Effect of interleukins on the proliferation and survival of B cell chronic lymphocytic leukaemia cells

Clinico-Biological Implications of Modified Levels of Cytokines in Chronic Lymphocytic Leukemia: A Possible Therapeutic Role

B-cell chronic lymphocytic leukemia (B-CLL) is the main cause of mortality among hematologic diseases in Western nations. B-CLL is correlated with an intense alteration of the immune system. The altered functions of innate immune elements and adaptive immune factors are interconnected in B-CLL and are decisive for its onset, evolution, and therapeutic response. Modifications in the cytokine balance could support the growth of the leukemic clone via a modulation of cellular proliferation and apoptosis, as some cytokines have been reported to be able to affect the life of B-CLL cells in vivo. In this review, we will examine the role played by cytokines in the cellular dynamics of B-CLL patients, interpret the contradictions sometimes present in the literature regarding their action, and evaluate the possibility of manipulating their production in order to intervene in the natural history of the disease.

Modeling the chronic lymphocytic leukemia microenvironment in vitro

Microenvironments within the lymph node and bone marrow promote proliferation and drug resistance in chronic lymphocytic leukemia (CLL). Successful treatment of CLL must therefore target the leukemic cells within these compartments. A better understanding of the interaction between CLL cells and the tumor microenvironment has led to the development of in vitro models that mimic the mechanisms that support leukemic cell survival and proliferation in vivo. Employing these models as part of the pre-clinical evaluation of novel therapeutic agents enables a better approximation of their potential clinical efficacy. In this review we summarize the current literature describing how different aspects of the tumor microenvironment have been modeled in vitro and detail how these models have been employed to study the biology of the disease and potential efficacy of novel therapeutic agents.

Interleukin-4 receptor signaling and its binding mechanism: A therapeutic insight from inhibitors tool box

Studies on Interlukin-4 (IL-4) disclosed great deal of information about its various physiological and pathological roles. All these roles depend upon its interaction and signaling through either type-I (IL-4Rα/common γ-chain) or type-II (IL-4Rα/IL-13Rα) receptors. Another cytokine, IL-13, shares some of the functions of IL-4, because both cytokines use a common receptor subunit, IL-4Rα. Here in this review, we discuss the structural details of IL-4 and IL-4Rα subunit and the structural similarities between IL-4 and IL-13. We also describe detailed chemistry of type-I and type-II receptor complexes and their signaling pathways. Furthermore, we elaborate the strength of type-II hetero dimer signals in response to IL-4 and IL-13. These cytokines are prime players in pathogenesis of allergic asthma, allergic hypersensitivity, different cancers, and HIV infection. Recent advances in the structural and binding chemistry of these cytokines various types of inhibitors were designed to block the interaction of IL-4 and IL-13 with their receptor, including several IL-4 mutant analogs and IL-4 antagonistic antibodies. Moreover, different targeted immunotoxins, which is a fusion of cytokine protein with a toxin or suicidal gene, are the new class of inhibitors to prevent cancer progression. In addition few small molecular inhibitors such as flavonoids have also been developed which are capable of binding with high affinity to IL-4Rα and, therefore, can be very effective in blocking IL-4-mediated responses.

Interleukin-1B (IL1B) and interleukin-6 (IL6) gene polymorphisms are associated with risk of chronic lymphocytic leukaemia

Common polymorphisms in genes encoding for cytokines implicated in the inflammatory response and Th1/Th2 balance might play a role in the development and prognosis of chronic lymphocytic leukaemia (CLL). To test the hypothesis, we investigated 13 single nucleotide polymorphisms (SNPs) in nine of such genes in a population-based case-control study, conducted in the Italian region of Sardinia in 1999-2003. Forty incident CLL cases and 113 population controls were available for study. The following SNPs were selected: IL1A-889C > T, IL1RN 9589A > T, IL1B-31C > T, IL1B-511C > T, IL2-384T > G, IL6-174G > C, IL6-597G > A, IL10-1082A > G, IL10-3575T > A, TNF-308G > A, LTA- 91A > C, LTA 252A > G and CARD15 nt1007. After adjusting by age and gender, individuals homozygous for the IL1B-511T allele run a lower risk of CLL (OR = 0.1, 95% CI 0.0, 0.8, p = 0.032), while risk showed a 4.5-fold increase associated with the genotype homozygous for the IL6-174C allele (OR = 4.5; 95% CI 1.1, 19.3, p = 0.041). Individuals homozygous for the IL6-174C allele and carrying the homozygous IL1B-511C allele showed an 11-fold increase in CLL risk (OR = 11.4, 95% CI 1.9, 69.4, p = 0.008). None of the other interleukin SNPs evaluated showed any association with CLL risk. Large multicentre pooled studies are warranted, achieving the statistical power required to confirm whether IL6 and IL1B gene polymorphisms might play a role in CLL development and prognosis, as well as the null associations herein reported.

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.

Dock10, a novel CZH protein selectively induced by interleukin-4 in human B lymphocytes

The Dock or CZH proteins are a family of activators for Rho GTPase proteins. The Zizimin subfamily is composed of three members: Dock9, Dock10, and Dock11. We have identified DOCK10 as an interleukin-4 (IL4)-inducible gene in chronic lymphocytic leukemias (CLLs). Subsequently, we have obtained the full-length cDNA sequence, which encodes a 2180 amino acid protein. Dock9 (2069 amino acids) and Dock11 (2073 amino acids) share more identity between them (58%) than with Dock10 (52% and 50%, respectively). Among normal human tissues, DOCK10 and DOCK11 mRNAs were mainly expressed in peripheral blood (PB) leukocytes. Dock10 protein was expressed at similar levels in normal PB-B and PB-T cells. Dock10 protein levels were heterogeneous in CLLs. IL4 consistently increased Dock10 mRNA and protein levels in CLL and normal PB-B cells. In contrast, IL4 did not affect the levels of Dock10 expression in normal PB-T cells. IL4 neither increased DOCK9 or DOCK11 mRNA levels in CLL cells. Dock10 protein distributed in the cytoplasm and nucleus of CLL cells, and IL4 increased its expression in both cellular compartments. The rapid and distinctive induction of Dock10 expression by IL4 in CLL and normal PB-B cells suggests a role for Dock10 in IL4-induced B-cell activation. Dock10 could represent a point of convergence for IL4 signalling and small Rho GTPase function in B cells.

CD5 provides viability signals to B cells from a subset of B-CLL patients by a mechanism that involves PKC

B-chronic lymphocytic leukaemia (B-CLL) is a heterogeneous disease characterized by an accumulation of B lymphocytes expressing CD5. To date, the biological significance of this molecule in B-CLL B cells remains to be elucidated. In this study, we have analysed the functional consequences of the binding of an anti-CD5 antibody on B-CLL B cells. To this purpose, we have measured the percentage of viability of B-CLL B cells in the presence or in the absence of anti-CD5 antibodies and also examined some of the biochemical events downstream the CD5-signalling. We demonstrate that anti-CD5 induces phosphorylation of protein tyrosine kinases and protein kinase C (PKC), while no activation of Akt/PKB and MAPKs is detected. This signalling cascade results in viability in a group of patients in which we observe an increase of Mcl-1 levels, whereas the levels of bcl-2, bcl-x(L) and XIAP do not change. We also report that this pathway leads to IL-10 production, an immunoregulatory cytokine that might act as an autocrine growth factor for leukaemic B cells. Inhibition of PKC prevents the induction of Mcl-1 and IL-10, suggesting that the activation of PKC plays an important role in the CD5-mediated survival signals in B cells from a subset of B-CLL patients.

Bcl-2 regulatory pathway is functional in chronic lymphocytic leukemia

BACKGROUND

Chronic lymphocytic leukemia (CLL) is characterized by accumulation of clonal, malignant CD5(+), CD23(+) B cells. In vivo, these cells have an antiapoptotic phenotype (high levels of Bcl-2 and low levels of proapoptotic Bcl-2 family proteins, such as Bax). Abnormal B cells accumulate due to altered apoptosis regulation rather than to increased proliferation. However, it is unclear whether there are inherent Bcl-2 apoptotic pathway defects. With in vitro culture, these B cells rapidly apoptosis.

METHODS

To investigate apoptosis regulation, Bcl-2, Bax, mitochondrial membrane potential, annexin V, and caspase activation were simultaneous monitored in individual cells during in vitro apoptosis.

RESULTS

With in vitro culture, 30% to 50% of B cells were apoptotic at 24 h compared with fewer than 10% of T cells. Apoptotic B cells showed dramatic Bax upregulation and slight Bcl-2 decreases accompanied by decreased mitochondrial membrane potential and increased activated caspase-3 protein levels. Caspase-3 and caspase-9 activities were increased 18- to 51-fold and 6- to 11-fold, respectively, after 24 h of culture. Caspase-8 showed limited or no activation (less than fourfold).

CONCLUSIONS

These data show that in vitro apoptosis of CLL B cells occurs through a well-characterized Bcl-2 regulatory pathway consistent with that pathway being functional. Further, these cells' antiapoptotic phenotype is dependent on the in vivo environment, potentially involving paracrine/autocrine interactions.

A recombinant IL-4-Pseudomonas exotoxin inhibits protein synthesis and overcomes apoptosis resistance in human CLL B cells

We have determined that CLL B cells consistently express type 3 membrane receptors for the Th2-derived cytokine IL-4 (IL-4R). Furthermore, when added to CLL B cells, IL-4 induces increased apoptosis resistance, increased protein synthesis in CLL B cells and rapid onset activation of STAT1, STAT5 and STAT6. Since the IL-4-IL-4R pathway is intact in CLL B cells and is related to apoptosis resistance, we considered whether we could target this pathway. A recombinant IL-4 Pseudomonas exotoxin fusion protein (IL-4 PE), known to bind to IL-4R, was incubated with CLL B cells. IL-4 PE (10 ng/ml) cultured with CLL B cells resulted in an increase of apoptosis/death from mean levels of 46.6+/-7.0 of non-exposed cells to 69+/-8.6 (n=6). By measuring in vitro protein synthesis, two predominant patterns of sensitivity were observed. In one, CLL B cell clones (n=4) were found to be extremely sensitive to IL-4 PE (IC50's range=6-25 ng/ml). In the second, low concentrations of IL-4 PE induced agonist activity while increasing concentrations induced cytotoxicity in 6 of 21 patient-derived cells. These studies suggest that the IL-4R, on B-CLL cells, can serve as a unique molecular target for directing cytotoxic agents in the therapy of B-CLL.

Chronic lymphocytic leukemia: A review of some new aspects of the biology, factors influencing prognosis and therapeutic options

This review provides some basic information on chronic lymphocytic leukemia (CLL) and attempts to present some of the newer data which have accumulated in recent years including those relating to familial aggregation of CLL and the detection of monoclonal CD5+ lymphocytosis in the general population and families of CLL patients. Novel data on the pathogenesis and concepts of cell origin in CLL are also reviewed stressing the fact that there is biased IgVH gene usage, and the importance of mutational status of the CLL cell, as reported in recent years by different authors. A brief review of the significance of the microenvironmental interactions between stromal cells and other accessory cells, and the leukemic CLL cells is also provided. Other clinical aspects are discussed including diagnostic criteria, clinical staging, and the newer prognostic factors which influence survival and timing of therapy for CLL patients. We also attempt to outline the therapeutic options available and the principles of planning risk and age-adapted treatment, stressing the importance and the necessity for participating in ongoing and future international clinical trials.

Intracellular IFN-γ expression by CD3+/CD8+ cell subset in B-CLL patients correlates with stage of the disease

Changes in the cytokine network may be responsible for malignant cell accumulation in B-cell chronic lymphocytic leukaemia (B-CLL). Among different cytokines of question interferon gamma (IFN-gamma) is indicated to prevent malignant cells from entering apoptosis. The aim of the study was to determine IFN-gamma production capacity of T-cell subsets and B lymphocytes in B-CLL patients in comparison with healthy individuals and during disease progression. Forty patients with newly diagnosed, untreated B-CLL and 20 healthy individuals were studied. The two- and three-colour flow cytometry techniques were used to detect intracellular cytokine expression. We detected statistically significantly higher percentage of both CD3+/CD4+/IFN-gamma+ and CD3+/CD8+/IFN-gamma+ in patients than in controls (P < 0.001 in both cases). Moreover the percentage of CD3+/CD8+/IFN-gamma+ cells correlated with stage of the disease (R = 0.39, P = 0.01) and parameters of disease progression like lymphocyte count and total tumour mass score (R = 0.33, P = 0.03 and R = 0.31, P = 0.04, respectively). By contrast, the percentage of CD19+/IFN-gamma+ cells in B-CLL group was lower than in controls (P < 0.01). These findings indicate that T-cell populations rather than malignant B cells are the source of IFN-gamma in B-CLL patients. The subset of CD3+/CD8+ cells expressing IFN-gamma seems to play a special role in the disease progression and more precise investigation should elucidate its role as a prognostic marker in B-CLL and a target for therapeutic strategies.

Interleukin 4 production by peripheral blood lymphocytes in patients with classical Hodgkin lymphoma

Although the production of interleukin (IL) 2 and interferon (IFN) gamma by peripheral blood lymphocytes in patients with Hodgkin lymphoma (HL) is well documented, the synthesis of IL4 has not been investigated before. The present study examines the production of IL4 by 2-day phytohaemaglutinin (PHA)-stimulated peripheral blood (PB) cells in HL and correlates the cytokine levels with the proportion of the different T-cell sub-populations. We observed a significant increase in the mean level of production of IL4 in patients with HL when compared with normal controls. The increased amount of IL4 in patients with HL correlated significantly with the proportion of the CD3(+)CD8(+) cells but not with CD3(+)CD4(+). The intensity of cytoplasmic IL4 (expressed as relative median fluorescence (RMF)) was significantly higher in the CD3(+)CD8(+) cells of the patients with HL compared with the CD3(+)CD4(+) sub-population, or with the normal CD3(+)CD8(+) cells and correlated with the levels of IL4 release in culture supernatants. In conclusion, there is increased production of IL4 by PHA-activated PB lymphocytes in HL. The CD3(+)CD8(+) T-cell population appears to be responsible for this increased synthesis.

Production of intracellular IL-2, TNF-alpha, and IFN-gamma by T cells in B-CLL

BACKGROUND

Recent evidence indicates that the slowly expanding population of CD5(+) B cells that characterizes B-cell chronic lymphocytic leukemia (B-CLL) could be related to defects in the response to cytokine produced by T cells that regulate apoptosis. We studied the intracellular expressions of interleukin-2 (IL-2), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma) in T-helper 1 cells (Th1 response) of B-CLL.

METHODS

Peripheral blood mononuclear cells from 21 healthy individuals and purified T cells from 21 early-stage and 15 late-stage B-CLL patients were activated with phorbol myristate acetate and ionomycin. The Th1 cytoplasmic cytokines were evaluated in CD4(+) and CD8(+) T cells by flow cytometry.

RESULTS

The percentages of CD4(+) and CD8(+) T cells positive for IL-2 were significantly lower in B-CLL patients than in healthy individuals (P = 0.030 and 0.049, respectively). No significant differences in TNF-alpha or IFN-gamma intracellular expressions were found between patients and healthy individuals. TNF-alpha- and IFN-gamma-expressing CD8 T cells were disease stage dependent, being significantly higher in late-stage patients (P < 0.001 for both cytokines).

CONCLUSIONS

Our present observations suggested that Th1 cytokines may be of major importance in the pathogenesis of B-CLL.

CD8+ chronic lymphocytic leukemia: an extensive characterization of a bizarre hybrid neoplasia

Atypical chronic lymphocytic leukemia (CLL) expressing the CD8 antigen have a frequency of less than 0.5% of all cases, however, they are not yet been fully characterized. Herein a CD8+ CLL case was extensively studied. Besides the classical CLL antigen expression, an unusual presence of surface markers such as CD11c, CD56, and CD154 was observed. Moreover, gene expression of chemokine receptors belonging to the CCR family were clearly evidenced as well as mRNA for both, Th1 and Th2 cytokines. Likewise, granzyme A, B and perforin gene expression, cytotoxic T cell or NK enzymes were found. The intricate profile of membrane molecules and gene expression suggest that it could be favorable, rather than deletereous, for the maintainance of the neoplastic process.

IL-4 biology: impact on normal and leukemic CLL B cells

This review provides a perspective on the role of IL-4 in relation to both normal and leukemic CLL B cells. IL-4 is a well-characterized cytokine known to be produced by normal T cells and have impact on normal B cell differentiation and proliferation. This cytokine and its receptor are now known to exist on CLL B cells. An autocrine pathway for CLL B cells is strongly supported by signaling events, alteration of apoptotic proteins and changes in apoptosis resistance. Based on the increasing knowledge regarding the IL-4 pathway unique opportunities for therapy are now available in B-CLL.

Spontaneous apoptosis in chronic lymphocytic leukemia and its relationship to clinical and cell kinetic parameters

Chronic lymphocytic leukemia (CLL) presents considerable variability in clinical presentation as well as in its evolution. In contrast to the inhibition of apoptosis in vivo, spontaneous apoptosis after short-term culture occurs. We studied the degree of this apoptosis in vitro, and its interactions with several clinical and laboratory parameters. Apoptosis was measured by the annexin V technique. Proliferation rate was evaluated by the AgNOR (nucleolar organizer regions) technique. There were inverse correlations between the percentage of annexin V-positive cells and peripheral lymphocyte count (r = - 0.49), Rai stage (r = - 0.40), Binet stage (r = - 0.50), TTM (total tumor mass score; r = - 0.51), and percentage of cells with one AgNOR cluster (r = - 0.45). Direct correlations were found with hemoglobin values ( r = 0.34) and platelet counts (r = 0.52). The number of CD8-positive cells showed a correlation with peripheral lymphocyte count (r = 0.49). When this variable was held constant, a correlation was detected between CD8-positive cells and staging (r = -0.47), TTM (r = - 0.42), and platelet count (r = 0.67). CD4-positive lymphocytes presented a correlation only with CD8-positive lymphocytes. In a cluster analysis, it was possible to create three groups of patients with different apoptosis rates using the TTM and AgNOR values. We conclude that, with the progression of the disease, together with the increase of tumor mass and proliferation rate, there is a decrease in the susceptibility to apoptosis.

Expression and production of interleukin 4 in B-cell chronic lymphocytic leukaemia

Interleukin (IL) 4 is a T-cell derived pleiotropic cytokine whose properties include alterations of B-cell function. In B-cell chronic lymphocytic leukaemia (B-CLL), IL4 is involved in the mechanism of survival of the leukaemic B-cells. The present study examines the expression and production of IL4 by B- and T-lymphocytes derived from patients with B-CLL and provides evidence that IL4 is not an autocrine factor in B-CLL. Freshly isolated B-CLL cells enriched for B- and T-cells did not express mRNA for IL4 but expressed mRNA for IL4 receptor (IL4R). Activation of B-cells with phorbol ester and calcium ionophore and of T-cells with phytohaemaglutinin (PHA) upregulated IL4 mRNA expression. However phorbol ester and calcium ionophore did not affect the mean level of IL4 production by either B-CLL or normal B-cells. Furthermore, in the presence or absence of activation, the amount of IL4 synthesised by B-CLL B-cells was not significantly different than that observed with peripheral blood B-cells isolated from normal individuals (with activation: P=0.239; without activation: P=0.565). Also, there was no significant difference between normal and B-CLL B-cells in the level of cytoplasmic IL4 (P=0.47). PHA-activated enriched B-CLL T-cells produced significantly higher levels of IL4 compared to normal control T-cells (P=0.0136). In addition, in 47% of cases with B-CLL T-cells, a significant higher level of intracellular IL4 was observed (P=0.0027). The levels of production of IL4 by the T-cell-enriched preparations correlated positively with the intensity of cytoplasmic L4 in CD4+ and CD8+ cells in tested samples (r=0.49 and r=0.76, respectively). The significant differences observed in the production of IL4 by B-CLL B- and T-lymphocytes may suggest a paracrine function of IL4 in B-CLL.

The levels of TNF alpha, IL4 and IL10 production by T-cells in B-cell chronic lymphocytic leukaemia (B-CLL)

Tumour necrosis factor alpha (TNF alpha), interleukin (IL) 4 and IL10 are important for the growth and survival of the leukaemic cells in B-cell chronic lymphocytic leukaemia (B-CLL). The present study investigates the production of TNF alpha, IL4 and IL10 in patients with B-CLL. Significant increases in the TNF alpha and IL4 mean levels compared to normal control CD2(+)-cells were observed for B-CLL lymphocytes (TNF alpha: P=0.0004 and IL4: P=0.0026). By contrast, the mean level of IL10 produced by purified B-CLL CD2(+)-cells was significantly lower than that seen with normal control T-cells (P=0.0136). No significant difference in the percentage (%) of T-cells that expressed cytoplasmic TNF alpha, IL4 and IL10 was observed between B-CLL and normal T-cells. However, a significant increase in the mean level of intracellular TNF alpha and IL4 expression was observed in B-CLL compared with normal control T-cells (TNF alpha: P=0.031; IL4: P=0.0027). The increased expression of cytoplasmic TNF alpha and IL4 appeared to be associated with increased cytokine production in the tested samples. The differences observed with some B-CLL cases in the production of TNF alpha, IL4 and IL10 by peripheral blood T-cells may suggest survival mechanisms for the leukaemic cells in these patients.

Interleukin 4 therapy for patients with chronic lymphocytic leukaemia: a phase I/II study

Interleukin 4 (IL-4) is a pleiotropic type II cytokine which has been shown to have a direct killing effect on lymphoma and B-cell chronic lymphocytic leukaemia (B-CLL) cells in vitro. The clinical effects and toxicity of IL-4 treatment in patients with B-CLL were evaluated. Fourteen patients with B-CLL who were in partial remission after chemotherapy received one, two or three 8-week cycles of escalating doses (2, 4 or 6 microg/kg/d s.c.) of IL-4 for 3 d/week. Clinical response was analysed after each treatment cycle and toxicity was monitored continuously. Ten patients (71%) had progressive disease (PD) during IL-4 treatment. This was mainly attributable to an increase (two- to fourfold) of the blood lymphocyte count during IL-4 therapy. After cessation of IL-4 treatment, the lymphocytosis decreased spontaneously in 8 out of 12 evaluable patients. Splenomegaly remained unchanged in 7/7 patients, whereas enlarged lymph nodes were reduced by > 50% in 1/13 patients and by 25-50% in 4/13 patients. None of the patients achieved an objective tumour regression (complete or partial remission). A temporary increase (16-60%) of the platelet count was observed during IL-4 treatment. The platelet count decreased in 8/11 patients after the end of IL-4 therapy. World Health Organization (WHO) grade I/II fever, arthralgia and fatigue was observed in one-third of the patients and was more commonly seen with the highest dose (6 microg/kg/d). One patient developed pulmonary oedema and WHO grade III neutropenia was recorded in three patients. IL-4 was well tolerated by most patients in an outpatient setting. The anti-tumour activity observed in previous in vitro studies was not verified by the present in vivo trial which showed that IL-4 may instead increase the number of CLL cells in blood, indicating that IL-4 may have induced a stimulatory or antiapoptotic effect on the CLL cells in blood. These results may have important implications for the development of immunotherapy of CLL. In addition, the potential platelet-stimulatory effect of IL-4 warrants further studies.

Contribution of nitric oxide to the apoptotic process in human B cell chronic lymphocytic leukaemia

B cell chronic lymphocytic leukaemia (B-CLL) is characterised by defective apoptosis that cannot be explained solely on the basis of the known chromosomal abnormalities. We and other have now reported that the leukemic cells spontaneously display the inducible isoform of nitric oxide synthase, iNOS. Inhibition of the iNOS pathway leads to increased apoptosis of the tumoral cells in vitro, indicating that the endogenous release of NO contributes to their resistance to the normal apoptotic process. The factors that induce the expression of iNOS in vivo in the leukemic cells are not yet identified. Yet, as interaction of B-CLL leukemic cells with bone marrow stromal cells promotes their survival, the involvement of adhesion molecules and integrins may be suspected. The engagement of CD23 stimulates iNOS activation in the tumoral cells, suggesting that in vivo interaction of CD23 with one of its recognised ligands may contribute to iNOS induction. A role for CD40-CD40 ligand interaction may also be hypothesised. The mechanisms involved in the anti-apoptotic role of NO are not fully understood, but may implicate the inhibition of caspase activity, hence the impairment of the Fas pathway. In addition, the mitochondrial membrane potential disruption appears to be a NO-sensitive step in the apoptosis cascade. The presence of a NOS displaying anti-apoptotic properties has now been recognised in different cell types, including various leukaemia. A better knowledge of the mechanisms governing the ultimate fate of NO, anti- versus pro-apoptotic would allow the development of new therapeutic approaches for the treatment of these diseases.

Disruption of the IFN-gamma cytokine network in chronic lymphocytic leukemia contributes to resistance of leukemic B cells to apoptosis

Recent evidence indicates that the slowly expanding population of CD5+ B cells that characterizes chronic lymphocytic leukemia (CLL) results primarily from defects in responses to cytokines that regulate apoptosis (e.g. I1-4, TGF-beta, IFN-alpha, IFN-gamma). We have now demonstrated not only that the enhanced anti-apoptotic effect of IFN-gamma on these neoplastic B cells is apparently mediated through increased levels of IFN-gamma receptors but also that there are increased numbers of IFN-gamma-expressing CD4 and CD8 T cells in these patients. This is the strongest evidence to date that multiple alterations in the IFN-gamma cytokine network contribute to the pathogenesis of CLL.

Serum beta-2-microglobulin, TNF-alpha and interleukins in myeloproliferative disorders

Whereas beta-2-microglobulin (beta2M) has mainly been used as a prognostic factor in patients with lymphoproliferative disorders, some studies have reported the value of beta2M in myeloproliferative disorders (MPD). In order to investigate a potential role in the pathogenesis of MPD and to find a possible value as indicators in monitoring the course of the disease, we measured beta2M, TNF-alpha, IL-1alpha, IL-1beta, IL-2, sIL-2R, IL-6 and IL-10 in 55 patients with MPD, at diagnosis and during the course of the disease. In progressive disease and particularly when transformation to acute leukemia occurred, high levels of beta2M, IL-2 and sIL-2R were found in all patients; the elevation was progressive, which suggests a potential prognostic usefulness in the individual patient.

Serum levels of IL-6 type cytokines and soluble IL-6 receptors in active B-cell chronic lymphocytic leukemia and in cladribine induced remission

We have investigated the serum concentrations of interleukin-6 (IL-6) and two IL-6 family cytokines-oncostatin M (OSM) and leukemia inhibitory factor (LIF)-in 63 patients with B-cell chronic lymphocytic leukemia (B-CLL) and 17 healthy controls using the enzyme-linked immunosorbent assay (ELISA) method. Simultaneously, we measured the serum levels of the soluble forms of two subunits of the IL-6 receptor complex-ligand binding glycoprotein 80 (sIL-6R) and glycoprotein 130 (sgp130). The cytokines and receptors were evaluated in 25 untreated patients and 38 patients treated with cladribine (2-CdA), as well as in 17 healthy controls. We have correlated the serum levels of these proteins with Rai's clinical stage of the disease, the response to 2-CdA treatment and some hematological parameters. We have also evaluated the correlation of the IL-6 serum level with the concentration of OSM and IL-6 soluble receptors. IL-6 was measurable in 62/63 (98.4%), OSM in 20/25 (80%) of untreated and 14/38 (37.8%) of the treated patients. sIL-6R and sgp130 were detectable in all 63 patients and LIF in none of the CLL patients. IL-6 serum level in untreated patients was not significantly different as compared to its concentration in the control group (P>0.05). However, in the patients treated with 2-CdA the IL-6 level was significantly lower (P<0.02), and the lowest concentration was found in the patients with complete remission (CR; median 1.4pg/ml; P<0.02). The concentration of sIL-6R was significantly higher in untreated (median 61.8 ng/ml) and treated (median 50.1 ng/ml) CLL patients when compared to normal persons (median 41.2 ng/ml; P=0.04; P<0.001, respectively). There was no difference between the sIL-6R levels in the patients with CR and the healthy controls. In non-responders sIL-6R concentration was the highest and similar to its level in the untreated patients. OSM level was higher in the untreated patients (median 1.8pg/ml) than in the normal controls (median 0.0pg/ml; P<0.001) and in the CR patients (median 0.0pg/ml; P<0.03). The serum concentration of sgp130 was similar in the untreated (median 480 pg/ml) and treated (median 470 pg/ml) patients, as well as in the healthy persons (median 420 pg/ml; P>0.05). We have found significant positive correlation between the levels of sIL-6R and the lymphocytes count in CLL patients (p=0.423; P<0.001). In addition, sIL-6R and OSM serum concentrations correlated also with CLL Rai stage. In conclusion, the serum level of IL-6, OSM and sIL-6R, but not LIF and sgp130, are useful indicators of CLL activity.

B-cell chronic lymphocytic leukemia: a bird of a different feather

PURPOSE

To review the recent major advances in the molecular and cell biology of B-cell chronic lymphocytic leukemia (B-CLL).

METHODS

We analyzed the nature of malignant B-CLL B cells and their interactions with the microenvironment.

RESULTS

B-CLL is a malignancy of a mantle zone-based subpopulation of anergic, self-reactive, activated CD5+ B cells devoted to the production of polyreactive natural autoantibodies. It is the quintessential example of a human malignancy that primarily involves defects in the induction of programmed cell death. An abnormal karyotype is observed in about 50% of patients with B-CLL. Patients with 13q14 abnormalities show heavy somatic mutation and have a benign disease. Trisomy 12 is associated with unmutated VH genes, atypical cellular morphology, and progressive disease. Extended cell survival is further shielded by a kinetic refractoriness likely promoted by abnormalities of the B-cell antigen receptor complex and favored by some cytokines that highlight a reciprocal dialog between malignant B and T cells. Because the tumor cells act as the major accessory cells, the accumulating malignant B-cell population per se is a hurdle to the production of normal antibodies and leads to a progressive and severe hypogammaglobulinemia. Conceivably, in the presence of certain immunoglobulin genes and when the T-cell control becomes deficient, activated malignant B cells may become able to present self-antigens and drive residual normal B cells to produce polyclonal autoantibodies restricted to self-antigens expressed only by blood cells and cause autoimmune cytopenias.

CONCLUSION

The distinctiveness of B-CLL B cells explains why B-CLL is different from other B-cell tumors and accounts for the development of immune deficiency and autoimmunity.

B-Cell Chronic Lymphocytic Leukemia Cells Express a Functional Inducible Nitric Oxide Synthase Displaying Anti-Apoptotic Activity

The expression of different isoforms of nitric oxide synthase (NOS) was investigated in B-cell chronic lymphocytic leukemia (B-CLL) to delineate a possible role for nitric oxide (NO) in the control of apoptosis of the tumoral cells. By reverse transcription-polymerase chain reaction (RT-PCR), all B-CLL cells were found to express spontaneously inducible NOS (iNOS) mRNA, whereas endothelial constitutive NOS (ecNOS) mRNA was undetectable. The iNOS protein was detected by immunofluorescence in the cytoplasm of permeabilized leukemic cells and identified by Western blotting, using different anti-iNOS antibodies, as a protein of 135 kD in B-CLL cytoplasmic extracts. B-CLL cell lysates also displayed basal NOS enzymatic activity, as measured by the conversion of14C-labeled L-arginine into 14C-L-citrulline. Ligation of CD23, expressed on the vast majority of B-CLL cells, resulted in increased iNOS expression and activity. The NO released exerted an anti-apoptotic effect on B-CLL cells that was counteracted by NOS inhibitors and engagement of the APO-1/Fas pathway. Therefore, the existence of a functional iNOS in B-CLL cells will provide further insights into the mechanisms that control proliferation and apoptosis in these tumor cells.

© 1998 by The American Society of Hematology.

B-Cell Chronic Lymphocytic Leukemia Cells Express a Functional Inducible Nitric Oxide Synthase Displaying Anti-Apoptotic Activity

The expression of different isoforms of nitric oxide synthase (NOS) was investigated in B-cell chronic lymphocytic leukemia (B-CLL) to delineate a possible role for nitric oxide (NO) in the control of apoptosis of the tumoral cells. By reverse transcription-polymerase chain reaction (RT-PCR), all B-CLL cells were found to express spontaneously inducible NOS (iNOS) mRNA, whereas endothelial constitutive NOS (ecNOS) mRNA was undetectable. The iNOS protein was detected by immunofluorescence in the cytoplasm of permeabilized leukemic cells and identified by Western blotting, using different anti-iNOS antibodies, as a protein of 135 kD in B-CLL cytoplasmic extracts. B-CLL cell lysates also displayed basal NOS enzymatic activity, as measured by the conversion of14C-labeled L-arginine into 14C-L-citrulline. Ligation of CD23, expressed on the vast majority of B-CLL cells, resulted in increased iNOS expression and activity. The NO released exerted an anti-apoptotic effect on B-CLL cells that was counteracted by NOS inhibitors and engagement of the APO-1/Fas pathway. Therefore, the existence of a functional iNOS in B-CLL cells will provide further insights into the mechanisms that control proliferation and apoptosis in these tumor cells.

© 1998 by The American Society of Hematology.

Regulation of B-CLL apoptosis through membrane receptors and Bcl-2 family proteins

The accumulation of monoclonal chronic lymphocytic leukemia B (B-CLL) cells may be due to excessive proliferation and longevity. Clinical progression may thus come from a constitutive but altered expression of a number of genes that results in extended B-CLL cells life span, increased proliferative capacity and diminished cell death. B-CLL cells express a number of surface markers that characterise the normal B-cells phenotype. However, B-CLL cells are CD5 positive and most of them also express CD6, surface receptors that are present in just a small subset of normal B-cells. When exploring CD6 function, we found out that cross-linking of CD6 protected B-CLL from anti-IgM-induced apoptosis. CD6 activation blocked anti-IgM- induced Bax(alpha) up-regulation and, by doing so, corrected an imbalance in the Bcl-2/Bax ratio that accompanies apoptosis. Here, we review all surface receptors and cytokines that have been described as participating in the induction or protection of B-CLL apoptosis together with data on chemosensitivity and gene modulation, data on the Fas receptor/Fas ligand system, and the implications of all the latter for B-CLL cell survival.

Prognostic Significance of the Cell Cycle Inhibitor p27Kip1 in Chronic B-Cell Lymphocytic Leukemia

B-cell chronic lymphocytic leukemia (B-CLL) is characterized by the accumulation of resting lymphocytes. The identification of p27kip1, a cyclin-dependent kinase inhibitor that contributes to cell cycle arrest and represents a link between extracellular signals and cell cycle, prompted us to study p27 protein in the lymphocytes from 88 patients with B-CLL and 32 patients with other chronic B-lymphoproliferative disorders. The expression of p27 protein was higher in B-CLL samples with variations among them. In B-CLL, p27 levels were independent of absolute number of circulating lymphocytes, but strongly correlated with both lymphocyte and total tumor mass (TTM) doubling time. High p27 expression was associated with a poorer overall prognosis. In vitro, there was an increased spontaneous survival of B-CLL cells expressing high p27 levels. Interleukin-4 (IL-4) upregulated p27 levels in B-CLL cells, while fludarabine decreased p27 levels. Thus, our results indicate that p27 may be a valuable kinetic marker in B-CLL by providing instantaneous estimation of the disease doubling time. In addition, these results suggest that there is a link between p27 expression and the ability of CLL cells to undergo apoptosis.

Prognostic Significance of the Cell Cycle Inhibitor p27Kip1 in Chronic B-Cell Lymphocytic Leukemia

B-cell chronic lymphocytic leukemia (B-CLL) is characterized by the accumulation of resting lymphocytes. The identification of p27kip1, a cyclin-dependent kinase inhibitor that contributes to cell cycle arrest and represents a link between extracellular signals and cell cycle, prompted us to study p27 protein in the lymphocytes from 88 patients with B-CLL and 32 patients with other chronic B-lymphoproliferative disorders. The expression of p27 protein was higher in B-CLL samples with variations among them. In B-CLL, p27 levels were independent of absolute number of circulating lymphocytes, but strongly correlated with both lymphocyte and total tumor mass (TTM) doubling time. High p27 expression was associated with a poorer overall prognosis. In vitro, there was an increased spontaneous survival of B-CLL cells expressing high p27 levels. Interleukin-4 (IL-4) upregulated p27 levels in B-CLL cells, while fludarabine decreased p27 levels. Thus, our results indicate that p27 may be a valuable kinetic marker in B-CLL by providing instantaneous estimation of the disease doubling time. In addition, these results suggest that there is a link between p27 expression and the ability of CLL cells to undergo apoptosis.

Functional aspects of apoptosis in hematopoiesis and consequences of failure

Apoptosis is an internally directed, physiological method of cell destruction. Cellular components are dismantled within the confines of an intact cell membrane, and rapid ingestion by phagocytic cells prevents local inflammation. A variety of genes have now been identified as positive or negative regulators of apoptosis. Transfection experiments and studies of gene cooperation in viral transformation suggest that full cellular transformation requires not only the deregulation of proliferation, but also the inhibition of concomitant apoptosis programs. The regulation of apoptosis is fundamental to hematopoietic homeostasis. Stem cell renewal is continuously counterbalanced by apoptosis in functionally inactive or terminally differentiated cells. Extensive cell death in developing lymphocyte populations ensures that only cells recognizing non-self antigens are released into the periphery, and the finite lifespan of terminally differentiated cells enables the extensive cell turnover demanded by functional aspects of the hematopoietic system. The requirement of each hematopoietic sub-population for a specific sub-set of survival factors, provides a flexible mechanism for dictating the cellular composition of the mature population and for controlling population size. Surplus cell production and apoptosis are therefore normal features of hematopoiesis. The consequences of deregulated apoptosis are severe. Excessive apoptosis in lymphocyte populations plays a major role in the pathogenesis of acquired immunodeficiency syndrome (AIDS), whereas ineffective apoptosis has been associated with the development of inflammation, autoimmunity and hematological malignancies. The identification of various genetic abnormalities which influence apoptosis in leukaemic cells (e.g., mutant p53, Bcr-Abl and over-expression of Bcl-2), suggests that the acquisition of an anti-apoptotic lesions is an important event in the multi-step evolution of hematological malignancies. In addition, the nature of some leukaemias particularly the chronic leukemias, in which the leukemic cells are nonproliferative and long lived, suggests that anti-apoptotic lesions are early events in the pathogenesis of these diseases. It is likely that the utilization of mechanisms to evade apoptosis would facilitate disease progression in all leukemias and contribute to the development of multi-drug resistance. A better understanding of apoptosis mechanisms in hematopoietic cells, and their exploitation by leukemic cells should be useful in the development of improved cytotoxic regimes.

Modulation of apoptosis with cytokines in B-cell chronic lymphocytic leukaemia

In B chronic lymphocytic leukaemia (B-CLL) non-proliferating peripheral blood (PB) B cells have a long life span in vivo. In cultures, these cells die spontaneously by apoptosis. Interleukin (IL) 4 inhibits spontaneous apoptosis (SA) and promotes survival of B-CLL B cells in vitro. No such effect is observed in PB B cells from normal healthy donors. The anti-apoptotic effect of IL4 is independent of mitogen-induced cell activation but depends on the concentration of IL4. The protective effect of IL4 is specific and it is significantly reduced or abolished with anti-IL4 antibody. Interferon (IFN)-gamma and alpha- IFN also protect B-CLL B cells from apoptosis in vitro. Sera from B-CLL patients have increased levels of IFN-gamma when compared with sera from healthy donors. In addition, B-cells in B-CLL express detectable levels of IFN-gamma mRNA. Other cytokines, namely ILl, IL2, IL6 and IL7 do not affect SA of B-CLL B cells. By contrast, IL5 and antibody to apolipoprotein-1 (APO- 1) receptor increase SA significantly and in a dose-dependent manner. Interleukin 4 protects B-CLL B cells from IL5-, anti(alpha) APO-1- and steroid-induced apoptosis. The mode of action of the cytokines inducing apoptosis or protecting B-CLL B cells from dying is largely unknown. Recently the bcl-2 proto-oncogene has been associated with prolonged cell survival. However, the involvement of bel-2 in spontaneous, cytokine-induced or steroid-induced apoptosis in B-CLL has been controversial. Some authors have reported down-regulation of bcl-2 protein expression in B-CLL B-cells undergoing SA or in steroid-treated cells with IL4 preventing this down-regulation. By contrast, others observed no significant loss of bcl-2 protein expression in steroid-, alpha-APO-1 - and IL5-treated cells when compared with untreated or fresh cells. Also, no correlation between bcl-2 protein expression and protection with IL4 has been reported. In conclusion, in B-CLL IL4, IFN-gamma and alpha-IFN promote the survival of the leukaemic cells. These cytokines may therefore be involved in the pathogenesis of the B-CLL.