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Cytostatic and cytotoxic effects of alkylglycerols (Ecomer)
Abstract
Shark liver oil, with a standardized concentration of alkylglycerols and their methoxyderivates, has been widely used in Scandinavian countries as complementary medicine in the treatment of different forms of cancer. The aim of our study was to verify the hypothesized antiproliferative effect of alkylglycerols in different human cancer cell lines.
The plating efficiency method was used to assay the effect of alkylglycerols on the plating efficiency of human ovarian carcinoma (OVP-10), mammary carcinoma (MCF-7), and prostate cancer (DU-145, PC-3 and PCa-2b) cell lines. Tumor colonies containing more than 20 cells were scored as positive. Flow cytometry was applied to identify necrotic vs. apoptotic mode of cell death. The cells were exposed to Ecomer shark liver oil containing 20% alkylglycerols and 3% methoxyderivates in a dose of 0.1 mg/ml, up to a concentration corresponding to LD-50. Apoptotic and necrotic cells were stained with Anexin V and propidium iodine respectively.
The prostate cells from DU-145, PC-3 and PCa-2B showed a dramatic reduction in the colony number even after relatively small doses of 0.5 and 0.1 mg/ml medium. Flow cytomery showed an increased percentage of apoptotic cells of ovarian and prostate carcinoma, while mammary carcinoma cells showed predominantly necrotic cells after exposure to Ecomer.
The alkylglycerols and their methoxyderivates present in Ecomer shark liver oil showed a clear apoptotic/necrotic effect on human prostate and mammary carcinoma cell lines.
... It was shown that the oral administration of AKG in mice grafted with tumor of Lewis lung carcinoma (3LL) reduced the spread of metastasis and the presence of tumors with von Willebrand factor, the marker of tumor vascular endothelium, thus emphasizing the antiangiogenic effect of AKG (Pedrono et al., 2004). Strong inhibition of tumor growth in three human prostate cancers was observed in in vitro administration of shark liver oil containing 20% of DAGE (Krotkiewski, Przybyszewska, & Janik, 2003). ...
... It was interesting to study the effect of AKG on these cells. PCa-2b after 0.5 and 0.1 mg/ml medium of shark liver oil containing 20% of DAGE (Krotkiewski et al., 2003). ...
1‐O‐alkylglycerols (AKG) are a class of natural ether lipids derived from 1‐O‐alkyl‐2,3‐diacyl‐sn‐glycerols by deacylation. In this study, 1‐O‐alkylglycerol (AKG) composition was investigated in the hepatopancreas lipids of the crab Paralithodes camtschaticus and the liver lipids of the squid Berryteuthis magister and the skate Bathyraja parmifera. One of the principal AKG in marine organisms was 1‐O‐hexadecyl‐sn‐glycerol (AKG 16:0). To assess AKG influence on melanoma, we evaluated the cytotoxicity and antiproliferative actions of natural AKG 16:0 and synthetic 1‐O‐octyl‐sn‐glycerol (AKG 8:0) on three human melanoma cell lines SK‐Mel‐5, SK‐Mel‐28, and RPMI‐7951. Natural AKG 16:0 in concentration up to 20 µM was not toxic to all cell lines. AKG 8:0 showed no toxicity to cells SK‐Mel‐5 and SK‐Mel‐28 in concentrations up to 20 µM but had moderate cytotoxicity to RPMI‐7951 cells with an IC50 of 13 µM. Both investigated substances inhibited the proliferation, formation, and growth of cell colonies of RPMI‐7951.
Practical applications
AKG exhibit a variety of biological activities, including anticancer effects. In this study, the liver lipids of the skate B. parmifera and the hepatopancreas lipids of crab P. camtschaticus were shown to be sources of AKG. Our data showed that AKG can be used to prevent the formation of new colonies of malignant cells in combination therapy against melanoma. The results will be useful for future studies involving marine ether lipids and the examination of their anticancer properties against malignant cells.
... Both natural and synthetic AGEs possess various biological activities; for a review, see [37]. Among others, there are such useful properties as anticancer [2,3,17,18,21,29,[38][39][40][41][42][43][44][45], anti-influenza [46], antibacterial [16,30,47,48], antifungal [49], and antifouling [50] activities found in these metabolites. AGEs have been described to reduce cardiovascular and rheumatoid arthritis risk factors [51], the side effects of radiotherapy [52][53][54], obesity [55][56][57][58], microglial activation, and a neuropathic pain [22,59]. ...
The cytotoxicity-bioassay-guided fractionation of the ethanol extract from the marine sponge Guitarra abbotti, whose 1-O-alkyl-sn-glycerol ethers (AGEs) have not been investigated so far, led to the isolation of a complex lipid fraction containing, along with previously known compounds , six new lipids of the AGE type. The composition of the AGE fraction as well as the structures of 6 new and 22 previously known compounds were established using 1 H and 13 C NMR, GC/MS, and chemical conversion methods. The new AGEs were identified as: 1-O-(Z-docos-15-enyl)-sn-glycerol (1), 1-O-(Z-docos-17-enyl)-sn-glycerol (2), 1-O-(Z-tricos-15-enyl)-sn-glycerol (3), 1-O-(Z-tricos-16-enyl)-sn-glycerol (4), 1-O-(Z-tricos-17-enyl)-sn-glycerol (5), and 1-O-(Z-tetracos-15-enyl)-sn-glycerol (6). The isolated AGEs show weak cytotoxic activity in THP-1, HL-60, HeLa, DLD-1, SNU C4, SK-MEL-28, and MDA-MB-231 human cancer cells. A further cytotoxicity analysis in JB6 P + Cl41 cells bearing mutated MAP kinase genes revealed that ERK2 and JNK1 play a cytopro-tective role in the cellular response to the AGE-induced cytotoxic effects.
... Shark liver oil (SLO) has been applied as a traditional marine natural product by Scandinavian people due to its possible therapeutic effects [11,12]. SLO is rich in alkylglycerols and squalene and also contains n-3 polyunsaturated fatty acids (N-3 PUFA) in lower amounts [13,14]. ...
Ulcerative colitis (UC) is one of the most well-known types of inflammatory bowel disease that manifests as recurrent inflammation of rectum and colon. The goal of this study is to evaluate the protective effects of shark liver oil (SLO) on acetic acid-induced ulcerative colitis in rats. Eighty induced UC rats were randomly divided into ten equal groups and received the following treatments for seven days: 1 ml of normal saline rectally, 1 ml of gel base (carboxymethyl cellulose) rectally, 10 mg/kg of Asacol rectally, 10 mg/kg of mesalazine orally, 5% gel form of SLO rectally, 10% gel form of SLO rectally, 200 mg of SLO orally, and 400 mg of SLO orally. We examined the oxidative stress indices, histopathological features, and body weight changes, as well as the function of the liver and kidneys at the end of treatment. Administration of 10% rectal and 400 mg oral SLO resulted in a significant weight gain. Also, glutathione peroxidase activity was significantly higher in 5% and 10% SLO-treated groups, and elevated superoxide dismutase activity in rats that received 5% SLO was observed compared to negative control and Asacol groups. While no significant changes were observed in most of the kidney and liver function markers, higher levels of aspartate aminotransferase were detected in the group that received 400 mg SLO orally compared to negative control and Asacol groups. Many histopathological signs of improvement were observed in mesalazine, Asacol, and SLO groups. There were no significant changes detected in the mean rank among different groups. Our data indicate that SLO supplementation could improve the amelioration of acetic acid-induced UC in rats due to its antioxidant effects.
... Alkylglycerols inhibit kinase C and cancer promotion. These potent antioxidants protect tissues against the toxic effects of hydroxyl radicals which are generated in large quantities during radiation therapy [61,62]. ...
Introduction and objective:
The anticarcinogenic potential of milk fat can be attributed to its antioxidant, anti-inflammatory, immunostimulatory properties as well as the presence of compounds with antimutagenic effects. In view of the high incidence of cancer the aim of this article was to review the literature concerning the biological activity of milk fat components.
Brief description of the state of knowledge:
Conjugated linoleic acid (CLA), coenzyme Q10, phospholipids, β-carotene, and vitamins A, D and E play an important role in the pro-oxidant/antioxidant homeostasis. The anti-inflammatory properties of milk fat can be attributed to the presence of phospholipids and short- and medium-chain saturated fatty acids. Conjugated linoleic acid has immunostimulatory properties, and it influences the proliferation and activity of lymphocytes and macrophages. Saturated (C10 and C12) and unsaturated (C18) fatty acids, as well as sphingolipids, exert bactericidal effects in the gastrointestinal tract. Vaccenic acid, CLA and sphingomyelin possess antimutagenic and anticarcinogenic properties. Butyric acid promotes the apoptosis of cancer cells in the liver, and delivers positive effects in the treatment of breast and colorectal cancer. Alkylglycerols activate macrophages, stimulate phagocytosis and, most importantly, the apoptosis of cancer cells.
Conclusions:
The health benefits of milk fat are not fully exploited due to its low consumption. Therefore, only some epidemiological studies have shown a negative correlation between the consumption of high-fat dairy products and the incidence of cancer. More research is needed involving human clinical trials to allow a better understanding of the anticancer biochemistry related with milk fat compounds.
... Ecomer® exhibits immune stimulating and anti-tumor activities for which O-18:1 alkylglycerol appears to be the most active component [93]. However, shark liver oil also possesses substantial amounts of methoxy-substituted alkylglycerols that have been suggested to contribute to their anti-tumor activity [94,95]. Despite numerous studies into the therapeutic properties of shark liver oil, the effects on plasmalogen modulation in disease settings remains to be fully characterised. ...
... In another study using the plating efficiency method to assess the effect of AKGs on human ovarian, breast, and prostate carcinoma cell lines, there was a dramatic reduction in prostate cancer cell numbers even at relatively low concentrations of AKGs (0.1 and 0.5 mg/ml). Flow cytometry showed an increase in the percentage of apoptotic ovarian and prostate carcinoma cells, although the breast carcinoma cells became mainly necrotic following exposure to commercially available Ecomer® (Ecomer® SLO containing 20% AKGs and 3% methoxy derivatives at a dose of 0.1 mg/ml) [54]. ...
... Ecomer® exhibits immune stimulating and anti-tumor activities for which O-18:1 alkylglycerol appears to be the most active component [93]. However, shark liver oil also possesses substantial amounts of methoxy-substituted alkylglycerols that have been suggested to contribute to their anti-tumor activity [94,95]. Despite numerous studies into the therapeutic properties of shark liver oil, the effects on plasmalogen modulation in disease settings remains to be fully characterised. ...
Plasmalogens are a class of membrane glycerophospholipids with unique properties. They contain a vinyl-ether linked alkyl chain at the sn-1 position of the glycerol backbone and, typically, a polyunsaturated fatty acyl chain at the sn-2 position. Plasmalogens are critical for human health and have established roles in neuronal development, the immune response and as endogenous antioxidants. However, the mechanistic bases of these and other biological functions of plasmalogens are not well defined. Lipidomic studies have characterised reduced levels of plasmalogens in a number of disease states, including neurodegenerative and cardiometabolic disease, highlighting the potential of plasmalogen modulation as a therapeutic strategy.
A number of approaches have been proposed to upregulate plasmalogen levels in different clinical settings; these include dietary intervention with inositol or the naturally occurring metabolic precursors known as alkylglycerols. Plasmalogen modulation has been utilised in both preclinical and clinical studies to prevent onset and/or attenuate progression of neurodegenerative diseases, atherosclerosis, insulin resistance and hepatosteatosis. These studies are providing new insight into the mechanistic role of plasmalogens in disease and their therapeutic potential.
In this review, we will examine the strategies for plasmalogen modulation and recent progress toward therapeutic applications with a focus on neurodegenerative and cardiometabolic disease.
... AKGs reduced also the major angiogenesis stimulator, basic fibroblast growth factor (bFGF), on endothelial cell proliferation [274] and influenced endothelial cell growth, without showing cytotoxic effects, decreasing the cell proliferation [275]. The antiproliferative effect of AKG was also tested in human mammary carcinoma (MCF7), ovarian carcinoma (OVP10), and prostate cancer (DU45, LnCap) cell lines, showing an increased percentage of apoptotic cells of ovarian and prostate carcinoma and a significant reduction in the number of prostatic cells [276,277]. A methoxy-substituted alkylglycerol inhibited the growth of three human colon cancer cell lines (Moser, HT29, and HCT116) [278]. ...
Objetivos: Estudiar el efecto del 1-O-undecilglicerol sobre la proliferación de células de cáncer de mama MCF-7 y de mama normales 184B5. Métodos: Se realizó seguimiento a tiempo real de la viabilidad de ambas líneas celulares, con empleo del analizador de células en tiempo real. Se determinó la densidad celular apropiada para el estudio, y se trataron las células con dos concentraciones de 1-O-undecilglicerol durante 48 horas. Se compararon las pendientes del índice celular en cada experimento. Resultados: El 1-O-undecilglicerol redujo significativamente la proliferación de las células MCF-7, mientras que fue poco citotóxico sobre las células 184B5 hasta 75µM. A la concentración de 150µM fue citotóxico para ambas líneas, pero invirtió la pendiente del índice celular de las células de cáncer de mama. Conclusiones: El 1-O-undecilglicerol podría ser candidato para futuros estudios en modelos in vivo de cáncer de mama, así como para la profundización en el mecanismo involucrado en este efecto.
Historically, lipids have been considered just as a source of energy for our bodies and as the basic unit of membranes. The discovery of the platelet-activating factor in 1979 as one of the first biologically active phospholipids was a relevant landmark in this field. Since then, some unique biological activities have been assigned to every single lipid class. For example, lipids, as small hydrophobic molecules, are extraordinary as chemical messengers to send information between organelles and to other cells. Additionally, polar lipids that contain hydrophobic and hydrophilic regions can interact distinctly with membrane proteins modulating their activities, while glycosphingolipids including their structure complex carbohydrates can play important roles in the immune system. Therefore, in this chapter, many relevant biological functions of some lipid classes from dietary sources will be extensively reviewed.
The glyceryl ethers were studied in lipids from human bone marrow, spleen, and milk; from yellow bone marrow and milk of cow; and from the yolk of hens' eggs. The highest concentrations were found in human red bone marrow and in human milk. No glyceryl ethers could be demonstrated in red cells or egg yolk. Besides the main components (chimyl, batyl, and selachyl alcohols), several new glyceryl ethers were found. The glyceryl ethers in man and cow were generally much more saturated than those in the liver oils of elasmobranch fish, although a fairly high degree of unsaturation was found in the glyceryl ethers of human milk.
The glyceryl ethers from the liver oils of the grey dogfish, the Greenland shark, and the ratfish were isolated by chromatography on alumina. These ethers were then converted into the corresponding dimethoxy derivatives, which were rechromatographed on alumina and then submitted to gas-liquid chromatography (GLC). By these means the presence of several new glyceryl ethers was demonstrated. Besides chimyl, batyl, and selachyl alcohols, compounds with saturated C14, and monounsaturated C16, C20, and C22 chains were found. Small amounts of a glyceryl ether with a C18 chain with two double bonds were also present. By oxidation with chromic acid, the position of the double bond in the hexadecenyl chain was found to be 9: 10; in the eicosenyl and the docosenyl chains the double bond was in position 13: 14. The molecular weight of the dimethoxy derivatives was determined by mass spectrometry. The mass spectrometric fragmentation pattern provided additional proof of the structure of the compounds.
The ether lipid antineoplastic agents have no known interaction with DNA, but rather they appear to target membranes. The primary mechanism of action is unknown but effects on membrane biology are documented. We have studied the effect of two ether lipids on membrane lipids and examined the hypothesis that membrane peroxidative damage may be involved in their mechanism of action. With the use of cells having membranes enriched in polyunsaturated fatty acids of the omega-3 family of fatty acids, we have demonstrated that the prototypical ether lipid 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine and a thioether lipid analogue, 1-O-hexadecylmercapto-2-methoxymethyl-rac-glycero-3-phosphocholine , increase membrane lipid peroxidation and cytotoxicity in a time- and drug concentration-dependent manner. The oxidative cofactors Fe2+ and ascorbic acid were required. The pattern of cell death did not fully correspond to the peroxidation, since cofactors were required for peroxidation but not cytotoxicity. However, the rate of decrease in cell viability after exposure to the drug and cofactors corresponded to the peroxidation rate. In addition, when L1210 cells modified with the monounsaturated fatty acid oleic acid or unmodified cells were used, there was no ether lipid-enhanced peroxidation, and the cells were significantly less sensitive to the drug, with or without cofactors. The lipid-soluble antioxidant vitamin E inhibited 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine peroxidation and cytotoxicity in a concentration-dependent manner in the presence of cofactors but not consistently without them. Depletion of cellular glutathione content of L1210 cells using L-buthionine-(SR)-sulfoximine resulted in 40% augmentation of cofactor-facilitated cytotoxicity of 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine and a borderline effect on peroxidation. Another ether lipid, the thio compound 1-O-hexadecylmercapto-2-methoxymethyl-rac-glycero-3-phosphocholine , enhanced peroxidation in the presence of cofactors with kinetics corresponding to those of cytotoxicity. In the presence of ether lipid and cofactors the intensity of ascorbate free radical increased, consistent with oxidative stress. We conclude that the ether lipids stimulate membrane lipid peroxidation in a time- and drug concentration-dependent manner in the presence of oxidative cofactors. Even though peroxidation may not fully explain the cytotoxic effect of the ether lipid class of anticancer drugs, this observation provides further information on the nature of the membrane damage induced by the drugs. Since the ether lipids generate no known free radical intermediates directly, this suggests that membrane damage indirectly results in a process involving a peroxidative reaction.
SANDLER1 claimed that the protective factor against benzene poisoning found in yellow bone marrow is batyl alcohol or one of its esters. Since batyl alcohol is found in those organs which are said to contain a humoral factor that protects animals against the acute phase of irradiation injury2, the following experiments were carried out. Sixty adult white male mice of an inbred strain (16 years) were irradiated with a therapeutic X-ray machine, 165 kV., 15 m.amp., filters 0.5 mm. copper + 1 mm. aluminium, target distance 60 cm., irradiation time 25 min., total dose 750 r. (air). Two hours after the end of the irradiation, thirty animals chosen at random were given 0.1 ml. of peanut oil subcutaneously, the others the same volume of peanut oil containing 2.5 mgm. dl-batyl alcohol per ml. These injections were repeated every second day until 1.75 mgm. of dl-batyl alcohol or a corresponding amount of the solvent had been administered to the animals. The 30-day letbality for the animals treated with batyl alcohol was seventeen out of thirty and for the controls twenty-six out of thirty. The difference is statistically significant (P < 0.01).
Alkyl-lysophospholipids are synthetic analogs of natural occurring 2-lysophosphatidylcholine. They inhibit the development of metastasis of 3-Lewis lung tumor in the lung of C57Bl/6 mice if given i.v., i.c. or even orally as demonstrated by the increase of the median survival time and the number of surviving animals. Furthermore, i.v. injections of lysophospholipid-activated bone marrow macrophages increase the number of surviving animals and cause also a prolongation of the median survival time.
Specific non-metabolizable alkyl-phospholipids selectively kill neoplastic cells, yet normal and more differentiated cells are relatively resistant. Although these highly selective anticancer lipids appear to target the cell membrane, their mechanism of cytotoxic action remains to be defined. We report here that treatment of 'sensitive' HL-60 leukemia cells with one of the most potent lipid agents, 1-alkyl-2-methoxy-glycero-3-phosphocholine, inhibits the cellular transport of multiple essential nutrients including choline, amino acids, fatty acids, and the non-metabolizable carbohydrate, 2-deoxy-D-glucose. Minimal inhibitory responses of the varied transport systems were noted in HL-60 cells treated with the less potent, 2-lyso analog, and in 'resistant' K562 leukemia cells, treated with the 2-methoxy lipid. Although both the 2-methoxy lipid and 12-tetradacanoylphorbol 13-acetate induce differentiation in HL-60 cells, significant differences in the interactions of these lipids on cellular choline transport were found. Based on these results, we conclude that multiple nutrient deprivation induced by the detergent-like action of the methoxy-containing alkyl phospholipid results in the selective destruction of neoplastic cells that are sensitive to this membrane-targeted antitumor agent.
This review covers the work of our laboratory on the antineoplastic activity of some ethei lipids and derivatives that are related to platelet-activating factor (PAF). Various 1-O-alkyl lysophospholipid derivatives (ALP) show therapeutic activity in mouse transplant tumor models and in metastatic 3-Lewis lung carcinoma in vivo. However, certain autochthonous mouse leukemias and radiation-induced lymphomas are resistant to ALP treatment. The therapeutic effects of these compounds are partially due to the activation of cytotoxic macrophages and direct cytotoxicity.
Approximately 20 ether lipids and derivatives were tested for direct cytotoxicity in cells from human solid tumors and leukemias using [3H]thymidine uptake, trypan blue dye exclusion, human tumor clonogenic assays (HTCA) and cell morphology as criteria. Certain ALP, thioether lysophospholipid-derivatives (TLP), ether0linked lipoidal amines,sn-2 analogs of PAF, and conjugates of ether lipids and cytosine arabinoside were found cytotoxic in a dose- and time-dependent fashion. Cytotoxicity of some of the ether lipids tested is based on destruction of cell membranes. Structure-activity studies were performed to better understand the mechanisms leading to accumulation and cytotoxicity of ALP. Comparative studies with normal bone marrow cells and leukemic blasts from humans revealed preferential antileukemic cytotoxity of three ether lipids.
A regression of tumor growth is observed when alkoxyglycerols are administered prior to radiation treatment of patients suffering from cancer of the uterine cervix. This regression is remarkably higher for patients below the age of 60 years than for those over 60. The regression has been demonstrated by a change in the quotient between the incidence of early and advanced stages.