The activity of transient receptor potential channel C-6 modulates the differentiation of fat cells.

Previously, the V1-3 isoforms of the transient receptor potential channel (TRP) have been shown to promote or prevent adipocyte differentiation. In the current study, the C isoforms were screened for blocking adipogenesis. The hypothesis that the TRP classic or canonical (TRPC) deters adipocyte differentiation was investigated in 3T3-L1 cells employing the channel-specific activator and antagonist, silencing, and overexpression techniques. Fat accumulation in cells was visualized by Oil Red O staining. Intracellular calcium inflow was estimated by confocal microscopy. A high-fat (HF) feeding study was also performed on C57BL/6J mice to verify the findings in the cell model. Among the 6 C isoforms tested, only TRPC-6 inhibited the differentiation of fat cells. The phytochemical quercetin induced the channel protein expression. Calcium-imaging results also revealed that the flavonoid could trigger calcium inflow. Coadministration of quercetin (1 or 20 mg/kg body weight) in an HF diet prevented TRPC-6 from declining and attenuated phosphorylated (p)-PKB and PI3k, as well as the proliferation of visceral fat cells. The present study illustrated that TRPC-6 activation could perturb adipocyte differentiation. The food flavonoid quercetin was a TRPC-6 inducer and activator and it could prevent adipogenesis in mice.-Tan, Y. Q., Kwan, H. Y., Yao, X., Leung, L. K. The activity of transient receptor potential channel C-6 modulates the differentiation of fat cells.

Dietary flavones counteract phorbol 12-myristate 13-acetate-induced SREBP-2 processing in hepatic cells.

Consumption of fruits and vegetables is generally regarded as beneficial to plasma lipid profile. The mechanism by which the plant foods induce desirable lipid changes remains unclear. SREBP-2 is crucial in cholesterol metabolism, and it is a major regulator of the cholesterol biosynthesis enzyme HMGCR. Our lab has previously illustrated that apigenin and luteolin could attenuate the nuclear translocation of SREBP-2 through an AMPK-dependent pathway. In the present study, these two flavones were studied for their ability to deter the same in an AMPK-independent signaling route. The processing of SREBP-2 protein was promoted by phorbol 12-myristate 13-acetate (PMA) in the hepatic cells WRL and HepG2, and the increased processing was reversed by apigenin or luteolin co-administration. EMSA results demonstrated that the PMA-induced DNA-binding activity was weakened by the flavones. The increased amount of nuclear SREBP-2 in cells was attenuated by the flavonoid as shown by immunocytochemical imaging. Quantitative reverse transcriptase-polymerase chain reaction assay demonstrated that the transcription of HMGCR under both flavone treatments was reduced. However, apigenin appeared to be stronger than luteolin in restraining PMA-induced HMGCR mRNA expression. Since PMA is a diacylglycerol analog, these findings might have some physiological implications.

The flavone apigenin blocks nuclear translocation of sterol regulatory element-binding protein-2 in the hepatic cells WRL-68.

Sterol regulatory element-binding protein-2 (SREBP-2) is a pivotal transcriptional factor in cholesterol metabolism. Factors interfering with the proper functioning of SREBP-2 potentially alter plasma lipid concentrations. Consuming fruits and vegetables is associated with beneficial plasma lipid profile. The mechanism by which plant foods induce desirable lipid changes remains unclear. Apigenin, a common plant food flavonoid, was shown to modulate the nuclear translocation of SREBP-2 in the hepatic cells WRL-68 in the present study. The processing of SREBP-2 protein occurred after translation, and apigenin blocked this activation route. Further examination indicated that AMP-activated protein kinase (AMPK) was activated by the flavone, and co-administrating the AMPK-specific inhibitor compound C could release the blockage. Reporter gene assay revealed that the transactivation of sterol responsive element (SRE)-containing 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) promoter was suppressed by the flavone. Similarly, electromobility shift assay result also demonstrated a reduced DNA-binding activity on the SRE domain under the same treatment. The reduced transactivity and DNA-binding activity could be attributed to a decreased amount of SREBP-2 translocating from cytosol to nucleus as depicted by confocal microscopy. Quantitative RT-PCR assay demonstrated that the transcription of HMGCR followed the same pattern of SREBP-2 translocation. In summary, the present study showed that apigenin prevented SREBP-2 translocation and reduced the downstream gene HMGCR transcription. The minimum effective dosage should be achievable in the form of functional food consumption or dietary supplementation.

Coadministrating luteolin minimizes the side effects of the aromatase inhibitor letrozole.

Aromatase inhibitors (AIs) have been used as adjuvant therapeutic agents for breast cancer. Their adverse side effect on blood lipid is well documented. Some natural compounds have been shown to be potential AIs. In the present study, we compared the efficacy of the flavonoid luteolin to the clinically approved AI letrozole (Femara; Novartis Pharmaceuticals, East Hanover, NJ) in a cell and a mouse model. In the in vitro experimental results for aromatase inhibition, the Ki values of luteolin and letrozole were estimated to be 2.44 µM and 0.41 nM, respectively. Both letrozole and luteolin appeared to be competitive inhibitors. Subsequently, an animal model was used for the comparison. Aromatase-expressing MCF-7 cells were transplanted into ovariectomized athymic mice. Luteolin was given by mouth at 5, 20, and 50 mg/kg, whereas letrozole was administered by intravenous injection. Similar to letrozole, luteolin administration reduced plasma estrogen concentrations and suppressed the xenograft proliferation. The regulation of cell cycle and apoptotic proteins-such as a decrease in the expression of Bcl-xL, cyclin-A/D1/E, CDK2/4, and increase in that of Bax-was about the same in both treatments. The most significant disparity was on blood lipids. In contrast to letrozole, luteolin increased fasting plasma high-density lipoprotein concentrations and produced a desirable blood lipid profile. These results suggested that the flavonoid could be a coadjuvant therapeutic agent without impairing the action of AIs.

Celecoxib increases miR-222 while deterring aromatase-expressing breast tumor growth in mice.

BACKGROUND: Breast cancer is one of the most deadly diseases in women. Inhibiting the synthesis of estrogen is effective in treating patients with estrogen-responsive breast cancer. Previous studies have demonstrated that use of cyclooxygenase (COX) inhibitors is associated with reduced breast cancer risk. METHODS: In the present study, we employed an established mouse model for postmenopausal breast cancer to evaluate the potential mechanisms of the COX-2 inhibitor celecoxib. Aromatase-expressing MCF-7 cells were transplanted into ovariectomized athymic mice. The animals were given celecoxib at 1500 ppm or aspirin at 200 ppm by oral administration with androstenedione injection. RESULTS: Our results showed that both COX inhibitors could suppress the cancer xenograft growth without changing the plasma estrogen level. Protein expression of ERα, COX-2, Cyclin A, and Bcl-xL were reduced in celecoxib-treated tumor samples, whereas only Bcl-xL expression was suppressed in those treated with aspirin. Among the breast cancer-related miRNAs, miR-222 expression was elevated in samples treated with celecoxib. Further studies in culture cells verified that the increase in miR-222 expression might contribute to ERα downregulation but not the growth deterrence of cells. CONCLUSION: Overall, this study suggested that both celecoxib and aspirin could prevent breast cancer growth by regulating proteins in the cell cycle and apoptosis without blocking estrogen synthesis. Besides, celecoxib might affect miR expression in an undesirable fashion.

Bisphenol A differentially activates protein kinase C isoforms in murine placental tissue.

Bisphenol A is utilized to make polycarbonate plastics and is an environmental pollutant. Recent research has indicated that it is an endocrine disruptor and may interfere with reproductive processes. Our lab has previously shown that bisphenol A could regulate corticotrophin releasing hormone and aromatase in cultured placental cells. In the present study, the effect of bisphenol A on these two genes in the placenta was investigated in mice. Pregnant ICR mice were gavaged with bisphenol A at 2, 20 and 200mg/kg body weight/day from E13 to E16 and were euthanized at E17. Compared to the control mice, increased plasma estrogen and corticotrophin releasing hormone were observed in bisphenol A-treated mice. Messenger RNA quantification indicated that placental crh but not cyp19 was induced in mice treated with bisphenol A. Tracking the related signaling pathway, we found that protein kinase C ζ/λ and δ were activated in the placentas of bisphenol A-treated mice. As the gene promoter of crh contains CRE and the half site of ERE, either phospho-PKC or estrogen could stimulate the gene transactivation. These results indicate that bisphenol A might increase plasma concentrations of estradiol, testosterone, corticotrophin releasing hormone and placental phospho-PKC ζ/λ and δ in mice. Ultimately, the incidence of premature birth in these mice could increase.

The citrus flavanone naringenin suppresses CYP1B1 transactivation through antagonising xenobiotic-responsive element binding.

Exposure to environmental toxicants or exogenous oestrogen increases the risk of cancer. Some toxicants such as polycyclic aromatic hydrocarbons (PAH) undergo biotransformation to become genotoxic agents. Cytochrome p450 (CYP) 1B1 is an enzyme catalysing this transformation. Consumption of fruit and vegetables is considered to be protective against carcinogenesis, and naringenin can be found abundantly in citrus fruits. In the present study, the effect of naringenin on the regulation of CYP1B1 was investigated in MCF-7 cells. Enzyme inhibition assays revealed that naringenin inhibited CYP1B1 at or above 5 µm but not CYP1A1 activity. Quantitative PCR analysis also demonstrated that 1 µm-naringenin reduced CYP1B1 mRNA expression induced by 7,12-dimethylbenz(α)anthracene (DMBA). Further study illustrated that the suppression was at the transcriptional level. Since previous studies have shown that oestrogen response element (ERE) and xenobiotic-responsive element (XRE) are functional binding sequences in the promoter region of CYP1B1, interference of DNA binding on these two elements was pursued. Employing reporter gene assays as well as the electromobility shift assay, we verified that naringenin counteracted DMBA-induced XRE binding at − 1675. These results supported the notion that fruit consumption could be a protective measure against PAH biotransformation.

The mycoestrogen zeranol at high dosage antagonizes transient receptor potential channel activities in 3T3 L1 cells.

Recent findings have revealed that exposure to environmental contaminants may result in obesity and pose a health threat to the general public. As the activity of transient receptor potential channels (TRPs) plays a permissive role in adipogenesis, the interactions between TRPs and some food pollutants, i.e. bisphenol A, di (2-ethylhexyl) phthalate, zearalenone, and zeranol at 10 µM were investigated in the present study. TRP-V1,-V3, -C4 and -C6 are reported to be differentially expressed in the adipocyte differentiation, and immunoblotting was performed to quantify changes in these TRPs affected by the pollutants. Our result indicated that the mycoestrogen zeranol or α-zearalanol suppressed the expression of the V1 and C6 isoforms. Subsequently, confocal microscopy was used to measure the calcium inflow repressed by zeranol from 0.1 µM to 10 µM. Oil Red O staining was used to determine the differentiation of 3T3 L1 preadipocytes. Zeranol could suppress the expression of TRP-V1 and -C6 protein and inhibit the associated flow of calcium into the cytosol of 3T3 L1 cells. Its IC50 value for inhibiting calcium inflow stimulated by 40 µM capsaicin or 10 µM GSK1702934A was estimated to be around 6 µM. Reduced TRP-V1 or -C6 activity might result in promoting adipogenesis. In conclusion, this study demonstrated that zeranol could potentiate fat cell differentiation through antagonizing TRP-V1 and -C6 activities.

The licorice flavonoid isoliquiritigenin suppresses phorbol ester-induced cyclooxygenase-2 expression in the non-tumorigenic MCF-10A breast cell line.

Cyclooxygenase (COX) is the rate-limiting enzyme for the conversion of prostaglandins from arachidonic acid. Upregulation of COX-2 has been well documented during tumorigenesis and metastasis of breast cancer. Isoliquiritigenin (ILN), a flavonoid isolated from licorice (the rhizomes of GLYCYRRHIZA GLABRA, a member of the bean plant family), is known to be a potential suppressor of COX-2 expression. This study focuses on phorbol ester-induced COX-2 expression in the non-tumorigenic MCF-10A cells. Real-time PCR and Western blotting indicated that ILN at 5 microM or above significantly inhibited phorbol 12-myristate 13-acetate (PMA)-induced COX-2 expression in the breast cells. The activated PKC alpha appeared to be not affected, whereas its downstream mitogen-activated protein kinase (MAPK) ERK-1/2 was deactivated. ERK can activate the transcriptional factor binding of AP-1 or CRE, which can be located at the COX-2 promoter region (- 72/- 53). Electrophoretic mobility shift assays illustrated that ILN suppressed DNA binding at this region. The shifted bands could be competed off with consensus sequences of AP-1 and CRE, and the supershift assay demonstrated that CREB-1 instead of c-Jun was responsible for the binding. This study showed that ILN downregulated PMA-induced COX-2 expression by modulating ERK-1/2 signaling, a finding that may be relevant to the disease prevention properties of licorice.

The livestock growth-promoter zeranol facilitates GLUT4 translocation in 3T3 L1 adipocytes.

Zeranol is an approved but controversial growth-promoting agent for livestock in North America. It is a mycotoxin metabolite secreted by the Fusarium family fungi. The regulatory bodies in this region have established the acceptable daily intake and exposure below the level would not significantly increase the health risk for humans. However, their European counterparts have yet to establish an acceptable level and do not permit the use of this agent in farm animals. Given the growth-promoting ability of zeranol, its effect on energy metabolism was investigated in the current study. Our results indicated that zeranol could induce glucose transporter type 4 (GLUT4) expression in 3T3 L1 cells at 10 µM and initiate the translocation of the glucose transporter to the membrane as assayed by confocal microscopy. The translocation was likely triggered by the increase of GLUT4 and p-Akt. The insulin signal transduction pathway of glucose translocation was analyzed by Western blot analysis. Since no increase in the phosphorylated insulin receptor substrate in zeranol-treated cells was evidenced, the increased p-Akt and GLUT4 amount should be the mechanism dictating the GLUT4 translocation. In summary, this study showed that zeranol could perturb glucose metabolism in differentiated 3T3 L1 adipocytes. Determining the growth-promoting mechanism is crucial to uncover an accepted alternative to the general public.

Dietary administration of the licorice flavonoid isoliquiritigenin deters the growth of MCF-7 cells overexpressing aromatase.

Licorice is the sweet-tasting rhizomes of a bean plant and is quite commonly used in Western countries for culinary purposes, while it is a medicinal herb in China. Many flavonoids have been isolated from licorice, and their pharmacological properties may be applicable in preventive medicine. Overexposure to estrogen has been implicated in the etiology of breast cancer, and cytochrome P450 (CYP) 19 enzyme, or aromatase, catalyzes the rate-limiting reaction. Phytocompounds that are able to inhibit this enzyme may potentially suppress breast cancer development. In the present study the licorice flavonoid isoliquiritigenin (ILN) was shown to be an aromatase inhibitor in recombinant protein and MCF-7 cells stably transfected with CYP19 (MCF-7aro). ILN displayed a K(i) value of around 3 muM, and it also blocked the MCF-7aro cell growth pertaining to the enzyme activity in vitro. Subsequently, the compound administered in diet was given to ovariectomized athymic mice transplanted with MCF-7aro cells. This mouse model is widely accepted for studying postmenopausal breast cancer. The phytochemical significantly deterred the xenograft growth without affecting the body weight. Subsequently, the flavonoid's effect on CYP19 transcriptional control in vitro was also investigated. At the mRNA level, ILN could also suppress the expression in wild-type MCF-7 cells. Reporter gene assay and real-time PCR verified that the transactivity of CYP19 driven by promoters I.3 and II was suppressed in these cells. Deactivation of C/EBP could be the underlying molecular mechanism. Our study demonstrated that ILN was an inhibitor of aromatase and a potential chemopreventive agent against breast cancer.

The soy isoflavone genistein induces estrogen synthesis in an extragonadal pathway.

Genistein is a phytoestrogen isolated from soyabean, and is a potential nutraceutical gearing for women suffering from perimenopausal symptoms. Because of its differential binding affinity to estrogen receptor (ER) isoforms, genistein is described as a selective estrogen receptor modulator (SERM). The ligand-receptor interaction is established, but the potential confounding factors have not been fully addressed. Alteration in estrogen metabolism is an important issue when determining the downstream effect of ER. Aromatase or CYP19 catalyzes the rate-limiting reaction of estrogen synthesis, and is highly expressed in the ovary. This organ is the source of estrogen in females. After menopause the ovaries cease to produce the hormone, and localized estrogen synthesis in extragonadal tissues could become physiologically significant. In the present study, effect of genistein on CYP19 regulation was investigated in the hepatic cells HepG2. The phytoestrogen induced aromatase activity in the cells. Increased mRNA expression with concurrent elevation in the usage of promoters I.3/II was also demonstrated. Luciferase reporter gene assays verified the transcriptional control dictated by the specific promoters under genistein treatment. Several protein kinases were examined, and PKC?, P38, ERK-1/2 appeared to be activated. Subsequent inhibition and expression experiments demonstrated the involvement of these kinases. The transcriptional factor CREB was ultimately activated in the gene regulation. The present study illustrated an extragonadal pathway by which genistein might increase estrogen synthesis.

The red wine polyphenol resveratrol reduces polycyclic aromatic hydrocarbon-induced DNA damage in MCF-10A cells.

Polycyclic aromatic hydrocarbons (PAH) are procarcinogens that can be commonly found in our food and environment. Upon biotransformation in our body system, they can cause DNA damage through the generation of genotoxic species and oxidative stress. Phase I and II enzymes are pivotal in the process of proximate carcinogen formation and elimination. Some dietary phytochemicals are strong inhibitors to the phase I enzymes. In the present study, we investigated the effect of the red wine compound resveratrol on DNA damage induced by PAH in a non-tumorigenic breast cell line MCF-10A. Resveratrol ranging from 1 to 5 microm could significantly suppress the expressions of cytochrome P450 (CYP) 1A1, CYP1B1 and UDP-glucuronosyltransferase (UGT) 1A1 induced by 7,12-dimethylbenz[a]anthracene (DMBA). The comet assay indicated that DMBA introduced DNA damage to these cells, and co-treatment of resveratrol at 5 or 10 microm could alleviate the damage. Further investigation illustrated that resveratrol reduced the binding of DMBA metabolites to DNA with no effect on DMBA-induced oxidative DNA damage. Since the phase II enzyme UGT1A1 was suppressed, the elimination of DMBA metabolites would not have contributed to the reduction in the DMBA metabolite-DNA binding. In summary, resveratrol might protect breast cells against PAH-induced DNA damage. The underlying mechanism was mediated by phase I enzyme suppression rather than phase II enzyme induction or oxidative DNA repair.

Genistein protects against polycyclic aromatic hydrocarbon-induced oxidative DNA damage in non-cancerous breast cells MCF-10A.

Polycyclic aromatic hydrocarbons (PAH) are established cancer initiators that can be found in our food and environment. Some dietary phytochemicals are strong inhibitors of PAH-induced mutagenesis. The soya isoflavone genistein has been shown previously in our laboratory to be an inhibitor of PAH metabolite binding to DNA. In the present study, we investigated the effect of genistein on oxidative DNA damage induced by PAH in the non-tumorigenic breast cell line MCF10A. 7,12-Dimethyl-benz[a]anthracene (DMBA) can induce expressions of CYP1A1 and CYP1B1 which are known to be responsive to PAH. These enzymes, in turn, will metabolise the PAH into their ultimate carcinogenic forms. Genistein can significantly suppress the expressions within 5 microm. The comet assay indicated that DMBA introduced DNA damage to these cells, and co-treatment with genistein at 5 or 10 microm could alleviate the damage. In addition to the chelation of DMBA metabolites to DNA, flow cytometry results revealed that oxidation was also a factor of DNA damage. The oxidative DNA damage could be removed by co-treating with 10 microm-genistein. Because no increased oxidative DNA repair was observed, suppression on the cytochrome enzymes appeared to be the underlying mechanism.

A positive feedback pathway of estrogen biosynthesis in breast cancer cells is contained by resveratrol.

Cytochrome P450 (CYP) 19 enzyme or aromatase catalyses the rate-determining step of estrogen synthesis. The transcriptional control of CYP19 gene is highly specific in different cell types, for instance, Promoter I.3/II is commonly used for regulation in breast cancer cells. Recently, a positive feedback pathway for estrogen synthesis has been identified in ER alpha expressing SK-BR-3 cells. CYP19 mRNA abundance and activity are increased in this pathway and the promoter usage is switched from Promoter I.3/II to I.1 through a non-genomic process. In the present study, effect of the phytocompound resveratrol on this Promoter I.1-controlled expression of aromatase was investigated. Results indicated that resveratrol reduced the estradiol-induced mRNA abundance in SK-BR-3 cells expressing ER alpha. Luciferase reporter gene assays revealed that resveratrol could also repress the transcriptional control dictated by Promoter I.1. Since the ERE-driven luciferase activity was not repressed by resveratrol, the nuclear events of estrogen were unlikely to be suppressed by resveratrol. Instead the phytochemical reduced the amount of ERK activated by estradiol, which could be the pathway responsible for Promoter I.1 transactivation and the induced CYP19 expression. The present study illustrated that resveratrol impeded the non-genomic induction of estrogen on CYP19.

The citrus flavonone hesperetin attenuates the nuclear translocation of aryl hydrocarbon receptor.

The environmental polycyclic aromatic hydrocarbons (PAH) and dioxins are carcinogens and their adverse effects have been largely attributed to the activation of AhR. Hesperetin is a flavonone found abundantly in citrus fruits and has been shown to be a biologically active agent. In the present study, the effect of hesperetin on the nuclear translocation of AhR and the downstream gene expression was investigated in MCF-7 cells. Confocal microscopy indicated that 7, 12-dimethylbenz[α]anthracene (DMBA) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) -induced nuclear translocation of AhR was deterred by hesperetin treatment. The reduced nuclear translocation could also be observed in Western analysis. Reporter-gene assay further illustrated that the induced XRE transactivation was weakened by the treatment of hesperetin. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assay demonstrated that the gene expressions of CYP1A1, 1A2, and 1B1 followed the same pattern of AhR translocation. These results suggested that hesperetin counteracted AhR transactivation and suppressed the downstream gene expression.

Co-administrating apigenin in a high-cholesterol diet prevents hypercholesterolaemia in golden hamsters.

OBJECTIVES: Hypercholesterolaemia is a major risk factor for developing atherosclerosis. Increased consumption of fruits and vegetables is recommended to hypercholesterolaemic patients. In this study, the hypocholesterolaemic effect of apigenin and luteolin was evaluated in a hamster model. METHODS: Hamsters were put on a high-cholesterol diet for 9 weeks, and apigenin or luteolin was administered in the diet at 60 and 300 ppm. KEY FINDINGS: Both apigenin and luteolin supplementations could attenuate the aorta plaque formation by 30% and 20%, respectively. Apigenin-fed hamsters at both dosages displayed a 1.5-fold increase in hepatic Ldlr expression and a 40% reduction in non-HDL cholesterol level as compared with those in the control fed a high-cholesterol (HC) diet. Besides, faecal elimination of cholesterol was facilitated by 20% in the hamsters with high apigenin consumption. Suppressing the expression of the cholesterol transporter ncp1l1 in the intestinal mucosa could block the cholesterol absorption and promote its elimination. The differential regulations of ncp1l1 and Ldlr appeared to be the underlying hypocholesterolaemic mechanism of apigenin in this model system. Luteolin supplementation, on the other hand, had no effect on the blood cholesterol. CONCLUSIONS: This study illustrated that dietary administration of apigenin attenuated HC feeding-induced hypercholesterolemia in hamsters.

PCP4/PEP19 upregulates aromatase gene expression via CYP19A1 promoter I.1 in human breast cancer SK-BR-3 cells.

The Purkinje cell protein 4/peptide 19 (PCP4/PEP19) is a novel breast cancer cell expressing peptide, originally found in the neural cells as an anti-apoptotic factor, could inhibit cell apoptosis and enhance cell migration and invasion in human breast cancer cell lines. The expression of PCP4/PEP19 is induced by estrogens in estrogen receptor-positive (ER+) MCF-7 cells but also highly expressed in ER- SK-BR-3 cells. In this study, we investigated the effects of PCP4/PEP19 on aromatase gene expression in MCF-7 and SK-BR-3 human breast cancer cells. In SK-BR-3 cells but not in MCF-7 cells, PCP4/PEP19 knockdown by siRNA silencing decreased the aromatase expression in gene transcriptional level. When PCP4/PEP19 was overexpressed by CMV promoter-driven PCP4/PEP19 expressing plasmid transfection, aromatase gene transcription increased in SK-BR-3 cells. This aromatase gene transcription is mainly mediated through promoter region PI.1, which is usually active in the placental tissue but not in the breast cancer tissue. These results indicate a new function of PCP4/PEP19 that would enhance aromatase gene upregulation to supply estrogens in heterogeneous cancer microenvironment.

Differential effect of over-expressing UGT1A1 and CYP1A1 on xenobiotic assault in MCF-7 cells.

Gene mutation has been considered as a major step of carcinogenesis. Some defective genes may induce spontaneous tumorigenesis, while others are required to interact with the environment to induce cancer. CYP1A1 and UGT1A1 are encoded for the respective phase I and II drug-metabolizing enzymes. Their expressions have been associated with breast cancer incidence in women, and some xenobiotics are substrates of these two enzymes. In the current study, cytochrome P450 (CYP) 1A1 and UDP-glucuronosyltransferase (UGT) 1A1 were over-expressed in the breast cancer MCF-7 cells, and potential interactions between these enzymes and estrogen or polycyclic aromatic hydrocarbon were evaluated. Compared with control cells (MCF-7(VEC)), reduced cell proliferation was seen in cells expressing UGT1A1 (MCF-7(UGT1A1)) under estradiol treatment. 7,12-Dimethylbenz[a]anthracene (DMBA) is an established breast cancer initiator in animal model. Over-expressing UGT1A1 reduced the binding of DMBA to DNA, and increased MCF-7(UGT1A1) intact cells under DMBA treatment was verified by comet assay. On the other hand, intensified DMBA binding and damages were observed in MCF-7(CYP1A1) cells. This study supported that UGT1A1 but not CYP1A1 expression could protect against xenobiotic assault.

Pharmacological concentration of resveratrol suppresses aromatase in JEG-3 cells.

Estrogen is crucial in preparing of pregnancy, and its role in the maintenance of pregnancy has yet to be elucidated. During the course of pregnancy, the placenta is responsible for the provision of estrogen. The hormone biosynthesis is catalyzed by cytochrome P450 (CYP) 19 or aromatase. In the present study, we screened several common dietary components and identified the grape polyphenol resveratrol to be a potential inhibitor in the hormone synthesis. In a recombinant protein system resveratrol inhibited the aromatase activity with an IC(50) value of approximately 40 microM. Subsequent analysis was performed in the human placental JEG-3 cells, and 25 microM resveratrol significantly reduced the mRNA abundance in these cells. Since the transcriptional control of CYP19 gene is tissue-specific and the proximal promoter region of exon Ia has previously been shown to be crucial in CYP19 expression in placental cells, we also evaluated the promoter activity of this gene. Reporter gene assays revealed that resveratrol repressed the transcriptional control of promoter Ia. The present study illustrated the possibility that dietary supplementation of resveratrol interfered with the normal functioning of placental cells.