Rare Ophiuroid-Type Steroid 3β,21-, 3β,22-, and 3α,22-Disulfates from the Slime Sea Star Pteraster marsippus and Their Colony-Inhibiting Effects against Human Breast Cancer Cells

Two new steroid 3β,21-disulfates (1, 2) and two new steroid 3β,22- and 3α,22-disulfates (3, 4), along with the previously known monoamine alkaloid tryptamine (5) were found in the ethanolic extract of the Far Eastern slime sea star Pteraster marsippus. Their structures were determined on the basis of detailed analysis of one-dimensional and two-dimensional NMR, HRESIMS, and HRESIMS/MS data. Compounds 1 and 2 have a Δ22-21-sulfoxy-24-norcholestane side chain. Compounds 3 and 4 contain a Δ24(28)-22-sulfoxy-24-methylcholestane side chain, which was first discovered in the polar steroids of starfish and brittle stars. The influence of substances 1-4 on cell viability, colony formation, and growth of human breast cancer T-47D, MCF-7, and MDA-MB-231 cells was investigated. It was shown that compounds 1 and 2 possess significant colony-inhibiting activity against T-47D cells, while compounds 3 and 4 were more effective against MDA-MB-231 cells.

New Rare Triterpene Glycosides from Pacific Sun Star, Solaster pacificus, and Their Anticancer Activity

Six previously unknown triterpene glycosides, pacificusosides L-Q (1-6), and two previously known triterpene glycosides, cucumariosides B1 (7) and A5 (8), were isolated from an alcoholic extract of Pacific sun star, Solaster pacificus. The structures of 1-6 were determined using 1D and 2D NMR, ESIMS, and chemical modifications. Compound 1 is a rare type of triterpene glycoside with non-holostane aglycon, having a linear trisaccharide carbohydrate chain. Pacificusosides M-P (2-5) have new structures containing a Δ8(9)-3,16,18-trihydroxy tetracyclic triterpene moiety. This tetracyclic fragment in sea star or sea cucumber triterpene glycosides was described for the first time. All the compounds under study exhibit low or moderate cytotoxic activity against colorectal carcinoma HCT 116 cells, and breast cancer MDA-MB-231 cells were assessed by MTS assay. Compound 2 effectively suppresses the colony formation of cancer cells at a non-toxic concentration, using the soft-agar assay. A scratch assay has shown a significant anti-invasive potential of compound 2 against HCT 116 cells, but not against MDA-MB-231 cells.

Production of high- and low-molecular weight fucoidan fragments with defined sulfation patterns and heightened in vitro anticancer activity against TNBC cells using novel endo-fucanases of the GH107 family

Fucoidans are complex fucose-containing sulfated polysaccharides with pronounced anticancer effects. Their structure-anticancer activity relationships are difficult to determine due to fucoidans' complex, often irregularities-including structures. Fucoidan-active enzymes can be used for this propose. We have investigated two new recombinant endo-fucanases FWf3 and FWf4 from the marine bacterium Wenyingzhuangia fucanilytica CZ1127^T that belong to the 107 family of glycoside hydrolases (GH). Both enzymes cleaved α-(1→4)-glycosidic bonds but in fucoidan fragments with different sulfation patterns. FWf3 is the first characterized endo-fucanase that cleaves glycosidic bonds between 2O- and 2,4diO-sulfated L-fucose residues. The obtained endo-fucanases were used to produce low- and high-molecular weight fucoidan derivatives with different sulfate group locations. Low- and high-molecular weight fucoidan derivatives rich with 2,4diO-sulfation were shown to inhibit MDA-MB-231 cell colony formation more efficiently than the native fucoidan and the derivatives sulfated otherwise. Such derivatives effectively suppressed the mitochondrial membrane potential of MDA-MB-231 cells and reduced the expression of the glucose transporter 1 (GLUT1). Co-treatment of MDA-MB-231 cells with the fucoidan derivatives and oligomycin (an OXPHOS inhibitor) resulted in a synergistic anticancer effect. The data obtained demonstrate, that fucoidan and its 2,4diO-sulfated derivatives can be an effective adjunct in TNBC therapy targeting cell metabolism.

Structure and Metabolically Oriented Efficacy of Fucoidan from Brown Alga Sargassum muticum in the Model of Colony Formation of Melanoma and Breast Cancer Cells

This work reports the detailed structure of fucoidan from Sargassum miticum (2SmF2) and its ability to potentiate the inhibitory effect of glycolysis inhibitor 2-deoxy-d-glucose (2-DG). 2SmF2 was shown to be sulfated and acetylated galactofucan containing a main chain of alternating residues of 1,3- and 1,4-linked α-l-fucopyranose, fucose fragments with monotonous 1,3- and 1,4-type linkages (DP up to 3), α-d-Gal-(1→3)-α-L-Fuc disaccharides, and 1,3,4- and 1,2,4-linked fucose branching points. The sulfate groups were found at positions 2 and 4 of fucose and galactose residues. 2SmF2 (up to 800 µg/mL) and 2-DG (up to 8 mM) were not cytotoxic against MDA-MB-231 and SK-MEL-28 as determined by MTS assay. In the soft agar-based model of cancer cell colony formation, fucoidan exhibited weak inhibitory activity at the concentration of 400 µg/mL. However, in combination with low non-cytotoxic concentrations of 2-DG (0.5 or 2 mM), 2SmF2 could effectively inhibit the colony formation of SK-MEL-28 and MDA-MB-231 cells and decreased the number of colonies by more than 50% compared to control at the concentration of 200 µg/mL. Our findings reveal the metabolically oriented effect of fucoidan in combination with a glycolysis inhibitor that may be beneficial for a therapy for aggressive cancers.

The Combined Metabolically Oriented Effect of Fucoidan from the Brown Alga Saccharina cichorioides and Its Carboxymethylated Derivative with 2-Deoxy-D-Glucose on Human Melanoma Cells

Melanoma is the most aggressive and treatment-resistant form of skin cancer. It is phenotypically characterized by aerobic glycolysis that provides higher proliferative rates and resistance to cell death. The glycolysis regulation in melanoma cells by means of effective metabolic modifiers represents a promising therapeutic opportunity. This work aimed to assess the metabolically oriented effect and mechanism of action of fucoidan from the brown alga Saccharina cichorioides (ScF) and its carboxymethylated derivative (ScFCM) in combination with 2-deoxy-D-glucose (2-DG) on the proliferation and colony formation of human melanoma cell lines SK-MEL-28, SK-MEL-5, and RPMI-7951. The metabolic profile of melanoma cells was determined by the glucose uptake and Lactate-GloTM assays. The effect of 2-DG, ScF, ScFCM, and their combination on the proliferation, colony formation, and activity of glycolytic enzymes was assessed by the MTS, soft agar, and Western blot methods, respectively. When applied separately, 2-DG (IC50 at 72 h = 8.7 mM), ScF (IC50 at 72 h > 800 µg/mL), and ScFCM (IC50 at 72 h = 573.9 μg/mL) inhibited the proliferation and colony formation of SK-MEL-28 cells to varying degrees. ScF or ScFCM enhanced the inhibiting effect of 2-DG at low, non-toxic concentrations via the downregulation of Glut 1, Hexokinase II, PKM2, LDHA, and pyruvate dehydrogenase activities. The obtained results emphasize the potential of the use of 2-DG in combination with algal fucoidan or its derivative as metabolic modifiers for inhibition of melanoma SK-MEL-28 cell proliferation.

Combined Radiomodifying Effect of Fucoidan from the Brown Alga Saccharina cichorioides and Pacificusoside D from the Starfish Solaster pacificus in the Model of 3D Melanoma Cells

Cancer is one of the main causes of human mortality worldwide. Despite the advances in the diagnostics, surgery, radiotherapy, and chemotherapy, the search for more effective treatment regimens and drug combinations are relevant. This work aimed to assess the radiomodifying effect and molecular mechanism of action of fucoidan from the brown alga Saccharina cichorioides (ScF) and product of its autohydrolysis (ScF_AH) in combination with pacificusoside D from the starfish Solaster pacificus (SpD) on the model of viability and invasion of three-dimension (3D) human melanoma cells SK-MEL-2. The cytotoxicity of ScF (IC50 JB6 Cl41 > 800 µg/mL; IC50 SK-MEL-2 = 685.7 µg/mL), ScF_AH (IC50 JB6 Cl41/SK-MEL-2 > 800 µg/mL), SpD (IC50 JB6 Cl41 = 22 µM; IC50 SK-MEL-2 = 5.5 µM), and X-ray (ID50 JB6 Cl41 = 11.7 Gy; ID50 SK-MEL-2 = 6.7 Gy) was determined using MTS assay. The efficiency of two-component treatment of 3D SK-MEL-2 cells was revealed for ScF in combination with SpD or X-ray but not for the combination of fucoidan derivative ScF_AH with SpD or X-ray. The pre-treatment of spheroids with ScF, followed by cell irradiation with X-ray and treatment with SpD (three-component treatment) at low non-toxic concentrations, led to significant inhibition of the spheroids' viability and invasion and appeared to be the most effective therapeutic scheme for SK-MEL-2 cells. The molecular mechanism of radiomodifying effect of ScF with SpD was associated with the activation of the initiator and effector caspases, which in turn caused the DNA degradation in SK-MEL-2 cells as determined by the Western blotting and DNA comet assays. Thus, the combination of fucoidan from brown algae and triterpene glycoside from starfish with radiotherapy might contribute to the development of highly effective method for melanoma therapy.

The carboxymethylated derivative of laminaran from brown alga Saccharina cichorioides: Structure, anticancer and anti-invasive activities in 3D cell culture

Polysaccharides' derivatives are promising biologically active compounds for biotechnology, nutrition, industries, and are becoming increasingly important in medicine and pharmacy. Laminaran from brown alga Saccharina cichorioides (ScL) was chemically modified to obtain the carboxymethylated derivative (ScLCM) with improved structure and bioactivity. ScLCM was identified as (1 → 3)-β-D-glucan with -CH2-COOH groups at some positions 2, 4, and 6 of glucose residues. The anticancer activity of ScLCM was studied on the models of viability and invasion of 3D human melanoma SK-MEL-28, breast cancer T-47D, and colorectal carcinoma DLD-1 cells in comparison with native laminaran or its sulfated or aminated derivatives. ScLCM had the highest anticancer and anti-invasive effects among investigated polysaccharides. ScLCM significantly suppressed the viability and invasion of 3D SK-MEL-28 cells via the regulation of the activity of matrix metalloproteinase 9 (MMP 9) and protein kinases of ERK/MAPK signaling pathway. These findings may contribute to the reported anticancer effects of algal polysaccharides' derivatives.

Structure and chemopreventive activity of fucoidans from the brown alga Alaria angusta

Six fucoidan fractions were isolated from the brown alga Alaria angusta. Structures of enzymatic hydrolysis products of the fraction 1AaF2 (Fuc:Gal ~ 1:1; 33 % of sulfates) by fucanase from Wenyingzhuangia fucanilytica were studied by chemical and instrumental (NMR spectroscopy and mass-spectrometry) methods. It was shown that 1AaF2 consisted of two structurally different fucoidans: a sulfated 1,3;1,4-α-L-fucan and an enzyme-resistant sulfated and acetylated complex fucogalactan (Fuc:Gal ~ 1:2; 19 % of sulfates) 1AaF2_HMP containing extended 1,3-linked fucose and 1,3/1,4-linked galactose fragments (up to 5 residues). The fractions 1AaF2 and 1AaF2_HMP were a non-cytotoxic, possessed dose-dependent chemopreventive effect on EGF-induced neoplastic cell transformation of mouse normal epidermal JB6 Cl41 cells and inhibited the colony formation of human melanoma SK-MEL-28 cells.

New Ceramides and Cerebrosides from the Deep-Sea Far Eastern Starfish Ceramaster patagonicus

Three new ceramides (1−3) and three new cerebrosides (4, 8, and 9), along with three previously known cerebrosides (ophidiocerebrosides C (5), D (6), and CE-3-2 (7)), were isolated from a deep-sea starfish species, the orange cookie starfish Ceramaster patagonicus. The structures of 1−4, 8, and 9 were determined by the NMR and ESIMS techniques and also through chemical transformations. Ceramides 1−3 contain iso-C21 or C23 Δ9-phytosphingosine as a long-chain base and have C16 or C17 (2R)-2-hydroxy-fatty acids of the normal type. Cerebroside 4 contains C22 Δ9-sphingosine anteiso-type as a long-chain base and (2R)-2-hydroxyheptadecanoic acid of the normal type, while compounds 8 and 9 contain saturated C-17 phytosphingosine anteiso-type as a long-chain base and differ from each other in the length of the polymethylene chain of (2R)-2-hydroxy-fatty acids of the normal type: C23 in 8 and C24 in 9. All the new cerebrosides (4, 8, and 9) have β-D-glucopyranose as a monosaccharide residue. The composition of neutral sphingolipids from C. patagonicus was described for the first time. The investigated compounds 1−3, 5−7, and 9 exhibit slight to moderate cytotoxic activity against human cancer cells (HT-29, SK-MEL-28, and MDA-MB-231) and normal embryonic kidney cells HEK293. Compounds 2, 5, and 6 at a concentration of 20 µM inhibit colony formation of MDA-MB-231 cells by 68%, 54%, and 68%, respectively. The colony-inhibiting activity of compounds 2, 5, and 6 is comparable to the effect of doxorubicin, which reduces the number of colonies by 70% at the same concentration.

Disulfated Ophiuroid Type Steroids from the Far Eastern Starfish Pteraster marsippus and Their Cytotoxic Activity on the Models of 2D and 3D Cultures

New steroidal 3β,21-disulfates (2–4), steroidal 3β,22-disulfate (5), and the previously known related steroidal 3β,21-disulfate (1) were isolated from the ethanolic extract of the Far Eastern starfish Pteraster marsippus, collected off Urup Island in the Sea of Okhotsk. The structures of these compounds were determined by intensive NMR and HRESIMS techniques as well as by chemical transformations. Steroids 2 and 3 have an oxo-group in the tetracyclic nucleus at position C-7 and differ from each other by the presence of the 5(6)-double bond. The Δ²⁴-22-sulfoxycholestane side chain of the steroid 5 has not been found previously in the starfish or ophiuroid steroids. The cytotoxic activities of 1, 4, 5, and the mixture of 2 and 3 were determined on the models of 2D and 3D cultures of human epithelial kidney cells (HEK293), melanoma cells (SK-MEL-28), small intestine carcinoma cells (HuTu80), and breast carcinoma cells (ZR-75-1). The mixture of 2 and 3 revealed a significant inhibitory effect on the cell viability of human breast carcinoma ZR-75-1 cells, but other tested compounds were less effective.

Structural diversity of fucoidans and their radioprotective effect

Fucoidans are biologically active sulfated polysaccharides of brown algae. They have a great structural diversity and a wide spectrum of biological activity. This review is intended to outline what is currently known about the structures of fucoidans and their radioprotective effect. We classified fucoidans according to their composition and structure, examined the structure of fucoidans of individual representatives of algae, summarized the available data on changes in the yields and compositions of fucoidans during algae development, and focused on information about underexplored radioprotective effect of these polysaccharides. Based on the presented in the review data, it is possible to select algae, which are the sources of fucoidans of desired structures and to determine the best time to harvest them. The use of high purified polysaccharides with established structures increase the value of studies of their biological effects and the determination of the dependence "structure - biological effect".

Combined Anticancer Effect of Sulfated Laminaran from the Brown Alga Alaria angusta and Polyhydroxysteroid Glycosides from the Starfish Protoreaster lincki on 3D Colorectal Carcinoma HCT 116 Cell Line

Colorectal cancer is one of the most frequent types of malignancy in the world. The search for new approaches of increasing the efficacy of cancer therapy is relevant. This work was aimed to study individual, combined anticancer effects, and molecular mechanism of action of sulfated laminaran AaLs of the brown alga Alaria angusta and protolinckiosides A (PL1), B (PL2), and linckoside L1 (L1) of the starfish Protoreaster lincki using a 3D cell culture model. The 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS), soft agar, 3D spheroids invasion, and Western blotting assays were performed to determine the effect and mechanism of the action of investigated compounds or their combinations on proliferation, colony formation, and the invasion of 3D HCT 116 spheroids. AaLs, PL1, PL2, and L1 individually inhibited viability, colony growth, and the invasion of 3D HCT 116 spheroids in a variable degree with greater activity of linckoside L1. AaLs in combination with L1 exerted synergism of a combined anticancer effect through the inactivation of protein kinase B (AKT) kinase and, consequently, the induction of apoptosis via the regulation of proapoptotic/antiapoptotic proteins balance. The obtained data about the efficacy of the combined anticancer effect of a laminaran derivative of brown algae and polyhydroxysteroid glycosides of starfish open up prospects for the development of new therapeutic approaches for colorectal cancer treatment.

Fucoidan from brown algae Fucus evanescens potentiates the anti-proliferative efficacy of asterosaponins from starfish Asteropsis carinifera in 2D and 3D models of melanoma cells

This study was aimed to determine the efficacy of combination of fucoidan from the brown algae Fucus evanescens (FeF) or its derivatives with thornasteroside A (ThA) or asteropsiside A (AsA) from the starfish Asteropsis carinifera in combating human melanoma cells. In vitro MTS and soft agar methods were performed to determine effect of FeF, its derivatives, ThA, AsA or their combination on proliferation and colony formation of SK-MEL-28 cells in 2D and 3D culture. Desulfation of FeF, but not deacetylation, led decreasing of its Mw and anti-proliferative activity. The combinatorial effect of FeF with ThA and AsA depended on the sequences of treatment by compounds. There was additive anticancer effect of FeF with ThA or AsA during simultaneous treatment of cells. ThA and AsA were not active against SK-MEL-28 cells after their pre-treatment with FeF. Potential synergism of action was identified only when SK-MEL-28 cells were pre-treated with ThA and AsA and then by FeF. This process going through the regulation of MEK1/2/ERK1/2/MSK1 pathway and expression of the cell cycle proteins as determined by Western Blot. Thus, the combination of fucoidan with the asterosaponins opens up the prospects for the development of effective combined chemotherapeutic methods for melanoma treatment.

The structure of fucoidan from Sargassum oligocystum and radiosensitizing activity of galactofucans from some algae of genus Sargassum

The aim of this study was to establish the fine structure of fucoidan from Sargassum oligocystum and to study the radiosensitizing effect of fucoidans from three algae of genus Sargassum (S. oligocystum, S. duplicatum, and S. feldmannii) with different structures. The fucoidan SoF2 from S. oligocystum was sulfated (32%) galactofucan (Fuc:Gal = 2:1), with a Mw of 183 kDa (Mw/Mn = 2.0). Its supposed structure was found to be predominantly 1,3-linked fucose as the main chain, with branching points at C2 and C4. The branches could be single galactose and/or fucose short chains with terminal galactose residues. Sulfate groups were found at positions C3, C2, and/or C4 of fucose residues and at C2 and/or C4 of galactose residues. The radiosensitizing effect of galactofucans from S. oligocystum, S. duplicatum, and S. feldmannii against human melanoma SK-MEL-28, colon HT-29, and breast MDA-MB-231 cancer cells was investigated. The influence of all investigated polysaccharides treatments with/without X-ray radiation on colony formation of human melanoma cells SK-MEL-28 was weak. Fucoidan from S. feldmannii has been shown to be the most promising radiosensitizing compound against human colon HT-29 and breast MDA-MB-231 cancer cells.

Aminated laminaran from brown alga Saccharina cichorioides: Synthesis, structure, anticancer, and radiosensitizing potential in vitro

Laminarans are currently the focus of attention in regard to the selection of prospective agents for the prevention and treatment of cancer. Laminaran from Saccharina cichorioides was aminated to heighten anticancer and radiosensitizing activities and elucidate its molecular mode of action. Aminated laminaran, ScLNH2, was identified as 1,3-β-d-glucan with -CH2-CH(OH)-CH2-NH2 group at the C6 of branches. ScLNH2 selectively inhibited the viability and colony formation in the MDA-MB-231 cell line of triple negative breast cancer cells. ScLNH2 possessed synergism with radiation, resulting in a decreased number of colonies of MDA-MB-231 cells. The mechanism underling the radiosensitizing effect of ScLNH2 was associated with apoptosis induction via regulation of caspases 9 and 3 and PARP enzyme, preventing the repair of DNA damage in irradiated cells. These findings confirmed that combination therapy by aminated laminaran and radiation might play a role in the optimization of therapy for an aggressive form of human breast cancer.

Laminarans and 1,3-β-D-glucanases

The laminarans are biologically active water-soluble polysaccharide (1,3;1,6-β-D-glucans) of brown algae. These polysaccharides are an attractive object for research due to its relatively simple structure, low toxicity, and various biological effects. 1,3-β-D-glucanases are an effective tool for studying the structure of laminarans, and can also be used to obtain new biologically active derivatives. This review is to outline what is currently known about laminarans and enzymes that catalyze of their transformation. We focused on information about sources, structure and properties of laminarans and 1,3-β-D-glucanases, methods of obtaining and structural elucidation of laminarans, and biological activity of laminarans and products of their enzymatic transformation. It has an increased focus on the immunomodulating and anticancer activity of laminarans and their derivatives.

Polar steroid compounds from the Arctic starfish Asterias microdiscus and their cytotoxic properties against normal and tumor cells in vitro

Two new natural compounds, sulfated polyhydroxysteroid, microdiscusol G (1), and polyhydroxysteroid bioside, microdiscusoside A (2), along with eight previously known polar steroid substances 3-10, were isolated from the Arctic starfish Asterias microdiscus. The structures of 1 and 2 have been elucidated by extensive 1D and 2D NMR spectroscopy and HRESIMS techniques. The 28-sulfooxy-24-methylcholestane side chain in 1 has been found among starfish steroid metabolites for the first time. Steroid saponins 9 and 10 exhibited cytotoxic effects against normal cells JB6 Cl41 and cancer cells HT-29, MDA-MB-231, THP-1, and Raji and effectively suppressed cell proliferation and colony formation of cancer cells HT-29 and MDA-MB-231 in non-toxic concentrations. Compounds 5, 7, and 8 were inactive or less active in the same experiments.

Enzymatic transformation and anti-tumor activity of Sargassum horneri fucoidan

Structure of the fucoidan from Sargassum horneri and products of its enzymatic transformation with molecular weight over 20 kDa were investigated. Fucoidan was hydrolyzed by recombinant fucoidanase FFA1 and its fraction of higher molecular weight was fractionated using anion-exchange chromatography, resulting in three sulphated polysaccharides of various molecular weight (63-138 kDa). Their structures were analyzed using NMR spectroscopy, showing the fucoidan (ShF) to be a branched polysaccharide with the backbone consisting of the repeating →3-α-l-Fucp(2SO3-)-1→4-α-l-Fucp(2,3SO3-)-1→ fragment and side chains including the α-l-Fucp-1→2-α-l-Fucp-1→ or α-l-Fucp-1→3-α-l-Fucp(4SO3-)-1→ fragments attached to the main chain at C4. The fragment F3 differing by molecular weight and side chain from other fucoidans fragments possessed the most significant anticancer and radiosensitizing activities.

Structures and Bioactivities of Quadrangularisosides A, A1, B, B1, B2, C, C1, D, D1-D4, and E from the Sea Cucumber Colochirus quadrangularis: The First Discovery of the Glycosides, Sulfated by C-4 of the Terminal 3-O-Methylglucose Residue. Synergetic Effect on Colony Formation of Tumor HT-29 Cells of these Glycosides with Radioactive Irradiation

Thirteen new mono-, di-, and trisulfated triterpene glycosides, quadrangularisosides A-D₄ (1-13) have been isolated from the sea cucumber Colochirus quadrangularis, which was collected in Vietnamese waters. The structures of these glycosides were established by 2D NMR spectroscopy and HR-ESI (High Resolution Electrospray Ionization) mass spectrometry. The novel carbohydrate moieties of quadrangularisosides D-D₄ (8-12), belonging to the group D, and quadrangularisoside E (13) contain three sulfate groups, with one of them occupying an unusual position-at C(4) of terminal 3-O-methylglucose residue. Quadrangularisosides A (1) and D₃ (11) as well as quadrangularisosides A₁ (2) and D₄ (12) are characterized by the new aglycones having 25-hydroperoxyl or 24-hydroperoxyl groups in their side chains, respectively. The cytotoxic activities of compounds 1-13 against mouse neuroblastoma Neuro 2a, normal epithelial JB-6 cells, erythrocytes, and human colorectal adenocarcinoma HT-29 cells were studied. All the compounds were rather strong hemolytics. The structural features that most affect the bioactivity of the glycosides are the presence of hydroperoxy groups in the side chains and the quantity of sulfate groups. The membranolytic activity of monosulfated quadrangularisosides of group A (1, 2) against Neuro 2a, JB-6 cells, and erythrocytes was relatively weak due to the availability of the hydroperoxyl group, whereas trisulfated quadrangularisosides D₃ (11) and D₄ (12) with the same aglycones as 1, 2 were the least active compounds in the series due to the combination of these two structural peculiarities. The erythrocytes were more sensitive to the action of the glycosides than Neuro 2a or JB-6 cells, but the structure-activity relationships observed for glycosides 1-13 were similar in the three cell lines investigated. The compounds 3-5, 8, and 9 effectively suppressed the cell viability of HT-29 cells. Quadrangularisosides A₁ (2), C (6), C₁ (7), and E (13) possessed strong inhibitory activity on colony formation in HT-29 cells. Due to the synergic effects of these glycosides (0.02 μM) and radioactive irradiation (1 Gy), a decreasing of number of colonies was detected. Glycosides 1, 3, and 9 enhanced the effect of radiation by about 30%.

In Vitro Anticancer and Radiosensitizing Activities of Phlorethols from the Brown Alga Costaria costata

The anticancer and radiosensitizing effects of high-molecular-weight phlorethols CcPh (Mw = 2520 Da) isolated from the brown algae of Costaria costata on human colorectal carcinoma HCT 116 and HT-29 cells were investigated. Phlorethols CcPh possessed cytotoxic activity against HT-29 (IC50 = 92 μg/mL) and HCT 116 (IC50 = 94 μg/mL) cells. CcPh at non-toxic concentrations inhibited the colony formation in colon cancer cells and significantly enhanced their sensitivity to low non-toxic X-ray irradiation. The combinatory effect of radiation and CcPh was synergistic (Combination index < 0.7). Algal phlorethols might be prospective candidates as radiosensitizers to improve the scheme of radiotherapy.

In Vitro and In Vivo Effects of Holotoxin A1 From the Sea Cucumber Apostichopus japonicus During Ionizing Radiation

Radiation therapy is one of the most important approaches to cancer therapy, but radiotoxicity to normal tissue is a serious limitation of this treatment. Compounds which are able to either sensitize cancer cells or protect normal cells to radiation are of great interest. The cytotoxicity of holotoxin A1 and the effects of radiation against DLD-1 and HT-29 cells were measured by MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay. The effect of the combination of holotoxin A1 with X-ray on colony formation of cancer cells was determined by the soft agar assay. The effect of holotoxin A1 on the recovery of peripheral blood leukocyte number, mass, and cellularity of the lymphoid organs of irradiated mice, as well as on growth of murine Ehrlich solid carcinoma was studied. Holotoxin A1 enhanced the sensitivity of colorectal carcinoma cells to radiation in vitro. Injection of holotoxin A1 to mice led to an increase in the spleen endogenous colony number and peripheral blood leukocyte number, as well as the weight and cellularity of the lymphoid organs of the irradiated mice. Holotoxin A1 in combination with X-ray radiation effectively inhibited the growth of Ehrlich solid carcinoma in vivo. Holotoxin A1 is suggested to be a promising agent for improving the efficiency of radiotherapy.

New Conjugates of Polyhydroxysteroids with Long-Chain Fatty Acids from the Deep-Water Far Eastern Starfish Ceramaster patagonicus and Their Anticancer Activity

Four new conjugates, esters of polyhydroxysteroids with long-chain fatty acids (1–4), were isolated from the deep-water Far Eastern starfish Ceramaster patagonicus. The structures of 1–4 were established by NMR and ESIMS techniques as well as chemical transformations. Unusual compounds 1–4 contain the same 5α-cholestane-3β,6β,15α,16β,26-pentahydroxysteroidal moiety and differ from each other in the fatty acid units: 5′Z,11′Z-octadecadienoic (1), 11′Z-octadecenoic (2), 5′Z,11′Z-eicosadienoic (3), and 7′Z-eicosenoic (4) acids. Previously, only one such steroid conjugate with a fatty acid was known from starfish. After 72 h of cell incubation, using MTS assay it was found that the concentrations of compounds 1, 2, and 3 that caused 50% inhibition of growth (IC₅₀) of JB6 Cl41 cells were 81, 40, and 79 µM, respectively; for MDA-MB-231 cells, IC₅₀ of compounds 1, 2, and 3 were 74, 33, and 73 µM, respectively; for HCT 116 cells, IC₅₀ of compounds 1, 2, and 3 were 73, 31, and 71 µM, respectively. Compound 4 was non-toxic against tested cell lines even in three days of treatment. Compound 2 (20 µM) suppressed colony formation and migration of MDA-MB-231 and HCT 116 cells.

Unusual Polyhydroxylated Steroids from the Starfish Anthenoides laevigatus, Collected off the Coastal Waters of Vietnam

Four new polyhydroxylated steroids 1–4 were isolated along with two previously known related steroids 5 and 6 from the methanolic extract of the starfish Anthenoides laevigatus collected off the coastal waters of Vietnam. Structures of new compounds were substantially elucidated by one-dimensional (1D) and two-dimensional (2D) NMR spectroscopy and HRESIMS techniques. Heptaol 1 and hexaol 2 contain the common 5α-cholestane skeleton, while hexaol 3 and heptaol 4 have the rare among starfish steroid compounds 5β-cholestane skeleton. Compounds 1, 5, and 6 do not show cytotoxic effects against normal JB6 Cl41 and cancer HT-29 and MDA-MB-231 cells, however they inhibit cell proliferation and colony formation of cancer HT-29 and MDA-MB-231 cells.

Fucoidans from brown algae Laminaria longipes and Saccharina cichorioides: Structural characteristics, anticancer and radiosensitizing activity in vitro

The sulfated α-l-fucans ScF and LlF were obtained from brown algae of the Laminariaceae family (Saccharina cichorioides and Laminaria longipes). According to spectroscopy NMR, the LlF fucan predominantly contained the →3)-α-l-Fucp-(2SO3-)-(1→4)-α-l-Fucp-(1→2)-α-l-Fucp-(4SO3-)-(1→ repeating units, with small amounts of disaccharide 1,4-linked fragments and 3-sulfated fucose residues. Mass spectrometric analysis revealed the presence of the following fragments in the fucan structure: α-l-Fucp-(2SO3-)-(1→4)-α-l-Fucp-(2SO3-)-(1→3)-α-l-Fucp-(4SO3-); α-l-Fucp-(2,4SO3-)-(1→3)-α-l-Fucp-(1→3)-α-l-Fucp-(4SO3-); α-l-Fucp-(2SO3-)-(1→2)-α-l-Fucp; α-l-Fucp-(2SO3-)-(1→2)-α-l-Fucp-(4SO3-); α-l-Fucp-(2SO3-)-(1→3)-α-l-Fucp; α-l-Fucp-(2,4SO3-)-(1→3)-α-l-Fucp; α-l-Fucp-(4SO3-)-(1→4)-α-l-Fucp; and α-l-Fucp-(4SO3-)-(1→4)-α-l-Fucp-(2SO3-). Both ScF and LlF fucoidans inhibited colony formation and growth of melanoma and colon cancer cells and sensitize-tested cancer cells to X-ray radiation to a comparable degree.

Effects of Polar Steroids from the Starfish Patiria (=Asterina) pectinifera in Combination with X-Ray Radiation on Colony Formation and Apoptosis Induction of Human Colorectal Carcinoma Cells

Despite significant advances in the understanding, prevention, and treatment of cancer, the disease continues to affect millions of people worldwide. Chemoradiation therapy is a rational approach that has already proven beneficial for several malignancies. However, the existence of toxicity to normal tissue is a serious limitation of this treatment modality. The aim of the present study is to investigate the ability of polar steroids from starfish Patiria (=Asterina) pectinifera to enhance the efficacy of radiation therapy in colorectal carcinoma cells. The cytotoxic activity of polar steroids and X-ray radiation against DLD-1, HCT 116, and HT-29 cells was determined by an MTS assay. The effect of compounds, X-ray, and their combination on colony formation was studied using the soft agar method. The molecular mechanism of the radiosensitizing activity of asterosaponin P₁ was elucidated by western blotting and the DNA comet assay. Polar steroids inhibited colony formation in the tested cells, and to a greater extent in HT-29 cells. Asterosaponin P₁ enhanced the efficacy of radiation and, as a result, reduced the number and size of the colonies of colorectal cancer cells. The radiosensitizing activity of asterosaponin P₁ was realized by apoptosis induction through the regulation of anti- and pro-apoptotic protein expression followed by caspase activation and DNA degradation.

Structures and Bioactivities of Six New Triterpene Glycosides, Psolusosides E, F, G, H, H1, and I and the Corrected Structure of Psolusoside B from the Sea Cucumber Psolus fabricii

Seven sulfated triterpene glycosides, psolusosides B (1), E (2), F (3), G (4), H (5), H₁ (6), and I (7), along with earlier known psolusoside A and colochiroside D have been isolated from the sea cucumber Psolus fabricii collected in the Sea of Okhotsk. Herein, the structure of psolusoside B (1), elucidated by us in 1989 as a monosulfated tetraoside, has been revised with application of modern NMR and particularly MS data and proved to be a disulfated tetraoside. The structures of other glycosides were elucidated by 2D NMR spectroscopy and HR-ESI mass-spectrometry. Psolusosides E (2), F (3), and G (4) contain holostane aglycones identical to each other and differ in their sugar compositions and the quantity and position of sulfate groups in linear tetrasaccharide carbohydrate moieties. Psolusosides H (5) and H₁ (6) are characterized by an unusual sulfated trisaccharide carbohydrate moiety with the glucose as the second sugar unit. Psolusoside I (7) has an unprecedented branched tetrasaccharide disulfated carbohydrate moiety with the xylose unit in the second position of the chain. The cytotoxic activities of the compounds 2-7 against several mouse cell lines-ascite form of Ehrlich carcinoma, neuroblastoma Neuro 2A, normal epithelial JB-6 cells, and erythrocytes-were quite different, at that hemolytic effects of the tested compounds were higher than their cytotoxicity against other cells, especially against the ascites of Ehrlich carcinoma. Interestingly, psolusoside G (4) was not cytotoxic against normal JB-6 cells but demonstrated high activity against Neuro 2A cells. The cytotoxic activity against human colorectal adenocarcinoma HT-29 cells and the influence on the colony formation and growth of HT-29 cells of compounds 1-3, 5-7 and psolusoside A was checked. The highest inhibitory activities were demonstrated by psolusosides E (2) and F (3).

Asterosaponins from the tropical starfish Acanthaster planci and their cytotoxic and anticancer activities in vitro

New asterosaponin, acanthaglycoside G (1), along with three previously known steroidal oligoglycosides (2‒4), were isolated from the ethanolic extract of the starfish Acanthaster planci, collected off the coast of Vietnam. The structure of 1 was mainly elucidated by extensive NMR and ESIMS techniques as sodium 6-O-{β-D-fucopyranosyl-(1→2)-β-D-quinovopyranosyl-(1→4)-[β-D-quinovopyranosyl-(1→2)]-β-D-quinovopyranosyl-(1→3)-β-D-quinovopyranosyl}-6α-hydroxy-5α-pregn-9(11)-en-20-one-3β-yl sulfate. Compounds 3 and 4 showed slight cytotoxic activities against cancer RPMI-7951, HT-29, and MDA-MB-231 cell lines, but effectively inhibited in non-toxic concentrations colony formation of HT-29 and MDA-MB-231 cells and cell migration of MDA-MB-231 cells. Compounds 1 and 2 were inactive or less active, respectively.

Laminaran from brown alga Dictyota dichotoma and its sulfated derivative as radioprotectors and radiosensitizers in melanoma therapy

The laminarans are neutral water-soluble β-D-glucans of brown algae possessing potent immunomodulating, radioprotective, and anticancer activities. The aim of the present study was to investigate in vitro anticancer, radioprotective, and radiosensitizing activities of laminaran from brown alga Dictyota dichotoma and its sulfated derivative. The native and sulfated laminarans by themselves at non-toxic doses possessed significant anticancer activity against melanoma cells. Both polysaccharides protected normal epidermal cells, while only sulfated laminaran was able to sensitize melanoma cells to X-rays irradiation resulting in significant inhibition of cell proliferation, colony formation, and migration of cancer cells. The molecular mechanism of this action was related to the inhibition of MMP-2 and MMP-9 proteinases activity as well as down-regulation of kinases' phosphorylation of ERK1/2 signaling cascade. Taken together, the combination of sulfated derivative of laminaran from D. dichotoma with X-ray may serve as a potential treatment strategy for human melanoma.

Radiosensitizing effect of the fucoidan from brown alga Fucus evanescens and its derivative in human cancer cells

Fucoidan from brown alga Fucus evanescens and its product of enzymatic hydrolysis have precisely established structure and possess significant biological activities. The aim of present study was to determine radiosensitizing activity of fucoidan from brown alga F. evanescens and its derivative in human melanoma, breast adenocarcinoma, and colorectal carcinoma cell lines and elucidate mechanism of their action. The fucoidan from F. evanescens and its derivative had a comparable radiosensitizing activity and increased the inhibiting effect of X-ray radiation on proliferation and colony formation of human cancer cells, with significant inhibition of melanoma cells. The molecular mechanism of this action was associated with the induction of apoptosis by activating the initiator and effector caspases, suppressing the expression of the anti-apoptotic protein, and enhancing the fragmentation of DNA. The obtained data confirm the prospects of using fucoidan's derivative in combination with radiation therapy for the improvement of the schemes of cancer therapy.

In Vitro Anticancer and Proapoptotic Activities of Steroidal Glycosides from the Starfish Anthenea aspera

New marine glycoconjugates—the steroidal glycosides designated as anthenosides V–X (1–3)—and the seven previously known anthenosides E (4), G (5), J (6), K (7), S1 (8), S4 (9), and S6 (10) were isolated from the extract of the tropical starfish Anthenea aspera. The structures of 1–3 were elucidated by extensive NMR and ESIMS techniques. Glycoside 1 contains a rare 5α-cholest-8(14)-ene-3α,7β,16α-hydroxysteroidal nucleus. Compounds 2 and 3 were isolated as inseparable mixtures of epimers. All investigated compounds (1–10) at nontoxic concentrations inhibited colony formation of human melanoma RPMI-7951, breast cancer T-47D, and colorectal carcinoma HT-29 cells to a variable degree. The mixture of 6 and 7 possessed significant anticancer activity and induced apoptosis of HT-29 cells. The molecular mechanism of the proapoptotic action of this mixture was shown to be associated with the regulation of anti- and proapoptotic protein expression followed by the activation of initiator and effector caspases.

Modification of native fucoidan from Fucus evanescens by recombinant fucoidanase from marine bacteria Formosa algae

Enzymatic depolymerization of fucoidans attracts many researchers due to the opportunity of obtaining standardized fucoidan fragments. Fucoidanase catalyzes the cleavage of fucoidan from Fucus evanescens (FeF) to form low molecular weight products (LMP) and a polymeric fraction (HMP) with 50.8 kDa molecular weight and more than 50% yield. NMR spectroscopy shows that the HMP fraction has regular structure and consists of a repeating fragment [→3)-α-l-Fucp2,4OSO3--(1 → 4)-α-l-Fucp2,4OSO3--(1 → 4)-α-l-Fucp2OSO3--(1→]n. The anticancer effects of FeF fucoidan and its derivative (HMP) were studied in vitro on colon cancer cells HCT-116, HT-29, and DLD-1. The anticancer activity of the HMP fraction was found to be slightly lower than that of the FeF fucoidan. Research and practical applications of the enzyme include modification of native fucoidans for purposes of regular and easier characterized derivatives acquisition.

Structure and anticancer activity of native and modified polysaccharides from brown alga Dictyota dichotoma

The laminaran DdL and fucoidan DdF were obtained from the brown alga Dictyota dichotoma. DdF was a sulfated (28.9%) and acetylated heteropolysaccharide containing fucose, galactose, mannose and glucose (57.9, 20.4, 12.4 and 9.2mol%, respectively). DdL was a 1,3;1,6-β-d-glucan with the main chain built from 1,3-linked glucose residues and single glucose residue in branches at C6 (one branch on three glucose residues of the main chain). Sulfated (43.7%) laminaran DdLs was obtained from DdL by sulfation. It was determined that sulfates occur at C2, C4 and C6 of glucose residues. The anticancer effect of DdF, DdL, and DdLs (200μg/mL) was studied in vitro on colon cancer cells HCT-116, HT-29, and DLD-1. The effect of polysaccharides (40μg/mL) on colony formation of DLD-1 cancer cells after irradiation (4Gy) was investigated first. All polysaccharides showed a synergistic effect with X-ray irradiation against cancer cells, decreasing the amount and size of cancer cells colonies.

Magnumosides B3, B4 and C3, Mono- and Disulfated Triterpene Tetraosides from the Vietnamese Sea Cucumber Neothyonidium (= Massinium) magnum

Two new monosulfated triterpene glycosides, magnumosides B3 (1) and B4 (2) and one new disulfated triterpene glycoside, magnumoside C3 (3) have been isolated from the tropical Indo-West Pacific sea cucumber Neothynidium (=Massinium) magnum (Phyllophoridae, Dendrochirotida) collected in the Vietnamese shallow waters. The structures of the glycosides were elucidated by 2D NMR spectroscopy and mass-spectrometry. All the isolated glycosides are characterized by the non-holostane type aglycones having 18(16)-lactone and 7(8)-double bond and differing from each other by the side chains structures and the quantity of sulfate groups in the carbohydrate chains. The cytotoxic activity of the compounds 1–3 against mouse spleen lymphocytes and ascite form of mouse Ehrlich carcinoma cells, human colorectal carcinoma DLD-1 as well as their hemolytic effects have been studied. Magnumoside B4 (2) greatly suppressed the colony formation and decreased the size of colonies of DLD-1 cancer cells at non-cytotoxic concentrations. The study on synergism of effects of radiation and compounds 1–3 on proliferation of DLD-1 cells showed that the tested compounds almost equally enhanced antiproliferative effect of radioactive irradiation.

Nine New Triterpene Glycosides, Magnumosides A₁-A₄, B₁, B₂, C₁, C₂ and C₄, from the Vietnamese Sea Cucumber Neothyonidium (=Massinium) magnum: Structures and Activities against Tumor Cells Independently and in Synergy with Radioactive Irradiation

Nine new sulfated triterpene glycosides, magnumosides A₁ (1), A₂ (2), A₃ (3), A₄ (4), B₁ (5), B₂ (6), C₁ (7), C₂ (8) and C₄ (9) as well as a known colochiroside B₂ (10) have been isolated from the tropical Indo-West Pacific sea cucumber Neothynidium (=Massinium) magnum (Phyllophoridae, Dendrochirotida) collected in the Vietnamese shallow waters. The structures of new glycosides were elucidated by 2D NMR spectroscopy and mass-spectrometry. All the isolated new glycosides were characterized by the non-holostane type lanostane aglycones having 18(16)-lactone and 7(8)-double bond and differed from each other by the side chains and carbohydrate moieties structures. Magnumoside A₁ (1) has unprecedented 20(24)-epoxy-group in the aglycone side chain. Magnumosides of the group A (1-4) contained disaccharide monosulfated carbohydrate moieties, of the group B (5, 6)-tetrasaccharide monosulfated carbohydrate moieties and, finally, of the group C (7-9)-tetrasaccharide disulfated carbohydrate moieties. The cytotoxic activities of the compounds 1-9 against mouse spleen lymphocytes, the ascites form of mouse Ehrlich carcinoma cells, human colorectal carcinoma DLD-1 cells as well as their hemolytic effects have been studied. Interestingly, the erythrocytes were more sensitive to the glycosides action than spleenocytes and cancer cells tested. The compounds 3 and 7 significantly inhibited the colony formation and decreased the size of colonies of DLD-1 cancer cells at non-cytotoxic concentrations. Moreover, the synergism of effects of radioactive irradiation and compounds 3 and 7-9 at subtoxic doses on proliferation of DLD-1 cells was demonstrated.

The Inhibitory Activity of Luzonicosides from the Starfish Echinaster luzonicus against Human Melanoma Cells

Malignant melanoma is the most dangerous form of skin cancer, with a rapidly increasing incidence rate. Despite recent advances in melanoma research following the approval of several novel targeted and immuno-therapies, the majority of oncological patients will ultimately perish from the disease. Thus, new effective drugs are still required. Starfish steroid glycosides possess different biological activities, including antitumor activity. The current study focused on the determination of the in vitro inhibitory activity and the mechanism of action of cyclic steroid glycosides isolated from the starfish Echinaster luzonicus-luzonicoside A (LuzA) and luzonicoside D (LuzD)-in human melanoma RPMI-7951 and SK-Mel-28 cell lines. LuzA inhibited proliferation, the formation of colonies, and the migration of SK-Mel-28 cells significantly more than LuzD. Anti-cancer activity has been ascribed to cell cycle regulation and apoptosis induction. The molecular mechanism of action appears to be related to the regulation of the activity of cleaved caspase-3 and poly(ADP-ribose) polymerase (PARP), along with Survivin, Bcl-2, p21 and cyclin D1 level. Overall, our findings support a potential anti-cancer efficacy of luzonicosides A and D on human melanoma cells.

BCKDK of BCAA Catabolism Cross-talking With the MAPK Pathway Promotes Tumorigenesis of Colorectal Cancer

Branched-chain amino acids catabolism plays an important role in human cancers. Colorectal cancer is the third most commonly diagnosed cancer in males and the second in females, and the new global incidence is over 1.2 million cases. The branched-chain α-keto acid dehydrogenase kinase (BCKDK) is a rate-limiting enzyme in branched-chain amino acids catabolism, which plays an important role in many serious human diseases. Here we investigated that abnormal branched-chain amino acids catabolism in colorectal cancer is a result of the disease process, with no role in disease initiation; BCKDK is widely expressed in colorectal cancer patients, and those patients that express higher levels of BCKDK have shorter survival times than those with lower levels; BCKDK promotes cell transformation or colorectal cancer ex vivo or in vivo. Mechanistically, BCKDK promotes colorectal cancer by enhancing the MAPK signaling pathway through direct MEK phosphorylation, rather than by branched-chain amino acids catabolism. And the process above could be inhibited by a BCKDK inhibitor, phenyl butyrate.