Antitumor activity of cucumarioside A2-2

Anticancer Activity of the Marine Triterpene Glycoside Cucumarioside A2-2 in Human Prostate Cancer Cells

Despite recent advances in the treatment of metastatic castration-resistant prostate cancer (CRPC), treatment is inevitably hampered by the development of drug resistance. Thus, new drugs are urgently needed. We investigated the efficacy, toxicity, and mechanism of action of the marine triterpene glycoside cucumarioside A2-2 (CA2-2) using an in vitro CRPC model. CA2-2 induced a G2/M-phase cell cycle arrest in human prostate cancer PC-3 cells and caspase-dependent apoptosis executed via an intrinsic pathway. Additionally, the drug inhibited the formation and growth of CRPC cell colonies at low micromolar concentrations. A global proteome analysis performed using the 2D-PAGE technique, followed by MALDI-MS and bioinformatical evaluation, revealed alterations in the proteins involved in cellular processes such as metastatic potential, invasion, and apoptosis. Among others, the regulation of keratin 81, CrkII, IL-1β, and cathepsin B could be identified by our proteomics approach. The effects were validated on the protein level by a 2D Western blotting analysis. Our results demonstrate the promising anticancer activity of CA2-2 in a prostate cancer model and provide insights on the underlying mode of action.

Saponins of North Atlantic Sea Cucumber: Chemistry, Health Benefits, and Future Prospectives

Frondosides are the major saponins (triterpene glycosides) of the North Atlantic sea cucumber (Cucumaria frondosa). Frondosides possess amphiphilic characteristics due to the presence of various hydrophilic sugar moieties and hydrophobic genin (sapogenin). Saponins are abundant in holothurians, including in sea cucumbers that are widely distributed across the northern part of the Atlantic Ocean. Over 300 triterpene glycosides have been isolated, identified, and categorized from many species of sea cucumbers. Furthermore, specific saponins from sea cucumbers are broadly classified on the basis of the fron-dosides that have been widely studied. Recent studies have shown that frondoside-containing extracts from C. frondosa exhibit anticancer, anti-obesity, anti-hyperuricemic, anticoagulant, antioxidant, antimicrobial, antiangiogenic, antithrombotic, anti-inflammatory, antitumor, and immunomodulatory activities. However, the exact mechanism(s) of action of biological activities of frondosides is not clearly understood. The function of some frondosides as chemical defense molecules need to be understood. Therefore, this review discusses the different frondosides of C. frondosa and their potential therapeutic activities in relation to the postulated mechanism(s) of action. In addition, recent advances in emerging extraction techniques of frondosides and other saponins and future perspectives are discussed.

Antioxidant and Anticancer Activities of Sand Sea Cucumber (Holothuria scabra) Extracts using Wet Rendering Extraction Method

Antioxidant and anticancer activities of sand sea cucumber Holothuria scabra (dried and fresh) extracts were studied. The highest extraction yield of sea cucumber H. scabra (3.9%) was obtained using dried H. scabra at 60oC. The highest antioxidant activity was found in fresh H. scabra extract at 60°C with an IC50 value of 629.89 ± 0.15 µg/mL using the ABTS method, and the highest antioxidant activity by DPPH method was found in dried H. scabra extract at 70°C with an IC50 value of 32017.18 ± 0.82 µg/mL. The best antioxidant activity based on FRAP and TBARS methods was found in fresh H. scabra extracts at 80°C, respectively. The highest total phenol and flavonoid contained in dried H. scabra extract were 317.54 ± 8.91 mg GAE/100 g sample and 247.56 ± 11.70 mg QE/100 g sample. H. scabra extracts inhibited more than 50% of the growth of the MDA-MB-231 cell line at concentrations of 25 and 50 μg/mL except for dried H. scabra extracts at 80°C. Similarly, the extracts showed the highest cytotoxic effect up to 100% at the highest concentration (100 μg/mL) except for dried H. scabra extracts at 70°C and 80°C.

The influence of antioxidant dietary-derived polyphenolic combination on breast cancer: Molecular study

Breast cancer remains a leading cause of female mortality worldwide. Therefore, novel complementary treatments have been sought. Recently, there has been a growing interest in investigating the possible complementary effects of polyphenolic compounds against various malignancies. In the present study, using MCF-7 and MDA-MB-231 human breast adenocarcinoma cells, the anticancer efficacy of a polyphenolic mixture (PFM) was investigated. PFM is composed of curcumin, resveratrol, epigallocatechin gallate, and quercetin. PFM treatment led to a dose-dependent inhibition of cell proliferation, with IC₅₀ values of 25.9 ± 3 µg/ml and 29.4 ± 0.9 µg/ml for MCF-7 and MDA-MB-231 cells, respectively. In addition, PFM induced apoptosis in MDA-MB-231 cells and cell cycle arrest at the S phase in MCF-7 cells. Using RT-qPCR, PFM treatment was observed to result in significant downregulation of the oncogenic miR-155 (P < 0.05), as well as significant downregulation of the rate-limiting glycolytic enzyme, hexokinase 2 (HK2) (P < 0.05), while upregulating the expression of the zinc finger E-box binding homeobox 2 gene (P < 0.01). PFM was also found to exert an anti-migration effect in breast cancer cells using the wound healing assay, as well as significantly (P < 0.05) increasing the median survival of Ehrlich ascites carcinoma (EAC) tumor-bearing mice. These results suggest that PFM possesses potential antitumor effects against breast cancer. A possible mechanism of action could be due to PFM's effect in modulating the expression of the glycolytic enzyme HK2 through suppression of miR-155 in MCF-7 cells. Combining polyphenolic compounds that interact with one another could result in synergistic effects that potentially target various tumour hallmarks.

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.

Comprehensive review on signaling pathways of dietary saponins in cancer cells suppression

Nutrigenomics utilizes high-throughput genomic technologies to reveal changes in gene and protein levels. Excitingly, ever-growing body of scientific findings has provided sufficient evidence about the interplay between diet and genes. Cutting-edge research and advancements in genomics, epigenetics and metabolomics have deepened our understanding on the role of dietary factors in the inhibition of carcinogenesis and metastasis. Dietary saponins, a type of triterpene glycosides, are generally found in Platycodon grandifloras, Dioscorea oppositifolia, asparagus, legumes, and sea cucumber. Wealth of information has started to shed light on pleiotropic mechanistic roles of dietary saponins in cancer prevention and inhibition. In this review, we have attempted to summarize the in vitro research of dietary saponins in the last two decades by searching common databases such as Google Scholar, PubMed, Scopus, and Web of Science. The results showed that dietary saponins exerted anti-cancer activities via regulation of apoptosis, autophagy, arrest cell cycle, anti-proliferation, anti-metastasis, and anti-angiogenesis, by regulation of several critical signaling pathways, including MAPK, PI3K/Akt/mTOR, NF-κB, and VEGF/VEGFR. However, there is no data about the dosage of dietary saponins for practical anti-cancer effects in human bodies. Extensive clinical studies are needed to confirm the effectiveness of dietary saponins for further commercial and medical applications.

Pharmacokinetics of Marine-Derived Drugs

Marine organisms represent an excellent source of innovative compounds that have the potential for the development of new drugs. The pharmacokinetics of marine drugs has attracted increasing interest in recent decades due to its effective and potential contribution to the selection of rational dosage recommendations and the optimal use of the therapeutic arsenal. In general, pharmacokinetics studies how drugs change after administration via the processes of absorption, distribution, metabolism, and excretion (ADME). This review provides a summary of the pharmacokinetics studies of marine-derived active compounds, with a particular focus on their ADME. The pharmacokinetics of compounds derived from algae, crustaceans, sea cucumber, fungus, sea urchins, sponges, mollusks, tunicate, and bryozoan is discussed, and the pharmacokinetics data in human experiments are analyzed. In-depth characterization using pharmacokinetics is useful for obtaining information for understanding the molecular basis of pharmacological activity, for correct doses and treatment schemes selection, and for more effective drug application. Thus, an increase in pharmacokinetic research on marine-derived compounds is expected in the near future.

An Unusual Pathway of Mitoptosis Found in Ehrlich Carcinoma Cells

An integrated microscopic study of the destruction of mouse Ehrlich ascites carcinoma (EAC) cells under starvation conditions has been carried out. It has been found that, in addition to apoptosis, necrosis, and apoptotic necrosis, already known for EAC, cell destruction can also occur through mitochondrial autolysis, which is proposed to be considered a new kind of mitoptosis. A mitoptosis in EAC is characterized by the appearance of many autolyzing mitochondria, the fusion of which leads to rupture of the cell membrane and the ejection of the nucleus from the cell. It is assumed that the polymorphism of EAC destruction patterns is explained by the different physiological state of the cells, which determines the "choice" of the cell death mechanism. This situation poses a challenge for researchers to develop complex inducers with the ability to stimulate all possible types of cancer cell death.

Synthesis and Evaluation of Antimicrobial and Cytotoxic Activity of Oxathiine-Fused Quinone-Thioglucoside Conjugates of Substituted 1,4-Naphthoquinones

A series of new tetracyclic oxathiine-fused quinone-thioglycoside conjugates based on biologically active 1,4-naphthoquinones and 1-mercapto derivatives of per-O-acetyl d-glucose, d-galactose, d-xylose, and l-arabinose have been synthesized, characterized, and evaluated for their cytotoxic and antimicrobial activities. Six tetracyclic conjugates bearing a hydroxyl group in naphthoquinone core showed high cytotoxic activity with EC50 values in the range of 0.3 to 0.9 μM for various types of cancer and normal cells and no hemolytic activity up to 25 μM. The antimicrobial activity of conjugates was screened against Gram-positive bacteria (Staphylococcus aureus, Bacillus cereus), Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli), and fungus Candida albicans by the agar diffusion method. The most effective juglone conjugates with d-xylose or l-arabinose moiety and hydroxyl group at C-7 position of naphthoquinone core at concentration 10 µg/well showed antimicrobial activity comparable with antibiotics vancomicin and gentamicin against Gram-positive bacteria strains. In liquid media, juglone-arabinosidic tetracycles showed highest activity with MIC 6.25 µM. Thus, a positive effect of heterocyclization with mercaptosugars on cytotoxic and antimicrobial activity for group of 1,4-naphthoquinones was shown.

Modulation of Doxorubicin Intracellular Accumulation and Anticancer Activity by Triterpene Glycoside Cucumarioside A2-2

The effect of treatment of Ehrlich ascites carcinoma (EAC) cells with multidrug resistance by holothurian triterpene glycoside, cucumarioside A₂-2 (CA₂-2) was evaluated. Calcein-AM efflux assay and doxorubicin (DOX) uptake and retention measurement in cancer cells, as well as determination of DOX cytotoxic and anticancer effects were applied. Treatment of EAC cells with CA₂-2 (0.01–0.1 μM) blocked Calcein-AM and DOX efflux from cancer cells and increased the accumulation and cytotoxicity of DOX in EAC cells. Moreover, pre-treatment of mice with EAC by CA₂-2 (10 μg/kg/5 days, intraperitoneal injection (i.p.)), then transplantation of tumor cells into fresh animals and subsequent treatment of these mice with DOX (2 mg/kg/3 days i.p.) significantly increased average life span (ALS) of mice bearing a tumor and therefore boosted the antitumor effect of doxorubicin in vivo.

Sea cucumber extract TBL-12 inhibits the proliferation, migration, and invasion of human prostate cancer cells through the p38 mitogen-activated protein kinase and intrinsic caspase apoptosis pathway

BACKGROUND

Sea cucumber is a kind of nutritious echinoderm that has multiple biological activities, including antioxidant, antibacterial, and antitumor activities. However, there is no extensive study on the antitumor effect of sea cucumber extract on prostate cancer (PCa). TBL-12 is a new sea cucumber extract. In this study, we investigated the in vivo anti-PCa effect of TBL-12 and its in vitro effects on the proliferation, apoptosis, migration, and invasion of the human PCa cell lines LNCaP, 22RV1, PC-3, and DU145, and evaluated its possible mechanisms.

METHODS

Cell proliferation was analyzed by cell counting kit-8 and colony formation assays. Scratch migration assay and transwell invasiveness assay were used to observe TBL-12 effect on the migration and invasion of PCa cells. Matrix metalloproteinase 2 (MMP-2) and MMP-9 expression and enzymatic activity was determined by Western blot analysis, quantitative reverse-transcription polymerase chain reaction, and gelatin zymography. Apoptosis level was detected by flow cytometry analysis. Western blot analysis was used to analyze p38 mitogen-activated protein kinase (MAPK) and apoptosis pathways. Angiogenic array analysis was used to explore autocrine and paracrine growth factors in PCa cell lines. Xenograft tumor model was built to observe the in vivo anticancer effect.

RESULTS

TBL-12 could significantly inhibit tumor growth in xenograft PCa mice in vivo, and dramatically inhibit the proliferation, colony formation, migration, and invasiveness of PCa cells in vitro (P < 0.05 and P < 0.001). The expression and enzyme activity of MMP-2 and MMP-9 were significantly suppressed by TBL-12 ( P < 0.01), and decreased phosphorylation level of p38 in PCa cells was detected ( P < 0.001). Furthermore, TBL-12 could reinforce the MMP-2/MMP-9 inhibitory effect of SB203580, a specific inhibitor of the p38 MAPK pathway ( P < 0.05). Besides, TBL-12 could induce the apoptosis of PCa cells by activating caspase-9, caspase-7, and poly(ADP-ribose) polymerase and suppressing survivin, and inhibit the secretion of angiogenin, angiopoietin-2, and vascular endothelial growth factor in PCa cells.

CONCLUSIONS

Sea cucumber extract TBL-12 could suppress the proliferation and metastasis of human PCa cells by inhibiting MMP-2 and MMP-9 via blocking the p38 MAPK pathway, inducing apoptosis through intrinsic caspase apoptosis pathway and inhibiting the secretion of angiogenic factors. Our findings may be of importance and significance for the research and clinical applications of sea cucumber extract in PCa treatment.

The study of the calpain and caspase-1 expression in ultrastructural dynamics of Ehrlich ascites carcinoma necrosis

An expression of calpain and caspase-1 as well as the concomitant ultrastructural alterations were investigated during necrosis of the mouse Ehrlich ascites carcinoma. The calpain expression was registered at 0 h and 1 h although caspase-1 did not induce any signals during these time periods. The rise of the cytoplasmic lytic zones contacted by calpain antibodies was identified as a morphologic event corresponding to the expression of calpain. Lytic zone's distribution followed by the appearance of the calpain/caspase-1 clusters assigned for lysis of the Golgi vesicles and ER. Also, the microapocrine secretion of the vesicles containing the calpain/caspase-1 clusters was detected. Further, the lysis of the plasma membrane occurred due to progression of intracellular lysis. Rupture of the plasma membrane resulted in the termination of secretion and dissemination of cell contents. The nuclei still had their normal shape. Nuclear lysis continued to rise with intranuclear lytic zones, of which the progression was accompanied with the presence of calpain/caspase-1 clusters. The data contribute to the concept of the initial role of calpain for tumor cell destruction, provide first evidence of the calpain/caspase-1 pathway in tumor cells, and highlight microapocrine secretion as a possible tumor cell death signalling mechanism.

Mechanisms of cancer cell killing by sea cucumber-derived compounds

The aim of cancer therapy is to specifically eradicate tumor cells while causing minimal damage to normal tissues and minimal side-effects. Because of this, the use of natural substances with low toxicity is a good option. Sea cucumbers are one of many potential marine animals that contain valuable nutrients and medicinal properties. The medicinal value of sea cucumbers is attributed to the presence of bioactive agents with promising biological and pharmacological properties that include cytotoxic activity, induction of apoptosis, cell cycle arrest, inhibition of tumor growth, anti-metastatic and anti-angiogenic properties, and inhibition of drug resistance. This review discusses the mechanisms of cancer cell death induced by sea cucumber-derived compounds with regard to exploring the potential use of these marine natural products for cancer therapy.

Nanoparticulate Tubular Immunostimulating Complexes: Novel Formulation of Effective Adjuvants and Antigen Delivery Systems

New generation vaccines, based on isolated antigens, are safer than traditional ones, comprising the whole pathogen. However, major part of purified antigens has weak immunogenicity. Therefore, elaboration of new adjuvants, more effective and safe, is an urgent problem of vaccinology. Tubular immunostimulating complexes (TI-complexes) are a new type of nanoparticulate antigen delivery systems with adjuvant activity. TI-complexes consist of cholesterol and compounds isolated from marine hydrobionts: cucumarioside A2-2 (CDA) from Cucumaria japonica and monogalactosyldiacylglycerol (MGDG) from marine algae or seagrass. These components were selected due to immunomodulatory and other biological activities. Glycolipid MGDG from marine macrophytes comprises a high level of polyunsaturated fatty acids (PUFAs), which demonstrate immunomodulatory properties. CDA is a well-characterized individual compound capable of forming stable complex with cholesterol. Such complexes do not possess hemolytic activity. Ultralow doses of cucumariosides stimulate cell as well as humoral immunity. Therefore, TI-complexes comprising biologically active components turned out to be more effective than the strongest adjuvants: immunostimulating complexes (ISCOMs) and complete Freund's adjuvant. In the present review, we discuss results published in series of our articles on elaboration, qualitative and quantitative composition, ultrastructure, and immunostimulating activity of TI-complexes. The review allows immersion in the history of creating TI-complexes.

Glycosides from edible sea cucumbers stimulate macrophages via purinergic receptors

Since ancient times, edible sea cucumbers have been considered a jewel of the seabed and used in Asian folk medicine for stimulation of resistance against different diseases. However, the power of this sea food has not been established on a molecular level. A particular group of triterpene glycosides was found to be characteristic metabolites of the animals, responsible for this biological action. Using one of them, cucumarioside A₂-2 (CA₂-2) from the edible Cucumaria japonica species as an example as well as inhibitory analysis, patch-clamp on single macrophages, small interfering RNA technique, immunoblotting, SPR analysis, computer modeling and other methods, we demonstrate low doses of CA₂-2 specifically to interact with P2X receptors (predominantly P2X4) on membranes of mature macrophages, enhancing the reversible ATP-dependent Ca²⁺ intake and recovering Ca²⁺ transport at inactivation of these receptors. As result, interaction of glycosides of this type with P2X receptors leads to activation of cellular immunity.

In vitroAnticancer Activities of Some Triterpene Glycosides from Holothurians of Cucumariidae, Stichopodidae, Psolidae, Holothuriidae and Synaptidae families

Triterpene glycosides isolated from holothurians are natural products known to possess cytotoxic properties against cancer cells. However, their anticancer prophylactic activity has not been studied sufficiently. The anticancer prophylactic, cytotoxic, and pro-apoptotic properties of 18 triterpene glycosides, as well as their effects on the transcriptional activities of activator protein-1 (AP-1) and nuclear factor-κB (NF-κB), were examined using methods that included EGF-induced JB6 Cl41 P+ cell transforation in soft agar, flow cytometry, MTS assessment of cell viability, and a luciferase activity assay. The compounds inhibited EGF-induced neoplastic JB6 Cl41 P+ cell transforation in soft agar and caused apoptosis and necrosis of human HL-60 and THP-1 leukemia cells. AP-1 and NF-κB were involved in the cellular response to the treatment by the compounds. Conclusion: glycosides isolated from holothurians of Cucumariidae, Stichopodidae, Psolidae, Holothuriidae and Synaptidae families have potential for development as new antitumor agents and as instruments to study AP-1 and NF-κB.

Cytotoxic and anti-colorectal tumor effects of sulfated saponins from sea cucumber Holothuria moebii

BACKGROUND

Whether sulfated saponins from Holothuria moebii inhibit the proliferation of colorectal cancer cells and have anti-colorectal tumor effects in animal model has not been investigated.

PURPOSE

To evaluate the cytotoxic and anti-colorectal tumor effects of sulfated saponins from sea cucumber Holothuria moebii.

METHOD

(1) Column chromatography was used to prepare the total and individual saponins and HPLC was applied to define the components of the total saponins; (2) the activity of the total and individual saponins inhibiting the proliferation of human colorectal cancer cells was determined by SRB assay and the apoptosis induced by the saponins was qualified using cytometric analysis with Annexin V-FITC/PI double staining; and (3) the antitumor effects of the sulfated saponins on colorectal CT-26 tumor-bearing Balb/c mice were tested.

RESULTS

The total and individual sulfated saponins significantly inhibited the proliferation of four different human colorectal cancer cells with IC50 values ranging from 1.04 to 4.08 μM (or 1.46 to 3.24 μg/ml for total saponins) and induced late apoptosis at an early treatment time in cancer cells. The total saponins (120 mg/kg) had antitumor activity in colorectal CT-26 tumor-bearing Balb/c mice.

CONCLUSION

The sulfated saponins from H. moebii remarkably inhibited the proliferation of different human colorectal cancer cells and had significant anti-colorectal tumor activity in animal model.

Anticancer activity of sea cucumber triterpene glycosides

Triterpene glycosides are characteristic secondary metabolites of sea cucumbers (Holothurioidea, Echinodermata). They have hemolytic, cytotoxic, antifungal, and other biological activities caused by membranotropic action. These natural products suppress the proliferation of various human tumor cell lines in vitro and, more importantly, intraperitoneal administration in rodents of solutions of some sea cucumber triterpene glycosides significantly reduces both tumor burden and metastasis. The anticancer molecular mechanisms include the induction of tumor cell apoptosis through the activation of intracellular caspase cell death pathways, arrest of the cell cycle at S or G2/M phases, influence on nuclear factors, NF-κB, and up-down regulation of certain cellular receptors and enzymes participating in cancerogenesis, such as EGFR (epidermal growth factor receptor), Akt (protein kinase B), ERK (extracellular signal-regulated kinases), FAK (focal adhesion kinase), MMP-9 (matrix metalloproteinase-9) and others. Administration of some glycosides leads to a reduction of cancer cell adhesion, suppression of cell migration and tube formation in those cells, suppression of angiogenesis, inhibition of cell proliferation, colony formation and tumor invasion. As a result, marked growth inhibition of tumors occurs in vitro and in vivo. Some holothurian triterpene glycosides have the potential to be used as P-gp mediated MDR reversal agents in combined therapy with standard cytostatics.

Relationships between chemical structures and functions of triterpene glycosides isolated from sea cucumbers

Many marine triterpene glycosides have in vitro and in vivo activities with very low toxicity, suggesting that they are suitable agents for the prevention and treatment of different diseases, particularly cancer. However, the molecular mechanisms of action of natural marine compounds in cancer, immune, and other various cells are not fully known. This review focuses on the structural characteristics of marine triterpene glycosides and how these affect their biological activities and molecular mechanisms. In particular, the membranotropic and membranolytic activities of frondoside A and cucumariosides from sea cucumbers and their ability to induce cytotoxicity and apoptosis have been discussed, with a focus on structure-activity relationships. In addition, the structural characteristics and antitumor effects of stichoposide C and stichoposide D have been reviewed along with underlying their molecular mechanisms.

Marine low molecular weight natural products as potential cancer preventive compounds

Due to taxonomic positions and special living environments, marine organisms produce secondary metabolites that possess unique structures and biological activities. This review is devoted to recently isolated and/or earlier described marine compounds with potential or established cancer preventive activities, their biological sources, molecular mechanisms of their action, and their associations with human health and nutrition. The review covers literature published in 2003–2013 years and focuses on findings of the last 2 years.