Elevated levels of biologically active soluble CD40 ligand in the serum of patients with chronic lymphocytic leukaemia

Soluble immune checkpoint molecules: Serum markers for cancer diagnosis and prognosis

BACKGROUND

With the recent advances in the understanding of the interaction of the immune system with developing tumor, it has become imperative to consider the immunological parameters for both cancer diagnosis and disease prognosis. Additionally, in the era of emerging immunotherapeutic strategies in cancer, it is very important to follow the treatment outcome and also to predict the correct immunotherapeutic strategy in individual patients. There being enormous heterogeneity among tumors at different sites or between primary and metastatic tumors in the same individual, or interpatient heterogeneity, it is very important to study the tumor-immune interaction in the tumor microenvironment and beyond. Importantly, molecular tools and markers identified for such studies must be suitable for monitoring in a noninvasive manner.

RECENT FINDINGS

Recent studies have shown that the immune checkpoint molecules play a key role in the development and progression of tumors. In-depth studies of these molecules have led to the development of most of the cancer immunotherapeutic reagents that are currently either in clinical use or under different phases of clinical trials. Interestingly, many of these cell surface molecules undergo alternative splicing to produce soluble isoforms, which can be tracked in the serum of patients.

CONCLUSIONS

Several studies demonstrate that the serum levels of these soluble isoforms could be used as noninvasive markers for cancer diagnosis and disease prognosis or to predict patient response to specific therapeutic strategies.

CD30/CD30 Ligand and CD40/CD40 Ligand in Malignant Lymphoid Disorders

CD30 and CD40 are members of the tumor necrosis factor (TNF) receptor family. These two receptors have pleiotropic biologic functions including induction of apoptosis and enhancing cell survival. This review will discuss the pattern of expression of these receptors in malignant lymphoid disorders and their prospective ligands. Understanding issues related to these two ligands and their receptors in lymphoid malignancies may help to improve the classification of these diseases and could open the doors for new treatment strategies.

Role of CD154 in cancer pathogenesis and immunotherapy

Many factors and molecules have been investigated as potential players in the pathogenesis or immunosurveillance of cancer. Among these, CD154 has been recognized as a co-stimulatory molecule with high potential for treating cancer, in addition to its contribution in the development of the disease. CD154 was initially described for its pivotal role in T cell-dependent humoral responses via an interaction with its classical receptor, CD40. Subsequent studies showed that CD154 is also implicated in cell-mediated immunity and inflammation via an interaction with CD40 alone or in combination with newly identified receptors, members of the integrin family, leading to the development of chronic inflammatory and autoimmune diseases. In the current article, we present an overview of the role of CD154 as a potential etiological factor in tumors inducing proliferation of malignant cells, their rescue from apoptosis and their invasiveness. In addition, this review describes the immuno-regulatory functions of CD154 against cancer reflected by its stimulation of antigen-presenting cells and the subsequent activation of effector cells, its enhancement of malignant cells' immunogenicity, its modulation of immune settings around tumors, and its initiation of proliferation inhibiting effects in malignant cells. In vitro as well as in vivo studies are outlined and a particular attention is given to clinical studies and progress reached at this point. Findings reviewed herein will improve our knowledge of the role of the CD154 system in cancers from causative to immunotherapeutic functions, paving the way for the identification of new targets for prevention and/or treatment of malignant disorders.

Clinical significance of elevated serum soluble CD40 ligand levels as a diagnostic and prognostic tumor marker for pancreatic ductal adenocarcinoma

BACKGROUND

CD40-CD40 ligand (CD40L) interaction is considered to contribute to the promotion of prothrombotic responses and production of angiogenesis-associated factor in addition to adaptive immune responses. Recently, the role of soluble CD40L (sCD40L) has gained interest in cancer, although its exact functions remain unknown. This study evaluated the clinical significance of sCD40L in patients with pancreatic ductal adenocarcinoma (PDAC) and validated its utility as a PDAC diagnostic and prognostic biomarker.

METHODS

Serum sCD40L levels were measured by chemiluminescent immunoassay and compared among normal, chronic pancreatitis (CP, high-risk), and PDAC group in both training (n=25 per group) and independent validation (n=30, 30, and 55, respectively) datasets through one-way ANOVA test with the post-hoc Bonferroni method. To evaluate the diagnostic potential of serum sCD40L for PDAC, receiver operating characteristic (ROC) curves were generated and logistic regression analysis was conducted. To investigate the sCD40L-assoicated cytokines/chemokines in PDAC, cytokines/chemokines levels were analyzed by a MILLIPLEX MAP Human Cytokine/Chemokine Kit. To assess the prognostic potentials of sCD40L, Kaplan-Meier survival curve and Cox proportional-hazards regression analysis were applied.

RESULTS

Serum sCD40L levels were significantly higher in PDAC group compared with non-cancer groups in both training (p<0.05) and validation (p<0.05) datasets. Clinically, serum sCD40L closely correlated with unresectability (γs=0.342, p=0.011) and distant metastasis (γs=0.294, p=0.030) of PDAC. ROC curve and logistic regression analysis demonstrated the remarkable predictive potentials of serum sCD40L for PDAC (80.0% sensitivity and 85.5% specificity at cut-off point, 0.45; logistic regression), superior to those of CA19-9 and CEA. According to cytokines/chemokines assay, serum sCD40L levels were closely correlated with serum levels of pro-angiogenic cytokines (EGF, VEGF, IL-8) and immunosuppressive cytokines (IL-6, IL-10, IL-1RA). Kaplan-Meier survival analysis demonstrated patients with high-serum sCD40L (>35,000 ng/ml) had a poorer prognosis than those with low-serum sCD40L (log-rank, p=0.015). Multivariate Cox regression analysis yielded a hazard ratio of 2.509 (95% CI, 1.038-6.067, p=0.041) for mortality in the high-serum sCD40L group.

CONCLUSIONS

Serum sCD40L is correlated with immunosuppression and angiogenesis in PDAC carcinogenesis/progression, and is a promising diagnostic and prognostic biomarker for PDAC superior to CA19-9 and CEA.

Monoclonal antibodies in chronic lymphocytic leukemia

Multiple options are now available for the treatment of chronic lymphocytic leukemia. Over the last 10 years, monoclonal antibodies have become an integral part of the management of this disease. Alemtuzumab has received approval for use in patients with fludarabine-refractory chronic lymphocytic leukemia. Rituximab has been investigated extensively in chronic lymphocytic leukemia both as a single agent and in combination with chemotherapy and other monoclonal antibodies. Epratuzumab and lumiliximab are newer monoclonal antibodies in the early phase of clinical development. This article will review the monoclonal antibodies more commonly used to treat chronic lymphocytic leukemia, the results obtained with monoclonal antibodies as single agents and in combination with chemotherapy, and other biological agents and newer compounds undergoing clinical trials.

A phase 1 study of lucatumumab, a fully human anti-CD40 antagonist monoclonal antibody administered intravenously to patients with relapsed or refractory multiple myeloma

In this open-label, multicentre, phase 1 study a fully human anti-CD40 antagonist monoclonal antibody, lucatumumab, was evaluated in patients with relapsed/refractory multiple myeloma (MM). The primary objective was to determine the maximum tolerated dose (MTD) based on dose-limiting toxicities (DLTs). Secondary objectives included safety, pharmacokinetics, pharmacodynamics and antimyeloma activity. Twenty-eight patients, enrolled using a standard '3 + 3' dose escalation, received one or two (n = 3) cycles of lucatumumab 1·0, 3·0, 4·5 or 6·0 mg/kg once weekly for 4 weeks. Common lucatumumab-related adverse events were reversible, mild-to-moderate infusion reactions. Severe adverse events were anaemia, chills, hypercalcaemia and pyrexia (7% each). DLTs included grade 4 thrombocytopenia, grade 3 increased alanine aminotransferase and grade 4 increased lipase (n = 1 each). The MTD was 4·5 mg/kg. At doses ≥3·0 mg/kg, sustained receptor occupancy (≥87%), observed throughout weekly infusions up to 5 weeks after the last infusion, correlated with an estimated half-life of 4-19 d. Twelve patients (43%) had stable disease, and one patient (4%) maintained a partial response for ≥8 months. These findings indicate that single-agent lucatumumab was well tolerated up to 4·5 mg/kg with modest clinical activity in relapsed/refractory MM, warranting further study as a combination therapy.

CD154 expression triggered by purine analogues in vitro: Correlation with treatment response and autoimmune events in chronic lymphocytic leukemia

OBJECTIVE

Despite a fludarabine-based treatment is the first choice of therapy in chronic lymphocytic leukemia (CLL), not all patients achieve a partial or complete response and some of them develop autoimmune manifestations. The aim of this study was to evaluate the influence of CD154 on these adverse effects because CD154 is involved in both B-cell survival and autoimmunity.

MATERIALS AND METHODS

Peripheral blood mononuclear cells (PBMC) from 36 patients with CLL were cultured in vitro with fludarabine or 2-chlorodeoxyadenosine for 24, 48, and 72 hours.

RESULTS

Seven patients (19.4%) presented CD154 expression in PBMC cultured with purine analogues in vitro for 24 and/or 48 hours, while no expression was found when cultured in media alone. These seven patients showed a decreased apoptotic rate in vitro after purine analogues compared with those patients who did not express CD154 (p = 0.01 for fludarabine; p < 0.001 for 2-chlorodeoxyadenosine). CD154 expression was found to have prognostic value for response to fludarabine in vivo and was associated with the development of autoimmune manifestations (odds ratio = 25; 95% confidence interval = 3.5-166.7; p < 0.001).

CONCLUSION

Our preliminary results suggest that CD154 expression in CLL patients, which may be induced by purine analogues, is associated with resistance to fludarabine and with development of autoimmune manifestations.

Coexpression of CD40 and CD40L on B Lymphoma and Carcinoma Cells: an Autocrine Anti-Apoptotic Role

To evaluate a possible autocrine role of CD40L, the expression and functional activity of CD40L on NHL and breast carcinoma cell lines were investigated. Using flow cytometry, CD40 was consistently detectable at the surface of all 5 NHL cell lines tested. CD40L expression was detectable at the surface of DAUDI (54%, MFI 47) and BJAB (12%, MFI 32) cell lines, and marginally on the RAJI cell line (7%, MFI 30), while 4 of 5 NHL cell lines (DAUDI, RAJI, BJAB, BL70) had detectable CD40L mRNA. CD40 was expressed on T47D and BT20 breast carcinoma cell lines while CD40L was detectable on T47D (93%, MFI 137) only. Both BT20 and T47D had detectable CD40 mRNA, while CD40L mRNA was detectable only in the T47D cell line. CD40, but not CD40L, was detectable on 6 renal, 1 prostatic and 1 colon carcinoma cell lines. CD40L expressed on tumor cells was functional, as shown by its capacity to decrease drug-induced apoptosis on CD40 expressing NHL and breast carcinoma cell lines, while irradiated CD40L negative cell line (BT20) had no effect. Blocking CD40L antibody abrogated the protective effect of irradiated CD40L positive T47D cell line against drug-induced apoptosis on BL70 cell line, confirming that CD40L is functional in the DAUDI and T47D cell lines. Importantly, blocking CD40L antibody increased drug-induced apoptosis in CD40L positive cell lines but had no effect on the CD40L negative cell lines. CD40L is expressed on CD40 positive B NHL and breast carcinoma cell lines and induces an autocrine antiapoptotic signal when cells are exposed to cytotoxic agents.

Therapeutic interventions targeting CD40L (CD154) and CD40: the opportunities and challenges

CD40 was originally identified as a receptor on B-cells that delivers contact-dependent T helper signals to B-cells through interaction with CD40 ligand (CD40L, CD154). The pivotal role played by CD40-CD40L interaction is illustrated by the defects in B-lineage cell development and the altered structures of secondary lymphoid tissues in patients and engineered mice deficient in CD40 or CD40L. CD40 signaling also provides critical functions in stimulating antigen presentation, priming of helper and cytotoxic T-cells and a variety of inflammatory reactions. As such, dysregulations in the CD40-CD40L costimulation pathway are prominently featured in human diseases ranging from inflammatory conditions to systemic autoimmunity and tissue-specific autoimmune diseases. Moreover, studies in CD40-expressing cancers have provided convincing evidence that the CD40-CD40L pathway regulates survival of neoplastic cells as well as presentation of tumor-associated antigens to the immune system. Extensive research has been devoted to explore CD40 and CD40L as drug targets. A number of anti-CD40L and anti-CD40 antibodies with diverse biological effects are in clinical development for treatment of cancer and autoimmune diseases. This chapter reviews the role of CD40-CD40L costimulation in disease pathogenesis, the characteristics of therapeutic agents targeting this pathway and status of their clinical development.

The antileukemia activity of a human anti-CD40 antagonist antibody, HCD122, on human chronic lymphocytic leukemia cells

B-cell chronic lymphocytic leukemia (B-CLL) is a lymphoproliferative disorder characterized by the surface expression of CD20, CD5 antigens, as well as the receptor CD40. Activation of CD40 by its ligand (CD40L) induces proliferation and rescues the cells from spontaneous and chemotherapy-induced apoptosis. CD40 activation also induces secretion of cytokines, such as IL-6, IL-10, TNF-alpha, IL-8, and GM-CSF, which are involved in tumor cell survival, migration, and interaction with cells in the tumor microenvironment. Here we demonstrate that in primary B-CLL tumor cells, the novel antagonist anti-CD40 monoclonal antibody, HCD122, inhibits CD40L-induced activation of signaling pathways, proliferation and survival, and secretion of cytokines. Furthermore, HCD122 is also a potent mediator of antibody-dependent cellular cytotoxicity (ADCC), lysing B-CLL cells more efficiently than rituximab in vitro, despite a significantly higher number of cell surface CD20 binding sites compared with CD40. Unlike rituximab, however, HCD122 (formerly CHIR-12.12) does not internalize upon binding to the cells. Our data suggest that HCD122 may inhibit B-CLL growth by blocking CD40 signaling and by ADCC-mediated cell lysis.

A functional TNFRSF5 gene variant is associated with risk of lymphoma

CD40 and its ligand, CD154, are major costimulatory molecules whose interactions are important in humoral and cellular immunity. We hypothesized that single nucleotide polymorphisms (SNPs) in TNFRSF5 and TNFSF5 encoding the CD40 and CD154 proteins, respectively, influence lymphoma risk, particularly a functional TNFRSF5 SNP (-1C>T, rs1883832) associated with reduced B-cell CD40 expression. TNFRSF5 and TNFSF5 SNPs were examined in a population-based case-control study of non-Hodgkin lymphoma (376 cases/801 controls with DNA), and compelling findings were followed up in 2 independent populations. Pooled analyses of all 3 case-control studies (total N = 1776 non-Hodgkin lymphoma cases, N = 2482 controls) revealed an increased risk of follicular lymphoma (FL) associated with the TNFRSF5 -1TT genotype (odds ratio = 1.6; 95% confidence interval, 1.1-2.4). In addition, among women, an inverse association was found between the variant A allele for a TNFSF5 6809G>A SNP and FL risk (OR = .61; 95% CI, 0.36-0.98). In genotype-phenotype studies, significantly reduced circulating soluble CD40 was observed in TNFRSF5 -1TT compared with -1CC carriers. Further, dendritic cells from those with -1TT versus -1CC genotypes exhibited lower CD40 cell surface expression. These results suggest that the TNFRSF5 -1C>T polymorphism may increase FL susceptibility through mechanisms that hinder cellular immune responses. Further studies are needed to explore these findings.

Cellular immune therapy for chronic lymphocytic leukemia

Although chemotherapy can induce complete responses in patients with chronic lymphocytic leukemia (CLL), it is not considered curative. Treated patients generally develop recurrent disease requiring additional therapy, which can cause worsening immune dysfunction, myelosuppression, and selection for chemotherapy-resistant leukemia-cell subclones. Cellular immune therapy promises to mitigate these complications and potentially provide for curative treatment. Most experience with this is in the use of allogeneic hematopoietic stem-cell transplantation (allo-HSCT), in which graft-versus-leukemia (GVL) effects can be observed and shown responsible for long-term disease-free survival. However, use of allo-HSCT for CLL is limited because of the lack of suitable donors and the treatment-related morbidity/mortality for elderly patients, who constitute the majority at risk for developing this disease. The GVL effect, however, suggests there are specific CLL-associated antigens that could be targeted in autologous cellular immune therapy. Effective strategies for this will have to overcome the disease-related acquired immune deficiency and the capacity of the leukemia-cell to induce T-cell tolerance, thereby compromising the activity of even conventional vaccines in patients with this disease. We will discuss the different strategies being developed to overcome these limitations that might provide for effective cellular immune therapy of CLL.

CD40 ligand-mediated activation of the de novo RelB NF-kappaB synthesis pathway in transformed B cells promotes rescue from apoptosis

CD40, a tumor necrosis factor receptor family member, is expressed on B lymphocytes. Interaction between CD40 and its ligand (CD40L), expressed on activated T lymphocytes, is critical for B cell survival. Here, we demonstrate that CD40 signals B cell survival in part via transcriptional activation of the RelB NF-kappaB subunit. CD40L treatment of chronic lymphocytic leukemia cells induced levels of relB mRNA. Similarly, CD40L-mediated rescue of WEHI 231 B lymphoma cells from apoptosis induced upon B cell receptor (surface IgM) engagement led to increased relB mRNA levels. Recently, we characterized a new de novo synthesis pathway for the RelB NF-kappaB subunit, induced by the cytomegalovirus IE1 protein, in which binding of p50/p65 NF-kappaB and c-Jun/Fra-2 AP-1 complexes to the relB promoter works in synergy to potently activate transcription (Wang, X., and Sonenshein, G. E. (2005) J. Virol. 79, 95-105). CD40L treatment of WEHI 231 cells caused induction of AP-1 family members Fra-2, c-Jun, JunD, and JunB. Cotransfection of Fra-2 with the Jun AP-1 subunits and p50/c-Rel NF-kappaB led to synergistic activation of the relB promoter. Ectopic expression of relB or RelB knockdown using small interfering RNA demonstrated the important role of this subunit in control of WEHI 231 cell survival and implicated activation of the anti-apoptotic factors Survivin and manganese superoxide dismutase. Thus, CD40 engagement of transformed B cells activates relB gene transcription via a process we have termed the de novo RelB synthesis pathway, which protects these cells from apoptosis.

High serum levels of soluble CD40-L in patients with undifferentiated nasopharyngeal carcinoma: pathogenic and clinical relevance

BACKGROUND

Engagement of CD40 promotes survival of undifferentiated nasopharyngeal carcinoma (UNPC) cells and similar effects are induced by the EBV oncoprotein LMP-1 that is expressed in a fraction of cases. Considering that CD40 may be activated also by the soluble isoform of CD40L (sCD40L), we investigated the serum levels of sCD40L in a series of 61 UNPC patients from Italy, a non-endemic area for this disease.

RESULTS

At diagnosis, serum samples of UNPC patients contained significantly higher levels of sCD40L than age-matched healthy controls (p < 0.001). High levels of sCD40L (i.e., >18 ng/ml) were more frequently found in patients <40 years of age (p = 0.03) and with distant metastases at presentation (p = 0.03). Serum levels of sCD40L were inversely associated with the expression of the EBV oncoprotein LMP-1 (p = 0.03), which mimics a constitutively activated CD40. The amount of sCD40L decreased in a fraction of patients treated with local radiotherapy alone. Moreover, CD40L+ lymphoid cells admixed to neoplastic UNPC cells were detected in cases with high serum levels of sCD40L, suggesting that sCD40L is probably produced within the tumor mass.

CONCLUSION

sCD40L may contribute to CD40 activation in UNPC cells, particularly of LMP-1-negative cases, further supporting the crucial role of CD40 signalling in the pathogenesis of UNPC. sCD40L levels may be useful to identify UNPC patients with occult distant metastases at presentation.

sCD40 Ligand Determined in Maternal and Umbilical Cord Blood in Pregnancies Complicated by Pre-Eclampsia with and without Intrauterine Growth Retardation

OBJECTIVE

The aim of this study was determination and comparative analysis of the maternal and umbilical cord sCD40L serum levels in pregnancies complicated by pre-eclampsia with and without intrauterine growth retardation (IUGR) and in normotensive pregnancies.

PATIENTS AND METHODS

The study was carried out on 16 patients with singleton pregnancies complicated by severe pre-eclampsia with appropriate-for-gestational-age weight infants and 14 pregnant patients with severe pre-eclampsia complicated by IUGR. The control group consisted of 13 healthy normotensive delivering patients. Five milliliters of blood were taken by venipuncture from each pre-eclamptic patient and from each woman from the control group before active phase of labor and 5 ml of umbilical vein blood were taken immediately after delivery and collected in sterile tubes. Maternal and umbilical serum sCD40L concentrations were estimated using a sandwich ELISA assay.

RESULTS AND CONCLUSIONS

Our results reveal the higher levels of maternal and umbilical sCD40L serum levels in pregnancy complicated by pre-eclampsia with and without IUGR. The mean maternal values were 4.022 +/- 2.399 ng/ml in group P, 3.914 +/- 2.824 ng/ml in group PI and 0.885 +/- 0.064 ng/ml in healthy controls. The mean umbilical values were 2.633 +/- 1.984 ng/ml in group P, 2.703 +/- 1.996 ng/ml in group PI and 1.112 +/- 0.436 ng/ml in the control group. It seems that these higher concentrations of sCD40L protect maternal immune cells bearing CD40 receptor from Fas-mediated apoptosis. Our findings may suggest also enhanced platelet activation in pre-eclamptic patients. It may be one of the factors responsible for the enhanced procoagulatory and proinflammatory properties, and increased cytokine production, and endothelial cell dysfunction in pregnancies complicated by pre-eclampsia.

Emerging drugs for chronic lymphocytic leukaemia

Although the philosophy of management of patients with chronic lymphocytic leukaemia (CLL) has been altered with the advent of fludarabine-based therapies, impact on long-term survival is unclear and a significant proportion of patients will develop resistance to fludarabine. Similar to other haematological malignancies, a potential for 'cure' is likely to be achieved only if 'high-quality' complete remissions (CRs) are achieved. Treatment options for patients who develop resistance to fludarabine continue to be limited, with only a proportion obtaining a response (usually not CRs) with salvage therapies. This review summarises novel therapies that are being evaluated in patients with CLL, specifically those targeting the antiapoptotic Bcl-2 family of proteins and receptors (e.g., CD40, CD80, HLA-DR) involved in mediating survival signals from the microenvironment.

Targeting Lymphoma Cells and Their Microenvironment with Novel Antibodies

Novel monoclonal antibodies are currently being evaluated and have been shown to have significantly influenced the treatment of Hodgkin's and non-Hodgkin's lymphoma. It is of the utmost importance to reduce treatment-related toxicity and, hopefully, improve the cure rate of lymphoma. This is possible by using novel therapies such as monoclonal antibodies, which target tumor cells while sparing normal cells. Investigational antibody therapies include those targeting malignant cells as well as those targeting the microenvironment. Continued investigation is encouraged to combine monoclonal antibodies with other targeted therapies and incorporate their use into standards of care in the treatment of lymphoma.

Novel treatment strategies for aggressive non-Hodgkin's lymphoma

The World Health Organization has included different types of lymphoma under the aggressive category. In the US, diffuse large B-cell lymphoma is the most common aggressive lymphoma and accounts for > 30% of the 55,000 new cases diagnosed annually. Recent advances in the knowledge of the molecular biology have provided an increased understanding of the heterogeneity of non-Hodgkin's lymphoma. New treatments, especially those with the use of monoclonal antibodies, are improving both the survival and the response rate.

Biologically active CD40 ligand is elevated in sickle cell anemia: potential role for platelet-mediated inflammation

OBJECTIVE

After activation, platelets expose CD40 ligand (CD40L) on their surface, then subsequently release the inflammatory mediator as a soluble fragment (sCD40L). Because sickle cell anemia (SCA) is noted for both platelet activation and chronic inflammation, we asked whether platelet-released CD40L potentially plays a role in SCA.

METHODS AND RESULTS

ELISAs demonstrate that SCA patient plasma contains 30-fold more sCD40L than control plasma. Correspondingly, platelets from these patients contain less than half the CD40L found in control platelets. Platelets from patients in painful crises are further depleted of CD40L, with even higher plasma levels, suggesting a correlation to the patient's clinical state. In addition, elevated sCD40L correlates with increased tissue factor in SCA plasma. Blockage of the CD40L receptor CD40 reduces SCA plasma-induced production of tissue factor and endothelial intercellular adhesion molecule-1 (ICAM-1). Finally, sCD40L activity in SCA plasma is confirmed by its induction of B-cell proliferation.

CONCLUSIONS

Platelet-derived sCD40L is elevated in SCA, further elevated in crises, and biologically active. The participation of sCD40L in SCA plasma-induced production of B cells, tissue factor, and ICAM-1 suggests that CD40L may contribute to the chronic inflammation and increased thrombotic activity known to occur in SCA.

Current and Investigational Therapies for Patients with CLL

Clinical and laboratory investigations are driving the rapid change in treatments for patients with chronic lymphocytic leukemia (CLL). Randomized trials have demonstrated superior activity for fludarabine combined with cyclophosphamide versus single-agent fludarabine or chlorambucil as initial treatment. Chemoimmunotherapy holds promise for further improvement and is being tested in randomized trials. New combinations and agents are being identified and tested. Eliminating minimal residual disease is a therapeutic endpoint that may prove to prolong survival and is also under investigation in prospective clinical trials. Work continues toward improving survival and potentially curing patients of this disease.

Novel immune-based treatment strategies for chronic lymphocytic leukemia

Immune-based treatments represent a new group of therapeutic strategies for patients with cancer, including chronic lymphocytic leukemia (CLL), that employ immune effector mechanisms. Among these strategies is passive immunotherapy with monoclonal antibody, alone or in combination with chemotherapy. Active immunotherapy strategies currently under development include vaccines, administration of expanded and activated T cells, and allogeneic stem cell transplantation. These immune-based strategies represent new treatments with potentially complementary mechanisms of action to standard therapies and signify major advances in treatments for patients with CLL.

CD40 stimulation of B-cell chronic lymphocytic leukaemia cells enhances the anti-apoptotic profile, but also Bid expression and cells remain susceptible to autologous cytotoxic T-lymphocyte attack

To enhance the poor antigen-presenting capacity of B-cell chronic lymphocytic leukaemia (B-CLL), CD40 triggering has been considered as an active immunotherapy. However, CD40 stimulation also has an anti-apoptotic effect and may further impair the dysregulated response of B-CLL to apoptotic stimuli. Therefore, we measured the expression of virtually all regulators of apoptosis before and after CD40 stimulation. These findings were correlated with sensitivity for chemotherapy- and death-receptor-induced apoptosis and T-cell-mediated killing. CD40 stimulation enhanced the constitutive anti-apoptotic profile of B-CLL cells by upregulation of Bcl-xL and Bfl-1 and downregulation of the BH3-only protein Harakiri. Unexpectedly, the BH3-only protein Bid was strongly induced. Functionally, CD40-stimulated B-CLL cells became resistant to drug-induced apoptosis and, despite upregulation of CD95 and Bid, were not sensitive to CD95L. In contrast, autologous T cell killing, triggered by loading CLL cells with viral (CMV) peptides, was very efficient both before and after CD40 stimulation. Upon CTL interaction, CLL targets underwent mitochondrial depolarization and caspase-3 activation. Thus, despite an increased anti-apoptotic profile, CD40 triggered B-CLL cells remain excellent targets for resident cytotoxic T cells. These data support therapeutic exploitation of CD40 stimulation in B-CLL, provided that a strong CTL component is induced.

New molecular targets for treatment of lymphoma

In recent years, several molecular mechanisms involved in promoting cancer cell survival and growth have been identified. These discoveries helped in designing and testing novel drugs that target specific cellular pathways. In this review, we focus on new molecular targets that are being explored for the treatment of non-Hodgkin's lymphoma and Hodgkin's disease.

The effect of the Fas/FasL pathway during chemotherapeutic drug-induced apoptosis of leukaemeic cells

The mechanism of chemotherapeutic drug-induced apoptosis in leukaemic cells was studied to further investigate whether Fas/FasL system was involved in apoptosis induced by chemotherapeutic drugs and assess their effects when used in combination with soluble FasL (sFasL). The expression of Fas on human leukaemic cell lines K562, HL-60 and U937 treated with daunorubicin (DNR) or cytosine arabinoside (Ara-C) was detected by using flow cytometry. The activities of sFasL, DNR and Ara-C inducing apoptosis of leukaemic cells, in the absence or presence of neutralizing anti-Fas IgG antibody, were detected by using flow cytometry and TUNEL. The results showed that flow cytometric profiles of K562, HL-60 and U937 cells treated with DNR or Ara-C failed to show any significant increase in Fas expression over 18 h (P > 0.05). Anti-Fas monoclonal antibody (IgG) could not block the apoptosis in leukaemic cells induced by DNR or Ara-C, but could block the apoptosis induced by sFasL. A role of sFasL in a cytotoxic synergistic effect when used in combination with chemotherapeutic drugs was revealed. It was concluded that chemotherapeutic drug-induced apoptosis in human leukaemic cells (UG37, HL-60) is independent of the Fas/FasL system, but combination of sFasL and drug treatment produces a synergistic cytotoxic effect on human leukaemic cells.

Apoptosis of leukemia cells induced by CD34+ cells transferred exogenous Fas ligand

To assess the value of CD34+ cells transferred exogenous Fas ligand (FasL) in inducing apoptosis of human leukemic cells, the CD34+ cells transfected with FasL or without, pretreated with mitomycin C, was mixed with leukemic cell line U937 cells in presence or absence of daunorubicin (DNR) or cytosine arabinoside (Ara-C). After 18 h, apoptosis of cells was detected by FCM and TUNEL. Induced for 18 h by CD34+ cells transfected with FasL or without, the ratio of apoptosis of U937 cells was (5.0 +/- 1.3)%, (10.8 +/- 0.6)% (P < 0.01), respectively. Induced by FasL+ CD34+ + DNR, FasL+ CD34+ + Ara-C, the ratio was (13.4 +/- 1.0)% (P < 0.05), (17.9 +/- 1.3)% (P < 0.01), respectively. The result demonstrated that CD34+ cells transfected with exogenous FasL could induce apoptosis of human leukemic cells and showed a cytotoxic synergistic effect when used in combination with chemotherapeutic drugs, suggesting that it was possible to develop a new method in treatment of leukemia.

The clinical significance of soluble CD86 levels in patients with acute myeloid leukemia and myelodysplastic syndrome

BACKGROUND

Levels of the soluble form of CD86 (sCD86) are elevated in a proportion of patients with leukemia. Although it is a potential modulator of antitumor responses, the significance of sCD86 in patients with hematologic malignancies is unknown.

METHODS

The authors evaluated sCD86 levels by enzyme-linked immunosorbent assay in patients with acute myeloid leukemia (AML) (n = 57 patients) and patients with myelodysplastic syndrome (MDS) (n = 40 patients) and analyzed the relation between sCD86 levels and various clinical parameters.

RESULTS

Levels of sCD86 were elevated (> 2.32 ng/mL) relative to normal donors (0.22-2.32 ng/mL; n = 51 patients) in 25% of patients with AML and in 27% of patients with MDS. Patients with AML who had elevated sCD86 levels had significantly lower complete remission (CR) rates compared with patients with AML who had normal sCD86 levels. In multivariate analysis using sCD86 as a continuous variable and including the interaction of age and sCD86 as a variable, sCD86 was a significant prognostic factor (P = 0.014) independent of cytogenetics. Further analysis demonstrated that, in patients with AML age 60 years and younger, but not in patients older than 60 years, elevated sCD86 levels were associated with significantly shorter survival (P = 0.04). There was no correlation between sCD86 levels and CR rates or survival in patients with MDS.

CONCLUSIONS

The presence in patients with AML of elevated levels of circulating sCD86 were associated with lower CR rates and poor survival. The prognostic significance of sCD86 was independent of cytogenetics but was modulated by age, in that it was independently significant only in younger patients. The results suggest that sCD86 may play a role in modulating immune responses associated with the progression of AML.

Emerging applications of the tumor necrosis factor family of ligands and receptors in cancer therapy

Abnormalities of the tumor necrosis factor (TNF) family members have been linked to several human diseases, including cancer. Novel treatment strategies for cancer are emerging based on an understanding of the function of TNF family members. The advantage of these strategies is their potential to selectively target cancer cells, while sparing normal cells. Combining these new strategies with currently available treatments such as chemotherapy and radiation therapy is under investigation, with promising results. However, because some TNF family members are toxic to normal mammalian cells when administered systemically, only a few TNF family members have potential therapeutic value. This concise review focuses on the clinical implications of four TNF family members for cancer treatment: CD30/CD30 ligand, CD40/CD40 ligand, receptor activator of nuclear factor-kappaB (RANK)/RANK ligand, and TNF-related apoptosis-inducing ligand (TRAIL) Apo-2L/TRAIL receptors.

Tracking death dealing by Fas and TRAIL in lymphatic neoplastic disorders: pathways, targets, and therapeutic tools

In the past decade, it was concluded from a number of investigations that death domain-containing members of the tumor necrosis factor-receptor (TNF-R) family and their ligands such as Fas/FasL and TNF-related apoptosis-inducing ligand (TRAIL)-R/TRAIL are essential for maintaining an intact immune system for surveillance against infection and cancer development and that nondeath domain-containing members such as CD30 or CD40 are involved in the fine tuning of this system during the selection process of the lymphatic system. In line with this conclusion are the observations that alterations in structure, function, and regulation of these molecules contribute to autoimmunity and cancer development of the lymphoid system. Besides controlling size and function of the lymphoid cell pool, Fas/FasL and TRAIL-R/TRAIL regulate myelopoiesis and the dendritic cell functions, and severe alterations of these lineages during the outgrowth and expansion of the lymphoid tumors have been reported. It is the aim of this review to summarize what is currently known about the complex role of these two death receptor/ligand systems in normal, disturbed, and neoplastic hemato-/lymphopoiesis and to point out how such knowledge can be used in developing novel, therapeutic options and the problems that will have to be faced along the way.

Clinical implications of the tumor necrosis factor family in benign and malignant hematologic disorders

Tumor necrosis factor (TNF), originally identified as a factor produced in the serum of endotoxin-injected animals, is a cytokine that mediates tumor necrosis. To date, 20 different members of the TNF superfamily and 21 different receptors have been identified. All ligands of the TNF superfamily have been found to activate transcription factor NF-kappaB and c-Jun kinase. Members of this family have diverse biologic effects, including induction of apoptosis, promotion of cell survival, and regulation of the immune system. The current review focuses on four members that play important roles in regulating hematopoietic cells and are involved in the pathogenesis of several hematologic malignancies. The potential therapeutic use of these members also is discussed.

Serum concentrations of sCD30 and sCD40L in patients with malignant bone tumours

The aim of this study was to evaluate serum levels of both soluble CD30 (sCD30) and soluble CD40 ligand (sCD40L) in patients with malignant bone tumours and to determine their ability to serve as serum markers. Sera of 31 patients were taken at the time of diagnosis, analysed by ELISA, and the results were correlated with clinical features and compared with healthy controls. Soluble CD30 and sCD40L levels were significantly higher in all patient groups than in the healthy controls. Soluble CD30 levels showed statistically significant differences between high malignant osteosarcoma and Ewing sarcoma (P = 0.015), whereas no statistically significant correlation was seen between different types of tumours and sCD40L levels. Soluble CD30 and sCD40L seem to be of diagnostic value in osteosarcoma and Ewing sarcoma.

The antiapoptotic effects of blood constituents in patients with chronic lymphocytic leukemia

OBJECTIVE

Clonal B-lymphocytes of chronic lymphocytic leukemia (B-CLL) are characterized by decreased sensitivity to programmed cell death and, therefore, they accumulate in vivo. However, these malignant cells die rapidly in vitro. In the current study we concentrated on the contribution of autologous serum (AS) and lymphocyte subsets to the survival of the malignant cells in vitro.

METHODS

Mononuclear cells from the peripheral blood of 26 CLL patients and 24 controls were incubated overnight in the presence or absence of AS and heat-inactivated AS (HI-AS) or fetal calf serum (FCS). Also, isolated B cells were incubated at different concentrations in the presence of AS and/or isolated T cells. The level of apoptosis of CD19+ cells was measured by flow cytometry.

RESULTS

Spontaneous apoptosis of unfractionated B-CLL cells incubated with AS, FCS or without serum was significantly lower than the rate of B-cell death in the control group, in similar culture conditions. AS had an antiapoptotic effect on unfractionated B-CLL cells when compared with FCS. The rate of apoptosis of B-CLL cells was directly associated with stage. HI of AS had a variable effect, which was related to the stage of the disease. High concentrations of B cells and the addition of autologous T cells reduced the rate of apoptosis when incubated without serum. The antiapoptotic effect of T cells was most prominent in progressive stages.

CONCLUSIONS

B-CLL cells exhibit decreased spontaneous apoptosis, which is partially prevented by humoral (AS) and cellular (T cells and B-CLL cells) factors. The equilibrium between apoptotic and antiapoptotic factors changes with disease progression.

IL-4 and interferon gamma regulate expression of inducible nitric oxide synthase in chronic lymphocytic leukemia cells

Chronic lymphocytic leukemia (B-CLL) is characterized by the accumulation of long-lived non-dividing CD5(+) B cells. Nitric oxide (NO) is an important regulator of apoptosis, and the viability of cultured B-CLL cells may be dependent on the autocrine production of nitric oxide by inducible nitric oxide synthase (NOS2). We performed this study to determine whether cytokine factors that prevent spontaneous in vitroapoptosis of B-CLL cells induce B-CLL cell NOS2 enzyme activity. B-CLL cells expressed NOS enzyme activity and NOS2 protein and mRNA. IL-4 and IFN-gamma increased B-CLL cell NOS2 enzyme activity and protein expression during in vitro culture. IFN-gamma, but not IL-4, increased NOS2 mRNA expression in cultured B-CLL cells suggesting that IL-4-mediated changes of NOS2 protein expression occurred at the post-transcriptional level. We were unable to detect increased concentrations of nitrite or nitrate (NO(x)) as surrogate markers of NO production in B-CLL cell cultures treated with IL-4 or IFN-gamma. IL-4 and IFN-gamma diminished NOS inhibitor-induced B-CLL cell death. In summary, we found that B-CLL cells expressed NOS2 and that IL-4 and IFN-gamma increased B-CLL NOS2 expression. Cytokine-mediated expression of NOS2 by B-CLL cells may promote their survival, and therapeutic strategies that target NOS2 or quench NO may be beneficial in patients with B-CLL.

Apoptosis in lymphocytic leukemias and lymphomas

Most current classifications of lymphoid neoplasms define the tumors based on the cell of origin, phenotype, genetic abnormalities, and clinical features. Here it is proposed that human lymphocytic tumors can be categorized based on the propensity and capacity of the tumor cells to undergo apoptosis. The first category is defined by malignant cells that are resistant to apoptosis due to expression of anti-apoptotic factors such as bcl-2 and cellular inhibitors of apoptosis (IAPs). These tumors would include CLL and follicular lymphomas, as well as some malignancies in which the tumor cells are infected by viruses that co-opt cell survival pathways, such as human T-cell leukemia/lymphoma virus (HTLV)-1. The second category, in which the malignant cells are apoptosis-prone, would include tumors arising in the context of impaired cytotoxic T-cell function. These neoplasms would include some human immunodeficiency virus (HIV)-related lymphomas such as Burkitt's lymphoma, and post-transplantation lymphomas. The third category would include neoplasms of intermediate sensitivity to apoptosis, some of which are associated with infection such as mucosa-associated lymphoid tissue (MALT) lymphomas of the stomach. Although this classification is tentative, it should evolve in parallel with our understanding of pathogenic mechanisms in lymphoid neoplasia, and provides a novel framework with which to consider the appropriateness of specific therapeutic strategies. Distinctions among lymphocytic tumors in terms of the likelihood of response to therapies such as antisense to bcl-2 related proteins, inhibitors of NF-kappa B activity, and new approaches aimed at bolstering the host's immune response, would cross standard classifications based on the T or B-cell origin of the tumor cells.

Chronic lymphocytic leukaemia: a model for investigating potential new targets for the therapy of indolent lymphomas

We address two key issues whose investigation may help to define new prognostic parameters and new potential targets for therapeutic intervention. First, which are the conceptual implications of the cellular origin of indolent lymphomas? Second, how may deciphering the biology of chronic lymphocytic leukaemia (CLL) lead to the development of new modalities of treatment? The latter issue is articulated in the following three key questions. (1) Which are the molecular pathways through which the microenvironment exerts its influence on the malignant clone? (2) What are the relationships between proliferation and defective apoptosis? (3)Is there any evidence of a role for antigenic stimulation?

Surface membrane antigen expression changes induced in vitro by exogenous growth factors in chronic lymphocytic leukemia cells

The factors determining the growth and survival of cells in B chronic lymphocytic leukemia (CLL) have remained poorly understood. We investigated the effects of optimal mitogen combinations (OMCs) on the expression of 26 surface membrane antigens among 33 CLL patients. The seven OMCs used were selected after pre-testing 14 combinations of (1) S. aureus Cowan I (SAC), (2) interleukin-2 (IL-2), (3) tumor necrosis factor alpha (TNF-alpha) and (4) 12-O-tetradecanoylphorbol 13-acetate (TPA; also known as phorbol 12-myristate 13-acetate or PMA). In flow cytometry we revealed that OMCs induced statistically highly significant upregulation of the expression of CD5, CD11c, CD19, CD22, CD23, CD25, CD38, CD40, CD45, CD45RO, CD95, CD126, CD130 and FMC7, and downregulation of CD20 and CD124 expression. Interestingly, the expression of CD27, CD45RA, CD79b, CD80, CD122 and that of the immunoglobulin gene superfamily members CD21, Ig-kappa, Ig-lambda, Ig-delta and Ig-micro were not significantly affected under similar conditions. The expression of several antigens was co-regulated, suggesting common regulatory pathways. These antigens include CD11c/CD5, CD11c/CD22, CD11c/CD126, CD11c/FMC7 as well as CD27/CD45, CD27/CD45RA and CD27/CD79b. Upregulation of surface antigen expression, induced by OMCs, should be applicable in antibody therapy in vitro and in vivo, and in negative stem cell selection for autotransplantation. Furthermore, the current strategy to enhance cell surface antigen expression may be a versatile tool to raise humoral and cell-mediated host defense against CLL cells. Upregulation of proteins mediating positive growth signals (eg CD25, CD40) and negative signals or apoptosis (eg CD95) may be used to sensitize cells to chemotherapy and programmed cell death.

Expression of CD154 on renal cell carcinomas and effect on cell proliferation, motility and platelet-activating factor synthesis

CD40 activation by CD154 may trigger diverse cellular responses, ranging from proliferation and differentiation to growth suppression and cell death, in normal and malignant cells. However, the pathophysiologic role of CD154 expressed by tumor cells remains unclear. We have investigated the expression of the CD40-CD154 system in 24 primary cultures derived from renal cell carcinomas, its correlation with tumor stage and its potential functional significance. We found coexpression of CD40 and CD154 in most of the renal carcinoma cell lines. CD154, but not CD40 expression, significantly correlated with tumor stage. Moreover, renal carcinoma cell lines also released the soluble form of CD154 into the supernatant. CD40 engagement by CD154 did not affect apoptosis or survival. On the contrary, CD154 stimulated cell proliferation, motility and production of PAF, a phospholipid mediator of inflammation with angiogenic properties. Furthermore, the renal carcinoma cell lines expressed PAF-R. Blockade of PAF-R by WEB-2170, a PAF-R antagonist, abolished the CD154-dependent motility, indicating a role for PAF synthesized after CD154 stimulation in renal carcinoma cell motility. In conclusion, this study identifies new functional properties for CD154, which are potentially relevant for the growth and dissemination of renal carcinoma cells.

Human plasma contains a soluble form of CD86 which is present at elevated levels in some leukaemia patients

Cell surface expression of CD86 (mCD86) provides an important co-stimulatory signal which profoundly influences immune responses. In this report, we investigated the potential presence of a circulating soluble form of CD86 (sCD86) in normal individuals and patients with acute myeloid leukaemia (AML) or B cell chronic lymphocytic leukaemia (B-CLL). Circulating sCD86 was detected in the plasma of all normal individuals (1.04 +/- 0.33 ng/ml, n = 51) and patients analysed. Plasma collected from AML patients in remission (n = 6) contained only low levels of sCD86 but significantly elevated levels (> or =2.65 ng/ml, P < 0.0001) were detected in 10/24 AML patients analysed at the time of presentation or relapse. Significantly elevated levels of sCD86 were also detected in 2/17 B-CLL patients. There was no correlation between sCD86 levels and other clinical parameters. RT-PCR analysis demonstrated that normal monocytes and dendritic cells, as well as isolated AML (n = 2) and B-CLL (n = 4) cells, expressed an alternatively spliced transcript of CD86 which encoded a soluble form absent in normal T, B and NK cells. The finding that a proportion of leukaemia patients contain elevated levels of sCD86 and that at least some leukaemic cells express sCD86 transcript suggests a potential role for sCD86 in modulating mCD86 signalling during the malignant process.

Levels of soluble CD40 ligand (CD154) in serum are increased in human immunodeficiency virus type 1-infected patients and correlate with CD4(+) T-cell counts

CD40 ligand (CD40L or CD154) is a costimulatory molecule expressed mainly on activated CD4(+) T cells. Concentrations of the soluble form of CD40L (sCD40L) in serum were determined for a cohort of 77 human immunodeficiency virus type 1 (HIV-1)-infected patients before and after initiation of highly active antiretroviral treatment (HAART) by a quantitative enzyme-linked immunosorbent assay. Circulating sCD40L levels were higher by twofold in untreated patients than in healthy controls (means +/- standard deviations [SD]: 1.41 +/- 1.48 versus 0.69 +/- 0.59 ng/ml; P < 0.001). HIV-1-infected patients classified as CD4 T-cell category 1 had significantly higher sCD40L levels than patients classified as CD4 categories 2 and 3 (mean +/- SD: 2.08 +/- 1.46 ng/ml versus 1.57 +/- 1.58 [category 2] and 0.94 +/- 1.25 ng/ml [category 3]; P = 0.046), while no correlation with clinical categories A, B, and C was found. Individual serum sCD40L levels correlated with CD4(+) T-cell counts (P = 0.039) but not with viral load, gamma globulin levels, or acute-inflammatory-response markers. After 8 to 12 months of HAART, a further threefold increase of serum sCD40L levels, which paralleled the increase of CD4(+) T-cell counts, was observed. These novel findings suggest that sCD40L measurement in HIV-1-infected patients could serve as a new surrogate marker useful in the assessment of treatment efficacy, especially in settings where well-equipped laboratories and funding required for CD4(+) T-cell count and viral load measurements are not available.

Latent sensitivity to Fas-mediated apoptosis after CD40 ligation may explain activity of CD154 gene therapy in chronic lymphocytic leukemia

Patients with chronic lymphocytic leukemia (CLL) treated with adenovirus (Ad)-CD154 (CD40L) gene therapy experience reductions in leukemia cell counts and lymph node size associated with induction of the death receptor Fas (CD95). CD4 T cell lines can induce apoptosis of CD40-activated CLL cells via a CD95 ligand (CD95-L)-dependent mechanism. To examine whether CD95-L was sufficient to induce cytolysis of CD40-activated CLL cells, we used Chinese hamster ovary cells transfected with CD95-L as cytotoxic effector cells. CD40-activated CLL cells were initially resistant to CD95-mediated apoptosis despite high-level expression of CD95. However, after 72 h, CLL cells from seven of seven patients became increasingly sensitive to CD95-mediated apoptosis. This sensitivity correlated with a progressive decline in Flice-inhibitory protein (FLIP), which was induced within 24 h of CD40 ligation. Down-regulation of FLIP with an antisense oligonucleotide or a pharmacologic agent, however, was not sufficient to render CLL cells sensitive to CD95-mediated apoptosis in the 24-72 h after CD40 activation. Although the levels of pro-Caspase-8 appeared sufficient, inadequate levels of Fas-associated death domain protein (FADD) and DAP3 may preclude assembly of the death-inducing signaling complex. Seventy-two hours after CD40 ligation, sensitivity to CD95 and a progressive increase in FADD and DAP3 were associated with the acquired ability of FADD and FLIP to coimmunoprecipitate with the death-inducing signaling complex after CD95 ligation. Collectively, these studies reveal that CD40 ligation on CLL B cells induces a programmed series of events in which the cells initially are protected and then sensitized to CD95-mediated apoptosis through shifts in the balance of the anti- and proapoptotic proteins FLIP and FADD.

Expression of CD40 ligand (CD154) in B and T lymphocytes of Hodgkin disease: potential therapeutic significance

BACKGROUND

The malignant Hodgkin and Reed-Sternberg (H/RS) cells of Hodgkin disease (HD) express CD30 and CD40 receptors that can activate nuclear factor kappa B and transduce survival signals. The authors have reported previously that the B lymphocytes of HD express CD30 ligand (CD30L, CD153). Furthermore, they and others have reported previously that the CD40L survival pathway is augmented in patients with B-cell malignancies, as CD40L was constitutively expressed by the malignant B cells and infiltrating T cells, and sera from those patients contained elevated levels of soluble CD40L. In this study, the authors investigated the hypothesis that the survival of H/RS cells was similarly promoted by an augmented CD40L signals in HD patients.

METHODS

The expression of CD40L on lymphocyte subsets of patients with classic HD was determined by two-color fluorescent-activated cell sorter analysis. Serum soluble CD40L levels were determined by enzyme linked immunosorbent assay.

RESULTS

CD40L was constitutively expressed on both the T and B cells of HD patients but was more prominently expressed on the B lymphocytes. Soluble CD40L was detected in the serum of 17 of 37 patients (45%) and was higher than 1 ng/mL in 4 patients (10%). Both interleukin (IL)-4 and IL-10, which are known to be secreted by H/RS cells and surrounding T cells, up-regulated CD40L expression on normal B cells.

CONCLUSIONS

Thus, the expression of CD40L and CD30L on the B cells of HD patients suggests that B lymphocytes may play a role in the regulation of H/RS cell growth in vivo. Depriving H/RS cells from CD30L and CD40L survival signals by eliminating B cells from HD lesions may be of therapeutic value.

Functional properties of lymphocytes in idiopathic thrombocytopenic purpura

Idiopathic or immune thrombocytopenic purpura (ITP) is characterized by antibody-mediated destruction of platelets. The etiology is unknown. We postulated that increased autoantibody production in ITP might be attributable to either increased or prolonged expression of CD40 ligand (CD40L, CD154) in T or B lymphocytes, as has been previously observed in systemic lupus erythematosus (SLE). In addition, we hypothesized that ITP is characterized by increased levels of interleukin 4 (IL-4), a prototypic Th2 cytokine which, along with CD40 ligation, is required for B cell differentiation and production of several IgG subclasses. Cell surface CD154 expression was measured in freshly-isolated and in vitro-activated peripheral blood lymphocytes of sixteen ITP patients and eight healthy volunteers. Plasma levels of IL-4 and the prototypic Th1 cytokine interferon-gamma (IFNgamma) were determined. We observed that CD154 expression in unstimulated and in vitro-activated lymphocytes did not differ between ITP patients and healthy controls. Plasma levels of the Th2 cytokine IL-4 were significantly higher in the ITP patients. These studies indicate that overexpression of CD154 in lymphocytes is unlikely to be a primary pathophysiological defect in most patients with ITP. The data support that in addition to cell membrane antigens such as CD154, soluble cytokines such as IL-4 should be considered as potential targets for therapy in this disease.

Survival of leukemic B cells promoted by engagement of the antigen receptor

Chronic lymphocytic leukemia (CLL) is an incurable leukemia characterized by the slow but progressive accumulation of cells in a CD5+ B-cell clone. Like the nonmalignant counterparts, B-1 cells, CLL cells often express surface immunoglobulin with the capacity to bind autologous structures. Previously there has been no established link between antigen-receptor binding and inhibition of apoptosis in CLL. In this work, using primary CLL cells from untreated patients with this disease, it is demonstrated that engagement of surface IgM elicits a powerful survival program. The response includes inhibition of caspase activity, activation of NF-kappaB, and expression of mcl-1, bcl-2, and bfl-1 in the tumor cells. Blocking phosphatidylinositol 3-kinase (PI3-K), a critical mediator of signals through the antigen receptor, completely abrogated mcl-1 induction and impaired survival in the stimulated cells. These data support the contention that CLL cell survival is promoted by antigen for which the malignant clone has affinity, and suggest that pharmacologic interference with antigen-receptor-derived signals has potential for therapy in patients with CLL.

Upstream mediators of the Fas apoptotic transduction pathway are defective in B-chronic lymphocytic leukemia

Data concerning the presence and the functionality of Fas receptor in malignant B-cells are controversial. We have analyzed Fas molecules on B-cells from patients with B-chronic lymphocytic leukemia (B-CLL) cells. We observed a large variability, both of percentage of Fas-positive cells and of intensity of Fas level. Fas triggering was inefficient in inducing apoptosis whatever the number of Fas-positive B-cells, the amount of Fas receptors. B-cells were also resistant to etoposide treatment, but able to undergo apoptosis after dexamethasone treatment. We suggest that the Fas apoptotic pathway is altered in B-CLL patients at the initial step(s) of apoptotic machinery.