF4 is critical for CLL development remains unclear. In rodents, CLL cells are derived from B1 cells whose population is dramatically expanded in immunoglobulin heavy chain Vh11 knock-in mice. We bred a Vh11 knock-in allele into IRF4-deficient mice (IRF4(-/-)Vh11). Here, we report that IRF4(-/-)Vh11 mice develop spontaneous early-onset CLL with 100% penetrance. Further analysis shows that IRF4(-/-)Vh11 CLL cells proliferate predominantly in spleen and express high levels of Mcl-1. IRF4(-/-)Vh11 CLL cells are resistant to apoptosis but reconstitution of IRF4 expression in the IRF4(-/-)Vh11 CLL cells inhibits their survival. Thus, our study demonstrates for the first time a causal relationship between low levels of IRF4 and the development of CLL. Moreover, our findings establish IRF4(-/-)Vh11 mice as a novel mouse model of CLL that not only is valuable for dissecting molecular pathogenesis of CLL but could also be used for therapeutic purposes.

Accelerated development of chronic lymphocytic leukemia in New Zealand Black mice expressing a low level of interferon regulatory factor 4

A recent genome-wide SNP association study identified IRF4 as a major susceptibility gene for chronic lymphocytic leukemia (CLL). Moreover, the SNPs located in the 3' UTR of the IRF4 gene have been linked to a down-regulation of IRF4. However, whether a low level of IRF4 is critical for CLL development remains unclear. New Zealand Black (NZB) mice are a naturally occurring, late-onset mouse model of CLL. To examine the role of a reduced level of IRF4 in CLL development, we generated, through breeding, IRF4 heterozygous mutant mice in the NZB background (NZB IRF4(+/-)). Our results show that CLL development is accelerated dramatically in the NZB IRF4(+/-) mice. The average onset of CLL in NZB mice is 12 months, but CLL cells can be detected in NZB IRF4(+/-) mice at 3 months of age. By 5 months of age, 80% of NZB IRF4(+/-) mice developed CLL. CLL cells are derived from B1 cells in mice. Interestingly, NZB IRF4(+/-) B1 cells exhibit prolonged survival, accelerated self-renewal, and defects in differentiation. Although NZB IRF4(+/-) CLL cells are resistant to apoptosis, high levels of IRF4 inhibit their survival. High levels of IRF4 also reduce the survival of MEC-1 human CLL cells. Our analysis further reveals that high levels of IRF4 suppress Akt activity and can do so without the IRF4 DNA binding domain. Thus, our findings reveal a causal relationship between a low level of IRF4 and the development of CLL and establish IRF4 as a novel regulator in the pathogenesis of CLL.

Enhanced CD21 expression and shedding in chronic lymphatic leukemia: a possible pathomechanism in disease progression

CD21 is a 145-kDa membrane glycoprotein mainly expressed on B cells and follicular dendritic cells, and is involved in B-cell activation, survival and proliferation. CD21 can be cleaved to give soluble CD21 (sCD21), which is constantly shed in healthy persons. We show here that plasma sCD21 levels are higher, while B-cell surface CD21 expression levels are lower in B-cell chronic lymphocytic leukemia (B-CLL) patients, but not in multiple myeloma (MM) patients. High sCD21 levels in the blood are positively correlated to the number of cells with high CD21 surface expression and the relative amount of CD21 expressed on the B cells. B-CLL patients with swollen lymph nodes had higher amounts of CD21 high-expressing B cells, as well as CD21 low-expressing B cells, as compared to B-CLL patients without swollen lymph nodes.

Immunological aspects in chronic lymphocytic leukemia (CLL) development

Chronic lymphocytic leukemia (CLL) is unique among B cell malignancies in that the malignant clones can be featured either somatically mutated or unmutated IGVH genes. CLL cells that express unmutated immunoglobulin variable domains likely underwent final development prior to their entry into the germinal center, whereas those that express mutated variable domains likely transited through the germinal center and then underwent final development. Regardless, the cellular origin of CLL remains unknown. The aim of this review is to summarize immunological aspects involved in this process and to provide insights about the complex biology and pathogenesis of this disease. We propose a mechanistic hypothesis to explain the origin of B-CLL clones into our current picture of normal B cell development. In particular, we suggest that unmutated CLL arises from normal B cells with self-reactivity for apoptotic bodies that have undergone receptor editing, CD5 expression, and anergic processes in the bone marrow. Similarly, mutated CLL would arise from cells that, while acquiring self-reactivity for autoantigens-including apoptotic bodies-in germinal centers, are also still subject to tolerization mechanisms, including receptor editing and anergy. We believe that CLL is a proliferation of B lymphocytes selected during clonal expansion through multiple encounters with (auto)antigens, despite the fact that they differ in their state of activation and maturation. Autoantigens and microbial pathogens activate BCR signaling and promote tolerogenic mechanisms such as receptor editing/revision, anergy, CD5+ expression, and somatic hypermutation in CLL B cells. The result of these tolerogenic mechanisms is the survival of CLL B cell clones with similar surface markers and homogeneous gene expression signatures. We suggest that both immunophenotypic surface markers and homogenous gene expression might represent the evidence of several attempts to re-educate self-reactive B cells.

Aging-associated changes in hematopoiesis and leukemogenesis: what's the connection?

Aging is associated with a marked increase in a number of diseases, including many types of cancer. Due to the complex and multi-factorial nature of both aging and cancer, accurate deciphering of causative links between aging and cancer remains a major challenge. It is generally accepted that initiation and progression of cancers are driven by a process of clonal evolution. In principle, this somatic evolution should follow the same Darwinian logic as evolutionary processes in populations in nature: diverse heritable types arising as a result of mutations are subjected to selection, resulting in expansion of the fittest clones. However, prevalent paradigms focus primarily on mutational aspects in linking aging and cancer. In this review, we will argue that age-related changes in selective pressures are likely to be equally important. We will focus on aging-related changes in the hematopoietic system, where age-associated alterations are relatively well studied, and discuss the impact of these changes on the development of leukemias and other malignancies.

Specific inhibition of spleen tyrosine kinase suppresses leukocyte immune function and inflammation in animal models of rheumatoid arthritis

Based on genetic studies that establish the role of spleen tyrosine kinase (Syk) in immune function, inhibitors of this kinase are being investigated as therapeutic agents for inflammatory diseases. Because genetic studies eliminate both adapter functions and kinase activity of Syk, it is difficult to delineate the effect of kinase inhibition alone as would be the goal with small-molecule kinase inhibitors. We tested the hypothesis that specific pharmacological inhibition of Syk activity retains the immunomodulatory potential of Syk genetic deficiency. We report here on the discovery of (4-(3-(2H-1,2,3-triazol-2-yl)phenylamino)-2-((1R,2S)-2-aminocyclohexylamino) pyrimidine-5-carboxamide acetate (P505-15), a highly specific and potent inhibitor of purified Syk (IC50 1-2 nM). In human whole blood, P505-15 potently inhibited B cell antigen receptor-mediated B cell signaling and activation (IC50 0.27 and 0.28 μM, respectively) and Fcε receptor 1-mediated basophil degranulation (IC50 0.15 μM). Similar levels of ex vivo inhibition were measured after dosing in mice (Syk signaling IC50 0.32 μM). Syk-independent signaling and activation were unaffected at much higher concentrations, demonstrating the specificity of kinase inhibition in cellular systems. Oral administration of P505-15 produced dose-dependent anti-inflammatory activity in two rodent models of rheumatoid arthritis. Statistically significant efficacy was observed at concentrations that specifically suppressed Syk activity by ∼67%. Thus specific Syk inhibition can mimic Syk genetic deficiency to modulate immune function, providing a therapeutic strategy in P505-15 for the treatment of human diseases.

Mutation pattern of paired immunoglobulin heavy and light variable domains in chronic lymphocytic leukemia B cells

B-cell chronic lymphocytic leukemia (CLL) patients display leukemic clones bearing either germline or somatically mutated immunoglobulin heavy variable (IGHV ) genes. Most information on CLL immunoglobulins (Igs), such as the definition of stereotyped B-cell receptors (BCRs), was derived from germline unmutated Igs. In particular, detailed studies on the distribution and nature of mutations in paired heavy- and light-chain domains of CLL clones bearing mutated Igs are lacking. To address the somatic hyper-mutation dynamics of CLL Igs, we analyzed the mutation pattern of paired IGHV-diversity-joining (IGHV-D-J ) and immunoglobulin kappa/lambda variable-joining (IGK/LV-J ) rearrangements of 193 leukemic clones that displayed ≥ 2% mutations in at least one of the two immunoglobulin variable (IGV ) genes (IGHV and/or IGK/LV ). The relationship between the mutation frequency in IGHV and IGK/LV complementarity determining regions (CDRs) and framework regions (FRs) was evaluated by correlation analysis. Replacement (R) mutation frequency within IGK/LV chain CDRs correlated significantly with mutation frequency of paired IGHV CDRs in λ but not κ isotype CLL clones. CDRs of IGKV-J rearrangements displayed a lower percentage of R mutations than IGHVs. The frequency/pattern of mutations in kappa CLL Igs differed also from that in κ-expressing normal B cells described in the literature. Instead, the mutation frequency within the FRs of IGHV and either IGKV or IGLV was correlated. Notably, the amount of diversity introduced by replaced amino acids was comparable between IGHVs and IGKVs. The data indicate a different mutation pattern between κ and λ isotype CLL clones and suggest an antigenic selection that, in κ samples, operates against CDR variation.

Internal standard-based analysis of microarray data2--analysis of functional associations between HVE-genes

In this work we apply the Internal Standard-based analytical approach that we described in an earlier communication and here we demonstrate experimental results on functional associations among the hypervariably-expressed genes (HVE-genes). Our working assumption was that those genetic components, which initiate the disease, involve HVE-genes for which the level of expression is undistinguishable among healthy individuals and individuals with pathology. We show that analysis of the functional associations of the HVE-genes is indeed suitable to revealing disease-specific differences. We show also that another possible exploit of HVE-genes for characterization of pathological alterations is by using multivariate classification methods. This in turn offers important clues on naturally occurring dynamic processes in the organism and is further used for dynamic discrimination of groups of compared samples. We conclude that our approach can uncover principally new collective differences that cannot be discerned by individual gene analysis.

An overview of chronic lymphocytic leukaemia biology

Chronic lymphocytic leukaemia (CLL) is characterised by accumulation of CD5(+) monoclonal B cells in primary and secondary lymphoid tissues. Genetic defects and stimuli originating from the microenvironment concur to the selection and expansion of the malignant clone. Several lines of evidence, including molecular and functional analysis of the monoclonal immunoglobulin, support the hypothesis that stimulation through the B-cell receptor affects life and death of leukaemic cells. The microenvironment also has a critical role in the survival and accumulation of leukaemic cells within lymphoid organs where signals delivered from the surrounding cells are likely crucial in inducing proliferation. Nevertheless, several major biological issues still remain to be solved including regulation of the balance between proliferation and survival of leukaemic cells and the links between emerging gene abnormalities and microenvironment. In this context, mouse models are helpful tools in understanding disease mechanisms and in evaluating the efficacy of novel therapeutic agents.

Ectonucleotidases as regulators of purinergic signaling in thrombosis, inflammation, and immunity

Evolving studies in models of transplant rejection, inflammatory bowel disease, and cancer, among others, have implicated purinergic signaling in clinical manifestations of vascular injury and thrombophilia, inflammation, and immune disturbance. Within the vasculature, spatial and temporal expression of CD39 nucleoside triphosphate diphosphohydrolase (NTPDase) family members together with CD73 ecto-5'-nucleotidase control platelet activation, thrombus size, and stability. This is achieved by closely regulated phosphohydrolytic activities to scavenge extracellular nucleotides, maintain P2-receptor integrity, and coordinate adenosinergic signaling responses. The CD38/CD157 family of extracellular NADases degrades NAD(+) and generates Ca(2+)-active metabolites, including cyclic ADP ribose and ADP ribose. These mediators regulate leukocyte adhesion and chemotaxis. These mechanisms are crucial in vascular homeostasis, hemostasis, thrombogenesis, and during inflammation. There has been recent interest in ectonucleotidase expression by immune cells. CD39 expression identifies Langerhans-type dendritic cells and efficiently distinguishes T regulatory cells from other resting or activated T cells. CD39, together with CD73 in mice, serves as an integral component of the suppressive machinery of T cells. Purinergic responses also impact generation of T helper-type 17 cells. Further, CD38 and changes in NAD(+) availability modulate ADP ribosylation of the cytolytic P2X7 receptor that deletes T regulatory cells. Expression of CD39, CD73, and CD38 ectonucleotidases on either endothelial or immune cells allows for homeostatic integration and control of vascular inflammatory and immune cell reactions at sites of injury. Ongoing development of therapeutic strategies targeting these and other ectonucleotidases offers promise for the management of vascular thrombosis, disordered inflammation, and aberrant immune reactivity.

Stereotypical chronic lymphocytic leukemia B-cell receptors recognize survival promoting antigens on stromal cells

Chronic lymphocytic leukemia (CLL) is the most common leukemia in the Western world. Survival of CLL cells depends on their close contact with stromal cells in lymphatic tissues, bone marrow and blood. This microenvironmental regulation of CLL cell survival involves the stromal secretion of chemo- and cytokines as well as the expression of adhesion molecules. Since CLL survival may also be driven by antigenic stimulation through the B-cell antigen receptor (BCR), we explored the hypothesis that these processes may be linked to each other. We tested if stromal cells could serve as an antigen reservoir for CLL cells, thus promoting CLL cell survival by stimulation through the BCR. As a proof of principle, we found that two CLL BCRs with a common stereotyped heavy chain complementarity-determining region 3 (previously characterized as “subset 1”) recognize antigens highly expressed in stromal cells – vimentin and calreticulin. Both antigens are well-documented targets of autoantibodies in autoimmune disorders. We demonstrated that vimentin is displayed on the surface of viable stromal cells and that it is present and bound by the stereotyped CLL BCR in CLL-stroma co-culture supernatant. Blocking the vimentin antigen by recombinant soluble CLL BCR under CLL-stromal cell co-culture conditions reduces stroma-mediated anti-apoptotic effects by 20–45%. We therefore conclude that CLL BCR stimulation by stroma-derived antigens can contribute to the protective effect that the stroma exerts on CLL cells. This finding sheds a new light on the understanding of the pathobiology of this so far mostly incurable disease.

Cellular origin(s) of chronic lymphocytic leukemia: cautionary notes and additional considerations and possibilities

Several cell types have been suggested as giving rise to chronic lymphocytic leukemia (CLL), and these suggestions have reflected the sophistication of technology available at the time. Although there is no consensus as to the normal cellular counterpart(s) in the disease, an antigen-experienced B lymphocyte appears required based on surface membrane phenotypes and gene expression profiles. However, what is still unclear is whether a single or multiple normal precursors were stimulated to evolve into CLL and at what stage(s) this occurred. A unifying, parsimonious theory is that CLL clones with either mutated or unmutated IGHVs derive from marginal zone B cells. However, evidence for remarkably similar B-cell receptor amino acid sequence and striking differences in polyantigen and autoantigen-binding activity, found in some but not all CLL clones, challenge a single-cell derivation for CLL. In this Perspective, we summarize data regarding normal counterparts of CLL cells and suggest that a multistep process of leukemogenesis is important to consider when assigning a cellular origin for this disease. Finally, although available data do not definitively identify the cell(s) of origin, we offer possibilities for single- and multiple-cell origin models as straw men that can be improved on and hopefully lead to final answers to this puzzle.

How the microenvironment shapes chronic lymphocytic leukemia: the cytoskeleton connection

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation in primary and secondary lymphoid tissues of CD5+ B cells that have the same B cell receptor (BCR) rearrangement. Genetic alterations and different stimuli originating from the microenvironment cooperate in the selection and expansion of the malignant clone. Molecular and functional analyses suggest that stimulation through the BCR affects the destiny of leukemic cells in terms of life or death. Microenvironmental signals are crucial for this process, inducing proliferation and leading to the survival and accumulation of leukemic cells within lymphoid organs. Nevertheless, a number of major biological issues still remain to be solved, including the relationships between cell proliferation and cell accumulation within lymphoid organs as well as the mechanisms that regulate CLL cell migration and recirculation between peripheral blood and lymphoid tissues. We focused on the role played by the cytoskeleton, given its relevance in controlling cellular shape, mobility, and homing. We hypothesize that hematopoietic cell-specific Lyn substrate 1 (HS1), a putative prognostic marker in CLL that interacts with distinct cytoskeleton adapters in leukemic B-lymphocytes, could regulate the CLL cell cytoskeleton.

CLL-like monoclonal B-cell lymphocytosis: are we all bound to have it?

CLL-like monoclonal B-cell lymphocytosis (MBL) shares a unique immunophenotype with chronic lymphocytic leukemia (CLL), and represents the vast majority of clonal B-cell expansions found in the peripheral blood of otherwise healthy subjects. Along with the improvement of laboratory techniques and the widespread availability of multiparameter flow cytometry, the finding of tiny aberrant B-cell populations became more frequent, prompting the need for clinical and biological definition of the nature of this condition and its relationship with leukemia development. MBL seems to be a melting-pot containing several entities, identical in terms of phenotype but with extremely different risks of leukemia development (from low to none) that seem to correlate with the number of B lymphocytes. CLL-like MBL observed in the clinical setting ("Clinical MBL"), usually being characterized by lymphocytosis, demonstrated a sizeable, even if low (1.1-1.4% per year), risk of leukemic progression, but represents a minority of all MBL cases. The vast majority of CLL-like MBL are detected in general population screenings and do not likely have a risk of CLL that is substantially higher than that of unaffected individuals. Interestingly, MBL frequency increases with age, being virtually undetectable under 40 years of age but being present in 50-75% of the people older than 90 years. It has been proposed that MBL could be interpreted as an epiphenomenon of a chronic and persistent antigenic stimulation. The (rare) possibility to evolve into a frank leukemia might then depend on biological and molecular factors insofar unknown that may modify the modality of cell reaction as well as the potential to acquire further genetic abnormalities. Therefore, the real challenge of the next years in the MBL research field is not to increase the sensitivity of detection, neither to implement screening protocols to be applied to the general population, rather to unravel the biologic features that, at individual level, will identify those (few) cases that are at risk of developing a progressive disease.

The role of estrogen receptor beta (ERbeta) in malignant diseases--a new potential target for antiproliferative drugs in prevention and treatment of cancer

The discovery of ERbeta in the middle of the 1990s represents a paradigm shift in our understanding of estrogen signaling. It has turned out that estrogen action is not mediated by one receptor, ERalpha, but by two balancing factors, ERalpha and ERbeta, which are often antagonistic to one another. Excitingly, ERbeta has been shown to be widespread in the body and to be involved in a multitude of physiological and pathophysiological events. This has led to a strong interest of the pharmaceutical industry to target ERbeta by drugs against various diseases. In this review, focus is on the role of ERbeta in malignant diseases where the anti proliferative activity of ERbeta gives hope of new therapeutic approaches.

High-density screening reveals a different spectrum of genomic aberrations in chronic lymphocytic leukemia patients with 'stereotyped' IGHV3-21 and IGHV4-34 B-cell receptors

BACKGROUND

The existence of multiple subsets of chronic lymphocytic leukemia expressing 'stereotyped' B-cell receptors implies the involvement of antigen(s) in leukemogenesis. Studies also indicate that 'stereotypy' may influence the clinical course of patients with chronic lymphocytic leukemia, for example, in subsets with stereotyped IGHV3-21 and IGHV4-34 B-cell receptors; however, little is known regarding the genomic profile of patients in these subsets.

DESIGN AND METHODS

We applied 250K single nucleotide polymorphism-arrays to study copy-number aberrations and copy-number neutral loss-of-heterozygosity in patients with stereotyped IGHV3-21 (subset #2, n=29), stereotyped IGHV4-34 (subset #4, n=17; subset #16, n=8) and non-subset #2 IGHV3-21 (n=13) and non-subset #4/16 IGHV4-34 (n=34) patients.

RESULTS

Over 90% of patients in subset #2 and non-subset #2 carried copy-number aberrations, whereas 75-76% of patients in subset #4 and subset #16 showed copy-number aberrations. Subset #2 and non-subset #2 patients also displayed a higher average number of aberrations compared to patients in subset #4. Deletion of 13q was the only known recurrent aberration detected in subset #4 (35%); this aberration was even more frequent in subset #2 (79%). del(11q) was more frequent in subset #2 and non-subset #2 (31% and 23%) patients than in subset #4 and non-subset #4/16 patients. Recurrent copy-number neutral loss-of-heterozygosity was mainly detected on chromosome 13q, independently of B-cell receptor stereotypy.

CONCLUSIONS

Genomic aberrations were more common in subset #2 and non-subset #2 than in subset #4. The particularly high frequency of del(11q) in subset #2 may be linked to the adverse outcome reported for patients in this subset. Conversely, the lower prevalence of copy-number aberrations and the absence of poor-prognostic aberrations in subset #4 may reflect an inherently low-proliferative disease, which would prevent accumulation of genomic alterations.

High expression of the inhibitory receptor BTLA in T-follicular helper cells and in B-cell small lymphocytic lymphoma/chronic lymphocytic leukemia

B- and T-lymphocyte attenuator (BTLA) is a lymphoid receptor that inhibits lymphocyte activation on interaction with its ligand, herpesvirus entry mediator (HVEM). We developed monoclonal antibodies against BTLA and HVEM to study their expression using immunohistochemical and flow cytometric analyses in human tissues. In reactive lymph nodes, they were both expressed in interfollicular T cells and in B cells from mantle and marginal zones. Within germinal centers, B cells were negative, whereas T follicular helper (TFH) cells were BTLA+ and follicular dendritic cells were HVEM+. BTLA was strongly expressed in chronic lymphocytic leukemia/small lymphocytic lymphoma (B-CLL/SLL, 19 of 19 positive) when compared with other small B-cell lymphomas, including follicular lymphoma (0 of 24 positive), mantle cell lymphoma (0 of 10 positive), and marginal zone lymphoma (0 of 5 positive). Our results suggest that down-regulation of the BTLA-HVEM pathway may be involved in germinal center B-cell activation. The specific high expression of BTLA in B-CLL/SLL represents a new potential diagnostic tool. The BTLA positivity of TFH cells may be a basis for designing future immunotherapies.

Common community acquired infections and subsequent risk of chronic lymphocytic leukaemia

Emerging evidence supports a role for immune-related factors in the causation of chronic lymphocytic leukaemia (CLL). Using the population-based U.S. Surveillance Epidemiology and End Results-Medicare database, 10,171 elderly CLL patients and 122,531 frequency-matched controls were identified in order to evaluate several community acquired infections associated with subsequent CLL risk. Odds ratios (ORs) were adjusted for gender, age, race, calendar year and number of physician claims. CLL risk was increased following Medicare claims for sinusitis (OR = 1.11; 95% CI = 1.05-1.17), pharyngitis (OR = 1.15; 1.08-1.22), bronchitis (OR = 1.14; 1.08-1.19), pneumonia (OR = 1.17; 1.11-1.24), influenza (OR = 1.10; 1.01-1.19), cellulitis (OR = 1.08; 1.02-1.14) and herpes zoster (OR = 1.26; 1.15-1.37). Associations with pneumonia and cellulitis remained significant when the 5-year period before diagnosis/control selection was excluded. CLL risk increased with increasing severity/frequency of pneumonia (P = 0.005), cellulitis (P < 0.001) and herpes zoster (P < 0.001). Our findings suggest that common infections may play a role in CLL aetiology. Alternatively, the associations might reflect an underlying immune disturbance present several years prior to CLL diagnosis.

Intrinsic and extrinsic factors influencing the clinical course of B-cell chronic lymphocytic leukemia: prognostic markers with pathogenetic relevance

B-cell chronic lymphocytic leukemia (CLL), the most frequent leukemia in the Western world, is characterized by extremely variable clinical courses with survivals ranging from 1 to more than 15 years. The pathogenetic factors playing a key role in defining the biological features of CLL cells, hence eventually influencing the clinical aggressiveness of the disease, are here divided into "intrinsic factors", mainly genomic alterations of CLL cells, and "extrinsic factors", responsible for direct microenvironmental interactions of CLL cells; the latter group includes interactions of CLL cells occurring via the surface B cell receptor (BCR) and dependent to specific molecular features of the BCR itself and/or to the presence of the BCR-associated molecule ZAP-70, or via other non-BCR-dependent interactions, e.g. specific receptor/ligand interactions, such as CD38/CD31 or CD49d/VCAM-1. A putative final model, discussing the pathogenesis and the clinicobiological features of CLL in relationship of these factors, is also provided.

AID constrains germinal center size by rendering B cells susceptible to apoptosis

The germinal center (GC) is a transient lymphoid tissue microenvironment that fosters T cell–dependent humoral immunity. Within the GC, the B cell–specific enzyme, activation-induced cytidine deaminase (AID), mutates the immunoglobulin locus, thereby altering binding affinity for antigen. In the absence of AID, larger GC structures are observed in both humans and mice, but the reason for this phenomenon is unclear. Because significant apoptosis occurs within the GC niche to cull cells that have acquired nonproductive mutations, we have examined whether a defect in apoptosis could account for the larger GC structures in the absence of AID. In this report, we reveal significantly reduced death of B cells in AID−/− mice as well as in B cells derived from AID−/− bone marrow in mixed bone marrow chimeric mice. Furthermore, AID-expressing B cells show decreased proliferation and survival compared with AID−/− B cells, indicating an AID-mediated effect on cellular viability. The GC is an etiologic site for B-cell autoimmunity and lymphomagenesis, both of which have been linked to aberrant AID activity. We report a link between AID-induced DNA damage and B-cell apoptosis that has implications for the development of B-cell disorders.

Differential aiolos expression in human hematopoietic subpopulations

The Aiolos transcription factor plays a crucial role in the control of lymphocyte differentiation and proliferation. The expression of Aiolos isoform has been studied in lymphoid pathologies but nothing is known about its expression in unaffected human hematopoietic subpopulations. In this manuscript we show for the first time the differential Aiolos expression at the RNA and protein level in hematopoietic cell subpopulations. B cells express higher levels of Aiolos than NK and T cells while monocytes express almost undetectable levels of Aiolos. Moreover, human CD34 (+) progenitors do not express Aiolos. We did not observe significant difference when comparing naive to memory T and B cells, but we observed an important difference between Bright and Dim NK cells. Furthermore, we show that, in addition to hematopoietic cells, non hematopoietic cell lines such as MCF-7, SW480, HEK, PC3 and HeLa also express Aiolos.

TLR9-activating DNA up-regulates ZAP70 via sustained PKB induction in IgM+ B cells

In the past, ZAP70 was considered a T cell-specific kinase, and its aberrant expression in B-CLL cells was interpreted as a sign of malignant transformation and dedifferentiation. It was only recently that ZAP70 was detected in normal human B cells. In this study, we show that TLR9-activated B cells resemble B-cell chronic lymphocytic leukemia cells with regard to CD5, CD23, CD25, and heat shock protein 90 expression. Furthermore, stimulatory CpG and GpC DNA oligonucleotides target CD27(+)IgM(+) and CD27(-)IgM(+) B cells (but not IgM(-) B cells) and enhance ZAP70 expression predominantly in the IgM(+)CD27(+) B cell subset. ZAP70 is induced via activation of TLR-7 or -9 in a MyD88-dependent manner, depends on protein kinase B (PKB)/mammalian target of rapamycin signaling and is rapamycin sensitive. Furthermore, ZAP70 expression levels correlate with induction of cyclin A2, prolonged B cell proliferation, and sustained induction of PKB. These events are not observed upon CD40 ligation. However, this deficit can be overcome by the expression of constitutively active PKB, given that CD40 ligation of PKB-transgenic B cells induces B cell proliferation and ZAP70 expression. These results highlight a major difference between CD40- and TLR-7/9-mediated B cell activation and suggest that ZAP70 expression levels in B cells give an estimate of the proliferative potential and the associated PKB availability.

Cell motility in chronic lymphocytic leukemia: defective Rap1 and alphaLbeta2 activation by chemokine

Chemokine-induced activation of alpha4beta1 and alphaLbeta2 integrins (by conformational change and clustering) is required for lymphocyte transendothelial migration (TEM) and entry into lymph nodes. We have previously reported that chemokine-induced TEM is defective in chronic lymphocytic leukemia (CLL) and that this defect is a result of failure of the chemokine to induce polar clustering of alphaLbeta2; engagement of alpha4beta1 and autocrine vascular endothelial growth factor (VEGF) restore clustering and TEM. The aim of the present study was to characterize the nature of this defect in alphaLbeta2 activation and determine how it is corrected. We show here that the alphaLbeta2 of CLL cells is already in variably activated conformations, which are not further altered by chemokine treatment. Importantly, such treatment usually does not cause an increase in the GTP-loading of Rap1, a GTPase central to chemokine-induced activation of integrins. Furthermore, we show that this defect in Rap1 GTP-loading is at the level of the GTPase and is corrected in CLL cells cultured in the absence of exogenous stimuli, suggesting that the defect is the result of in vivo stimulation. Finally, we show that, because Rap1-induced activation of both alpha4beta1 and alphaLbeta2 is defective, autocrine VEGF and chemokine are necessary to activate alpha4beta1 for ligand binding. Subsequently, this binding and both VEGF and chemokine stimulation are all needed for alphaLbeta2 activation for motility and TEM. The present study not only clarifies the nature of the alphaLbeta2 defect of CLL cells but is the first to implicate activation of Rap1 in the pathophysiology of CLL.

Stimulation of iNOS expression and apoptosis resistance in B-cell chronic lymphocytic leukemia (B-CLL) cells through engagement of Toll-like receptor 7 (TLR-7) and NF-kappaB activation

B-CLL cells are characterized by in vivo resistance to apoptosis due, in part, to the presence of an inducible nitric oxide synthase, iNOS, as the NO released plays anti-apoptotic role, notably by inhibiting caspases. The mechanisms leading to spontaneous expression of iNOS in these cells are presently unknown. The restricted use of some V(H) sub-groups and the sequences of the monoclonal immunoglobulins of the B-cell receptor expressed by the leukemia cells suggested that the latter have encountered specific auto-antigens and/or microbial derived antigens. Their binding to the BCR provides an activation signal resulting in enhanced survival, hence could be involved in the aetiology of the disease. At the interface of innate and cognate immunity, Toll-like receptors, TLR, recognize PAMPs (pathogen-associated molecular patterns) expressed by various bacteria and virus as well as some self-antigens. We thus hypothesized that TLR were involved in the early steps of B-CLL oncogenesis, notably apoptosis resistance through the induction of iNOS expression and the production of NO. Our results show that B-CLL cells express TLR-7 and TLR-9. Incubation of B-CLL cells with TLR-7 agonists effectively resulted in an increased resistance to apoptosis that was reverted with the NOS inhibitor L-NMMA. This resistance was associated with enhanced iNOS expression (protein and mRNA) and NO release, stimulation of NF-kappaB activation, phosphorylation of I kappaB alpha, all these events being suppressed with wedelolactone or Bay 11-7085, two inhibitors of I kappaB alpha phosphorylation. Our present data thus suggest that TLR-7 signaling stimulates apoptosis resistance, notably through an NF-kappaB-dependent activation of the NO pathway.

The Aiolos transcription factor is up-regulated in chronic lymphocytic leukemia

The Aiolos transcription factor, member of the Ikaros family of zinc finger proteins, plays an important role in the control of mature B lymphocyte differentiation and proliferation, and its function appears to be modulated through alternative splicing. To assess Aiolos isoform role in humans' pathologies, we studied Aiolos variant distribution and expression in mature B lymphoproliferative disorders (chronic lymphocytic leukemia [CLL] and other B-cell lymphomas). We demonstrated that more than 80% of expressed Aiolos in normal as well as in malignant B cells is of the hAio1 type, and we showed for the first time a homogeneous overexpression of the total amounts of Aiolos transcripts in the B cells of CLL patients, independently of ZAP-70 and IgVH mutational status prognosis factors. This up-regulation of Aiolos, confirmed at protein level, seems independent of Aiolos promoter H3K9 acetylation and H3K4 trimethylation.

Similarities and differences between the light and heavy chain Ig variable region gene repertoires in chronic lymphocytic leukemia

Analyses of Ig V(H)DJ(H) rearrangements expressed by B-CLL cells have provided insights into the antigen receptor repertoire of B-CLL cells and the maturation stages of B-lymphocytes that give rise to this disease. However, less information is available about the L chain V gene segments utilized by B-CLL cells and to what extent their characteristics resemble those of the H chain. We analyzed the V(L) and J(L) gene segments of 206 B-CLL patients, paying particular attention to frequency of use and association, mutation status, and LCDR3 characteristics. Approximately 40% of B-CLL cases express V(L) genes that differ significantly from their germline counterparts. Certain genes were virtually always mutated and others virtually never. In addition, preferential pairing of specific V(L) and J(L) segments was found. These findings are reminiscent of the expressed VH repertoire in B-CLL. However unlike the V(H) repertoire, V(L) gene use was not significantly different than that of normal B-lymphocytes. In addition, Vkappa genes that lie more upstream on the germline locus were less frequently mutated than those at the 3' end of the locus; this was not the case for Vlambda genes and is not for V(H) genes. These similarities and differences between the IgH and IgL V gene repertoires expressed in B-CLL suggest some novel features while also reinforcing concepts derived from studies of the IgH repertoire.

Similarities and differences between the light and heavy chain Ig variable region gene repertoires in chronic lymphocytic leukemia

Analyses of Ig V(H)DJ(H) rearrangements expressed by B-CLL cells have provided insights into the antigen receptor repertoire of B-CLL cells and the maturation stages of B-lymphocytes that give rise to this disease. However, less information is available about the L chain V gene segments utilized by B-CLL cells and to what extent their characteristics resemble those of the H chain. We analyzed the V(L) and J(L) gene segments of 206 B-CLL patients, paying particular attention to frequency of use and association, mutation status, and LCDR3 characteristics. Approximately 40% of B-CLL cases express V(L) genes that differ significantly from their germline counterparts. Certain genes were virtually always mutated and others virtually never. In addition, preferential pairing of specific V(L) and J(L) segments was found. These findings are reminiscent of the expressed VH repertoire in B-CLL. However unlike the V(H) repertoire, V(L) gene use was not significantly different than that of normal B-lymphocytes. In addition, Vkappa genes that lie more upstream on the germline locus were less frequently mutated than those at the 3' end of the locus; this was not the case for Vlambda genes and is not for V(H) genes. These similarities and differences between the IgH and IgL V gene repertoires expressed in B-CLL suggest some novel features while also reinforcing concepts derived from studies of the IgH repertoire.