FOXO signaling pathway participates in oxidative stress-induced histone deacetylation.

High concentrations of antioxidants can exert pro-oxidative effects, elevate the level of intracellular reactive oxygen species (ROS), and cause oxidative stress in cells. We previously found that high concentrations of curcumin, a natural polyphenol antioxidant, elevated ROS levels and upregulated the expression of histone deacetylase 1 (HDAC1) in human gastric cancer cells (hGCCs); however, its potential mechanisms and subsequent functions have not been elucidated. In the present study, we treated hGCCs with high concentrations of curcumin, detected several indicators of oxidative stress, and investigated the mechanism of curcumin-treatment-mediated HDAC1 upregulation and its effect on histone acetylation. The results showed that curcumin treatment caused oxidative stress in hGCCs and upregulated HDAC1/2 expression via the forkhead box O (FOXO) signaling pathway, ultimately leading to the deacetylation of histones in hGCCs. Moreover, HDAC1/2 mediates the deacetylation of FOXOs and promotes their transcription activities, implying a positive feedback loop between FOXOs and HDAC1/2. These findings present a mechanism by which oxidative stress induces histone deacetylation in hGCCs.

The miR-302s/367 Cluster Inhibits the Proliferation and Apoptosis in Sheep Fetal Fibroblasts via the Cell Cycle and PI3K-Akt Pathways.

The miR-302s/367 family has the ability to induce mouse and human somatic cell reprogramming into induced pluripotent stem cells (iPSCs), inhibit the proliferation of several types of cancer cells, and even cause cancer cell apoptosis. However, the functions of the miR-302s/367 family in other mammals have not been explored. In the present study, the effects of miR-302s/367 on reprogramming, proliferation, and apoptosis in sheep fetal fibroblasts (SFFs) were evaluated by the delivery of a plasmid vector containing synthetic precursor miRNAs into cells, followed by the induction of mature miR-302s/367 expression. The results showed that miR-302s/367 could not reprogram SFFs into iPSCs; however, they could inhibit both the proliferation and apoptosis of SFFs by targeting CDK2, E2F1, E2F2, and PTEN in the cell cycle and PI3K-Akt pathways. Based on our findings, a novel mechanism was proposed in which the miR-302s/367 family functions in both the proliferation and apoptosis of somatic cells in mammals, suggesting that caution is needed when using miR-302s/367 as therapeutic agent.

c-Met/MAPK pathway promotes the malignant progression of residual hepatocellular carcinoma cells after insufficient radiofrequency ablation.

Radiofrequency ablation (RFA) is popularly used in the treatment of hepatocellular carcinoma (HCC). However, the accelerated malignant progression of residual HCC cells after RFA is the main obstacle for the application of this technology in HCC treatment. In the present study, HepG2 cells, an established human HCC cell line, experienced repeatedly with heat treatment, survived cells, HepG2-H cells, were used to simulate residual HCC cells after RFA. The abilities of proliferation, colony formation, and migration were compared between HepG2 and HepG2-H cells. Then, RNA sequencing was used to explore the difference in genes expression between two groups of cells. Subsequently, the level of c-Met, one of membranous receptors of MAPK signal pathway, was measured by RT-qPCR and western blot; the effect of c-Met inhibition on the malignant progression of HepG2-H cells was evaluated. The results showed that HepG2-H cells exhibited higher abilities in the proliferation, colony formation, and migration than that of HepG2 cells. Moreover, differentially expressed genes between two groups of cells were prominently enriched in MAPK signal pathway. The level of c-Met in HepG2-H cells was significantly higher than that in HepG2 cells, and the inhibition in the activity of c-Met could repress the malignant behaviors of HepG2-H cells. These results indicated that the accelerated malignant progression of residual HCC cells after RFA can be partly attributed to the overexpression of c-Met and the activation of MAPK signal pathway. Therefore, we proposed that RFA followed by c-Met inhibitor intake maybe is a better treatment protocol for HCC.

Curcumin-Induced DNA Demethylation in Human Gastric Cancer Cells Is Mediated by the DNA-Damage Response Pathway.

Curcumin, a natural polyphenol antioxidant extracted from the root of turmeric (Curcuma longa), can induce apoptosis and DNA demethylation in several types of cancer cells. However, the mechanism of its anticancer potentials and DNA demethylation effects and the potential relationships between these outcomes have not been clearly elucidated. In the present study, the effects of curcumin on the proliferation, colony formation, and migration of human gastric cancer cells (hGCCs) were explored. Reactive oxygen species (ROS) levels, mitochondrial damage, DNA damage, and apoptosis of curcumin-treated hGCCs were analyzed. Changes in the expression of several genes related to DNA damage repair, the p53 pathway, cell cycle, and DNA methylation following curcumin treatment were also evaluated. We observed that curcumin inhibited the proliferation, colony formation, and migration of hGCCs in a dose- and time-dependent fashion. A high concentration of curcumin elevated ROS levels and triggered mitochondrial damage, DNA damage, and apoptosis of hGCCs. Further, curcumin-induced DNA demethylation of hGCCs was mediated by the damaged DNA repair-p53-p21/GADD45A-cyclin/CDK-Rb/E2F-DNMT1 axis. We propose that the anticancer effect of curcumin could largely be attributed to its prooxidative effect at high concentrations and ROS elevation in cancer cells. Moreover, we present a novel mechanism by which curcumin induces DNA demethylation of hGCCs, suggesting the need to further investigate the demethylation mechanisms of other DNA hypomethylating drugs.