In vivo anti-tumour effect of 3'-sulphonoquinovosyl 1'-monoacylglyceride isolated from sea urchin (Strongylocentrotus intermedius) intestine

Chemical synthesis of amphiphilic glycoconjugates: Access to amino, fluorinated and sulfhydryl oleyl glucosides

Amphiphilic glycoconjugates offer an important prospect for development as chemical biology tools and biosurfactants. The chemical synthesis of such materials is required to expedite such prospect, compounded by the example of oleyl glycosides. Herein, we report a mild and reliable glycosylation method to access oleyl glucosides, glycosidating oleyl alcohol with α-trichloroacetimidate donors. We demonstrate capability for this methodology, extending it to synthesise the first examples of pyranose-component fluorination and sulfhydryl modifications within glucosides and glucosamines of oleyl alcohol. These compounds provide an exciting series of tools to explore processes and materials that utilise oleyl glycosides, including as probes for glycosphingolipid metabolism.

Silica-Containing Biomimetic Composites Based on Sea Urchin Skeleton and Polycalcium Organyl Silsesquioxane

The paper presents an original approach to the synthesis of polycalciumorganyl silsesquioxanes through the reaction of polyorganyl silsesquioxanes [RSiO1.5]n (where R is an ethyl and phenyl radical) with sea urchin skeleton under the conditions of mechanochemical activation. The novelty and practical significance of the present study lies in the use of an available natural raw source as a source of calcium ions to initiate the reaction of calcium silicate formation and create a matrix for the formation of a porous inorganic composite framework. The thermal stability of the introduced silicates, i.e., the ability to maintain a porous structure at high temperatures, is key to the production of an ordered porous material. The reaction scheme was proposed to be based on the interaction of calcium carbonate with the siloxane bond. FTIR, XRD, GPC, and TGA were used to study the composition and structure of the obtained materials. The cross-sectional area of the polymer chain and the volumes of the coherent scattering regions of the polymers obtained were calculated from the XRD data. To prepare the composites, the sea urchin skeleton was further modified with polycalciumorganyl silsesquioxanes in a toluene solution. To remove the sea urchin skeleton, the obtained biomimetic composites were treated with hydrochloric acid. The results of the morphological and surface composition studies are reported. The method proposed in the paper could be of fundamental importance for the possibility of obtaining structured porous composite materials for a wide range of practical applications, including for the purpose of creating a composite that may be a promising carrier for targeted delivery of chemotherapy agents.

Anticancer agent α-sulfoquinovosyl-acylpropanediol enhances the radiosensitivity of human malignant mesothelioma in nude mouse models

Malignant pleural mesothelioma (MPM) is a highly malignant disease that develops after asbestos exposure. Although the number of MPM cases is predicted to increase, no effective standard therapies have been established. The novel radiosensitizer α-sulfoquinovosyl-acylpropanediol (SQAP) enhances the effects of γ-radiation in human lung and prostate cancer cell lines and in animal models. In this study, we explored the radiosensitizing effect of SQAP and its mechanisms in MPM. The human MPM cell lines MSTO-211H and MESO-4 were implanted subcutaneously into the backs and thoracic cavities of immunodeficient KSN/Slc mice, then 2 mg/kg SQAP was intravenously administered with or without irradiation with a total body dose of 8 Gy. In both the orthotopic and ectopic xenograft murine models, the combination of irradiation plus SQAP delayed the implanted human MSTO-211H tumor growth. The analysis of the changes in the relative tumor volume of the MSTO-211H indicated a statistically significant difference after 8 Gy total body combined with 2 mg/kg SQAP, compared to both the untreated control (P = 0.0127) and the radiation treatment alone (P = 0.0171). After the treatment in each case, immunostaining of the harvested tumors revealed decreased cell proliferation, increased apoptosis and normalization of tumor blood vessels in the SQAP- and irradiation-treated group. Furthermore, hypoxia-inducible factor (HIF) 1 mRNA and protein expression were decreased, indicating reoxygenation in this group. In conclusion, SQAP improved hypoxic conditions in tumor tissue and may elicit a radiosensitizing effect in malignant mesothelioma models.

The natural sulfoglycolipid derivative SQAP improves the therapeutic efficacy of tissue factor-targeted radioimmunotherapy in the stroma-rich pancreatic cancer model BxPC-3

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SQAP enhanced tumor uptake and the therapeutic efficacy of radiolabeled anti-tissue factor antibody 1849.

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SQAP allows for a reduction of the dose of the therapeutic agent ⁹⁰Y-labeled 1849 to half.

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SQAP did not affect hematologic parameters, or gastrointestinal and respiratory systems in mice.

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⁹⁰Y-labeled 1849 with SQAP potentially increases exposure of tumors to radiation.

α-Sulfoquinovosylacyl-1,3-propanediol (SQAP) is a semi-synthetic derivative of natural sulfoglycolipid that sensitizes tumors to external-beam radiotherapy. How SQAP affects internal radiotherapy, however, is not known. Here, we investigated the effects of SQAP for radioimmunotherapy (RIT) targeting tissue factor (TF) in a stroma-rich refractory pancreatic cancer mouse model, BxPC-3. A low dose of SQAP (2 mg/kg) increased tumor uptake of the ¹¹¹In-labeled anti-TF antibody 1849, indicating increased tumor perfusion. The addition of SQAP enhanced the growth-inhibitory effect of ⁹⁰Y-labeled 1849 without leading to severe body weight changes, allowing for the dose of ⁹⁰Y-labeled 1849 to be reduced to half that when used alone. Histologic analysis revealed few necrotic and apoptotic cells, but Ki-67–positive proliferating cells and increased vascular formation were detected. These results suggest that the addition of a low dose of SQAP may improve the therapeutic efficacy of TF-targeted RIT by increasing tumor perfusion, even for stroma-rich refractory pancreatic cancer.

Characterization of Gangliosides in Three Sea Urchin Species by HILIC-ESI-MS/MS

Sea urchin gangliosides (SU-GLSs) are well acknowledged for their nerve regeneration activity and neuroprotective property. The present study sought to characterize and semi-quantitate different SU-GLS subclasses in three sea urchin species, including Strongylocentrotus nudus, Hemicentrotus pulcherrimus, and Glyptocidaris crenularis. A total of 14 SU-GLS subclasses were identified by a hydrophilic interaction liquid chromatography-Q-Exactive tandem mass spectrometry method. Three sialic acid (Sia) structures, including Neu5Ac, Neu5Gc, and KDN, were identified in SU-GLSs, of which Neu5Ac and Neu5Gc had their corresponding sulfated forms. The linkage among Sias was determined to be 2-8. Additionally, KDN2-6Glc1-1Cer, KDN2-8Neu5Gc2-6Glc1-1Cer, and KDN2-8Neu5Gc2-8Neu5Gc2-6Glc-1Cer were speculated to be novel SU-GLS structures. Furthermore, the total SU-GLS content was 2.0-7.3 mg/g in the three sea urchin species. These results will provide useful data for developing a SU-GLS database of aquatic products. Besides, this study will provide a theoretical basis to explore the nutritional values of seafood products further.

SQAP, an acyl sulfoquinovosyl derivative, suppresses expression of histone deacetylase and induces cell death of cancer cells under hypoxic conditions

Sulfoglycolipid, SQAP, is a radiosensitizing agent that makes tumor cells more sensitive to radiation therapy. A previous study revealed that SQAP induced the degradation of hypoxia-inducible factor-1α (HIF-1α) and inhibited angiogenesis in a hepatoma model mouse. Herein, we examined the biological activities of SQAP against hepatocarcinoma cells under low oxygen conditions. Cell growth inhibition of SQAP under hypoxic conditions was significantly higher than that under normoxic conditions. In addition, SQAP was found to impair the expression of histone deacetylase (HDAC) under low oxygen conditions. Our present data suggested that SQAP induced the degradation of HIF-1α and then decreased the expression of HDAC1. Unlike known HDAC inhibitors, SQAP increased the acetylation level of histone in cells without inhibition of enzymatic activity of HDACs. Our data demonstrated hypoxia-specific unique properties of SQAP.

Induction of Apoptosis by Acanthaster planci sp., and Diadema setosum sp., Fractions in Human Cervical Cancer Cell Line, HeLa

Cancer is an uncontrolled multiplication of cells. The desire efficacy and severe toxicity of current anticancer drugs urge exploring and investigating a better alternative to existing chemotherapeutics. Natural products of marine origin are excellent sources of potential new drugs of enhanced biological activities.

OBJECTIVES

Thus, the cytotoxic effects along with investigating the mode of cell death exerted by fractions, AP-9, AP-THR, DS-8 and DS-9 fraction of Acanthaster planci, Diadema setosum sp., on the human cervical cancer cell line, HeLa.

METHODS

The cytotoxicity of fractions has determined by using an MTS assay. The early and late apoptosis was studied by using the High content Screening (HCS) instrument.

RESULTS

The four fractions produced effective cytotoxicity effects with IC50 values at 72hr of less than 20 μg/ml in the order of AP-9 > DS-9 > APTHR-9 > DS-8. The fraction s exhibited cytotoxicity via mediating apoptotic mode of cell death. The early apoptosis by exposure of phosphatidylserine to the outer leaflet of the plasma membrane and late apoptosis due to the presence of green stain (DNA fragmentation) in treated cells.

CONCLUSION

The potent bioactive compounds might be responsible for inducing apoptosis in cancer cells and, thus, the potential to be a successful candidate for exploring upcoming chemotherapeutic drugs.

The Outcome and CT Findings of Low-Dose Intensity Modulated Radiation Therapy with SQAP in a Cat with Thymoma

A 9-year-old male intact domestic cat weighing 4.6 kg was referred for tachypnea. A large mass was visible in computed tomography (CT) scans of the thoracic cavity. A histopathological evaluation of the mass was consistent with thymoma. The cat was treated with 2 × 8 Gy intensity modulated radiation therapy and sulfoquinovosyl acyl propanediol (SQAP). Post radiation therapy (RT), the tumor structure appeared cystic in the CT, and the tumor volume decreased by approximately 80% after aspiration than that before aspiration. The tumor was removed surgically. RT treatment with SQAP made it possible to treat the thymoma with a low total radiation dose.

A Multimodal Molecular Imaging Study Evaluates Pharmacological Alteration of the Tumor Microenvironment to Improve Radiation Response

: Hypoxic zones in solid tumors contribute to radioresistance, and pharmacologic agents that increase tumor oxygenation prior to radiation, including antiangiogenic drugs, can enhance treatment response to radiotherapy. Although such strategies have been applied, imaging assessments of tumor oxygenation to identify an optimum time window for radiotherapy have not been fully explored. In this study, we investigated the effects of α-sulfoquinovosylacyl-1,3-propanediol (SQAP or CG-0321; a synthetic derivative of an antiangiogenic agent) on the tumor microenvironment in terms of oxygen partial pressure (pO₂), oxyhemoglobin saturation (sO₂), blood perfusion, and microvessel density using electron paramagnetic resonance imaging, photoacoustic imaging, dynamic contrast-enhanced MRI with Gd-DTPA injection, and T2*-weighted imaging with ultrasmall superparamagnetic iron oxide (USPIO) contrast. SCCVII and A549 tumors were grown by injecting tumor cells into the hind legs of mice. Five days of daily radiation (2 Gy) combined with intravenous injection of SQAP (2 mg/kg) 30 minutes prior to irradiation significantly delayed growth of tumor xenografts. Three days of daily treatment improved tumor oxygenation and decreased tumor microvascular density on T2*-weighted images with USPIO, suggesting vascular normalization. Acute effects of SQAP on tumor oxygenation were examined by pO₂, sO₂, and Gd-DTPA contrast-enhanced imaging. SQAP treatment improved perfusion and tumor pO₂ (ΔpO₂: 3.1 ± 1.0 mmHg) and was accompanied by decreased sO₂ (20%-30% decrease) in SCCVII implants 20-30 minutes after SQAP administration. These results provide evidence that SQAP transiently enhanced tumor oxygenation by facilitating oxygen dissociation from oxyhemoglobin and improving tumor perfusion. Therefore, SQAP-mediated sensitization to radiation in vivo can be attributed to increased tumor oxygenation. SIGNIFICANCE: A multimodal molecular imaging study evaluates pharmacological alteration of the tumor microenvironment to improve radiation response.

Modulation of Telomerase Activity in Cancer Cells by Dietary Compounds: A Review

Telomerase is expressed in ~90% of human cancer cell lines and tumor specimens, whereas its enzymatic activity is not detectable in most human somatic cells, suggesting that telomerase represents a highly attractive target for selective cancer treatment. Accordingly, various classes of telomerase inhibitors have been screened and developed in recent years. We and other researchers have successfully found that some dietary compounds can modulate telomerase activity in cancer cells. Telomerase inhibitors derived from food are subdivided into two groups: one group directly blocks the enzymatic activity of telomerase (e.g., catechin and sulfoquinovosyldiacylglycerol), and the other downregulates the expression of human telomerase reverse transcriptase (hTERT), the catalytic subunit of human telomerase, via signal transduction pathways (e.g., retinoic acid and tocotrienol). In contrast, a few dietary components, including genistein and glycated lipid, induce cellular telomerase activity in several types of cancer cells, suggesting that they may be involved in tumor progression. This review summarizes the current knowledge about the effects of dietary factors on telomerase regulation in cancer cells and discusses their molecular mechanisms of action.

Amphiphilic glycoconjugates as potential anti-cancer chemotherapeutics

Amphiphilicity is one of the desirable features in the process of drug development which improves the biological as well as the pharmacokinetics profile of bioactive molecule. Carbohydrate moieties present in anti-cancer natural products and synthetic molecules influence the amphiphilicity and hence their bioactivity. This review focuses on natural and synthetic amphiphilic anti-cancer glycoconjugates. Different classes of molecules with varying degree of amphiphilicity are covered with discussions on their structure-activity relationship and mechanism of action.

Chemical Synthesis of Marine-Derived Sulfoglycolipids, a New Class of Molecular Adjuvants

Vaccines play a primary role in the protection of human health by preventing infectious and chronic diseases. Recently we have reported 1,2-O-distearoyl-3-O-β-d-sulfoquinovosylglycerol (β-SQDG18), here named Sulfavant A (1), which shows promising properties as a new molecular adjuvant in in vitro and in vivo tests. In the present manuscript, we provide full details about a synthetic strategy for the preparation of 1, including a discussion of chemical determinants of the activity and the major technical hurdles we faced during the study. Synthesis of Sulfavant A (1) is achieved by a versatile procedure based on a trichloroacetimidate methodology and peracetate sugar precursors. The final design opens possibilities for the preparation of a series of interesting analogs for further pharmacological optimization and development, including derivatives containing different saturated and polyunsaturated fatty acids (e.g., 17 and 22).

A polysaccharide component from Strongylocentrotus nudus eggs inhibited hepatocellular carcinoma in mice by activating T lymphocytes

A component purified from Strongylocentrotus nudus eggs on a diethylaminoethyl cellulose-52 chromatography column and eluted using a NaCl solution gradient (SEP-S), is a homogeneous polysaccharide of α-D-glucan with a reduced molecular weight of 9.33×10⁵ Da, compared with that of S. nudus egg polysaccharide (SEP). In an in vivo antitumor assay of histocompatibility-22 hepatocellular carcinoma in tumor-bearing mice, the inhibitory rates at SEP-S doses of 5, 10 and 20 mg/kg/day were 38.8, 50.7 and 70.3%, respectively. In addition, the spleen and thymus indices and the percentages of cluster of differentiation (CD) 4⁺ and CD8⁺ T cells were significantly increased, and the activity of cytotoxic T lymphocytes was notably enhanced, suggesting that the anti-hepatocellular carcinoma activity is mediated by boosting the immune system. In vitro experiments also demonstrated that splenocyte proliferation induced by SEP-S was inhibited by the toll-like receptor (TLR) 2 and TLR4 monoclonal antibodies. These data indicate that SEP-S is a polysaccharide component possessing high anti-hepatocellular carcinoma activity and may be a potential immunotherapy candidate for the treatment of liver cancer.

Glycolipids synthesis: improved hydrazinolysis conditions for preparation of 1,2-polyunsaturated fatty acyl-β-monogalactosyl-glycerols

The investigation is related to the development of a general strategy for the synthesis of glycolipids including analogs bearing polyunsaturated fatty acids. In particular, here we report exceptionally mild and selective conditions to remove acetate protecting groups from glyceroglycolipids by hydrazinolysis. Synthetic 1,2-O-di-arachidonoyl-3-O-β-galactosyl-glycerol was used as representative of polyunsaturated β-galactosyl-di-acyl-glycerols due to its reactivity under the conditions usually employed in literature.

Inhibition of hypoxia-inducible factor via upregulation of von Hippel-Lindau protein induces "angiogenic switch off" in a hepatoma mouse model

“Angiogenic switch off” is one of the ideal therapeutic concepts in the treatment of cancer. However, the specific molecules which can induce “angiogenic switch off” in tumor have not been identified yet. In this study, we focused on von Hippel-Lindau protein (pVHL) in hepatocellular carcinoma (HCC) and investigated the effects of sulfoquinovosyl-acylpropanediol (SQAP), a novel synthetic sulfoglycolipid, for HCC. We examined mutation ratio of VHL gene in HCC using 30 HCC samples and we treated the HCC-implanted mice with SQAP. Thirty clinical samples showed no VHL genetic mutation in HCC. SQAP significantly inhibited tumor growth by inhibiting angiogenesis in a hepatoma mouse model. SQAP induced tumor “angiogenic switch off” by decreasing hypoxia-inducible factor (HIF)-1, 2α protein via pVHL upregulation. pVHL upregulation decreased HIFα protein levels through different multiple mechanisms: (i) increasing pVHL-dependent HIFα protein degradation; (ii) decreasing HIFα synthesis with decrease of NF-κB expression; and (iii) decrease of tumor hypoxia by vascular normalization. We confirmed these antitumor effects of SQAP by the loss-of-function experiments. We found that SQAP directly bound to and inhibited transglutaminase 2. This study provides evidence that upregulation of tumor pVHL is a promising target, which can induce “angiogenic switch off” in HCC.

Novel anticancer agent, SQAP, binds to focal adhesion kinase and modulates its activity

SQAP is a novel and promising anticancer agent that was obtained by structural modifications from a natural compound. SQAP inhibits angiogenesis in vivo resulting in increased hypoxia and reduced tumor volume. In this study, the mechanism by which SQAP modifies the tumor microenvironment was revealed through the application of a T7 phage display screening. This approach identified five SQAP-binding proteins including sterol carrier protein 2, multifunctional enzyme type 2, proteasomal ubiquitin receptor, UV excision repair protein and focal adhesion kinase (FAK). All the interactions were confirmed by surface plasmon resonance analysis. Since FAK plays an important role in cell turnover and angiogenesis, the influence of SQAP on FAK was the principal goal of this study. SQAP decreased FAK phosphorylation and cell migration in human umbilical vein endothelial cells and A549 cancer cells. These findings suggest that inhibition of FAK phosphorylation works as the mechanism for the anti-angiogenesis activity of SQAP.

Total synthesis and structure-activity relationship of glycoglycerolipids from marine organisms

Glycoglycerolipids occur widely in natural products, especially in the marine species. Glycoglycerolipids have been shown to possess a variety of bioactivities. This paper will review the different methodologies and strategies for the synthesis of biological glycoglycerolipids and their analogs for bioactivity assay. In addition, the bioactivities and structure-activity relationship of the glycoglycerolipids are also briefly outlined.

Anti-angiogenesis effect of 3'-sulfoquinovosyl-1'-monoacylglycerol via upregulation of thrombospondin 1

We previously reported that 3'-sulfoquinovosyl-1'-monoacylglycerol (SQMG) effectively suppresses the growth of solid tumors, likely via its anti-angiogenic activity. To investigate how SQMG affects angiogenesis, we performed DNA microarray analysis and quantitative real-time polymerase chain reaction. Consequently, upregulation of thrombospondin 1 (TSP-1) in SQMG-treated tumors in vitro and in vivo was confirmed. To address the mechanisms of TSP-1 upregulation by SQMG, we established stable TSP-1-knockdown transformants (TSP1-KT) by short hairpin RNA induction and performed reporter assay and in vivo assessment of anti-tumor assay. On the reporter assay, transcriptional upregulation of TSP-1 in TSP1-KT could not be induced by SQMG, thus suggesting that TSP-1 upregulation by SQMG occurred via TSP-1 molecule. In addition, growth of TSP1-KT xenografted tumors in vivo was not inhibited by SQMG, thus suggesting that anti-angiogenesis via TSP-1 upregulation induced by SQMG did not occur, as the SQMG target molecule TSP-1 was knocked down in TSP1-KT transformants. These data provide that SQMG is a promising candidate for the treatment of tumor-induced angiogenesis via TSP-1 upregulation.

Synthetic Strategy for the Preparation of Bioactive Galactoglycerolipids

The current communication represents an extended abstract of the presentation delivered on the joint Moldo-Italian seminar “New frontiers in natural product chemistry”, held in the Institute of Chemistry, Academy of Sciences of Moldova on 30 September. A simple and efficient strategy for the synthesis of galactoglycerolipids is provided.

Downregulation of Tie2 gene by a novel antitumor sulfolipid, 3'-sulfoquinovosyl-1'-monoacylglycerol, targeting angiogenesis

We previously reported that 3'-sulfoquinovosyl-1'-monoacylglycerol (SQMG) was effective in suppressing the growth of solid tumors due to hemorrhagic necrosis in vivo. In the present study, we investigated the antiangiogenic effect of SQMG. In vivo assessment of antitumor assays showed that some tumor cell lines, but not others, were sensitive to SQMG. Microscopic study suggested that in SQMG-sensitive tumors, but not SQMG-resistant tumors, angiogenesis was reduced. We next investigated gene expression relating to angiogenesis in tumor tissues by quantitative real-time polymerase chain reaction. Consequently, although vascular endothelial growth factor gene expression was not detected with significant differences among the cases, significant downregulation of Tie2 gene expression was observed in all SQMG-sensitive tumors as compared with controls, but not in SQMG-resistant tumors. These data suggested that the antitumor effects of SQMG could be attributed to antiangiogenic effects, possibly via the downregulation of Tie2 gene expression in SQMG-sensitive tumors.

Clinicopathological and biological significance of mitotic centromere-associated kinesin overexpression in human gastric cancer

Mitotic centromere-associated kinesin (MCAK) is a microtubule (MT) depolymerase necessary for ensuring proper kinetochore MT attachment during spindle formation. To determine MCAK expression status and its clinicopathological significance, real-time reverse transcriptase–polymerase chain reaction was used in 65 cases of gastric cancer. MCAK gene expression in cancer tissue was significantly higher than expression in non-malignant tissue (P<0.05). Elevated MCAK expression was significantly associated with lymphatic invasion (P=0.01) and lymph node metastasis (P=0.04). Furthermore, patients with high MCAK expression had a significantly poorer survival rate than those with low MCAK expression (P=0.008). Immunohistochemical study revealed that expression of MCAK was primarily observed in cancer cells. Additionally, a gastric cancer cell line (AZ521) that stably expressed MCAK was established and used to investigate the biological effects of the MCAK gene. In vitro results showed that cells transfected with MCAK had a high rate of proliferation (P<0.001) and increased migratory ability (P<0.001) compared to mock-transfected cells. This study demonstrated that elevated expression of MCAK may be associated with lymphatic invasion, lymph node metastasis, and poor prognosis. These characteristics may be due in part to the increased proliferative and migratory ability of cells expressing MCAK.

Sulfoglycolipids as candidate antiangiogenic radiosensitizers

Angiogenesis is considered an essential process for the growth of solid tumors and, accordingly, angiogenesis has been a focus of attention for cancer therapy. Although various antiangiogenic agents have been developed, adverse effects and limitations associated with antitumor therapies have recently become apparent. To overcome these problems, combining such agents with chemotherapy or radiotherapy is now strongly recommended in clinical practice. Provided such combination treatment, from the onset of therapy, different strategies in developing antiangiogenic agents should be used to enhance any combinatory effects and reduce adverse effects. By applying the concept of radiosensitizers, a new class of antiangiogenic treatments should now be possible. We recently developed sulfoglycolipids that possess such properties. In this review, we discuss the properties of antiangiogenic radiosensitizers and their potential usefulness.

α-Sulfoquinovosylmonoacylglycerol Is a Novel Potent Radiosensitizer Targeting Tumor Angiogenesis

Angiogenesis is a promising target for the treatment of cancer, and varying types of antiangiogenic agents have been developed. However, limitations and problems associated with antiangiogenic therapy have recently arisen. Although radiotherapy can be combined with antiangiogenic compounds to overcome these difficulties, almost all previously described angiogenesis inhibitors could still cause side effects at effective doses, and only additive effects are seen in current combination therapy. In this study, we identified a member of the sulfoquinovosylacylglycerols, alpha-sulfoquinovosylmonoacylglycerol (alpha-SQMG), originally derived from sea urchins, as a potent radiosensitizer. The agent synergistically inhibits angiogenesis at low doses when combined with ionizing radiation. Combined treatment with alpha-SQMG and radiation seems to promote the adoption of a senescence-like phenotype by vascular endothelial cells. Finally, the agent remarkably enhances the radioresponse of human tumors transplanted into nude mice, accompanied by a significant reduction in the vascularity of the tumors. Collectively, alpha-SQMG may be a novel potent radiosensitizer targeting angiogenesis.

Selective in vivo anti-inflammatory action of the galactolipid monogalactosyldiacylglycerol

The thermophilic blue-green alga ETS-05 colonises the therapeutic thermal muds of Abano and Montegrotto, Italy. Following the isolation, purification and identification of monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulphoquinovosyldiacylglycerol (SQDG) and phosphatidylglycerol from ETS-05, we here examine their in vivo anti-inflammatory activities. MGDG, DGDG and SQDG inhibit croton-oil-induced ear oedema in the mouse in a dose-dependent manner. Inhibition by MGDG is greater than that of the reference drug, betamethasone 17,21-dipropionate, and is largely abrogated following acyl group saturation. SQDG is the least potent of these glycoglycerolipids, and shows an early transient effect. In the in vivo carrageenan-induced paw oedema model in the mouse, the inhibitory effects are again dose dependent, with an enhanced efficacy of MGDG over DGDG, SQDG and the reference drug, indomethacin. These compounds are all less toxic than indomethacin. The selective and enhanced inhibitory effects of MGDG over DGDG indicate the mechanisms behind these in vivo anti-inflammatory actions.

Structural analysis of isosteviol and related compounds as DNA polymerase and DNA topoisomerase inhibitors

Isosteviol (ent-16-ketobeyeran-19-oic acid) is a hydrolysis product of stevioside, which is a natural sweetener produced in the leaves of Stevia rebaudiana (Bertoni) Bertoni. In this report, we prepared isosteviol and related compounds from stevioside by microbial transformation and chemical conversion and assayed the inhibitory activities toward DNA metabolic enzymes and human cancer cell growth. Among twelve compounds obtained, only isosteviol (compound 3) potently inhibited both mammalian DNA polymerases (pols) and human DNA topoisomerase II (topo II), and IC50 value for pol alpha was 64.0 microM. This compound had no inhibitory effect on higher plant (cauliflower) pols, prokaryotic pols, human topo I, and DNA metabolic enzymes such as human telomerase, T7 RNA polymerase, and bovine deoxyribonuclease I. With pol alpha, isosteviol acted non-competitively with the DNA template-primer and nucleotide substrate. Isosteviol prevented the growth of human cancer cells, with LD50 values of 84-167 microM, and 500 microg of the compound caused a marked reduction in TPA (12-O-tetradecanoylphorbol-13-acetate)-induced inflammation (inhibitory effect, 53.0%). The relationship between the structure of stevioside-based compounds and these activities were discussed.

Sulfoquinovosylmonoacylglycerol inhibitory mode analysis of rat DNA polymerase beta

We have previously reported that sulfoquinovosylmonoacylglycerol (SQMG) is a potent inhibitor of mammalian DNA polymerases. DNA polymerase beta (pol beta) is one of the most important enzymes protecting the cell against DNA damage by base excision repair. In this study, we characterized the inhibitory action of SQMG against rat pol beta. SQMG competed with both the substrate and the template-primer for binding to pol beta. A gel mobility shift assay and a polymerase activity assay showed that SQMG competed with DNA for a binding site on the N-terminal 8-kDa domain of pol beta, subsequently inhibiting its catalytic activity. Fragments of SQMG such as sulfoquinovosylglycerol (SQG) and fatty acid (myristoleic acid, MA) weakly inhibited pol beta activity and the inhibitory effect of a mixture of SQG and MA was stronger than that of SQG or MA. To characterize this inhibition more precisely, we attempted to identify the interaction interface between SQMG and the 8-kDa domain by NMR chemical shift mapping. Firstly, we determined the binding site on a fragment of SQMG, the SQG moiety. We observed chemical shift changes primarily at two sites, the residues comprising the C-terminus of helix-1 and the N-terminus of helix-2, and residues in helix-4. Finally, based on our present results and our previously reported study of the interaction interface of fatty acids, we constructed two three-dimensional models of a complex between the 8-kDa domain and SQMG and evaluated them by the mutational analysis. The models show a SQMG interaction interface that is consistent with the data.

Effects of DNA polymerase inhibitory and antitumor activities of lipase-hydrolyzed glycolipid fractions from spinach

We succeeded in purifying the major glycolipid fraction in the class of sulfoquinovosyl diacylglycerol, monogalactosyl diacylglycerol and digalactosyl diacylglycerol (DGDG) from a green vegetable, spinach (Spinacia oleracea L.). This glycolipid fraction was an inhibitor of DNA polymerases and a growth inhibitor of NUGC-3 human gastric cancer cells, and, interestingly, the activities were much stronger when the fraction was hydrolyzed by lipase. Glycolipids in the hydrolyzed fraction consisted of sulfoquinovosyl monoacylglycerol (SQMG), monogalactosyl monoacylglycerol (MGMG) and DGDG. In the in vivo antitumor assay using Greene's melanoma, the fraction containing SQMG, MGMG and DGDG showed to be a promising suppressor of solid tumors. Spinach glycolipid fraction might be a potent antitumor compound if directly injected into a tumor-carrying body, and this fraction may be a healthy food material that has antitumor activity.

Inhibition of CD62L+ T-cell response in vitro via a novel sulfo-glycolipid, beta-SQAG9 liposome that binds to CD62L molecule on the cell surface

We previously reported that synthetic sulfo-glycolipid, 3-O-(6-deoxy-6-sulfono-beta-D-glucopyranosyl)-1,2-di-O-acylglycerol (beta-SQDG(18:0)) which was deduced from sulfonoquinovosyl-diacylglycerols of sea urchin possessed immunosuppressive effects, such as human mixed lymphocyte reaction (MLR) and skin allograft in rat, and that these effects were caused by contact inhibition between T-cells and antigen presenting cells (APCs). Here, we investigated the mechanism of these immunosuppressive effects on human MLR by beta-SQAG9 which had been newly synthesized from beta-SQDG(18:0) to improve structural stability in water solution. CD62L+ T-cells in peripheral blood predominantly respond to APCs, and beta-SQAG9 inhibited the response of CD62L+ T-cell subset in human allogeneic MLR. Surprisingly, it was demonstrated that beta-SQAG9 bound to L- and P-selectin (CD62L and P) molecule in vitro. Meanwhile, beta-SQAG9 efficiently formed liposome structure and bound to L-selectin on the cell surface of CD62L+ T-cell subset but might not be incorporated into the cells. Because the immunosuppressive effects of beta-SQAG9 disappeared when beta-SQAG9 liposome was changed to soluble form by detergent, the liposome structure of beta-SQAG9 was presumed to be essential for these effects. These findings suggested beta-SQAG9 to be a novel drug with a unique immunosuppressive action.

Mammalian mitotic centromere-associated kinesin (MCAK)

Sulfoquinovosylacylglycerols (SQAGs), in particular compounds with C18 fatty acid(s) on the glycerol moiety, may be clinically promising antitumor and/or immunosuppressive agents. They were found originally as inhibitors of mammalian DNA polymerases. However, SQAGs can arrest cultured mammalian cells not only at S phase but also at M phase, suggesting they have several molecular targets. A screen for candidate target molecules using a T7 phage display method identified an amino acid sequence. An homology search showed this to be a mammalian mitotic centromere-associated kinesin (MCAK), rather than a DNA polymerase. Analyses showed SQAGs bound to recombinant MCAK with a K(D)=3.1x10(-4) to 6.2x10-5 M. An in vivo microtubule depolymerization assay, using EGFP-full length MCAK fusion constructs, indicated inhibition of the microtubule depolymerization activity of MCAK. From these results, we conclude that clinically promising SQAGs have at least two different molecular targets, DNA polymerases and MCAK. It should be stressed that inhibitors of MCAK have never been reported previously so that there is a major potential for clinical utility.

Monolayer membranes and bilayer vesicles characterized by α- and β-anomer of sulfoquinovosyldiacyglycerol (SQDG)

Physicochemical properties of 1,2-di-O-stearoyl-3-O-(6-deoxy-6-sulfo-alpha-D-glucopyranosyl)-sn-glycerol (alpha-SQDG-C(18:0)) and 1,2-di-O-stearoyl-3-O-(6-deoxy-6-sulfo-beta-D-glucopyranosyl)-sn-glycerol (beta-SQDG-C(18:0)) in monolayer and bilayer membranes were examined. Surface pressure measurements in monolayer membranes indicated the molecular area of beta-SQDG-C(18:0) to be slightly smaller than that of alpha-SQDG-C(18:0). In bilayer membranes, the phase transition temperature and the enthalpy of beta-SQDG-C(18:0) were higher than those of alpha-SQDG-C(18:0), while the trapping efficiency of beta-SQDG-C(18:0) vesicles was lower. The results suggested tighter packing with beta-SQDG-C(18:0) than alpha-SQDG-C(18:0), due to differences in the head group stereochemistry. High-performance liquid chromatography-electrospray ionization ion trap mass spectrometry (HPLC-ESI-MS) data and computational modeling studies provided supporting evidence for morphological differences. In both monolayer and bilayer membranes, the affinity of beta-SQDG-C(18:0) with cholesterol was greater than that of alpha-SQDG-C(18:0), again due to the differences in head group properties. Turbidity measurement and microscopic examination of alpha- and beta-SQDG-C(18:0)/cholesterol mixtures confirmed formation of large vesicles. The addition of cholesterol to SQDG-C(18:0) optimized membrane formation and stabilized its structure.

Cell adhesion and communication: a lesson from echinoderm embryos for the exploitation of new therapeutic tools

In this chapter, we summarise fundamental findings concerning echinoderms as well as research interests on this phylum for biomedical and evolutionary studies. We discuss how current knowledge of echinoderm biology, in particular of the sea urchin system, can shed light on the understanding of important biological phenomena and in dissecting them at the molecular level. The general principles of sea urchin embryo development are summarised, mainly focusing on cell communication and interactions, with particular attention to the cell-extracellular matrix and cell-cell adhesion molecules and related proteins. Our purpose is not to review all the work done over the years in the field of cellular interaction in echinoderms. On the contrary, we will rather focus on a few arguments in an effort to re-examine some ideas and concepts, with the aim of promoting discussion in this rapidly growing field and opening new routes for research on innovative therapeutic tools.

Design of vesicles of 1,2-di-O-acyl-3-O-(β-d-sulfoquinovosyl)-glyceride bearing two stearic acids (β-SQDG-C18), a novel immunosuppressive drug

The immunosuppressive effects of synthetic sulfo-glycolipids in the class of sulfoquinovosyl-diacylglycerols (SQDG), including stereoisomers, were interesting in development of a promising clinical drug. Especially, 1,2-di-O-stearoyl-3-O-(6-deoxy-6-sulfo-beta-D-glucopyranosyl)-sn-glycerol (beta-SQDG-C18) was thought to be a valuable candidate because of the preliminary observations of its high inhibitory activities in spite of low toxicities. The problem of using this material is to find an applicable way avoiding its low solubility in water. The vesicle formation of beta-SQDG-C18 is advantageous to i.v. administration in its chemico-structural character. With preparation in water, beta-SQDG-C18 was hard to form vesicles, because its hydrophilicity was strong. We examined the suitable parameter of the vesicle forming condition. It was possible to take a balance between the hydrophilicity and the hydrophobicity of the beta-SQDG-C18 molecule to be optimized to form vesicles in 150 mM PBS. In addition, we demonstrated the strong immunosuppressive activity of beta-SQDG-C18 vesicles. This is the first report of the preparation method of beta-SQDG-C18 vesicles, which should facilitate in vitro and in vivo application.

Synthetic sulfonolipids deduced from sulfonoquinovosyl diacylglycerols of sea urchin reduces hepatic ischemia-reperfusion injury in rats

BACKGROUND

In hepatic surgery and liver transplantation, ischemia-reperfusion (I/R) is an unavoidable process, and protection against hepatic I/R injury is a major unresolved problem. In this study, we investigated whether 3-O-(6-deoxy-6-sulfono-beta-D-glucopyranosyl)-1,2-di-O-acylglycerol bound to saturated C18 fatty acids (beta-SQAG9), which was derived from sea urchin intestines, could reduce this injury. This agent was recently reported to have immunosuppressive effects in allogeneic rat skin grafts.

MATERIALS & METHODS

Male Lewis rats were divided into two experimental groups. Group 1 rats were injected with SQAG9 (50 mg/kg) into the penile vein 15 minutes before the induction of ischemia and into the portal vein just reperfusion. The same amounts of normal saline were injected into rats in the control group (group 2). Each experimental groups included six rats. Seventy percent hepatic ischemia (20 minutes) was induced by occluding the blood vessels and bile duct with a vascular clamp. For examination of hepatic function, serum levels of aspartate aminotransferase, (AST) alanine transaminase (ALT), and lactic dehydrogenase (LDH) were measured. In addition, histological examination was also assessed.

RESULTS

Three hours after reperfusion, the mean plasma concentration of AST, ALT, LDH in group 1 was suppressed compared with group 2. Six hours after reperfusion, the hepatic damage in group 1 was mild in comparison with that in group 2.

CONCLUSIONS

Our data demonstrated that SQAG-9 reduced the warm hepatic I/R injury.

Synthesis of an immunosuppressant SQAG9 and determination of the binding peptide by T7 phage display

SQAG9, a new class of immunosuppressive sulfoquinovosylacylglycerol, and its biotinylated derivatives have been synthesized. A T7 Phage library, composed of random cDNA fragments from Drosophila melanogaster, displayed a possible binding peptide of 14 amino acids. The immobilized synthetic peptide on a sensor chip showed a dissociation constant of K(D)=1.5 x 10(-6) against SQAG9 in a surface plasmon resonance experiment.

Telomerase inhibition by sulfoquinovosyldiacylglycerol from edible purple laver (Porphyra yezoensis)

As high telomerase activity is detected in most cancer cells, telomerase represents a promising cancer therapeutic target. We investigated the inhibitory effect of sulfoquinovosyldiacylglycerol (SQDG), distributed in plants and seaweeds, on human telomerase in a cell-free system. SQDG inhibited telomerase activity dose-dependently with 50% inhibition at 22 microM, whereas monogalactosyldiacylglycerol and digalactosyldiacylglycerol did not, even at concentrations of 100 microM. Moreover, we confirmed that eicosapentaenoic acid, one of the fatty acid components of SQDG, is a potent telomerase inhibitor with 50% inhibition at 19 microM. We speculate that the structure of the sulfate group and fatty acid of SQDG is important for the potent telomerase-inhibitory effect. Our findings suggest that SQDG has potential use as a therapeutic dietary compound for telomerase inhibition.

Mechanism of cell cycle arrest by sulfoquinovosyl monoacylglycerol with a C18-saturated fatty acid (C18-SQMG)

We have screened the inhibitors of mammalian DNA polymerases from natural products, and in the process found that either sulfoglycolipids or sulfoquinovosyl monoacylglycerol with a C18-saturated fatty acid (C18-SQMG), potently and selectively inhibited the activity of mammalian DNA polymerase (pol) and moderately the pol alpha. C18-SQMG was a cancer cell growth suppressor and a promissive anti-tumor agent. The purpose of this study was to elucidate the cell growth inhibition mechanism of C18-SQMG using HeLa cells. Analyses of the cell cycle and cyclin expression suggested that C18-SQMG arrested the cell cycle at intra-S phase, and the inhibition manner of DNA replication by C18-SQMG was similar to that by hydroxyurea. However, the DNA replication block by C18-SQMG did not induce degradation of Cdc25A protein, which was required for the replication block by hydroxyurea. C18-SQMG somewhat delayed mitosis because it induced phosphorylation of protein kinases, such as checkpoint kinases 1 and 2. These results suggest that C18-SQMG at first blocked DNA replication at the S phase by inhibiting replicative DNA polymerases, such as alpha, and then as the result of the inhibition, the other checkpoint signals associated with the pol might have responded.

A novel DNA topoisomerase inhibitor: dehydroebriconic acid, one of the lanostane-type triterpene acids from Poria cocos

Traditional Chinese medicinal plants are a treasure house for screening novel inhibitors of DNA polymerases and DNA topoisomerases from mammals; in the present study, nine lanostane-type triterpene acids were found in sclerotium of Poria cocos. Among the nine compounds, only dehydroebriconic acid could potently inhibit DNA topoisomerase II (topo II) activity (IC(50) = 4.6 microM), while the compound moderately inhibited the activities of DNA polymerases alpha, beta, gamma, delta, epsilon, eta, iota, kappa and lambda only from mammals, to similar extents. Another compound, dehydrotrametenonic acid, also showed moderate inhibitory effects against topo II (IC(50) = 37.5 microM) and weak effects against all the polymerases tested. Both compounds showed no inhibitory effect against topo I, higher plant (cauliflower) DNA polymerase I (alpha-like polymerase) or II (beta-like polymerase), calf thymus terminal deoxynucleotidyl transferase, human immunodeficiency virus type-1 reverse transcriptase, prokaryotic DNA polymerases such as the Klenow fragment of E. coli DNA polymerase I, Taq DNA polymerase and T4 DNA polymerase, or DNA metabolic enzymes such as T 7 RNA polymerase, T4 polynucleotide kinase and bovine deoxyribonuclease I. These findings suggest that dehydroebriconic acid and dehydrotrametenonic acid should be designated as topo II-preferential inhibitors, although they also moderately inhibited all the mammalian DNA polymerases tested. Both dehydrotrametenonic acid and dehydroebriconic acid could prevent the growth of human gastric cancer cells, and their LD(50) values were 63.6 and 38.4 microM, respectively. The cells were halted at the G1 phase in the cell cycle. The relation between the structure of triterpene acids and their inhibitory activities is discussed.