Mechanism of action of aragusterol a (YTA0040), a potent anti-tumor marine steroid targeting the G(1) phase of the cell cycle

Marine life as a source for breast cancer treatment: A comprehensive review

Breast cancer, one of the most significant tumors among all cancer cells, still has deficiencies for effective treatment. Moreover, substitute treatments employing natural products as bioactive metabolites has been seriously considered. The source of bioactive metabolites are not only the most numerous but also represent the richest source. A unique source is from the oceans or marine species which demonstrated intriguing chemical and biological diversity which represents an astonishing reserve for discovering novel anticancer drugs. Notably, marine sponges produce the largest amount of diverse bioactive peptides, alkaloids, terpenoids, polyketides along with many secondary metabolites whose potential is mostly therapeutic. In this review, our main focus is on the marine derived secondary metabolites which demonstrated cytotoxic effects towards numerous breast cancer cells and have been isolated from the marine sources such as marine sponges, cyanobacteria, fungi, algae, tunicates, actinomycetes, ascidians, and other sources of marine organisms.

Synthetic and Naturally Occurring Heterocyclic Anticancer Compounds with Multiple Biological Targets

Cancer is a complex group of diseases initiated by abnormal cell division with the potential of spreading to other parts of the body. The advancement in the discoveries of omics and bio- and cheminformatics has led to the identification of drugs inhibiting putative targets including vascular endothelial growth factor (VEGF) family receptors, fibroblast growth factors (FGF), platelet derived growth factors (PDGF), epidermal growth factor (EGF), thymidine phosphorylase (TP), and neuropeptide Y4 (NY4), amongst others. Drug resistance, systemic toxicity, and drug ineffectiveness for various cancer chemo-treatments are widespread. Due to this, efficient therapeutic agents targeting two or more of the putative targets in different cancer cells are proposed as cutting edge treatments. Heterocyclic compounds, both synthetic and natural products, have, however, contributed immensely to chemotherapeutics for treatments of various diseases, but little is known about such compounds and their multimodal anticancer properties. A compendium of heterocyclic synthetic and natural product multitarget anticancer compounds, their IC50, and biological targets of inhibition are therefore presented in this review.

Antitumor Profile of Carbon-Bridged Steroids (CBS) and Triterpenoids

This review focuses on the rare group of carbon-bridged steroids (CBS) and triterpenoids found in various natural sources such as green, yellow-green, and red algae, marine sponges, soft corals, ascidians, starfish, and other marine invertebrates. In addition, this group of rare lipids is found in amoebas, fungi, fungal endophytes, and plants. For convenience, the presented CBS and triterpenoids are divided into four groups, which include: (a) CBS and triterpenoids containing a cyclopropane group; (b) CBS and triterpenoids with cyclopropane ring in the side chain; (c) CBS and triterpenoids containing a cyclobutane group; (d) CBS and triterpenoids containing cyclopentane, cyclohexane or cycloheptane moieties. For the comparative characterization of the antitumor profile, we have added several semi- and synthetic CBS and triterpenoids, with various additional rings, to identify possible promising sources for pharmacologists and the pharmaceutical industry. About 300 CBS and triterpenoids are presented in this review, which demonstrate a wide range of biological activities, but the most pronounced antitumor profile. The review summarizes biological activities both determined experimentally and estimated using the well-known PASS software. According to the data obtained, two-thirds of CBS and triterpenoids show moderate activity levels with a confidence level of 70 to 90%; however, one third of these lipids demonstrate strong antitumor activity with a confidence level exceeding 90%. Several CBS and triterpenoids, from different lipid groups, demonstrate selective action on different types of tumor cells such as renal cancer, sarcoma, pancreatic cancer, prostate cancer, lymphocytic leukemia, myeloid leukemia, liver cancer, and genitourinary cancer with varying degrees of confidence. In addition, the review presents graphical images of the antitumor profile of both individual CBS and triterpenoids groups and individual compounds.

Sponges: A Reservoir of Genes Implicated in Human Cancer

Recently, it was shown that the majority of genes linked to human diseases, such as cancer genes, evolved in two major evolutionary transitions—the emergence of unicellular organisms and the transition to multicellularity. Therefore, it has been widely accepted that the majority of disease-related genes has already been present in species distantly related to humans. An original way of studying human diseases relies on analyzing genes and proteins that cause a certain disease using model organisms that belong to the evolutionary level at which these genes have emerged. This kind of approach is supported by the simplicity of the genome/proteome, body plan, and physiology of such model organisms. It has been established for quite some time that sponges are an ideal model system for such studies, having a vast variety of genes known to be engaged in sophisticated processes and signalling pathways associated with higher animals. Sponges are considered to be the simplest multicellular animals and have changed little during evolution. Therefore, they provide an insight into the metazoan ancestor genome/proteome features. This review compiles current knowledge of cancer-related genes/proteins in marine sponges.

Marine Sponge Natural Products with Anticancer Potential: An Updated Review

Despite the huge investment into research and the significant effort and advances made in the search for new anticancer drugs in recent decades, cancer cure and treatment continue to be a formidable challenge. Many sources, including plants, animals, and minerals, have been explored in the oncological field because of the possibility of identifying novel molecular therapeutics. Marine sponges are a prolific source of secondary metabolites, a number of which showed intriguing tumor chemopreventive and chemotherapeutic properties. Recently, Food and Drug Administration-approved drugs derived from marine sponges have been shown to reduce metastatic breast cancer, malignant lymphoma, and Hodgkin's disease. The chemopreventive and potential anticancer activity of marine sponge-derived compounds could be explained by multiple cellular and molecular mechanisms, including DNA protection, cell-cycle modulation, apoptosis, and anti-inflammatory activities as well as their ability to chemosensitize cancer cells to traditional antiblastic chemotherapy. The present article aims to depict the multiple mechanisms involved in the chemopreventive and therapeutic effects of marine sponges and critically explore the limitations and challenges associated with the development of marine sponge-based anticancer strategy.

Marine bioactives as functional food ingredients: potential to reduce the incidence of chronic diseases

The marine environment represents a relatively untapped source of functional ingredients that can be applied to various aspects of food processing, storage, and fortification. Moreover, numerous marine-based compounds have been identified as having diverse biological activities, with some reported to interfere with the pathogenesis of diseases. Bioactive peptides isolated from fish protein hydrolysates as well as algal fucans, galactans and alginates have been shown to possess anticoagulant, anticancer and hypocholesterolemic activities. Additionally, fish oils and marine bacteria are excellent sources of omega-3 fatty acids, while crustaceans and seaweeds contain powerful antioxidants such as carotenoids and phenolic compounds. On the basis of their bioactive properties, this review focuses on the potential use of marine-derived compounds as functional food ingredients for health maintenance and the prevention of chronic diseases.

Brassinosteroids cause cell cycle arrest and apoptosis of human breast cancer cells

Brassinosteroids (BRs) are plant hormones that appear to be ubiquitous in both lower and higher plants. Recently, we published the first evidence that some natural BRs induce cell growth inhibitory responses in several human cancer cell lines without affecting normal non-tumor cell growth (BJ fibroblasts). The aim of the study presented here was to examine the mechanism of the antiproliferative activity of the natural BRs 28-homocastasterone (28-homoCS) and 24-epibrassinolide (24-epiBL) in human hormone-sensitive and -insensitive (MCF-7 and MDA-MB-468, respectively) breast cancer cell lines. The effects of 6, 12 and 24h treatments with 28-homoCS and 24-epiBL on cancer cells were surveyed using flow cytometry, Western blotting, TUNEL assays and immunofluorescence analyses. The studied BRs inhibited cell growth and induced blocks in the G(1) cell cycle phase. ER-α immunoreactivity was uniformly present in the nuclei of control MCF-7 cells, while cytoplasmic speckles of ER-α immunofluorescence appeared in BR-treated cells (IC(50), 24h). ER-β was relocated to the nuclei following 28-homoCS treatment and found predominantly at the periphery of the nuclei in 24-epiBL-treated cells after 24h of treatment. These changes were also accompanied by down-regulation of the ERs following BR treatment. In addition, BR application to breast cancer cells resulted in G(1) phase arrest. Furthermore, TUNEL staining and double staining with propidium iodide and acridine orange demonstrated the BR-mediated induction of apoptosis in both cell lines, although changes in the expression of apoptosis-related proteins were modulated differently by the BRs in each cell line. The studied BRs seem to exert potent growth inhibitory effects via interactions with the cell cycle machinery, and they could be highly valuable leads for agents for managing breast cancer.

Steroids from an Australian sponge Psammoclema sp

Investigation of an extract of the Australian marine sponge Psammoclema sp. for dynamin I inhibitory activity led to the isolation of four new trihydroxysterols (1-4) related to aragusterol G. These compounds were largely identified by 1D and 2D NMR spectroscopic methods. While 1 was found to be inactive in the dynamin bioassay, bioassays did reveal that compounds 1-4 inhibited the growth of colorectal, breast, ovarian, and prostate cancer cell lines (GI(50) 5-27 microM). The additional insight that these new compounds give to previous SAR studies is discussed briefly.

Cytotoxic derivatives of (22R,23R)-dihydroxystigmastane

(22R,23R)-22,23-dihydroxystigmast-4-en-3-one, (22R,23R)-22,23-dihydroxystigmast-4-en-3,6-dione, (22R,23R)-3beta,5alpha,6beta,22,23-pentahydroxystigmastane, (22R,23R)-5alpha,6alpha-oxido-3beta,22,23-trihydroxystigmastane, (22R,23R)-5beta,6beta-oxido-3beta,22,23-trihydroxystigmastane, and (22R,23R)-3beta,6beta,22,23-tetrahydroxystigmast-4-ene were synthesized. Their cytotoxicities were comparatively studied using the MCF-7 line of carcinoma cells of human mammary gland and cells of human hepatoma of the Hep G2 line.

The natural compound n-butylidenephthalide derived from Angelica sinensis inhibits malignant brain tumor growth in vitro and in vivo

The naturally-occurring compound, n-butylidenephthalide (BP), which is isolated from the chloroform extract of Angelica sinensis (AS-C), has been investigated with respect to the treatment of angina. In this study, we have examined the anti-tumor effects of n-butylidenephthalide on glioblastoma multiforme (GBM) brain tumors both in vitro and in vivo. In vitro, GBM cells were treated with BP, and the effects of proliferation, cell cycle and apoptosis were determined. In vivo, DBTRG-05MG, the human GBM tumor, and RG2, the rat GBM tumor, were injected subcutaneously or intracerebrally with BP. The effects on tumor growth were determined by tumor volumes, magnetic resonance imaging and survival rate. Here, we report on the potency of BP in suppressing growth of malignant brain tumor cells without simultaneous fibroblast cytotocixity. BP up-regulated the expression of Cyclin Kinase Inhibitor (CKI), including p21 and p27, to decrease phosphorylation of Rb proteins, and down-regulated the cell-cycle regulators, resulting in cell arrest at the G(0)/G(1) phase for DBTRG-05MG and RG2 cells, respectively. The apoptosis-associated proteins were dramatically increased and activated by BP in DBTRG-05MG cells and RG2 cells, but RG2 cells did not express p53 protein. In vitro results showed that BP triggered both p53-dependent and independent pathways for apoptosis. In vivo, BP not only suppressed growth of subcutaneous rat and human brain tumors but also, reduced the volume of GBM tumors in situ, significantly prolonging survival rate. These in vitro and in vivo anti-cancer effects indicate that BP could serve as a new anti-brain tumor drug.

The Antitumor Effects of Angelica sinensis on Malignant Brain Tumors In vitro and In vivo

PURPOSE

In this study, we have examined the antitumor effects of chloroform extract of Angelica sinensis (AS-C), a traditional Chinese medicine, on glioblastoma multiforme (GBM) brain tumors in vitro and in vivo.

EXPERIMENTAL DESIGN

In vitro, GBM cells were treated with AS-C, and the cell proliferation, changes in distributions of cell cycle, and apoptosis were determined. In vivo, human DBTRG-05MG and rat RG2 GBM tumor cells were injected s.c. or i.c. and were treated with AS-C. Effects on tumor growth were determined by tumor volume, magnetic resonance imaging, survival, and histology analysis.

RESULTS

The AS-C displays potency in suppressing growth of malignant brain tumor cells without cytotoxicity to fibroblasts. Growth suppression of malignant brain tumor cells by AS-C results from cell cycle arrest and apoptosis. AS-C can up-regulate expression of cdk inhibitors, including p21, to decrease phosphorylation of Rb proteins resulting in cell arrest at the G0-G1 phase for DBTRG-05MG and RG2 cells. The apoptosis-associated proteins are dramatically increased and activated in DBTRG-05MG cells and RG2 cells by AS-C but RG2 cells without p53 protein expression. In vitro results showed AS-C triggered both p53-dependent and p53-independent pathways for apoptosis. In in vivo studies, AS-C not only can suppress growths of malignant brain tumors of rat and human origin but also shrink the volumes of in situ GBM, significantly prolonging survivals.

CONCLUSIONS

The in vitro and in vivo anticancer effects of AS-C indicate that it has sufficient potential to warrant further investigation and development as a new anti-brain tumor agent.

Marine sponges as pharmacy

Marine sponges have been considered as a gold mine during the past 50 years, with respect to the diversity of their secondary metabolites. The biological effects of new metabolites from sponges have been reported in hundreds of scientific papers, and they are reviewed here. Sponges have the potential to provide future drugs against important diseases, such as cancer, a range of viral diseases, malaria, and inflammations. Although the molecular mode of action of most metabolites is still unclear, for a substantial number of compounds the mechanisms by which they interfere with the pathogenesis of a wide range of diseases have been reported. This knowledge is one of the key factors necessary to transform bioactive compounds into medicines. Sponges produce a plethora of chemical compounds with widely varying carbon skeletons, which have been found to interfere with pathogenesis at many different points. The fact that a particular disease can be fought at different points increases the chance of developing selective drugs for specific targets.

New polyhydroxylated sterols stylisterols A-C and a novel 5,19-cyclosterol hatomasterol from the Okinawan marine sponge Stylissa sp

New polyhydroxylated sterols, stylisterol A-C (1-3), and a novel 5,19-cyclosterol, hatomasterol (4) were isolated from the Okinawan sponge Stylissa sp. Structural determinations of these compounds were made by spectroscopic analysis and chemical conversion. Assessment of cytotoxicity toward HeLa cells was also determined.

Mechanism targeted discovery of antitumor marine natural products

Antitumor drug discovery programs aim to identify chemical entities for use in the treatment of cancer. Many strategies have been used to achieve this objective. Natural products have always played a major role in anticancer medicine and the unique metabolites produced by marine organisms have increasingly become major players in antitumor drug discovery. Rapid advances have occurred in the understanding of tumor biology and molecular medicine. New insights into mechanisms responsible for neoplastic disease are significantly changing the general philosophical approach towards cancer treatment. Recently identified molecular targets have created exciting new means for disrupting tumor-specific cell signaling, cell division, energy metabolism, gene expression, drug resistance and blood supply. Such tumor-specific treatments could someday decrease our reliance on traditional cytotoxicity-based chemotherapy and provide new less toxic treatment options with significantly fewer side effects. Novel molecular targets and state-of-the-art, molecular mechanism-based screening methods have revitalized antitumor research and these changes are becoming an ever-increasing component of modern antitumor marine natural products research. This review describes marine natural products identified using tumor-specific mechanism-based assays for regulators of angiogenesis, apoptosis, cell cycle, macromolecule synthesis, mitochondrial respiration, mitosis, multidrug efflux and signal transduction. Special emphasis is placed on natural products directly discovered using molecular mechanism-based screening.

Challenges and rewards of research in marine natural products chemistry in Brazil

Brazil is blessed with a great biodiversity, which constitutes one of the most important sources of biologically active compounds, even if it has been largely underexplored. As is the case of the Amazon and Atlantic rainforests, the Brazilian marine fauna remains practically unexplored in the search for new biologically active natural products. Considering that marine organisms have been shown to be one of the most promising sources of new bioactive compounds for the treatment of different human diseases, the 8000 km of the Brazilian coastline represents a great potential for finding new pharmacologically active secondary metabolites. This review presents the status of marine natural products chemistry in Brazil, including results reported by different research groups with emphasis on the isolation, structure elucidation, and evaluation of biological activities of natural products isolated from sponges, ascidians, octocorals, and Opistobranch mollusks. A brief overview of the first Brazilian program on the isolation of marine bacteria and fungi, directed toward the production of biologically active compounds, is also discussed. The current multidisciplinary collaborative program under development at the Universidade de São Paulo proposes to establish a new paradigm toward the management of the Brazilian marine biodiversity, integrating research on the species diversity, ecology, taxonomy, and biogeography of marine invertebrates and microorganisms. This program also includes a broad screening program of Brazilian marine bioresources, to search for active compounds that may be of interest for the development of new drug leads.

Marine pharmacology in 2000: antitumor and cytotoxic compounds

During 2000, marine antitumor pharmacology research aimed at the discovery of novel antitumor agents was published in 85 peer-reviewed articles. The purpose of this article is to present a structured review of the antitumor and cytotoxic properties of 143 marine natural products, many of them novel compounds that belong to diverse structural classes, including polyketides, terpenes, steroids and peptides. The organisms yielding these bioactive compounds comprised a taxonomically diverse group of marine invertebrate animals, algae, fungi and bacteria. Antitumor pharmacological studies were conducted with 19 marine natural products in a number of experimental and clinical models that defined or further characterized their mechanisms of action. Potentially promising in vitro cytotoxicity data generated with murine and human tumor cell lines were reported for 124 novel marine chemicals with as yet undetermined mechanisms of action. Noteworthy is the fact that marine anticancer research clearly remains a multinational effort, involving researchers from Austria, Australia, Brazil, Canada, England, France, Germany, Greece, Indonesia, Italy, Japan, New Zealand, Russia, Spain, South Korea, Switzerland, Taiwan, the Netherlands and the United States. Finally, this 2000 overview of the marine pharmacology literature highlights the fact that the discovery of novel marine antitumor agents continued at the same high level of research activity as during 1998 and 1999.

Synthesis and anti-tumor activity of new steroidal nuclear analogues of aragusterol A

3alpha,7alpha-Dihydroxy-5-epiaragusterol A (3) was synthesized from bile acid (cholic acid) as a new steroidal nuclear analogue of antitumor marine steroid aragusterol A. 7alpha-Hydroxyaragusterol A (4) was also derived from xestokerol B. The in vitro anti-proliferative activity of each of these analogues toward KB cells as well as in vivo anti-tumor activity of 5-epiaragusterol A (2) previously synthesized by the authors and 3 were assessed.

Capsaicin inhibits growth of adult T-cell leukemia cells

Human T-cell leukemia virus type 1 (HTLV-1)-associated adult T-cell leukemia (ATL) is resistant to conventional chemotherapy. We examined the in vitro effects of capsaicin, the principal ingredients of red pepper, on three ATL cell lines. Capsaicin treatment inhibited the growth of ATL cells both in dose- and time-dependent manner. The inhibitory effect was mainly due to the induction of cell cycle arrest and apoptosis. Capsaicin treatment also induced the degradation of Tax and up-regulation of I kappa-B alpha, resulting in the decrease of nuclear factor (NF)-kappa B/p65 DNA binding activity. In addition, the Bcl-2 level was found to be decreased. Based on these findings, capsaicin may be considered for chemoprevention of ATL.

[Studies on discovery and synthesis of bioactive marine organic molecules]

This paper describes the discovery and total synthesis of bioactive marine natural products conducted in our laboratory. Clavulone, chlorovulone, bromovulone, and iodovulone are antitumor marine prostanoids isolated from the Okinawan soft coral Clavularia viridis. The synthesis of clavulone and chlorovulone was achieved from chiral 4-hydroxy-2-cyclopentenone. Marine prostanoid punaglandins 3 and 4 were synthesized via similar methodology. The chemical structures of punaglandins 3 and 4 were revised by these syntheses. Dollaberane-type diterpenoid stolonidiol and claenone were isolated from Okinawan soft coral Clavularia sp. Stolonidiol showed potent choline acetyltransferase-inducible activity in cultured basal forebrain cells. The synthesis of stolondiol and claenone was conducted via sequential Michael reaction and retro-aldol reaction. Aragusterols, isolated from the Okinawan marine sponge Xestospongia sp., are structurally unique steroids possessing a rare 26,27-cyclo structure in the side chain. Aragusterols express potent in vivo antitumor activity against L1210 leukemia in mice. The synthesis of aragusterols was carried out via steroselective construction of the side chain and stereocontrolled coupling reaction with the steroid skeleton. Kalihinane-type diterpenoid kalihinol A, isolated by Scheuer, has remarkable in vitro antimalarial activity. The absolute configuration of kalihinol A was determined by applying the CD exciton chiral method. Synthesis of kalihinene X, a kalihinane-type diterpenoid, was achieved. This synthesis involves the regioselective coupling reaction of carbanion of alkyl sulfone with epoxyalcohol and construction of cis-decalin by an intramolecular Diels-Alder reaction.