Positive and negative regulation of prostaglandin E2 biosynthesis in human colorectal carcinoma cells by cancer chemopreventive agents

ZNF384 transcriptionally activated MGST1 to confer TMZ resistance of glioma cells by negatively regulating ferroptosis

BACKGROUND

Drug resistance is one of the major reasons of the poor prognosis and recurs frequently in glioma. Ferroptosis is considered to be a new therapeutic strategy for glioma.

METHODS

Microsomal glutathione S-transferase 1 (MGST1) expression in glioma samples was ensured through GAPIA database, qRT-PCR, western blotting assay and immunohistochemistry. The interaction between zinc finger protein 384 (ZNF384) and MGST1 promoter was analyzed through UCSC and JASPAR databases and further verified by ChIP and luciferase reporter assay. Cell viability and IC50 value of temozolomide (TMZ) was measured by CCK-8 assay. The production of MDA, GSH and ROS and the level of Fe2+ were determined using the corresponding kit.

RESULTS

MGST1 expression was increased in clinical glioma tissues and glioma cells. MGST1 expression was increased but ferroptosis was suppressed in TMZ-resistant cells when contrasted to parent cells. MGST1 silencing downregulated IC50 value of TMZ and cell viability but facilitated ferroptosis in TMZ-resistant cells and parent glioma cells. Moreover, our data indicated that ZNF384 interacted with MGST1 promoter and facilitated MGST1 expression. ZNF384 was also increased expression in TMZ-resistant cells, and showed a positive correlation with MGST1 expression in clinical level. ZNF384 decreasing enhanced the sensitivity of resistant cells to TMZ, while the effect of ZNF384 could be reversed by overexpression of MGST1.

CONCLUSION

MGST1 transcription is regulated by transcription factor ZNF384 in TMZ-resistant cells. ZNF384 confers the resistance of glioma cells to TMZ through inhibition of ferroptosis by positively regulating MGST1 expression. The current study may provide some new understand to the mechanism of TMZ resistance in glioma.

Oncogenic Activation of Nrf2, Though as a Master Antioxidant Transcription Factor, Liberated by Specific Knockout of the Full-Length Nrf1α that Acts as a Dominant Tumor Repressor

Liver-specific knockout of Nrf1 in the mouse leads to spontaneous development of non- alcoholic steatohepatitis with dyslipidemia, and then its deterioration results in hepatoma, but the underlying mechanism remains elusive to date. A similar pathological model is reconstructed here by using human Nrf1α-specific knockout cell lines. Our evidence has demonstrated that a marked increase of the inflammation marker COX2 definitely occurs in Nrf1α^−/− cells. Loss of Nrf1α leads to hyperactivation of Nrf2, which results from substantial decreases in Keap1, PTEN and most of 26S proteasomal subunits in Nrf1α^−/− cells. Further investigation of xenograft model mice showed that malignant growth of Nrf1α^−/−-derived tumors is almost abolished by silencing of Nrf2, while Nrf1α^+/+-tumor is markedly repressed by an inactive mutant (i.e., Nrf2^−/−ΔTA), but largely unaffected by a priori constitutive activator (i.e., caNrf2^ΔN). Mechanistic studies, combined with transcriptomic sequencing, unraveled a panoramic view of opposing and unifying inter-regulatory cross-talks between Nrf1α and Nrf2 at different layers of the endogenous regulatory networks from multiple signaling towards differential expression profiling of target genes. Collectively, Nrf1α manifests a dominant tumor-suppressive effect by confining Nrf2 oncogenicity. Though as a tumor promoter, Nrf2 can also, in turn, directly activate the transcriptional expression of Nrf1 to form a negative feedback loop. In view of such mutual inter-regulation by between Nrf1α and Nrf2, it should thus be taken severe cautions to interpret the experimental results from loss of Nrf1α, Nrf2 or both.

Association of aspirin and NSAID use with risk of colorectal cancer according to genetic variants

IMPORTANCE

Use of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with lower risk of colorectal cancer.

OBJECTIVE

To identify common genetic markers that may confer differential benefit from aspirin or NSAID chemoprevention, we tested gene × environment interactions between regular use of aspirin and/or NSAIDs and single-nucleotide polymorphisms (SNPs) in relation to risk of colorectal cancer.

DESIGN, SETTING, AND PARTICIPANTS

Case-control study using data from 5 case-control and 5 cohort studies initiated between 1976 and 2003 across the United States, Canada, Australia, and Germany and including colorectal cancer cases (n=8634) and matched controls (n=8553) ascertained between 1976 and 2011. Participants were all of European descent.

EXPOSURES

Genome-wide SNP data and information on regular use of aspirin and/or NSAIDs and other risk factors.

MAIN OUTCOMES AND MEASURES

Colorectal cancer.

RESULTS

Regular use of aspirin and/or NSAIDs was associated with lower risk of colorectal cancer (prevalence, 28% vs 38%; odds ratio [OR], 0.69 [95% CI, 0.64-0.74]; P = 6.2 × 10(-28)) compared with nonregular use. In the conventional logistic regression analysis, the SNP rs2965667 at chromosome 12p12.3 near the MGST1 gene showed a genome-wide significant interaction with aspirin and/or NSAID use (P = 4.6 × 10(-9) for interaction). Aspirin and/or NSAID use was associated with a lower risk of colorectal cancer among individuals with rs2965667-TT genotype (prevalence, 28% vs 38%; OR, 0.66 [95% CI, 0.61-0.70]; P = 7.7 × 10(-33)) but with a higher risk among those with rare (4%) TA or AA genotypes (prevalence, 35% vs 29%; OR, 1.89 [95% CI, 1.27-2.81]; P = .002). In case-only interaction analysis, the SNP rs16973225 at chromosome 15q25.2 near the IL16 gene showed a genome-wide significant interaction with use of aspirin and/or NSAIDs (P = 8.2 × 10(-9) for interaction). Regular use was associated with a lower risk of colorectal cancer among individuals with rs16973225-AA genotype (prevalence, 28% vs 38%; OR, 0.66 [95% CI, 0.62-0.71]; P = 1.9 × 10(-30)) but was not associated with risk of colorectal cancer among those with less common (9%) AC or CC genotypes (prevalence, 36% vs 39%; OR, 0.97 [95% CI, 0.78-1.20]; P = .76).

CONCLUSIONS AND RELEVANCE

In this genome-wide investigation of gene × environment interactions, use of aspirin and/or NSAIDs was associated with lower risk of colorectal cancer, and this association differed according to genetic variation at 2 SNPs at chromosomes 12 and 15. Validation of these findings in additional populations may facilitate targeted colorectal cancer prevention strategies.

Methionine adenosyltransferase II-dependent histone H3K9 methylation at the COX-2 gene locus

BACKGROUND

MATII biosynthesizes AdoMet, which supplies methyl group for methylation of molecules, including histone.

RESULTS

MATII interacts with histone methyltransferase SETDB1 and inhibits COX-2 gene expression.

CONCLUSION

AdoMet synthesis and histone methylation are coupled on chromatin by a physical interaction of MATII and SETDB1 at the MafK target genes.

SIGNIFICANCE

MATII may be important for both gene-specific and epigenome-wide regulation of histone methylation. Methionine adenosyltransferase (MAT) synthesizes S-adenosylmethionine (AdoMet), which is utilized as a methyl donor in transmethylation reactions involving histones. MATIIα, a MAT isozyme, serves as a transcriptional corepressor in the oxidative stress response and forms the AdoMet-integrating transcription regulation module, affecting histone methyltransferase activities. However, the identities of genes regulated by MATIIα or its associated methyltransferases are unclear. We show that MATIIα represses the expression of cyclooxygenase 2 (COX-2), encoded by Ptgs2, by specifically interacting with histone H3K9 methyltransferase SETDB1, thereby promoting the trimethylation of H3K9 at the COX-2 locus. We discuss both gene-specific and epigenome-wide functions of MATIIα.

Impact of cigarette smoke exposure on the expression of cardiac hypertrophic genes, cytochrome P450 enzymes, and oxidative stress markers in rats

Various experimental and clinical studies strongly support a cigarette smoke-heart disease association and suggest possible mechanisms, unfortunately, the involvement of genetic modulations remain unexplored. Thus, the main aim of the current study was to evaluate the effects of sub-chronic cigarette smoke exposure on the mRNA expression of cardiac hypertrophy genes, cytochrome P450 (CYP) enzymes, and the oxidative stress markers in heart rats. For this purpose, Wistar albino rats were exposed to increasing doses of passive cigarette smoke 2, 4, 8, and 24 cigarettes per day for 7 consecutive days. The mRNA expression of fifteen cardiac genes was determined using real-time polymerase chain reaction. Our results showed that the levels of hypertrophic genes; atrial natriuretic peptide, brain natriuretic peptide, and β-myosin heavy chain were significantly induced, whereas the anti-hypertrophic gene α-myosin heavy chain was dramatically inhibited, in heart tissues of passive-smoke-exposed groups compared with normal-control groups. This was accompanied with a significant induction of CYP enzymes; CYP1A1, CYP2C11, CYP2E1, and CYP3A2, and the expression of oxidative stress genes, heme oxygenase 1, catalase, cyclooxygenase, and glutathione S-Transferase. The ability of cigarette smoke to induce cardiac hypertrophic genes, CYPs enzymes, and oxidative stress, collectively explore the molecular mechanism of cigarette smoke-induced cardiac diseases and brings further investigative attention to the public health issue of the injurious effects of chronic passive smoke exposure. In conclusion, sub-chronic environmental tobacco smoke exposure increases the incidence of cardiovascular diseases through modulation of cardiac genes.

Butyrate suppresses mRNA increase of osteopontin and cyclooxygenase-2 in human colon tumor tissue

The short chain fatty acid (SCFA) butyrate, a product of fermentation of dietary fiber in the human colon, is found to exert multiple regulatory processes in colon carcinogenesis. The aim of this study was to find out whether butyrate affects the tumor-promoting genes osteopontin (OPN) and cyclooxygenase (COX)-2, their respective proteins and/or their functional activity in matched normal, adenoma and tumor colon tissues obtained from 20 individuals at colon cancer surgery. Quantitative real-time polymerase chain reaction experiments showed increased levels of OPN and COX-2 messenger RNA in tumor tissues when compared with the adjacent normal samples (P < 0.001). The addition of butyrate reduced OPN and COX-2 mRNA expression in all tissue types compared with the related medium controls (tumor: P < 0.05). In tumor samples, a downregulation of up to median 35% (COX-2) and 50% (OPN) was observed, respectively. Thereby, tumors with lower levels of OPN basal expression were more sensitive to inhibition and vice versa for COX-2 in normal tissue. At the protein and enzyme level, which were determined by using western blot and enzyme immunometric assays, the impact of the SCFA was not clearly visible anymore. The active proteins of OPN and COX-2 (determined by prostaglandin E(2)) were found to correlate with their respective mRNA expression only in 50-63% of analyzed donors. For the first time, our data reveal new insights into the chemoprotective potential of butyrate by showing the suppression of OPN and COX-2 mRNA in primary human colon tissue with the strongest effects observed in tumors.

Expression of UDP-glucuronosyltransferase 1A6 isoform in Caco-2 cells stimulated with lipopolysaccharide

Glucuronidation is an important metabolic process of detoxification in all vertebrates. The reaction is catalyzed by a multigene family of UDP-glucuronosyltransferases (UGTs) able to convert many xenobiotics and endobiotics (hydrophobic substances) to inactive, water-soluble glucuronides. The UGTs play a protective role, facilitating the elimination of potentially toxic metabolites via urine, bile and feces; therefore, impairment of UGTs may have important toxicological consequences. The regulation of UGTs during bacterial infection or inflammation is not well described. In this study, we investigated the in vitro effect of lipopolysaccharide (LPS) on the expression of the UGT1A6 isoform in human colon carcinoma Caco-2 cells. Results demonstrated a significant down-regulation of UGT1A6 expression, both in terms of mRNA and protein levels, and a reduced UGT activity after LPS exposure of cell cultures, suggesting a role for endotoxins on UGT regulation mechanisms.

Nrf3-deficient mice are not protected against acute lung and adipose tissue damages induced by butylated hydroxytoluene

We found that both wild type and Nrf3 (NF-E2-related factor 3) deficient mice are sensitive to BHT single administration exhibiting respiratory distress and considerably lose body weight following treatment. At time of sacrifice, the BHT-treated Nrf3-/- mice had lost significantly more body weight than their WT counterparts. In the lung, transcript levels of the transcription factors Nrf1, Nrf2 and Nrf3 were differentially regulated by BHT treatment. In addition, genes implicated in adipogenesis were repressed following BHT exposure in the white adipose tissue. Together, our data provide the first evidence that BHT exposure not only affects lung function but also leads to impaired adipogenesis in adipocytes.

Part of the Series: From dietary antioxidants to regulators in cellular signaling and gene regulation

The association of decreased cancer risk with intake of cruciferous vegetables and selenium is stronger than that reported for fruits and vegetables in general. An active constituent in cruciferae is sulforaphane. Chemopreventive effects of both, sulforaphane and selenium have been attributed to an antioxidant action which certainly is too simplicistic. Sulforaphane induces via activation of the Nrf2/Keap1 system phase 2 enzymes that protect against carcinogens and oxidants. Induced enzymes comprise the selenoproteins thioredoxin reductase-1 (TrxR1) and gastrointestinal glutathione peroxidase (GI-GPx, GPx2), which contain antioxidant response elements (ARE) in their promoter regions. Translational realisation of the enhanced transcripts depends on adequate selenium supply, which explains the synergism of Nrf2 activators and selenium. Regarding tumorigenesis the role of TrxR1 is ambiguous: it is essential for fast tumor cell growth but also diminishes vascularisation of tumors. The anticarcinogenic role of GI-GPx is evident from enhanced gastrointestinal tumor formation in gpx2/gpx1 double KO mice.

Gene expression profiling in Caco-2 human colon cells exposed to TCDD, benzo[a]pyrene, and natural Ah receptor agonists from cruciferous vegetables and citrus fruits

Cruciferous vegetables and citrus fruits are reported to possess health-beneficial properties, but also have been shown to contain natural aryl hydrocarbon receptor (AhR) agonists (NAhRAs). Binding to the AhR is widely assumed to activate the main pathway by which dioxins, like 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exert their toxicity. To establish whether or not activation of the AhR pathway by NAhRAs and dioxin-like substances results in similar cellular responses, gene expression profiles induced in Caco-2 cells were studied using microarray analysis. Cells were exposed to indolo[3,2-b]carbazole (ICZ), an acid reaction product from cruciferous vegetables, and to extracts of citrus pulp and grapefruit juice. Gene expression profiles induced by these NAhRAs were compared to those of the xenobiotic AhR agonists TCDD and benzo[a]pyrene (B[a]P). Over 20 genes were found more than 1.5 times up- or down-regulated by TCDD, and the expression of most of these genes was modulated in the same direction and to a similar extent by B[a]P and the NAhRAs. Results were confirmed by RT-PCR, and many of these genes may be involved in dioxin-related toxic effects. In conclusion, this in vitro study showed similar effects induced by NAhRAs, TCDD and B[a]P at the transcriptome level in a human intestinal cell line.

Neuroendocrine disruption and health effects in Elliptio complanata mussels exposed to aeration lagoons for wastewater treatment

The purpose of this study was to examine neuroendocrine-disrupting effects of two domestic wastewater aeration lagoons on freshwater mussels. Mussels were caged and placed in two final aeration lagoons for treating domestic wastewaters for 60 days, at a site 1km downstream of the dispersion plume on the eastern shores of the Richelieu River; the western shore served as the reference site. The mussels were analysed for gonad activity, oxidative metabolism of xenobiotics, stress biomarkers and neuroendocrine status (monoamine and arachidonic acid metabolism). The domestic wastewaters produced many different effects at all levels examined. The gonado-somatic index and vitellogenin-like proteins were significantly induced in both aeration lagoons and gonad pyrimidine synthesis (aspartate transcarbamylase activity) was significantly reduced, indicating that vitellogenin-like proteins were produced while DNA synthesis in gametes remained constant. Biomarkers of oxidative metabolism revealed that global heme oxidase (HO), glutathione S-transferase and xanthine (caffeine) oxydoreductase (XOR) activities were significantly induced in at least one of the aeration lagoons, but not downstream of the dispersion plume. The activities of 7-ethoxyresorufin (cytochrome P4501A1), dibenzoylfluorescein (cytochrome P450 3A4 and 3A5) and benzoyloxyresorurufin (cytochrome P450 3A4 and 2B6) dealkylases were readily induced by substances sharing structural similarities with coplanar polyaromatic hydrocarbons and hydroxylated or aminated aromatic or cyclic hydrocarbon compounds such as pharmaceuticals or steroids in the domestic wastewaters. Biomarkers of toxic stress revealed that exposure to aeration lagoons led to increased production of metallothioneins, lipid peroxidation and DNA strand breaks, with decreased heme oxygenase activity. LPO was significantly correlated with XOR, HO and cytochrome P4501A1 activities. Neuroendocrine effects included significant increases in dopamine and serotonin levels and in monoamine oxidase (MAO). Dopamine transport in synaptosome was significantly increased while serotonin transport activity was significantly decreased, suggesting the mussels were in a state of serotonergicity. Moreover, arachidonic acid cyclooxygenase (COX) activity was also readily increased in one aeration lagoon. Aeration lagoons for the treatment of domestic wastewaters are toxic, estrogenic and disrupt the metabolism of monoamines and COX in freshwater mussels.

Advance of the relationship between esophageal cancer and cyclooxygenase-2

Cyclooxygenase (COX) is a rate-limiting enzyme in the arachidonate metabolism. COX-2, as one of the isoenzymes of COX, is responsible for the pathogenesis, development, metastasis and prognosis of carcinoma through various mechanisms. Esophageal cancer is one of the common cancers with high incidence and high mortality. It is reported that COX-2 plays important roles in it, through xenobiotic metabolism, inhibiting apoptosis, development of inflammation-stimulated hyperplasia and metaplasia, suppressing host immune responses, inducing angiogenesis and promoting infiltration and metastasis. Recently, some trials demonstrated that selective COX-2 inhibitors can inhibit COX-2 to prevent carcinogenesis. In this article, we reviewed the roles of COX-2 in the carcinogenesis and analyzed COX-2 inhibitors for the chemoprevention of esophageal cancer.

The anti-inflammatory actions of LCY-2-CHO, a carbazole analogue, in vascular smooth muscle cells

LCY-2-CHO has anti-inflammatory actions on macrophages. To understand its therapeutic implication in atherosclerosis, we examined its effects on the expressions of anti-inflammatory and inflammatory proteins in cultured rat aortic vascular smooth muscle cells (VSMC). LCY-2-CHO is able to induce heme oxygenase-1 (HO-1) protein expression through a transcriptional action. The HO-1 inducting effect of LCY-2-CHO was inhibited by SB203580, N(G)-nitro-l-arginine methylester (l-NAME), and wortmannin, but was not affected by U0126 or SP600125. In accordance LCY-2-CHO increased protein phosphorylation of p38, Akt, and eNOS. Nrf2 is a transcription factor essential for HO-1 gene induction and we showed that LCY-2-CHO is able to cause Nrf2 nuclear translocation and this action depends on p38, Akt and eNOS. In addition to induce anti-inflammatory HO-1, LCY-2-CHO reduced interleukin-1beta (IL-1beta)-induced inflammatory mediators, inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), growth-related oncogene protein-alpha (GRO-alpha), and interleukin-8 (IL-8). Inhibitory effect on IL-1beta-mediated NF-kappaB activation was evidenced by the diminishment of IkappaB kinase (IKK) phosphorylation and IkappaBalpha degradation. In contrast, IL-1beta-mediated ERK and JNK activations were not changed by LCY-2-CHO, while p38 activation by IL-1beta and LCY-2-CHO displayed the non-additivity. Taken together, given the overall anti-inflammatory properties of LCY-2-CHO in VSMC, in terms to induce HO-1 gene expression and inhibit inflammatory gene expression, these results highlight the therapeutic potential of LCY-2-CHO in atherosclerosis.

The role of aryl hydrocarbon receptor in the pathogenesis of cardiovascular diseases

Numerous experimental and epidemiological studies have demonstrated that polycyclic aromatic hydrocarbons (PAHs), which are major constituents of cigarette tobacco tar, are strongly involved in the pathogenesis of the cardiovascular diseases (CVDs). Knowing that PAH-induced toxicities are mediated by the activation of a cytosolic receptor, aryl hydrocarbon receptor (AhR), which regulates the expression of a group of xenobiotic metabolizing enzymes (XMEs) such as CYP1A1, CYP1A2, CYP1B1, NQO1, and GSTA1, suggests a direct link between AhR-regulated XMEs and CVDs. Therefore, identifying the localization and expression of the AhR and its regulated XMEs in the cardiovascular system (CVS) is of major importance in understanding their physiological and pathological roles. Generally, it was believed that the levels of AhR-regulated XMEs are lower in the CVS than in the liver; however, it has been shown that similar or even higher levels of expression are demonstrated in the CVS in a tissue- and species-specific manner. Moreover, most, if not all, AhR-regulated XMEs are differentially expressed in most of the CVS, particularly in the endothelium cells, aorta, coronary arteries, and ventricles. Although the exact mechanisms of PAH-mediated cardiotoxicity are not fully understood, several mechanisms are proposed. Generally, induction of CYP1A1, CYP1A2, and CYP1B1 is considered cardiotoxic through generating reactive oxygen species (ROS), DNA adducts, and endogenous arachidonic acid metabolites. However the cardioprotective properties of NQO1 and GSTA1 are mainly attributed to the antioxidant effect by decreasing ROS and increasing the levels of endogenous antioxidants. This review provides a clear understanding of the role of AhR and its regulated XMEs in the pathogenesis of CVDs, in which imbalance in the expression of cardioprotective and cardiotoxic XMEs is the main determinant of PAH-mediated cardiotoxicity.

Primary tumour genetic alterations and intra-tumoral heterogeneity are maintained in xenografts of human colon cancers showing chromosome instability

Evaluation of the role of clonal heterogeneity in colon tumour sensitivity/resistance to drugs and/or in conferring metastatic potential requires an adequate experimental model in which the tumour cells maintain the initial genetic alterations and intra-tumoral heterogeneity through maintenance of the genetic clones present in the initial tumour. Therefore, we xenografted subcutaneously into nude mice seven human colonic tumours (from stages B1 to D) that showed chromosome instability and transplanted them sequentially for up to 14 passages. Maintenance after xenografting of the genetic alterations present in the initial tumours was scored by allelotype studies targeting 45 loci localized on 18 chromosomes. We show that xenografting does not alter the genetic or the histological profiles of the tumours even after 14 passages. Screening of the entire genome of one tumour by comparative genome hybridization also showed overall stability of the alterations between the initial and the xenografted tumour. In addition, intra-tumoral heterogeneity was maintained over time, suggesting that no clonal selection occurred in the nude mice. The observation that some loci showed partial allelic imbalance in the initial tumour but loss of heterozygosity after the first passage in nude mice when all the normal cells were lost may allow identification of interesting genetic defects that could be involved in tumour expansion. Thus, sequential xenografts of colon tumours will provide a powerful model for further study of tumour clonality and for the identification of genetic profiles responsible for differential resistance to therapeutic treatments. Our data also suggest that tumour expansion can result from alterations in several distinct genetic pathways.

Benzo-[a]-pyrene increases invasion in MDA-MB-231 breast cancer cells via increased COX-II expression and prostaglandin E2 (PGE2) output

Benzo-[a]-pyrene (B[a]P), a carcinogenic component of cigarette smoke, has been shown to increase both COX-II expression and prostaglandin output in vascular smooth muscle and oral epithelial cells. In addition, invasive breast cancer cells have been reported to over express COX-II and PGE(2). Therefore, the objective of this study was to quantify the effect of increasing B[a]P concentrations on COX-II expression, PGE(2) output, and invasion using MDA-MB-231 cells, an invasive estrogen unresponsive breast cancer cell line. B[a]P significantly increased invasion in MDA-MB-231 cells at concentrations greater than 4 x 10(-8) M. Treatment of MDA-MB-231 cells with Vomitoxin (a selective COX-II inducer) enhanced invasion whereas co-treatment with NS398 (a selective COX-II inhibitor) attenuated B[a]P-induced invasion in MDA-MB-231 cells. Immunohistochemical staining and Western blots demonstrated a significant B[a]P treatment-induced increase in both the number of COX-II immunopositive MDA-MB-231 cells and COX-II protein levels. Moreover, B[a]P-treatment induced a profound (46 fold) increase in PGE(2) production by MDA-MB-231 cells. The aryl hydrocarbon receptor (AhR) antagonists resveratrol (RES) and alpha-naphthaflavone (alpha-NF) had no effect on their own, whereas B[a]P-induced invasion was significantly inhibited by co-treatment with RES and alpha-NF. Our data demonstrate that B[a]P-induced changes in invasion are mediated through augmented COX-II expression and PGE(2) production involving an AhR regulated pathway. Moreover, these results suggest a potential role for the AhR signalling pathway in breast cancer invasion.

The expression of cyclooxygenase-2, VEGF and PGs in CIN and cervical carcinoma

OBJECTIVE

To study the expression of cyclooxygenase-2 (COX-2), vascular endothelial growth factor (VEGF) and prostaglandins (PGs) in cervical tissues of differential pathological types, especially in cervical intraepithelial neoplasia (CIN) and cervical carcinoma, and their possible relationships in carcinogenesis.

METHODS

Tissue blocks and blood samples from 20 normal cervix women, 20 cervix inflammation patients, 20 CIN patients and 40 patients with cervical carcinoma, respectively, at our institutions from February 2000 to March 2002 were available for this study. COX-2 mRNA was examined by reverse transcription-polymerase chain reaction (RT-PCR). COX-2 and VEGF proteins were measured by immunohistochemistry using monoclonal antibodies to them. PGs (PGE2, TXB2, 6-k-PGF(1alpha)) were detected by radioimmunoassay (RIA).

RESULT

The overall positive expression of COX-2 and the quantity of PGs, especially PGE2 in inflammation, CIN and cervical carcinoma was higher and much higher than that in normal cervix (P < 0.001), There was a close relationship between COX-2 and PGs. The positive expression rate of VEGF in cervical carcinoma was higher than that in normal, inflammatory and CIN cervix, respectively (P < 0.001). VEGF protein was occasionally expressed in CIN cervix (15%). There was no association among COX-2, VEGF and clinicopathological parameters in cervical carcinoma. The expression of COX-2 and VEGF in cases with tumor in diameter more than 4 cm (90.9%, 72.7%) was higher than those with smaller tumor (86.2%, 51.7%).

CONCLUSIONS

The COX-2 probably is a gene involved early in carcinogenesis of cervical carcinoma by increase of PGs, and accelerates the progress of tumor by increase of PGs and VEGF. Therefore testing the expression of PGs may be a prognosis marker for clinical diagnosis.

Expression of PGE2, Bcl-2 and Bax in carcinogenesis of colorectal mucosa

AIM: To investigate the expression of PGE₂, Bcl-2 and Bax in the carcinogenesis of colorectal mucosa and the relationship between them.

METHODS: The expression of PGE₂, Bcl-2 and Bax were detected in 15 normal colorectal mucous membrane (NCM), 20 chronic colonitis (CHC), 30 colorectal adenoma (CAA), 50 colorectal cancer (CC)and 50 cancer adjacent (CAT) tissues by DAB immunohistochemical staining. The correlations among PGE₂, Bcl-2 and Bax expression as well as the clinical and pathological characteristics were analyzed.

RESULTS: The rates of PGE₂ expression in NCM, CHC, CAT, CAA and CC tissues were 6.67%, 10%, 40%, 56.7% and 90% respectively and manifested an ascending trend. The rates of Bcl-2 expression in the five groups were 6.67%, 10%, 38%, 46.7%, and 76% respectively and also showed an ascending trend. The rates of Bax expression in the five groups was 86.67%, 75%, 78%, 76.7% and 82% respectively and there was no significant difference among the five groups (P>0.05). However, the positive degree in NCM, CA and CC group exhibited a descending trend (P<0.05). The expressions of PGE₂, Bcl-2 and Bax in human CC were not associated with sex, age and the size of tumor (P>0.05). A positive correlation was noted between expression of PGE₂ and Bcl-2 in CC tissue (r = 0.532, P<0.05). The same correlation also existed between Bax and Bcl-2 (r = 0.653, P<0.05). The rates of PGE₂, Bcl-2 and Bax expression in highly and moderately differentiated CC were significantly higher than those in lowly differentiated one (100%, 88.9%, 85.2% vs 79.3%, 60.9%, 78.3%; P<0.05). The expression of Bcl-2 was significantly higher in Duke's A, B stage than that in Duke's C, D (90%, 77.8% vs 60%, 57.2%; P<0.05).

CONCLUSION: The expression of PGE₂ and Bcl-2 increases while that of Bax decreases with the occurrence and development of CC, which indicates that PGE₂ and Bcl-2 play important roles in the carcinogenesis and development of CC. At the same time, there is a positive relationship between PGE₂ and Bcl-2.

Dietary chemopreventive compounds and ARE/EpRE signaling

Chemoprevention comprises multiple intervention methods using either pharmacological or dietary agents to impede, arrest, or reverse carcinogenesis at various stages. Development of dietary compounds as potential cancer chemopreventive agents is highly desirable, due to their safety, low toxicity, and general acceptance as dietary supplements. In this review, potential application of the dietary detoxifying enzyme inducers for chemoprevention and their relevant signaling events are discussed. Overall, the detoxifying enzyme system plays an important role in determining the final fate of carcinogens/procarcinogens and their subsequent impact on carcinogenesis. Among those positive regulators, phenolic and sulfur-containing compounds are two major classes of dietary detoxifying enzyme inducers. Regulation of many detoxifying enzymes by dietary chemopreventive compounds is mediated by the antioxidant response element (ARE)/electrophile response element (EpRE), which is located in the promoter region of related genes. Transcription factor nuclear factor E2-related factor 2 (Nrf2) binds to the ARE sequence to initiate gene expression. In response to treatments of various detoxifying enzyme inducers, several signal transduction pathways, including the oxidative stress, mitogen-active protein kinase, protein kinase C, and phosphatidylinositol 3-kinase pathways, are activated. The consequences of the activation of these signaling cascades, whether directly or indirectly, lead to the dissociation of Nrf2 from its cytosolic sequester Kelch-like ECH associating protein 1, nuclear translocation, and accumulation of Nrf2 protein in the nucleus, and ultimately increase the expression level of detoxifying enzymes through transcriptional activation of ARE/EpRE in those responsible genes.