Polyphenol-mediated inhibition of AP-1 transactivating activity may slow cancer growth by impeding angiogenesis and tumor invasiveness

Procyanidins from wild grape (Vitis amurensis) seeds regulate ARE-mediated enzyme expression via Nrf2 coupled with p38 and PI3K/Akt pathway in HepG2 cells

Procyanidins, polymers of flavan-3-ol units, have been reported to exhibit many beneficial health effects such as antioxidant and anti-carcinogenic effects. In this study, we investigated the cancer chemopreventive properties of procyanidins from wild grape (Vitis amurensis) seeds in particular their roles in inducing phase II detoxifying/antioxidant enzymes as well as in modulating the upstream kinases. Ethanolic extract of V. amurensis seeds was fractionated with a series of organic solvents and finally separated into six fractions, F1–F6. Chemical properties of the procyanidins were analyzed by vanillin assay, BuOH-HCl test, and depolymerization with phloroglucinol followed by LC/MS analysis. The F5 had the highest procyanidin content among all the fractions and strongly induced the reporter activity of antioxidant response element as well as the protein expression of nuclear factor E2-related factor (Nrf2) in HepG2 human hepatocarcinoma cells. The procyanidin-rich F5 also strongly induced the expression of the phase II detoxifying and antioxidant enzymes such as NAD(P)H:quinone oxidoreductase1 and hemeoxygenase1. Phosphorylations of the upstream kinases such as MAPKs and PI3K/Akt were significantly increased by treatment with procyanidin fraction. In addition, the procyanidin-mediated Nrf2 expression was partly attenuated by PI3K inhibitor LY294002, and almost completely by p38 inhibitor SB202190, but neither by JNK inhibitor SP600125 nor by MEK1/2 inhibitor U0126. Taken together, the procyanidins from wild grape seeds could be used as a potential natural chemopreventive agent through Nrf2/ARE-mediated phase II detoxifying/antioxidant enzymes induction via p38 and PI3K/Akt pathway.

Plant polyphenols in cancer and heart disease: implications as nutritional antioxidants

Certain dietary antioxidants such as vitamin E and vitamin C are important for maintaining optimum health. There is now much interest in polyphenolic products of the plant phenylpropanoid pathway as they have considerable antioxidant activity in vitro and are ubiquitous in our diet. Rich sources include tea, wine, fruits and vegetables although levels are affected by species, light, degree of ripeness, processing and storage. This confounds the formulation of databases for the estimation of dietary intakes. Most attention to date has focused on the flavonoids, a generic term which includes chalcones, flavones, flavanones, flavanols and anthocyanins. There is little convincing epidemiological evidence that intakes of polyphenols are inversely related to the incidence of cancer whereas a number of studies suggest that high intakes of flavonoids may be protective against CHD. In contrast, numerous cell culture and animal models indicate potent anticarcinogenic activity by certain polyphenols mediated through a range of mechanisms including antioxidant activity, enzyme modulation, gene expression, apoptosis, upregulation of gap junction communication and P-glycoprotein activation. Possible protective effects against heart disease may be due to the ability of some polyphenols to prevent the oxidation of LDL to an atherogenic form although anti-platelet aggregation activity and vasodilatory properties are also reported. However, some polyphenols are toxic in mammalian cells. Thus, until more is known about their bioavailability, metabolism and intracellular location, increasing intakes of polyphenols by supplements or food fortification may be unwise.

Loss of endogenous interleukin-12 activates survival signals in ultraviolet-exposed mouse skin and skin tumors

Interleukin-12 (IL-12)-deficiency promotes photocarcinogenesis in mice; however, the molecular mechanisms underlying this effect have not been fully elucidated. Here, we report that long-term exposure to ultraviolet (UV) radiation resulted in enhancement of the levels of cell survival kinases, such as phosphatidylinositol 3-kinase (PI3K), Akt (Ser(473)), p-ERK1/2, and p-p38 in the skin of IL-12p40 knockout (IL-12 KO) mice compared with the skin of wild-type mice. UV-induced activation of nuclear factor-kappaB (NF-kappaB)/p65 in the skin of IL-12 KO mice was also more prominent. The levels of NF-kappaB-targeted proteins, such as proliferating cell nuclear antigen (PCNA), cyclooxygenase-2, cyclin D1, and inducible nitric oxide synthase, were higher in the UV-exposed skin of IL-12 KO mice than the UV-exposed skin of wild types. In short-term UV irradiation experiments, subcutaneous treatment of IL-12 KO mice with recombinant IL-12 (rIL-12) or topical treatment with oridonin, an inhibitor of NF-kappaB, resulted in the inhibition of UV-induced increases in the levels of PCNA, cyclin D1, and NF-kappaB compared with non-rIL-12- or non-oridonin-treated IL-12 KO mice. UV-induced skin tumors of IL-12 KO mice had higher levels of PI3K, p-Akt (Ser(473)), p-ERK1/2, p-p38, NF-kappaB, and PCNA and fewer apoptotic cells than skin tumors of wild types. Together, these data suggest that the loss of endogenous IL-12 activates survival signals in UV-exposed skin and that may lead to the enhanced photocarcinogenesis in mice.

Green tea: nature's defense against malignancies

The current practice of introducing phytochemicals to support the immune system or fight against diseases is based on centuries old traditions. Nutritional support is a recent advancement in the domain of diet-based therapies; green tea and its constituents are one of the important components of these strategies to prevent and cure various malignancies. The anti-carcinogenic and anti-mutagenic activities of green tea were highlighted some years ago suggesting that it could reduce the prevalence of cancer and even provide protection. The pharmacological actions of green tea are mainly attributed to polyphenols that includes epigallocatechin-3-gallate (EGCG), epicatechin, epicatechin-3-gallate, epigallocatechin. Green tea and its components effectively mitigate cellular damage arising due to oxidative stress. Green tea is supposed to enhance humoral and cell-mediated immunity, decreasing the risk of certain cancers, and may have certain advantage in treating inflammatory disorders. Much of the cancer chemopreventive properties of green tea are mediated by EGCG that induces apoptosis and promotes cell growth arrest, by altering the expression of cell cycle regulatory proteins, activating killer caspases, and suppressing nuclear factor kappa-B activation. Besides, it regulates and promotes IL-23 dependent DNA repair and stimulates cytotoxic T cells activities in a tumor microenvironment. It also blocks carcinogenesis by modulating the signal transduction pathways involved in cell proliferation, transformation, inflammation and metastasis. The review is intended to highlight the chemistry of green tea, its antioxidant potential, its immunopotentiating properties and mode of action against various cancer cell lines that showed its potential as a chemopreventive agent against colon, skin, lung, prostate, and breast cancer.

Multi-targeted prevention and therapy of cancer by proanthocyanidins

In recent years, a considerable emphasis has been focused on the importance of the naturally available botanicals that can be consumed in an individual's everyday diet and that can also be useful as a chemopreventive or chemotherapeutic agent for certain diseases, including cancers. A wide variety of botanicals, mostly dietary flavonoids or polyphenolic substances, have been reported to possess substantial anti-carcinogenic and antimutagenic activities because of their antioxidant and anti-inflammatory properties. Proanthocyanidins are considered as one of them, and are abundantly available in various parts of the plants, such as fruits, berries, bark and seeds. Their modes of action were evaluated through a number of in vitro and in vivo studies which showed their potential role as anti-carcinogenic agent. We summarize and highlight the latest developments on anti-carcinogenic activities of proanthocyanidins from different sources, specifically from grape seeds, and their molecular targets, such as NF-kappaB, mitogen-activated protein kinases, PI3K/Akt, caspases, cytokines, angiogenesis and cell cycle regulatory proteins and other check points, etc. Although the bioavailability and metabolism data on proanthocyanidins is still largely unavailable, certain reports indicate that at least monomers and smaller oligomeric procyanidins are absorbed in the gut. The modulation of various molecular targets by proanthocyanidins in vitro and in vivo tumor models suggests their importance, contribution and mechanism of action to the prevention of cancers of different organs.

Redox signals in wound healing

Physical trauma represents one of the most primitive challenges that threatened survival. Healing a problem wound requires a multi-faceted comprehensive approach. First and foremost, the wound environment will have to be made receptive to therapies. Second, the appropriate therapeutic regimen needs to be identified and provided while managing systemic limitations that could secondarily limit the healing response. Unfortunately, most current solutions seem to aim at designing therapeutic regimen with little or no consideration of the specific details of the wound environment and systemic limitations. One factor that is centrally important in making the wound environment receptive is correction of wound hypoxia. Recent work have identified that oxygen is not only required to disinfect wounds and fuel healing but that oxygen-dependent redox-sensitive signaling processes represent an integral component of the healing cascade. Over a decade ago, it was proposed that in biological systems oxidants are not necessarily always the triggers for oxidative damage and that oxidants such as H2O2 could actually serve as signaling messengers and drive several aspects of cellular signaling. Today, that concept is much more developed and mature. Evidence supporting the role of oxidants such as H2O2 as signaling messenger is compelling. A complete understanding of the continuum between the classical and emergent roles of oxygen requires a thorough consideration of current concepts in redox biology. The objective of this review is to describe our current understanding of how redox-sensitive processes may drive dermal tissue repair.

Redox regulation of the VEGF signaling path and tissue vascularization: Hydrogen peroxide, the common link between physical exercise and cutaneous wound healing

Vascularization, under physiological or pathophysiological conditions, typically takes place by one or more of the following processes: angiogenesis, vasculogenesis, arteriogenesis, and lymphangiogenesis. Although all of these mechanisms of vascularization have sufficient contrasting features to warrant consideration under separate cover, one common feature shared by all is their sensitivity to the VEGF signaling pathway. Conditions such as wound healing and physical exercise result in increased production of reactive oxygen species such as H(2)O(2), and both are associated with increased tissue vascularization. Understanding these two scenarios of adult tissue vascularization in tandem offers the potential to unlock the significance of redox regulation of the VEGF signaling pathway. Does H(2)O(2) support tissue vascularization? H(2)O(2) induces the expression of the most angiogenic form of VEGF, VEGF-A, by a HIF-independent and Sp1-dependent mechanism. Ligation of VEGF-A to VEGFR2 results in signal transduction leading to tissue vascularization. Such ligation generates H(2)O(2) via an NADPH oxidase-dependent mechanism. Disruption of VEGF-VEGFR2 ligation-dependent H(2)O(2) production or decomposition of such H(2)O(2) stalls VEGFR2 signaling. Numerous antioxidants exhibit antiangiogenic properties. Current evidence lends firm credence to the hypothesis that low-level endogenous H(2)O(2) supports vascular growth.

Dietary grape seed proanthocyanidins inhibit UVB-induced oxidative stress and activation of mitogen-activated protein kinases and nuclear factor-κB signaling in in vivo SKH-1 hairless mice

We have shown previously that dietary grape seed proanthocyanidins (GSP) inhibit UVB-induced photocarcinogenesis in mice. As UVB-induced oxidative stress and oxidative stress-mediated signaling has been implicated in photocarcinogenesis, this study was designed to investigate the effect of dietary GSPs on UVB-induced oxidative stress in in vivo SKH-1 hairless mice. Here, we report that provision of dietary GSPs (0.2 and 0.5%, w/w) to mice exposed to either acute UVB irradiation (120 mJ/cm(2)) or chronic irradiation of UVB inhibited depletion of glutathione peroxidase, catalase, and glutathione, and inhibited UVB-induced H(2)O(2), lipid peroxidation, protein oxidation, and nitric oxide in mouse skin. As UV-induced oxidative stress mediates activation of mitogen-activated protein kinase (MAPK) and nuclear factor-kappaB (NF-kappaB) signaling pathways, we determined the effect of dietary GSPs on these pathways. We observed that dietary GSPs inhibited UVB-induced phosphorylation of extracellular signal-regulated kinase 1/2, c-Jun-NH(2)-kinase, and p38 proteins of MAPK family, which seems to be mediated through reactivation of MAPK phosphatases. GSPs inhibited UVB-induced activation of NF-kappaB/p65 through inhibition of degradation of IkappaBalpha and activation of IkappaB kinase alpha (IKKalpha). As NF-kappaB-targeted genes play critical roles in inflammation and cellular proliferation, we assessed the effect of GSPs on proteins encoded by these genes. Dietary GSPs resulted in inhibition of the expression of proliferating cell nuclear antigen, cyclin D1, inducible nitric oxide synthase, and cyclooxygenase-2 in the skin. Collectively, our data show that GSPs have the ability to protect the skin from the adverse effects of UVB radiation via modulation of the MAPK and NF-kappaB signaling pathways and provide a molecular basis for the photoprotective effects of GSPs in an in vivo animal model.

Obesity increases the risk of UV radiation-induced oxidative stress and activation of MAPK and NF-kappaB signaling

Obesity has been implicated in several diseases, including cancer; however, the relationship of obesity and susceptibility to ultraviolet (UV) radiation-caused skin diseases has not been investigated. As UV-induced oxidative stress has been implicated in several skin diseases, we assessed the role of obesity on UVB-induced oxidative stress in genetically obese Lep(ob)/Lep(ob) (leptin-deficient) mice. Here, we report that chronic exposure to UVB (120 mJ/cm(2)) resulted in greater oxidative stress in the skin of obese mice in terms of higher levels of H(2)O(2) and NO production, photo-oxidative damage of lipids and proteins, and greater depletion of antioxidant defense enzymes, like glutathione, glutathione peroxidase, and catalase. As UV-induced oxidative stress mediates activation of MAPK and NF-kappaB signaling pathways, we determined the effects of UVB on these pathways in obese mice. Exposure of obese mice to UVB resulted in phosphorylation of ERK1/2, JNK, and p38 proteins of the MAPK family. Compared to wild-type mice, the obese mice exhibited higher levels of phosphorylation of these proteins, greater activation of NF-kappaB/p65, and higher levels of circulating proinflammatory cytokines, including TNF-alpha, IL-1beta and IL-6, on UVB irradiation. Taking these results together, our study suggests for the first time that obesity in mice is associated with greater susceptibility to UVB-induced oxidative stress and therefore may be a risk factor for skin diseases associated with UVB-induced oxidative stress.

Grape seed proanthocyanidins inhibit UV-radiation-induced oxidative stress and activation of MAPK and NF-kappaB signaling in human epidermal keratinocytes

Solar ultraviolet (UV) radiation-induced oxidative stress has been implicated in various skin diseases. Here, we report the photoprotective effect of grape seed proanthocyanidins (GSPs) on UV-induced oxidative stress and activation of mitogen-activated protein kinase (MAPK) and NF-kappaB signaling pathways using normal human epidermal keratinocytes (NHEK). Treatment of NHEK with GSPs inhibited UVB-induced hydrogen peroxide (H2O2), lipid peroxidation, protein oxidation, and DNA damage in NHEK and scavenged hydroxyl radicals and superoxide anions in a cell-free system. GSPs also inhibited UVB-induced depletion of antioxidant defense components, such as glutathione peroxidase, catalase, superoxide dismutase, and glutathione. As UV-induced oxidative stress mediates activation of MAPK and NF-kappaB signaling pathways, we determined the effects of GSPs on these pathways. Treatment of NHEK with GSPs inhibited UVB-induced phosphorylation of ERK1/2, JNK, and p38 proteins of the MAPK family at the various time points studied. As UV-induced H2O2 plays a major role in activation of MAPK proteins, NHEK were treated with H2O2 with or without GSPs and other known antioxidants, viz. (-)-epigallocatechin-3-gallate, silymarin, ascorbic acid, and N-acetylcysteine. It was observed that H2O2-induced phosphorylation of ERK1/2, JNK, and p38 was decreased by these antioxidants. Under identical conditions, GSPs also inhibited UVB-induced activation of NF-kappaB/p65, which was mediated through inhibition of degradation and activation of IkappaBalpha and IKKalpha, respectively. Together, these results suggest that GSPs could be useful in the attenuation of UV-radiation-induced oxidative stress-mediated skin diseases in human skin.

Dietary polyphenols and the prevention of diseases

Polyphenols are the most abundant antioxidants in the diet and are widespread constituents of fruits, vegetables, cereals, dry legumes, chocolate, and beverages, such as tea, coffee, or wine. Experimental studies on animals or cultured human cell lines support a role of polyphenols in the prevention of cardiovascular diseases, cancers, neurodegenerative diseases, diabetes, or osteoporosis. However, it is very difficult to predict from these results the effects of polyphenol intake on disease prevention in humans. One of the reasons is that these studies have often been conducted at doses or concentrations far beyond those documented in humans. The few clinical studies on biomarkers of oxidative stress, cardiovascular disease risk factors, and tumor or bone resorption biomarkers have often led to contradictory results. Epidemiological studies have repeatedly shown an inverse association between the risk of myocardial infarction and the consumption of tea and wine or the intake level of some particular flavonoids, but no clear associations have been found between cancer risk and polyphenol consumption. More human studies are needed to provide clear evidence of their health protective effects and to better evaluate the risks possibly resulting from too high a polyphenol consumption.

Antioxidants of the beverage tea in promotion of human health

Tea that contains many antioxidants is a pleasant and safe drink that is enjoyed by people across the globe. Tea leaves are manufactured as black, green, or oolong. Black tea represents approximately 78% of total consumed tea in the world, whereas green tea accounts for approximately 20% of tea consumed. The concept of "use of tea for promotion of human health and prevention and cure of diseases" has become a subject of intense research in the last decade. Diseases for which tea drinkers appear to have lower risk are simple infections, like bacterial and viral, to chronic debilitating diseases, including cancer, coronary heart disease, stroke, and osteoporosis. Initial work on green tea suggested that it possesses human health-promoting effects. In recent years, the research efforts have been expanded to black tea as well. Research conducted in recent years reveals that both black and green tea have very similar beneficial attributes in lowering the risk of many human diseases, including several types of cancer and heart diseases. For cancer prevention, evidence is so overwhelming that the Chemoprevention Branch of the National Cancer Institute has initiated a plan for developing tea compounds as cancer-chemopreventive agents in human trials. Thus, modern medical research is confirming the ancient wisdom that therapy of many diseases may reside in an inexpensive beverage in a "teapot."

Inhibition of Lung Carcinogenesis and Effects on Angiogenesis and Apoptosis in A/J Mice by Oral Administration of Green Tea

Oral administration of tea (Camellia sinensis) has been shown to inhibit the formation and growth of several tumor types in animal models. The present study investigated the effects of treatment with different concentrations of green tea on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in female A/J mice. Two days after a single dose of NNK (100 mg/kg body weight, i.p.), the mice were given 0.1, 0.2, 0.4, and 0.6% green tea solution (1, 2, 4, and 6 g of tea solids, respectively, dissolved in 1 l of water), 0.02% caffeine, or water as the sole source of drinking fluid until the termination of the experiment. Only the treatment with 0.6% tea preparation significantly reduced lung tumor multiplicity (mean +/- SE, 6.07 +/- 0.77 vs. 8.60 +/- 0.50 tumors per mouse, P = 0.018). Treatment with 0.6% tea also inhibited angiogenesis, as indicated by the lower microvessel density (number of blood vessels/mm2) based on immunostaining for the von Willebrand factor antigen (81.9 +/- 9.5 vs. 129.4 +/- 8.2, P = 0.0018) and anti-CD31 antibody staining (465.3 +/- 61.4 vs. 657.1 +/- 43.6, P = 0.0012). Significantly lower vascular endothelial growth factor immunostaining scores were also observed in the 0.6% tea-treated group (0.98 +/- 0.17 vs. 1.43 +/- 0.07, P = 0.006). The apoptosis index was significantly higher in lung adenomas from 0.6% tea-treated mice based on morphological analysis of cell apoptosis (2.51 +/- 0.18% vs. 1.57 +/- 0.11%, P = 0.00005), and the result was further confirmed using the TUNEL method. Inhibition of angiogenesis and the induction of apoptosis by green tea may be closely related to the inhibition of pulmonary carcinogenesis.

Penta-O-galloyl-beta-D-glucose inhibits the invasion of mouse melanoma by suppressing metalloproteinase-9 through down-regulation of activator protein-1

Penta-O-galloyl-beta-D-glucose (5GG) inhibited the invasion of highly metastatic mouse melanoma B16F10 cells in vitro, as demonstrated by transwell assay. Its ability to diminish the activity of matrix metalloproteinase (MMP) was demonstrated by zymographic assay. Our data showed 5GG could diminish the activity of MMP-9 more than that of MMP-2. The effect on MMP-9 was elicited in a dose- and time-dependent manner, with IC50 of 15 microM. Next, we analyzed the amounts of MMP-9 and MMP-2 protein in conditioned media and in the cells. The data indicated MMP-9 proteins were also suppressed by 5GG in the same manner. In accordance with these data above, the results of reverse transcriptase polymerase chain reaction (RT-PCR) and Northern blot analysis showed a reduced level of MMP-9 mRNA. Furthermore, we studied transcription factor binding to MMP-2 and MMP-9 promoter regions by electrophoretic mobility shift assay (EMSA) in the nucleus. The results suggested that the transcription factor binding activities of Activator protein-1 (AP-1) and Sp-1 sites was mainly down-regulated by 5GG in the concentration range of 5-15 microM, but not that of nuclear factor kappaB (NF-kappaB), polioma enhancer activator 3 (PEA-3), and Activator protein-2 (AP-2) sites. The Western blot analysis of AP-1 nuclear protein showed a reduced level of c-Jun but not of c-Fos. In addition, the expression of Sp-1 and c-Jun protein was also suppressed. To elucidate whether the transcriptional activity of AP-1 or Sp-1 sites is more important, we transfected MMP-9/luciferase reporter vector, under MMP-9 promoter control, into the cells. We found that a decreased transcriptional activity of AP-1 sites is sufficient to reduce MMP-9 promoter activity. These results lead us to conclude that 5GG restricts the invasive ability of B16F10 mouse melanoma cells by reducing MMP-9 activity, by suppressing the transcriptional activity of AP-1 sites and the expression of c-Jun protein. The result may provide a potential mechanism for 5GG in cancer chemopreventive action.

Mechanisms of chronic disease causation by nutritional factors and tobacco products and their prevention by tea polyphenols

The beverage tea, from the top leaves of the plant Camellia sinensis is one of the most widely used beverages in the world, second only to water. Black and green tea have mostly similar actions. The active components are polyphenols, mainly epigallocatechin gallate in green tea, and the tea leaf polyphenol oxidase mediated oxidation to oolong and black tea, yielding other polyphenols, theaflavin and thearubigins. There is 40-50 mg caffeine in a 160-ml cup of tea. The chemopreventive effects of tea depend on: (1) its action as an antioxidant; (2) the specific induction of detoxifying enzymes; (3) its molecular regulatory functions on cellular growth, development and apoptosis; and (4) a selective improvement in the function of the intestinal bacterial flora. The oxidation of LDL cholesterol, associated with a risk for atherosclerosis and heart disease, is inhibited by tea. Many of cancers are caused by lifestyle elements. One is cigarette and tobacco use, leading to cancer in the oral cavity, esophagus and lung, inhibited by tea. Mice administered a tobacco nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), developed significantly fewer lung tumors than controls when given green tea or its major polyphenol, epigallocatechin gallate (EGCG). Tea suppressed the formation of 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative DNA damage, in the lung DNA of mice given NNK. Gastric cancer, caused by a combination of Helicobacter pylori and salted foods, is lower in tea drinkers. Western nutritionally-linked cancers of the breast, colon, prostate and pancreas can be inhibited by tea. The formation of genotoxic carcinogens for these target organs during the cooking of meats, heterocyclic amines, and their effects were decreased by tea. Tea inhibited the formation of reactive oxygen species and radicals and induced cytochromes P450 1A1, 1A2 and 2B1, and glucuronosyl transferase. The higher formation of glucuronides represents an important mechanism in detoxification. The developmental aspects and growth of cancers through promotion are decreased by tea. The regular use of a widely available, tasty, inexpensive beverage, tea, has displayed valuable preventive properties in chronic human diseases.

Suppression of human pancreatic carcinoma cell growth and invasion by epigallocatechin-3-gallate

INTRODUCTION

The consumption of green tea is associated with a lower risk of several types of human carcinomas. A number of studies have focused on the possible mechanisms of cancer prevention by tea extracts, especially polyphenols such as epigallocatechin-3-gallate (EGCG).

AIMS AND METHODOLOGY

Green tea-derived EGCG was tested in human pancreatic carcinoma cells. The cells (PANC-1, MIA PaCa-2, and BxPC-3) were treated with different doses of EGCG (0, 25, 50, 100, and 200 micromol/L) for 48 hours in culture medium. Proliferation of pancreatic carcinoma cells was measured by means of the WST-1 colorimetric assay. For the study of cell invasion, the cells were incubated with 100 micromol/L EGCG for 2 hours. Then, the cells were added into the cell insert, coated with Matrigel basement membrane matrix. After incubation at 37 degrees C for 24 hours, the cells that had invaded through the Matrigel were counted visually under the microscope.

RESULTS

The growth of all three pancreatic carcinoma cells was significantly suppressed by EGCG treatment in a dose-dependent manner. EGCG treatment caused significant suppression of the invasive ability of pancreatic carcinoma cells PANC-1, MIA PaCa-2, and BxPC-3 but did not affect the cell cycle protein cyclin D1.

CONCLUSION

EGCG may be a potent biologic inhibitor of human pancreatic carcinomas, reducing their proliferative and invasive activities.

Tea flavonoids: bioavailability in vivo and effects on cell signaling pathways in vitro

The elucidation of the potential health benefits of tea beverage continues to be a focus of research in many laboratories. Beneficial effects of tea have been particularly evident in animal tumorigenesis models, with green and black tea frequently demonstrating similar effectivity. Human data are now emerging to support a beneficial role for tea in cardiovascular disease, but the data with respect to cancer risk at various sites remain inconclusive. The constituent flavonoids of green and black tea beverage are known to be potent antioxidants, and although this may be a major factor in explaining their biological activity, it appears that the gallated flavonoids in particular (e.g., epigallocatechin gallate and the gallated theaflavins) impact on a wide range of molecular targets that influence cell growth and more specifically pathways such as those involving angiogenesis. Data on the pharmacokinetic properties of tea flavonoids, primarily on the catechins and therefore related most closely to green tea, have provided indications of the plasma levels and circulating molecular forms that may be expected in humans following tea consumption. The structural complexity of black tea flavonoids, in particular the thearubigins, has hindered efforts to describe their bioavailability and to perform mechanistic studies. Recent studies on the effects of catechins and theaflavins on growth factor-, nuclear factor-kappaB-, and stress-mediated signal transductions are described in this review, where possible in relation to their bioavailability in vivo. These studies indicate that effects that may be relevant to both cancer and atherosclerosis are often observed at tea flavonoid levels that could realistically be encountered in vivo. However, more studies need to be performed using those molecular forms of tea flavonoids (methylated, sulfated, and glucuronidated conjugates) that are the major circulating species encountered following tea consumption. Such studies, combined with further human epidemiological and interventional data, should ultimately elucidate the full beneficial potential of tea beverage on human health.

Mechanisms of inhibition of the Ras-MAP kinase signaling pathway in 30.7b Ras 12 cells by tea polyphenols (-)-epigallocatechin-3-gallate and theaflavin-3,3'-digallate

Our previous study showed that tea polyphenols inhibited MAP kinase and AP-1 activities in mouse epidermal JB6 cells and the corresponding H-ras-transformed cell line 30.7b Ras 12. The present study investigated the mechanisms of this inhibition. The cells were incubated with (-)-epigallocatechin-3-gallate (EGCG) or theaflavin-3,3'-digallate (TFdiG) (20 mM) for different times, and the cell lysate was analyzed by immunoblotting. EGCG treatment decreased the levels of phospho-Erk1/2 and -MEK1/2 time-dependently (by 60% at 60 min). TFdiG lowered their levels by 38%-50% at 15 min. TFdiG effectively decreased total Raf-1 protein levels, most likely through lysosomal degradation. EGCG did not affect protein levels or the activity of Raf-1 significantly but decreased its association with MEK1 as determined by co-immunoprecipitation. In addition, EGCG and TFdiG (10 mM) inhibited the phosphorylation of Elk-1 by isolated phospho-Erk1/2 in vitro. This inhibition of Erk1/2 activity is Elk-1 concentration-dependent and ATP concentration-independent, which suggests that EGCG and TFdiG interfere with the binding of the protein substrate to the kinase. The presently demonstrated specific mechanisms of inhibition of MAP kinases by EGCG and TFdiG may help us to understand the effects of tea consumption on cancer, inflammatory diseases, and cardiovascular diseases.

A review of latest research findings on the health promotion properties of tea

Important progress has been made in the past five years concerning the effects of green and black tea on health. Experimentation with new accurate tools provide useful information about the metabolism of tea components in the body, their mode of action as antioxidants at the cellular level and their protective role in the development of cancer, cardiovascular disease and other pathologies. The use of tea components as nutraceuticals and functional foods are also discussed.

The inhibitory role of DOC-2/DAB2 in growth factor receptor-mediated signal cascade. DOC-2/DAB2-mediated inhibition of ERK phosphorylation via binding to Grb2

DOC-2/DAB2 (differentially expressed in ovarian carcinoma-2/disabled 2) appears to be a potential tumor suppressor gene with a growth inhibitory effect on several cancer types. Previously, we have shown that DOC-2/DAB2 suppresses protein kinase C-induced AP-1 activation, which is modulated by serine 24 phosphorylation in the N terminus of DOC-2/DAB2. However, the functional impact of the C terminus of DOC-2/DAB2, containing three proline-rich domains, has not been explored. In this study, we examined this functional role in modulating signaling mediated by peptide growth factor receptor tyrosine kinase, particularly because it involves the interaction with Grb2. Using sequence-specific peptides, we found that the second proline-rich domain of DOC-2/DAB2 is the key binding site to Grb2 in the presence of growth factors. Such elevated binding interrupts the binding between SOS and Grb2, which consequently suppresses downstream ERK phosphorylation. Reduced ERK phosphorylation was restored when the binding between DOC-2/DAB2 and Grb2 was interrupted by a specific peptide or by increasing the expression of Grb2. Furthermore, the C terminus of the DOC-2/DAB2 construct can inhibit the AP-1 activity elicited by growth factors. We conclude that DOC-2/DAB2, a potent negative regulator, can suppress ERK activation by interrupting the binding between Grb2 and SOS that is elicited by peptide growth factors. This study further illustrates that DOC-2/DAB2 has multiple effects on the RAS-mediated signal cascades active in cancer cells.

Current prospects for controlling cancer growth with non-cytotoxic agents--nutrients, phytochemicals, herbal extracts, and available drugs

In animal or cell culture studies, the growth and spread of cancer can be slowed by many nutrients, food factors, herbal extracts, and well-tolerated, available drugs that are still rarely used in the clinical management of cancer, in part because they seem unlikely to constitute definitive therapies in themselves. However, it is reasonable to expect that mechanistically complementary combinations of these measures could have a worthwhile impact on survival times and, when used as adjuvants, could improve the cure rates achievable with standard therapies. The therapeutic options available in this regard include measures that: down-regulate serum free IGF-I; suppress the synthesis of mevalonic acid and/or certain derivatives thereof; modulate arachidonate metabolism by inhibiting 5-lipoxygenase, 12-lipoxygenase, or COX-2; antagonize the activation of AP-1 transcription factors; promote the activation of PPAR-gamma transcription factors; and that suppress angiogenesis by additional mechanisms. Many of these measures appear suitable for use in cancer prevention.

Molecular regulation of constitutive expression of interleukin-8 in human pancreatic adenocarcinoma

Recent studies have shown that interleukin-8 (IL-8) plays an important role in the growth and metastasis of human pancreatic cancer. In the present study, we determined the molecular regulation of constitutive IL-8 expression in human pancreatic cancer cells. Various human pancreatic cancer cell lines were incubated in vitro. Sixty-seven percent of the cell lines constitutively secreted high levels of IL-8, as determined using enzyme-linked immunosorbent assay. Consistently, these cells constitutively expressed high levels of IL-8 mRNA, as determined using Northern blot analysis. To determine the mechanisms of the high steady-state levels of IL-8 mRNA, the IL-8 half-life and transcription rate were measured. There was no significant difference in IL-8 half-life between cells expressing high and low levels of IL-8. However, higher transcription rates and increased IL-8 promoter activity were observed in the cells constitutively expressing high levels of IL-8. Detailed IL-8 promoter analysis using deletion mutation revealed that the region from -85 to -133 bp was essential for the constitutive IL-8 promoter activity. Also, point-mutation analysis indicated that mutation of NF-kappaB, AP-1, or NF-IL-6 binding sites significantly reduced or eliminated the constitutive IL-8 promoter activity. Consistent with the constitutive IL-8 transcription activity, high levels of constitutive NF-kappaB and AP-1 activity were detected in the cells overexpressing IL-8, as determined using electrophoretic mobility shift assay. In addition, transfection of a dominant-negative I-kappaBalpha expression vector (I-kappaBalphaM) inhibited constitutive NF-kappaB activity and IL-8 expression in pancreatic cancer cells. Collectively, our data demonstrated that constitutive NF-kappaB and AP-1 activation contributes to the overexpression of IL-8, which in turn plays an important role in tumor angiogenesis and contributes to the aggressive biology of human pancreatic cancer.

Rapid effects of stretched myocardial and vascular cells on gene expression of neonatal rat cardiomyocytes with emphasis on autocrine and paracrine mechanisms

Passive stretch of the heart has a direct effect on cardiomyocytes and other cell types including cardiac fibroblasts, endothelial cells, and vascular smooth muscle cells (VSMCs). Cardiomyocytes are targets for the action of peptide growth factors found in myocardium, suggesting an autocrine or paracrine model of the hypertrophic process. In this study we examined stretch-dependent cellular communication between cardiomyocytes, cardiac fibroblasts, endothelial cells, and VSMCs. Stationary cardiomyocytes were incubated with stretch-conditioned medium (CM0-CM60) derived from stretched (for 0-60 min) cardiomyocytes, cardiac fibroblasts, endothelial cells, and VSMCs. The expression levels of protooncogenes (as c-fos, c-jun, and fra-1) were measured, and as an indication of a hypertrophic response the expression of atrial natriuretic peptide (ANP) was measured. Stationary cardiomyocytes that have been incubated for 30 min with CM from stretched (for 0-60 min) cardiomyocytes, cardiac fibroblasts, endothelial cells, and VSMCs showed distinct gene expression patterns that were time-dependent and cell-type specific. In stationary cardiomyocytes, CM derived from stretched cardiomyocytes caused decreased c-fos and fra-1 expression by 37 and 20%, respectively (CM30), elevated c-jun expression by 20% (CM45-CM60), and increased ANP expression by 106% (CM45). CM derived from stretched cardiac fibroblasts caused increased c-fos expression by 41% (CM60), no significant changes in c-jun expression, and increased fra-1 and ANP expression by 39 and 20%, respectively (CM45). CM derived from stretched VSMCs induced an initial decrease in c-fos expression followed by an increase of 13% (CM45) and induced increased c-jun, fra-1, and ANP expression by 39, 24, and 22%, respectively. CM15-CM60 derived from stretched endothelial cells caused decreased c-fos, c-jun and fra-1 expression by 20, 25, and 25%, respectively, and increased ANP expression by 18%. Our data indicate that gene expression of cardiomyocytes in stretched myocardium is regulated by mediators released by cardiomyocytes, cardiac fibroblasts, endothelial cells, and VSMCs. This observation emphasizes the involvement of nonmyocyte cells in the early stages of cardiomyocyte hypertrophy caused by cardiac stretch.

Tumor invasion: role of growth factor-induced cell motility

Cancer progression to the invasive and metastatic stage represents the most formidable barrier to successful treatment. To develop rational therapies, we must determine the molecular bases of these transitions. Cell motility is one of the defining characteristics of invasive tumors, enabling tumors to migrate into adjacent tissues or transmigrate limiting basement membranes and extracellular matrices. Invasive tumor cells have been demonstrated to present dysregulated cell motility in response to extracellular signals from growth factors and cytokines. Recent findings suggest that this growth factor receptor-mediated motility is one of the most common aberrations in tumor cells leading to invasiveness and represents a cellular behavior distinct from-adhesion-related haptokinetic and haptotactic migration. This review focuses on the emerging understanding of the biochemical and biophysical foundations of growth factor-induced cell motility and tumor cell invasiveness, and the implications for development of targeted agents, with particular emphasis on signaling from the epidermal growth factor (EGF) and hepatocyte growth factor (HGF) receptors, as these have most often been associated with tumor invasion. The nascent models highlight the roles of various intracellular signaling pathways including phospholipase C-gamma (PLC gamma), phosphatidylinositol (PI)3'-kinase, mitogen-activated protein (MAP) kinase, and actin cytoskeleton-related events. Development of novel agents against tumor invasion will require not only a detailed appreciation of the biochemical regulatory elements of motility but also a paradigm shift in our approach to and assessment of cancer therapy.

Green tea polyphenols and cancer: biologic mechanisms and practical implications

Polyphenolic compounds in fruits and vegetables have been associated with lower risk of some diseases, including cancer. Recent research has shown that the polyphenolic antioxidants in green tea possess cancer chemopreventive effects. This review discusses the cancer chemopreventive effects associated with green tea and the molecular mechanisms that underlie the broad anticarcinogenic effect of polyphenols in green tea.