Ectopic ERK expression induces phenotypic conversion of C10 cells and alters DNA methyltransferase expression

Amentoflavone induces apoptosis and suppresses glycolysis in glioma cells by targeting miR-124-3p

Malignant glioma is the most common type of brain tumor with poor clinical outcome and survival. Therefore, it is imperative to develop novel therapeutic agents for managing glioma. The aim of this study was to investigate the role of amentoflavone (AF), an active flavonoid component in Selaginella tamariscina Spring, in glioma cells and the underlying mechanism of its action. Our results showed that miR-124-3p expression was significantly down-regulated in glioma tissues relative to normal brain tissues. AF decreased cell viability and triggered apoptosis in both glioma cell lines in a dose-dependent manner. AF induced apoptosis and inhibited glycolysis in the glioma cells by upregulating miR-124-3p. Furthermore, AF upregulated miR-124-3p by repressing DNMT1 through Sp1, which in turn was caused by the activation of ROS/AMPK signaling pathway by AF. In conclusion, AF could induce apoptosis and inhibited glycolysis in glioma cells via miR-124-3p. Our findings provide preliminary experimental data that support further investigation on the therapeutic efficacy of AF in glioma.

Physcion induces apoptosis in hepatocellular carcinoma by modulating miR-370

Hepatocellular carcinoma (HCC) is one of the most common and aggressive malignancies. The current study is designed to explore the role of physcion, a major active ingredient in several traditional herbal medicinal plants, for the treatment of HCC. HCC cell lines, SMMC7721 and HepG2, were treated with physcion and its apoptosis-inducing effect was examined. Both in vitro and in vivo results from the present study demonstrated that physcion treatment resulted in apoptotic cell death in HCC cells via upregulation of miR-370. Furthermore, our findings showed that the physcion modulated the level of miR-370 through AMPK/Sp1/DNMT1 signaling. Taken together, these results showed that physcion exerts anti-tumor effect against HCC, which may be a potential agent for the adjunct chemotherapy.

RETRACTED: Physcion 8-O-β-glucopyranoside induces apoptosis, suppresses invasion and inhibits epithelial to mesenchymal transition of hepatocellular carcinoma HepG2 cells

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Panels from Figure 4A appear similar to panels from Figure 1 of the article previously published by Z. Ding, F. Xu, J. Tang, G. Li, P. Jiang, Z. Tang and H. Wu in Neoplasma 63(3) (2016) 351–361 http://www.elis.sk/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=4703&category_id=128&option=com_virtuemart&vmcchk=1&Itemid=1. One of the conditions of submission of a paper for publication is that authors declare explicitly that the paper has not been previously published and is not under consideration for publication elsewhere. Re-use of any data should be appropriately cited. As such this article represents a misuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

The role and regulatory mechanism of IL-1β on the methylation of the NF2 gene in benign meningiomas and leptomeninges

Methylation of the neurofibromatosis type 2 (NF2) gene in low-grade meningioma (WHO grade I) has crucial roles in tumorigenesis and development. Meningioma formation might also occur in the setting of an inflammatory microenvironment. However, the association between inflammation and the methylation of NF2 remains unclear. The present study investigates the role and regulatory mechanism of IL-1β, one of the most important pro-inflammatory cytokines, in the methylation of NF2 in benign meningioma. Three primary low-grade meningioma cells and leptomeningeal cells were cultured. CCK-8 and BrdU assays demonstrated that proliferation of meningioma/leptomeningeal cells treated with IL-1β occurred in a dose- and time-dependent manner. Methylation-specific PCR verified that IL-1β induced methylation of the NF2 promoter and decreased NF2/merlin expression in meningioma/leptomeningeal cells. Real-time PCR, western blotting, and immunofluorescence showed that IL-1β up-regulated DNMT1 in meningioma cells and DNMT1/3b in leptomeningeal cells but did not up-regulate DNMT3a. After co-treatment with the DNMT inhibitor 5-Aza-2'-deoxycytidine and DNMT siRNA, methylation of NF2 induced by IL-1β was attenuated and merlin expression was restored. Furthermore, we showed that DNMT1 in meningiomas and DNMT1/3b in leptomeninges were regulated via activation of the MAPK (p38, ERK, JNK) and NF-κB pathways. These results suggest that IL-1β induces methylation of NF2 by up-regulating DNMT1 in benign meningioma cells and DNMT1/3b in leptomeningeal cells via MAPK and NF-κB pathways. Therefore, NF2 methylation is a linker between IL-1β and tumor development, and DNMTs might be potential therapeutic targets in meningioma for regulating NF2 and inhibiting tumor development. © 2016 Wiley Periodicals, Inc.

Ursolic acid inhibited growth of hepatocellular carcinoma HepG2 cells through AMPKα-mediated reduction of DNA methyltransferase 1

Hepatocellular carcinoma (HCC), the major histological subtype of primary liver cancer, remains one of the most common malignancies worldwide. Due to the complicated pathogenesis of this malignancy, the outcome for comprehensive treatment is limited. Chinese herbal medicine (CHM) is emerging as a promising choice for its multi-targets and coordinated intervention effects against HCC. Ursolic acid (UA), a natural pentacyclic triterpenoid carboxylic acid found in CHM, exerts anti-tumor effects and is emerging as an effective compound for cancer prevention and therapy. However, the molecular mechanisms underlying the action of UA remain largely unknown. In this study, we showed that UA inhibited the growth of HCC cells and induced apoptosis in the dose- and time-dependent fashion. Furthermore, we found that UA induced phosphorylation of AMP-activated protein kinase alpha (AMPKα) and suppressed the protein expression of DNA methyltransferase 1 (DNMT1) in the dose-dependent manner. The inhibitor of AMPK, compound C blocked, while an activator of AMPK, metformin augmented the effect of UA on DNMT1 expression. In addition, UA suppressed the expression of transcription factor Sp1. Conversely, overexpression of Sp1 reversed the effect of UA on DNMT1 expression and cell growth. Collectively, our results show for the first time that UA inhibits growth of HCC through AMPKα-mediated inhibition of Sp1; this in turn results in inhibition of DNMT1. This study reveals a potential novel mechanism by which UA controls growth of HCC cells and suggests that DNMT1 could be novel target for HCC chemoprevention and treatment.

β-elemene inhibited expression of DNA methyltransferase 1 through activation of ERK1/2 and AMPKα signalling pathways in human lung cancer cells: the role of Sp1

β-elemene, a compound derived from Rhizoma zedoariae, is a promising new plant-derived drug with broad-spectrum anticancer activity. However, the underlying mechanism by which this agent inhibits human lung cancer cell growth has not been well elucidated. In this study, we showed that β-elemene inhibits human non-small cell lung carcinoma (NSCLC) cell growth, and increased phosphorylation of ERK1/2, Akt and AMPKα. Moreover, β-elemene inhibited expression of DNA methyltransferase 1 (DNMT1), which was not observed in the presence of the specific inhibitors of ERK (PD98059) or AMPK (compound C). Overexpression of DNMT1 reversed the effect of β-elemene on cell growth. Interestingly, metformin not only reversed the effect of β-elemene on phosphorylation of Akt but also strengthened the β-elemene-reduced DNMT1. In addition, β-elemene suppressed Sp1 protein expression, which was eliminated by either ERK1/2 or AMPK inhibitor. Conversely, overexpression of Sp1 antagonized the effect of β-elemene on DNMT1 protein expression and cell growth. Taken together, our results show that β-elemene inhibits NSCLC cell growth via ERK1/2- and AMPKα-mediated inhibition of transcription factor Sp1, followed by reduction in DNMT1 protein expression. Metformin augments the effect of β-elemene by blockade of Akt signalling and additively inhibition of DNMT1 protein expression. The reciprocal ERK1/2 and AMPKα signalling pathways contribute to the overall responses of β-elemene. This study reveals a potential novel mechanism by which β-elemene inhibits growth of NSCLC cells.

Long-term exposure to cigarette smoke extract induces hypomethylation at the RUNX3 and IGF2-H19 loci in immortalized human urothelial cells

Cigarette smoking is the single most important epidemiological risk factor for bladder cancer but it is not known whether exposure of urothelial cells to the systemic soluble contents of cigarette smoke is directly causative to bladder cancer and the associated epigenetic changes such as tumor suppressor gene hypermethylation. We undertook this study to investigate if long-term treatment of human urothelial cells with cigarette smoke extract (CSE) results in tumor suppressor gene hypermethylation, a phenotype that was previously associated with long-term constant CSE treatment of airway epithelial cells. We chronically treated an immortalized human urothelial cell line UROtsa with CSE using a cyclic daily regimen but the cells were cultured in CSE-free medium between daily treatments. Bisulfite sequencing and real-time PCR array-based methylation profiling were employed to evaluate methylation changes at tumor suppressor gene loci in the chronically CSE-treated cells versus the passage-matched untreated control cells. The RUNX3 tumor suppressor gene promoter was hypomethylated with a significant increase in proportion of the completely unmethylated haplotype after the long-term CSE treatment; whereas RUNX3 promoter hypermethylation was previously reported for bladder cancers of smokers. Hypomethylation induced by the long-term CSE treatment was also observed for the IGF2-H19 locus. The methylation status at the PRSS8/prostasin and 16 additional loci however, was unaffected by the chronic CSE treatment. Transient CSE treatment over 1 daily regimen resulted in transcriptional down-regulation of RUNX3 and H19, but only the H19 transcription was down-regulated in the chronically CSE-treated urothelial cells. Transcription of a key enzyme in one-carbon metabolism, dihydrofolate reductase (DHFR) was greatly reduced by the long-term CSE treatment, potentially serving as a mechanism for the hypomethylation phenotype via a reduced supply of methyl donor. In conclusion, chronic cyclic CSE treatment of urothelial cells induced hypomethylation rather than hypermethylation at specific loci.

Characterization and transcriptional regulation of Stachybotrys elegans mitogen-activated-protein kinase gene smkA following mycoparasitism and starvation conditions

Mitogen-activated protein kinase (MAPK) signaling pathways play an important role in the development and conidiation of fungal pathogens on their hosts and the sensing of host-derived cues. Mycoparasitism is a fungus-fungus interaction comprising host-pathogen cross talk. Until now, only little information is available on the role of the MAPK signaling pathway during this interaction. Here, we report on the differential expression of a MAPK/ERK gene in the mycoparasite Stachybotrys elegans in response to direct parasitism of different vegetative structures of the plant pathogen Rhizoctonia solani (i.e., carbon-rich condition) and to nutrient starvation (i.e., carbon-poor condition). Western blot analysis against ERK1/2 highlighted an increase in their phosphorylated forms when S. elegans was grown under starvation condition compared to that detected in response to mycoparasitism. A higher abundance of phosphorylated ERK1/2 at the third day of interaction compared to that estimated under starvation condition was detected applying LC-MS/MS. At the transcriptional level, smkA, a YERK1 class member, was significantly induced in response to hyphal parasitism compared to parasitized sclerotia at 3, 4, and 5 days of interaction. However, under starvation condition, smkA levels were significantly induced after 7 days of growth. Southern blot analysis revealed that smkA is member of a small gene family. Collectively, these results suggest that smkA could be implicated in the mycoparasitic process in S. elegans as well as in stress-activated pathways. These results may be of wider significance in other fungus-fungus interactions.