Serum levels of IL-12 and the production of IFN-gamma, IL-2 and IL-4 by peripheral blood mononuclear cells (PBMC) in cancer patients treated with Viscum album extract

Biological activity of mistletoe: in vitro and in vivo studies and mechanisms of action

Mistletoe has been used as treatment of many diseases in traditional and folk medicine. To date, anticancer, immunomodulatory, cardiac, antidiabetic, hepatoprotective, neuropharmacological, antibacterial and antifungal properties of mistletoe extracts have been studied the most. In this review, we summarized in vitro and in vivo studies on the pharmacological activity of Viscum species. Furthermore, we proposed the possible mechanisms of action of this herb, which might include many signalling pathways. Mistletoe could regulate either similar or different targets in various pathways that act on membrane receptors, enzymes, ion channels, transporter proteins and transcriptional targets. Still, pharmacological activities of mistletoe have been investigated mainly for crude extracts. It is a new field for scientists to determined which chemical compounds are responsible for the individual biological activities of mistletoe and how these activities are achieved. As a result, mistletoe might become a source of new complementary therapies supporting the treatment of many diseases.

Differential Effects of Viscum album Preparations on the Maturation and Activation of Human Dendritic Cells and CD4⁺ T Cell Responses

Extracts of Viscum album (VA); a semi-parasitic plant, are frequently used in the complementary therapy of cancer and other immunological disorders. Various reports show that VA modulates immune system and exerts immune-adjuvant activities that might influence tumor regression. Currently, several therapeutic preparations of VA are available and hence an insight into the mechanisms of action of different VA preparations is necessary. In the present study, we performed a comparative study of five different preparations of VA on maturation and activation of human dendritic cells (DCs) and ensuing CD4⁺ T cell responses. Monocyte-derived human DCs were treated with VA Qu Spez, VA Qu Frf, VA M Spez, VA P and VA A. Among the five VA preparations tested VA Qu Spez, a fermented extract with a high level of lectins, significantly induced DC maturation markers CD83, CD40, HLA-DR and CD86, and secretion of pro-inflammatory cytokines such as IL-6, IL-8, IL-12 and TNF-α. Furthermore, analysis of T cell cytokines in DC-T cell co-culture revealed that VA Qu Spez significantly stimulated IFN-γ secretion without modulating regulatory T cells and other CD4⁺ T cytokines IL-4, IL-13 and IL-17A. Our study thus delineates differential effects of VA preparations on DC maturation; function and T cell responses.

Preclinical and clinical effects of mistletoe against breast cancer

Breast cancer is among the most frequent types of cancer in women worldwide. Current conventional treatment options are accompanied by side effects. Mistletoe is amongst the important herbal medicines traditionally used as complementary remedies. An increasing number of studies have reported anticancer activity of mistletoe extracts on breast cancer cells and animal models. Some recent evidence suggests that cytotoxic activity of mistletoe may be mediated through different mechanisms. These findings provide a good base for clinical trials. Various studies on mistletoe therapy for breast cancer patients revealed similar findings concerning possible benefits on survival time, health-related quality of life (HRQoL), remission rate, and alleviating adverse reactions to conventional therapy. This review provides an overview of the recent findings on preclinical experiments and clinical trials of mistletoe for its cytotoxic and antitumor activity and its effect on HRQoL in breast cancer patients. Moreover, studies investigating molecular and cellular mechanisms underlying antitumor activity of mistletoe are discussed in this paper. The analyzed trials provided evidence that there might be a combination of pharmacological and motivational aspects mediated by the mistletoe extract application which may contribute to the clinical benefit and positive outcome such as improved HRQoL and self-regulation in breast cancer patients.

Enhanced dendritic cell maturation by the B-chain of Korean mistletoe lectin (KML-B), a novel TLR4 agonist

Korean mistletoe lectin (KML) is composed of A and B sub-chains. The B-chain binds to cell surfaces, whereas the A-chain hinders translation because it is a RIP (ribosome inactivating protein) inducing apoptosis. Although KML has various biological and immunological activities, its potential use in cancer therapy or as an adjuvant therapy is limited by its toxicity to normal cells. This study was conducted to determine whether the B-chain of KML (KML-B) has immunoadjuvant activity and cytotoxicity activity. To evaluate the immunomodulatory activities of B chain KML, in vitro experiments employing bone marrow-derived dendritic cells (BMDCs) were performed. Dendritic cells (DCs) are a unique group of white blood cells that are able to capture and process antigens for presentation to T cells, which constitute primary immune response. In the present study, KML-B was found to be non-cytotoxic to BMDCs. Furthermore, the expressions of co-stimulatory molecules (CD40, CD80, CD86, and MHC II) and the secretions of cytokines (IL-1β, IL-6, IL-12p70, and TNF-α) were increased in BMDCs by KML-B. In addition, other indicators (antigen-uptake and CCR7 expression) of BMDC maturation were changed by KML-B, and the ability of KML-B to enhance various functions by BMDCs was found to be dependent on TLR4 expression. Moreover, BMDCs matured by KML-B induced naïve CD4(+) T cell differentiation toward Th1 cells directly and indirectly. These experiments confirm that KML-B exhibits potent immunomodulatory properties and suggest that KML-B be considered a potential dendritic cell-based cancer therapy and immunoadjuvant.

Immunological response to mistletoe (Viscum album L.) in cancer patients: a four-case series

European mistletoe (Viscum album) has been used in complementary cancer treatment, but little is known concerning its effects on immunological parameters, although there is evidence that Viscum may stimulate the immune system. In this study, a trial was conducted with cancer patients to determine whether Viscum album extracts could improve the results of immune tests. These were: white blood cell count (leukocytes, neutrophils, lymphocytes), CD4+ and CD8+ T-lymphocytes, intradermal tests of delayed hypersensitivity (candidin, trichophytin, purified protein derivative-PPD), complement C3 and C4, and immunoglobulin A, G and M. Four patients received seven doses of subcutaneous Viscum album 20 mg, twice weekly. Immunological tests were carried out before and after treatment, and an increase in several parameters of humoral and cellular immunity were shown. Apart from reactions around the injection sites, treatment was well tolerated and all patients benefited from it. These results suggest that Viscum album can enhance humoral and cellular immune responses in cancer patients, but further studies attesting to the possible clinical impact of these immunological effects are necessary.

Mistletoe Preparation Iscador: Are there Methodological Concerns with Respect to Controlled Clinical Trials?

In Europe many cancer patients use complementary therapies, particularly mistletoe. Only a few controlled clinical trials have been performed with the mistletoe preparation Iscador as a complementary treatment for cancer, many of them with medium to low quality due to methodological shortcomings. Reasons for some quality concerns, particularly discontinuation of treatment and/or participation and premature termination are analyzed. Analysis is based on controlled clinical trials dealing with Iscador. Data stem from the archive of published and ongoing research of the <> (Society for Cancer Research) in Arlesheim, Switzerland. Controlled clinical studies with cancer patients that were started after 01.01.1990 or were not completed by then have been evaluated. Fifty-six controlled studies are documented, 24 of them randomized and 32 non-randomized. Nine of the randomized studies were done by matched-pair design, the others by conventional parallel group design; six of the last were terminated prematurely primarily for slow recruitment due to patient preferences and compliance of physicians. Patient and physician preference seem to be important factors limiting recruitment for randomized trials and hence implementation. This adds to the overall unwillingness of participation by patients with serious diseases. A well-balanced mix of designs using different research methods and outcomes is suggested combined with analyses, in countries where mistletoe therapy in general or Iscador in particular is unknown or not available.

In vitro immunoregulatory effects of Korean mistletoe lectin on functional activation of monocytic and macrophage-like cells

Korean mistletoe lectin (KML) is one of the major active components in Viscum album var. (coloratum), displaying various biological effects such as anti-tumor and anti-metastatic activities. Even though it has been shown to boost host immune defense mechanisms, the immunomodulatory effects of KML on specific immune responses mediated by macrophages have not been fully elucidated. Therefore, in this study, we aimed to demonstrate KML's regulatory roles on macrophage-mediated immune responses. KML clearly blocked lipopolysaccharide (LPS)-induced events [expression of interleukin (IL)-10, nitric oxide (NO) production and phagocytic uptake], and suppressed the normal expression levels of IL-10 (at 2 ng/ml) and tumor necrosis factor (TNF)-alpha (at 10 ng/ml). In contrast, (1) the expression of cytokine (TNF-alpha) and (2) the generation of reactive oxygen species (ROS) induced by LPS were significantly up-regulated with KML co-treatment. In addition, KML itself increased the mRNA levels of IL-3 and IL-23; phagocytic uptake; the surface levels of co-stimulatory molecules (CD80 and CD86), pattern recognition receptors (PRRs) [such as dectin-1 and toll like receptor (TLR)-2] and adhesion molecules [beta1-integrins (CD29) and CD43]; and CD29-mediated cell adhesion events. Finally, according to co-treatment of D-galactose with KML under LPS-induced NO production conditions, KML inhibition seems to be mediated by binding to proteins with D-galactose. Therefore, these data suggest that KML may participate in regulating various macrophage-mediated innate and adaptive responses via binding to surface protein with D-galactose and that some of these may deserve in KML's therapeutic activities such as anti-tumor and anti-microbial effects.

Suppressive effect of a standardized mistletoe extract on the expression of activatory NK receptors and function of human NK cells

Despite long-term use of mistletoe extracts for cancer treatment, their mode of action remains elusive. In this study, it was studied in vitro if mistletoe extract is able to modulate the expression of natural cytotoxic receptors (NCRs) and NKG2D receptor, which stimulate natural killer cell-mediated cytotoxicity. Unexpectedly, a mistletoe extract, ABNOBA viscum Fraxini, inhibited the expression level of NKp46 and NKG2D receptors in dose- and time-dependent manners. The levels of NKp30 and NKG2D receptors were remarkably induced and NKp44 was slightly induced after 48 h treatment with IL-2 and IL-15 in both mRNA and surface expression. The activatory NK receptors were not induced significantly after treatment with IL-12, IL-18, and IL-21 for 48 h. Induction of activatory NK receptors by IL-2 and IL-15 was suppressed almost to the untreated levels by treatment with mistletoe extract, which appeared to induce apoptosis of NK cells in a dose-dependent manner. However, the treatment with IL-2 and IL-15 did not prevent the mistletoe-induced NK-cell death. Mistletoe extract inhibited significantly the cytotoxic activity of resting and IL-2- or IL-15-stimulated NK cells. These results suggest that inhibition of survival and function of NK cells by mistletoe extract may curtail in part the therapeutic effects of mistletoe.

Interleukin-12 is associated with the in vivo anti-tumor effect of mistletoe extracts in B16 mouse melanoma

Viscum album (VA) preparations consist of aqueous extracts of different types of lectins of mistletoe. VA exert cytotoxic and immunomodulatory properties that may be relevant for the inhibition of tumor growth. We addressed the effects of VA preparation VA Qu FrF on growth of B16F1 melanoma implanted in mice and on proliferation and cytokine synthesis of splenocytes. In C57BL6 mice, inhibition of tumor growth by VA was associated with an enhancement of splenocyte proliferation and with an up-regulation of IL-12 secretion. In IL-12-deficient strain of mice the inhibition of melanoma growth by VA and the splenocyte proliferation were abrogated. Results from the present study strongly suggest a crucial role of IL-12 in the anti-tumor properties of VA extracts.

Production of Cytokine and NO by RAW 264.7 Macrophages and PBMC In Vitro Incubation with Flavonoids

Flavonoids, a group of low molecular weight phenylbenzopyrones, have various pharmacological properties including antioxidant activity, anticancer, and immunomodulatory effects. In the present study, lipopolysaccharide (LPS) and phorbol 12-myristate 13-acetate/phytohemagglutinin (PMA/PHA) were used as stimulants for RAW 264.7 macrophages and human peripheral blood mononuclear cell (hPBMC), and tumor necrosis factor (TNF)-alpha and interleukin (IL)-2 productions were measured. In addition, flavonoids were examined for their effects on LPS-induced NO production in RAW 264.7 macrophages. The results showed that all compounds were not strongly cytotoxic at the tested concentrations on hPBMC and RAW 264.7 macrophages. On immunomodulatory properties, catechin, epigallocatechin (EGC), naringenin, and fisetin repressed NO production and TNF-alpha secretion. Furthermore, catechin, epigallocatechin gallate (EGCG), epicatechin (EC), luteolin, chrysin, quercetin, and galangin increased IL-2 secretion while EGC, apigenin, and fisetin inhibited the secretion. These results indicated that flavonoids have the capacity to modulate the immune response and have a potential anti-inflammatory activity. There was no obvious structure-activity relationship regard to the chemical composition of the flavonoids and their cell biological effects.

Crystal Structure of Himalayan Mistletoe Ribosome-inactivating Protein Reveals the Presence of a Natural Inhibitor and a New Functionally Active Sugar-binding Site

Ribosome-inactivating proteins (RIPs) are toxins involved in plant defense. How the plant prevents autotoxicity is not yet fully understood. The present study is the first structural evidence of a naturally inhibited form of RIP from a plant. Himalayan mistletoe RIP (HmRIP) was purified from Viscum album leaves and crystallized with lactose. The structure was determined by the molecular replacement method and refined at 2.8-A resolution. The crystal structure revealed the presence of high quality non-protein electron density at the active site, into which a pteridine derivative (2-amino 4-isopropyl 6-carboxyl pteridine) was modeled. The carboxyl group of the ligand binds strongly with the key active site residue Arg(162), nullifies the positive charge required for catalysis, and thereby acts as a natural inhibitor. Lectin subunits of RIPs have two active sugar-binding sites present in 1alpha- and 2gamma-subdomains. A third functionally active site has been identified in the 1beta-subdomain of HmRIP. The 1beta-site is active despite the absence of conserved polar sugar-binding residues. Loss of these residues is compensated by the following: (i) the presence of an extended site where the penultimate sugar also interacts with the protein; (ii) the interactions of galactose with the protein main chain carbonyl and amide nitrogen atoms; (iii) the presence of a well defined pocket encircled by four walls; and (iv) a favorable stacking of the galactose ring with Tyr(66) besides the conserved Phe(75). The mode of sugar binding is also distinct at the 1alpha and 2gamma sugar-binding sites.

Comparison of the impact of pro- and antiinflammatory immune processes at the two immune-deviated sites, eye and solid tumor and possible consequences for the antitumoral therapy with fever inducers

Findings from various epidemiological studies suggest that acute inflammation and fever may decrease the risk of developing certain types of cancer. In an established tumor situation acute inflammation and fever resulted in tumor regression in some cases, however, treatment was sometimes ineffective or even deleterious. It has been suggested that chronic inflammation contributes to carcinogenesis and in an established tumor situation to malignancy. In order to better understand the role of acute inflammation and fever in the treatment of cancer, we compare some of the current knowledge about the effects of pro- and antiinflammatory immunological processes in the two immune-deviated sites, eye and cancer. Striking similarities between these two sites have been demonstrated. The knowledge gained in experimental studies abrogating immune privilege in the eye could provide insights into the inconsistent results of proinflammatory cancer therapy. The eye could be used as a model to develop hypotheses on how to abolish the immunological tolerance state of a solid tumor and make it susceptible to immunological destruction. The immune privilege of the eye is abrogated, at least transiently, in the initial stages of tissue- or organ-specific cellular autoimmune responses and this effect is possibly supported by complement- fixing/proinflammatory antibodies. An overview of possible consequences for the tumor therapy especially in connection with inflammation and fever inducers such as bacterial vaccines or mistletoe preparations, which are therapeutically used to interfere with the privileged immune state of the tumor, is given.

Differences in amino acid sequences of mistletoe lectin I and III B-subunits determining carbohydrate binding specificity

Toxic lectins of European mistletoe Viscum album L.--MLI (viscumin), MLII and MLIII--are present in water extracts of this plant. Earlier we have cloned the full-length gene of MLIII precursor [A.G. Tonevitsky, I.I. Agapov, I.B. Pevzner, N.V. Maluchenko, M.M. Mojsenovich, U. Pfueller, M.P. Kirpichnikov, (2004) Biochemistry (Mosc.), 69 (6), 790-800, in press]. Here for the first time we report the cloning and expression in Escherichia coli cells of MLIII gene fragment encoding the carbohydrate-binding subunit. We have proved with our panel of monoclonal antibodies against ML toxins that the cloned fragment encoded MLIII B-subunit. The immunochemical and sugar-binding activities of renatured recombinant MLIII B-subunit were demonstrated in ELISA and ELLA, respectively. The comparative analysis of amino acid sequences of the cloned rMLIIIB and the B-subunits of other type II RIPs--MLI, ricin, abrin and nigrin b--was performed, revealing the main differences in primary structure of MLI and MLIII B-chains, which could determine their sugar specificity. The antigenicity analysis of MLI and MLIII B-subunits showed one epitope 25RDDDFRDGNQ34 in MLIB that is absent in MLIIIB sequence. The role of the toxic lectins and their subunits in immunological properties of mistletoe extracts is discussed.

Anti-inflammatory effect of Viscum album agglutinin-I (VAA-I): induction of apoptosis in activated neutrophils and inhibition of lipopolysaccharide-induced neutrophilic inflammation in vivo

Viscum album agglutinin-I (VAA-I) is a plant lectin which possesses antitumoral properties. This lectin is also known for its immunostimulatory effects when used at low concentrations (1-100 ng/ml). We have demonstrated recently that VAA-I is a potent inducer of human neutrophil apoptosis in vitro when used at higher concentrations. The role of VAA-I on activated neutrophils has not so far been investigated and its potential proinflammatory properties in vivo are poorly documented. Herein, we demonstrated that VAA-I (1000 ng/ml) induces apoptosis in lipopolysaccharide (LPS)-treated human neutrophils in vitro as well as in murine neutrophils isolated from lipopolysaccharide (LPS)-induced neutrophil influx. Using this model, we found that administration of VAA-I (100 or 1000 ng/ml) did not induce an inflammatory response. However, when used at 1 or 10 ng/ml, VAA-I was found to significantly induce a transitory inflammatory response, based on an increased leucocyte infiltration (>98% neutrophils). Also, we found that VAA-I inhibits LPS-induced neutrophil influx when administered simultaneously with LPS. In such conditions, some characteristic apoptotic neutrophils were observed in the pouch. Unlike LPS, which increased the production of some cytokines, VAA-I (1 or 10 ng/ml) did not increase the production of tumour necrosis factor (TNF)-alpha, interleukin (IL)-1Ra, IL-1alpha, IL-beta, IL-8, IL-10 or IL-12 (p70) in human neutrophils. We conclude that VAA-I possesses the ability to induce apoptosis of preactivated neutrophils at a concentration that does not induce a proinflammatory response. Moreover, we conclude that VAA-I can inhibit a LPS-induced proinflammatory response in vivo. These data may provide new clinical perspectives in future mistletoe therapy and favour its potential utilization based on anti-inflammatory activity that at first appears contradictory with its use as immunostimulant.

Effects ofViscum albumExtract Therapy in Patients with Cancer: Relation with Interleukin-6, Soluble Interleukin-6 Receptor, and Soluble gp130

OBJECTIVES

The aim of this investigation was to determine the effects of Viscum album (VA) extract therapy on interleukin (IL)-12, IL-16, IL-6, soluble interleukin-6 receptor (sIL-6R), and soluble gp130 (sgp130) in patients with cancer. VA extract as immunomodulator is used as treatment either following or in combination with chemo/radiotherapy. Previously we showed that serum levels of IL-12 and IL-16 were significantly elevated during tumor progression in 72 patients. The serum values of IL-6 were not significantly altered, however sIL-6R and sgp130 also increased significantly.

DESIGN

In this study the serum levels of the five parameters were measured during VA extract therapy in 46 of these 72 tumor patients and compared to the values before VA extract treatment. The levels of the serum parameters IL-12, IL-16, IL-6, sIL-6R, sgp130 were determined by enzyme-linked immunosorbent assay (ELISA).

SETTING

Private cancer hospital in Arlesheim, Switzerland.

RESULTS

Eighty percent (80%) of the tumor patients survived longer than 1 year (11 patients in stage I + II without, 8 patients after chemotherapy/radiotherapy, 10 patients in stage III + IV without, 8 patients after chemotherapy). Clinically and with laboratory investigations there was no progression in these patients. VA extract therapy did not affect serum values of IL-12 or IL-16. However both the number of patients with increased levels of IL-6, sIL-6R, and sgp130 and also the serum values decreased significantly during the treatment, (between p < 0.05 and p < 0.001). In 20% of the patients with cancer with rapid progression who died within 3 months, the serum values of IL-6 increased significantly (p < 0.05), whereas the other investigated parameters did not change.

CONCLUSION

The results show that measurements of IL-6, sIL-6R, and sgp130 could be important for establishing the clinical condition and evaluating treatment in tumor patients.

Flow cytometric testing of immunological effects of a phytomedicinal combination (equimun) and its compounds on bovine leucocytes

One of the major goals of this study was to establish fast, reliable and sensitive assays for the quality control of immunomodulating phytopreparations and to determine whether pharmacological compounds or phytopreparations have effects on bovine immune cells. Flow cytometric methods were chosen because they are very sensitive in the detection of even subtle effects on cells. In this study, we addressed the question of whether these methods are useful in monitoring the effects of EquiMun and its compounds on bovine leucocytes in vitro. EquiMun is a fixed combination of Echinacea purpurea (Ec), Thuja occidentalis (Th) and elemental phosphorus (Ph) in different starting concentrations. Separated blood mononuclear cells (MNC) and polymorphonuclear cells (PMN, mainly neutrophils) were cultured for up to 44 h in vitro in the presence or absence of the tested substances. Whereas MNC were not affected by any of the compounds, EquiMun, Ec, Th and Ph significantly reduced the forward scatter (size) of cultured PMN without affecting their side scatter (granularity). The size effects were paralleled by a significantly enhanced viability of PMN after 20 h in culture. The observed effects were constant over wide concentration ranges and indicate a very similar reaction of leucocytes from individual cows. Whereas spontaneous generation of reactive oxygen species (ROS) by neutrophils was up-regulated by Ph and EquiMun, EquiMun down-regulated the phorbol ester-stimulated ROS production. However, ROS generation by neutrophils displayed a large inter-individual variation with less apparent, down-regulatory effects of EquiMun. The ability of PMN to kill target cells via antibody-independent cellular cytotoxicity showed small inter-individual variations and was enhanced by Ec and Th but not by Ph and EquiMun, probably due to dose-dependent effects. In summary, the flow cytometric characterization of cellular viability and shape changes of neutrophils seem to be a suitable and reliable approach for the quality test of immunomodulating phytomedicines based on bioassays.

Measurements of IL-6, soluble IL-6 receptor and soluble gp130 in sera of B-cell lymphoma patients. Does viscum album treatment affect these parameters?

Interleukin-6 (IL-6) can be involved in several diseases including lymphoid malignancies. This cytokine binds to soluble IL-6 receptor (sIL-6R) circulating in blood, leading to signal transduction via gp130. Soluble IL-6R shows agonistic activity for IL-6, and the soluble form of gp130 (sgp130) an antagonistic effect against the complex IL-6/sIL-6R. Viscum album extract (Iscador) as an immunomodulator is used in the treatment of malignant disorders. In this study we investigated the effect of this treatment on the serum levels of IL-6, sIL-6R and sgp130 in B-cell lymphoma patients (n = 27), in comparison to healthy controls (n = 28). Twenty-one of 27 patients had been treated previously with chemo/radiotherapy. The patients were divided into two groups; those with short-term (investigated before and during treatment) or those with long-term Viscum album (VA) therapy (investigated during therapy). The serum levels of the three parameters were determined by ELISA. In patients having short-term treatment IL-6 values were similar to those of controls. During long-term therapy the values were significantly lower (P<0.05). The values of sIL-6R were elevated only in long-term treated patients (P<0.05), the values of sgp130 in both short-term (P<0.05) and in long-term treated patients (P=0.001). There is a significant correlation (P<0.05) between levels of sIL-6R and sgp130 in both therapy groups at 24 hours after injection. This indicates that the potent effect of sIL-6R on the biological activity of IL-6 could be inhibited by sgp130 as antagonist. Clinical data show that half of the patients (6/12) with long-term treatment had a continuous complete remission, whereas only 2/15 patients with short-term treatment had a complete remission.