Sergey N. Fedorov

Anticancer and cancer preventive properties of marine polysaccharides: some results and prospects.

Many marine-derived polysaccharides and their analogues have been reported as showing anticancer and cancer preventive properties. These compounds demonstrate interesting activities and special modes of action, differing from each other in both structure and toxicity profile. Herein, literature data concerning anticancer and cancer preventive marine polysaccharides are reviewed. The structural diversity, the biological activities, and the molecular mechanisms of their action are discussed.

Differential effects of triterpene glycosides, frondoside A and cucumarioside A2-2 isolated from sea cucumbers on caspase activation and apoptosis of human leukemia cells

Frondoside A is a pentaoside having an acetyl moiety at the aglycon ring and xylose as a third monosaccharide residue. Cucumarioside A2‐2 is a pentaoside having glucose as a third monosaccahride unit. We compared the effects of frondoside A and A2‐2 for cell death‐inducing capability with close attention paid to structure–activity relationships. Both frondoside A and A2‐2 strongly induced apoptosis of leukemic cells. Frondoside A‐induced apoptosis was more potent and rapid than A2‐2‐induced apoptosis. A2‐2‐induced but not frondoside A‐induced apoptosis was caspase‐dependent. This suggests that holothurians may induce apoptosis of leukemic cells caspase‐dependently or ‐independently, depending on the holothurian structure.

Constituents of the sea cucumber Cucumaria okhotensis. Structures of okhotosides B1-B3 and cytotoxic activities of some glycosides from this species

Three new triterpene oligoglycosides, okhotosides B 1 ( 1), B 2 ( 2), and B 3 ( 3), have been isolated from the sea cucumber Cucumaria okhotensis along with the known compounds frondoside A ( 4), frondoside A 1, cucumarioside A 2-5, and koreoside A. The structures of 1- 3 were elucidated on the basis of their spectroscopic data (2D NMR and MS). Compounds 1- 3 were moderately toxic against HeLa tumor cells. Frondoside A ( 4) showed more potent cytotoxicity against THP-1 and HeLa tumor cell lines (with IC 50 values of 4.5 and 2.1 microg/mL, respectively) and decreased both the AP-1-dependent trascriptional activities induced by UVB, EGF, or TPA in JB6-LucAP-1 cells and the EGF-induced NF-kappaB-dependent transcriptional activity in JB6-LucNF-kB cells at doses of about 1 microg/mL. At the same doses, it increased the p53-dependent transcriptional activity in nonactivated JB6-Lucp53 cells and inhibited the colony formation of JB6 P (+) Cl 41 cells activated with EGF (INCC 50 = 0.8 microg/mL).

The anticancer effects of actinoporin RTX-A from the sea anemone Heteractis crispa (=Radianthus macrodactylus)

Four isoforms of actinoporins were isolated in 2002-2004 from the tropical sea anemone Heteractis crispa (=Radianthus macrodactylus). Their potent hemolytic activities and effects on Ehrlich ascites carcinoma bearing mice were also studied. In this study, the individual actinoporin (RTX-A) demonstrated potential cancer-preventive activity at extremely low and non-cytotoxic concentrations. The substance suppressed the malignant transformation of mouse JB6 P(+) Cl41 cells stimulated by epidermal growth factor (EGF) in soft agar with the inhibition of number of the colonies C(50) (INCC(50))=0.034 nM. Actinoporin RTX-A also was shown to inhibit the phenotype expression of HeLa human cancer cells with an INCC(50)=0.03 nM. The cytotoxic effect of RTX-A against JB6 P(+) Cl41 cells and HeLa, THP-1, MDA-MB-231, and SNU-C4 human tumor cell lines was high (IC(50)=0.57, 2.26, 1.11, 30.0 and 4.66 nM), but significantly less than their capacity to suppress tumor cell colony formation or phenotype expression. RTX-A also induced apoptosis and inhibited basal AP-1, NF-kappaB, and p53-dependent transcriptional activity in JB6 Cl41 cells. These results confirmed that actinoporin RTX-A from H. crispa, at least partially, might exhibit cancer-preventive and anticancer cytotoxic properties through the induction of p53-independent apoptosis and inhibition of the oncogenic AP-1 and NF-kappaB nuclear factors activity.

Evaluation of cancer-preventive activity and structure-activity relationships of 3-demethylubiquinone Q2, isolated from the ascidian Aplidium glabrum, and its synthetic analogs.

Purpose3-Demethylubiquinone Q2 (1) was isolated from the ascidian Aplidium glabrum. The cancer-preventive properties and the structure–activity relationship for 3-demethylubiquinone Q2 (1) and 12 of its synthetic analogs (3–14) are reported.MethodsCompounds 3–14, having one or several di- or triprenyl substitutions and quinone moieties with methoxyls in different positions, were synthesized. The cancer-preventive properties of compounds 1 and 3–14 were tested in JB6 Cl41 mouse skin cells, using a variety of assessments, including the methanethiosulfonate (MTS) assay, flow cytometry, and soft agar assay. Statistical nonparametric methods were used to confirm statistical significance.ResultsAll quinones tested were shown to inhibit JB6 Cl41 cell transformation, to induce apoptosis, AP-1, and NF-κB activity, and to inhibit p53 activity. The most promising effects were indicated for compounds containing two isoprene units in a side chain and a methoxyl group at the para-position to a polyprenyl substitution.ConclusionsQuinones 1 and 3–14 demonstrated cancer-preventive activity in JB6 Cl41 cells, which may be attributed to the induction of p53-independent apoptosis. These activities depended on the length of side chains and on the positions of the methoxyl groups in the quinone part of the molecule.

Proteomic Profiling of Germ Cell Cancer Cells Treated with Aaptamine, a Marine Alkaloid with Antiproliferative Activity

Aaptamine is a marine compound isolated from the sponge Aaptos aaptos showing antiproliferative properties via an undefined mode of action. We analyzed the effects of aaptamine treatment on the proliferation and protein expression of the pluripotent human embryonal carcinoma cell line NT2. Effects on proliferation, cell cycle distribution, and induction of apoptosis were analyzed. At lower concentrations, including the IC50 of 50 μM, aaptamine treatment resulted in a G2/M phase cell cycle arrest, whereas at higher concentrations, induction of apoptosis was seen. Differentially expressed proteins were assessed by 2D-PAGE and mass spectrometry, followed by verification and analysis of protein modifications of the most significantly up- and down-regulated proteins. Aaptamine treatment at the IC50 for 48 h resulted in alteration of 10 proteins, of which five each showed up- and down-regulation. Changes in the 2D map were frequently noticed as a result of post-transcriptional modifications, e.g., of the hypusine modification of the eukaryotic initiation factor 5A (eIF5A). Observed alterations such as increased expression of CRABP2 and hypusination of eIF5A have previously been identified during differentiation of pluripotent cells. For the first time, we describe changes in protein expression caused by aaptamine, providing valuable information regarding the mode of action of this compound.

Dactylone inhibits epidermal growth factor-induced transformation and phenotype expression of human cancer cells and induces G1-S arrest and apoptosis

The marine natural chamigrane-type sesquiterpenoid, dactylone, is closely related to secondary metabolites of some edible species of red algae. In the present study, the effect of dactylone was tested on the mouse skin epidermal JB6 P+ Cl41 cell line and its stable transfectants as well as on several human tumor cell lines, including lung (H460), colon (HCT-116), and skin melanomas (SK-MEL-5 and SK-MEL-28). This natural product was effective at nontoxic doses as a cancer-preventive agent, which exerted its actions, at least in part, through the inhibition of cyclin D3 and Cdk4 expression and retinoblastoma tumor suppressor protein (Rb) phosphorylation. The inhibition of these cell cycle components was followed by cell cycle arrest at the G1-S transition with subsequent p53-independent apoptosis. Therefore, these data showed that application of dactylone and related compounds may lead to decreased malignant cell transformation and/or decreased tumor cell proliferation.

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.

Activity of aaptamine and two derivatives, demethyloxyaaptamine and isoaaptamine, in cisplatin-resistant germ cell cancer

UNLABELLED We analyzed the effects of all three marine alkaloids aaptamine, demethyloxyaaptamine and isoaaptamine in NT2-R, a cisplatin-resistant subline of the human embryonal carcinoma cell line NT2. All aaptamines were found to be equally effective in both cell lines, excluding cross-resistance between aaptamines and cisplatin in vitro. At the inhibitory concentration (IC50), aaptamine exerted an antiproliferative effect, whereas demethyloxyaaptamine and isoaaptamine were strong inducers of apoptosis. We analyzed the changes in the proteome of NT2-R cells treated with these compounds. 16-22 proteins were found to be significantly altered, of which several were validated by Western blotting and two-dimensional Western blotting analysis. Changes in the proteome pattern frequently resulted from post-transcriptional protein modifications, i.e. phosphorylation or hypusination in the case of eIF5A. Although the lists of altered proteins were heterogeneous and compound-specific, gene ontology analyses identified rather similar profiles regarding the affected molecular functions. Ingenuity pathway analysis by IPA put the following factors in a central position of the hypothetical networks: myc and p53 for aaptamine; tumor necrosis factor (TNF) for demethyloxyaaptamine; and all three, myc, p53, and TNF for isoaaptamine. Our results represent an important step towards a better understanding of the molecular basis underlying the observed bioactivity of these promising marine compounds. BIOLOGICAL SIGNIFICANCE We characterized the mode of action of three aaptamines, marine natural compound with anti-tumor activity, using a functional proteomics approach and the cisplatin-resistant pluripotent human embryonal carcinoma cell line NT2-R. The manuscript is of particular scientific interest, as we could reveal the similarities and differences of the modes of action. Furthermore, we were able to identify several new targets of these promising compounds. We found hypusination of eIF5A to be a prominent feature exclusively of aaptamine treatment, as this was not observed upon treatment with demethyloxyaaptamine or isoaaptamine. Our results are a step towards unraveling the mode of action of these interesting compounds.

Marine Alkaloid Polycarpine and Its Synthetic Derivative Dimethylpolycarpine Induce Apoptosis in JB6 Cells Through p53- and Caspase 3-Dependent Pathways

No HeadingPurpose.Polycarpine from ascidian Polycarpa aurata was previously found to be active against different human tumor cells. In this study, we investigated the antitumor mechanisms of polycarpine and its synthetic derivative, desmethoxyethoxy-polycarpine (dimethylpolycarpine), through the induction of apoptosis. This new knowledge regarding the proapoptotic action of polycarpine and dimethylpolycarpine should lead to a better understanding of their effects and development of a new class of anticancer drugs.Methods.Apoptosis was clearly observed by flow cytometry and Western blotting using an antibody against cleaved caspase-3 as an apoptotic marker.Results.Polycarpines differentially activated p38 kinase, JNKs, and ERKs in JB6 Cl 41 cells. The polycarpines-induced apoptosis was decreased in cells expressing a dominant-negative mutant of JNK. Both compounds stimulated p53-dependent transcriptional activity and phosphorylation. Induction of p53-phosphorylation at serine 15 was suppressed in JNK1 and JNK2 knockout cells. Furthermore, polycarpines were unable to induce apoptosis in p53-deficient MEFs in contrast to a strong induction of apoptosis in wild type MEFs, suggesting that p53 is involved in apoptosis induced by polycarpines. The p53 phosphorylation in turn was mediated by activated JNKs.Conclusions.These results indicate that all three MAPK signaling pathways are involved in the response of JB6 cells to treatment with polycarpines. Evidence also supports a proapoptotic role of the JNKs signaling pathway in vivo and clearly indicates that JNKs are required for phosphorylation of c-Jun, activation of p53, and subsequent apoptosis induced by polycarpines.