[Effects of Sodium Selenite and Dithiothreitol on Expression of Endoplasmic Reticulum Selenoproteins and Apoptosis Markers in MSF7 Breast Adenocarcinoma Cells].

The endoplasmic reticulum (ER) stress inducers dithiothreitol (DTT) and sodium selenite (SS) were tested for effect on expression of ER selenoproteins and apoptosis markers in MCF7 breast adenocarcinoma cells. DTT used at 1 or 5 mM did not affect the survival of MCF7 cells. Based on the real-time PCR data and the protein expression levels of ER stress markers, ER stress was assumed to evolve along an adaptation pathway in MCF7 cells treated with 1 or 5 mM DTT, involving mainly the transcription factors IRE1 and ATF6 and the selenoproteins SELS, SELK, SELT, SELM, and SELN. Cell treatment with 0.01 µM SS decreases the mRNA levels of all genes examined. When the SS concentration was increased to 0.1 µM, an increase in expression was observed for key ER stress genes and apoptosis markers, including CHOP, GADD34, PUMA, BIM, ATF4, sXBP, uXBP, AKT1, BAX, and BAK. Higher SS concentrations were assumed to trigger the unfolded protein response (UPR) via a proapoptic signaling pathway involving PERK and an alternative IRE1 signaling pathway. Used at 1 µM, SS increased the mRNA levels of apoptosis markers, upregulated expression of a spliced form of XBP1, and substantially decreased the cell survival. SS (1 µM) was assumed to trigger apoptosis in MCF7 cells. The results indicate that both adaptive and proapoptic UPR signaling pathways are activated in cells, depending on the nature and concentration of the ER stress inducer.

Expression of ER-resident selenoproteins and activation of cancer cells apoptosis mechanisms under ER-stress conditions caused by methylseleninic acid.

The aim of this work was to study changes in gene expression levels of 7 ER-resident selenoproteins under ER-stress caused by the action of a selenium-containing compound of organic nature, methylselenic acid using three human cancer cell lines DU 145 (prostate carcinoma), MCF 7 (breast adenocarcinoma)and HT-1080 (fibrosarcoma). According to the obtained results, we can speak of a synchronous changes in the expression of SELT and SEP15 mRNA depending on the concentration of MSA for 24 h, while the pattern of SELM expression was completely opposite and was radically different from other selenoproteins. It should be noted that in HT-1080 cells, the expression pattern of SELM differed from the expression pattern in two other cancer cells, while the expression patterns of other ER-resident selenoproteins (SELT, SEP15, SELK, SELS, SELN and DIO2) differed slightly depending on the cell line. Also we investigated the molecular mechanisms of UPR caused by MSA-induced ER stress in three cancer cell lines. According to the obtained results, it can be assumed that in DU 145 cells, MSA promotes activation of the PERK signaling pathway of UPR. In fibrosarcoma cells MSA was promoted the activation of ATF-6 UPR signaling pathway. In MCF 7 cells, MSA promoted the activation of two pro-apoptotic UPR signaling pathways at once: IRE1 and ATF-6.The results of this work once again demonstrate that the mechanisms of ER-stress regulation caused by the same agent, in this case, MSA, lead to the activation of different UPR signaling pathways in different cancer cells, and about their relationship.

Activation of Signal Pathways of Apoptosis under Conditions of Prolonged ER-Stress Caused by Exposure of Mouse Testicular Teratoma Cells to Selenium-Containing Compounds.

Aim to study the molecular mechanisms of apoptotic death of mouse testicular teratocarcinoma cells (line F-9) under exposure to the widely used selenium-containing compounds with antitumor activity, sodium selenite and methylseleninic acid. Methods fluorescence microscopy, MTT assay, Western blotting. Results It was shown that sodium selenite at a concentration of 10 µM and methylseleninic acid at concentrations of 1 and 10 µM cause apoptosis-dependent death of F-9 cells, excluding necrotic death. Western blotting showed an increase in the expression of XBP1s when treating F-9 cells with 1 µM methylseleninic acid. Conclusions 10 µM methylseleninic acid leads to cell apoptosis, most likely by activation of the IRE1 signaling pathway under prolonged stress of the endoplasmic reticulum.

Protein Partners of Selenoprotein SELM and the Role of Selenium Compounds in Regulation of Its Expression in Human Cancer Cells.

The search for potential partners of human SELM in lysates of two cancer cell lines, HT-1080 (fibrosarcoma) and MCF-7 (breast adenocarcinoma), was carried out. Two cytoplasmic actin isoforms-cytoplasmic actin 1 (cytoskeleton ß-actin) and cytoplasmic actin 2 (cytoskeletal γ-actin)-were identified as partners. In addition, the influence of two widely used antitumor selenium compounds (sodium selenite and methylseleninic acid) on the expression of SELM in cancer cells was studied. On the basis of the results obtained by real-time PCR and Western blotting, we concluded that 1 µM and 10 µM sodium selenite did not affect the expression of SELM in fibrosarcoma cells, whereas in breast adenocarcinoma cells 1 µM sodium selenite slightly increased expression and 10 µM sodium selenite significantly (approximately 2 times) decreased it. Methylseleninic acid in both cancer cell lines increased the SELM gene expression; the most pronounced effect was observed when fibrosarcoma cells were treated with 10 µM MSA (the expression of the hSelm gene increased almost 4 times).

[Effect of Sodium Selenite on Gene Expression of SELF, SELW, and TGR Selenoproteins in Adenocarcinoma Cells of the Human Prostate].

Selenium is an essential trace element, the deficiency of which leads to the development of several serious diseases, including male infertility, prostate cancer, etc. It has been shown that oxidative stress contributes to the progression of prostate cancer, and antioxidants such as selenium and vitamin E can significantly reduce the risk of this disease. Sodium selenite, one of the selenium compounds that induce the formation of reactive oxygen species, is considered as a potential anticancer agent. The SS concentrations that lead to a decrease in the viability of human prostate adenocarcinoma cells (line Du-145) have been selected, and the effect of sodium selenite on the expression of mRNA of the SELV, SELW, and TGR selenocysteine proteins in these cells has been analyzed.

Influence of Sodium Selenite on the mRNA Expression of the Mammalian Selenocysteine-Containing Protein Genes in Testicle and Prostate Cancer Cells.

The sodium selenite concentration that reduces the viability of Du-145 human prostate adenocarcinoma cells and F-9 mouse testicular teratocarcinoma cells was determined. We investigated the effect of sodium selenite on the mRNA expression level of the genes encoding mammalian selenocysteine-containing glutathione peroxidases and thioredoxin reductases (key antioxidant enzymes involved in the regulation of intracellular thiol redox balance), endoplasmic reticulum selenoproteins, and selenoproteins located in the testes and prostate.

Cloning, intracellular localization, and expression of the mammalian selenocysteine-containing protein SELENOI (SelI) in tumor cell lines.

The intracellular localization of human selenoprotein SelI and the degree of expression of its gene in different human tumor cell lines were determined. It was found that the SelI protein is present in the nucleus, cytoplasm, and endoplasmic reticulum and is absent in the nucleolus. Since the oxidative stress caused by a sharp increase in the content of free radicals in the body is one of the causes of malignant transformation, the study of the role of the trace element selenium and selenocysteine-containing proteins as antioxidants in carcinogenesis is of great scientific interest.

Expression of human selenoprotein genes selh, selk, selm, sels, selv, and gpx-6 in various tumor cell lines.

The expression level of the genes encoding six selenocysteine-containing human proteins was determined in the brain, cervical, liver, breast, prostate, and human fibrosarcoma cancer cells. It was found that a high level of expression in all studied types genes of tumor cells is characteristic for selh, selk, and selm genes, encoding SelH, SelK, and SelM proteins, respectively, whereas a complete lack of such expression was shown for gpx-6, selv, and sels genes. The results of this work can be regarded as a major prerequisite for further studies on the role of the three selenoproteins SelH, SelK, and SelM in the regulation of carcinogenesis processes associated with these types of cancer.