Alexander Kornienko

Chemistry, biology, and medicinal potential of narciclasine and its congeners.

Ornamental flower growers know that placing a cut daffodil (a.k.a. narcissus) in a vase with other flowers has a negative effect on the quality of those flowers and significantly shortens their vase life. Furthermore, a common horticultural practice for the cultivation of narcissus flowers involves the introduction of cuts on the bulbs before immersing them into water. The mucilage that leaches out from the cuts is constantly removed by frequent changing of water and this leads to sprouting. These observations raise speculation that specific components in the mucilage of the narcissus bulbs may have powerful growth-inhibitory effects. Historical use of narcissus flowers, as well as at least thirty other plants of the Amaryllidaceae family, in folk medicine for the management of cancer1 speaks volumes to validate this conjecture. Indeed, powerful anticancer properties of Narcissus poeticus L. were already known to the Father of Medicine, Hippokrates of Kos (ca. B.C. 460–370), who recommended a pessary prepared from narcissus oil for the treatment of uterine tumors.2 His successors, the ancient Greek physicians Pedanius Dioscorides (ca. A.D. 40–90) and Soranus of Ephesus (A.D. 98–138) continued using this therapy in the first and second centuries A.D.3,4 In addition, the topical anticancer uses of extracts from this plant5,6 as well as from N. pseudonarcissus7–9 were recorded in the first century A.D. by the Roman natural philosopher Gaius Plinius Secundus, (A.D. 23–79), better known as Pliny the Elder.10 Even the Bible provides multiple references to the Mediterranean N. tazetta L., which has a long history of use against cancer.11 The applications of narcissus oil in cancer management continued in the middle ages in Chinese, North African, Central American and Arabian medicine.1,12 The uses of other genera of the Amaryllidaceae family were also common, e. g. Hymenocallis caribaea (L. emend Gawler) Herbert, utilized by early European medical practitioners for inflammatory tumors.13 More recently, the plants of the Amaryllidaceae have been under intense scrutiny for the presence of the specific metabolites responsible for the medicinal properties associated with this plant family. The study began in 1877 with the isolation of alkaloid lycorine from Narcissus pseudonarcissus14 and since then more than 100 alkaloids, exhibiting diverse biological activities, have been isolated from the Amaryllidaceae plants. Based on the present scientific evidence, it is likely that isocarbostyril constituents of the Amaryllidaceae, such as narciclasine, pancratistatin and their congeners, are the most important metabolites responsible for the therapeutic benefits of these plants in the folk medical treatment of cancer. Notably, N. poeticus L. used by the ancient Greek physicians, as was eluded before, is now known to contain some 0.12 g of narciclasine per kg of fresh bulbs.15 Continuing along this intriguing path, the focus of the present review is a comprehensive literature survey and discussion of the chemistry and biology of these compounds as specifically relevant to their potential use in medicine. The examination of the synthetic organic chemistry, more specifically the total synthesis efforts inspired by the challenging chemical structures of narciclasine, pancratistatin and their congeners, will be reduced to a minimum in view of the two very recent excellent reviews published on this subject.16,17

Lycorine, the main phenanthridine Amaryllidaceae alkaloid, exhibits significant antitumor activity in cancer cells that display resistance to proapoptotic stimuli: an investigation of structure-activity relationship and mechanistic insight.

Twenty-two lycorine-related compounds were investigated for in vitro antitumor activity using four cancer cell lines displaying different levels of resistance to proapoptotic stimuli and two cancer cell lines sensitive to proapoptotic stimuli. Lycorine and six of its congeners exhibited potency in the single-digit micromolar range, while no compound appeared more active than lycorine. Lycorine also displayed the highest potential (in vitro) therapeutic ratio, being at least 15 times more active against cancer than normal cells. Our studies also showed that lycorine exerts its in vitro antitumor activity through cytostatic rather than cytotoxic effects. Furthermore, lycorine provided significant therapeutic benefit in mice bearing brain grafts of the B16F10 melanoma model at nontoxic doses. Thus, the results of the current study make lycorine an excellent lead for the generation of compounds able to combat cancers, which are naturally resistant to proapoptotic stimuli, such as glioblastoma, melanoma, non-small-cell-lung cancers, and metastatic cancers, among others.

Structural simplification of bioactive natural products with multicomponent synthesis. 2. Antiproliferative and antitubulin activities of pyrano[3,2-c]pyridones and pyrano[3,2-c]quinolones

Pyrano[3,2- c]pyridone and pyrano[3,2- c]quinolone structural motifs are commonly found in alkaloids manifesting diverse biological activities. As part of a program aimed at structural simplification of bioactive natural products utilizing multicomponent synthetic processes, we developed compound libraries based on these privileged heterocyclic scaffolds. The selected library members display low nanomolar antiproliferative activity and induce apoptosis in human cancer cell lines. Mechanistic studies reveal that these compounds induce cell cycle arrest in the G2/M phase and block in vitro tubulin polymerization. Because of the successful clinical use of microtubule-targeting agents, these heterocyclic libraries are expected to provide promising new leads in anticancer drug design.

Amaryllidaceae alkaloids belonging to different structural subgroups display activity against apoptosis-resistant cancer cells.

Fifteen Amaryllidaceae alkaloids (1-15) were evaluated for their antiproliferative activities against six distinct cancer cell lines. Several of these natural products were found to have low micromolar antiproliferative potencies. The log P values of these compounds did not influence their observed activity. When active, the compounds displayed cytostatic, not cytotoxic activity, with the exception of pseudolycorine (3), which exhibited cytotoxic profiles. The active compounds showed similar efficacies toward cancer cells irrespective of whether the cell lines were responsive or resistant to proapoptotic stimuli. Altogether, the data from the present study revealed that lycorine (1), amarbellisine (6), haemanthamine (14), and haemanthidine (15) are potentially useful chemical scaffolds to generate further compounds to combat cancers associated with poor prognoses, especially those naturally resistant to apoptosis, such as glioblastoma, melanoma, non-small-cell lung, and metastatic cancers.

Three-component synthesis and anticancer evaluation of polycyclic indenopyridines lead to the discovery of a novel indenoheterocycle with potent apoptosis inducing properties

A multicomponent reaction of indane-1,3-dione, an aldehyde and an amine-containing aromatic compound leading to the formation of indenopyridine-based heterocyclic medicinal scaffolds has been investigated. It was found that the yields significantly improve when oxygen gas is bubbled through the reaction mixture, facilitating the oxidation of the intermediate dihydropyridine-containing compounds to their aromatic counterparts. Investigation of the reaction scope revealed that formaldehyde, as well as various aliphatic, aromatic and heteroaromatic aldehydes, works well as the aldehyde component. In addition, substituted anilines and diverse aminoheterocycles can be utilized in this process as the amine-containing component. Preliminary biological evaluation of the synthesized library identified a pyrimidine-based polycycle, which rivals the anticancer drug etoposide in its toxicity and apoptosis inducing properties toward a human T-cell leukemia cell line.

Targeting of eEF1A with Amaryllidaceae isocarbostyrils as a strategy to combat melanomas

Melanomas display poor response rates to adjuvant therapies because of their intrinsic resistance to proapoptotic stimuli. This study indicates that such resistance can be overcome, at least partly, through the targeting of eEF1A elongation factor with narciclasine, an Amaryllidaceae isocarbostyril controlling plant growth. Narciclasine displays IC50 growth inhibitory values between 30–100 nM in melanoma cell lines, irrespective of their levels of resistance to proapoptotic stimuli. Normal noncancerous cell lines are much less affected. At nontoxic doses, narciclasine also significantly improves (P=0.004) the survival of mice bearing metastatic apoptosis‐resistant melanoma xenografts in their brain. The eEF1A targeting with narciclasine (50 nM) leads to 1) marked actin cytoskeleton disorganization, resulting in cytokinesis impairment, and 2) protein synthesis impairment (elongation and initiation steps), whereas apoptosis is induced at higher doses only (≥200 nM). In addition to molecular docking validation and identification of potential binding sites, we biochemically confirmed that narciclasine directly binds to human recombinant and yeast‐purified eEF1A in a nanomolar range, but not to actin or elongation factor 2, and that 5 nM narciclasine is sufficient to impair eEF1A‐related actin bundling activity. eEF1A is thus a potential target to combat melanomas regardless of their apoptosis‐sensitivity, and this finding reconciles the pleiotropic cytostatic of narciclasine.—Van Goietsenoven, G., Hutton, J., Becker, J.‐P., Lallemand, B., Robert, F., Lefranc, F., Pirker, C., Vandenbussche, G., Van Antwerpen, P., Evidente, A., Berger, W., Prevost, M., Pelletier, J., Kiss, R., Goss Kinzy, T., Kornienko, A., Mathieu, V. Targeting of eEF1A with Amaryllidaceae isocarbostyrils as a strategy to combat melanomas. FASEB J. 24, 4575–4584 (2010). www.fasebj.org

Biological Evaluation of Structurally Diverse Amaryllidaceae Alkaloids and their Synthetic Derivatives: Discovery of Novel Leads for Anticancer Drug Design

Twenty-nine Amaryllidaceae alkaloids and their derivatives belonging to the five most common groups, including lycorine, lycorenine, tazettine, crinine, and narciclasine types, were evaluated for antiproliferative, apoptosis-inducing, and anti-invasive activities in vitro. The antiproliferative properties of each test compound are in agreement with those reported in the literature, while the high potency of amarbellisine is reported for the first time. It was also found that with the exception of ungeremine, amarbellisine, and hippeastrine, the antiproliferative effect of the potent compounds is apoptosis mediated. Thus, apoptosis in Jurkat cells was triggered by narciclasine, narciclasine tetraacetate, C10b-R-hydroxypancratistatin, cis-dihydronarciclasine, trans-dihydronarciclasine, lycorine, 1-O-acetyllycorine, lycorine-2-one, pseudolycorine, and haemanthamine. With the exception of narciclasine, lycorine, and haemanthamine, the apoptosis-inducing properties of these compounds are reported for the first time. The collagen type I invasion assay revealed potent anti-invasive properties associated with N-methyllycorine iodide, hippeastrine, clivimine, buphanamine, and narciclasine tetraacetate, all of which were tested at non-toxic concentrations. The anti-invasive activity of buphanamine is particularly promising because this alkaloid is not toxic to cells even at much higher doses. This work has resulted in the identification of several novel leads for anticancer drug design.

Lycorine and its derivatives for anticancer drug design.

Amaryllidaceae alkaloids are extensively studied for their biological activities in several pharmaceutical areas, including, for example, Alzheimers disease for which galanthamine has already reached the market. Among this chemical family, lycorine displays very promising anti-tumor properties. This review first focuses on the chemical diversity of natural and synthetic analogues of lycorine and their metabolites, and then on mechanisms of action and biological targets through which lycorine and its derivatives display their anti-tumor activity. Our analysis of the structure-activity relationships of this family of compounds highlights the existence of various potential leads for the development of novel anticancer agents.

Ophiobolin A induces paraptosis-like cell death in human glioblastoma cells by decreasing BKCa channel activity

Glioblastoma multiforme (GBM) is the most lethal and common malignant human brain tumor. The intrinsic resistance of highly invasive GBM cells to radiation- and chemotherapy-induced apoptosis accounts for the generally dismal treatment outcomes. This study investigated ophiobolin A (OP-A), a fungal metabolite from Bipolaris species, for its promising anticancer activity against human GBM cells exhibiting varying degrees of resistance to proapoptotic stimuli. We found that OP-A induced marked changes in the dynamic organization of the F-actin cytoskeleton, and inhibited the proliferation and migration of GBM cells, likely by inhibiting big conductance Ca2+-activated K+ channel (BKCa) channel activity. Moreover, our results indicated that OP-A induced paraptosis-like cell death in GBM cells, which correlated with the vacuolization, possibly brought about by the swelling and fusion of mitochondria and/or the endoplasmic reticulum (ER). In addition, the OP-A-induced cell death did not involve the activation of caspases. We also showed that the expression of BKCa channels colocalized with these two organelles (mitochondria and ER) was affected in this programmed cell death pathway. Thus, this study reveals a novel mechanism of action associated with the anticancer effects of OP-A, which involves the induction of paraptosis through the disruption of internal potassium ion homeostasis. Our findings offer a promising therapeutic strategy to overcome the intrinsic resistance of GBM cells to proapoptotic stimuli.

Fungal metabolites with anticancer activity

Covering: 1964 to 2013. Natural products from bacteria and plants have played a leading role in cancer drug discovery resulting in a large number of clinically useful agents. In contrast, the investigations of fungal metabolites and their derivatives have not led to a clinical cancer drug in spite of significant research efforts revealing a large number of fungi-derived natural products with promising anticancer activity. Many of these natural products have displayed notable in vitro growth-inhibitory properties in human cancer cell lines and select compounds have been demonstrated to provide therapeutic benefits in mouse models of human cancer. Many of these compounds are expected to enter human clinical trials in the near future. The present review discusses the reported sources, structures and biochemical studies aimed at the elucidation of the anticancer potential of these promising fungal metabolites.