Interferon-alpha-mediated prevention of in vitro apoptosis of chronic lymphocytic leukemia B cells: role of bcl-2 and c-myc

Type I interferon and cancer

Type I interferon (IFN) is a class of proinflammatory cytokines with a dual role on malignant transformation, tumor progression, and response to therapy. On the one hand, robust, acute, and resolving type I IFN responses have been shown to mediate prominent anticancer effects, reflecting not only their direct cytostatic/cytotoxic activity on (at least some) malignant cells, but also their pronounced immunostimulatory functions. In line with this notion, type I IFN signaling has been implicated in the antineoplastic effects of various immunogenic therapeutics, including (but not limited to) immunogenic cell death (ICD)-inducing agents and immune checkpoint inhibitors (ICIs). On the other hand, weak, indolent, and non-resolving type I IFN responses have been demonstrated to support tumor progression and resistance to therapy, reflecting the ability of suboptimal type I IFN signaling to mediate cytoprotective activity, promote stemness, favor tolerance to chromosomal instability, and facilitate the establishment of an immunologically exhausted tumor microenvironment. Here, we review fundamental aspects of type I IFN signaling and their context-dependent impact on malignant transformation, tumor progression, and response to therapy.

Development of the R263K Mutation to Dolutegravir in an HIV-1 Subtype D Virus Harboring 3 Class-Drug Resistance

Dolutegravir (DTG), a second-generation integrase strand-transfer inhibitor (INSTI), is equivalent or superior to current non-nucleotide reverse transcriptase inhibitors (NNRTIs), protease inhibitors (PIs), and first-generation INSTI-based antiretroviral regimens (ARVs). It has the potential to make big improvements in HIV control globally and within patients. This is perhaps the most "precious" HIV drug available. The integrase mutation R263K has been observed in tissue culture experiments and in patients treated with dolutegravir monotherapy in clinical trials. Globally, adherence and monitoring may be less than optimal and therefore DTG resistance more common. This is particularly important in low-middle-income countries, where patients may remain on failing regimens for longer periods of time and accumulate drug resistance. Data on this mutation in non-subtype B infections do not exist. We describe the first report of the R263K integrase mutation in a dolutegravir-exposed subtype D-infected individual with vertically acquired HIV. We have used deep sequencing of longitudinal samples to highlight the change in resistance over time while on a failing regimen. The case highlights that poorly adherent patients should not be offered dolutegravir even as part of a combination regimen and that protease inhibitors should be used preferentially.

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.

Modulation of the sensitivity of Jurkat T-cells to inhibition of protein synthesis by tumor necrosis factor α-related apoptosis-inducing ligand

Tumor necrosis factor α-related apoptosis-inducing ligand (TRAIL) is a potent inducer of apoptosis in Jurkat T lymphoma cells. One of the characteristics of the phase preceding overt apoptosis is the marked downregulation of protein synthesis. We have investigated factors that can influence this response and have explored some of the signaling pathways involved. We show that interferon-α (IFNα) pretreatment desensitizes Jurkat cells to TRAIL-induced inhibition of protein synthesis, such that the concentration of TRAIL required for 50% inhibition is increased by 10-fold. The inhibition of translation is characterized by dephosphorylation of the eIF4E-binding protein 4E-BP1 and IFNα desensitizes Jurkat cells to this effect. IFNα also inhibits TRAIL-mediated dephosphorylation of the growth-promoting protein kinase B (Akt). Since Jurkat cells are defective for phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and therefore have constitutive phosphoinositide 3-kinase (PI3K) activity, we investigated the consequences for protein synthesis of inhibiting PI3K using LY294002. Inhibition of PI3K partially inhibits translation, but also enhances the effect of a suboptimal concentration of TRAIL. However, LY294002 does not block the ability of IFNα to protect protein synthesis from TRAIL-induced inhibition. Data are presented suggesting that IFNα impairs the process of activation of caspase-8 within the TRAIL death-inducing signaling complex.

Identification of a STAT5 target gene, Dpf3, provides novel insights in chronic lymphocytic leukemia

STAT5 controls essential cellular functions and is encoded by two genes, Stat5a and Stat5b. To provide insight to the mechanisms linking hematologic malignancy to STAT5 activation/regulation of target genes, we identified STAT5 target genes and focused on Dpf3 gene, which encodes for an epigenetic factor. Dpf3 expression was induced upon IL-3 stimulation in Ba/F3 cells, while strong binding of both STAT5a and STAT5b was detected in its promoter. Reduced expression of Dpf3 was detected in Ba/F3 cells with Stat5a and Stat5b knock-down, suggesting that this gene is positively regulated by STAT5, upon IL-3 stimulation. Furthermore, this gene was significantly up-regulated in CLL patients, where DPF3 gene/protein up-regulation and strong STAT5 binding to the DPF3 promoter, correlated with increased STAT5 activation, mainly in non-malignant myeloid cells (granulocytes). Our findings provide insights in the STAT5 dependent transcriptional regulation of Dpf3, and demonstrate for the first time increased STAT5 activation in granulocytes of CLL patients. Novel routes of investigation are opened to facilitate the understanding of the role of STAT5 activation in the communication between non-malignant myeloid and malignant B-cells, and the functions of STAT5 target genes networks in CLL biology.

The role of cytokines in the mechanism of adverse drug reactions

Cytokines are thought to play a role in acute and/or immune-mediated adverse drug reactions (ADRs) due to their ability to regulate the innate and adaptive immune systems. This role is highly complex owing to the pluripotent nature of cytokines, which enables the same cytokine to play multiple roles depending on target organ(s) involved. As a result, the discussion of cytokine involvement in ADRs is organized according to target organ(s); specifically, ADRs targeting skin and liver, as well as ADRs targeting multiple organs, such as drug-induced autoimmunity and infusion-related reactions. In addition to discussing the mechanism(s) by which cytokines contribute to the initiation, propagation, and resolution of ADRs, we also discuss the usefulness and limitations of current methodologies available to conduct such mechanistic studies. While animal models appear to hold the most promise for uncovering additional mechanisms, this field is plagued by a lack of good animal models and, as a result, the mechanism of cytokine involvement in ADRs is often studied using less informative in vitro studies. The recent formation of the Drug-Induced Liver Injury Network, whose goal is collect thousands of samples from drug-induced liver injury patients, has enormous potential to advance knowledge in this field, by enabling large-scale cytokine polymorphism studies. In conclusion, we discuss how further advances in this field could be of significant benefit to patients in terms of preventing, predicting, and treating ADRs.

Honokiol up-regulates prostacyclin synthease protein expression and inhibits endothelial cell apoptosis

Honokiol is a bioactive compound extracted from the Chinese medicinal herb Magnolia officinalis. We recently demonstrated that honokiol inhibited arterial thrombosis through stimulation of prostacyclin (PGI2) generation and endothelial cell protection. The current study is designed to investigate its mechanism of stimulation of PGI2 generation and cell protection. 6-keto-PGF1alpha, the stable metabolite of PGI2, in the media of rat aortic endothelial cells was measured with radioimmunoassay kits. Indomethacin, an inhibitor of cyclooxygenase (COX) and tranylcypromine, a prostacyclin synthease inhibitor were used to ascertain the target enzyme affected by honokiol. Prostacyclin synthease protein levels in endothelial cells were determined by Western blot analysis using an anti-PGI2 synthease rabbit polyclonal antibody. Flow cytometry was used to quantify the apoptotic cells and spectrophotometry was used to test the caspase-3 activity. Honokiol (0.376-37.6 microM) increased the level of 6-keto-PGF1alpha in the media of normal endothelial cells. It counteracted the inhibitory effect of tranylcypromine on the PGI2 generation, but did not influence the effect of indomethacin; evidently, honokiol up-regulated the expression of prostacyclin synthease in the endothelial cells. These effects showed perfect concentration-dependent behavior. In addition, at lower concentration (0.376-3.76 microM), honokiol significantly decreased the percentage of apoptotic endothelial cells induced by oxidized low-density lipoprotein (ox-LDL) and significantly lowered the activity of caspase-3 stimulated by ox-LDL. A high dose of honokiol (37.6 microM), however, failed to influence either of them. In conclusion, honokiol augments PGI2 generation in normal endothelial cells; its effect on PGI2 generation attributes to up-regulation of prostacyclin synthease expression; its cell protection may be correlated with its inhibition on apoptosis of endothelial cells. These findings have partly revealed the molecular mechanism of honokiol on inhibiting arterial thrombosis.

Deficiency of type I interferon contributes toSle2-associated component lupus phenotypes

OBJECTIVE

Studies in mice and humans have implicated type I interferon (IFN-I) in the pathogenesis of lupus. Given that the locus for IFN-I is positioned within the Sle2 murine lupus susceptibility interval on chromosome 4, we undertook this study to investigate whether differences in IFN-I levels might potentially contribute to the phenotypes ascribed to this locus.

METHODS

IFN-I, anti-IFN-I, isotype control antibody, or phosphate buffered saline was administered to C57BL/6 and B6.Sle2 mice, and the serologic and cellular phenotypes were studied. In addition, B6.Sle2 mice were examined for structural and expression polymorphisms in the IFN-I gene.

RESULTS

In both B6.Sle2 congenic mice and C57BL/6 control mice, antibody-mediated blockade of IFN-I augmented serum autoantibody levels and boosted B1a cell numbers. Administration of IFN-I ameliorated these 2 features previously attributed to this disease locus. Importantly, compared with B6 controls, B6.Sle2 mice had reduced levels of IFN-I in their sera and cell culture supernatants, following stimulation. Although several sequence polymorphisms were noted in the Sle2 alleles of various IFN-I genes, it was not established whether any of the noted sequence variations were causally related to the observed phenotypes.

CONCLUSION

Unexpectedly, reduction of IFN-I levels reproduced the serologic and cellular phenotypes previously associated with the Sle2 lupus susceptibility interval. Placing these findings in the context of other studies, the effect of IFN-I on systemic autoimmunity appears to be far more complex than originally perceived.

Evaluation of superficial basal cell carcinomas after treatment with imiquimod 5% cream or vehicle for apoptosis and lymphocyte phenotyping

OBJECTIVE

To characterize the immune response and the apoptotic pathways that result in regression of imiquimod-treated basal cell carcinomas (BCCs).

METHODS

The trial was conducted as an open-label, matched controlled, nonrandomized study. Twelve patients were assigned as either active-treatment patients or matched control subjects. After treatment, lesions were excised and stained for CD20, CD3, CD4, CD56, bcl-2, bax, caspase-3, and p53. Additionally, a DNA fragmentation assay was performed using the terminal deoxynucleotidyltransferase-mediated dUTP nick-end-labeling method.

RESULTS

All vehicle-treated BCCs (six of six) had residual tumor compared with four of six imiquimod-treated BCCs. A dense mononuclear infiltrate surrounded all of the imiquimod-treated tumors and only one of six vehicle-treated BCCs. Staining for CD20, CD3, and CD4 revealed that the infiltrate consisted primarily of T-helper lymphocytes; however, a significant portion of the cells stained positively for CD56, indicating the presence of natural killer cells. Imiquimod-treated BCCs stained more strongly for caspase-3 and to a lesser degree p53 as compared with vehicle-treated BCCs. No differences were seen in either bax or bcl-2 staining. Minimal apoptosis was seen with the terminal deoxynucleotidyltransferase-mediated dUTP nick-end-labeling assay in either group.

CONCLUSION

This study provides evidence that imiquimod's antitumorigenic effects are mediated via up regulation of local interferon-alpha levels and supports previous work, suggesting that increased natural killer cell activity may be an important factors explaining both spontaneous regression and IFN-alpha induced regression of BCC.

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.

Long-term high-dose interferon-alpha therapy delays Hepadnavirus-related hepatocarcinogenesis in X/myc transgenic mice

The role of interferon-alpha (IFN-alpha) remains unclear in prevention of virus-induced hepatocellular carcinoma in humans. We have investigated it herewith in the X/myc transgenic mouse model of Hepadnavirus-related hepatocarcinogenesis because of upregulation of c-myc oncogene in the liver. We have demonstrated that IFN-alpha can downregulate dose-dependently hepatocyte proliferation and c-myc overexpression at early premalignant stages, while it does not affect either hepatocyte apoptosis or telomerase activity at these steps. However, continuous and long-term administration of IFN-alpha dose-dependently delays tumor onset in dysplastic livers and increases overall survival of animals, more efficiently whether started before the onset of dysplasia. The present study therefore highlights that early preventive administration of IFN-alpha can slow down evolution towards hepatocellular carcinoma via repression of c-myc and hepatocyte proliferation at premalignant steps in experimental c-myc-induced hepatocarcinogenesis. However, the transient effect observed in this study emphasizes a need to clarify the possible mechanisms of acquired resistance and subsequent therapeutic escape. Our experimental model may be a pertinent tool to explore antioncogenic properties of IFN-alpha in human cirrhotic livers showing c-myc upregulation.

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

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

Modulation of the activity of calcium-activated neutral proteases (calpains) in chronic lymphocytic leukemia (B-CLL) cells

Decreased susceptibility to apoptosis and impaired proliferative control are thought to be responsible for prolonged life span and accumulation of chronic lymphocytic leukemia (B-CLL) cells. The activity of calpains (calcium-dependent, neutral proteases, active in the cells responding to signals inducing a rise of cytoplasmic Ca(++)) is involved in the regulation of apoptosis of some cell types by interaction with caspase-3. This work verifies the hypothesis of the abnormal activity of calpains and its role in reduced apoptosis of the B-CLL cells. Casein zymography, reverse transcriptase-polymerase chain reaction, and Western blotting were used for identification and quantification of the activity and expression of calpains in B-CLL cells and purified normal B lymphocytes. The activity and expression of mu-calpain (requiring micromolar Ca(++) for activation) are significantly higher in the leukemic than in nonmalignant cells. Contrarily, the activity and expression of m-calpain (requiring millimolar Ca(++)) as well as the expression of calpastatin (an endogenous inhibitor of calpains) are unchanged or reduced in the B-CLL lymphocytes. Correspondingly, the activity of caspase-3 is many times lower in the B-CLL cells than in normal B lymphocytes. Inhibition of overexpressed mu-calpain in living B-CLL cells in vitro results in doubling of the proportion of the cells undergoing spontaneous apoptosis. This observation suggests a possible role for calpains in longer survival of the B-CLL cells and may open new therapeutic possibilities.

Immune complexes and apoptosis in B-cell chronic lymphocytic leukemia

The progressive accumulation of B-cell chronic lymphocytic leukemia (B-CLL) cells in vivo is attributed to resistance to apoptosis, although this can be modulated in vitro by a variety of cellular and humoral factors (cell-cell, cell-matrix interactions, cytokines). We have previously reported that IgG immune complexes (IC) delay B-CLL cell apoptosis through a paracrine mechanism, which depends on monocytes and NK cells. On the other hand, despite the fact that IC effectively bind to type II Fc gammaRs expressed on B-CLL cells, they are unable to deliver transmembrane signals. We speculate that this lack of responsiveness of resting B-CLL cells to IC could be overcome by activation. The analysis of this possibility would be relevant since the presence of circulating IC is a common feature in B-CLL patients.

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.

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.

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.

Interferon α prevents spontaneous apoptosis of clonal Th2 cells associated with chronic hypereosinophilia

A recent study identified a clonal expansion of CD3−CD4+cells secreting Th2-type cytokines in 4 patients with chronic hypereosinophilia. Because interferon α (IFN-α) is used in the therapy of the idiopathic hypereosinophilic syndrome, the effects of this cytokine on the survival of clonal Th2 cells isolated from the blood of 2 patients were determined. First, these cells displayed a high rate of spontaneous apoptosis on culture in cytokine-free medium and were also sensitive to Fas-mediated apoptosis induced by soluble Fas ligand. Addition of IFN-α or interleukin-2 (IL-2) to culture medium resulted in significant protection against spontaneous but not Fas-induced apoptosis. Although spontaneous apoptosis of the clonal Th2 cells was clearly associated with down-regulation of both bcl-2 and bcl-xL levels, IFN-α had no significant effect on the expression of these antiapoptotic proteins, whereas addition of IL-2 resulted in higher levels of bcl-2. On the other hand, IFN-α decreased the numbers of cells with disrupted mitochondrial transmembrane potential both during spontaneous apoptosis and after exposure to protoporphyrin IX. Thus, IFN-α might promote the survival of clonal Th2 cells, an effect that could be relevant to the therapeutic approach for patients with chronic hypereosinophilia caused by clonal expansion of Th2-type cells.

Interferon α prevents spontaneous apoptosis of clonal Th2 cells associated with chronic hypereosinophilia

A recent study identified a clonal expansion of CD3−CD4+cells secreting Th2-type cytokines in 4 patients with chronic hypereosinophilia. Because interferon α (IFN-α) is used in the therapy of the idiopathic hypereosinophilic syndrome, the effects of this cytokine on the survival of clonal Th2 cells isolated from the blood of 2 patients were determined. First, these cells displayed a high rate of spontaneous apoptosis on culture in cytokine-free medium and were also sensitive to Fas-mediated apoptosis induced by soluble Fas ligand. Addition of IFN-α or interleukin-2 (IL-2) to culture medium resulted in significant protection against spontaneous but not Fas-induced apoptosis. Although spontaneous apoptosis of the clonal Th2 cells was clearly associated with down-regulation of both bcl-2 and bcl-xL levels, IFN-α had no significant effect on the expression of these antiapoptotic proteins, whereas addition of IL-2 resulted in higher levels of bcl-2. On the other hand, IFN-α decreased the numbers of cells with disrupted mitochondrial transmembrane potential both during spontaneous apoptosis and after exposure to protoporphyrin IX. Thus, IFN-α might promote the survival of clonal Th2 cells, an effect that could be relevant to the therapeutic approach for patients with chronic hypereosinophilia caused by clonal expansion of Th2-type cells.

Oxidized-LDL induce apoptosis in HUVEC but not in the endothelial cell line EA.hy 926

We studied the cytotoxic effect of copper-oxidized LDL in human primary human umbilical vein endothelial cells (HUVEC) and the immortalized EA.hy 926 cell line. Copper oxidized LDL (50-200 microg apoB/ml) induced concentration-dependent apoptotic cell death in HUVEC but did not induce apoptosis in EA.hy 926 cells. Only necrotic EA.hy 926 cells were evidenced at all copper oxidized LDL concentrations (25-200 microg apoB/ml), oxidation states (lightly, moderately and extensively copper-oxidized LDL) and incubation periods (4, 8 and 20 h). The different mechanisms of cell death induced by copper-oxidized LDL in EA.hy 926 cells and HUVEC may be related to various factors such as cytokines. In this study, we investigated whether interleukin-8 may be implicated in this process. The interleukin-8 production was increased in EA.hy 926 cells but not in HUVEC incubated with oxidized LDL. This increase in EA.hy 926 cells was associated with necrosis but not apoptosis. Nevertheless, the addition of interleukin-8 to HUVEC did not inhibit apoptosis induced by oxidized LDL. As the lower antioxidant capacity of EA.hy 926 cells results in higher sensitivity to oxidized LDL cytotoxicity (as we previously described), the redox status of cells may also control the form of endothelial cell death. In atherosclerotic lesions, the formation of apoptotic endothelial cells may result in part from the induction by oxidized LDL.

Regulation of apoptosis in myeloid cells by interferon consensus sequence-binding protein

Mice with a null mutation of the gene encoding interferon consensus sequence-binding protein (ICSBP) develop a disease with marked expansion of granulocytes and macrophages that frequently progresses to a fatal blast crisis, thus resembling human chronic myelogenous leukemia (CML). One important feature of CML is decreased responsiveness of myeloid cells to apoptotic stimuli. Here we show that myeloid cells from mice deficient in ICSBP exhibit reduced spontaneous apoptosis and a significant decrease in sensitivity to apoptosis induced by DNA damage. In contrast, apoptosis in thymocytes from ICSBP-deficient mice is unaffected. We also show that overexpression of ICSBP in the human U937 monocytic cell line enhances the rate of spontaneous apoptosis and the sensitivity to apoptosis induced by etoposide, lipopolysaccharide plus ATP, or rapamycin. Programmed cell death induced by etoposide was specifically blocked by peptides inhibitory for the caspase-1 or caspase-3 subfamilies of caspases. Studies of proapoptotic genes showed that cells overexpressing ICSBP have enhanced expression of caspase-3 precursor protein. In addition, analyses of antiapoptotic genes showed that overexpression of ICSBP results in decreased expression of Bcl-X(L). These data suggest that ICSBP modulates survival of myeloid cells by regulating expression of apoptosis-related genes.

Interferon alfa receptor expression and growth inhibition by interferon alfa in human liver cancer cell lines

Type I interferon (IFN) receptor consists of two chains (Hu-IFN-alphaR1 and Hu-IFN-alphaR2), and Hu-IFN-alphaR2 takes a soluble (Hu-IFN-alphaR2a), short (Hu-IFN-alphaR2b), or long (Hu-IFN-alphaR2c) form. We examined the expression of type I IFN receptor, the growth-suppression effect of IFN-alpha, and their relationship in 13 liver cancer cell lines. With reverse-transcription polymerase chain reaction (RT-PCR) analysis, the expressions of Hu-IFN-alphaR1, Hu-IFN-alphaR2a, and Hu-IFN-alphaR2c were confirmed in all cell lines, and that of Hu-IFN-alphaR2b in 12 cell lines. All cell lines expressed mRNAs of a transcriptional activator, interferon regulatory factor (IRF)-1, and its antagonistic repressor (IRF-2). Flow cytometry revealed weak expression of Hu-IFN-alphaR2 on the cell surface in 12 cell lines. The soluble-form protein of Hu-IFN-alphaR2 was detected at varying levels in culture supernatants of all cell lines with enzyme-linked immunosorbent assay (ELISA). Cell proliferation was suppressed in proportion to the dose of human natural IFN-alpha at 96 hours of culture, but it was not clearly related to the expression of Hu-IFN-alphaR2 protein on the cell surface. Investigations on the morphology, DNA, and cell cycle presented four growth suppression patterns as a result of IFN-alpha: 1) induction of apoptosis and blockage of cell cycle at the S phase (9 cell lines); 2) blockage at the S phase (2 cell lines); 3) induction of apoptosis and blockage at the G2/M phase (1 cell line); and 4) blockage at the G1 phase (1 cell line). There was no evidence showing that changes in the expressions of Bcl-2, Bcl-xL, Bak, and Bax lead directly to IFN-alpha-mediated apoptosis. Our findings demonstrated that IFN-alpha would express growth-suppression effects at varying degrees by inducing inhibition of cell-cycle progression with or without apoptosis, regardless of the expression level of Hu-IFN-alphaR2 protein on the cell surface.

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.

Effect of anti-DNA autoantibodies on the gene expression of interleukin 8, transforming growth factor-beta, and nitric oxide synthase in cultured endothelial cells

Our study aims to determine whether anti-dsDNA exerts any effect on the gene expression of IL-8 or TGF-beta in cultured HUVEC. Both cytokines have angiogenic effect on endothelial cells. IgG was purified from 19 patients with SLE and from 19 healthy controls. Anti-dsDNA-depleted polyclonal IgG was also prepared from serum IgG of lupus patients by affinity chromatography with DNA cellulose column. Compared with either control IgG or anti-dsDNA-dep-IgG, HUVEC incubated with anti-dsDNA-containing-IgG expressed higher levels of IL-8 mRNA (p = 0.0001) and TGF-beta 1 mRNA (p = 0.0014). We demonstrated a significant increase in the percentage of cells with fragmented DNA in HUVEC incubated with anti-dsDNA-containing-IgG compared with those incubated with anti-dsDNA-dep-IgG, supporting the notion that anti-dsDNA may exert a direct apoptotic effect on cultured endothelial cells. Our study provides in vitro evidence that anti-dsDNA could play an important pathogenetic role in inducing inflammatory injury of vascular endothelium in SLE.

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.

The anti-tumor effect of Ganoderma lucidum is mediated by cytokines released from activated macrophages and T lymphocytes

The present study was to ascertain the immunomodulating and anti-tumor effects of Ganoderma (G.) lucidum. Polysaccharides (PS) from fresh fruiting bodies of G. lucidum (PS-G) were isolated and used to potentiate cytokine production by human monocytes-macrophages and T lymphocytes. Our results had shown that the levels of interleukin (IL)-1 beta, tumor necrosis factor (TNF)- alpha, and IL-6 in macrophage cultures treated with PS-G (100 micrograms/ml) were 5.1-, 9.8- and 29-fold higher, respectively, than those of untreated controls. In addition, the release of interferon (IFN)- gamma from T lymphocytes was also greatly promoted in the presence of PS-G (25-100 micrograms/ml). Furthermore, these cytokine-containing mononuclear cell-conditioned media (PSG-MNC-CM) were found to suppress the proliferation and clonogenicity of both the HL-60 and the U937 leukemic cell lines. DNA labeling and gel electrophoresis showed that treatment with PSG-MNC-CM markedly induced leukemic-cell apoptosis. Flow-cytometric analysis revealed that few (2.3 +/- 0.8%) apoptotic cells were seen in the control cultures, while PSG-MNC-CM treatment resulted in a significant increase in the apoptotic population both in the HL-60 (38.3 +/- 4.5%) and in the U937 (44.5 +/- 3.8%) cells. In addition, 40 to 45% of the treated leukemic cells were triggered to differentiate into mature monocytic cells expressing CD14 and CD68 surface antigens. However, PS-G alone had no such effects even at a higher dose of 400 micrograms/ml. Since untreated macrophages and T lymphocytes produced little or no cytokine, and normal MNC-CM did not suppress leukemic cell growth, it was suggestive that the anti-tumor activity of PSG-MNC-CM was derived from the elevated levels of cytokines. Antibody-neutralization studies further revealed that the anti-tumor cytokines in the PSG-MNC-CM were mainly of TNF- alpha and IFN- gamma, and these 2 cytokines acted synergistically on the inhibition of leukemic-cell growth.

Interferon-alpha, Bcl-2 expression and apoptosis in B-cell chronic lymphocytic leukemia

Interferon-alpha has been used as therapy in patients with B-cell chronic lymphocytic leukaemia (B-CLL), and is able to induce remissions in patients with early stage disease. Although interferon-alpha exhibits a wide variety of cellular effects, none of these have adequately explained the mechanism of action of interferon-alpha in B-CLL. Recent attention has focussed on the role of bcl-2 in B-CLL, and the regulation of bcl-2 expression by cytokines. B-CLL is characterized by the relentless accumulation in the peripheral blood and bone marrow of a monoclonal population of long-lived B-cells. However, when these cells are cultured in vitro, they die rapidly by apoptosis or programmed cell death. It has recently been demonstrated that B-CLL cells can be protected from apoptotic death in vitro by co-culture with cytokines, such as IL-1, IL-2, IL-4, IL-6 and interferon-gamma. The protection against apoptosis is correlated with increased levels of bcl-2 expression. It was suggested that interferon-alpha induced remissions in early stage B-CLL by interrupting these growth-factor dependent survival pathways and allowing the cells to die by apoptotic death in vivo. However, interferon-alpha has also been shown to protect B-CLL cells from apoptotic death in vitro. This suggests that interferon-alpha does not produce remission in B-CLL by direct effects on B-CLL cells in the circulation. Many of the cytokines which protect B-CLL cells from apoptotic cell death, are members of the cytokine receptor family which utilize a common family of signal transduction molecules. Further elucidation of these signal transduction pathways may offer the prospect of developing novel therapeutic strategies aimed at inducing apoptosis of the malignant clone in vivo.