Effect of selenium on malignant tumor cells of brain

Comparison of Elemental Anomalies Following Implantation of Different Cell Lines of Glioblastoma Multiforme in the Rat Brain: A Total Reflection X-ray Fluorescence Spectroscopy Study

Glioblastoma multiforme (GBM) is a primary brain tumor with a very high degree of malignancy and is classified by WHO as a glioma IV. At present, the treatment of patients suffering from GBM is based on surgical resection of the tumor with maximal protection of surrounding tissues followed by radio- and pharmacological therapy using temozolomide as the most frequently recommended drug. This strategy, however, does not guarantee success and has devastating consequences. Testing of new substances or therapies having potential in the treatment of GBM as well as detection of their side effects cannot be done on humans. Animal models of the disease are usually used for these purposes, and one possibility is the implantation of human tumor cells into rodent brains. Such a solution was used in the present study the purpose of which was comparison of elemental anomalies appearing in the brain as a result of implantation of different glioblastoma cell lines. These were two commercially available cell lines (U87MG and T98G), as well as tumor cells taken directly from a patient diagnosed with GBM. Using total reflection X-ray fluorescence we determined the contents of P, S, K, Ca, Fe, Cu, Zn, and Se in implanted-left and intact-right brain hemispheres. The number of elemental anomalies registered for both hemispheres was positively correlated with the invasiveness of GBM cells and was the highest for animals subjected to U87MG cell implantation, which presented significant decrease of P, K, and Cu levels and an increase of Se concentration within the left hemisphere. The abnormality common for all three groups of animals subjected to glioma cell implantation was increased Fe level in the brain, which may result from higher blood supply or the presence of hemorrhaging regions. In the case of the intact hemisphere, elevated Fe concentration may also indicate higher neuronal activity caused by taking over some functions of the left hemisphere impaired as a result of tumor growth.

Effects of Fermented Mushroom of Cordyceps sinensis, Rich in Selenium, on Uterine Cervix Cancer

The purpose of this study was to investigate the effect of fermented mushroom of Cordyceps sinensis (CS), rich in selenium (Se-CS), on uterine cervical cancer in mice. The methylcholanthrene- (MCA-) induced tumor model was used in this paper. After the mice were administered Se-CS, the animals showed 40% tumor incidence (P < 0.05). Se-CS also enhanced the immune functions. Se-CS treatment showed significant (P < 0.05–0.01) restoration in the level of glutathione content, lipid peroxidation, glutathione peroxidase activity, glutathione reductase activity, catalase activity, Na⁺/K⁺-ATPase activity, and glutathione S transferase activity. This finding suggested that the concomitant use of Se and CS could be a potential therapeutic approach to improve the efficacy of therapy for uterine cervical cancer.

Influence of inorganic and organic selenium on number of living mycelial cells and their ultrastructure in culture of Hericium erinaceum (Bull.: Fr. Pers.)

Mycelium of the white-rot fungus (Hericium erinaceum (Bull.: Fr. Pers.) produces polysaccharides showing anticancer and immunostimulating activity. In our previous works, we have shown that organic selenitetriglycerides (Selol) contribute to the increase of biosynthesis of exopolysaccharides (EPS) having antioxidative properties and containing large amounts of selenium. The present work is a study of influence of inorganic and organic form of selenium on viability of H. erinaceum mycelium and on ultrastructural changes taking place during its development in submerged culture. The mycelium was grown on media containing sodium selenite (Na2SeO3), a mixture of Na2SeO3 + Selol2% and on control medium (no selenium added). It was shown that mycelium cultured for 3 days in control conditions on standard media contained almost 100% of living cells, with over 80% after 24 days. Treatment with 100 ppm of Na2SeO3 lowered the number of viable cells to 11.8% and 9.1% after 3 and 24 days, respectively. The addition of 2% Selol caused the amounts of living cells to remain at ca 90%. Apparently, Selol helped the cells to cope with the toxic activity of inorganic selenium ions. The addition of sodium selenite induced degradative changes in cell organelles. Such changes were not observed in the case of Na2SeO3 + Selol mixture, in which case cells contained numerous ribosomes and small lipid bodies.

Estimation of trace elements in mace (Myristica fragrans Houtt) and their effect on uterine cervix cancer induced by methylcholanthrene

In the present work, trace elemental analysis of mace (Myristica fragrans Houtt) was carried out by the atomic absorption spectrometry technique. The concentrations of various elements analyzed in this medicine were ranked in decreasing order: selenium (Se) > zinc (Zn) > magnesium (Mg) > iron (Fe) > calcium (Ca) > manganese (Mn) > lead (Pb). The concentrations of Mg, Zn, Fe, Mn, Ca, and Se were significantly decreased in serum of methylcholanthrene tumor models (P < 0.001) compared with the control and mace groups. It is consistent with the result of tumor incidence. These trace elements could be directly or indirectly responsible for the antitumor activity of mace. The inorganic elements in this folk remedy can partly account for the antitumor.

Selenium: From cancer prevention to DNA damage

Selenium (Se) is a dietary essential trace element with important biological roles. Accumulating evidence indicates that Se compounds possess anticancer properties. Se is specifically incorporated into proteins in the form of selenocysteine and non-specifically incorporated as selenomethionine in place of methionine. The effects of Se compounds on cells are strictly compositional and concentration-dependent. At supranutritional dietary levels, Se can prevent the development of many types of cancer. At higher concentrations, Se compounds can be either cytotoxic or possibly carcinogenic. The cytotoxicity of Se is suggested to be associated with oxidative stress. Accordingly, sodium selenite, an inorganic Se compound, was reported to induce DNA damage, particularly DNA strand breaks and base damage. In this review we summarize the various activities of Se compounds and focus on their relation to DNA damage and repair. We discuss the use of Saccharomyces cerevisiae for identification of the genes involved in Se toxicity and resistance.

Selenium and the brain: a review

Similar to other tissues selenium from selenomethionine is deposited in the brain at higher concentrations than selenium in other forms. Vitamin E has a greater effect than selenium in reducing lipid peroxidation in various brain regions. Selenium does not have as great effect on glutathione peroxidase (GPX) activity in the brain as in most other organs. Prolonged selenium and iodine deficiencies will compromise thyroid hormone homeostatus in the brain and this is due to changes in deiodinases activities and lipid peroxidation. Even though selenium deficiency results in reduced GPX activity and selenium content in the brain, there is no reduction in thioredoxin reductase activity or selenoprotein W levels. Selenoprotein P is taken up in greater amounts by the brain but not by other organs in selenium deficient animals, suggesting a critical function of this selenoprotein in this organ. Selenium will influence compounds with hormonal activity (and neurotransmitters) in the brain, and this is postulated to be the reason selenium affects moods in humans and behavior in animals. Even though selenium counteracts the neurotoxicity of mercury, cadmium, lead and vanadium, it causes them to accumulate in the brain, presumably in a nontoxic complex.

The protective role of selenium on genetic damage and on cancer

Collectively, results from epidemiologic studies, laboratory bioassays, and human clinical intervention trials clearly support a protective role of selenium against cancer development. Several hypotheses have been proposed to explain these observations. Increased genomic instability, either inherent or induced by exogenous agents (mutagens or carcinogens), has been considered as a primary event leading to neoplastic transformation. This report deals specifically with the evidence for a role of selenium in the inhibition of carcinogen-induced covalent DNA adduct formation and retardation of oxidative damage to DNA, lipids and proteins, and for modulating cellular and molecular events that are critical in cell growth inhibition and in the multi-step carcinogenesis process. At present, the bulk of our knowledge on the role of selenium on genetic stability is based primarily on animal data and from studies conducted in in vitro systems. Studies performed in vitro showed that the dose and form of selenium compounds are critical factors with regard to cellular responses. Inorganic (at doses up to 10microM) and organic selenium compounds (at doses equal to or greater than 10microM) elicit distinctly different cellular responses. The recommended daily allowance (RDA) is 50-70 microgramSe per day for healthy adults; with 40 microgramSe as minimum requirement. Less than 11 microgramSe will definitely put people at risk of deficiency that would be expected to cause genetic damage. Daily doses of 100-200 microgramSe inhibited genetic damage and cancer development in humans. About 400 microgramSe per day is considered an upper limit. Clearly, doses above the RDA are needed to inhibit genetic damage and cancer. However, it has been hypothesized that the intake of excessive doses of selenium may cause oxidative damage, leading to genomic instability. The use of a cocktail consisting of selenium, and other vitamins and minerals appears to be a promising approach to inhibit genetic damage and the development of cancer. It is the author's recommendation that development of mechanism-based hypotheses that can be tested in pilot studies in different populations prior to a large-scale clinical trial in humans, is of paramount importance in order to better understand the role of selenium on genetic stability and cancer.

Selenium causes growth inhibition and apoptosis in human brain tumor cell lines

We examined the effect of the trace element selenium on human glioma cell lines: T98G, U373MG, and U87MG, in addition to dermal fibroblast cells. Cultures were incubated with sodium selenite, and the following parameters were studied: cell growth, mitochondrial function, and ultrastructure. Cell growth was assayed by counting the number of viable cells after treatment with selenium. Mitochondrial function was analyzed using the MTT (tetrazolium salt reduction) assay. Apoptosis was determined by evaluating nuclear chromatin condensation by electron microscopy. The results indicated that selenium had a significant inhibitory effect on the growth of the tumor cells but had little effect upon dermal fibroblasts which had been passaged numerous times. Selenium also induced mitochondrial damage as shown by MTT assay in two brain tumor cell lines and in minimally passaged fibroblasts, but it had little effect upon the high-passage fibroblasts. Ultrastructurally, mitochondria had electron-dense inclusions resulting from selenium treatment. High rates of apoptosis were induced by selenium in the tumor cell lines and in the minimally passaged fibroblasts, whereas the fibroblasts with a high number of passages had some resistance to selenium treatment. This study correlates the adverse effects of selenium on mitochondrial function, inhibition of cell growth, and apoptosis and shows that selenium similarly affects three different brain tumor cell lines and minimally passaged fibroblasts. Further, the results with fibroblasts show that some types of cells after repeated passages can develop resistance to selenium damage.

Chemopreventive mechanisms of selenium

The element selenium (Se) was recognized only 40 years ago as being essential in the nutrition of animals and humans. It is recognized as being an essential component of a number of enzymes in which it is present as the amino acid selenocysteine (SeCys). Selenium compounds have also been found to inhibit tumorigenesis in a variety of animal models and recent studies indicate that supplemental Se in human diets may reduce cancer risk. Anti-tumorigenic activities have been associated with Se intakes that are more than sufficient to correct nutritionally deficient status; that is, Se appears to be anti-tumorigenic at intakes that are substantially greater than those associated with maximal expression of the known SeCys-containing enzymes. Therefore, while some cancer protection may involve one or more Se-enzymes, it is probable that anti-tumorigenic functions of Se are discharged by certain Se-metabolites produced in significant amounts at relatively high Se intakes. Thus, Se supplementation of individuals with relatively low or frankly deficient natural intakes of the element can be expected to support enhanced anti-oxidant protection due to increased expression of the Se-dependent glutathione peroxidases and thioredoxin reductase. Higher levels of Se-supplementation can be expected to affect other functions related to tumorigenesis: carcinogen metabolism, immune function, cell cycle regulation and apoptosis. Thus, according to this 2-stage model of the roles of Se in cancer prevention, even individuals with nutritionally adequate Se intakes may benefit from Se-supplementation.

Chemopreventive agents: selenium

The element selenium (Se) was recognized only 40 years ago as being essential in the nutrition of animals and humans. It is recognized as being an essential component of a number of enzymes, in which it is present as the amino acid selenocysteine. Se compounds have also been found to inhibit tumorigenesis in a variety of animal models, and recent studies indicate that supplemental Se in human diets may reduce cancer risk. The antitumorigenic activities have been associated with Se intakes that correct nutritionally deficient status in animals, as well as higher intakes that are substantially greater than those associated with maximal expression of the selenocysteine-containing enzymes. Therefore, it is proposed that while some cancer protection, particularly that involving antioxidant protection, involves selenoenzymes, specific Se metabolites, which are produced in significant amounts at relatively high Se intakes, also discharge antitumorigenic functions. According to this two-stage model of the roles of Se in cancer prevention, individuals with nutritionally adequate Se intakes may benefit from Se supplementation. Evidence for chemoprevention by Se and for the apparent mechanisms underlying these effects is reviewed to the end of facilitating the development of the potential of Se compounds as cancer chemopreventive agents.

Symptomatic treatment of brain tumor patients with sodium selenite, oxygen, and other supportive measures

Patients (16 women and 16 men) with brain tumors previously treated conservatively by surgery, radiation, and/or chemotherapy with typical symptoms of increased intracranial pressure were consecutively enrolled to test the effects of pharmacological dosages of sodium selenite (selenase) in conjunction with other supportive therapies (biological response modifiers, detoxification, chemotherapy, immunotherapy, oxygen therapy). The rationale for the use of sodium selenite was that the whole-blood selenium levels were subnormal in 70% of the patients on admission. Patients also frequently presented abnormal levels of other minerals, especially lowered sodium and elevated potassium levels, which appears to be characteristic of brain tumor patients. Sodium selenite was administered by infusion at dosages of 1000 microg Se in physiological saline/d for 4-8 wk. In 76% of the patients, a definite, and in 24% a slight improvement of the general condition and a decrease in symptoms, such as nausea, emesis, headache, vertigo, unsteady gait, speech disorders, and Jacksonian seizures, were observed. In all treated patients, improvements of erythrocyte, hemoglobin, and thrombocyte counts were observed. Additional beneficial effects were noted in the patients receiving the oxygen therapy. It is concluded that the sodium selenite can be employed with oxygen therapy and other supportive measures in the management of brain tumor patients.