Effect of anti-APO1 on spontaneous apoptosis of B cells in chronic lymphocytic leukaemia: the role of bcl-2 and interleukin 4

Autotransplanting of bone marrow-derived mononuclear cells for complete cases of canine paraplegia and loss of pain perception, secondary to intervertebral disc herniation

OBJECTIVES

Severe intervertebral disc herniation causes complete paraplegia and loss of pain sensation in canines. The prognosis is poor, even when decompression surgery is performed immediately after onset. Studies suggest that bone marrow-derived mononuclear cells will regenerate the injured spinal cord and restore neurologic function. This study was conducted to assess the clinical efficacy of bone marrow-derived mononuclear cell autotransplanting in severe cases of canine intervertebral disc herniation.

MATERIALS AND METHODS

Eighty-two dogs (miniature dachshunds) with severe thoracolumbar intervertebral disc herniation were used. All had intervertebral disc herniation accompanied by paraplegia and loss of pain perception. In 36 dogs, bone marrow-derived mononuclear cells were autotransplanted to the lesioned spinal cord immediately after decompression surgery. Bone marrow was collected from the proximal humerus and subjected to density gradient centrifugation to isolate the bone marrow-derived mononuclear cells. The remaining 46 dogs (receiving surgical treatment only) were assigned as controls. Therapeutic efficacy was compared based on the rate of ambulatory recovery.

RESULTS

Ambulatory recovery was observed in 88.9% and 56.5% of animals in the bone marrow-derived mononuclear cells and control groups, and a significant difference was found. No complications were found in bone marrow-derived mononuclear cells group.

CONCLUSIONS

Bone marrow-derived mononuclear cell transplanting revealed a significant increase in the recovery rate and, as has been reported in rats and humans, bone marrow-derived mononuclear cell autotransplanting shows efficacy in canines as well.

Cancer-stromal interactions: role in cell survival, metabolism and drug sensitivity

It has been known for a long time that the interaction between cancer cells and tissue microenvironment plays a major role in cancer development, progression and metastasis. The biochemical aspect of cancer-stromal interactions, however, is less appreciated. This short review article first provides a brief summary of the communications between cancer cells and the tissue microenvironment by direct cell-cell interactions and by soluble factors, and then describes several biochemical pathways that are important for the interaction between stromal and cancer cells with respect to energy metabolism, redox balance, cell survival and drug resistance. The potential therapeutic implications of abolishing stromal protective mechanisms to overcome drug resistance are also discussed.

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.

Intracellular T cell cytokines in patients with B cell chronic lymphocytic leukaemia (B-CLL)

Analysis of cytokine production is a tool to functionally characterise T cells. In this study, spontaneous and polyclonal activation induced cytokine production in T cells were assessed by flow cytometry in patients with B-CLL. Patients with progressive disease had a significantly increased number of T cells spontaneously producing IL-2, IL-4 and GM-CSF as compared to healthy donors and patients with non-progressive CLL, which was not the case for TNF-alpha and IFN-gamma producing T cells. However, no difference in the frequency of T cells producing these cytokines was seen comparing patients with non-progressive disease to control donors. Polyclonal activation of B-CLL T cells in vitro induced an increased proportion of T cells producing these five cytokines in patients as well as in control donors, indicating that T cells in CLL patients might have a relatively well preserved functional capacity. However, the increase in GM-CSF, TNF-alpha and IL-4 producing T cells was more marked in CLL patients than in controls. Furthermore, following activation, a higher frequency of cytokine-producing T cells was noted in patients with progressive disease as compared to those with non-progressive disease. The augmented number of cytokine-producing T cells in CLL may indicate an up-regulated capability of T cells to secrete cytokines, especially in patients with progressive CLL. The increased production of the T cell derived cytokines GM-CSF, TNF-alpha, IL-4 and IL-2 is interesting, as these cytokines have previously been shown to support growth of B-CLL leukaemic cells in vitro and as T cells might specifically recognise the autologous leukaemic B cells in vivo. The findings may suggest a role for T cells in the pathogenesis of B-CLL.

Non-malignant leukocytes delay spontaneous B-CLL cell apoptosis

Malignant B cells from chronic lymphocytic leukemia (B-CLL) patients have a long survival in vivo, although, in culture, they spontaneously die by apoptosis. Here, we analyzed the capacity of accessory leukocytes to modulate apoptosis of B-CLL cells in vitro. To this end, we performed long-term cultures using total mononuclear cells (TMC) from B-CLL patients and TMC depleted from monocytes, NK cells and T lymphocytes (B-CLL cells). In all the patients studied (n = 25) the presence of accessory leukocytes markedly prolonged the survival of B-CLL cells. The anti-apoptotic effect was exerted by monocytes and, to a lesser degree, NK cells, partially through the release of soluble factors. Indeed, accessory leukocytes separated from leukemic cells by semipermeable membranes were still able to prolong B-CLL cell survival. By flow cytometric analysis we found that the protective effect of non-malignant cells was associated with delayed down-regulation of Bcl-2 expression on leukemic cells. By contrast, the expression of Fas and Fas ligand proteins was unchanged in most samples. Our findings suggest that monocytes and NK cells, by delaying leukemic cell apoptosis, may play a role in B-CLL cell accumulation in vivo.

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.

Interleukin 4 content in chronic lymphocytic leukaemia (CLL) B cells and blood CD8+ T cells from B-CLL patients: impact on clonal B-cell apoptosis

B-chronic lymphocytic leukaemia (CLL) clonal B cells are characterized by resistance to apoptosis. We evaluated clonal B cells and blood T cells for interleukin 4 (IL-4) content as IL-4 is able to increase CLL cell resistance to apoptosis. The content of IL-4 in CD8+ T cells of CLL patients (n = 9) ranged from 37% to 63% of the total CD8+ T cells (mean level of 49% +/- 3.4) compared with a range of 5-10% for control CD8+ T cells. Clonal B cells positive for cytoplasmic IL-4 ranged from 1% to 97% (mean value 57.8 +/- 6.9%). CD8+ T cells and clonal B cells secreted detectable levels of IL-4, but only clonal CLL B cells (n = 4) secreted IL-4 in association with increasing cell numbers. Fludarabine (F-ara-AMP, 0.1-100 micromol/ml) was able to downregulate the IL-4 content of CD8+ T cells, but not clonal B-cell IL-4. Culture supernatant from CLL CD8+ T cells decreased the spontaneous apoptotic rate of clonal B cells that was reversed with anti-IL-4 and soluble IL-4 receptor. These findings show that IL-4 is present in the microenvironment of B-CLL. In addition, use of agents that can interfere with IL-4 presentation to clonal B cells can be effective in increasing clonal B-cell apoptosis.

Gamma-linolenic acid induces apoptosis in B-chronic lymphocytic leukaemia cells in vitro

Gamma linolenic acid (GLA) is cytotoxic to many types of human cancer cells. Most chemotherapeutic agents are cytotoxic by inducing apoptosis. We examined the apoptotic activity of GLA on purified B-cells isolated from patients with B-cell chronic lymphocytic leukaemia (B-CLL) and from normal individuals. GLA significantly increased the degree of apoptosis in B-CLL B-cells after 24 hours of culture. The mean percentage of cells undergoing apoptosis when cultured in medium alone (spontaneous apoptosis) was 20% (range: 7 to 31%) (n=25) and in the presence of GLA (5 microg-60 microg) was: 42%-95%. In the presence of GLA 5 microg/ml and dexamethasone the degree of apoptosis was 86% (range: 72 to 100%). GLA induced apoptosis in B-CLL B-cells at a higher level than that observed with normal B-cells at all lower concentrations tested 5, 10 and 15 microg/ml: P=0.045; 0.027 and 0.022, respectively. At 30 microg/ml of GLA, no significant difference in the percentage of cells displaying apoptosis between B-CLL and normal B-cells was observed (P=0.075). GLA induced apoptosis in B-CLL T-cells at both 10 and 30 microg/ml. The degree of apoptosis in normal T-cells with GLA was also significant at the higher concentration of 30 microg/ml. Interleukin 4 (IL4), a viability factor in B-CLL, and vitamin E, an anti-oxidant, protected B-CLL B-cells against GLA (20 microg/ml)-induced apoptosis. These results demonstrate that GLA induces apoptosis in B-CLL B- and T-cells cells in vitro and that they are more susceptible to GLA-induced apoptosis than normal peripheral blood B- and T-cells.

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.

Expression of interleukin-4 in apoptotic cells: stimulation of the type-2 cytokine by different toxins in human peripheral blood mononuclear and tumor cells

BACKGROUND

Immunological reactivity is regulated by T-cell populations (type-1 and type-2 cells) via cytokine secretion, but their influence on apoptosis remains unclear.

METHODS

Intracellular expression of type-1 (interferon [IFN]-gamma) and type-2 (interleukin [IL]-4) cytokines and apoptosis-related molecules (Apo2. 7, Bcl-2 protein) was studied by flow cytometry in human peripheral blood mononuclear cells (PBMC), myeloma (U-266), monocytic (THP-1), and T-leukemia cells (MOLT-4) in response to toxins, which act on different intracellular targets (actinomycin D, cycloheximide, the mistletoe lectins [ML]-1 and ML-3, brefeldin A, staurosporine).

RESULTS

The apoptosis-inducing toxins stimulated intracellular IL-4 expression mainly in PBMC with high expression of the mitochondrial apoptosis marker, Apo2.7, but with decreased level of the anti-apoptotic Bcl-2 protein. Up-regulation of IL-4 coincided with a significant down-regulation of IFN-gamma in CD4(+) and CD8(+) cells. The inhibitor of oxidative phosphorylation, oligomycin, and the caspase inhibitor, z-VAD-fmk, abolished IL-4 expression and DNA fragmentation in the PBMC. Also in the myeloma, monocytic, and T-leukemia cells, IL-4 was mainly observed in the Apo2.7(+) apoptotic cells in response to the toxins.

CONCLUSIONS

We suggest that the different apoptotic toxins activate a common pathway in which IL-4 production plays a yet unknown intracellular role further downstream during apoptosis.

The indispensable role of microenvironment in the natural history of low-grade B-cell neoplasms

Follicular lymphoma (FL) and B-cell chronic lymphocytic leukemia (B-CLL) are paradigmatic examples of lymphoid malignancies in which the relevant biological mechanisms are alterations in the control of apoptosis rather than an exaggerated proliferation. This explains why low-grade B-cell neoplasms still fail to be cured with current approaches. It is becoming increasingly clear that the defective apoptosis of FL and B-CLL has to be ascribed not only to intrinsic defects of the neoplastic cells, but also to extrinsic factors that influence their behavior. Malignant B cells retain the capacity to respond to microenvironmental signals, but have devised a monothematic responsiveness. They have a specific sensitivity to anti-apoptotic signals that favor their survival, whereas they seem to have become insensitive to pro-apoptotic signals. Bystander, nontumoral cells play a fundamental (though not sufficient) role both in the onset and in the progression of these diseases. The survival of leukemic cells appears to be dependent on direct cell-cell contacts. The localization of malignant B cells in bone marrow or neoplastic follicles is not a passive adhesion phenomenon but a crucial step for their survival. Bidirectional malignant lymphocyte-nontumoral cell interactions may lead to the amplification of a microenvironment able to inhibit the apoptosis of neoplastic B cells. The pressure of antigenic selection and the role of the tumor necrosis factor receptor family through the functional survival signal provided by CD40 together with the crippled death signal exerted by CD95 are new prominent characters on the stage.

Accessory cells, cytokine loops and cell-to-cell interactions in chronic lymphocytic leukemia

In addition to the extensive work that has been conducted in order to understand better the biological features of the leukemic population in B-cell chronic lymphocytic leukemia (CLL), over the years considerable interest has been directed towards other related studies that may have important implications for the accumulation of the leukemic clone and for the immunoparesis typical of this disease. In the present review article, we discuss some of these areas of investigation and, in particular, we focus on: (1) the multiple abnormalities recorded within the T and cytotoxic compartment of patients with CLL; (2) cytokine loops occurring in this disease, with particular emphasis on the cytokines that appear to play a more critical role; and (3) the cell-to-cell cross talk that may be actively operational in CLL. These findings will be discussed in relation with the possible implications that each of them have in the expansion and clinical behavior of a disease that is increasingly proving its heterogeneity.

Analysis of Bcl-2 protein expression in chronic lymphocytic leukemia. A comparison of three semiquantitation techniques

A number of studies revealed that high expression of the proto-oncogene bcl-2 correlated with poor prognosis or resistance to chemotherapy in some tumors but predicted a favorable clinical course in other neoplasias. In these studies, however, different immunologic techniques for Bcl-2 detection were used, raising the question of whether the methods applied were comparable. Using chronic lymphocytic leukemia (CLL) cells, the aims of our study were as follows: (1) to determine the reproducibility of Bcl-2 semiquantitation by immunocytochemistry, flow cytometry, or immunoblotting; (2) to study the agreement between results obtained by these methods; and (3) to examine the association between Bcl-2 expression in tumor cells of 99 patients with CLL and clinical parameters. We found that determination of Bcl-2 expression by immunocytochemistry was reproducible and the results were comparable with those of flow cytometry and immunoblotting. In the patient collective examined, Bcl-2 expression did not reflect the extent of tumor mass, but higher levels were found more often in patients with progressive disease.

Apoptosis in B-chronic lymphocytic leukaemia

B-chronic lymphocytic leukaemia (B-CLL) is characterised by the progressive accumulation of monoclonal B cells, which may be the result of several factors leading to extended B-CLL cell lifespan, increased proliferative capacity and diminished cell death. Here we review the implications of several signals mediated by receptors, such as surface IgM, CD6 and CD40, for the B-CLL cell survival, together with data on gene modulation in relation to the apoptosis process in B-CLL cells. We also describe some features of the Fas/FasL system in B-CLL that hypothetically might contribute to the accumulation of leukaemic cells and the progression of the disease, by downregulating the apoptotic response or avoiding the autologous immune response.

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.