RAF may induce cell proliferation through hypermethylation of tumor suppressor gene promoter in gastric epithelial cells

Xingbi Gel Ameliorates Allergic Rhinitis by Regulating IFN-γ Gene Promoter Methylation in CD4+ T Cells via the ERK-DNMT Pathway

Allergic rhinitis (AR) is a common, non-infectious, chronic nasal mucosal disease primarily mediated by immunoglobulin E (IgE) following allergen exposure. Currently, studies on AR mainly focus on cytokines, IgE and its receptors, basophils, eosinophils, mast cells, and related genes. Among these, an imbalance between T helper (Th) 1 and Th2 cells is considered an important mechanism underlying AR pathogenesis. The most important cytokines in AR are interleukin (Il)-4 and interferon gamma (IFN-γ) which are secreted by Th2 and Th1 cells, respectively. Il-4 and IFN-γ are antagonistic to each other in regulating IgE synthesis. In this study, the expression of extracellular signal-regulated protein kinase (ERK) 1/2 and its phosphorylation from p-ERK1/2, were significantly increased in a cluster of differentiation of 4+ T cells of AR mice, suggesting that the ERK signaling pathway in these cells is involved in the occurrence and development of AR. This result also implies an enhanced expression of deoxyribonucleic acid methyltransferases (DNMTs). To verify the relationship between ERK signaling and DNMT expression, AR mice were treated with PD98059, a specific inhibitor of the ERK1/2 signaling pathway. The results revealed that perturbations in ERK signaling were significantly positively correlated with the downregulation of DNMT1 expression. Pharmacological intervention is key to treating AR. This study demonstrated that Xingbi gel intervention affected both serum IgE levels and AR behavior scores in mice. Based on its effects on IFN-γ gene expression, the regulation of Th1/Th2 balance, and the ERK signaling pathway, research on the effects of Xingbi gel on AR may provide new avenues in its prevention and treatment.

RN181 is a tumour suppressor in gastric cancer by regulation of the ERK/MAPK-cyclin D1/CDK4 pathway

RN181, a RING finger domain-containing protein, is an E3 ubiquitin ligase. However, its biological function and clinical significance in cancer biology are obscure. Here, we report that RN181 expression is significantly down-regulated in 165 tumour tissues of gastric carcinoma (GC) versus adjacent non-tumour tissues, and inversely associated with tumour differentiation, tumour size, clinical stage, and patient's overall survival. Alterations of RN181 expression in GC cells by retrovirus-transduced up-regulation and down-regulation demonstrated that RN181 functions as a tumour suppressor to inhibit growth of GC in both in vitro culture and in vivo animal models by decreasing tumour cell proliferation and increasing tumour cell apoptosis. Cell cycle analysis revealed that RN181 controls the cell cycle transition from G1 to S phase. Mechanistic studies demonstrated that RN181 inhibits ERK/MAPK signalling, thereby regulating the activity of cyclin D1-CDK4, and consequently controlling progression in the cell cycle from G1 to S phase. Restoring CDK4 in GC cells rescued the inhibitory phenotype produced by RN181 in vitro and in vivo, suggesting a dominant role of CDK4 in control of the tumour growth by RN181. Importantly, RN181 expression is inversely correlated with the expression of cyclin D1 and CDK4 in GC clinical samples, substantiating the role of the RN181-cyclin D1/CDK4 pathway in control of the tumour growth of GC. Our results provide new insights into the pathogenesis and development of GC and rationale for developing novel intervention strategies against GC by disruption of ERK/MAPK-cyclin D1/CDK4 signalling. In addition, RN181 may serve as a novel biomarker for predicting clinical outcome of GC. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Anti-invasion and anti-metastasis effects of Valjatrate E via reduction of matrix metalloproteinases expression and suppression of MAPK/ERK signaling pathway

Valjatrate E is an iridoid compound extracted from Valeriana jatamansi Jones herb and is the active ingredient in antitumor activity. Here, we reported its action on tumor invasion and metastasis in the human hepatocellular carcinoma HepG2, aiming at a better understanding of the potential mechanism of action of Valjatrate E. HepG2 cells were treated with Valjatrate E at different concentrations. Wound healing assay and transwell chamber assay were used to determine the effects of Valjatrate E on the migration and invasiveness of HepG2 cells, respectively. Moreover, homogeneity and heterotypic adhesion experiments evaluated the adhesion property of HepG2 cells. The molecular mechanisms by which Valjatrate E inhibited the invasion and migration of HepG2 cells were investigated by gelatin zymography experiment and western blot. Treatment with Valjatrate E inhibited the migration and invasion of HepG2 cells. It achieved this by reducing the expression of matrix metalloprotease 2 (MMP-2) and matrix metalloprotease 9 (MMP-9), by inhibition of heterogeneous adhesion ability, by blocking mitogen-activated protein kinase (MAPK) signaling via inhibiting the phosphorylation of extracellular signal-regulated kinases (p-ERK). Taken together, these findings provide new evidence that mitogen-activated protein kinase/extracellular signal regulated kinase (MAPK/ERK) signaling pathway plays an important role in promoting invasion and metastasis in HepG2 cells through p-ERK, and MAPK/ERK signaling pathway may be a therapeutic target for tumor.

BRD4 regulates cellular senescence in gastric cancer cells via E2F/miR-106b/p21 axis

Small molecules targeting bromodomains of BET proteins possess strong anti-tumor activities and have emerged as potential therapeutics for cancer. However, the underlying mechanisms for the anti-proliferative activity of these inhibitors are still not fully characterized. In this study, we demonstrated that BET inhibitor JQ1 suppressed the proliferation and invasiveness of gastric cancer cells by inducing cellular senescence. Depletion of BRD4, which was overexpressed in gastric cancer tissues, but not other BET proteins recapitulated JQ1-induced cellular senescence with increased cellular SA-β-Gal activity and elevated p21 levels. In addition, we showed that the levels of p21 were regulated at the post-transcriptional level by BRD4-dependent expression of miR-106b-5p, which targets the 3'-UTR of p21 mRNA. Overexpression of miR-106b-5p prevented JQ1-induced p21 expression and BRD4 inhibition-associated cellular senescence, whereas miR-106b-5p inhibitor up-regulated p21 and induced cellular senescence. Finally, we demonstrated that inhibition of E2F suppressed the binding of BRD4 to the promoter of miR-106b-5p and inhibited its transcription, leading to the increased p21 levels and cellular senescence in gastric cancer cells. Our results reveal a novel mechanism by which BRD4 regulates cancer cell proliferation by modulating the cellular senescence through E2F/miR-106b-5p/p21 axis and provide new insights into using BET inhibitors as potential anticancer drugs.

Decitabine inhibits tumor cell proliferation and up-regulates e-cadherin expression in Epstein-Barr virus-associated gastric cancer

The present study investigated the effect of a DNA demethylating agent, decitabine, against Epstein-Barr virus-associated gastric cancer (EBVaGC). Decitabine inhibited cell growth and induced G2/M arrest and apoptosis in EBVaGC cell lines. The expression of E-cadherin was up-regulated and cell motility was significantly inhibited in the cells treated with decitabine. The promoter regions of p73 and RUNX3 were demethylated, and their expression was up-regulated by decitabine. They enhanced the transcription of p21, which induced G2/M arrest and apoptosis through down-regulation of c-Myc. Decitabine also induced the expression of BZLF1 in SNU719. Induction of EBV lytic infection was an alternative way to cause apoptosis of the host cells. This study is the first report to reveal the effectiveness of a demethylating agent in inhibiting tumor cell proliferation and up-regulation of E-cadherin in EBVaGC. J. Med. Virol. 89:508-517, 2017. © 2016 Wiley Periodicals, Inc.

Effects of radix curcumae-derived diterpenoid C on Helicobacter pylori-induced inflammation and nuclear factor kappa B signal pathways

AIM: To study effect of diterpenoid C extracted from radix curcumae on Helicobacter pylori (H. pylori)-infected inflammation, intestinal metaplasia, and nuclear factor kappa B (NF-κB) signaling pathway in vitro.

METHODS: We used I-type H. pylori to infect human gastric epithelial gastric epithelium cell line (GES-1) cell lines, and then H. pylori-infected GES-1 cells were treated with radix curcumae (RC)-derived diterpenoid C of different concentrations (5, 10, 20 μg/mL) and amoxicillin. The expression of p65, IκB kinase (IKK) α and IKKγ proteins was detected with Western blotting, and the expression of interleukin (IL)-8, IL-6 and IL-4 was determined with enzyme-linked immunosorbent assay method. Data were analyzed using SPSS software ver18.0. For comparisons between groups of more than two unpaired values, one-way analysis of variance (ANOVA) was used. If an ANOVA F value was significant, post hoc comparisons were performed between groups. If results were not normally distributed, the Mann-Whitney U test was used to compare two groups of unpaired values, whereas for comparisons between groups of more than two unpaired values, the Kruskal-Wallis H test was used. Statistical significance was established at P < 0.05.

RESULTS: The MTT assay results revealed the inhibited rate of GES-1, and indicated that the IC5 of RC-derived diterpenoid C and amoxicillin all were 5 μg/mL for gastric GES-1 cells. The expression of IL-8 was significantly increased, especially at 12 h time point; and the expression of IL-4 was decreased in H. pylori-infected GES-1 cells. After H. pylori-infected GES-1 cells were treated with RC-derived diterpenoid C of different concentrations and amoxicillin, the expression of IL-8 was decreased at 12, 24, 48, 72 h points (P < 0.01), especially in high-concentration diterpenoid C (20 μg/mL) group; and the expression of IL-4 was increased, especially in moderate and high-concentration diterpenoid C (10 and 20 μg/mL) groups. RC-derived diterpenoid C had the inhibitory effects on H. pylori-induced p65 translocation from cytoplasm into cell nucleus, H. pylori-stimulant IkBα degradation, the phosphorylation of p65 and IkBα, and the expression of IKKα and IKKβ proteins.

CONCLUSION: RC-derived diterpenoid C can block NF-κB signal pathway, effectively reducing the secretion of H. pylori-induced proinflammatory cytokine and increasing the secretion of anti-inflammatory cytokine.

TGF-β mediated DNA methylation in prostate cancer

Almost all tumors harbor a defective negative feedback loop of signaling by transforming growth factor-β (TGF-β). Epigenetic mechanisms of gene regulation, including DNA methylation, are fundamental to normal cellular function and also play a major role in carcinogenesis. Recent evidence demonstrated that TGF-β signaling mediates cancer development and progression. Many key events in TGF-β signaling in cancer included auto-induction of TGF-β1 and increased expression of DNA methyltransferases (DNMTs), suggesting that DNA methylation plays a significant role in cancer development and progression. In this review, we performed an extensive survey of the literature linking TGF-β signaling to DNA methylation in prostate cancer. It appeared that almost all DNA methylated genes detected in prostate cancer are directly or indirectly related to TGF-β signaling. This knowledge has provided a basis for our future directions of prostate cancer research and strategies for prevention and therapy for prostate cancer.

Apoptosis signal-regulating kinase 1 and cyclin D1 compose a positive feedback loop contributing to tumor growth in gastric cancer

Mitogen-activated protein kinase (MAPK) pathways regulate multiple cellular functions and are highly active in many types of human cancers. Apoptosis signal-regulating kinase 1 (ASK1) is an upstream MAPK involved in apoptosis, inflammation, and carcinogenesis. This study investigated the role of ASK1 in the development of gastric cancer. In human gastric cancer specimens, we observed increased ASK1 expression, compared to nontumor epithelium. Using a chemically induced murine gastric tumorigenesis model, we observed increased tumor ASK1 expression, and ASK1 knockout mice had both fewer and smaller tumors than wild-type (WT) mice. ASK1 siRNA inhibited cell proliferation through the accumulation of cells in G1 phase of the cell cycle, and reduced cyclin D1 expression in gastric cancer cells, whereas these effects were uncommon in other cancer cells. ASK1 overexpression induced the transcription of cyclin D1, through AP-1 activation, and ASK1 levels were regulated by cyclin D1, via the Rb-E2F pathway. Exogenous ASK1 induced cyclin D1 expression, followed by elevated expression of endogenous ASK1. These results indicate an autoregulatory mechanism of ASK1 in the development of gastric cancer. Targeting this positive feedback loop, ASK1 may present a potential therapeutic target for the treatment of advanced gastric cancer.