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Abstract Background Previous studies demonstrated that selenite induced cancer-cell apoptosis through multiple mechanisms; however, effects of selenite on microtubules in leukemic cells have not been demonstrated. Methods The toxic effect of selenite on leukemic HL60 cells was performed with cell counting kit 8. Selenite effects on cell cycle distribution and apoptosis induction were determined by flow cytometry. The contents of cyclin B1, Mcl-1, AIF, cytochrome C, insoluble and soluble tubulins were detected with western blotting. Microtubules were visualized with indirect immunofluorescence microscopy. The interaction between CDK1 and Mcl-1 was assessed with immunoprecipitation. Decreasing Mcl-1 and cyclin B1 expression were carried out through siRNA interference. The alterations of Mcl-1 and cyclin B1 in animal model were detected with either immunohistochemical staining or western blotting. In situ detection of apoptotic ratio was performed with TUNEL assay. Results Our current results showed that selenite inhibited the growth of HL60 cells and induced mitochondrial-related apoptosis. Furthermore, we found that microtubule assembly in HL60 cells was altered, those cells were arrested at G2/M phase, and Cyclin B1 was up-regulated and interacted with CDK1, which led to down-regulation of the anti-apoptotic protein Mcl-1. Finally, in vivo experiments confirmed the in vitro microtubule disruption effect and alterations in Cyclin B1 and Mcl-1 levels by selenite. Conclusions Taken together, the results from our study indicate that microtubules are novel targets of selenite in leukemic HL60 cells.

Thioredoxin is a ubiquitous dithioI oxidoreductase found in many organisms and involved in numerous biochemical processes. Human thioredoxin-like protein (hTRXL) is differentially expressed at different development stages of human fetal cerebrum and belongs to an expanding family of thioredoxins. Recombinant hTRXL and truncated hTRXLs corresponding to the N-terminal (hTRXLN) and C-terminal (hTRXL-C) domains are expressed and purified. In insulin disulfide reduction assay, both full-length hTRXL and hTRXL-N show reducing activity for the insulin disulfide bonds. As expected, the hTRXL-C failed to reduce insulin. MCF-7 cell stably transfected with hTRXL cDNA exhibits increased sensitivity to apoptosis induced by phorbol myristic acetate (PMA) and ionomysin. [ABSTRACT FROM AUTHOR]

Zika virus (ZIKV), a recently emerged member of the flavivirus family, forms replication compartments at the ER during its lifecycle. The proteins that are responsible for the biogenesis of replication compartments are not well defined. Here, we show that Zika nonstructural protein 1 (NS1)-induced ER remodeling is essential for viral replication. NS1 expressed in the ER lumen induced ER perinuclear aggregation with an ultrastructure resembling that of the replication compartment. Data from model membrane system indicated that the membrane-binding and membrane-remodeling properties of NS1 depend on its hydrophobic insertion into the membrane. These findings demonstrate that NS1 plays a crucial role in flavivirus replication compartment formation by remodeling the ER structure., (© 2019 Ci et al.)

Glutaminolysis is important for metabolism and biosynthesis of cancer cells, and GLS is essential in the process. Selenite is widely regarded as a chemopreventive agent against cancer risk. Emerging evidence suggests that it also has chemotherapeutic potential in various cancer types, but the mechanism remains elusive. We demonstrate for the first time that supranutritional dose of selenite suppresses glutaminolysis by promoting GLS1 protein degradation and apoptosis. Mechanistically, selenite promotes association of APC/C-CDH1 with GLS1 and leads to GLS1 degradation by ubiquitination, this process is related to induction of PTEN expression. In addition, GLS1 expression is increased in human colorectal cancer tissues compared with normal mucosae. Our data provide a novel mechanistic explanation for the anti-cancer effect of selenite from a perspective of cell metabolism. Moreover, our results indicate that glutaminolysis especially GLS1 could be an attractive therapeutic target in colorectal cancer.

In the present study, we aimed to investigate the relationship between autophagy and apoptosis in selenite‑treated colorectal cancer (CRC) cells. The effects of selenite on HCT116 and SW480 cell apoptosis were investigated with an Annexin V/propidium iodide (PI) double staining kit by flow cytometry. The punctate of LC3 protein following treatment with selenite was observed by a laser scanning confocal microscope and by transmission electron microscopy. Using western blot assays, we detected the apoptotic and autophagic markers in both CRC cells and mouse xenograft tumor models. We found that sodium selenite induced autophagy in the two CRC cell lines. Consistent with the in vitro results, we observed that the expression of autophagy marker LC3 was increased. Finally, we discovered that modulation of reactive oxygen species by MnTMPyP inhibited autophagy, while H2O2 activated autophagy. These results help to elucidate the anticancer effect of selenium, providing further evidence to exploit novel anticancer drugs targeting selenium.

Ahead of Print article withdrawn by publisher. The chemopreventive and chemotherapeutic effects of selenium compounds has been well validated in colorectal cancer by epidemiologic and pre-clinical studies, but the underlying mechanisms still remains elusive. We provide evidence that interaction between selenium metabolites and selenoproteins participates in colorectal cancer suppression induced by selenite. We found that supranutritional doses of selenite could induces inhibition of thioredoxin system and apoptosis in SW480 cells, and cause direct modifications of thiol groups on TrxR protein. Moreover, we showed that TrxR ablation sensitized apoptosis induced by selenite, and the synergistic effect was related to Bax activation and mitochondrial apoptotic pathway. Our results proposed that TrxR is an important target for selenite in colorectal cancer suppression, and selenite in combination with TrxR inhibition could be an effective strategy to treat colorectal cancer.

It was revealed by our previous research that sodium selenite repressed autophagy accompanied by the induction of apoptosis in human leukemia NB4 cells. The inhibition of autophagy exerted a facilitative effect on apoptosis. In the present study, we further explored the mechanisms underlying the switch from autophagy to apoptosis and elucidated p53 played a key role. Selenite induced phosphorylation of p53 at the vital site Ser15 via p38MAPK and ERK. Subsequently p53 dissociated with its inhibitory protein mouse double minute 2 (MDM2). Meanwhile, the nucleolar protein B23 transferred from the nucleolus to the nucleoplasm and associated with MDM2, probably stabilizing p53. The active p53 participated in the decrease of autophagic protein Beclin-1 and LC-3, as well as activation of apoptosis-related caspases. Furthermore, in p53 mutant U937 leukemia cells, selenite could not elicit such a switch from autophagy to apoptosis, laying emphasis on the crucial role p53 played in this process.

Our previous study has shown that sodium selenite can cause apoptosis in acute promyelocytic leukemia-derived NB4 cells in a caspase-dependent manner, but the detailed mechanism is unknown. Here we demonstrate a requirement for extracellular signal-regulated protein kinase (ERK) in mediating sodium selenite -induced apoptosis in NB4 cell. Though no apparent elevation of ERK activity was observed during the apoptosis in NB4 cells caused by 20 microM sodium selenite treatment, PD98059 and U0126, specific chemical inhibitors of the MEK/ERK signaling pathway, were shown to strongly prevent the apoptosis process, while ERK activator TPA enhanced the process. It is also known that p38 MAPK inhibitor SB203580 and JNK inhibitor SP600125 had slight effects on apoptosis. Further study indicated that ERK exerted its proapoptotic effect only at the early stage of apoptosis and played an antiapoptotic role at the later stages. Taken together, our findings suggest that ERK plays an active role in mediating sodium seleniteinduced apoptosis in NB4 cells.

To analyze the effect of Maltol on the apoptosis of Human Neuroblastoma Cells (SH-SY5Y) treated by free radical which was generated from Hydrogen Peroxide (H2O2), flow cytometry analysis on Phosphatidylserine (PS) inverting percentage was applied to determine the apoptosis. MTT (3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) assay was employed to analyze the cell viability. DNA electrophoresis was used to detect DNA fragmentation. Moreover intracellular calcium of concentration ([Ca2+]i) was measured by fluorescence emission. Flow cytometry analysis on the function of mitochondria and Western blot analysis of NF-kappaB. The results showed that the pretreatment with maltol for 2 hours could prevent the H2O2-induced apoptosis. Maltol could reduce the inverting percentage of PS, DNA fragmentation and [Ca2+]i, and enhance the cellular function of mitochondria. NF-kappaB activated by H2O2 is reduced. The experiments suggest that maltol could effectively inhibit the apoptosis induced by H2O2. As a novel anti-oxidant, maltol is a new promising drug in protecting the neurological cells from the damage by free radical.

Objective: To study the effects of low dose sodium selenite combined with all-trans retinoic acid (ATRA) on apoptosis and differentiation of human acute promyelocytic leukemia (APL) NB4 cells., Methods: Apo-ptosis was detected by translocation of phosphatidylserine (PS) with a Annexin-V kit and DNA fragmentation by agarose gel electrophoresis analysis, cell differentiation was studied by flow cytometry of CD(11b) expression and NBT reduction assay., Results: Five micromol/L sodium selenite or 0.1 micromol/L ATRA alone could not induce apoptosis of NB4 cells within 48 hours. However, combination of the two drugs at the same doses as above could induce significant apoptosis in 48 hours characterized by increased PS translocation and DNA ladder. Sodium selenite at concentration of 2 micromol/L was not able to induce differentiation of NB4 cells, but when combined with 0.1 micromol/L ATRA, CD(11b) expression and NBT reduction were increased as compared with that of 0.1 micromol/L ATRA alone., Conclusion: Low dose sodium selenite could enhance the effects of low dose ATRA in inducing apoptosis and differentiation of NB4 cells.