Natural Products as Anti-Cancerous Therapeutic Molecules Targeted towards Topoisomerases.

Topoisomerases are reported to resolve the topological problems of DNA during several cellular processes, such as DNA replication, transcription, recombination, and chromatin remodeling. Two types of topoisomerases (Topo I and II) accomplish their designated tasks by introducing single- or double-strand breaks within the duplex DNA molecules, and thus maintain the proper structural conditions of DNA to release the topological torsions, which is generated by unwinding of DNA to access coded information, in the course of replication, transcription, and other processes. Both the topoisomerases have been looked at as crucial targets against various types of cancers such as lung, melanoma, breast, and prostate cancers. Conceptually, targeting topoisomerases will disrupt both DNA replication and transcription, thereby leading to inhibition of cell division and consequently stopping the growth of actively dividing cancerous cells. Since the discovery of camptothecin (an alkaloid) as an inhibitor of Topo I in 1958, a number of derivatives of camptothecin were developed as potent inhibitors of Topo I. Two such derivatives of camptothecin, namely, topotecan and irinotecan, have been commonly used as US Food and Drug Administration (FDA) approved drugs against Topo I. Similarly, the first Topo II inhibitor, namely, etoposide, an analogue of podophyllotoxin, was developed in 1966 and got FDA approval as an anti-cancer drug in 1983. Subsequently, several other inhibitors of Topo II, such as doxorubicin, mitoxantrone, and teniposide, were developed. These drugs have been reported to cause accumulation of cytotoxic non-reversible DNA double-strand breaks (cleavable complex). Thus, the present review describes the anticancer potential of plant-derived secondary metabolites belonging to alkaloids, flavonoids and terpenoids directed against topoisomerases. Furthermore, in view of the recent advances made in the field of computer-aided drug design, the present review also discusses the use of computational approaches such as ADMET, molecular docking, molecular dynamics simulation and QSAR to assess and predict the safety, efficacy, potency and identification of these potent anti-cancerous therapeutic molecules.

Methylation-Sensitive High Resolution Melting (MS-HRM).

Methylation-Sensitive High Resolution Melting (MS-HRM) is an in-tube, PCR-based method to detect methylation levels at specific loci of interest. A unique primer design facilitates a high sensitivity of the assays enabling detection of down to 0.1-1% methylated alleles in an unmethylated background.Primers for MS-HRM assays are designed to be complementary to the methylated allele, and a specific annealing temperature enables these primers to anneal both to the methylated and the unmethylated alleles thereby increasing the sensitivity of the assays. Bisulfite treatment of the DNA prior to performing MS-HRM ensures a different base composition between methylated and unmethylated DNA, which is used to separate the resulting amplicons by high resolution melting.The high sensitivity of MS-HRM has proven useful for detecting cancer biomarkers in a noninvasive manner in urine from bladder cancer patients, in stool from colorectal cancer patients, and in buccal mucosa from breast cancer patients. MS-HRM is a fast method to diagnose imprinted diseases and to clinically validate results from whole-epigenome studies. The ability to detect few copies of methylated DNA makes MS-HRM a key player in the quest for establishing links between environmental exposure, epigenetic changes, and disease.

Synthesis and structure elucidation of novel salophen-based dioxo-uranium(VI) complexes: In-vitro and in-silico studies of their DNA/BSA-binding properties and anticancer activity.

The synthesis and characterization of three dioxo U(VI) complexes, [UO2(L1)(OH2)], [UO2(L2)DMF], and [UO2(L2)DMSO], [L1]2- = 1,1'-(4-methyl-1,2-phenylenebis (nitrilomethylidyne))di-2-naphtholate: [L2]2- = 1,1'-(o-phenylenebis (nitrilomethylidyne)) di-2-naphtholate, are reported. Elemental analysis, FT-IR, 1HNMR, UV-Vis spectroscopy, molar conductivity and single crystal X-ray diffraction were used to characterize the complexes. It was found that the complexes adopt a distorted pentagonal bipyramidal coordination geometry. The interaction of the synthesized complexes with DNA and bovine serum albumin was thoroughly investigated using both experimental and theoretical studies. UV-Vis absorption and fluorescence quenching techniques were applied to determine the binding parameters as well as the mechanism of the interaction of each complex with DNA and the protein. The results obtained suggested that interaction of the complexes with DNA occurred through partial intercalation into the minor grooves of DNA with binding constants in the range of 0.661 × 105-1.56 × 105 M-1. In addition, interaction of the complexes with bovine serum albumin quenched the fluorescence emission of the tryptophan residues of the protein binding constants and thermodynamic parameters were obtained from the fluorescence quenching experiments at different temperatures. The values of binding constants revealed moderate interactions between the synthesized complexes and the protein suggesting that this protein could act as a suitable vehicle for transportation of the compounds. The results of molecular docking confirmed those of the experimental studies. The anticancer properties of the title complexes were also evaluated through a study of the in vitro cytotoxicity of the compounds against the HT-29 and MCF-7 cancer cell lines and the DPSC normal cell line using an MTT assay.

Role of ion channels in ionizing radiation-induced cell death.

Neoadjuvant, adjuvant or definitive fractionated radiation therapy are implemented in first line anti-cancer treatment regimens of many tumor entities. Ionizing radiation kills the tumor cells mainly by causing double strand breaks of their DNA through formation of intermediate radicals. Survival of the tumor cells depends on both, their capacity of oxidative defense and their efficacy of DNA repair. By damaging the targeted cells, ionizing radiation triggers a plethora of stress responses. Among those is the modulation of ion channels such as Ca2+-activated K+ channels or Ca2+-permeable nonselective cation channels belonging to the super-family of transient receptor potential channels. Radiogenic activation of these channels may contribute to radiogenic cell death as well as to DNA repair, glucose fueling, radiogenic hypermigration or lowering of the oxidative stress burden. The present review article introduces these channels and summarizes our current knowledge on the mechanisms underlying radiogenic ion channel modulation. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.

Heterologous expression and functional characterization of matrix metalloproteinase-11 from canine mammary tumor.

Matrix metalloproteinases (MMPs) are reported to be involved in tumor growth, apoptosis, angiogenesis, invasion, and development of metastases. These are zinc containing metalloproteases, known for their role in extracellular matrix degradation. MMP-11 (stromelysin3) is reported to be highly expressed in breast cancer, therefore it may act as marker enzyme for breast cancer progression. The present work was carried out to produce recombinant canine (Canis lupus familiaris) MMP-11 lacking the signal and propeptide in E. coli by optimizing its expression and purification in biologically active form and to functionally characterize it. A bacterial protein expression vector pPROEX HTc was used. The MMP-11 mature peptide encoding gene was successfully cloned and expressed in E. coli and the purified recombinant enzyme was found to be functionally active. The recombinant enzyme exhibited caseinolytic activity and could be activated by Trypsin and 4-Amino phenyl mercuric acetate (APMA). However Ethylene diamine tertra acetate (EDTA) inhibited the enzyme's caseinolytic activity. The recombinant enzyme degraded extracellular matrix constituents and facilitated migration of MDCK (Madin-Darby canine kidney) cells through BD Biocoat Matrigel invasion chambers. These results suggest that in vivo MMP-11 could play a significant role in the turnover of extracellular matrix constituents.

Association of CASP9, CASP10 gene polymorphisms and tea drinking with colorectal cancer risk in the Han Chinese population.

The initiators caspase-9 (CASP9) and caspase-10 (CASP10) are two key controllers of apoptosis and play important roles in carcinogenesis. This study aims to explore the association between CASPs gene polymorphisms and colorectal cancer (CRC) susceptibility in a population-based study. A two-stage designed population-based case-control study was carried out, including a testing set with 300 cases and 296 controls and a validation set with 206 cases and 845 controls. A total of eight tag selected single nucleotide polymorphisms (SNPs) in CASP9 and CASP10 were chosen based on HapMap and the National Center of Biotechnology Information (NCBI) datasets and genotyped by restriction fragment length polymorphism (RFLP) assay. Multivariate logistic regression models were applied to evaluate the association of SNPs with CRC risk. In the first stage, from eight tag SNPs, three polymorphisms rs4646077 (odds ratio (OR)(AA+AG): 0.654, 95% confidence interval (CI): 0.406-1.055; P=0.082), rs4233532 (OR(CC): 1.667, 95% CI: 0.967-2.876; OR(CT): 1.435, 95% CI: 0.998-2.063; P=0.077), and rs2881930 (OR(CC): 0.263, 95% CI: 0.095-0.728, P=0.036) showed possible association with CRC risk. However, none of the three SNPs, rs4646077 (OR(AA+AG): 1.233, 95% CI: 0.903-1.683), rs4233532 (OR(CC): 0.892, 95% CI: 0.640-1.243; OR(CT): 1.134, 95% CI: 0.897-1.433), and rs2881930 (OR(CC): 1.096, 95% CI: 0.620-1.938; OR(CT): 1.009, 95% CI: 0.801-1.271), remained significant with CRC risk in the validation set, even after stratification for different tumor locations (colon or rectum). In addition, never tea drinking was associated with a significantly increased risk of CRC in testing set together with validation set (OR: 1.755, 95% CI: 1.319-2.334). Our results found that polymorphisms of CASP9 and CASP10 genes may not contribute to CRC risk in Chinese population and thereby the large-scale case-control studies might be in consideration. In addition, tea drinking was a protective factor for CRC.

A comparative study of the antioxidant/prooxidant effects of carvacrol and thymol at various concentrations on membrane and DNA of parental and drug resistant H1299 cells.

Carvacrol and thymol, both used as flavor agents in cosmetic and food products, have prooxidant and antioxidant activities. To clarify the mechanisms of their cytotoxicity and the factors affecting their antioxidant/prooxidant activities, we investigated cell membrane and DNA damage induced by carvacrol and thymol in parental and drug-resistant human lung cancer cell lines. After 24 and 48 hour incubation periods, the cytotoxicity of carvacrol (IC50 380 and 244 microM) was found to be higher than that of thymol (IC50 497 and 266 microM) in parental cells. However, thymol showed higher cytotoxic effects in drug resistant H1299 cells for three incubation periods. Also, carvacrol and thymol, at higher concentrations, increased malondealdehyde (MDA) levels causing membrane damage and 8-hydroxy deoxyguanozine (8-OHdG) levels, causing DNA damage to both parental and drug resistant cells. On the other hand, carvacrol and thymol protected the cells against H2O2-induced cytotoxicity, and membrane and DNA damage when the cells were preincubated with these two compounds at lower concentration (< IC50) before H2O2 incubation. These findings suggest that carvacrol and thymol exhibit protective/damaging effects depending on cell resistance, concentration and time.

Screening DNA-targeted anticancer drug in vitro based on the drug-conjugated DNA by resonance light scattering technique.

A sensitive and reliable assay has been developed to directly screen DNA-targeted anticancer drugs in vitro via using resonance light scattering (RLS) technique. The results of experiments displayed that the increment of RLS intensity was directly proportional to the antitumor effect of anticancer drugs. Through the RLS spectra, the activities of four drugs have been demonstrated as mitoxantrone (MIT)>epirarubicin (EPI)>daunorubicin (DAU)>adriamycin (ADM). However, to further verify the activities of the above four drugs, binding constant (k) for each of them has been calculated by RLS technique as follows: k(RLS) (MIT, 8.75 x 10(5) L mol(-1))>k(RLS) (EPI, 6.58 x 10(5) L mol(-1))>k(RLS) (DAU, 4.79 x 10(5) L mol(-1))>k(RLS) (ADM, 3.82 x 10(5) L mol(-1)). Also, this RLS assay result was validated by seasoned vitro screening methods for anticancer drugs. In all, the proposed RLS is not only a simple, sensitive, objective and straightforward method, but also it is an unprecedented assay for primarily screening DNA-targeted anticancer drugs.

Galloylated catechins as potent inhibitors of hypochlorous acid-induced DNA damage.

Hypochlorous acid (HOCl), a strong oxidant derived from myeloperoxidase in neutrophils and macrophages, can chlorinate DNA bases at the site of inflammation. Because little is known about the protective role of natural antioxidants, such as polyphenols, for the myeloperoxidase-derived DNA damage, we screened the inhibitory effects of various phenolic antioxidants on the chlorination of the 2'-deoxycytidine residue by HOCl in vitro and found that green tea catechins, especially (-)-epicatechin gallate (ECg) and (-)-epigallocatechin gallate (EGCg), significantly inhibited the chlorination. These catechins also reduced nucleoside- and taurine-chloramines, which can induce secondary oxidative damage, into their native forms. Mass spectrometric and nuclear magnetic resonance analyses showed that ECg and EGCg can effectively scavenge HOCl and/or chloramine species resulting in the formation of mono- and dichlorinated ECg and EGCg. Using the HL-60 human leukemia cell line, it was found that ECg could efficiently accumulate in the cells. Immunocytometric analyses using antihalogenated 2'-deoxycytidine antibody showed that pretreatment of cells with ECg inhibited the HOCl-induced immunofluorescence. In addition, the chlorinated ECg derivatives were detected in the HOCl-treated HL-60 cells. These results showed that green tea catechins, especially 3-galloylated catechins, may be the plausible candidate for the prevention of inflammation-derived DNA damage and perhaps carcinogenesis.

Expression profiling and genetic alterations of the selenoproteins GI-GPx and SePP in colorectal carcinogenesis.

The trace element selenium is discussed as a chemopreventive agent in colorectal carcinogenesis. Selenocysteine-containing proteins, so-called selenoproteins, represent potential molecular targets for nutritive selenium supplementation. Due to their antioxidative potential, the selenoproteins gastrointestinal glutathione peroxidase (GI-GPx) and selenoprotein P (SePP) are considered to provide protection against reactive oxygen species (ROS), thereby reducing DNA damage and preventing development of colon cancer. GI-GPx and SePP are abundantly expressed in normal colon mucosa. Recently, we demonstrated both reduced SePP expression and increased GI-GPx expression in colorectal adenomas. In this study, we investigated the expression of SePP and GI-GPx in colorectal cancers compared with corresponding normal mucosa. Further, the occurrence of genetic alterations within the SePP and GI-GPx genes was analyzed. We observed a significant reduction or loss of SePP mRNA expression in colon cancers, whereas GI-GPx mRNA and protein expression varied between different tumor samples. In addition, we identified novel polymorphisms within the SePP and GI-GPx genes with so far unknown relevance for protein function. Our results argue against a general decrease of selenoprotein expression in colorectal carcinogenesis but imply specific differential regulation of expression of individual selenoproteins.

p53 Mutations and microsatellite instability in ovarian cancer: Yin and yang.

OBJECTIVE: We tested the hypothesis that p53 frameshift mutations in ovarian cancer occur as a result of genomic instability rather than as a proximal cause of this process. STUDY DESIGN: Sequencing of the p53 tumor suppressor gene has been carried out on 305 ovarian, fallopian tube, and peritoneal cancers. Two groups of p53 null mutations were identified: (1) those caused by frameshift insertion or deletion mutations (n = 31) and (2) those caused by nonsense mutations (n = 28). As a control group 59 tumors with p53 missense mutations were selected by matching with the p53 null tumors on the basis of patient age at diagnosis, stage and grade of cancer, cancer site, and year of diagnosis. Microsatellite instability was determined from paired normal and tumor tissue deoxyribonucleic acid by means of the following different markers: D2S123, D5S346, D17S250, BAT25, and BAT26. Amplimers from polymerase chain reactions were evaluated on 7% polyacrylamide gels. RESULTS: The p53 null tumors were more likely to be of higher stage and grade. Fallopian tube cancers were more common (P =.02) in the p53 frameshift group. The overall incidence of microsatellite instability was 39%, 36%, and 25% for tumors with p53 frameshift nonsense and missense mutations (P =.30). Microsatellite instability was seen almost exclusively with ovarian cancer (P =.04). CONCLUSIONS: Microsatellite instability is a relatively common event in ovarian cancer and is dependent on marker selection. The p53 frameshift mutations do not appear to occur as a consequence of genomic instability.

Low incidence of p53 mutations in betel quid and tobacco chewing-associated oral squamous carcinoma from India.

Mutations of the p53 tumor suppressor gene have been found to be the single most frequent event in human cancers. In India and other southeast Asian countries tobacco chewing with betel quid was attributed to be the major factor in oral carcinogenesis. We have analyzed 72 untreated primary oral squamous cell carcinomas (SCCs) for mutations in the tumor suppressor gene p53 exons 4-9 by PCR-SSCP and DNA sequencing. Sequencing analysis revealed 16 missense mutations, one silent mutation in codon 307 and four A to G substitution polymorphism in codon 213. The incidence of p53 mutation was 21% (15 of 72) excluding the polymorphism and the silent mutation. Eight mutations were clustered in codons 266-282 of exon 8. Of the total mutation events 37.5% were G to A transitions and 31.3% were G to T transversions. These results indicate the possible involvement of tobacco derived nitrosamines and their adducts in the genesis of oral cancer among Indians.

Regulation of S100P expression by androgen.

BACKGROUND: The growth and function the normal prostate is dependent on the presence of androgen. As prostate tumors progress there is a loss of androgen-dependent cell growth. The identification of the genes that are regulated by androgens may be of pathological and clinical significance. METHODS: In this study the differential display method was used to identify genes regulated by androgen in an androgen-responsive prostate cancer cell line, LNCaP-FGC. RESULTS: A gene whose expression is down-regulated in LNCaP-FGC cells after 30 hr of androgen deprivation has been identified. This gene is a previously identified member of the S100 gene family of calcium-binding proteins, namely S100P. Here we show that S100P expression is regulated by the synthetic androgen R1881, but not by serum growth factors. It is dysregulated in the androgen-independent prostate cancer cell lines LNCaP-R, DU145, and PC3. CONCLUSIONS: The data indicate that S100P may play a role in the etiology of prostate cancer.

The mRNA expression of neurocan, a brain-specific chondroitin sulfate proteoglycan, in neoplastic mammary glands in mice.

In the experiment of mouse transforming growth factor alpha (TGF alpha) gene expression in mammary tumors, various sizes of amplified products by reverse transcriptase-polymerase chain reaction (RT-PCR) using mouse TGF alpha primers were detected in addition to a predicted size in four strains of mice. During the further analysis of these RT-PCR products in mouse mammary tumors, the transcript of neurocan gene was detected in the mammary tumor from SHN mice by the cloning and nucleotide sequence analysis after RT-PCR reaction using mouse TGF alpha primers. The 5'-nucleotide sequence of sequential 246bp in the amplified cDNA of 527bp was completely identical to a middle part of mouse neurocan cDNA sequence, one of the chondroitin-sulfate proteoglycan expressed in the nervous tissue.

Isolation and structure identification of an active DNA strand-scission agent, (+)-3,4-di-hydroxy-8,9-methylenedioxypterocarpan.

A new pterocarpan, (+)-3,4-dihydroxy-8,9-methylenedioxypterocarpan [1], was isolated from the flowers of Petalostemon purpureus by a DNA strand-scission assay-guided fractionation procedure. Compound 1 demonstrated activity in a standard in vitro DNA strand-scission assay, and cytotoxicity toward a KB tumor cell line. Two other related pterocarpans [2, 3] isolated from same plant were found to be moderately active for KB cells, but were inactive in the DNA strand-scission assay. (+)-4-Hydroxy-3-methoxy-8,9-methylenedioxypterocarpan [2] has not been reported previously as a natural product, while (+)-maackiain [3] has been isolated only as an optically inactive racemate along with its optical antipode, the (-)-isomer.

Cytotoxic activity of bryonolic acid isolated from transformed hairy roots of Trichosanthes kirilowii var. japonica.

Bryonolic acid was isolated in high yield from transformed hairy root cultures of Trichosanthes kirilowii var. Japonica. Bryonolic acid exhibited cytotoxic activity to various tumor cells in vitro, independent of cell type. Normal cells such as rat hepatocytes are less sensitive to bryonolic acid. The appearance of a DNA ladder was detected in the bryonolic acid-treated HL-60RG cells, indicating that cell death triggered by bryonolic acid is due to apoptosis.

Isolation of active genes containing CAG repeats by DNA strand invasion by a peptide nucleic acid.

An amplification of tandem CAG trinucleotide sequences in DNA due to errors in DNA replication is involved in at least four hereditary neurodegenerative diseases. The CAG triplet repeats when translated into protein give rise to tracts of glutamine residues, which are a prominent feature of many transcription factors, including the TATA-binding protein of transcription factor TFIID. We have used a biotin-labeled, complementary peptide nucleic acid (PNA) to invade the CAG repeats in intact chromatin and then employed a method for the selective isolation of transcriptionally active chromatin restriction fragments containing the PNA.DNA hybrids. The PNA-containing chromatin fragments were captured on streptavidin-agarose magnetic beads and shown to contain all the CAG.PNA hybrids of the active chromatin fraction. DNA hybridization experiments using a DNA probe specific for unique sequences downstream of the CAG-tandem repeats confirmed that the PNA.DNA hybrids contained the transcribed gene for the TATA-binding protein. In contrast, no hybridization signal was detected with a DNA probe specific for the c-myc protooncogene, which is amplified and transcriptionally active in COLO 320DM cells but lacks CAG tandem repeats.

In vitro evaluation of DNA-DNA hybridization as a two-step approach in radioimmunotherapy of cancer.

The specific delivery of radioisotopes to a tumor at minimal radiation of normal tissue is the ultimate aim of radioimmunotherapy. In this respect a two-step pretargeting regimen generally leads to an improved tumor to normal tissue uptake ratio compared to direct administration of radioimmunoconjugates. In this paper, in vitro studies are described in which the specific hybridization of complementary DNA fragments is the recognition mechanism in a pretargeting regimen comprising tumor cell saturation with a monoclonal antibody (MoAb)-oligonucleotide conjugate, followed by administration of the radiolabeled complementary oligonucleotide. Complementary oligodeoxynucleotides (15-mers; melting temperature, 68 degrees C) were prepared on a DNA synthesizer. The 5'-end was derivatized with a functional group for labeling with iodine, and the 3'-end was substituted with an amino function suitable for conjugation to an antibody (or attachment of a biotin residue). Both terminal modifications ensure stability of the oligonucleotides against exonucleases because the unconjugated form is stable for 24 h and the conjugated form is stable for several days when incubated in human plasma at 37 degrees C. Antibody-DNA conjugates were prepared by introduction of sulfhydryl groups into the oligonucleotide, followed by conjugation to maleimide-substituted MoAbs. Typically, 3 oligonucleotides were conjugated to an IgG, and 4-6 were conjugated to an IgM with preservation of immunoreactivity. Histochemistry on fresh frozen sections of breast cancer tissue demonstrated qualitatively the specificity of our two-step procedure. In vitro experiments with human tumor cell lines and tumor-specific MoAbs showed that, after saturation with tumor-specific MoAb-DNA conjugates, quantitative hybridization of the tumor cell-bound oligonucleotides occurred at a 30-fold excess of the labeled complementary oligonucleotide: hybridization was complete after 30 min of incubation. No reaction was observed with an irrelevant MoAb-DNA conjugate. The oligonucleotide was neither taken up by tumor cells or endothelial cells nor hybridized to a significant extent with human genomic DNA. These data indicate the feasibility of this two-step approach in radioimmunotherapy.

Studies of effects of anticancer agents in combination with/without hyperthermia on metastasized human bladder cancer cells in chick embryos using the polymerase chain reaction technique.

Cultivated T24 cells derived from a human bladder cancer were inoculated into the chorioallantoic membrane vein of chick embryos. Hyperthermic treatment was performed following injection of anticancer agents 3 days after the inoculation of the T24 cells. DNA samples were obtained from the livers of the chick embryos, and the polymerase chain reaction technique was used to amplify a DNA fragment specific to the human beta-globin gene. The Southern hybridization method was used to evaluate the inhibitory effects of anticancer agents in combination with/without hyperthermia on T24 cells metastasized to the liver. The hyperthermia exerted an inhibitory effect on the growth of the T24 cells in the livers of the chick embryos, and this was dependent on the thermal dose. The antitumor effects of hyperthermia performed at 42.5 degrees C for 20 min and at 43.0 degrees C for 10 min were evidenced by 69.2% an 82.0% inhibition of the growth of the metastasized T24 cells, respectively, as compared with the growth of untreated T24 cell. Hyperthermia performed at 42.5 degrees C for 10 min alone produced 26.7% tumor growth inhibition, and these conditions for hyperthermia were subsequently used as a criterion for evaluating the effects of its combination with various anticancer agents. Adriamycin (20 micrograms/egg) alone, mitomycin C (10 micrograms/egg) alone, carboplatin (10 micrograms/egg) alone, and cisplatin (10 micrograms/egg) alone produced 13.5%, 58.9%, 27.3%, and 29.1% tumor growth inhibition, respectively. Adriamycin and mitomycin C applied in combination with hyperthermia showed additive inhibitory effects on the growth of the metastasized T24 cells in this chick embryo model.

In vitro effects of mistletoe extracts and mistletoe lectins. Cytotoxicity towards tumor cells due to the induction of programmed cell death (apoptosis).

The in vitro effects of therapeutically administered mistletoe extracts (ABNOBAviscum) and pure mistletoe lectins (mainly mistletoe lectin I) on a variety of human and murine tumor cell lines have been investigated. Mistletoe extracts and purified mistletoe lectins inhibited in vitro the growth of all tumor cell lines tested including B cell hybridomas, P815, EL-4, Ke37, MOLT-4 and U937. The mechanism of growth arrest was shown to be due to the induction of programmed cell death (apoptosis). Thus, fragmentation of genomic DNA into oligonucleosomal bands of approximately 200 base pairs in length was observed within 20 h when tumor cells were incubated with mistletoe extracts or lectins. These data point to a rational basis for the direct cytotoxic effects of mistletoe extracts and lectins apart from the postulated immunostimulatory properties of these agents.