Celastrol induces cell cycle arrest by MicroRNA-21-mTOR-mediated inhibition p27 protein degradation in gastric cancer.

OBJECTIVE: Celastrol has anti-cancer effects by increase of apoptosis of gastric cancer cells. However, its role in gastric cancer cell cycle is still unclear. The aim of this study was to investigate the effect and mechanism of celastrol on gastric cancer cell cycle. METHODS: The effects of celastrol on cell cycle in BGC-823 and MGC-803 cells were assayed via flow cytometry analysis. The expression of p27 and mTOR was detected by real-time PCR and western blot. The activity of mTOR and mTORC2 was measured by mTOR and mTORC2 kinase assays. miR-21 mimic was used to up-regulate miR-21 expression and mTOR expression plasmid was used to increase mTOR level in gastric cancer cells. RESULTS: Celastrol caused G2/M cell-cycle arrest that was accompanied by the down-regulation of miR-21 expression. In particular, miR-21 overexpression reversed cell cycle arrest effects of celastrol. Further study showed that celastrol increased levels of the p27 protein by inhibiting its degradation. miR-21 and mTOR signaling pathway was involved in the increase of p27 protein expression in BGC-823 and MGC-803 cells treated with celastrol. Significantly, miR-21 overexpression restored the decrease of mTOR activity in cells exposed celastrol. CONCLUSIONS: The effect of celastrol on cell cycle arrest of gastric cancer cells was due to an increase of p27 protein level via inhibiting miR-21-mTOR signaling pathway.

Artesunate exerts an anti-immunosuppressive effect on cervical cancer by inhibiting PGE2 production and Foxp3 expression.

Artesunate (ART), derived from a common traditional Chinese medicine, has beeen used an antimalarial for several years. In this study, the effect and mechanism of ART on anti-human cervical cancer cells was examined. The level of prostaglandin E2 (PGE2 ) and the population of CD4+CD25+Foxp3 regulatory T cells (Treg) in peripheral blood were detected by flow cytometry. In vivo antitumor activity was investigated in mice with cervical cancer by the subcutaneous injection of various concentrations of ART. The concentrations of PGE2 in the supernatants of CaSki cells were measured using an ELISA kit. Cyclooxygenase-2 (COX-2) and Foxp3 expression were determined using quantitative polymerase chain reaction (qPCR) and western blot analysis. The effect of ART on the viability of CaSki and Hela cells was evaluated with a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. It was identified that the level of PGE2 and the population of CD4+CD25+Foxp3 Treg cells in the peripheral blood were significantly higher in cervical cancer patients and mice with cervical cancer. ART was capable of inhibiting orthotopic tumor growth, which correlated with a decrease in the level of PGE2 and the percentage of Treg cells in mice with cervical cancer. Furthermore, ART decreased COX-2 expression and the production of PGE2 in CaSki and Hela cells. Notably, the supernatants of CaSki cells treated with ART lowered the expression of Foxp3 in Jurkat T cells, which was capable of being reversed by exogenous PGE2 . Our data revealed that ART may elicit an anti-tumor effect against cervical cancer by inhibition of PGE2 production in CaSki and Hela cells, which resulted in the decrease of Foxp3 expression in T cells. Therefore, ART may be an effective drug for immunotherapy of cervical cancer.

Celastrol induces apoptosis of gastric cancer cells by miR-21 inhibiting PI3K/Akt-NF-κB signaling pathway.

OBJECTIVE: Celastrol, a plant triterpene, has anticancer effects by increase of apoptosis. In the present study, the mechanism of celastrol on gastric cancer cell apoptosis was examined. METHODS: The effect of celastrol on PI3K/Akt and the NF-κB signaling pathway was evaluated with Western blot and luciferase reporter assay. miR-21 expression was determined using real-time PCR. miR-21 inhibitor and miR-21 mimic were used to downregulate and upregulate miR-21 expression, respectively. RESULTS: It was identified that celastrol was capable of inducing apoptosis of gastric cancer cells, which was mediated via inhibiting the activation of PI3K/Akt and NF-κB. A strong activator of Akt, IGF-1 restored NF-κB activity in cells treated with celastrol. Celastrol could also significantly suppress miR-21 expression. Furthermore, miR-21 inhibitor could decrease phospho-Akt expression and NF-κB activity. Notably, upregulation of miR-21 expression can increase PI3K/Akt and NF-κB activity and decrease apoptosis of gastric cancer cells treated with celastrol, which could be reversed by PI3K inhibitor. CONCLUSIONS: Our data revealed that the effect of celastrol on apoptosis was due to miR-21 inhibiting the PI3K/Akt-dependent NF-κB pathway.

Celastrol induces apoptosis of gastric cancer cells by miR-146a inhibition of NF-κB activity.

BACKGROUND: Celastrol, a plant triterpene, is known to play important role in inhibiting proliferation and inducing apoptosis of gastric cancer cells. In the present study, the mechanism of celastrol on gastric cancer cells apoptosis was examined. METHODS: We assessed effect of celastrol on NF-κB signaling pathway in gastric cancer cells using western blot and luciferase reporter assay. The real-time PCR was used to evaluate the effect of celastrol on miR-146a expression, and miR-146a mimic to evaluate whether over-expression of miR-146a can affect NF-κB activity. Finally, the effect of miR-146a on celastrol-induced anti-tumor activity was assessed using miR-146a inhibitor. RESULTS: Celastrol decreased gastric cancer cells viability in a dose-dependent. Celastrol also reduced IκB phosphorylation, nuclear P65 protein levels and NF-κB activity. Furthermore, Celastrol could increase miR-146a expression and up-regulation of miR-146a expression could suppress NF-κB activity. More important, down-regulation of miR-146a expression can reverse the effect of celastrol on NF-κB activity and apoptosis in gastric cancer cells. CONCLUSIONS: In this study, we demonstrated that the effect of celastrol on apoptosis is due to miR-146a inhibition of NF-κB activity.