In situ, high-resolution measurement of labile phosphate in sediment porewater using the DET technique coupled with optimized imaging densitometry.

Obtaining two-dimensional distributions of reactive phosphorus in sediment porewater is very important for understanding fine-scale phosphorus mobilization and sequestration processes in sediments. In this study, the diffusive equilibrium in thin films (DET) measurement based on computer imaging densitometry (CID) was studied in detail with optimal conditions described. This study focuses on evaluating the two-dimensional colorimetric DET method coupled with CID (DET-CID method) for porewater labile phosphate measurements. The result shows that the red channel filter is the optimum channel for sensitivity to process the image. Additionally, staining time and temperature have great influence on the method, and 20 min staining time and ≥25 °C staining temperature were recommended. The minimum detection limit of labile phosphate of this method was 0.300 mg P/L, and the maximum detection limit could reach 50.00 mg P/L. The DET-CID technique can be used to measure labile phosphate in a wide range of acidic and alkaline water bodies (pH = 2-10 and water hardness from 0 to 2000 mg/L as CaCO3). The linear regression analysis shows that this technique presents very similar results compared with other two existing methods (R2 = 0.999). Our results would give insights into the precisely measurements of labile phosphate in field applications.

Translational repression of p53 by RNPC1, a p53 target overexpressed in lymphomas.

The p53 pathway is critical for tumor suppression, as the majority of human cancer has a faulty p53. Here, we identified RNPC1, a p53 target and a RNA-binding protein, as a critical regulator of p53 translation. We showed that ectopic expression of RNPC1 inhibited, whereas knockdown of RNPC1 increased, p53 translation under normal and stress conditions. We also showed that RNPC1 prevented cap-binding protein eIF4E from binding p53 mRNA via its C-terminal domain for physical interaction with eIF4E, and its N-terminal domain for binding p53 mRNA. Consistent with this, we found that RNPC1 directly binds to p53 5' and 3'untranslated regions (UTRs). Importantly, we showed that RNPC1 inhibits ectopic expression of p53 in a dose-dependent manner via p53 5' or 3' UTR. Moreover, we showed that loss of RNPC1 in mouse embryonic fibroblasts increased the level of p53 protein, leading to enhanced premature senescence in a p53-dependent manner. Finally, to explore the clinical relevance of our finding, we showed that RNPC1 was frequently overexpressed in dog lymphomas, most of which were accompanied by decreased expression of wild-type p53. Together, we identified a novel p53-RNPC1 autoregulatory loop, and our findings suggest that RNPC1 plays a role in tumorigenesis by repressing p53 translation.

Induction of NRF2-mediated gene expression by dietary phytochemical flavones apigenin and luteolin.

Apigenin (API) and luteolin (LUT) have been used as therapeutic agents in folk medicine for thousands of years. These compounds exert a variety of biological activities, including anticancer, antioxidant and antiinflammatory activities. This study investigated whether API and LUT could activate Nrf2-antioxidant response element (ARE)-mediated gene expression and induce antiinflammatory activities in human hepatoma HepG2 cells. The compounds did not exhibit any substantial toxicity at low doses (1.56-6.25 µm). The induction of ARE activity was assessed in HepG2-C8 cells after treatment with low doses of API and LUT for 6 and 12 h. It was found that the induction of ARE activity by these compounds at the higher doses was comparable to the effects of the positive control, SFN at a dose of 6.25 µm. Exposure to the PI3K inhibitor LY294002 abolished ARE activation by both API and LUT, whereas the ERK-1/2 inhibitor PD98059 only decreased ARE activity induced by API. Both compounds significantly increased the endogenous mRNA and protein levels of Nrf2 and Nrf2 target genes with important effects on heme oxygenase-1 (HO-1) expression. API and LUT significantly and dose-dependently decreased the production of nitric oxide (NO), nitric oxide synthase (iNOS) and cytosolic phospholipase A2 (cPLA2), which were induced by the treatment of HepG2 cells with 1 µg/ml of lipopolysaccharide (LPS) for 24 h. The results indicate that API and LUT significantly activate the PI3K/Nrf2/ARE system, and this activation may be responsible for their antiinflammatory effects, as demonstrated by the suppression of LPS-induced NO, iNOS and cPLA2.

The Ras GTPase-activating-like protein IQGAP1 mediates Nrf2 protein activation via the mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK)-ERK pathway.

Nrf2 plays a critical role in the regulation of cellular oxidative stress. MEK-ERK activation has been shown to be one of the major pathways resulting in the activation of Nrf2 and induction of Nrf2 downstream targets, including phase II detoxifying/antioxidant genes in response to oxidative stress and xenobiotics. In this study, IQGAP1 (IQ motif-containing GTPase-activating protein 1), a new Nrf2 interaction partner that we have published previously, was found to modulate MEK-ERK-mediated Nrf2 activation and induction of phase II detoxifying/antioxidant genes. Nrf2 binds directly to the IQ domain (amino acids 699-905) of IQGAP1. Knockdown of IQGAP1 significantly attenuated phenethyl isothiocyanate- or MEK-mediated activation of the MEK-ERK-Nrf2 pathway. Knockdown of IQGAP1 also attenuated MEK-mediated increased stability of Nrf2, which in turn was associated with a decrease in the nuclear translocation of Nrf2 and a decrease in the expression of phase II detoxifying/antioxidant genes. In the aggregate, these results suggest that IQGAP1 may play an important role in the MEK-ERK-Nrf2 signaling pathway.

A perspective on dietary phytochemicals and cancer chemoprevention: oxidative stress, nrf2, and epigenomics.

Oxidative stress is caused by an imbalance of reactive oxygen species (ROS)/reactive nitrogen species (RNS) and the antioxidative stress defense systems in cells. ROS/RNS or carcinogen metabolites can attack intracellular proteins, lipids, and nucleic acids, which can result in genetic mutations, carcinogenesis, and other diseases. Nrf2 plays a critical role in the regulation of many antioxidative stress/antioxidant and detoxification enzyme genes, such as glutathione S-transferases (GSTs), NAD(P)H:quinone oxidoreductase 1 (NQO1), UDP-glucuronyl transferases (UGTs), and heme oxygenase-1 (HO-1), directly via the antioxidant response element (ARE). Recently, many studies have shown that dietary phytochemicals possess cancer chemopreventive potential through the induction of Nrf2-mediated antioxidant/detoxification enzymes and anti-inflammatory signaling pathways to protect organisms against cellular damage caused by oxidative stress. In addition, carcinogenesis can be caused by epigenetic alterations such as DNA methylation and histone modifications in tumor-suppressor genes and oncogenes. Interestingly, recent studies have shown that several naturally occurring dietary phytochemicals can epigenetically modify the chromatin, including reactivating Nrf2 via demethylation of CpG islands and the inhibition of histone deacetylases (HDACs) and/or histone acetyltransferases (HATs). The advancement and development of dietary phytochemicals in cancer chemoprevention research requires the integration of the known, and as-yet-unknown, compounds with the Nrf2-mediated antioxidant, detoxification, and anti-inflammatory systems and their in vitro and in vivo epigenetic mechanisms; human clinical efficacy studies must also be performed.

Epigenetic reactivation of Nrf2 in murine prostate cancer TRAMP C1 cells by natural phytochemicals Z-ligustilide and Radix angelica sinensis via promoter CpG demethylation.

Cancer development has been linked to epigenetic modifications of cancer oncogenes and tumor suppressor genes; in advanced metastatic cancers, severe epigenetic modifications are present. We previously demonstrated that the progression of prostate tumors in TRAMP mice is associated with methylation silencing of the Nrf2 promoter and a reduced level of transcription of Nrf2 and Nrf2 target genes. Radix Angelicae Sinensis (RAS; Danggui) is a medicinal herb and health food supplement that has been widely used in Asia for centuries. Z-Ligustilide (Lig) is one of the bioactive components of RAS. We investigated the potential of Lig and RAS to restore Nrf2 gene expression through epigenetic modification in TRAMP C1 cells. Lig and RAS induced the mRNA and protein expression of endogenous Nrf2 and Nrf2 downstream target genes, such as HO-1, NQO1, and UGT1A1. Bisulfite genomic sequencing revealed that Lig and RAS treatment decreased the level of methylation of the first five CpGs of the Nrf2 promoter. A methylation DNA immunoprecipitation assay demonstrated that Lig and RAS significantly decreased the relative amount of methylated DNA in the Nrf2 gene promoter region. Lig and RAS also inhibited DNA methyltransferase activity in vitro. Collectively, these results suggest that Lig and RAS are able to demethylate the Nrf2 promoter CpGs, resulting in the re-expression of Nrf2 and Nrf2 target genes. Epigenetic modifications of genes, including Nrf2, may therefore contribute to the overall health benefits of RAS, including the anticancer effect of RAS and its bioactive component, Lig.

A γ-tocopherol-rich mixture of tocopherols maintains Nrf2 expression in prostate tumors of TRAMP mice via epigenetic inhibition of CpG methylation.

Nuclear factor-erythroid 2-related factor 2 (Nrf2) plays a pivotal role in maintaining cellular redox homeostasis and eliminating reactive toxic species. Nrf2 is epigenetically suppressed due to CpG hypermethylation in prostate tumors from the transgenic adenocarcinoma of the mouse prostate (TRAMP) model. We previously showed that dietary feeding of a γ-tocopherol-rich mixture of tocopherols (γ-TmT) suppressed prostate tumorigenesis in TRAMP mice associated with higher Nrf2 protein expression. We hypothesized that γ-TmT may maintain Nrf2 through epigenetic inhibition of promoter CpG methylation. In this study, 8-wk-old male TRAMP mice were fed 0.1% γ-TmT or a control diet for 16 wk. The methylation in the Nrf2 promoter was inhibited in the prostate of the γ-TmT group compared with the control group. Protein expressions of DNA methyltransferase (DNMT), including DNMT1, DNMT3A, and DNMT3B, were lower in the prostate of the γ-TmT group than in the controls. TRAMP-C1 cells were treated with 30 µmol/L of γ-TmT or blank medium for 5 d. The methylation in the Nrf2 promoter was inhibited in the γ-TmT-treated cells compared with the untreated cells at d 5, and mRNA and protein expressions of Nrf2 and NAD(P)H:quinone oxidoreductase 1 were higher. Interestingly, only DNMT3B was inhibited in the γ-TmT-treated cells compared with the untreated cells. In the aggregate, our findings demonstrate that γ-TmT could inhibit CpG methylation in the Nrf2 promoter in the prostate of TRAMP mice and in TRAMP-C1 cells, which might lead to higher Nrf2 expression and potentially contribute to the prevention of prostate tumorigenesis in this TRAMP model.

Metal(loid) flux change in Dongting Lake due to the operation of Three Gorges Dam, China.

A drastic decrease in the suspended sediment of Dongting Lake (DTL) has been observed due to Three Gorges Dam (TGD) impoundment operation since 2003. However, the relationship between sediment loads and metal fluxes has not been studied. This study comprehensively analyzed the content characteristics of seven metal(loid)s (As, Cd, Cr, Cu, Hg, Pb, and Zn) in the surface sediment of DTL from 2000 to 2019. The period of 2005-2009 corresponded to a metal(loid) enrichment stage in the sediment of DTL. The metal(loid) cumulative input of DTL from 2000 to 2019 reached 153 × 103 t, and the increasing rate was gradually diminished because of TGD operation, while the metal(loid) cumulative output reached 132 × 103 t. Undergoing an input-output state transition, the metal(loid) cumulative deposition of DTL in 2019 was only 42% of its peak in 2007. Especially, the metal(loid) fluxes of DTL all became negative for the first time in 2006. It is worth noting that Cd in DTL has shifted to a net export during the study period. Finally, the assessment results of pollution, risk, and toxicity indicated that metal(loid) effects on sediment quality were weakening in recent years. This study confirmed that DTL has shifted from metal(loid) deposition to export, providing new information for future DTL management options.

Twenty years of China's water pollution control: Experiences and challenges.

Water pollution is a major environmental problem worldwide, especially in developing countries. China's environmental protection strategies have been pushed to the highest priority in history, driving remarkable achievements in water pollution control, but were also coupled with new challenges. In this study, we analyzed diverse long-term data (i.e. water quality, WWTPs, pollutant discharge etc.) to systematically understand the process of water pollution control in China in the last twenty years. The results highlighted that the collection and treatment capacity of wastewater in China approached the developed country level, with the treatment rates exceeding 90% both in urban and country areas. The environmental quality of surface water was continuously improved, but water pollution problems remained in the river basins of eastern China, with remarkable economic progress. Rapid economic growth rather than population growth was the limiting factor for water pollution control in China. Therefore, more efforts should be made to further improve wastewater collection and treatment capacity and address the gap between effluent discharge limits for wastewater treatment plants and environmental quality standards for surface water. China's progress toward water pollution control provided important insights for other developing countries.

Phytochemicals: cancer chemoprevention and suppression of tumor onset and metastasis.

Carcinogenesis is a multi-step process which could be prevented by phytochemicals. Phytochemicals from dietary plants and other plant sources such as herbs are becoming increasingly important sources of anticancer drugs or compounds for cancer chemoprevention or adjuvant chemotherapy. Phytochemicals can prevent cancer initiation, promotion, and progression by exerting anti-inflammatory and anti-oxidative stress effects which are mediated by integrated Nrf2, NF-kappaB, and AP-1 signaling pathways. In addition, phytochemicals from herbal medicinal plants and/or some dietary plants developed in recent years have been shown to induce apoptosis in cancer cells and inhibition of tumor growth in vivo. In advanced tumors, a series of changes involving critical signaling molecules that would drive tumor cells undergoing epithelial-mesenchymal transition and becoming invasive. In this review, we will discuss the potential molecular targets and signaling pathways that mediate tumor onset and metastasis. In addition, we will shed light on some of the phytochemicals that are capable of targeting these signaling pathways which would make them potentially applicable to cancer chemoprevention, treatment and control of cancer progression.

Assessment of human health risk due to lead in urban park soils using in vitro methods.

Beijing parks always have a large flow of local residents and tourists, and the soil Pb could threaten human health by incidental ingestion. Soil samples from eleven parks in Beijing were collected to assess the human health risk associated with Pb. Lead bioaccessibility in these parks ranged from 3.2 ± 0.4% to 12.1 ± 0.5% in the physiologically based extraction test (PBET) gastric phase and increased when approaching the city center. The chemical forms and soil properties (Fe, organic matter, and grain size) were important factors affecting the soil Pb bioaccessibility. The geo-accumulation index of Beihai Park (BH, near the city center) reached 1.3 ± 0.1 indicating moderate contamination. Lead health risk to children in BH should be of concern though its hazard quotient was below one. Results obtained from the Diffusive Gradients in Thin-films (DGT)-induced fluxes in the soils (DIFS) model showed that Pb-release in some parks farther from the city center was a "partially sustained case" (Rdiff < R < 0.95) indicating that soil particles could partially replenish effective Pb to the soil solution. A relatively higher desorption rate constant (k1) and shorter characteristic response time (Tc) were also found in these parks, indicating non-negligible release risk. Soil Pb based on the PBET method and DIFS model could provide a reliable reference to park managers for the health risk management of Pb pollution.

Assessment methodology applied to arsenic pollution in lake sediments combining static and dynamic processes.

The fraction transformation from stable to mobile forms in sediments is continuous, slow, and spontaneous chain reactions causing static risks to the aquatic system. However, this process may change into abrupt, rapid, and dynamic paths when certain physicochemical conditions changed. Using the Delayed Geochemical Hazard (DGH) model, comprehensive methods combing both static and dynamic risk assessment were therefore conducted to evaluate the aforementioned processes. By applying these methods, arsenic (As) pollution in surface sediments of the Baiyangdian Lake (BYD Lake) was investigated thoroughly as a case study area. The results showed that the total As concentrations in those sediment samples ranged from 4.87 to 17.94 mg/kg, with an average of 8.75 mg/kg. In a fraction, Fe and Mn were observed to pose effects on the surface-adsorbed (AsS) and residual fractions (AsR) with the coefficient analysis. The static risk assessment showed that both the contamination and ecological risk are at a low level in the total content but a low to moderate risk in the fraction. The dynamic risk assessment posted the potential transformation paths of As in the sediments, indicating a trend of potential DGH burst in 45.24%-78.57% of the BYD Lake. In summary, this study provides a methodology for the risk assessment of arsenic that may extend to other heavy metal(loid)s combining static and dynamic processes in sediments.

Histone Methyltransferase Setd7 Regulates Nrf2 Signaling Pathway by Phenethyl Isothiocyanate and Ursolic Acid in Human Prostate Cancer Cells.

SCOPE: This study aims to investigate the role of the epigenetic regulator SET domain-containing lysine methyltransferase 7 (Setd7) in regulating the antioxidant Nrf2 pathway in prostate cancer (PCa) cells and examines the effects of two phytochemicals, phenethyl isothiocyanate (PEITC) and ursolic acid (UA). METHODS AND RESULTS: Lentivirus-mediated shRNA knockdown of Setd7 in LNCaP and PC-3 cells decreases the expression of downstream Nrf2 targets, such as NAD(P)H: quinone oxidoreductase 1 (Nqo1) and glutathione S-transferase theta 2 (Gstt2). Downregulation of Setd7 decreases soft agar colony formation ability of PCa cells. Knockdown of Setd7 increases reactive oxygen species (ROS) generation. Furthermore, Setd7 knockdown attenuates Nqo1 and Gstt2 expression in response to H2 O2 challenge, whereas increased DNA damage is observed in Setd7 knockdown cells in comet assay. Interestingly, Setd7 expression could be induced by the dietary phytochemicals PEITC and UA. Chromatin immunoprecipitation (ChIP) assays show that Setd7 knockdown decreased H3K4me1 enrichment in the Nrf2 and Gstt2 promoter regions, while PEITC and UA treatments elevated the enrichment. CONCLUSION: Taken together, these results indicate that Setd7 knockdown decreases Nrf2 and Nrf2-target genes expression and that PEITC and UA induce Setd7 expression, which activates the Nrf2/antioxidant response element (ARE) signaling pathway and protects DNA from oxidative damage.

Epigenetic alterations in TRAMP mice: epigenome DNA methylation profiling using MeDIP-seq.

PURPOSE: We investigated the genomic DNA methylation profile of prostate cancer in transgenic adenocarcinoma of the mouse prostate (TRAMP) cancer model and to analyze the crosstalk among targeted genes and the related functional pathways. METHODS: Prostate DNA samples from 24-week-old TRAMP and C57BL/6 male mice were isolated. The DNA methylation profiles were analyzed by methylated DNA immunoprecipitation (MeDIP) followed by next-generation sequencing (MeDIP-seq). Canonical pathways, diseases and function and network analyses of the different samples were then performed using the Ingenuity® Pathway Analysis (IPA) software. Some target genes with significant difference in methylation were selected for validation using methylation specific primers (MSP) and qPCR. RESULTS: TRAMP mice undergo extensive aberrant CpG hyper- and hypo-methylation. There were 2147 genes with a significant (log2-change ≥ 2) change in CpG methylation between the two groups, as mapped by the IPA software. Among these genes, the methylation of 1105 and 1042 genes was significantly decreased and increased, respectively, in TRAMP prostate tumors. The top associated disease identified by IPA was adenocarcinoma; however, the cAMP response element-binding protein (CREB)-, histone deacetylase 2 (HDAC2)-, glutathione S-transferase pi (GSTP1)- and polyubiquitin-C (UBC)-related pathways showed significantly altered methylation profiles based on the canonical pathway and network analyses. MSP and qPCR results of genes of interests corroborated with MeDIP-seq findings. CONCLUSIONS: This is the first MeDIP-seq with IPA analysis of the TRAMP model to provide novel insight into the genome-wide methylation profile of prostate cancer. Studies on epigenetics, such as DNA methylation, will potentially provide novel avenues and strategies for further development of biomarkers targeted for treatment and prevention approaches for prostate cancer.

Epigenetic CpG Methylation of the Promoter and Reactivation of the Expression of GSTP1 by Astaxanthin in Human Prostate LNCaP Cells.

Astaxanthin (AST), a red dietary carotenoid, has synergistic antioxidant effects with polyunsaturated fatty acids at low concentrations via Nuclear factor (erythroid-derived 2)-like 2 (NFE2L2 or Nrf2)/antioxidant response element (ARE) signaling. In addition, chromatin remodeling and DNA methylation-based gene silencing represent a common mechanism in prostate carcinogenesis and tumor progression from normal cells to pre-initiated cells and ultimately to invasive carcinoma. Therefore, the control of epigenetic modification and the transcriptional/translational control of the activation of Nrf2 and Nrf2-target genes, including glutathione S-transferases (GSTs), appear to be an important mechanism that protects cells against injuries from oxidative stress and cancer development. In this study, we aim to investigate the role of AST in reactivating the expression of Nrf2 and GSTP1 through epigenetic modification in human prostate LNCaP cells. Treatment with AST in human LNCaP cells reduced the methylation of 21 CpG sites of the GSTP1 CpG island but did not affect the three CpG sites of the Nrf2 promoter region. AST induced the mRNA expression and protein expression of both Nrf2 and GSTP1. It also increased the mRNA expression of NQO1 in sh-mock LNCaP cells but not in sh-SETD7 LNCaP cells. Furthermore, AST reduced the protein expression of DNMT3b and significantly inhibited DNMT and HDAC activities in vitro. Taken together, these results suggest that AST decreased the methylation status of the GSTP1, and these epigenetic modifying effects may originate from the decreasing activities of epigenetic modification enzymes, contributing to the overall beneficial health effects of AST.

Identification of elements essential for transcription in Brugia malayi promoters.

Little is known concerning promoter structure in the filarial parasites. Recently, transient transfection methods have been developed for the human filarial parasite Brugia malayi. These methods have been employed to localize the promoter for the 70kDa heat shock protein (BmHSP70) to a region extending 394nt upstream from the initiating codon of the BmHSP70 open reading frame. Replacement mutagenesis was used to define the elements necessary for BmHSP70 promoter activity in detail. Four domains, ranging in size from six to 22 nucleotides, were found to be necessary for full promoter activity. The two most distal domains encoded a binding site for the heat shock transcription factor and a putative binding site for the GAGA transcription factor, motifs that are found in many other HSP70 promoters. However, none of the essential domains contained sequences typical of cis elements that are usually found in the core domain of a eukaryotic promoter. The largest essential domain was located at positions -53 to -32, and included the splice leader addition site. These data suggest that the regulatory domains of the BmHSP70 promoter were similar to those found in other eukaryotes, but that the core promoter domain exhibited features that appeared to be distinct from those found in most other well-characterized eukaryotic promoters. An analysis of two additional promoters of B.malayi highly transcribed genes suggests that they also lack features commonly found in most eukaryotic core promoters, suggesting that the unique features of the BmHSP70 core promoter are not confined to this gene.

Phenethyl isothiocyanate (PEITC) suppresses prostate cancer cell invasion epigenetically through regulating microRNA-194.

SCOPE: Tumor metastasis greatly contributes to the mortality of prostate cancer. The glucosinolate-derived phenethyl isothiocyanate (PEITC) has been widely documented to reduce the risk of prostate cancer by modulating multiple biologically relevant processes. Emerging evidence suggests that PEITC may exert its anti-cancer effects through epigenetic mechanisms including microRNAs. Altered levels of miRNA have been linked to tumor malignancy due to their capacity to regulate functional gene expression in carcinogenesis. Here, we assessed the effects of PEITC on miRNA expression which is related to PCa cell invasiveness. METHODS AND RESULTS: Utilizing oligonucleotide microarray first identified the most affected miRNAs in LNCaP cells after PEITC treatment. Several top altered miRNAs were further validated using quantitative PCR. Interestingly, overexpression of miR-194 suppressed PC3 cell invasion in matrigel-coated Transwell chambers. Bone morphogenetic protein 1 (BMP1) was shown to be a direct target of miR-194. Downregulation of BMP1 by miR-194 or PEITC led to decreased expression of key oncogenic matrix metalloproteinases, MMP2 and MMP9. This in turn resulted in the suppression of tumor invasion. CONCLUSION: Our results indicate that miR-194 downregulates the expression of oncogenic MMP2 and MMP9 by targeting BMP1, which suggests a potential new mechanistic target by which PEITC suppresses prostate cancer cell invasiveness.

Epigenetic blockade of neoplastic transformation by bromodomain and extra-terminal (BET) domain protein inhibitor JQ-1.

The neoplastic transformation of cells and inflammation are processes that contribute to tumor initiation. Recently, emerging evidence has suggested that epigenetic alterations are also implicated in the early stages of carcinogenesis. Therefore, potent small molecules targeting epigenetic regulators have been developed as novel cancer therapeutic and preventive strategies. Bromodomain and extraterminal domain (BET) proteins are epigenetic readers that play key roles at the interface between chromatin modification and transcriptional regulation. In this study, we investigated the effect of the BET inhibitor JQ-1 on malignant transformation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in mouse skin epidermal JB6 P+ cells. Treatment with JQ-1 effectively impaired TPA-induced colony formation in vitro. At the molecular level, the expression of several key TPA-induced pro-survival and pro-proliferative genes (Bcl2, Cyclin D1, and c-Myc) decreased rapidly after BET inhibition. In addition, JQ-1 treatment attenuated the activation of inflammatory NF-κB signaling triggered by TPA. Luciferase reporter assays using plasmids carrying different elements from the COX2 or IL6 promoters demonstrated that JQ-1 does not directly inhibit interactions between NF-κB and its binding sequence; rather, it affects CRE-element-associated transcriptional enhancement. Through siRNA gene silencing, we found that JQ-1 inhibits the p300-dependent transcriptional activation of COX2, which correlates with the results of the luciferase assay. Chromatin immunoprecipitation assays showed that TPA elevated H3K27Ac enrichment in the COX2 promoter region, which is mediated by p300, and Brd4. JQ-1 treatment did not change H3K27Ac levels but decreased the recruitment of Brd4 and RNA Polymerase II. Collectively, our study reveals that the BET inhibitor JQ-1 exerts potent anti-cancer and anti-inflammatory effects by interfering with the core transcriptional program of neoplastic transformation.

MicroRNAs: New players in cancer prevention targeting Nrf2, oxidative stress and inflammatory pathways.

miRNAs are endogenous small non-coding RNAs of 20-22 nucleotides that repress gene expression at the post-transcriptional level. There is growing interest in the role of miRNAs in cancer chemoprevention, and several naturally occurring chemopreventive agents have been found to be modulators of miRNA expression both in vitro and in vivo. Moreover, these chemopreventive phytochemicals commonly possess anti-oxidative and/or anti-inflammatory properties, and Nrf2 has been extensively studied as a molecular target in cancer prevention. The crosstalk between miRNAs and the traditional cellular signaling pathways of chemoprevention remain to be fully elucidated. This review summarizes the data regarding the potential interactions between miRNAs and anti-oxidative and anti-inflammatory pathways. Cellular redox homeostasis can affect the biogenesis and processing of miRNAs, which in turn regulate the Nrf2 pathway of detoxifying/anti-oxidative genes. We also discuss the miRNA regulatory mechanisms in relation to inflammation-related cancer signaling pathways.

Curcumin inhibits anchorage-independent growth of HT29 human colon cancer cells by targeting epigenetic restoration of the tumor suppressor gene DLEC1.

Colorectal cancer remains the most prevalent malignancy in humans. The impact of epigenetic alterations on the development of this complex disease is now being recognized. The dynamic and reversible nature of epigenetic modifications makes them a promising target in colorectal cancer chemoprevention and treatment. Curcumin (CUR), the major component in Curcuma longa, has been shown as a potent chemopreventive phytochemical that modulates various signaling pathways. Deleted in lung and esophageal cancer 1 (DLEC1) is a tumor suppressor gene with reduced transcriptional activity and promoter hypermethylation in various cancers, including colorectal cancer. In the present study, we aimed to investigate the inhibitory role of DLEC1 in anchorage-independent growth of the human colorectal adenocarcinoma HT29 cells and epigenetic regulation by CUR. Specifically, we found that CUR treatment inhibited colony formation of HT29 cells, whereas stable knockdown of DLEC1 using lentiviral short hairpin RNA vector increased cell proliferation and colony formation. Knockdown of DLEC1 in HT29 cells attenuated the ability of CUR to inhibit anchorage-independent growth. Methylation-specific polymerase chain reaction (MSP), bisulfite genomic sequencing, and methylated DNA immunoprecipitation revealed that CUR decreased CpG methylation of the DLEC1 promoter in HT29 cells after 5 days of treatment, corresponding to increased mRNA expression of DLEC1. Furthermore, CUR decreased the protein expression of DNA methyltransferases and subtypes of histone deacetylases (HDAC4, 5, 6, and 8). Taken together, our results suggest that the inhibitory effect of CUR on anchorage-independent growth of HT29 cells could, at least in part, involve the epigenetic demethylation and up-regulation of DLEC1.