Effects of interferon alpha on autocrine growth factor loops in B lymphoproliferative disorders

No Loose Ends: A Review of the Pharmacotherapy of Hairy Cell and Hairy Cell Leukemia Variant

Objective: To review the literature for the treatment of classical and variant hairy cell leukemia (HCL, HCLv), evaluating efficacy, safety, and supportive care involved in the use of purine analogues (PAs), interferon, BRAF inhibitors, monoclonal antibodies, Bruton's tyrosine kinase inhibitors, and new immunotoxin, moxetumomab pasudotox-tdfk (MPT). An electronic literature search of PubMed (January 1958 to January 2019) was conducted in PubMed using the MESH terms hairy cell leukemia, hairy cell leukemia variant, cladribine, pentostatin, rituximab, interferon, vemurafenib, moxetumomab pasudotox. Study Selection and Data Extraction: Studies written in the English language were considered for this article. The significance of each article was determined by authors independently. Data Synthesis: HCL and HCLv are rare B-cell lymphoproliferative disorders, each with distinct biologies. Symptoms are characterized by pancytopenia and splenomegaly. Initial treatments for HCL were suboptimal, leading to minimal and transient remissions. PAs significantly improved outcomes, inducing remission in most patients. However, those with purine-resistant disease were left with a dearth of options, leading to implementation of vemurafenib for BRAF V600 mutated disease and chemoimmunotherapy with rituximab. Despite these advances, some HCL and a majority of HCLv patients experience relapse. Newer targeted agents offer promise for relapsed and refractory patients, including the recently approved MPT. Relevance to Patient Care and Clinical Practice: This review provides a comprehensive update on the pharmacological management of HCL and HCLv for clinicians who encounter patients with this rare disease. Conclusion: HCL and HCLv are uncommon lymphoid neoplasms that lead to a characteristic constellation of symptoms. The emergence of PAs and novel targeted agents have improved the likelihood and durability of responses for these patients.

Antibody-cytokine fusion proteins for treatment of cancer: engineering cytokines for improved efficacy and safety

The true potential of cytokine therapies in cancer treatment is limited by the inability to deliver optimal concentrations into tumor sites due to dose-limiting systemic toxicities. To maximize the efficacy of cytokine therapy, recombinant antibody-cytokine fusion proteins have been constructed by a number of groups to harness the tumor-targeting ability of monoclonal antibodies. The aim is to guide cytokines specifically to tumor sites where they might stimulate more optimal anti-tumor immune responses while avoiding the systemic toxicities of free cytokine therapy. Antibody-cytokine fusion proteins containing interleukin (IL)-2, IL-12, IL-21, tumor necrosis factor (TNF)α, and interferons (IFNs) α, β, and γ have been constructed and have shown anti-tumor activity in preclinical and early-phase clinical studies. Future priorities for development of this technology include optimization of tumor targeting, bioactivity of the fused cytokine, and choice of appropriate agents for combination therapies. This review is intended to serve as a framework for engineering an ideal antibody-cytokine fusion protein, focusing on previously developed constructs and their clinical trial results.

Targeted delivery of interferon-alpha via fusion to anti-CD20 results in potent antitumor activity against B-cell lymphoma

The anti-CD20 antibody rituximab has substantially improved outcomes in patients with B-cell non-Hodgkin lymphomas. However, many patients are not cured by rituximab-based therapies, and overcoming de novo or acquired rituximab resistance remains an important challenge to successful treatment of B-cell malignancies. Interferon-alpha (IFNalpha) has potent immunostimulatory properties and antiproliferative effects against some B-cell cancers, but its clinical utility is limited by systemic toxicity. To improve the efficacy of CD20-targeted therapy, we constructed fusion proteins consisting of anti-CD20 and murine or human IFNalpha. Fusion proteins had reduced IFNalpha activity in vitro compared with native IFNalpha, but CD20 targeting permitted efficient antiproliferative and proapoptotic effects against an aggressive rituximab-insensitive human CD20(+) murine lymphoma (38C13-huCD20) and a human B-cell lymphoma (Daudi). In vivo efficacy was demonstrated against established 38C13-huCD20 grown in syngeneic immunocompetent mice and large, established Daudi xenografts grown in nude mice. Optimal tumor eradication required CD20 targeting, with 87% of mice cured of rituximab-insensitive tumors. Gene knockdown studies revealed that tumor eradication required expression of type I IFN receptors on the tumor cell surface. Targeting type I IFNs to sites of B-cell lymphoma by fusion to anti-CD20 antibodies represents a potentially useful strategy for treatment of B-cell malignancies.

Diminished production of monocyte proinflammatory cytokines during human immunodeficiency virus viremia is mediated by type I interferons

The effect of human immunodeficiency virus (HIV) infection and high-level HIV replication on the function of monocytes was investigated. HIV-positive patients had elevated levels of spontaneous production of some or all of the monocyte proinflammatory cytokines measured (interleukin-1beta [IL-1beta], IL-6, and tumor necrosis factor alpha [TNF-alpha]) compared to uninfected controls. In patients on therapy with high frequencies of monocytes producing proinflammatory cytokines, this frequency was diminished in the context of viremia during an interruption of therapy. Diminished production of proinflammatory cytokines during viremia was restored by culture with autologous CD4(+) T cells or monocytes from an on-therapy time point or lipopolysaccharide (LPS). Microarray analysis demonstrated that diminished monocyte production of proinflammatory cytokines was correlated with elevated type I interferon-stimulated gene transcripts. The addition of exogenous alpha 2A interferon diminished the spontaneous production of IL-1beta, IL-6, and TNF-alpha but did not affect responses to LPS, recapitulating the changes observed for HIV-viremic patients. These results suggest that monocyte function is diminished during high-level HIV viremia and that this effect is mediated by chronic stimulation by type I interferons. This effect on monocytes during viremia may play a role in diminished innate or adaptive immune system functions in HIV-infected patients. In addition, the restoration of these functions may also play a role in some immune reconstitution syndromes observed during initiation of therapy.

B-chronic lymphocytic leukemia cells exert an in vitro cytotoxicity mediated by tumor necrosis factor α

Tumor necrosis factor alpha (TNFalpha) is constitutively produced by B-chronic lymphocytic leukemia (B-CLL) cells and may act as an autocrine factor for their growth and survival. However, very few data are available on the possible cytotoxic effect of TNFalpha produced by B-CLL cells. This study investigated whether B-CLL cells exert in vitro cytotoxicity by TNFalpha and if so, whether this cytotoxicity can be modulated by cytokines. In 8 of 12 patients (66.6%), B-CLL cells in vitro constitutively produced TNFalpha and exerted a TNFalpha-mediated cytotoxicity, evaluated in an 18-h 51Cr release assay, against the TNFalpha-sensitive Jurkat, U937 and K562 cell lines but not against the TNFalpha-resistant Raji cell line. Involvement of TNFalpha in B-CLL cell cytotoxicity is demonstrated by the fact that anti-TNFalpha antibodies strongly inhibited it and supernatants of cytotoxic cultures contained TNFalpha and mediated a completely TNFalpha-dependent cytotoxicity. When the cytotoxic B-CLL cells were stimulated with interleukin (IL)-2 plus IL-12, there was increased TNFalpha mRNA expression, TNFalpha production and TNFalpha-mediated cytotoxicity. All eight patients with cytotoxic leukemic cells had progressive disease and six of these also expressed high levels of ZAP-70 protein. In the other four patients (33.3%), B-CLL cells did not produce TNFalpha in vitro and were not cytotoxic, either spontaneously or after IL-2 plus IL-12 stimulation. Of these four patients, three had stable disease and one had progressive disease. The patient with progressive disease and one of the three with stable disease expressed low levels of ZAP-70 protein. We conclude that a group of B-CLL patients with progressive disease have leukemic B cells able to exert in vitro a TNFalpha-mediated cytotoxicity, which is modulated by cytokines.

Interferon-β-induced activation of c-Jun NH2-terminal kinase mediates apoptosis through up-regulation of CD95 in CH31 B lymphoma cells

Type I interferon (IFN)-induced antitumor action is due in part to apoptosis, but the molecular mechanisms underlying IFN-induced apoptosis remain largely unresolved. In the present study, we demonstrate that IFN-beta induced apoptosis and the loss of mitochondrial membrane potential (delta psi m) in the murine CH31 B lymphoma cell line, and this was accompanied by the up-regulation of CD95, but not CD95-ligand (CD95-L), tumor necrosis factor (TNF), or TNF-related apoptosis-inducing ligand (TRAIL). Pretreatment with anti-CD95-L mAb partially prevented the IFN-beta-induced loss of delta psi m, suggesting that the interaction of IFN-beta-up-regulated CD95 with CD95-L plays a crucial role in the induction of fratricide. IFN-beta induced a sustained activation of c-Jun NH2-terminal kinase 1 (JNK1), but not extracellular signal-regulated kinases (ERKs). The IFN-beta-induced apoptosis and loss of delta psi m were substantially compromised in cells overexpressing a dominant-negative form of JNK1 (dnJNK1), and it was slightly enhanced in cells carrying a constitutively active JNK construct, MKK7-JNK1 fusion protein. The IFN-beta-induced up-regulation of CD95 together with caspase-8 activation was also abrogated in the dnJNK1 cells while it was further enhanced in the MKK7-JNK1 cells. The levels of cellular FLIP (c-FLIP), competitively interacting with caspase-8, were down-regulated by stimulation with IFN-beta but were reversed by the proteasome inhibitor lactacystin. Collectively, the IFN-beta-induced sustained activation of JNK mediates apoptosis, at least in part, through up-regulation of CD95 protein in combination with down-regulation of c-FLIP protein.

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.

Medical approaches and future options in chronic active ulcerative colitis

BACKGROUND

Immunosuppressive therapy employing purine analogues is the therapeutic mainstay in patients with chronic active ulcerative colitis. However, despite therapeutic optimization according to thiopurine-methyltransferase activity or red blood cell 6-thioguanine levels, a substantial proportion of patients does not tolerate azathioprine or 6-mercaptopurine or relapses during this treatment. In the latter multiple therapeutic regimens comprising 6-thioguanine, cyclosporin or tacrolimus, methotrexate, cyclophosphamide, infliximab, interferons, heparin, leukocyte apheresis, and various other regimens might be considered aiming at long-term remission. Many of these treatment forms have only been evaluated in small mostly uncontrolled trials.

OBJECTIVE

In this review existing treatment modalities and future options for patients with chronic active ulcerative colitis will be discussed focusing on immunomodulating approaches.

Interferon in the treatment of hairy-cell leukemia

The introduction of alpha interferon in 1984 initiated a new and exciting turnaround in the treatment of hairy-cell leukemia. Until that time splenectomy was the only known effective therapy for this disease. Interferon proved to benefit hairy-cell leukemia patients with active disease, whether or not they had undergone prior splenectomy. However, most interferon-induced responses were partial and were of relatively short duration. Purine analogues such as cladribine and pentostatin have since been found to be more effective than alpha interferon and, therefore, have now replaced interferon as first-line therapy for hairy-cell leukemia. At the present time, interferon has a relatively limited role in the treatment of hairy-cell leukemia and it is reserved for a group of selected patients who have failed nucleoside analogue therapy. In this chapter, we discuss the efficacy of interferon and its response duration, toxicity and possible mechanism of action in patients with hairy-cell leukemia.

The biology of hairy cells

The evidence that hairy cells are activated clonal late B cells is presented. The largely non-specific (i.e. not confined to hairy-cell leukaemia) chromosome and genetic abnormalities are then described. Next, the features of malignant-cell activation are considered, including the distinctive morphology of hairy cells and their expression of activation-related antigens and activated adhesion receptors. Also, signalling and cytokine production are discussed in the context of malignant-cell activation. It is then demonstrated that many of the distinctive clinicopathological features of hairy-cell leukaemia can be explained in terms of the interaction of the activated malignant cells with other types of cell and tissue matrix. Finally, the biological basis of the hairy cell's unusually high sensitivity to IFN-alpha and nucleoside analogues is discussed.

Response of hairy cells to IFN-alpha involves induction of apoptosis through autocrine TNF-alpha and protection by adhesion

Although hairy cell leukemia is uniquely sensitive to interferon-alpha (IFN-alpha), the biologic basis for this phenomenon remains unclear. Here we examine the effects of IFN-alpha on cultured hairy cells (HCs), taking into account the possible modifying influence of cell adhesion. We make the novel observation that therapeutic concentrations of IFN-alpha kill nonadherent HCs by inducing apoptosis. In keeping with the persistence of HCs in tissues during therapy, such killing was inhibited by integrin-mediated adhesion to vitronectin or fibronectin. Exposure of HCs to IFN-alpha resulted in a marked increase in tumor necrosis factor-alpha (TNF-alpha) secretion. Furthermore, blocking antibodies to TNF-RI or TNF-RII protected HCs from IFN-alpha-induced apoptosis, demonstrating that such killing was mediated by TNF-alpha. In the absence of IFN-alpha, exogenous TNF-alpha did not induce HC apoptosis, showing that IFN-alpha sensitized HCs to the proapoptotic effect of autocrine TNF-alpha. This sensitization to TNF-alpha-induced killing was attributable to suppression of IAP (inhibitors of apoptosis) production known to be regulated by the cytoprotective nuclear factor-kappaB-dependent arm of TNF-alpha signaling. Moreover, engagement of the receptors for fibronectin or vitronectin prevented this IFN-alpha-induced down-regulation of IAPs. Understanding of the signals involved in the combined effects of IFN-alpha and TNF-alpha and abrogation of those induced by integrin engagement offers the possibility of sensitizing other malignant cells to IFN-alpha-induced killing and thereby extending the therapeutic use of this cytokine.

Interferon-alpha 2b and vesnarinone influence levels of tumor necrosis factor-alpha, apoptosis, or interleukin 6 in ESKOL, a hairy cell leukemic cell line. A potential cytokine and oncogene relationship regulating apoptosis is suggested

The in vitro effects of interferon-alpha (IFN) on levels of secreted interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF alpha), and nuclear matrix proteins (NMP) were examined in ESKOL, a B-lymphoblastoid cell line resembling hairy cell leukemia (HCL). IFN enhances differentiation in ESKOL, decreases TNF alpha levels, decreases apoptosis, increases IL-6 levels, and down regulates the expression of several oncogenes. Vesnarinone (Ves), a TNF alpha repressor, lowers TNF-alpha and decreases apoptosis in the same cell line. ESKOL exhibits enhanced apoptosis and reduced B-cell lymphomas (Bcl-2) levels over WIL-2. IL-6 and TNFalpha have been shown to decrease and increase apoptosis in B-cells respectively; however, treatment of ESKOL with these cytokines had no significant effect on apoptosis. We suggest that IFN decreases apoptosis by mechanisms involving enhanced IL-6 and Bcl-2 levels, decreased TNF alpha and the down regulation of apoptotic oncogenes, including c-myc.

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.

CD40 ligand in CLL pathogenesis and therapy

Advances in immunology during the past three decades have facilitated our understanding of the biology of specific lymphoid neoplasms including chronic lymphocytic leukemia (CLL). Investigations in our laboratory have focused on CD40, a critical regulator of B cell survival and differentiation, and its ligand, CD154 (CD40L). We have established that in some cases of CLL the malignant cells express both CD40 and CD154, and on the basis of those observations, proposed a model for CLL tumor growth due to CD40-CD154 interactions within and among the malignant cells, and for the occurrence of autoimmune syndromes in some cases of CLL. Here, we include an update on our studies regarding CD154 expression in CLL, a review of the data regarding the consequences of CD40 engagement in CLL B cells, and a discussion of these findings in the context of the complex and potentially opposite outcomes that have been reported for CD40-mediated signals in CLL. The implications for therapy, such as by impedance to CD154-CD40 interaction using antibody to CD154, or by selective inhibitors of NF-kappa B, are considered.

S-phase induction by interleukin-6 followed by chemotherapy in patients with chronic lymphocytic leukemia and non-Hodgkin's lymphoma

Interleukin-6 (IL-6) has in vitro demonstrated growth regulatory effects on tumor cells from patients with chronic lymphocytic leukemia (CLL) and lymphoma. The proliferation rate of these cells is usually very low and this is thought to be one of the reasons for the lack of a curative potential of cytostatic chemotherapy in CLL and low grade NHL. Recombinant human (rh) IL-6 might increase the in vivo proliferation rate leading to a higher sensitivity for chemotherapy. We tested this hypothesis by administering rhIL-6 to 9 CLL patients and 3 NHL patients in doses of 2.5 micrograms/kg, 5 micrograms/kg and 10 micrograms/kg s.c. daily for 5 days followed by CHOP chemotherapy on the last day of rhIL-6 injection. Six patients had two treatment cycles. The proportion of cells in S-phase was determined by the bromodeoxyuridine labeling index (LI). Three patients achieved a partial remission, one patient had progressive disease and the remaining patients demonstrated no change. Two patients, who received 10 micrograms/kg/day rhIL-6, demonstrated a significant increase in LI, one of these was first observed in the second treatment cycle. A significant decrease was seen in two patients receiving 2.5 micrograms/kg and 5 micrograms/kg respectively. Immunophenotypic assessment demonstrated that rhIL-6 increased the expression of CD20 in all CLL patients with a reversal after cessation of rhIL-6. We conclude that rhIL-6, in the dosage and schedule used in this study, did not increase the proportion of the cells in S-phase and that the growth stimulatory effects of rhIL-6 in CLL in vivo probably are insignificant. However, the role of rhIL-6 in CLL as inducer of increased CD20 expression prior to anti-CD20 antibody treatment remains to be determined.

IFN-alpha stimulates proliferation and cytokine secretion of CD40-stimulated B cell chronic lymphocytic leukemia cells in vitro

Interferon (IFN)-alpha has a therapeutic effect in several B cell malignancies, including low-grade non-Hodgkin's lymphoma (NHL), multiple myeloma, and hairy cell leukemia, whereas its efficacy in the treatment of B cell chronic lymphocytic leukemia (B-CLL) is rather limited. In the present study, we investigated the effect of IFN-alpha on the biologic functions of B-CLL cells, which were stimulated by cross-linking of the CD40 antigen. In cell samples from 16 B-CLL patients, the addition of IFN-alpha to CD40-stimulated purified B-CLL cells caused a significant increase in [3H]thymidine uptake (p < 0.003). In B-CLL cells maximally activated by CD40 cross-linking and interleukin-2 (IL-2)/IL-10, proliferation was not further enhanced or inhibited by IFN-alpha. In contrast, proliferation of normal tonsillar B cells stimulated by the combination CD40/IL-2/IL-10 was significantly inhibited by IFN-alpha. Because B-CLL activation might be enhanced by induction of the autocrine growth factor tumor necrosis factor-alpha (TNF-alpha), we investigated the effect of IFN-alpha on the secretion of B cell tropic cytokines. In fact, IFN-alpha significantly stimulated the secretion of IL-6 and TNF-alpha in CD40-activated B-CLL cells (p < 0.01). Although exogenous addition of TNF-alpha did not influence activation of CD40-stimulated B-CLL cells, neutralization of TNF-alpha by polyclonal antibodies led to a complete inhibition of CD40-mediated proliferation of B-CLL cells, suggesting that enhanced proliferation and increased cytokine production by CD40-activated B-CLL cells are independent IFN-alpha-mediated events. The studies presented here provide evidence that IFN-alpha mediates costimulatory signals in the context of T cell-mediated B-CLL cell activation.

Novel biologic approaches to hematologic malignancies

Biologic agents have made a major impact on the treatment of hematologic malignancies and will continue to play a major role as we better understand their function in normal and malignant cell regulation. The examples provided in this chapter are a brief introduction to the potential of these agents. Many have yet to be used in conjunction with current cytotoxic therapy in these diseases, and perhaps combinations will prove even more successful. This possibility provides substantial ground for further investigation and therapy.

Effects of immunotherapy on experimental immunodeficiency-related lymphoproliferative disease

BACKGROUND

Human lymphokine-activated cells (LAK cells) and interferon alpha (IFN-alpha) have been used clinically in the therapy of posttransplant lymphoproliferative disease (PTLD). However, the efficacy of such therapy has not been extensively tested under controlled experimental conditions.

METHODS

A B-cell line, derived from PTLD tissue and clonally related to the parent lesion, was tested for its response to IFN-alpha in vitro. The effects of LAK cells and IFN-alpha therapy were examined in a severe combined immunodeficiency disease (SCID) mouse model in vivo.

RESULTS

The PTLD cell line studied showed a 30% decrease in the rate of growth upon incubation with 500 U/ml of IFN-alpha. This in vitro response was also reproduced in vivo, in tumor therapy studies conducted in SCID mice. The magnitude of this inhibitory effect in vivo was a function of tumor burden and dose of IFN-alpha. In parallel experiments, LAK cells reduced the tumorigenicity of a lymphoblastoid cell line derived from the peripheral blood of a patient with PTLD, and prolonged the survival of SCID-beige mice with established lymphoproliferative disease. In contrast with two prior studies, in which the use of autologous cytotoxic T cells was found to be necessary, we found the administration of third-party non-HLA-matched LAK cells also to be effective in reducing tumor burden.

CONCLUSIONS

These observations demonstrate the efficacy of immunotherapy for lymphoproliferative disease under controlled experimental conditions, and validate currently ongoing efforts exploring the utility of such therapy in the clinical setting.

In vitro culture of B-lymphocytes derived from Epstein-Barr-virus-associated posttransplant lymphoproliferative disease: cytokine production and effect of interferon-alpha

Epstein-Barr-virus-associated posttransplant lymphoproliferative disease ranges from transient lymphadenitis to aggressive lymphoma. This study characterizes an in vitro model to study the pathogenesis of this disease with a cell culture system. Five B-cell lines derived from posttransplant lymphoproliferative disease tissue were characterized with regard to immunophenotype, karyotype, molecular genetics, cytokine production, and growth regulation. All cell lines expressed CD19, CD21, CD22, CD43, and CD77, but not CD10 antigens. Immunoglobulin light chain restriction was seen in four of five cell lines, and cytogenetic abnormalities were demonstrable in three of the five. Cells proliferating in culture contained multiple Epstein-Barr virus episomes and showed lytic viral replication. All cell lines produced tumor necrosis factor-beta and interleukin-10 without evidence of autocrine growth regulatory loops involving these cytokines. No evidence of IL-1 alpha, IL-2, IL-4, IL-5 or IL-6 production was found by reverse transcriptase polymerase chain reaction. Adding 500 U IFN-alpha/ml to the culture medium resulted in 30% inhibition of [3H]thymidine incorporation.

Human Cytomegalovirus-Associated Immunosuppression Is Mediated Through Interferon-α

Human cytomegalovirus (HCMV) infections are commonly associated with a generalized immunologic hyporesponsiveness. The present study was designed to evaluate the potential mechanisms of HCMV-associated immunosuppression. In our initial experiments, monocytes in peripheral blood mononuclear cells (PBMCs) exposed to cell-free HCMV appeared morphologically less differentiated than monocytes in PBMCs exposed to a mock preparation. These morphologic changes were closely correlated with a decrease in monocyte oxidative activity and occurred under noncytopathic conditions. HCMV-associated suppression of monocyte differentiation did not require virus replication, occurred in PBMCs from either HCMV seropositive or seronegative donors, and required HCMV interaction with the nonadherent cells. An HCMV-induced soluble factor was found to not only reproduce the identical changes in purified monocytes but to inhibit the phagocytic activity of these cells. Additionally, the HCMV-induced factor accounted for a generalized defect in the ability of PBMCs to proliferate in response to mitogens and recall antigens. In subsequent experiments, interferon-α (IFN-α) was identified as the soluble factor involved in these immunosuppressive effects. Thus, PBMCs, when exposed to HCMV, produce a soluble factor, identified as IFN-α, that appears to be an important mediator of immunosuppression associated with HCMV infection.

Human cytokines suppress apoptosis of leukaemic CD5+ B cells and preserve expression of bcl-2

Leukaemic CD5+ B cells obtained from B cell chronic lymphocytic leukaemia (B-CLL) patients rapidly undergo apoptosis during in vitro culture. This is associated with down-regulation in expression of bcl-2. Spontaneous apoptosis of these cells contrasts their enhanced longevity in vivo and suggests that apoptosis-inhibitory factors may be responsible for the accumulation of leukaemic cells in B-CLL. The effect of different cytokines on apoptosis and bcl-2 expression was examined in six populations of leukaemic CD5+ B cells. Consistent with previous data, IL-4 and IFN-gamma suppressed apoptosis in 6/6 and 5/6 cell populations, respectively. Interestingly, the ability to suppress apoptosis in leukaemic CD5+ B cells was also found to be a property of IL-2, IL-6, IL-13 and TNF-alpha. In the presence of these cytokines, 10-40% more viable cells were detected, compared with unstimulated cultures. Enhancement of cell viability and suppression of apoptosis were associated with a delay in down-regulation of bcl-2. These results suggest a role for autocrine and paracrine growth factors in the pathogenesis of B-CLL, and indicate that cytokines which prevent apoptosis in vitro may be targets for treating this malignancy.

Differential human multiple myeloma cell line responsiveness to interferon-alpha. Analysis of transcription factor activation and interleukin 6 receptor expression

Although IFN-alpha is commonly used as maintenance treatment for multiple myeloma patients, its effectiveness is varied. In this study, we have used a panel of IL-6 responsive myeloma cell lines that vary remarkably in responsiveness to IFN-alpha. Three cell lines were growth arrested by IFN-alpha; however, IFN-alpha significantly stimulated growth of the fourth cell line, KAS-6/1. Our studies have focused on elucidating the mechanism of differential IFN-alpha responsiveness. First, we have shown that IFN-alpha-stimulated growth of the KAS-6/1 cells did not result from induction of autocrine IL-6 expression. Second, analysis of Stats 1, 2, and 3 and IFN regulatory factor-1 (IRF-1) and IRF-2 activation failed to reveal differences between the IFN-alpha growth-arrested or growth-stimulated cells. Third, although IFN-alpha treatment of the IFN-alpha growth-inhibited cell lines reduced IL-6 receptor (IL-6R) expression, IFN-alpha also reduced KAS-6/1 IL-6R expression. Finally, although IFN-alpha treatment reduced IL-6R numbers on each cell line, analysis of Stat protein activation revealed that the receptors were still functional. We conclude that myeloma cell responsiveness to IFN-alpha is heterogeneous and that mechanisms of IFN-alpha-mediated growth inhibition other than IL-6R downregulation must exist in myeloma. Identification of these mechanisms may allow development of agents that are more universally effective than IFN-alpha.

Serum levels of TNF, IL-6 and sCD23 correlate with changes in lymphocyte count in patients with B-cell chronic lymphocytic leukaemia receiving interferon-alpha therapy

The control of cell growth and differentiation in B-cell malignancies may be regulated by the autocrine production of cytokines, several of which have been implicated in the growth and survival of B-cells. The effect of interferon-alpha (IFN) therapy in these disorders may be to disrupt autocrine growth or survival loops. We have measured levels of circulating IL-1b, IL-6, TNF-a and soluble CD23 (sCD23) in 8 patients with Binet stage A B-cell chronic lymphocytic leukaemia (B-CLL) receiving IFN therapy, and compared these with changes in the lymphocyte count following IFN therapy. Two patients developed anti-interferon antibodies while on IFN therapy, and in both them, the changes in lymphocyte count correlated significantly with the titre of anti-interferon antibodies, as well as serum levels of IL-6, TNF-a and sCD23. In one patient there was significant correlation with levels of IL-1b. One patient, who stopped and restarted IFN therapy, demonstrated correlation between lymphocyte count and levels of IL-6 and sCD23. In a further two patients, there was correlation with levels of sCD23 alone, while the remaining three patients showed no correlation between lymphocyte count and the serum cytokines measured. These results suggest that IFN therapy may alter levels of circulating cytokines in some CLL patients and that these effects may be associated with disease progression.

Effects of interferon-alpha and -gamma on B cell differentiation in macroglobulinemia

We previously showed that clonal blood B cells from patients with macroglobulinemia spontaneously differentiate in vitro to plasma cells via an IL-6 autocrine pathway. Here we investigate whether interferon-alpha or -gamma would interfere with B cell differentiation either in patients with IgM gammopathy of undetermined significance (IgM-MGUS) or Waldenström's macroglobulinemia (WM). A 65% inhibition of in vitro B cell differentiation was noted in 8 of 10 patients in the presence of either interferon-alpha or -gamma. Cells from 4 patients (3 IgM-MGUS and 1 WM) were susceptible to both types of interferon while B cell differentiation from 4 patients (3 IgM-MGUS and 1 WM) was inhibited only by one type of interferon. During in vitro culture, IL6 synthesis was unaffected by the presence of interferon alpha or gamma in the 8 cases studied. Likewise, no modulation of the constitutive B cell IL6-R expression from 6 patients studied (4 WM and 2 IgM-MGUS) was observed. These data indicate that interferons did not modify the differentiation of B cells in macroglobulinemia via modulation of the IL6-IL6-R pathway. This is in contrast with the mode of action of interferons in other lymphoid malignancies such as multiple myeloma or chronic lymphocytic leukemia where they directly modulate IL6-production and/or IL6-R expression.

Interleukin-6 inhibits apoptosis and tumour necrosis factor induced proliferation of B-chronic lymphocytic leukaemia

There is now good evidence that tumour necrosis factor [TNF] stimulates DNA synthesis of B-chronic lymphocytic leukaemia (B-CLL) cells. The malignant clone produces TNF, and addition of exogenous TNF up-regulates the TNF mRNA in B-CLL cells. Interleukin-6 (rIL-6) may also be important in this growth loop. We studied the interaction of TNF and IL-6 in the regulation of DNA synthesis (3H-TdR uptake), cytokine release and cell survival in CLL cells in vitro. Addition of TNF (100 U/ml over 5 days) enhanced DNA synthesis from 718 +/- 284 (mean cpm +/- SE) to 2730 +/- 545 compared to cells cultured in medium alone (n = 16, p < 0.01). TNF-alpha induced DNA synthesis was inhibited in all cases studied by the addition of anti-TNF monoclonal antibody (5 micrograms/ml) to cell cultures. Spontaneous IL-6 protein release was enhanced in the presence of TNF (100 U/ml and 250 U/ml) by CLL cells at 48 hours of culture 143.6% and 172% (p < 0.05, n = 6). At 120 hours of culture, the increase was 323% and 412.5% (4 of 7 cases) of the control respectively. IL-6 (100 U/ml or greater) increased spontaneous DNA synthesis (3H-TdR uptake) but, in the presence of high concentrations of TNF-alpha, inhibited TNF induced DNA synthesis in a dose dependent manner. Cell survival was reduced in the presence of anti-IL-6 mAb, while IL-6 was able to protect CLL cells from spontaneous apoptosis. These results suggest that IL-6 in an autocrine manner may inhibit DNA synthesis but prolongs survival in CLL cells. Increased serum IL-6 levels were detected in 27 of 50 cases of CLL, the mean level being significantly higher in Rai Stage III and IV cases compared to Rai Stage O-II cases.

Deregulation of protein synthesis as a mechanism of neoplastic transformation

Early research on the cell cycle revealed correlations between protein accumulation and cell proliferation. In this review, I describe the data showing that abnormality of cell growth and tumor development are dependent upon oncogene-induced increases in the levels and activity of factors that determine the rate of protein synthesis. It is proposed that the establishment of a vicious circle, namely oncoproteins-->increase in translation-->oncoproteins, is a major biological mechanism that fuels neoplastic growth. The constitutively high rates of protein synthesis and accumulation of proteins, including those necessary for DNA replication and mitosis, would drive cells to excessive proliferation.

Growth factors can protect B-chronic lymphocytic leukaemia cells against programmed cell death without stimulating proliferation

The proliferation and survival of B-chronic lymphocytic leukaemia (B-CLL) cells may be regulated by autocrine growth factor loops. Furthermore, it has been suggested the reduction in lymphocytosis following therapy with interferon-alpha may be associated with the interruption of autocrine growth factor production. We have therefore examined the effects of a number of cytokines on the proliferation of B-CLL cells, and also on the regulation of programmed cell death, and the role of interferon-alpha in these systems. In the ten patients studied, neither interferon-alpha alone or together with either interferon-gamma, IL1, IL4, IL6, TNF, or serum containing high levels of soluble CD23 was able to induce proliferation of B-CLL cells. Incubation with TPA or IL2 resulted in variable proliferative responses. Co-incubation with interferon-alpha enhanced TPA-induced proliferation in 4 cases, but reduced IL2-induced proliferation in all cases studied. In contrast, all the cytokines studied were able to protect B-CLL cells against programmed cell death, both spontaneous and that induced by hydrocortisone, with the exception of TNF. These data suggest a role for interferon-alpha in disrupting autocrine survival pathways rather than inhibiting proliferation.

CD27-CD70 interaction: unravelling its implication in normal and neoplastic B-cell growth

Members of the Tumour Necrosis Factor-Receptor (TNFR) family play an essential role in the control of lymphoid cell growth and differentiation. The ligand of one of its lymphoid-specific members, CD27, was recently characterized as CD70, a type II transmembrane molecule with homology to TNF that is expressed on activated T and B cells. Ligation of CD27 by its natural ligand generates a potent costimulatory signal for cytokine production and proliferation of activated T cells. In contrast to normal B cells, where CD27 expression is confined to germinal centre cells and to a small subset of circulating B lymphocytes, CD27 expression is found on a large array of distinct B-cell neoplasia. Here, we review recent data on the expression and function of TNFR family members on normal and malignant lymphocytes and propose a role for CD27-CD70 interaction in B-cell development.

Prospective evaluation of interferon-alpha in treatment of chronic active Crohn's disease

Several case reports suggested good effects of interferon-alpha in patients with Crohn's disease. In addition, a decreased production of interferon-alpha in Crohn's disease has been shown in vitro. Treatment with interferon-alpha may activate intestinal natural killer cells and down-regulate the overproduction of inflammatory cytokines like interleukin-6 in Crohn's disease. To evaluate the clinical efficacy of interferon-alpha, we treated 12 patients with a chronic active course of Crohn's disease with recombinant human interferon-alpha prospectively for 24 weeks. Prednisolone was continuously tapered and discontinued at week 12. The end point of the study was the prevention of worsening of clinical symptoms defined with the Crohn's disease activity index and was monitored by acute-phase proteins, interleukin-6 serum concentrations, and endoscopy. The biochemical activity of interferon-alpha was measured by 2',5'-oligo adenylate serum levels. The end point of the study was reached in four patients (33%). In these patients the final Crohn's disease activity index was above 150, which means that they did not achieve clinical remission. All other patients (66%) did not respond to interferon-alpha and had to be withdrawn prematurely. Interferon-alpha did not show any beneficial effect on interleukin-6 or acute-phase protein concentrations and on endoscopic activity. The 2',5'-oligo adenylate levels continuously increased during interferon therapy. Considerable side effects were noted. These results fail to demonstrate a therapeutic role of interferon-alpha in chronic active Crohn's disease.

Interferon-alpha activates cytotoxic function but inhibits interleukin-2-mediated proliferation and tumor necrosis factor-alpha secretion by immature human natural killer cells

Natural killer (NK) cells play an important role in host defense mechanisms against infection and neoplasia. Interferon-alpha (IFN-alpha) has been shown to activate NK cells and to augment their cytotoxic activity, albeit its role in the maturation pathway of NK cells has not been elucidated. The present study examined whether IFN-alpha activates the immature NK subset (Free cells) to become cytotoxic and also ascertained whether IFN-alpha uses the same pathway of activation as that mediated by interleukin-2 (IL-2). Incubation of sorted Free cells overnight with IFN-alpha resulted in augmentation of their cytotoxic function against NK sensitive target cells. The enhanced cytotoxic activity was not accompanied by a new recruitment of NK-target binder cells but by an increase in the frequency of killer cells in the conjugate fraction. Activation of the Free subset by IFN-alpha resulted in upregulation of CD69, CD11b, and CD2 surface expression and stimulated secretion of IFN-gamma. Unlike IL-2, IFN-alpha did not stimulate the Free cells to proliferate or secrete TNF-alpha and activation of cytotoxicity and modulation of surface antigens by IFN-alpha were independent of TNF-alpha. The failure of IFN-alpha to stimulate secretion and proliferation by Free cells appeared to be mediated by negative signals. This was corroborated in experiments demonstrating that when Free cells were cultured with both IFN-alpha and IL-2, a significant inhibition was observed for both the IL-2 dependent secretion of TNF-alpha and proliferation. These results demonstrate that IFN-alpha serves as both an activator and a regulator of NK function. Further, activation of the immature Free NK cells by IL-2 and IFN-alpha proceeds by TNF-alpha- dependent and independent pathways, respectively. The findings also support our contention that the mechanism of activation of the cytotoxic machinery of NK cells is not linked to the mechanism of activation of cytokine secretion and/or proliferation.

Disruption by interferon-alpha of an autocrine interleukin-6 growth loop in IL-6-dependent U266 myeloma cells by homologous and heterologous down-regulation of the IL-6 receptor alpha- and beta-chains

IL-6 is an autocrine growth factor for U266 myeloma cells and their growth is inhibited by IFN-alpha or IL-6 mAb. We asked, therefore, whether IFN-alpha-induced growth inhibition involved IL-6. IFN-alpha and mAb against IL-6, the IL-6R alpha-(gp80) or beta-chain (gp130) potently inhibited U266 cells. Remarkably, this effect occurred despite IFN-alpha-augmented secretion of endogenous IL-6. However, examining the IL-6R revealed that IFN-alpha drastically curtailed expression of the IL-6R alpha- and beta-chain. This effect occurred on two different levels (protein and mRNA) and by two different mechanisms (directly and indirectly through IL-6). First, IFN-alpha, but not IL-6, greatly decreased gp80 and, to a lesser extent, gp130 mRNA levels which resulted in a loss of IL-6 binding sites. Second, IFN-alpha-induced IL-6 predominantly down-regulated membrane-bound gp130. IFN-alpha-mediated decrease of gp80 levels was not detected on IL-6-independent myeloma (RPMI 8226) or myeloid cells (U937). We conclude that IFN-alpha inhibited IL-6-dependent myeloma cell growth by depriving U266 cells of an essential component of their autocrine growth loop, a functional IL-6R.

The potential role of cytokines in the pathogenesis of Epstein-Barr virus associated post-transplant lymphoproliferative disease

Post-transplant lymphoproliferative disease (PTLD) is a complication of Epstein-Barr virus infection occurring in immunosuppressed transplant recipients. Non-clonal lesions with a polymorphous histology have the potential of regressing, if the degree of immunosuppression is reduced, thereby giving the immune system a chance to recuperate. In contrast, clonal tumors with a monomorphous histology portend a bad clinical outcome. This review summarizes evidence that the biological behavior of PTLD may be predicated on intercellular interactions involving multiple cytokines. With further investigations to clarify the nature of these interactions, it should be possible to design rational strategies for the cytokine therapy of human PTLD.

Interferon-alpha-2b downregulation of oncogenes H-ras, c-raf-2, c-kit, c-myc, c-myb and c-fos in ESKOL, a hairy cell leukemic line, results in temporal perturbation of signal transduction cascade

ESKOL, a B-lymphoblastoid cell line consisting of late differentiated cells, resembles hairy cell leukemia (HCL). It is pseudodiploid with a deleted 7q and an unbalanced translocation between chromosomes 4 and 6. It was screened by Northern hybridization for oncogenes, including H-ras, c-raf-2 (c-raf1p1), c-kit, c-myc, c-myb, c-fos, Fim-1, c-jun, ski, and c-mos, which are believed to contribute to B-cell differentiation and maturation. Interferon-alpha-2b (IFN) downregulates the expression of H-ras, c-raf-2, c-kit, c-myc, c-myb, c-fos, as determined by Northern hybridization of RNA isolated from cells harvested at time points during a 30 h time course. Downregulation of oncogenes H-ras, c-raf-2, c-kit, whose proteins are associated with cell surfaces or are cytosolar transducers, occurs before those oncogenes c-myc, c-myb, and c-fos, whose products are DNA binding proteins. This suggests a temporal perturbation of signal transduction by IFN. No change in oncogene expression occurred in non-treated cells nor were these oncogenes expressed in the non-transformed B-lymphoblast cell line, Wil-2, under the same treatment regimen. The basis for the IFN perturbation is not understood; yet the role of these oncogenes as signal transducers in differentiation and proliferation of human hematopoietic progenitors is unfolding, and ESKOL is an excellent system in which to study this phenomenon.

Interleukin-6 production in B-cell neoplasias and Castleman's disease: evidence for an additional paracrine loop

Functioning as a B-cell growth and differentiation factor, interleukin-6 (IL-6) may play an important role in the pathophysiology of B-cell tumors. The capacity for IL-6 secretion was evaluated in 58 patients with various B-cell leukemias/lymphomas and in four patients with Castleman's disease (CMD). Cell populations from various sites including peripheral blood, bone marrow, lymph nodes, and osteolytic bone lesions were cultured and tested for spontaneous or IL-1 beta/TNF alpha-induced IL-6 production in a sensitive bioassay. No significant IL-6 levels were released by the tumor cells in any of the B-cell leukemias or lymphomas tested, including hairy cell leukemia (HCL) and B-cell chronic lymphocytic leukemia (B-CLL). In contrast, purified malignant plasma cells were found to secrete IL-6, strengthening the idea that an autocrine pathway for growth regulation in multiple myeloma (MM) exists. For the first time, in several patients with CMD, peripheral blood cells were shown to produce extremely high levels of IL-6, the pathogenetic significance of which remains to be elucidated. However, similar observations were very occasionally made in MM patients. Therapy with corticosteroids strongly inhibited this IL-6 production. These data provide evidence for autocrine and possibly an additional paracrine regulatory loop in plasma cell neoplasias and CMD.

Morphologic and immunophenotypic characterization of a cell line derived from liver tissue with Epstein-Barr virus associated post-transplant lymphoproliferative disease

A B-cell line was established from the liver of an 11-yr-old boy with Epstein-Barr virus (EBV)-associated post-transplant lymphoproliferative disease (PTLD). The cells were morphologically heterogenous, CD10 (CALLA) negative, and expressed several B-cell antigens, including CD23, in a manner reminiscent of lymphoblastoid cell lines (LCLs) reported in the literature. However, the cells also showed expression of the CD77 antigen, carried a 14q32+ chromosomal anomaly, and showed IgM-kappa immunoglobulin isotype restriction immediately after their outgrowth in culture. These latter properties are typically associated with Burkitt's lymphoma cell lines rather than LCLs. Aberrant expression of the L60 antigen on these B-cells was found as additional evidence of altered growth regulation in these cells. EBV infection was demonstrated by the abundant expression of EBNA-2 and LMP viral antigens in culture. The cell line described should be useful in planning in vitro experiments designed to understand the factors that modulate the growth of PTLD in vivo.

Interleukin 1 (IL-1 alpha and IL-1 beta) induces differentiation/activation of B cell chronic lymphoid leukemia cells

The effect of interleukin 1 (IL-1) was studied on leukemic cells from 12 patients with B cell chronic lymphoid leukemias including two cases of hairy cell leukemia (HCL), two cases of HCL-variant (HCL-V), one case of prolymphocytic leukemia (PLL), and seven cases of chronic lymphocytic leukemia (CLL). In most cases, IL-1 induced differentiation characterized by increments of sIg gamma+, sIg mu+ and PCA-1+ cells, and a decrement of CD5+ cells, and activation characterized by increments of CD23+ and HC2+ cells, but induced the proliferation of leukemic cells only in two HCL-V cases. Among these effects, increment of sIg+ cells was observed more frequently in non-CLL (4/5 cases) than in CLL (2/7 cases), and increments of sIg gamma+, CD23+ and PCA-1+ cells were induced more frequently by IL-1 beta than by IL-1 alpha. These results suggest that IL-1, especially IL-1 beta, plays a significant role in the differentiation and activation of leukemic cells, but has only a minor role as an extrinsic/leukemic cells in B cell chronic lymphoid leukemias, particularly those with more mature cells such as PLL and HCL.

TNF receptors in chronic lymphocytic leukemia

Two transmembrane receptors for tumor necrosis factor (TNF) with different molecular weight, 55 kD (p55) and 75 kD (p75), have been identified. In addition, the extracellular part of both receptors are shedded by proteolytic cleavage and exist as soluble receptors which bind to TNF in plasma and other biological fluids. Normal B cells produce TNF and express TNF receptors (R), mainly p75, upon stimulation. TNF costimulates DNA synthesis via the p75 receptor in normal B cells. The B cells from patients with chronic lymphocytic leukemia (CLL) produce TNF and have the capacity to express both receptor types. Also in malignant B cells the p75 receptor is dominant. TNF induce DNA synthesis in CLL cells via both receptors. CLL patients have elevated serum levels of soluble (s) TNFR and this is more pronounced in advanced disease. In conclusion, there is considerable support for TNF as an autocrine growth factor in CLL. However, the net effect of TNF is determined by the quantitative relationship between TNFR on the cell surface, TNF in plasma and sTNFR in plasma, and the affinities between TNF-p55 and TNF-p75. Due to increasing serum levels of sTNFR the significance of TNF as a growth factor is probably less important in advanced disease.

Serum levels of tumour necrosis factor-alpha in patients with B-cell chronic lymphocytic leukaemia

Serum levels of tumour necrosis factor-alpha (TNF-alpha) have been evaluated in the peripheral blood of 91 patients with B-cell chronic lymphocytic leukaemia (B-CLL), and have been correlated with the clinical stage (according to Rai's staging system) and relevant haematological and immunological data. Increased values were detected, compared to 36 normal age-matched controls (36 pg/ml +/- 5 versus 0.11 pg/ml +/- 0.08; P < 0.05). An increase of TNF-alpha serum levels was observed in all stages including stage 0, with a progressive increase in relation to the stage of the disease. A significant relationship between serum TNF-alpha levels and the number of circulating monocytes (P < 0.002) and an inverse correlation with the level of the haemoglobin (P < 0.001) was established, as defined by the Pearson's correlation test. In contrast, no correlation was observed between TNF-alpha serum levels and the other parameters taken into account, including the white blood cell and platelet counts, the absolute number of peripheral blood (PB) lymphocytes, CD5+ B lymphocytes, CD57+ lymphocytes, serum levels of lactic dehydrogenase, total serum immunoglobulins and the serum levels of IgG, IgA and IgM. These data suggest that, in addition to the B-CLL neoplastic cells, the PB monocytes may be involved in the release of TNF-alpha.

TNF-alpha induces spreading of B-CLL via the CD11c/CD18 molecule

Activation of malignant B cells can lead to extensive morphological changes of these cells. A combination of PMA and TNF-alpha can induce adherence of purified B-CLL cells, which acquire a dendritic cell-like appearance. This phenomenon that we have termed spreading, is accompanied by upregulation of expression of both beta 1 and beta 2 integrin molecules. Spreading was inhibited by the addition of antibodies against CD18 or CD11c. In other B cell malignancies (HCL and NHL), morphological changes could be induced by PMA in the absence of TNF-alpha. Culturing in the presence of prednisolone resulted in an inhibition of spreading, most likely mediated via a down regulation of CD18 and CD11c expression. These data indicate that the CD11c/CD18 complex might be important for the adhesive properties of B cells.

Cytokines and intracellular signals involved in the regulation of B-CLL proliferation

Cytokines play an important role in the regulation of both normal and malignant B cells. In this paper we give a brief overview of the major cytokines involved in the regulation of B-CLL proliferation. In vitro experiments have indicated that there is an antagonistic interaction between TNF-alpha as a growth-enhancing factor and IL-4, which inhibits the growth of B-CLL. We have extended these findings with recent experiments on the intracellular signals which might be involved in these processes. We show that increased levels of intracellular cAMP dose-dependently inhibit the TNF-alpha-induced proliferation of B-CLL. On the basis of these results, we propose a model for the signals involved in the regulation of B-CLL proliferation. The implications for possible new ways of treatment are discussed.

Interleukin-6 functions as an intracellular growth factor in hairy cell leukemia in vitro

The role of interleukin-6 (IL-6) in the growth of B cell derived hairy cell leukemia (HCL) was characterized. Purified hairy cells (HCs) did not increase DNA synthesis in vitro in response to exogenous IL-6; however, they expressed IL-6 receptor (IL-6R) mRNA and bound directly fluorochrome labeled IL-6. IL-6 mRNA was not detectable in tumor cells by Northern blotting, but was evident using PCR amplification. Although intracytoplasmic IL-6 protein was not demonstrable, HCs did secrete low levels of IL-6. Neutralizing antibody to IL-6 did not inhibit HC DNA synthesis. Since tumor necrosis factor (TNF) is a growth factor for HCL, we determined whether the TNF effect could be IL-6-mediated. TNF markedly augmented in vitro DNA synthesis by HCs. TNF did not alter IL-6R expression or IL-6 binding; however, IL-6 mRNA and IL-6 protein were detectable after 3-d culture of HCs with TNF. In addition, IL-6 secretion by HCs was markedly augmented by TNF. Finally, although neither IL-6 nor anti-IL-6 antibody altered TNF-induced DNA synthesis by HCs, IL-6 antisense oligonucleotide inhibited TNF-induced DNA synthesis and IL-6 secretion by HCs. Therefore, IL-6 does not directly affect the growth of HCL, but rather mediates TNF-induced DNA synthesis via an intracytoplasmic mechanism.

Transcriptional and post-transcriptional regulation of IL-1 beta, IL-6 and TNF-alpha genes in chronic lymphocytic leukaemia

The present study was designed to define the mechanisms of interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6) and tumour necrosis factor (TNF-alpha) gene regulation in chronic lymphocytic leukaemia of B cell origin (B-CLL). By nuclear run-on analysis, all B-CLL cases displayed high levels of nuclear transcription of the IL-6 and TNF-alpha genes, whereas IL-1 beta gene transcription was only barely detectable. Upon in vitro culture for 1 h, B-CLL cells from different patients were substantially heterogeneous in terms of expression of steady state mRNA levels of IL-1 beta, IL-6 and TNF-alpha even though the pattern of nuclear transcription of these cytokines was only marginally affected by in vitro culture. mRNA stability was then examined and cytokine gene transcripts showed a half life of more than 2 h in cultured B-CLL cells and treatment with cycloheximide (CHX) did not affect cytokine transcript levels in B-CLL cells. These results indicate that: steady state levels of each mRNA do not reflect the rate of nuclear transcription of these cytokines in fresh or cultured B-CLL cells, that purification and in vitro culture of leukaemic cells may amplify cytokine gene expression in B-CLL, and that cytokine gene transcripts are relatively stable in B-CLL.

The effect of cytokines on cultured mononuclear cells from patients with B cell chronic lymphocytic leukemia

In the past 5 years a number of cytokines have been identified that control B cell development, proliferation, and maturation. The role of such cytokines in the evolution, pathophysiology, and treatment of B cell malignancies is an area of great interest. The in vitro response of freshly isolated peripheral blood mononuclear cells from patients with B cell chronic lymphocytic leukemia (B-CLL) and a high white cell count, to four cytokines, IFN-alpha, IFN-gamma, IL-2 and TNF, was studied. No culture condition or cytokine resulted in a significant increase in cell number over 4 days, cells survived better in autologous serum than in heat inactivated foetal calf serum, and a small but significant increase in blast cells was seen when the cells were cultured in IL-2. There was a discrepancy between uptake of thymidine and increase in cell number which can be explained by the low labelling index of these cultures and the fact that cells can incorporate [3H]-thymidine without going into mitosis. The majority of cultures produced biologically active TNF at levels ranging from 1 to 40 pg/ml. In IFN-alpha treated cultures TNF levels were decreased. Cultures contained biologically active IL-6 at levels ranging from 2 to 2800 U/ml. IL-6 production was not influenced by other cytokines. Thirteen of 28 patients had detectable IL-6 in their serum, but in cells lysed no more than 2 h after removal from the patient, message for IL-6 could not be detected by Northern blotting. Cells also failed to express IL-1 beta mRNA but seven of eight patients had low levels of TNF message. Preliminary data using in situ hybridization techniques revealed that whilst no mRNA for IL-6 was detected, TNF and IL-1 beta mRNA were detected in a minority of mononuclear cells.

Control of human B cell tumor growth in severe combined immunodeficiency mice by monoclonal anti-B cell antibodies

Severe combined immunodeficiency (scid) mice develop EBV (+)B cell tumors after infusion of EBV(+)B cells or of B cells and EBV. In this study, scid mice were infused with B cell lines derived from three patients who developed a B lymphocyte proliferative disorder after bone marrow or organ transplantation. Intraperitoneal injection of 5 x 10(6) B cells induced tumor growth in all mice, leading to death within 60 d. Human B cells were identified in spleen and bone marrow by means of immunofluorescence or EBV genome amplification, and human IgM was detected in serum. Infusion of murine monoclonal antibodies specific for human B cell membrane antigens CD21, CD24, and CD23 was effective in 80% of animals, against two of the three cell lines preventing tumor development or inducing remission according to the time of treatment. The effect was antibody dose dependent and was optimal with four intravenous infusions of at least 0.1 mg 4 d apart. Human IgM in serum and human B cells in spleen and bone marrow became undetectable when peritoneal tumors regressed completely. Infusions of IgG1 isotype-matched anti-CD4 antibody or anti-CD3 antibody had no effect. Tumors developed or recurred in 50% of these animals injected with one of the B cell line 3 mo after treatment was stopped. The same anti-CD21 and anti-CD24 antibodies had been used to treat the three patients, and shown similar degrees of effectiveness as in the scid mouse model. These results indicate that scid mice may be suitable for assessing therapeutic approaches to human B cell proliferation.