Methylseleninic Acid Research Articles

Effects of administering sodium selenite, methylseleninic acid, and seleno-L-methionine on glucose tolerance in a streptozotocin/nicotinamide-induced diabetic mouse model.

The effects of administering the selenocompounds, sodium selenite, methylseleninic acid (MSA), and seleno-L-methionine (SeMet) on glucose tolerance were compared in the nicotinamide (NA) and streptozotocin (STZ)-induced diabetic mouse model. ICR mice were intraperitoneally treated twice with STZ (100 mg/kg) 15 min after an injection of NA (120 mg/kg) at a 1-d interval. Non-fasting blood glucose levels were then monitored weekly while orally administering the selenocompounds at 158 µg Se/kg body weight with free access to a selenium-deficient diet for 5 weeks. The mean body weights of NA/STZ-induced diabetic mice were partly restored by the administration of selenocompounds, while SeMet led to a higher selenium content and glutathione peroxidase 1 activity in the pancreas. Non-fasting and oral glucose tolerance-tested blood glucose levels, which were elevated by NA/STZ, were significantly suppressed by the administration of SeMet. These results suggest that SeMet may improve glucose tolerance in a NA/STZ-induced mild diabetic mouse model by increasing bioavailability in the pancreas.

Glutathione-dependent cell cycle G1 arrest and apoptosis induction in human lung cancer A549 cells caused by methylseleninic acid: comparison with sodium selenite.

The aim of the present study was to clarify the mechanism underlying the inhibition of cell proliferation in human lung cancer A549 cells by selenium (Se) compounds. Methylseleninic acid (CH3SeO2H, abbreviated as MSA), a synthetic Se compound, is a direct precursor of active methylselenol (CH3SeH) and is considered to be one of beneficial agents for cancer prevention and therapy. Sodium selenite (Na2SeO3), an inorganic Se form, is utilized in clinical Se supplementation. MSA markedly inhibited the growth of A549 cells at a concentration of 2.5×10(-6) mol/L for 1 d. On Day 1, Na2SeO3 also inhibited A549 cell growth at the concentration of 7.5×10(-6) mol/L. These compounds induced cell cycle arrest at the G1 phase and apoptosis under the inhibitory condition. Reduced glutathione (GSH) is critical to MSA or Na2SeO3 metabolism. The depletion of intracellular GSH suppressed Na2SeO3-induced G1 arrest, but promoted Na2SeO3-induced apoptosis. Therefore, Na2SeO3 appears to have directly induced apoptosis. In contrast, the MSA-induced G1 arrest was ameliorated by a marked decrease in GSH content. Additionally, the depletion of GSH slightly suppressed MSA-induced apoptosis. The difference in inhibitory effects between MSA and Na2SeO3 may be due to this variation in GSH-related metabolism. After exposure of A549 cells to MSA, the GSH content was significantly decreased. These results indicate that because MSA-induced G1 arrest and apoptosis induction are enhanced by GSH, the maintenance of GSH is essential for the effective anticancer action of MSA in A549 cells.

Effects of methylseleninic acid on inhibition and chemosensitization of triple-negative breast cancer cells

Objective To investigate the effects of methylseleninic acid on chemosensitization of triple-negative breast cancer (TNBC) cells and the molecular mechanism.Methods Methylseleninic acid (MSA) (2.5,3.5,4.0 μmol/L) in combination with paclitaxel,doxorubicin or malondialdehyde (MDA)-treated MB-231 cells were cultured separately.Cell counting kit-8 (CCK-8) assay was applied to detect the inhibition of cell proliferation rate by chemotherapy drugs use alone or in combination with MSA,and the combined index was calculated to explore the impact of the function of MSA on the efficacy of chemotherapy drugs.Annexin V-FITC/propidium iodide (PI) double staining was applied to detect apoptosis,flow cytometry to examine cell cycle,and Western blotting to analyze thes histone deacetylase-6 (HDAC-6) expression.Results The cell proliferation rate of chemotherapy drugs in combination with MSA was decreased as compared with chemotherapy drugs used alone,suggesting the synergetic effects of MSA and chemotherapy drugs.The combined use of paclitaxel with MSA could significantly increase the number of cells in G2/M phase (P ＜ 0.05),that of doxorubicin with MSA could significandy increase the number of cells in S-phase cells (P ＜ 0.05),and the prompt MSA enhanced the effect of anticancer drugsinduced cell cycle arrest.MSA,paclitaxel and doxorubicin could induce apoptosis of TNBC cells.The apoptosis rate in MSA + chemotherapy groups was significantly increased as compared with monotherapy group and the control group.Chemotherapy drugs alone did not affect the expression of HDAC-6,and MSA used alone or incombination with chemotherapy drugs could significantly inhibit the HDAC-6 expression.Conclusion MSA enhanced anticancer drugs-induced cell cycle arrest and apoptosis so as to improve the efficacy of chemotherapy drugs probably by regulating the HDAC-6 expression. Key words: Breast cancer; Chemotherapy; Methylseleninic acid; Apoptosis

Suppression of FOXO1 is responsible for a growth regulatory repressive transcriptional sub-signature of EWS-FLI1 in Ewing sarcoma.

The Ewing sarcoma (ES) EWS-FLI1 chimeric oncoprotein is a prototypic aberrant ETS transcription factor with activating and repressive regulatory functions. We report that EWS-FLI1-repressed promoters are enriched in forkhead box (FOX) recognition motifs, and identify FOXO1 as a EWS-FLI1-suppressed regulator orchestrating a major subset of EWS-FLI1-repressed genes. In addition to FOXO1 regulation by direct promoter binding of EWS-FLI1, its subcellular localization and activity is regulated by cyclin-dependent kinase 2- and AKT-mediated phosphorylation downstream of EWS-FLI1. Restoration of nuclear FOXO1 expression in ES cells impaired proliferation and significantly reduced clonogenicity. Gene-expression profiling revealed a significant overlap between EWS-FLI1-repressed and FOXO1-activated genes. As a proof of principle for a potential therapeutic application of our findings, the treatment of ES cell lines with methylseleninic acid (MSA) reactivated endogenous FOXO1 in the presence of EWS-FLI1 in a dose- and time-dependent manner and induced massive cell death dependent on FOXO1. In an orthotopic xenograft mouse model, MSA increased FOXO1 expression in the tumor paralleled by a significant decrease in ES tumor growth. FOXO1 reactivation by small molecules may therefore serve as a promising strategy for a future ES-specific therapy.

Lipophilicity, biomimetic retention profile and antioxidant activity of selenium species

The lipophilicity and biomimetic retention profile of three selenium species, methyl-seleninic acid (MSA), Se-Methyl-selenocysteine (MeSeC) and dimethyl-selenourea (DMeSeU), were established. Lipophilicity was measured by the shaking flask method, while for chromatography one reversed-phase (Discovery C-18) column and three biomimetic stationary phases, namely immobilized artificial membrane (IAM), human serum albumin (HSA) and α1-acid glycoprotein (AGP) were employed, under different mobile phase conditions. These results were combined with previous data obtained under analogous conditions on eight selenium species including selenites (Se(IV)), selenates (Se(VI)), selenomethionine (SeMet), selenocystine (SeCyst), selenocystamine (SeCM), selenourea (SeU), dimethylselenide ((CH3)2Se) and dimethyldiselenide ((CH3)2Se2). The combined data were further used to establish relations between biomimetic retention factors and lipophilicity, the effect of the presence of reduced glutathione (GSH) to retention, as well as to determine the oxidation potential by means of cyclic voltammetry. According to their anode potentials in cyclic voltammetry, only the urea analogues, SeU and, especially, DMeSeU, exhibited considerable antioxidant properties. Moreover IAM retention of Se(IV), Se(VI), SeMet and MeSeC was correlated with Caco-2 apparent permeability coefficient (Papp) available in literature. IAM retention data were further converted to percentage of human oral absorption according to a relevant equation reported in the literature, while from HSA retention results the plasma protein binding was estimated. According to these values, low biopersistence in the human body may be anticipated.

Dietary selenium supplementation modifies breast tumor growth and metastasis

The survival rate for breast cancer drops dramatically once the disease progresses to the metastatic stage. Selenium (Se) is an essential micronutrient credited with having high anticancer and chemopreventive properties. In our study, we investigated if dietary Se supplementation modified breast cancer development in vivo. Three diets supplemented with sodium selenite, methylseleninic acid (MSA) or selenomethionine (SeMet), as well as a Se-deficient and a Se-adequate diet were fed to mice before mammary gland inoculation of 4T1.2 cells. The primary tumor growth, the numbers of cancer cells present in lungs, hearts, livers, kidneys and femurs and several proinflammatory cytokines were measured. We found that inorganic selenite supplementation provided only short-term delay of tumor growth, whereas the two organic SeMet and MSA supplements provided more potent growth inhibition. These diets also affected cancer metastasis differently. Mice fed selenite developed the most extensive metastasis and had an increased incidence of kidney and bone metastasis. On the other hand, mice fed the SeMet diet showed the least amount of cancer growth at metastatic sites. The MSA diet also provided some protection against breast cancer metastasis although the effects were less significant than those of SeMet. The cytokine profiles indicated that serum levels of interlukin-2, interleukin-6, interferon γ and vascular endothelial growth factor were elevated in SeMet-supplemented mice. There was no significant difference in tumor growth and the patterns of metastasis between the Se-deficient and Se-adequate groups. Our data suggest that organic Se supplementation may reduce/delay breast cancer metastasis, while selenite may exacerbate it.

Porcine Serum Can Be Biofortified with Selenium to Inhibit Proliferation of Three Types of Human Cancer Cells1–3

Our objectives were to determine if porcine serum could be enriched with selenium (Se) by feeding pigs with high concentrations of dietary Se and if the Se-biofortified serum inhibited proliferation of 3 types of human cancer cells. In Expt. 1, growing pigs (8 wk old, n = 3) were fed 0.02 or 3.0 mg Se/kg (as sodium selenite) for 16 wk and produced serum with 0.5 and 5.4 μmol/L Se, respectively. In Expt. 2, growing pigs (5 wk old, n = 6) were fed 0.3 or 1.0 mg Se/kg (as Se-enriched yeast) for 6 wk and produced serum with 2.6 and 6.2 μmol/L Se, respectively. After the Se-biofortified porcine sera were added at 16% in RPMI 1640 to treat NCI-H446, DU145, and HTC116 cells for 144 h, they decreased (P < 0.05) the viability of the 3 types of human cancer cells by promoting apoptosis, compared with their controls. This effect was replicated only by adding the appropriate amount of methylseleninic acid to the control serum and was mediated by a downregulation of 8 cell cycle arrest genes and an upregulation of 7 apoptotic genes. Along with 6 previously reported selenoprotein genes, selenoprotein T (Selt), selenoprotein M (Selm), selenoprotein H (Selh), selenoprotein K (Selk), and selenoprotein N (Sepn1) were revealed to be strongly associated with the cell death-related signaling induced by the Se-enriched porcine serum. In conclusion, porcine serum could be biofortified with Se to effectively inhibit the proliferation of 3 types of human cancer cells and the action synchronized with a matrix of coordinated functional expression of multiple selenoprotein genes.

A tight junction between E-Cadherin and the prostate tumor suppressor SPDEF

A tight junction between E-Cadherin and the prostate tumor suppressor SPDEF

Differential effects of selenium (Se) on normal and malignant cells treated with chemotherapy (CT) and radiation (RT).

e13583 Background: Preclinical work has demonstrated that Se compounds potentiate anticancer effects of CT and RT while reducing normal tissue toxicities. The molecular basis for the therapeutic selectivity has yet to be fully elucidated but includes modulation of intracellular glutathione (GSH) concentrations, endoplasmic reticulum (ER) stress responses, DNA repair, induction of apoptosis and cellular resistance to CT and RT. Our aim was to evaluate the dose-response relationship of the Se compound methylseleninic acid (MSA) on molecular pathways involved in the response of normal and malignant cells to CT and RT. Methods: Peripheral blood mononuclear cells (PBMC) obtained from healthy blood donors and malignant THP-1 human monocytic leukaemia cells were exposed in vitro to MSA 2.5, 5 or 15 µM in varying combinations with MSA, RT, cisplatin (Pt), doxorubicin (Dox) and cytosine arabinoside (Ara-C). GSH concentration was measured by ELISA, DNA damage and repair by COMET assay, cell viability by MTT assay and ER stress response protein expression by western blotting. Results: MSA was selectively toxic to THP-1 cells and induced a protective increase in GSH in PBMC but a decrease in high concentrations within THP-1 cells. DNA damage induced by Ara-C or Dox in the COMET assay was significantly reduced by MSA in PBMC but increased in THP-1 cells. Cell death after 2 Gy RT was increased by all doses of MSA in THP-1 cells but only by the highest dose in PBMC. The cytotoxicity of Dox and Ara-C at sublethal doses was significantly enhanced by MSA in THP-1 cells and to a lesser extent in PBMC, but MSA increased cell death from Pt only in THP-1 cells. MSA induced a protective ER stress response in PBMC exposed to Ara-C but an apoptotic response in THP-1 cells. Conclusions: MSA at clinically-relevant concentrations had a differential effect on cell survival and death responses to RT and CT with relative protection of PBMC and enhanced death of THP-1 cells. Several mechanisms mediated this therapeutic selectivity and the dose-dependence of the Se effect varied between malignant and normal cells. These assays could potentially be used in clinical trials to evaluate pharmacodynamic markers of Se effects in conjunction with CT and/or RT.

Homeostatic housecleaning effect of selenium: Evidence that noncytotoxic oxidant‐induced damage sensitizes prostate cancer cells to organic selenium‐triggered apoptosis

The anti-cancer activity of organic selenium has been most consistently documented at supra-nutritional levels at which selenium-dependent, antioxidant enzymes are maximized in both expression and activity. Thus, there is a strong imperative to identify mechanisms other than antioxidant protection to account for selenium's anti-cancer activity. In vivo work in dogs showed that dietary selenium supplementation decreased DNA damage but increased apoptosis in the prostate, leading to a new hypothesis: Organic selenium exerts its cancer preventive effect by selectively increasing apoptosis in DNA-damaged cells. Here, we test whether organic selenium (methylseleninic acid; MSA) triggers more apoptosis in human and canine prostate cancer cells that have more DNA damage (strand breaks) created by hydrogen-peroxide (H₂O₂) at noncytotoxic doses prior to MSA exposure. Apoptosis triggered by MSA was significantly higher in H₂O₂-damaged cells. A supra-additive effect was observed--the extent of MSA-triggered apoptosis in H₂O₂-damaged cells exceeded the sum of apoptosis induced by MSA or H₂O₂ alone. However, neither the persistence of H₂O₂-induced DNA damage, nor the activation of mitogen-activated protein kinases was required to sensitize cells to MSA-triggered apoptosis. Our results document that selenium can exert a "homeostatic housecleaning" effect--a preferential elimination of DNA-damaged cells. This work introduces a new and potentially important perspective on the anti-cancer action of selenium in the aging prostate that is independent of its role in antioxidant protection.

Abstract 3677: Prostate cancer progression decreases the cancer prevention by selenium: relation to overexpression of protein kinase Cε and selenoprotein thioredoxin reductase.

Abstract Selenium effectively prevents cancer in some cases, but fails in other cases. It could be possible that cancer-preventive actions of selenium are diminished by tumor progression, thus making this an important issue to study. In previous studies, tumor cell sensitivity to selenium was determined with commonly used, highly malignant prostate cancer cell lines such as DU145, PC-3, and LNCaP, which were originally cloned from different patients. These cell lines help us understand the mechanistic details of selenium-induced cellular effects, but due to their different genetic backgrounds, it is difficult to establish mechanisms related to cellular sensitivity to selenium. Previously, others have cloned a family of human prostate cancer cell lines with a common lineage showing progression characteristics from a low to high degree of malignancy and mimicking different stages of tumor progression seen in human prostate cancer. For this study, we used these prostate cancer cell lines with increasing tumorigenicity and invasive ability: WPE1-NA22 showing the lowest, WPE1-NB14 and WPE1-NB11 showing intermediate, and WPE1-NB26 showing the greatest. The low tumorigenic cell line, WPE1-NA22 resembles noninvasive prostatic intra-epithelial neoplasia and represents a good target for chemoprevention in humans. In this study, we found that WPE1-NA22 cells required a lower concentration of methylseleninic acid (MSA) for inhibition of cell growth (anchorage-dependent and anchorage-independent), induction of apoptosis, and inhibition of matrigel invasion. On the contrary, highly malignant cell line WPE1-NB26 required higher concentration of MSA to induce these effects, whereas moderately malignant cell lines WPE1-NB14 and WPE1-NB11 required intermediate levels of MSA. We have previously shown that protein kinase Cε (PKCε) is a molecular target for MSA and that the redox modification of this kinase is reversed by thioredoxin reductase (TR) system. Therefore, we determined whether there is an increase in expression of these two enzymes in tumor progression relating to a decrease in sensitivity to MSA. Western immunoblot analysis revealed low levels of PKCε, TR1, and TR2 in low tumorigenic WPE1-NA22 cells, while their levels were higher in advanced malignant cell lines correlating with their sensitivity to MSA. A conditional overexpression of PKCε in WPE1-NA22 cells resulted in an increase of both growth in soft agar and matrigel invasion and a decrease in sensitivity to MSA. An inhibition of TR activity in WPE1-NB26 resulted in an increase in sensitivity to MSA. Conceivably, there is an inverse correlation between the sensitivity to selenium-induced cancer prevention and prostate tumor progression involving an overexpression of PKCε and TR. Citation Format: Rayudu Gopalakrishna, Barsegh A. Barseghian, Carleen Sarksian, Jason E. Schiffman, David V. Rayudu, Usha Gundimeda. Prostate cancer progression decreases the cancer prevention by selenium: relation to overexpression of protein kinase Cε and selenoprotein thioredoxin reductase. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3677. doi:10.1158/1538-7445.AM2013-3677

Abstract 191: Methylseleninic acid super-activates p53 senescence axis as a preventive barrier to prostate tumorigenesis driven by Pten deficiency in vivo.

Abstract Prostate cancer (PCa) arises from progression of pre-invasive lesions such as prostatic intraepithelial neoplasia (PIN) to adenocarcinoma and metastatic disease. Due to the very long latency of lesion progression, chemoprevention of prostate adenocarcinogenesis is recognized as a plausible and essential approach to win the war against PCa. Whereas the results from recent clinical trials (SWOG 9917 and SELECT) did not support the protective function for seleno-methionine (SeMet) supplement in healthy men with or without high grade PIN, we and others have shown that supra-nutritional supplement of methylseleninic acid (MSeA), which differs, both chemically and metabolically, from SeMet, suppressed tumor growth in human prostate cancer xenografts, and in the transgenic adenocarcinoma mouse prostate (TRAMP) model. However, the former models did not mimic primary prevention, and the TRAMP mice vastly differ from the etiology and adenocarcinogenesis nature of the human prostate cancers. Therefore, a mouse model that closely recapitulates the clinic pathological features of human prostate cancer will be essential and necessary to predict the preventive efficacy and mechanisms of MSeA in men. As the loss of tumor suppressor gene Pten (phosphatase and tensin homolog deleted on chromosome 10) plays a causal role in human prostate cancers, the prostate epithelial-specific Pten-knockout mouse is such a preclinical model of choice. Here we utilized Probasin-Cre (Pb-Cre) transgenic mice expressing Cre to delete Pten in prostate epithelium to investigate whether administration of MSeA inhibited prostate tumorigenesis. We treated Pten-knockout and age-matched wild type male mice from 8 weeks of age with water or MSeA at a dose of 3 mg/kg body weight five times a week (Monday through Friday) for 27 weeks and sacrificed them for analyses. Our results show that MSeA significantly suppressed prostate tumorigenesis as evidenced by (1) suppression of tumor progression to high grade PIN or/and adenocarcinoma; (2) a 50% reduction in prostate tumor weight (P&amp;lt;0.01); (3) a significant reduction in cellular proliferation determined by ki67 immunostaining (P&amp;lt;0.01); and (4) attenuation of androgen receptor (AR) signaling. Mechanistically, we found that MSeA induced a super-activation of p53, p21 and cellular senescence. Because intact p53 signaling is preserved in most early prostate lesions, our findings provide compelling rationale to consider MSeA as a bioactive dietary supplement to activate p53-p21 mediated senescence as a barrier to prevent PIN from progressing to advanced prostate cancer. Citation Format: Lei Wang, Hua Xiong, Fengxia Wu, Tao Lin, Junxuan Lu, Yibin Deng. Methylseleninic acid super-activates p53 senescence axis as a preventive barrier to prostate tumorigenesis driven by Pten deficiency in vivo. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 191. doi:10.1158/1538-7445.AM2013-191

Abstract 315: Proteomic profiling of PTEN-deletion mouse prostate and its molecular pharmacodynamic responses to methylseleninic acid .

Abstract Recent genomic and exome sequencing analyses revealed that loss of one allele of tumor suppressor gene Pten (phosphatase and tensin homolog deleted on chromosome 10) occurs frequently in primary prostate tumors, and homozygous deletion of Pten plays a casual role in advanced prostate cancer. Therefore, the prostate-specific PTEN-deletion driven prostate cancer mouse model resembles many features of human prostate cancer including disease progression to metastasis. Due to its high clinical relevance, this model is gaining wider utility for prostate cancer chemoprevention and therapeutic studies. Very recently, our collaborative team found that oral administration of methylseleninic acid (MSeA), a second-generation selenium compound, significantly inhibited PTEN-loss driven prostate tumorigenesis in vivo. In particular, the efficacy was associated with a super-activation of p53-p21 senescence pathway (PTEN-loss induced cellular senescence, PICS). To gain insights into additional molecular targets, we profiled the prostate proteome of PTEN-deletion mice. Whole prostates from PTEN-deletion mice (12-15 weeks of age) and their wild type littermate were obtained from the NCI Mouse Model Repository. Homogenate from 4 prostate pairs (Pten−/− and wild type) was prepared and digested individually and the peptides were labeled with 8-plex iTRAQTM reagents. Labeled peptides were pooled and analyzed by 2D-LC-MS/MS (LTQ Orbitrap Velos, Thermo Scientific). Out of 949 proteins identified, we further analyzed 152, the expressions of which were significantly and concordantly changed in all four pairs of mice. Among them, we detected enrichment of proteins related to cellular senescence (chitinase-3 like protein3 [CH3L3], cathelin-related antimicrobial peptide [Camp]), p53 (S100-A8, sorbitol dehydrogenase [DHSO]) and molecular targets involved in AKT signaling pathway (lipocalin 2, CH3L3), in line with the well-described AKT driven p53-mediated senescence in Pten-deficient prostate cancer mouse model. We also found decreased protein expression of GRP78 (78 kDa glucose-regulated protein), endoplasmin, probasin and TGM4 (transglutaminase4), same as we reported in the TRAMP model. Some of these protein changes (over or under) were predicated by published changes of their mRNA levels in prostates (probasin, TGM4, etc) and/or protein levels in sera (probasin, endoplasmin, GRP78, etc). Moreover, the congruence on some proteins (DHSO, S100-A8, etc) between the mouse model and clinical specimens (e.g. by C. Sawyers) highlights the clinical relevance of the model. The proteomic changes induced by MSeA are being investigated. Citation Format: Jinhui Zhang, Yibin Deng, Junxuan Lü. Proteomic profiling of PTEN-deletion mouse prostate and its molecular pharmacodynamic responses to methylseleninic acid . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 315. doi:10.1158/1538-7445.AM2013-315

Abstract 3693: Methaneseleninic acid and γ-tocopherol combination inhibits prostate tumor growth in a xenograft model .

Abstract Prostate Cancer (PCa) is the second leading cause of cancer-related deaths in American males. Several in vitro and in vivo studies have suggested that vitamin E as well as selenium possesses potential in the management of PCa. However, results from the large-scale Selenium and Vitamin E Cancer Prevention Trial (SELECT) found that vitamin E (α-tocopheryl acetate; 400 mg) and/or selenium (L-selenomethionine; 200 μg) were ineffective in preventing PCa. Based on these seemingly contradictory outcomes, we believe that the dose and formulation of both these agents were sub-optimal in the SELECT trial, and may be critical in providing appropriate biological response in PCa. Thus, additional studies are needed to define the most appropriate formulations of vitamin E and selenium as well as the optimal dosages of these two agents. Following a careful analysis of literature, we evaluated the effect of methylseleninic acid (MSA in sterile water; oral gavage) and/or γ-tocopherol (γT in tocopherol-stripped corn oil; oral gavage), at a dose much lower than used in SELECT, against prostate tumors in an immunecompromised mouse model. Sixty Nu/J mice were implanted with 22Rν1 cells, tumors were allowed to grow to an average volume of 36 mm3, followed by treatment in 6 groups (10 animals each): 1) Control (vehicle alone); 2) MSA (41 μg/kg); 3) γT (20.8 mg/kg); 4) γT (41.7 mg/kg); 5) MSA (41 μg/kg) + γT (20.8 mg/kg); and 6) MSA (41 μg/kg) + γT (41.7 mg/kg). The mice were treated for 2 weeks (5 days per week) and followed for tumor growth. At the end of experiment, the mice were sacrificed and further studies were done. Our data demonstrated that the combination of γT (20.8 mg/kg) and MSA (41 μg/kg) resulted in a significant decrease in i) serum prostate specific antigen levels, ii) tumor volume and tumor wet weight, and iii) Ki-67 proliferation index. We found that this combination also resulted in i) an up-regulation of pro-apoptotic Bax coupled with a down-regulation of the pro-survival protein Bcl2, thereby resulting in an increased Bax/Bcl2 ratio, and ii) an increase in pro-apoptotic protein Bad. Further, γT and MSA combination modulated levels of apolipoprotein E, selenoprotein P and Nrf2 in a fashion that favors anti-proliferative responses in PCa. Interestingly, we found that the combination using a lower dose of γT was much more effective than the higher dose, in most of the parameters evaluated. In the most effective treatment group, the approximate daily human equivalent dose for γT was 72 mg/day (corresponding to 20.8 mg/kg in mouse) and for MSA is 142 μg/day (corresponding to 41 μg/kg in mouse), which is significantly lower than the doses used in SELECT. Overall, our study suggests that γT and MSA, at the lower dose regimen, could be useful in PCa management. However, further studies with additional formulations and doses in more relevant animal model(s) are needed to confirm our findings. Citation Format: Chandra K. Singh, Mary A. Ndiaye, Imtiaz A. Siddiqui, Minakshi Nihal, Thomas Havighurst, Weixiong Zhong, Hasan Mukhtar, Nihal Ahmad. Methaneseleninic acid and γ-tocopherol combination inhibits prostate tumor growth in a xenograft model . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3693. doi:10.1158/1538-7445.AM2013-3693

Spatial and temporal expression of histone H3 Lysine 9 trimethylation foci by methylseleninic acid treatment

We have recently shown that selenium compounds can induce a senescence response in a manner depending on ataxia‐telangiectasia mutated (ATM), DNA‐dependent protein kinase (DNA‐PK), p53 and reactive oxygen species (ROS). To test the hypothesis that the selenium‐induced senescence response involves epigenetic changes in senescence‐associated heterochromatin foci (SAHF), we determined the expression of histone H3 Lysine 9 trimethylation (H3K9me3), a marker of SAHF, in human primary MRC‐5 cells treated with methylseleninic acid (MSeA, 2 μM) for 2 days, followed by a 7‐day recovery, in the presence or absence of KU55933 (10 μM), an ATM kinase inhibitor, and NU7026 (10 μM), a DNA‐PK kinase inhibitor. Our results showed that MSeA treatment induced the formation of SAHF and H3K9me3 foci. Pre‐treatment of the cells with KU55955 or NU7026 resulted in numerous and smaller foci, and they did not co‐localize with the MSeA‐induced SAHF. These results suggest that the MSeA‐induced senescence response involves epigenetic changes of H3K9me3 in a manner depending on ATM and DNA‐PK.Grant Funding Source: UMCP

Methylseleninic acid sensitizes Notch3 activated ovarian cancer cells to carboplatin

Ovarian cancer is the deadliest of gynecologic cancers and is usually diagnosed at advanced stage due to invalidated screening test. Although carboplatin has been used for treating ovarian cancer for years, ovarian cancer eventually develops resistance to this platinum‐containing drug. Animal studies have demonstrated efficacies of methylseleninic acid (MSeA) in counteracting tumorigenesis. Expression of Notch3 is associated with chemoresistance and correlated with poor overall survival of human ovarian cancer patients. Here we tested the hypothesis that MSeA can sensitize OVCA429/NICD3 cells to carboplatin treatment. Overexpression of NICD3 (the constitutively active form of Notch3) in OVCA429 ovarian cancer cells (OVCA429/NICD3) rendered them resistance to carboplatin compared to OVCA429 cells transduced with an empty vector (OVCA429/pCEG). Co‐treatment with MSeA sensitized OVCA429/NICD3, but not OVCA429/pCEG cells to carboplatin treatment. These two chemicals appear to synergistically kill OVCA429/NICD3 cells, which can be suppressed by the presence of N‐acetyl cysteine or DNA damage kinase inhibitors of ATM and DNA‐PKcs. In summary, MSeA sensitizes OVCA429/NICD3 cells to carboplatin treatment in a pathway involves oxidative stress, ATM and DNA‐PKcs, suggesting a new strategy to improve the efficacy of carboplatin treatment against ovarian cancer.Grant Funding Source: UMCP

Methylselenol, a selenium metabolite, inhibits colon cancer cell growth in vitro and in vivo

Methylselenol is hypothesized to be a critical selenium (Se) metabolite for certain anticancer activities in vivo but its role in colon cancer prevention remains to be characterized. This study tested the hypothesis that methylselenol inhibits the growth of colon cancer cells and tumors. We found that submicromolar methylselenol exposure inhibited cell growth and led to an increase in the G1 and G2 fractions with a concomitant drop in the S‐phase, and an induction of apoptosis in cancerous colon HCT116 cells, but to a much lesser extent in noncancerous NCM460 colon cells. Furthermore, in agreement with the fact that blockade of extracellular‐regulated kinase1/2 (ERK1/2) and p38 mitogen activated protein kinase (p38 MAPK) pathways suppresses the growth of colon tumors, we demonstrated that methylselenol inhibited ERK1/2 and p38 MAPK in cancerous colon HCT116 cells but also to a lesser extent in NCM460 cells. Consistent with these in vitro observations, a daily single oral dose (1 to 3 mg Se/kg body weight) of methylseleninic acid, a methylselenol precursor, for 5 weeks inhibits the growth of colon cancer xenografts in a C57/BL mouse model. Taken together, methylselenol's strong potential of inhibiting colon cancer cell proliferation, may be an important mechanism by which Se exerts its anticancer activity in colon cancer prevention.

Selenium for the Prevention of Cutaneous Melanoma

The role of selenium (Se) supplementation in cancer prevention is controversial; effects often depend on the nutritional status of the subject and on the chemical form in which Se is provided. We used a combination of in vitro and in vivo models to study two unique therapeutic windows for intervention in the process of cutaneous melanomagenisis, and to examine the utility of two different chemical forms of Se for prevention and treatment of melanoma. We studied the effects of Se in vitro on UV-induced oxidative stress in melanocytes, and on apoptosis and cell cycle progression in melanoma cells. In vivo, we used the HGF transgenic mouse model of UV-induced melanoma to demonstrate that topical treatment with l-selenomethionine results in a significant delay in the time required for UV-induced melanoma development, but also increases the rate of growth of those tumors once they appear. In a second mouse model, we found that oral administration of high dose methylseleninic acid significantly decreases the size of human melanoma xenografts. Our findings suggest that modestly elevation of selenium levels in the skin might risk acceleration of growth of incipient tumors. Additionally, certain Se compounds administered at very high doses could have utility for the treatment of fully-malignant tumors or prevention of recurrence.

Influence of MSA on cell growth and spontaneousn metastasis of L9981-Luc lung cancer transplanted model in nude mice by bioluminescence imaging

背景与目的甲基硒酸是一种新型的人工合成的硒化合物。研究发现甲基硒酸对肿瘤细胞的生长转移有抑制作用。本研究的目的是探讨甲基硒酸对L9981-Luc裸鼠异体移植瘤生长和转移能力的抑制作用及机制。方法建立L9981-Luc肺癌细胞株移植瘤模型，用精诺真活体动物可见光成像系统观察肺癌移植瘤肿瘤生长转移情况。实验将6周龄裸鼠15只，随机分为3组，每组5只，对照组每日腹腔注射生理盐水0.2 mL；甲基硒酸组每日腹腔注射甲基硒酸溶液50 μg（0.2 mL）；顺铂组每周腹腔注射顺铂4 mg/kg。结果接种第21天，不同组间原发瘤发光值比较差异有统计学意义（P=0.002）；顺铂组发光值明显低于对照组（P=0.001），甲基硒酸组发光值明显低于对照组（P=0.031）。不同药物处理组胸部转移信号发光值差异无统计学意义（P > 0.05）。结论甲基硒酸能明显抑制L9981-Luc裸鼠异体移植瘤生长，并有抑制L9981-Luc原发瘤肺转移的趋势。

Pharmacokinetics and cytotoxic effect of selenium compounds in rodent cancer xenograft model for therapy experiment

To the editor: It has been, currently, acknowledged that selenium, as a chemopreventive agent, reduces considerably the risk of prostate, colorectal, lung, breast or any other cancer. Furthermore, therapeutic application of selenium compounds for several advanced epithelial carcinomas has been tried through translational research. Although the anti-tumor mechanism of selenium was not entirely understood, apoptosis mediated by reactive oxygen species is mainly suggested. In the volume 23, a research article regarding the therapeutic effects of sodium selenite on epithelial ovarian cancer was very impressive in terms of therapy experiment employing rodent orthotopic ovarian cancer xenograft model [1]. Summarizing the results, in vitro growth of selenite-treated cancer cells was significantly decreased; however, in vivo treatment with sodium selenite (1.5 mg/kg, intraperitoneal injection, 3 times per week) did not show apparent inhibitory effect against tumor growth. Various forms of selenium compounds exist. Selenomethionine is synthesized by plants and often used as a supplement in human studies. Selenocysteine represents the proteinogenic amino acid and selenium exerts its biological effects mainly via selenocysteine-containing proteins. Na2SeO3 (selenite), Na2SeO4 (selenate), and methylseleninic acid are inorganic selenium salts. From an in vitro assessment of cytotoxic effects on hepatocyte according to forms of selenium compounds, it was reported that the most powerful and fastest effect was observed in the methylseleninic acid, which is a potent second-generation selenium compound having different biological and pharmacological activity [2]. Additionally, in terms of route-dependent pharmacokinetics of selenium compounds, Willhite et al. [3] reported the high oral bioavailability of organic or inorganic selenium in hamsters. Total absorption of selenomethionine was measured as 73% and that of selenate was 100% in their experiment. Most recently, it was reported that the orally administered methylseleninic acid synergistically enhanced paclitaxel efficacy in a treatment experiment employing breast cancer xenograft model [4]. Therefore, these kinds of issues are needed to be considered for the future design of therapy experiment using selenium in ovarian cancer.