The role of toll-like receptors in chronic B-cell malignancies

Autoimmune hemolytic anemia: current knowledge and perspectives

Autoimmune hemolytic anemia (AIHA) is an acquired, heterogeneous group of diseases which includes warm AIHA, cold agglutinin disease (CAD), mixed AIHA, paroxysmal cold hemoglobinuria and atypical AIHA. Currently CAD is defined as a chronic, clonal lymphoproliferative disorder, while the presence of cold agglutinins underlying other diseases is known as cold agglutinin syndrome. AIHA is mediated by autoantibodies directed against red blood cells (RBCs) causing premature erythrocyte destruction. The pathogenesis of AIHA is complex and still not fully understood. Recent studies indicate the involvement of T and B cell dysregulation, reduced CD4+ and CD25+ Tregs, increased clonal expansions of CD8 + T cells, imbalance of Th17/Tregs and Tfh/Tfr, and impaired lymphocyte apoptosis. Changes in some RBC membrane structures, under the influence of mechanical stimuli or oxidative stress, may promote autohemolysis. The clinical presentation and treatment of AIHA are influenced by many factors, including the type of AIHA, degree of hemolysis, underlying diseases, presence of concomitant comorbidities, bone marrow compensatory abilities and the presence of fibrosis and dyserthropoiesis. The main treatment for AIHA is based on the inhibition of autoantibody production by mono- or combination therapy using GKS and/or rituximab and, rarely, immunosuppressive drugs or immunomodulators. Reduction of erythrocyte destruction via splenectomy is currently the third line of treatment for warm AIHA. Supportive treatment including vitamin supplementation, recombinant erythropoietin, thrombosis prophylaxis and the prevention and treatment of infections is essential. New groups of drugs that inhibit immune responses at various levels are being developed intensively, including inhibition of antibody-mediated RBCs phagocytosis, inhibition of B cell and plasma cell frequency and activity, inhibition of IgG recycling, immunomodulation of T lymphocytes function, and complement cascade inhibition. Recent studies have brought about changes in classification and progress in understanding the pathogenesis and treatment of AIHA, although there are still many issues to be resolved, particularly concerning the impact of age-associated changes to immunity.

Autoimmune Cytopenias in Chronic Lymphocytic Leukemia: Focus on Molecular Aspects

Autoimmune cytopenias, particularly autoimmune hemolytic anemia (AIHA) and immune thrombocytopenia (ITP), complicate up to 25% of chronic lymphocytic leukemia (CLL) cases. Their occurrence correlates with a more aggressive disease with unmutated VHIG status and unfavorable cytogenetics (17p and 11q deletions). CLL lymphocytes are thought to be responsible of a number of pathogenic mechanisms, including aberrant antigen presentation and cytokine production. Moreover, pathogenic B-cell lymphocytes may induce T-cell subsets imbalance that favors the emergence of autoreactive B-cells producing anti-red blood cells and anti-platelets autoantibodies. In the last 15 years, molecular insights into the pathogenesis of both primary and secondary AIHA/ITP has shown that autoreactive B-cells often display stereotyped B-cell receptor and that the autoantibodies themselves have restricted phenotypes. Moreover, a skewed T-cell repertoire and clonal T cells (mainly CD8+) may be present. In addition, an imbalance of T regulatory-/T helper 17-cells ratio has been involved in AIHA and ITP development, and correlates with various cytokine genes polymorphisms. Finally, altered miRNA and lnRNA profiles have been found in autoimmune cytopenias and seem to correlate with disease phase. Genomic studies are limited in these forms, except for recurrent mutations of KMT2D and CARD11 in cold agglutinin disease, which is considered a clonal B-cell lymphoproliferative disorder resulting in AIHA. In this manuscript, we review the most recent literature on AIHA and ITP secondary to CLL, focusing on available molecular evidences of pathogenic, clinical, and prognostic relevance.

Targeted silencing of genes related to acute monocytic leukaemia by CpG(B)-MLAA-34 siRNA conjugates

Acute monocytic leukaemia (AML-M5) associated antigen-34 (MLAA-34) is a novel antigen overexpressed in patients with acute monocytic leukaemia. RNA interference is a promising therapy in oncology, especially for refractory acute leukaemia. In this study, we delivered MLAA-34 siRNA into AML-M5 THP-1 cells using CpG(B)-MLAA-34 siRNA conjugates, in the absence of any other transfection reagent. The uptake efficiency and the rate of apoptosis were measured by using flow cytometry. The level of relevant mRNAs was measured by quantitative PCR. THP-1 cell invasion was assessed by transwell assay. Protein expression was analysed by western blotting. The spleen and liver of AML-M5 nude mice were measured and weighted after euthanisation. Spleen sections were analysed by immunohistochemistry. We found that MLAA-34 siRNA was successfully delivered into THP-1 cells and induced MLAA-34 gene silencing via the blockade of JAK2/STAT3 and Wnt/-catenin signalling pathways. In addition, CpG(B)-MLAA-34 siRNA upregulated Gsk3β protein expression, resulting in retraining of the JAK2/STAT3 and Wnt/β-catenin signalling pathways. Importantly, CpG(B)-MLAA-34 siRNA reduced the survival and invasiveness of THP-1 cells. We further demonstrated that CAB39L was effectively downregulated by CpG(B)-MLAA-34 siRNA in vivo. These findings suggested CpG(B)-MLAA-34 siRNA conjugates may provide a novel therapeutic strategy for acute monocytic leukaemia.

Engineering lymphocytes with RNAi

Lymphocytes are the gatekeepers of the body's immune system and are involved in pathogenesis if their surveillance is stalled by inhibitory molecules or when they act as mediators for viral entry. Engineering lymphocytes in order to restore their functions is an unmet need in immunological disorders, cancer and in lymphotropic viral infections. Recently, the FDA approved several therapeutic antibodies for blocking inhibitory signals on T cells. This has revolutionized the field of solid tumor care, together with chimeric antigen receptor T cell (CAR-T) therapy that did the same for hematological malignancies. RNA interference (RNAi) is a promising approach where gene function can be inhibited in almost all types of cells. However, manipulation of genes in lymphocyte subsets are difficult due to their hard-to-transfect nature and in vivo targeting remains challenging as they are dispersed throughout the body. The ability of RNAi molecules to gain entry into cells is almost impossible without delivery strategy. Nanotechnology approaches are rapidly growing and their impact in the field of drug and gene delivery applications to transport payloads inside cells have been extensively studied. Here we discuss various technologies available for RNAi delivery to lymphocytes. We shed light on the importance of targeting molecules in order to target lymphocytes in vivo. In addition, we discuss recent developments of RNAi delivery to lymphocyte subsets, and detail the potential implication for the future of molecular medicine in leukocytes implicated diseases.

TLR Signaling Is Activated in Lymph Node-Resident CLL Cells and Is Only Partially Inhibited by Ibrutinib

Chronic lymphocytic leukemia (CLL) is a malignancy of mature B cells driven by B-cell receptor (BCR) signaling and activated primarily in the lymph node. The Bruton's tyrosine kinase (BTK) inhibitor ibrutinib effectively inhibits BCR-dependent proliferation and survival signals and has emerged as a breakthrough therapy for CLL. However, complete remissions are uncommon and are achieved only after years of continuous therapy. We hypothesized that other signaling pathways that sustain CLL cell survival are only partially inhibited by ibrutinib. In normal B cells, Toll-like receptor (TLR) signaling cooperates with BCR signaling to activate prosurvival NF-κB. Here, we show that an experimentally validated gene signature of TLR activation is overexpressed in lymph node-resident CLL cells compared with cells in the blood. Consistent with TLR activation, we detected phosphorylation of NF-κB, STAT1, and STAT3 in lymph node-resident CLL cells and in cells stimulated with CpG oligonucleotides in vitro. CpG promoted IRAK1 degradation, secretion of IL10, and extended survival of CLL cells in culture. CpG-induced TLR signaling was significantly inhibited by both an IRAK1/4 inhibitor and ibrutinib. Although inhibition of TLR signaling was incomplete with either drug, the combination achieved superior results, including more effective inhibition of TLR-mediated survival signaling. Our data suggest an important role for TLR signaling in CLL pathogenesis and in sustaining the viability of CLL cells during ibrutinib therapy. The combination of ibrutinib with a TLR pathway inhibitor could provide superior antitumor activity and should be investigated in clinical studies. SIGNIFICANCE: CLL relies on the concomitant cooperation of B-cell receptor and Toll-like receptor signaling; inhibition of both pathways is superior to inhibition of either pathway alone. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/79/2/360/F1.large.jpg.

TLR2 Expression on Leukemic B Cells from Patients with Chronic Lymphocytic Leukemia

Antigenic stimulation is considered as a possible trigger of neoplastic transformation in chronic lymphocytic leukemia (CLL). B-cell receptor plays a key role in the interactions between the microenvironment and leukemic cells; however, an important role has also been attributed to Toll-like receptors (TLRs). It is believed that disorders of TLR expression may play a part in the pathogenesis of CLL. In this study, we investigated the potential role of TLR2 in CLL by analyzing its expression on leukemic B cells in correlation with clinical and laboratory parameters characterizing disease activity and patients’ immune status. We assessed the frequencies of TLR2⁺/CD19⁺ cells by the flow cytometry method in peripheral blood of 119 patients with CLL. The percentage of TLR2⁺/CD19⁺ cells was significantly lower in patients with CLL as compared to the healthy volunteers. There was also a lower percentage of TLR2⁺/CD19⁺ cells in CLL patients with poor prognostic factors, such as ZAP70 and/or CD38 expression, 17p and/or 11q deletion. On the other hand, among patients with del(13q14) associated with favorable prognosis, the percentage of TLR2⁺/CD19⁺ cells was higher than among those with del(11q22) and/or del(17p13) as well as in the control group. We found an association between low percentage of CD19⁺/CD5⁺/TLR2⁺ cells and shorter time to treatment. We also demonstrated the relationship between low percentage of CD19⁺/CD5⁺ TLR2-positive and overall survival (OS) of CLL patients. CLL patients with a proportion of 1.6% TLR2-positive B CD5⁺ cells (according to the receiver operating characteristic curve analysis) or more had a longer time to treatment and longer OS than the group with a lower percentage of TLR2 positive cells. To sum up, the results of the study suggest that low TLR2 expression is associated with poor prognosis in CLL patients. The monitoring of CD19⁺/CD5⁺/TLR2⁺ cells number may provide useful information on disease activity. Level of TLR2 expression on leukemic B cells may be an important factor of immunological dysfunction for patients with CLL. Our study suggests that TLR2 could becomes potential biological markers for the clinical outcome in patients with CLL.

Tuning inflammation and immunity by the negative regulators IL-1R2 and IL-1R8

Interleukin-1 receptor family members (ILRs) and Toll-Like Receptors (TLRs) are key players in immunity and inflammation and are tightly regulated at different levels. Most cell types, including cells of the innate and adaptive immune system express ILRs and TLRs. In addition, IL-1 family members are emerging as key players in the differentiation and function of innate and adaptive lymphoid cells. IL-1R2 and IL-1R8 (also known as TIR8 or SIGIRR) are members of the ILR family acting as negative regulators of the IL-1 system. IL-1R2 binds IL-1 and the accessory protein IL-1RAcP without activating signaling and can be released as a soluble form (sIL-1R2), thus modulating IL-1 availability for the signaling receptor. IL-1R8 dampens ILR- and TLR-mediated cell activation and it is a component of the receptor recognizing human IL-37. Here, we summarize our current understanding of the structure and function of IL-1R2 and IL-1R8, focusing on their role in different pathological conditions, ranging from infectious and sterile inflammation, to autoimmunity and cancer-related inflammation. We also address the emerging evidence regarding the role of IL-1R8 as a crucial checkpoint molecule in NK cells in anti-cancer and antiviral activity and the potential therapeutic implications of IL-1R8 blockade in specific pathological contexts.

B Cell Lymphoma Immunotherapy Using TLR9-Targeted Oligonucleotide STAT3 Inhibitors

Growing evidence links the aggressiveness of non-Hodgkin’s lymphoma, especially the activated B cell-like type diffuse large B cell lymphomas (ABC-DLBCLs) to Toll-like receptor 9 (TLR9)/MyD88 and STAT3 transcription factor signaling. Here, we describe a dual-function molecule consisting of a clinically relevant TLR9 agonist (CpG7909) and a STAT3 inhibitor in the form of a high-affinity decoy oligodeoxynucleotide (dODN). The CpG-STAT3dODN blocked STAT3 DNA binding and activity, thus reducing expression of downstream target genes, such as MYC and BCL2L1, in human and mouse lymphoma cells. We further demonstrated that injections (i.v.) of CpG-STAT3dODN inhibited growth of human OCI-Ly3 lymphoma in immunodeficient mice. Moreover, systemic CpG-STAT3dODN administration induced complete regression of the syngeneic A20 lymphoma, resulting in long-term survival of immunocompetent mice. Both TLR9 stimulation and concurrent STAT3 inhibition were critical for immune-mediated therapeutic effects, since neither CpG7909 alone nor CpG7909 co-injected with unconjugated STAT3dODN extended mouse survival. The CpG-STAT3dODN induced expression of genes critical to antigen-processing/presentation and Th1 cell activation while suppressing survival signaling. These effects resulted in the generation of lymphoma cell-specific CD8/CD4-dependent T cell immunity protecting mice from tumor rechallenge. Our results suggest that CpG-STAT3dODN as a systemic/local monotherapy or in combination with PD1 blockade can provide an opportunity for treating patients with B cell NHL.

The inhibitory receptor toll interleukin-1R 8 (TIR8/IL-1R8/SIGIRR) is downregulated in chronic lymphocytic leukemia

Toll interleukin-1 receptor 8 (also known as TIR8, SIGIRR, or IL1R8) is a transmembrane receptor that inhibits inflammation. Accordingly, genetic inactivation of this protein exacerbates chronic inflammation and inflammation-associated tumors in mice. In particular, lack of TIR8 triggers leukemia progression in a mouse model of chronic lymphocytic leukemia (CLL), supporting its role as a novel tumor restrainer. The aim of this study was to measure the amount of TIR8 mRNA and protein in CLL cells, and to analyze its regulation of expression. Circulating leukemic cells expressed lower levels of TIR8 compared to normal B-lymphocytes. Treatment of CLL cells with Azacytidine restored higher levels of TIR8 suggesting that DNA methylation may be involved in modulating TIR8 expression, with implications for novel therapeutic strategies.

Toll-like receptors targeting technology for the treatment of lymphoma

INTRODUCTION

The crucial role of Toll-like Receptors (TLRs) in innate and adaptive immune systems is well discussed in the literature. In cancer, TLRs act as a double-edged sword that can promote or suppress tumor growth. Areas covered: In this article, the authors uncover the potential role of TLRs in lymphomas, which are cancers related to the lymphatic system and blood cells. TLRs are de facto inflammation-inducing receptors that can either worsen disease or ameliorate lymphoma treatment. From this perspective, the usage of TLRs to modulate the immune system toward lymphoma regression is desirable. Various strategies have been used so far, and novel ways are being sought out to cure lymphoma. Expert opinion: TLR ligands have successfully been used to improve patient health; however, these receptors must be finely tuned to further optimize therapy. For a better outcome, novel specific ligands, improved pharmacodynamics, and unique targets should be discerned. Ligands with conjugated molecules, nanoparticles, and targeted drug delivery can highly optimize the therapy for lymphoma with various etiologies.

Regulatory Role of IL-1R8 in Immunity and Disease

Interleukin-1 receptor family members (ILRs) and toll-like receptors (TLRs) are characterized by the presence of a conserved intracellular domain and the toll-IL-1resistance (TIR) domain and are key players in immunity and inflammation. ILR and TLR signaling is tightly regulated at different levels. All cell types of the innate immune system express ILRs and TLRs. In addition, IL-1 family members are emerging as key players in the differentiation and function of innate and adaptive lymphoid cells. IL-1R8, also known as TIR8 or SIGIRR, is a fringe member of the ILR family and acts as a negative regulator of ILR and TLR signaling, which dampens ILR- and TLR-mediated cell activation. IL-1R8 is a component of the receptor recognizing human IL-37. Here, we summarize our current understanding of the structure and function of IL-1R8, focusing on its role in different pathological conditions, ranging from infectious and sterile inflammation to autoimmunity and cancer-related inflammation.

MYD88 L265P Mutations, But No Other Variants, Identify a Subpopulation of DLBCL Patients of Activated B-cell Origin, Extranodal Involvement, and Poor Outcome

PURPOSE

Mutations in MYD88 are found in different lymphoproliferative disorders associated with particular biologic characteristics and clinical impact. The aim of this study was to analyze the incidence of MYD88 mutations and its clinical impact in diffuse large B-cell lymphoma (DLBCL).

EXPERIMENTAL DESIGN

The incidence, clinicobiological features, and outcome of 213 patients (115 M/98 F; median age, 65 years) with DLBCL treated with immunochemotherapy in a single institution according to MYD88 mutational status as assessed by an allele-specific PCR assay were analyzed. The cell of origin (COO) was determined in 129 cases by gene expression.

RESULTS

MYD88 mutations were found in 47 cases (22%), including L265P in 39 and S219C and M232F in 4 cases, respectively. Patients with MYD88 L265P were older, presenting frequent extranodal involvement, and mostly corresponded to activated B-cell like (ABC) subtype, whereas no preference in COO was observed in patients with other MYD88 mutations. Five-year overall survival (OS) for MYD88 wild-type, MYD88 L265P, and other variants was 62%, 52%, and 75%, respectively (P = 0.05). International Prognostic Index (IPI) (HR, 2.71; P < 0.001) and MYD88 L265P (HR, 1.786; P = 0.023) were independent variables predicting OS in the multivariate analysis. However, MYD88 L265P lost its independent value when COO was included in the model.

CONCLUSIONS

Our findings indicate that MYD88 L265P mutations, but no other variants, identify a subgroup of DLBCL mainly of ABC origin, with extranodal involvement and poor outcome. Clin Cancer Res; 22(11); 2755-64. ©2016 AACR.

Dysregulated B-cell TLR2 expression and elevated regulatory B-cell frequency precede the diagnosis of AIDS-related non-Hodgkin lymphoma

OBJECTIVES

In antiretroviral therapy (ART)-treated patients, to determine if AIDS-related non-Hodgkin lymphoma (AIDS-NHL) is preceded by: elevated frequency of potentially malignant abnormal activated/germinal center-like B cells, elevated serum prevalence of B-cell stimulatory Toll-like receptor (TLR) ligands resulting from HIV infection-associated microbial translocation, dysregulated B-cell TLR expression/signaling, and perturbations in the frequency of immunoregulatory cells.

DESIGN

A case-control study nested with a cohort study of HIV-infected women.

METHODS

Prediagnostic AIDS-NHL cases (n = 12, collected 1-12 months before diagnosis) and controls (n = 42) from the Women's Interagency HIV Study cohort, were matched for HIV and ART status, age, race, and CD4 lymphocyte count. Serum levels of TLR ligands, the prevalence of malignancy-associated abnormal activated/germinal center-like (CD19CD10CD71CD86AID) B cells, TLR2 expression on B cells, expression of TLR2-modulating micro-RNA, and the frequency of regulatory T and B cells were assessed.

RESULTS

Diagnosis of AIDS-NHL was preceded by a significantly elevated frequency of activated/germinal center-like CD19CD10CD71CD86AID B cells (P = 0.0072), elevated serum prevalence of the TLR2 ligand, and significantly elevated B-cell TLR2 expression (P = 0.0015), positively correlating with the frequency of activated/germinal center-like B cells (rho = 0.7273, P = 0.0144). In cases, a purified subset of activated/germinal center-like B cells exhibited decreased expression of microRNAs that modulate TLR2 signaling, including miR-21, 146a, 146b, and 155. Finally, cases also exhibited significantly elevated frequencies of antitumor immunity inhibitory regulatory B cells (P = 0.0024), but not regulatory T cells.

CONCLUSIONS

Our findings suggest that increased microbial translocation and dysregulated TLR expression/signaling, coupled with an elevated frequency of regulatory B cells, precede the diagnosis of AIDS-NHL in HIV-infected ART-treated patients.

Autoimmune cytopenias in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is frequently complicated by secondary autoimmune cytopenias (AIC) represented by autoimmune hemolytic anemia (AIHA), immune thrombocytopenia (ITP), pure red cell aplasia, and autoimmune granulocytopenia. The distinction of immune cytopenias from cytopenias due to bone marrow infiltration, usually associated with a worse outcome and often requiring a different treatment, is mandatory. AIHA and ITP are more frequently found in patients with unfavorable biological risk factors for CLL. AIC secondary to CLL respond less favorably to standard treatments than their primary forms, and treating the underlying CLL with chemotherapy or monoclonal antibodies may ultimately be necessary.

Ibrutinib inhibits BCR and NF-κB signaling and reduces tumor proliferation in tissue-resident cells of patients with CLL

Chronic lymphocytic leukemia (CLL) cells depend on microenvironmental factors for proliferation and survival. In particular, tissue-resident CLL cells show prominent activation of both B-cell receptor (BCR) and NF-κB pathways. We evaluated the in vivo effects of ibrutinib, a Bruton tyrosine kinase (BTK) inhibitor on tumor cell activation and proliferation in the blood, lymph node, and bone marrow of patients with CLL. Applying validated pathway-specific gene signatures, we detected a rapid and sustained downregulation of BCR and NF-κB signaling in CLL cells from both the peripheral blood and tissue compartments during ibrutinib treatment. Ibrutinib reduced phosphorylation of PLCγ2 and ERK and decreased nuclear protein expression of NF-κB p50. Ibrutinib significantly decreased tumor proliferation and expression of surface activation markers CD69 and CD86, independent of prognostic factors such as IGHV mutational status, chromosome 17p deletion, or prior treatment history. Interestingly, stronger inhibition of BCR signaling in lymph node resident CLL cells after one dose of ibrutinib was associated with a higher rate of nodal response at the end of cycle 2. Together, these data validate on-target effects of BTK inhibition in the tissue compartments and demonstrate that ibrutinib effectively inhibits pathways that promote tumor cell activation and proliferation in vivo. This study is registered at www.clinicaltrials.gov as #NCT01500733.

TLR2-activated B cells are phenotypically similar to the abnormal circulating B cells seen preceding the diagnosis of AIDS-related NHL diagnosis

BACKGROUND

AIDS-related non-Hodgkin lymphoma (AIDS-NHL) is a common AIDS-defining cancer. Prior studies suggest that chronic B-cell activation precedes AIDS-NHL diagnosis. Activation of B cells by multiple factors, including Toll-like receptor (TLR) signaling, leads to the expression of activation-induced cytidine deaminase (AID), a DNA mutating molecule that can contribute to oncogene translocations/mutations, leading to NHL. The goal of this study was to determine whether surface markers expressed on activated and/or germinal center B cells, and AID expression, were elevated on circulating B cells preceding AIDS-NHL and to determine if TLR signaling contributes to this activated B-cell phenotype.

METHODS

Stored viable peripheral blood mononuclear cell specimens, obtained before AIDS-NHL diagnosis, were assessed by multicolor flow cytometry. Additionally, B cells isolated from peripheral blood mononuclear cell were exposed to TLR ligands in vitro, after which B-cell phenotype was assessed by flow cytometry.

RESULTS

An elevated fraction of B cells expressing CD10, CD71, or CD86 was seen in those who went on to develop AIDS-NHL. AID expression was detected in some who developed AIDS-NHL, but not in HIV+ or HIV- controls. TLR2-stimulated purified B cells exhibited the activated B-cell phenotype observed in HIV+ subjects before AIDS-NHL diagnosis.

CONCLUSIONS

These results indicate that an elevated fraction of B cells display an activated/germinal center phenotype in those HIV+ subjects who go on to develop AIDS-NHL and suggest that TLR2-mediated activation may play a role in HIV infection-associated B-cell activation, potentially contributing to the genesis of AIDS-NHL.

Decoys and Regulatory "Receptors" of the IL-1/Toll-Like Receptor Superfamily

Members of the IL-1 family play a key role in innate and adaptive immunity and in the pathogenesis of diverse diseases. Members of IL-1R like receptor (ILR) family include signaling molecules and negative regulators. The latter include decoy receptors (IL-1RII; IL-18BP) and “receptors” with regulatory function (TIR8/SIGIRR; IL-1RAcPb; DIGIRR). Structural considerations suggest that also TIGIRR-1 and IL-1RAPL may have regulatory function. The presence of multiple pathways of negative regulation of members of the IL-1/IL-1R family emphasizes the need for a tight control of members of this fundamental system.

TLR9-mediated siRNA delivery for targeting of normal and malignant human hematopoietic cells in vivo

STAT3 operates in both cancer cells and tumor-associated immune cells to promote cancer progression. As a transcription factor, it is a highly desirable but difficult target for pharmacologic inhibition. We have recently shown that the TLR9 agonists CpG oligonucleotides can be used for targeted siRNA delivery to mouse immune cells. In the present study, we demonstrate that a similar strategy allows for targeted gene silencing in both normal and malignant human TLR9(+) hematopoietic cells in vivo. We have developed new human cell-specific CpG(A)-STAT3 siRNA conjugates capable of inducing TLR9-dependent gene silencing and activation of primary immune cells such as myeloid dendritic cells, plasmacytoid dendritic cells, and B cells in vitro. TLR9 is also expressed by several human hematologic malignancies, including B-cell lymphoma, multiple myeloma, and acute myeloid leukemia. We further demonstrate that oncogenic proteins such as STAT3 or BCL-X(L) are effectively knocked down by specific CpG(A)-siRNAs in TLR9(+) hematologic tumor cells in vivo. Targeting survival signaling using CpG(A)-siRNAs inhibits the growth of several xenotransplanted multiple myeloma and acute myeloid leukemia tumors. CpG(A)-STAT3 siRNA is immunostimulatory and nontoxic for normal human leukocytes in vitro. The results of the present study show the potential of using tumoricidal/immunostimulatory CpG-siRNA oligonucleotides as a novel 2-pronged therapeutic strategy for hematologic malignancies.

Aggressive disease defined by cytogenetics is associated with cytokine dysregulation in CLL/SLL patients

Early treatment of CLL/SLL does not impact survival-reflecting limitations in detecting progression early and identifying asymptomatic patients likely to benefit from early treatment. Improved understanding of CLL/SLL biology would identify better prognostic/predictive markers. This study attempts to address these issues by determining the relationship between cytokine aberrations and poor clinical outcomes in CLL/SLL in the context of a genetic-based prognostic model. Fifty-nine serum cytokines/chemokines were measured in 28 untreated CLL/SLL patients. Patients were stratified as GR or int/PR using cytogenetics. Comparison of CLL/SLL with 28 HCs revealed increased expression of Th2 cytokines (IL-10, IL-5, sIL-2Rα; P≤0.01) and decreased levels of Th1 cytokines (IL-17, IL-23, IFN-γ; P≤0.003). In a multivariate analysis of GR versus int/PR groups, differential expression of sIL-2Rα maintained significance with increased expression in int/PR CLL/SLL. With median follow-up of 54.3 months after diagnosis, four patients incurred disease progression, with an IL-17/sIL-2Rα model predicting need for treatment in all cases. In summary, specific cytokine signatures are associated with genetically defined aggressive disease and predict need for therapy. This suggests utility in detecting disease progression early, identifying those likely to incur a survival advantage with early treatment, and directing future therapy.

TIR8/SIGIRR is an Interleukin-1 Receptor/Toll Like Receptor Family Member with Regulatory Functions in Inflammation and Immunity

Interleukin-1R like receptors (ILRs) and Toll Like Receptors (TLRs) are key receptors of innate immunity, inflammation, and orientation of the adaptive response. They belong to a superfamily characterized by the presence of a conserved intracellular domain, the Toll/IL-1R (TIR) domain, which is involved in the activation of a signaling cascade leading to activation of transcription factors associated to inflammation. The activation of inflammatory responses and immunity by ILRs or TLRs signaling is potentially detrimental for the host in acute and chronic conditions and is tightly regulated at different levels by receptor antagonists, decoy receptors or signaling molecules, and miRNAs. Recent evidence suggests that the ILRs family member TIR8 (also known as SIGIRR) is a regulatory protein acting intracellularly to inhibit ILRs and TLRs signaling. In particular, current evidence suggests that TIR8/SIGIRR dampens TLRs-mediated activation and inhibits signaling receptor complexes of IL-1 family members associated with Th1 (IL-18), Th2 (IL-33), and Th17 (IL-1) differentiation. Studies with Tir8/Sigirr-deficient mice showed that the ability to dampen signaling from ILRs and TLRs family members makes TIR8/SIGIRR a key regulator of inflammation. Here, we summarize our current understanding of the structure and function of TIR8/SIGIRR, focusing on its role in different pathological conditions, ranging from infectious and sterile inflammation, to autoimmunity and cancer-related inflammation.

Toll-like Receptors in Chronic Lymphocytic Leukemia

Toll-like receptors belong to the pattern recognition receptors family present on a variety of immune cells including normal and malignant B-cells. They act as immediate molecular sentinels of innate immunity but also act as a molecular bridge between the innate and the adaptive immune response; distinct Toll-like receptors are able to bind specific pattern molecules of bacteria, viruses and autoantigens. In this review we will briefly introduce the Toll-like receptor family and their expression pattern, signaling and function in the B cell context; following we will summarize the published data on TLR in chronic lymphocytic leukemia, and we will discuss their emerging role in the modulation of leukemia pathobiology.

Overexpression of TCL1 activates the endoplasmic reticulum stress response: a novel mechanism of leukemic progression in mice

Chronic lymphocytic leukemia (CLL) represents 30% of adult leukemia. TCL1 is expressed in ~ 90% of human CLL. Transgenic expression of TCL1 in murine B cells (Eμ-TCL1) results in mouse CLL. Here we show for the first time that the previously unexplored endoplasmic reticulum (ER) stress response is aberrantly activated in Eμ-TCL1 mouse and human CLL. This includes activation of the IRE-1/XBP-1 pathway and the transcriptionally up-regulated expression of Derlin-1, Derlin-2, BiP, GRP94, and PDI. TCL1 associates with the XBP-1 transcription factor, and causes the dysregulated expression of the transcription factors, Pax5, IRF4, and Blimp-1, and of the activation-induced cytidine deaminase. In addition, TCL1-overexpressing CLL cells manufacture a distinctly different BCR, as we detected increased expression of membrane-bound IgM and altered N-linked glycosylation of Igα and Igβ, which account for the hyperactive BCR in malignant CLL. To demonstrate that the ER stress-response pathway is a novel molecular target for the treatment of CLL, we blocked the IRE-1/XBP-1 pathway using a novel inhibitor, and observed apoptosis and significantly stalled growth of CLL cells in vitro and in mice. These studies reveal an important role of TCL1 in activating the ER stress response in support for malignant progression of CLL.

Exploiting biological diversity and genomic aberrations in chronic lymphocytic leukemia

There is remarkable heterogeneity in the clinical course and biological characteristics of patient subgroups with chronic lymphocytic leukemia (CLL). Mutations of key tumor suppressors (ATM, miR-15a/16-1 and TP53) have been identified in CLL, and these aberrations are important "drivers" of the disease and some of its clinical characteristics. While some mutations are associated with poor outcome [particularly del(17p) and TP53 mutation], others are linked to a favorable clinical course [e.g. del(13q) as sole aberration]. In addition to genetic aberrations, antigen drive and microenvironmental interactions contribute to the pathogenesis of CLL. How the genetic aberrations impact on the process of antigen drive or microenvironmental interactions is currently unclear. Our improved understanding of the biology and clinical course of specific genetic subgroups is beginning to be translated into more specific and targeted treatment approaches. As a result, genetic subgroups are treated in distinct protocols. This review summarizes the contribution of the microenvironment and the most important genetic aberrations in CLL and how our improved knowledge of the biology of CLL may translate into improved treatment results.

Novel epitope evoking CD138 antigen-specific cytotoxic T lymphocytes targeting multiple myeloma and other plasma cell disorders

The development of an immunotherapeutic strategy targeting CD138 antigen could potentially represent a new treatment option for multiple myeloma (MM). This study evaluated the immune function of CD138 peptide-specific cytotoxic T lymphocytes (CTL), generated ex vivo using an HLA-A2-specific CD138 epitope against MM cells. A novel immunogenic HLA-A2-specific CD138(260-268) (GLVGLIFAV) peptide was identified from the full-length protein sequence of the CD138 antigen, which induced CTL specific to primary CD138(+) MM cells. The peptide-induced CD138-CTL contained a high percentage of CD8(+) activated/memory T cells with a low percentage of CD4(+) T cell and naive CD8(+) T cell subsets. The CTL displayed HLA-A2-restricted and CD138 antigen-specific cytotoxicity against MM cell lines. In addition, CD138-CTL demonstrated increased degranulation, proliferation and γ-interferon secretion to HLA-A2(+) /CD138(+) myeloma cells, but not HLA-A2(-) /CD138(+) or HLA-A2(+) /CD138(-) cells. The immune functional properties of the CD138-CTL were also demonstrated using primary HLA-A2(+) /CD138(+) cells isolated from myeloma patients. In conclusion, a novel immunogenic CD138(260-268) (GLVGLIFAV) peptide can induce antigen-specific CTL, which might be useful for the treatment of MM patients with peptide-based vaccine or cellular immunotherapy strategies.

Chronic lymphocytic leukemia: the pathologist's view of lymph node microenvironment

Chronic lymphocytic leukemia (CLL), an indolent B-cell malignancy frequently diagnosed in the elderly, is characterized by the relentless accumulation of CD5+ monoclonal B cells that proliferate in the appropriate tissue microenvironments. Despite many advances achieved by molecular and functional studies, our knowledge of the reciprocal relationship between the CLL cell and its microenvironment at the tissue level is still largely incomplete. In this review we present the relevant current information on the tissue microenvironmental features of CLL, focusing on the events that appear to occur in the lymph node. Special attention is devoted to analyzing the properties of both neoplastic and nonneoplastic bystander cells within proliferation centers, the mysterious structures that likely represent the actual proliferative compartment.

Lack of TIR8/SIGIRR triggers progression of chronic lymphocytic leukemia in mouse models

Inflammation is involved in the initiation and progression of several chronic lymphoid malignancies of B-cell type. Toll-like receptors (TLR) are transmembrane inflammatory receptors that on recognition of pathogen-associated molecular patterns trigger an innate immune response and bridge the innate and adaptive immune response by acting as costimulatory signals for B cells. Fine tuning of TLR and IL-1R-like (ILR) activity is regulated by TIR8 (SIGIRR), a transmembrane receptor of the TLR/ILR family which inhibits other family members. To test the hypothesis that TLR and/or ILR may play a role in the natural history of chronic B-cell tumors, we crossed Eμ-TCL1 transgenic mice, a well established model of chronic lymphocytic leukemia (CLL), with mice lacking the inhibitory receptor TIR8 that allow an unabated TLR-mediated stimulation. We here report that in the absence of TIR8 the appearance of monoclonal B-cell expansions is accelerated and mouse life span is shortened. The morphology and phenotype of the mouse leukemic expansions reproduce the progression of human CLL into an aggressive and frequently terminal phase characterized by the appearance of prolymphocytes. This study reveals an important pathogenetic implication of TLR in CLL development and progression.

The lymph node microenvironment promotes B-cell receptor signaling, NF-kappaB activation, and tumor proliferation in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL), an incurable malignancy of mature B lymphocytes, involves blood, bone marrow, and secondary lymphoid organs such as the lymph nodes (LN). A role of the tissue microenvironment in the pathogenesis of CLL is hypothesized based on in vitro observations, but its contribution in vivo remains ill-defined. To elucidate the effects of tumor-host interactions in vivo, we purified tumor cells from 24 treatment-naive patients. Samples were obtained concurrently from blood, bone marrow, and/or LN and analyzed by gene expression profiling. We identified the LN as a key site in CLL pathogenesis. CLL cells in the LN showed up-regulation of gene signatures, indicating B-cell receptor (BCR) and nuclear factor-κB activation. Consistent with antigen-dependent BCR signaling and canonical nuclear factor-κB activation, we detected phosphorylation of SYK and IκBα, respectively. Expression of BCR target genes was stronger in clinically more aggressive CLL, indicating more effective BCR signaling in this subtype in vivo. Tumor proliferation, quantified by the expression of the E2F and c-MYC target genes and verified with Ki67 staining by flow cytometry, was highest in the LN and was correlated with clinical disease progression. These data identify the disruption of tumor microenvironment interactions and the inhibition of BCR signaling as promising therapeutic strategies in CLL. This study is registered at http://clinicaltrials.gov as NCT00019370.