The cytotoxic effect of mistletoe lectins I, II and III on sensitive and multidrug resistant human colon cancer cell lines in vitro

Self-Nanoemulsifying Drug Delivery System (SNEDDS) Using Lipophilic Extract of Viscum album subsp. austriacum (Wiesb.) Vollm

Background and Purpose

Natural products are potential sources of anticancer components. Among various species, the lipophilic extract of the Viscum album subsp. austriacum (Wiesb.) Vollm. (VALE) has shown promising therapeutic potential. The present work aimed to qualify the plant source and characterize the extract's chemical profile. In addition, a self-nanoemulsifying drug delivery system (SNEDDS) containing VALE (SNEDDS-VALE) was developed.

Methods

V. album subsp. austriacum histochemistry was performed, and the chemical profile of VALE was analyzed by GC-MS. After the SNEEDS-VALE development, its morphology was visualized by transmission electron microscopy (TEM), while its stability was evaluated by the average droplet size, polydispersity index (PdI) and pH. Lastly, SNEDDS-VALE chemical stability was evaluated by LC-DAD-MS.

Results

The histochemical analysis showed the presence of lipophilic compounds in the leaves and stems. The major compound in the VALE was oleanolic acid, followed by lupeol acetate and ursolic acid. SNEDDS was composed of medium chain triglyceride and Kolliphor® RH 40 (PEG-40 hydrogenated castor oil). A homogeneous, isotropic and stable nanoemulsion was obtained, with an average size of 36.87 ± 1.04 nm and PdI of 0.14 ± 0.02, for 14 weeks.

Conclusion

This is the first histochemistry analysis of V. album subsp. austriacum growing on Pinus sylvestris L. which provided detailed information regarding its lipophilic compounds. A homogeneous, isotropic and stable SNEDDS-VALE was obtained to improve the low water solubility of VALE. Further, in vitro and in vivo experiments should be performed, in order to evaluate the antitumoral potential of SNEDDS-VALE.

Transiently Expressed Mistletoe Lectin II in Nicotiana benthamiana Demonstrates Anticancer Activity In Vitro

Mistletoe (Viscum album) extracts have been used as alternative and complementary therapeutic preparations in multiple cancers for decades. Mistletoe lectins (ML-I, ML-II, and ML-III) are considered to be the main anticancer components of such preparations. In the present study, ML-II was transiently expressed in Nicotiana benthamiana using the pEAQ-HT expression system. Expression levels of up to 60 mg/kg of the infiltrated plant tissue were obtained, and a three-fold increase was achieved by adding the endoplasmic reticulum (ER) retention signal KDEL to the native ML-II sequence. The native protein containing His-tag and KDEL was purified by immobilized metal affinity chromatography (IMAC) and gel filtration. We found that the recombinant ML-II lectin was glycosylated and retained its carbohydrate-binding activity. In addition, we demonstrated that plant produced ML-II displayed anticancer activity in vitro, inhibiting non-small cell lung cancer H460 and A549 cells with EC50 values of 4 and 3.5 µg/mL, respectively. Annexin V-448A and PI double staining revealed that cell cytotoxicity occurred via apoptosis induction. These results indicate that ML-II transiently expressed in N. benthamiana plants is a promising candidate as an anticancer agent, although further optimization of production and purification methods is required to enable further in vitro testing, as well as in vivo assays.

Evaluation of How Integrative Oncology Services Are Valued between Hematology/Oncology Patients and Hematologists/Oncologists at a Tertiary Care Center

Evidence regarding opinions on integrative modalities by patients and physicians is lacking. Methods. A survey study was conducted assessing how integrative modalities were valued among hematology/oncology patients and hematologists and oncologists at a major tertiary medical center. Results. 1008 patients and 55 physicians were surveyed. With the exception of support groups, patients valued nutrition services, exercise therapy, spiritual/religious counseling, supplement/herbal advice, support groups, music therapy, and other complimentary medicine services significantly more than physicians (P ≤ 0.05). Conclusion. With the exception of support groups, patients value integrative modalities more than physicians. Perhaps with increasing education, awareness, and acceptance by providers and traditional institutions, integrative modalities could be equally valued between patients and providers. It is possible that increased availability and utilization of integrative oncology modalities at tertiary hospital sites could improve patient satisfaction, quality of life, and other clinical endpoints.

Quantitative analysis of receptor-mediated uptake and pro-apoptotic activity of mistletoe lectin-1 by high content imaging

Ribosome inactivating proteins (RIPs) are highly potent cytotoxins that have potential as anticancer therapeutics. Mistletoe lectin 1 (ML1) is a heterodimeric cytotoxic protein isolated from European Mistletoe and belongs to RIP class II. The aim of this project was to systematically study ML1 cell binding, endocytosis pathway(s), subcellular processing and apoptosis activation. For this purpose, state of the art cell imaging equipment and automated image analysis algorithms were used. ML1 displayed very fast binding to sugar residues on the membrane and energy-dependent uptake in CT26 cells. The co-staining with specific antibodies and uptake blocking experiments revealed involvement of both clathrin-dependent and -independent pathways in ML1 endocytosis. Co-localization studies demonstrated the toxin transport from early endocytic vesicles to Golgi network; a retrograde road to the endoplasmic reticulum. The pro-apoptotic and antiproliferative activity of ML1 were shown in time lapse movies and subsequently quantified. ML1 cytotoxicity was less affected in multidrug resistant tumor cell line 4T1 in contrast to commonly used chemotherapeutic drug (ML1 resistance index 6.9 vs 13.4 for doxorubicin; IC₅₀: ML1 1.4 ng/ml vs doxorubicin 24000 ng/ml). This opens new opportunities for the use of ML1 as an alternative treatment in multidrug resistant cancers.

Phenolic compounds from Viscum album tinctures enhanced antitumor activity in melanoma murine cancer cells

Cancer is one of the biggest problems in public health worldwide. Plants have been shown important role in anticancer research. Viscum album L. (Santalaceae), commonly known as mistletoe, is a semi-parasitic plant that grows on different host trees. In complementary medicine, extracts from European mistletoe (Viscum album L.) have been used in the treatment of cancer. The study was conducted to identify chemical composition and antitumor potential of Viscum album tinctures. Chemical analysis performed by high resolution chromatography equipped with high resolution mass spectrometer identified caffeic acid, chlorogenic acid, sakuranetin, isosakuranetin, syringenin 4-O-glucoside, syringenin 4-O-apiosyl-glucoside, alangilignoside C and ligalbumoside A compounds. Some of these compounds are probably responsible for the reduction of tumoral cellular growth in a dose-dependent manner. It was observed that melanoma murine cells (B16F10) were more sensitive to V. album tinctures than human leukaemic cells (K562), besides non-tumoral cells (MA-104) had a much lower cytotoxicity to them. Apoptotic-like cells were observed under light microscopy and were confirmed by a typical DNA fragmentation pattern. Additionally, flow cytometry results using Annexin-V/FITC permitted to quantify increased expression of early and late apoptotic markers on tumoral cells, confirming augmented Sub G0 population, which was probably associated with a consistent decrease in G1, and an increase in S or G2/M populations. Results indicate the chemical composition of V. album tinctures influences the mechanisms of in vitro tumoral cell death, suggesting a potential use in cancer pharmacotherapy research.

Cardioprotective effects of Viscum album L. subsp. album (European misletoe) leaf extracts in myocardial ischemia and reperfusion

ETHNOPHARMACOLOGICAL RELEVANCE

Viscum album L. (European mistletoe) is a hemiparasitic plant belonging to Loranthaceae family and has been used in Turkish traditional medicine for the treatment of cardiovascular disorders and heart diseases such as hypertension, tachycardia and angina pectoris.

AIM OF THE STUDY

The present study investigated the cardioprotective effects of V. album leaf extracts in myocardial ischemia and reperfusion injury in rats.

MATERIAL AND METHODS

Lyophilized aqueous (AVa) and methanolic (MVa) extracts of V. album were prepared from dried leaf. The isolated hearts were perfused with V. album extracts prior to and during 35min of ischemia induced by coronary artery occlusion. After 120min of coronary reperfusion, infarct size was determined by triphenyltetrazolium staining.

RESULTS

Both AVa and MVa extracts reduced the extent of infarction compared with untreated control hearts, but protective effect of MVa had more potential in low concentration; infarct size as proportion of ischemic risk zone: AVa 17.5±1.5%; Mva 20.3±2.5%, both P<0.01 versus control 38.1±1.4%. This protective effect was comparable to infarct limitation induced by ischemic preconditioning (21.5±2.4%). Inhibition of nitric oxide synthesis with L-N^G-nitroarginine methyl ester completely abrogated the protection afforded by both extracts. ATP-sensitive K⁺ channel blockade by glibenclamide abrogated the protection afforded by MVa while attenuating, but not abolishing, the protective action of Ava.

CONCLUSIONS

This study provided the first experimental evidence that V. album leaf extracts can mediate nitric oxide-dependent cardioprotection against myocardial injury produced by ischemia/reperfusion insult. With this study, popular usage of V. album extracts in Turkish folk medicine as a remedy for cardiac diseases was justified.

Viscum album neutralizes tumor-induced immunosuppression in a human in vitro cell model

Tumor cells have the capacity to secrete immunosuppressive substances in order to diminish dendritic cell (DC) activity and thereby escape from immune responses. The impact of mistletoe (Viscum album) extracts (VAE), which are frequently used as an additive anti-cancer therapy to stimulate the immune response, is still unknown. Using a human cellular system, the impact of two different VAE (VAEA + VAEI) on the maturation of human dendritic cells and on T cell function has been investigated using flow cytometry, automated fluorescence microscopy and cytokine bead array assays. Furthermore, we examined whether VAEI was able to counteract tumor-induced immunosuppression within this cellular system using a renal cancer cell model. The role of mistletoe lectin (ML) was analyzed using ML-specific antibodies and ML-depleted VAEI. VAEI and VAEA augmented the maturation of dendritic cells. VAEI abrogated tumor-induced immunosuppression of dendritic cells and both processes were partially mediated by ML since ML-depleted VAEI and ML-specific antibodies almost neutralized the rehabilitative effects of VAEI on DC maturation. Using these settings, co-culture experiments with purified CD4⁺ T cells had no influence on T cell proliferation and activation but did have an impact on IFN-γ secretion. The study provides a potential mode-of-action of VAE as an additive cancer therapy based on immunomodulatory effects. However, the impact on the in vivo situation has to be evaluated in further studies.

Iscador Qu inhibits doxorubicin-induced senescence of MCF7 cells

Chemotherapy in patients with inoperable or advanced breast cancer inevitably results in low-dose exposure of tumor-cell subset and senescence. Metabolically active senescent cells secrete multiple tumor promoting factors making their elimination a therapeutic priority. Viscum album is one of the most widely used alternative anti-cancer medicines facilitating chemotherapy tolerance of breast cancer patients. The aim of this study was to model and investigate how Viscum album extracts execute additive anti-tumor activity with low-dose Dox using ER + MCF7 breast cancer cells. We report that cotreatment of MCF7 with Viscum album and Dox abrogates G2/M cycle arrest replacing senescence with intrinsic apoptotic program. Mechanistically, this switch was associated with down-regulation of p21, p53/p73 as well as Erk1/2 and p38 activation. Our findings, therefore, identify a novel mechanistic axis of additive antitumor activity of Viscum album and low dose-Dox. In conclusion, ER + breast cancer patients may benefit from addition of Viscum album to low-dose Dox chemotherapy due to suppression of cancer cell senescence and induction of apoptosis.

Impact of Mistletoe Triterpene Acids on the Uptake of Mistletoe Lectin by Cultured Tumor Cells

Complementary treatment possibilities for the therapy of cancer are increasing in demand due to the severe side effects of the standard cytostatics used in the first-line therapy. A common approach as a complementary treatment is the use of aqueous extracts of Viscum album L. (Santalaceace). The therapeutic activity of these extracts is attributed to Mistletoe lectins which are Ribosome-inactivating proteins type II. Besides these main constituents the extract of Viscum album L. comprises also a mixture of lipophilic ingredients like triterpene acids of the oleanane, lupane and ursane type. However, these constituents are not contained in commercially available aqueous extracts due to their high lipophilicity and insolubility in aqueous extraction media. To understand the impact of the extract ingredients in cancer therapy, the intracellular uptake of the mistletoe lectin I (ML) by cultured tumor cells was investigated in relation to the mistletoe triterpene acids, mainly oleanolic acid. Firstly, these hydrophobic triterpene acids were solubilized using cyclodextrins (“TT” extract). Afterwards, the uptake of either single compounds (isolated ML and the aqueous “viscum” extract) or in combination with the TT extract (ML+TT, viscumTT), was analyzed. The uptake of ML was studied inTHP-1-, HL-60-, 143B- and Ewing TC-71-cells and determined after 30, 60 and 120 minutes by an enzyme linked immunosorbent assay which quantifies the A-chain of the hololectin. It could be shown that the intracellular uptake after 120 minutes amounted to 20% in all cell lines after incubation with viscumTT. The studies further revealed that the uptake in THP-1-, HL-60- and Ewing TC-71-cells was independent of the addition of TT extract. Interestingly, the uptake of ML by 143B-cells could only be measured after addition of triterpenes pointing to resistance to mistletoe lectin.

Bridging cross-cultural gaps: monitoring herbal use during chemotherapy in patients referred to integrative medicine consultation in Israel

INTRODUCTION

The high prevalence of the use of traditional herbs among patients with cancer is a cause for concern with regard to potentially adverse interactions with conventional oncology treatments. In this study, we explore herbal use among patients with cancer in northern Israel who are referred by their health care providers to complementary and traditional medicine (CTM) consultations provided to them within the conventional oncology department. The study's objectives were to identify which herbs patients use and to examine the scope of current research on the efficacy and safety regarding the identified herbs.

PATIENTS AND METHODS

Herbal use by patients receiving oncology care was assessed prospectively from July 2009 to July 2012 by integrative physicians (IPs) trained in herbal medicine. Historical, ethnobotanical, basic research, and clinical data regarding the identified herbs were explored by using a keyword search in PubMed and Middle Eastern ethnohistorical literature.

RESULTS

Disclosure of herbal use was reported by 154 of the 305 patients (50.5 %) interviewed by IPs. The use of 85 single herbs and 30 different herbal formulas was documented during the initial or follow-up IP assessments. Patients reported 14 quality of life-associated indications for herbal use. The ten most prevalent herbs displaying in vitro/in vivo anticancer activity and nine other herbs were preliminarily assessed concerning potential risks, safety, and interaction with chemotherapy.

CONCLUSIONS

Herbal use by patients with cancer in northern Israel is widespread and calls for further study in order to address issues of safety and effectiveness. We recommend constructing a multinational and multidisciplinary team of researchers with ethnopharmacological and clinical expertise that will explore the use of herbs among patients with cancer in a cross-cultural perspective attuned with patients' affinity to traditional herbal medicine.

Anthroposophic medicine: an integrative medical system originating in europe

Anthroposophic medicine is an integrative multimodal treatment system based on a holistic understanding of man and nature and of disease and treatment. It builds on a concept of four levels of formative forces and on the model of a three-fold human constitution. Anthroposophic medicine is integrated with conventional medicine in large hospitals and medical practices. It applies medicines derived from plants, minerals, and animals; art therapy, eurythmy therapy, and rhythmical massage; counseling; psychotherapy; and specific nursing techniques such as external embrocation. Anthroposophic healthcare is provided by medical doctors, therapists, and nurses. A Health-Technology Assessment Report and its recent update identified 265 clinical studies on the efficacy and effectiveness of anthroposophic medicine. The outcomes were described as predominantly positive. These studies as well as a variety of specific safety studies found no major risk but good tolerability. Economic analyses found a favorable cost structure. Patients report high satisfaction with anthroposophic healthcare.

A new development of triterpene acid-containing extracts from Viscum album L. displays synergistic induction of apoptosis in acute lymphoblastic leukaemia

OBJECTIVES

Aqueous Viscum album L. extracts are widely used for anti-cancer therapies. Due to their low solubility, triterpenes (which are known to act on cancers), do not occur in aqueous extracts in significant amounts. Using cyclodextrins, we have found it possible to solubilize mistletoe triterpene acids and to determine their effects on acute lymphoblastic leukaemia (ALL) in vitro and in vivo.

MATERIALS AND METHODS

A C.B-17/SCID model of pre-B ALL (NALM-6) was used to test efficacy and mechanisms of treatment with lectin- and triterpene acid containing preparations in vivo. Cytotoxicity of increasing concentrations of V. album L. preparations was assessed in vitro. Apoptosis was determined using mitochondrial membrane potential measurements, annexin V/PI, western blot analyses and caspase inhibitor assays.

RESULTS

Solubilized triterpene acid- or lectin-containing V. album L. extracts inhibited cell proliferation and demonstrated cytotoxic properties in vitro. Annexin V/PI and mitochondrial membrane potential assays indicated that dose-dependent induction of apoptosis was the main mechanism. Combination (viscumTT) of lectin- (viscum) and triterpene-containing (TT) extracts resulted in greatest induction of apoptosis. Furthermore, caspase activity demonstrated that these extracts were able to induce apoptosis through both caspase-8 and -9 dependent pathways. In vivo experimentation showed that treatment of mice with viscumTT combination prolonged mean survival to 50.5 days compared to 39.3 days in the phosphate-buffered saline group.

CONCLUSION

Here for the first time, we have demonstrated that either solubilized triterpene acids or lectins and combinations thereof, induce dose-dependent apoptosis in the ALL cell line NALM-6 via caspase-8 and -9 dependent pathways.

Integrative oncology in the Middle East: from traditional herbal knowledge to contemporary cancer care

BACKGROUND

Based on traditional, historical, ethnobotanical, laboratory, and clinical findings, we present research framework aiming to identify Middle Eastern herbs that are worthy of further research for their anticancer potential.

METHODS

A comprehensive research project was developed by a multinational team comprising family physicians, medicine specialists, oncologists, an Islamic medicine history specialist, a traditional medicine ethnobotanist, and a basic research scientist. The project followed two consecutive phases: (i) historical and ethnobotanical search for cancer-related keywords and (ii) Medline search for in vitro and in vivo studies.

RESULTS

This search yielded 44 herbs associated with cancer care. The Medline search yielded 34 herbs of which 9 herbs were reported in various clinical studies.

CONCLUSIONS

This multidisciplinary survey was found to be a valuable way to identify herbs with potential clinical significance in cancer care. Based on this pilot study, it is suggested that the Middle East can serve as a valuable region for future multicultural-oriented cancer research.

Down-regulation of some miRNAs by degrading their precursors contributes to anti-cancer effect of mistletoe lectin-I

BACKGROUND AND PURPOSE

Mistletoe lectin-I (ML-I), the main anti-cancer component of mistletoe extracts, was originally thought to act exclusively on 28S rRNA. Here, we investigate the down-regulating effect and mechanism of CM-1, an ML-I isolated from Chinese mistletoe, on some miRNAs.

EXPERIMENTAL APPROACH

The anti-cancer effects of CM-1 were assessed in vitro and in vivo in colorectal cancer cells. The miRNAs down-regulated by CM-1 were identified by miRNA microarray assay and validated by qRT-PCR analysis. The suppression of host gene transcription or by degradation of precursors was determined by qRT-PCR and enzyme activity assays respectively. The qRT-PCR, Western blot and immunohistochemistry were used to examine the expression of their target gene and related downstream effector. Cell proliferation was assayed in stably transfected HEK-293 cells with different levels of these miRNAs.

KEY RESULTS

CM-1 showed prominent anti-neoplastic activity towards CLY and HT-29 cells both in vitro and in vivo. The miR-135a&b were the miRNAs most down-regulated by CM-1. Their host gene transcription was largely up-regulated, while their precursors were degraded directly by CM-1. The expression of their target gene adenomatous polyposis coli and the phosphorylation of related effector β-catenin were both significantly up-regulated. The IC(50) values of CM-1 on derivative HEK-293 cells with high miR-135a&b levels were 2-4 times lower than that of control cells.

CONCLUSIONS AND IMPLICATIONS

CM-1 down-regulated some miRNAs by degrading their precursors, which contributes to its prominent anti-cancer activity.

Herbs in hemato-oncological care: an evidence-based review of data on efficacy, safety, and drug interactions

Herbal remedies are clearly a complementary and alternative modality used frequently by patients with hemato-oncological neoplasias during the course of their specific treatment. This review focuses on the potential safety and efficacy of herbs which are either used often or even on a daily basis by patients with hematological malignancies or indicated in the herbal pharmacopeias utilized by various traditional systems of medicine, in order to improve the well-being of patients with these cancers. Traditional medicine worldwide is a source for ongoing laboratory research related to the activity of herbs on cultured cell lines derived from patients with leukemia, lymphoma, and myeloma. Although the number of clinical studies in the field of hemato-oncology is limited, there appears to be potential efficacy in studies of mistletoe (Viscum album), green tea, Indian and Middle-Eastern spices, and some traditional Chinese, American, and European herbs. In addition to the potential efficacy of herbs, safety issues are also reviewed here, particularly, the documented and potential side effects, herb-drug interactions, and matters of quality control. Based on the above issues, the authors suggest enhancing doctor-patient communication regarding herbal use by adopting a patient-centered attitude based on scientific perspective.

Review article: Influence of Viscum album L (European mistletoe) extracts on quality of life in cancer patients: a systematic review of controlled clinical studies

OBJECTIVE

To evaluate controlled clinical studies on the efficacy and effectiveness of Viscum album for quality of life (QoL) in cancer.

MATERIALS AND METHODS

The authors conducted a search of 7 electronic databases and reference lists and had extensive consultations with experts. They carried out a criteria-based assessment of methodological study quality.

RESULTS

The authors identified 26 randomized controlled trials (RCTs) and 10 non-RCTs that investigated the influence of V album extracts (VAEs) on QoL in malignant diseases; 26 studies assessed patient-reported QoL. Questionnaires were mostly well established and validated. Half of the studies investigated VAEs concomitant with chemotherapy, radiotherapy, or surgery. Some studies were well designed, whereas others had minor or major methodological weaknesses. Among the 26 RCTs, 22 reported a QoL benefit, 3 indicated no difference, and 1 did not report any result. All the non-RCTs reported a QoL benefit. Of the studies with higher methodological quality, most reported a benefit, whereas 1 found no difference. Improvements were mainly in regard to coping, fatigue, sleep, exhaustion, energy, nausea, vomiting, appetite, depression, anxiety, ability to work, and emotional and functional well-being in general and, less consistently, in regard to pain, diarrhea, general performance, and side effects of conventional treatments. VAEs were well tolerated.

CONCLUSIONS

VAEs seem to have an impact on QoL and reduction of side effects of conventional therapies (chemotherapy, radiation) in experimental trials as well as in routine daily application. The influence on fatigue especially should be investigated further.

Viscum album L. extracts in breast and gynaecological cancers: a systematic review of clinical and preclinical research

BACKGROUND

Viscum album L. extracts (VAE, European mistletoe) are a widely used medicinal plant extract in gynaecological and breast-cancer treatment.

METHODS

Systematic review to evaluate clinical studies and preclinical research on the therapeutic effectiveness and biological effects of VAE on gynaecological and breast cancer. Search of databases, reference lists and expert consultations. Criteria-based assessment of methodological study quality.

RESULTS

19 randomized (RCT), 16 non-randomized (non-RCT) controlled studies, and 11 single-arm cohort studies were identified that investigated VAE treatment of breast or gynaecological cancer. They included 2420, 6399 and 1130 patients respectively. 8 RCTs and 8 non-RCTs were embedded in the same large epidemiological cohort study. 9 RCTs and 13 non-RCTs assessed survival; 12 reported a statistically significant benefit, the others either a trend or no difference. 3 RCTs and 6 non-RCTs assessed tumour behaviour (remission or time to relapse); 3 reported statistically significant benefit, the others either a trend, no difference or mixed results. Quality of life (QoL) and tolerability of chemotherapy, radiotherapy or surgery was assessed in 15 RCTs and 9 non-RCTs. 21 reported a statistically significant positive result, the others either a trend, no difference, or mixed results. Methodological quality of the studies differed substantially; some had major limitations, especially RCTs on survival and tumour behaviour had very small sample sizes. Some recent studies, however, especially on QoL were reasonably well conducted. Single-arm cohort studies investigated tumour behaviour, QoL, pharmacokinetics and safety of VAE. Tumour remission was observed after high dosage and local application. VAE application was well tolerated. 34 animal experiments investigated VAE and isolated or recombinant compounds in various breast and gynaecological cancer models in mice and rats. VAE showed increase of survival and tumour remission especially in mice, while application in rats as well as application of VAE compounds had mixed results. In vitro VAE and its compounds have strong cytotoxic effects on cancer cells.

CONCLUSION

VAE shows some positive effects in breast and gynaecological cancer. More research into clinical efficacy is warranted.

The anti-cancer effects of poi (Colocasia esculenta) on colonic adenocarcinoma cells In vitro

Hawaiians tend to have lower incidence rates of colorectal cancer and it was hypothesized that this may be due to ethnic differences in diet, specifically, their consumption of poi, a starchy paste made from the taro (Colocasia esulenta L.) plant corm. Soluble extracts of poi were incubated at 100 mg/mL in vitro for antiproliferative activity against the rat YYT colon cancer cell line. (3)H-thymidine incorporation studies were conducted to demonstrate that the poi inhibited the proliferation of these cancer cells in a dose-dependent manner. The greatest suppression of YYT colon cancer growth occurred when 25% concentration was used. When poi was incubated with the YYT cells after 2 days, the YYT cells underwent apoptotic changes as evidenced by a positive terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) stain. Poi enhanced the proliferation of normal mouse splenocyte control cells, suggesting that poi is not simply toxic to all cells but even has a positive immunostimulatory role. By flow cytometry, T cells (CD4+ and CD8+) were predominantly activated by the poi. Although numerous factors can contribute to the risk of colon cancer, perhaps poi consumption may contribute to the lower colon cancer rates among Hawaiians by two distinct mechanisms. First, by inducing apoptosis within colon cancer cells; second, by non-specifically activating lymphocytes, which in turn can lyse cancerous cells. Our results suggest for the first time that poi may have novel tumor specific anti-cancer activities and future research is suggested with animal studies and human clinical trials.

Analysis of unconventional approaches for the rapid detection of surface lectin binding ligands on human cell lines

For over a decade our laboratory has developed and used a novel histochemical assay using derivatized agarose beads to examine the surface properties of various cell types. Most recently, we have used this assay to examine lectin binding ligands on two human cell types, CCL-220, a colon cancer cell line, and CRL-1459, a non-cancer colon cell line. We found that CCL-220 cells bound specific lectins better than CRL-1459, and this information was used to test for possible differential toxicity of these lectins in culture, as a possible approach in the design of more specific anti-cancer drugs. Although we have examined the validity of the bead-binding assay in sea urchin cell systems, we have not previously validated this technique for mammalian cells. Here the binding results of the bead assay are compared with conventional fluorescence assays, using lectins from three species (Triticum vulgaris, Phaseolus vulgaris, and Lens culinaris) on the two colon cell lines. These lectins were chosen because they seemed to interact with the two cell lines differently. Binding results obtained using both assays were compared for frozen, thawed and fixed; cultured and fixed; and live cells. Both qualitative and quantitative fluorescence results generally correlated with those using the bead assay. Similar results were also obtained with all of the three different cell preparation protocols. The fluorescence assay was able to detect lower lectin binding ligand levels than the bead assay, while the bead assay, because it can so rapidly detect cells with large numbers of lectin binding ligands, is ideal for initial screening studies that seek to identify cells that are rich in surface binders for specific molecules. The direct use of frozen, thawed and fixed cells allows rapid mass screening for surface molecules, without the requirement for costly and time consuming cell culture.

Direct targeting of cancer cells: a multiparameter approach

Lectins have been widely used in cell surface studies and in the development of potential anticancer drugs. Many past studies that have examined lectin toxicity have only evaluated the effects on cancer cells, not their non-cancer counterparts. In addition, few past studies have evaluated the relationship between lectin-cell binding and lectin toxicity on both cell types. Here we examine these parameters in one study: lectin-cell binding and lectin toxicity with both cancer cells and their normal counterparts. We found that the human colon cancer cell line CCL-220/Colo320DM bound to agarose beads derivatized with Phaseolus vulgaris agglutinin (PHA-L) and wheat germ agglutinin (WGA), while the non-cancer human colon cell line CRL-1459/CCD-18Co did not. When these lectins were tested for their effects on cell viability in culture, both cell lines were affected by the lectins but at 6, 48 and 72 h incubation times, PHA-L was most toxic to the cancer cell line in a concentration dependent manner. At 48 h incubation, WGA was more toxic to the cancer cell line. The results suggest that it may be possible to develop lectin protocols that selectively target cancer cells for death. In any case, examination of both malignant cells and their non-malignant counterparts, analysis of their binding characteristics to immobilized lectins, and examination of the toxicity of free lectins in culture, provides a multiparameter model for obtaining more comprehensive information than from more limited approaches.

Influence of mistletoe lectins and cytokines induced by them on cell proliferation of human melanoma cells in vitro

Although aqueous mistletoe extracts are widely used in complementary cancer therapy, the precise mode of action of their main therapeutic agents, the three mistletoe lectins (MLs), is poorly understood as they act both as cytotoxic agents and as immunomodulators due to their cytokine release by mononuclear cells. Thus, this study aims to investigate both the direct and the indirect effects of MLs on the growth of human melanoma cells in vitro. Proliferation of six human melanoma cell lines under ML treatment and additionally under the influence of cytokines induced by them (TNF-alpha, IL-1, IL-6) was assessed by means of the tetrazolium derived reduction (XTT) assay. Furthermore, ML binding patterns were analysed and correlated with the biological effects. All three MLs inhibited melanoma cell proliferation in a dose-dependent manner starting at very low ML concentrations (0.001-100 ng/ml) with ML-I being the most cytotoxic lectin (significant inhibition of ultra-sensitive cell line MV3 at 1 x 10(-13) ng ML-I/ml). Even if applied in a broad concentration range (0.0001-100 ng/ml) cytokines had no influence on cell proliferation at all. For ML-I, no association between binding intensity and cytotoxicity was observed, while for ML-II and -III an association between binding and toxicity was established. In conclusion, this study emphasises the direct anti-proliferative effect of the mistletoe lectins on melanoma cells with ML-I being superior to MLs-II and -III. The observation of an ultra-sensitivity of one cell line towards ML-I toxicity may serve as an explanation for the therapeutic success in anecdotal case reports and needs further investigations.

Mistletoe viscotoxins increase natural killer cell-mediated cytotoxicity

Mistletoe extracts have immunomodulatory activity. We show that nontoxic concentrations of Viscum album extracts increase natural killer (NK) cell-mediated killing of tumor cells but spare nontarget cells from NK lysis. The compounds responsible for this bioactivity were isolated from mistletoe and characterized. They have low molecular mass and are thermostable and protease-resistant. After complete purification by HPLC, they were identified by tandem MS as viscotoxins A1, A2 and A3 (VTA1, VTA2 and VTA3, respectively). Whereas micromolar concentrations of these viscotoxins are cytotoxic to the targets, the bioactivity with respect to NK lysis is within the nanomolar range and differs between viscotoxin isoforms: VTA1 (85 nm), VTA2 (18 nm) and VTA3 (8 nm). Microphysiometry and assays of cell killing indicate that, within such nontoxic concentrations, viscotoxins do not activate NK cells, but act on cell conjugates to increase the resulting lysis.