Some perspectives on dietary inhibition of carcinogenesis: studies with curcumin and tea

Modulation of CYP1A1 metabolism: From adverse health effects to chemoprevention and therapeutic options

The human cytochrome P450 (CYP) 1A1 gene encodes a monooxygenase that metabolizes multiple exogenous and endogenous substrates. CYP1A1 has become infamous for its oxidative metabolism of benzo[a]pyrene and related polycyclic aromatic hydrocarbons, converting these chemicals into very potent human carcinogens. CYP1A1 expression is mainly controlled by the aryl hydrocarbon receptor (AHR), a transcription factor whose activation is induced by binding of persistent organic pollutants, including polycyclic aromatic hydrocarbons and dioxins. Accordingly, induction of CYP1A1 expression and activity serves as a biomarker of AHR activation and associated xenobiotic metabolism as well as toxicity in diverse animal species and humans. Determination of CYP1A1 activity is integrated into modern toxicological concepts and testing guidelines, emphasizing the tremendous importance of this enzyme for risk assessment and regulation of chemicals. Further, CYP1A1 serves as a molecular target for chemoprevention of chemical carcinogenesis, although present literature is controversial on whether its inhibition or induction exerts beneficial effects. Regarding therapeutic applications, first anti-cancer prodrugs are available, which require a metabolic activation by CYP1A1, and thus enable a specific elimination of CYP1A1-positive tumors. However, the application range of these drugs may be limited due to the frequently observed downregulation of CYP1A1 in various human cancers, probably leading to a reduced metabolism of endogenous AHR ligands and a sustained activation of AHR and associated tumor-promoting responses. We here summarize the current knowledge on CYP1A1 as a key player in the metabolism of exogenous and endogenous substrates and as a promising target molecule for prevention and treatment of human malignancies.

Effect of decaffeinated coffee on function and nucleotide metabolism in kidney

Little is known about the effects of coffee that are not related to the presence of caffeine. The aim of the study was to analyse changes in kidney function and nucleotide metabolism related to high intake of decaffeinated coffee. Mice consumed decaffeinated coffee extract for two weeks. Activities of AMP deaminase, ecto5′-nucleotidase, adenosine deaminase, purine nucleoside phosphorylase were measured in kidney cortex and medulla by analysis of conversion of substrates into products using HPLC. Concentration of nucleotides in kidney cortex, kidney medulla and serum were estimated by HPLC. Activity of ecto5′-nucleotidase increased from 0.032 ± 0.006 to 0.049 ± 0.014 nmol/mg tissue/min in kidney cortex of mice administered high-dose decaffeinated coffee (HDC) together with increase in cortex adenosine concentration and decrease in plasma creatinine concentration. HDC leads to increased activity of ecto5′-nucleotidase in kidney cortex that translates to increase in concentration of adenosine. Surprisingly this caused improved kidney excretion function.

Pharmacokinetic Studies of Chinese Medicinal Herbs Using an Automated Blood Sampling System and Liquid Chromatography-mass Spectrometry

The safety of herbal products is one of the major concerns for the modernization of traditional Chinese medicine, and pharmacokinetic data of medicinal herbs guide us to design the rational use of the herbal formula. This article reviews the advantages of the automated blood sampling (ABS) systems for pharmacokinetic studies. In addition, three commonly used sample preparative methods, protein precipitation, liquid-liquid extraction and solid-phase extraction, are introduced. Furthermore, the definition, causes and evaluation of matrix effects in liquid chromatography-mass spectrometry (LC/MS) analysis are demonstrated. Finally, we present our previous works as practical examples of the application of ABS systems and LC/MS for the pharmacokinetic studies of Chinese medicinal herbs.

Chemopreventive effect of Lagenaria siceraria in two stages DMBA plus croton oil induced skin papillomagenesis

Cancer chemoprevention is a dietary or therapeutic strategy to prevent, suppress, or delay carcinogenesis either at initiation or progression level with nontoxic agents. Use of natural dietary compounds has been a major chemopreventive approach to modulate tumorigenic pathways. In the present study, we have evaluated Lagenaria siceraria (bottle gourd), a common vegetable of Indian household for its chemomodulatory potential. The fruit has been used in traditional medicine for a very long time for health benefits and to cure pain, ulcers, fever, cough, asthma, and other bronchial disorders. However, despite its reported beneficial effect the chemo modulatory potential of this plant has not been reported. Therefore chemopreventive effect of bottle gourd juice (BGJ) was studied against 7,12-dimethylbenz(a)anthracene (DMBA) plus croton oil induced skin papillomagenesis in Swiss albino mice. The effect was studied both at antiinitiation and antiinitiation/promotion level followed by histopathological study. A dose of 2.5% and 5% given in drinking water showed significant decrease in papilloma number, papilloma incidence, papilloma multiplicity, papilloma latency, papilloma volume, and papilloma size in different size range. Histopathological study showed chemopreventive effect by minimizing loss of stratification, a decrease in number of epithelial layers, reducing dermal infiltration and protection for various cytoplasmic changes. Higher dose of BGJ was found to be more effective than lower dose and the chemopreventive effect was maximum for antiinitiation/promotion treatment. Altogether, this study reports the chemopreventive effect of Lagenaria siceraria on skin papillomagenesis for the first time and suggests that its consumption may help in suppression of skin cancer.

Cinnamic acid induces apoptotic cell death and cytoskeleton disruption in human melanoma cells

Anticancer activities of cinnamic acid derivatives include induction of apoptosis by irreversible DNA damage leading to cell death. The present work aimed to compare the cytotoxic and genotoxic potential of cinnamic acid in human melanoma cell line (HT-144) and human melanocyte cell line derived from blue nevus (NGM). Viability assay showed that the IC₅₀ for HT-144 cells was 2.4 mM, while NGM cells were more resistant to the treatment. The growth inhibition was probably associated with DNA damage leading to DNA synthesis inhibition, as shown by BrdU incorporation assay, induction of nuclear aberrations and then apoptosis. The frequency of cell death caused by cinnamic acid was higher in HT-144 cells. Activated-caspase 3 staining showed apoptosis after 24 hours of treatment with cinnamic acid 3.2 mM in HT-144 cells, but not in NGM. We observed microtubules disorganization after cinnamic acid exposure, but this event and cell death seem to be independent according to M30 and tubulin labeling. The frequency of micronucleated HT-144 cells was higher after treatment with cinnamic acid (0.4 and 3.2 mM) when compared to the controls. Cinnamic acid 3.2 mM also increased the frequency of micronucleated NGM cells indicating genotoxic activity of the compound, but the effects were milder. Binucleation and multinucleation counting showed similar results. We conclude that cinnamic acid has effective antiproliferative activity against melanoma cells. However, the increased frequency of micronucleation in NGM cells warrants the possibility of genotoxicity and needs further investigation.

Epigallocatechin-3-gallate decreases UVA-induced HPRT mutations in human skin fibroblasts accompanied by increased rates of senescence and apoptosis

Our study was designed to determine the protective effect of epigallocatechin-3-gallate (EGCG) on cultured human skin fibroblasts (HSFs) from multiple ultraviolet A (UVA) irradiation-induced hypoxanthine-guanine phosphoribosyl transferase (HPRT) mutant colony formation and its underlying mechanisms. In our study, the mutation frequency of the HPRT gene was examined by mutagenesis assay. Cell senescence was determined by histochemical staining of senescence-associated β-galactosidase. The apoptosis rate was detected by flow cytometry. EGCG decreased the UVA-induced HPRT gene mutation frequency by 47.85%. However, EGCG further increased the number of senescent cells by 38.92% and the apoptosis rate by 56.92% in HSFs. The photo-protective effect of EGCG on multiple UVA-exposed HSFs is related to a significant reduction in UVA-induced HPRT mutant cells. This may be caused by the induction of damaged cells to proceed to senescence and apoptosis.

Synthesis and characterization of novel PUFA esters exhibiting potential anticancer activities: an in vitro study

Polyunsaturated fatty acids (PUFAs) have been reported to play a regulatory role in tumour growth progression. In the present study, we have synthesized ester derivatives of two important PUFA viz., linoleic acid (LA) and arachidonic acid (AA) with propofol, a widely used general anaesthetic-sedative agent. The novel propofol ester analogues have been found to inhibit various cancer cell lines in a dose-dependent manner. Moreover, the compounds have been found to induce apoptotic cell death by enhancing the release of cytochrome c and expression of caspase-3. The data of the present study suggest that novel propofol-PUFA esters have strong potential to emerge as effective anticancer agents.

A rapid and simple HPLC method for the determination of curcumin in rat plasma: assay development, validation and application to a pharmacokinetic study of curcumin liposome

This paper describes a sensitive, specific and rapid high-performance liquid chromatography (HPLC) method for the determination of curcumin in rat plasma. After a simple step of protein precipitation in 96-well format using acetonitrile containing the internal standard (IS), emodin, plasma samples were analyzed by reverse-phase HPLC. Curcumin and the IS emodin were separated on a Diamonsil C(18) analytical column (4.6 x 100 mm, 5 microm) using acetonitrile-5% acetic acid (75:25, v/v) as mobile phase at a flow rate of 1.0 mL/min. The method was sensitive with a lower limit of quantitation of 1 ng/mL, with good linearity (r(2) >or= 0.999) over the linear range 1-500 ng/mL. All the validation data, such as accuracy and precision, were within the required limits. A run time of 3.0 min for each sample made high-throughput bioanalysis possible. The assay method was successfully applied to the study of the pharmacokinetics of curcumin liposome in rats.

Mitigation of acute ultraviolet B radiation-mediated damages by baicalin in mouse skin

BACKGROUND

Solar ultraviolet (UV) irradiation, in particular UVB with a wavelength range between 290 and 320 nm, induces different hazardous effects on the skin, including sunburn, photoaging and cancer. Protection against sun-induced damage is therefore a highly desirable goal. Chemoprevention is being investigated as a potential approach for the management of UV damages including skin cancer.

AIM

In this study, to determine the relevance of our in vitro findings to in vivo situations, we assessed the effects of baicalin on UVB-mediated damages in mice skin.

METHODS

Balb/C hairless mice were topically pretreated (24 h before UVB) or post-treated (5 min after UVB) with baicalin (1 mg/cm(2) skin area/mouse/100 microl acetone) and were exposed to UVB 24 h later (180 mJ/cm(2)). The animals were sacrificed 1 and 24 h after the UVB exposure. Skin edema, histopathology changes, hydrogen peroxide (H2O2) and cyclobutane pyrimidine dimers (CPDs)-positive cells were assessed to determine the UVB-induced photodamage.

RESULTS

Our data demonstrated that a topical application of baicalin, either as a pretreatment or as a post-treatment, resulted in a significant decrease in UVB mediated increases in skin edema, skin hyperplasia and infiltration of leukocytes. Further, baicalin treatments (pre and post) also resulted in a significant decrease in UVB mediated (1) generation of H2O2 and (2) formation of DNA photolesions: CPDs.

CONCLUSION

Based on these data, we suggest that baicalin could be developed as an agent for the management of conditions elicited by UV exposure including skin cancer.

Dietary grape seed proanthocyanidins inhibit 12-O-tetradecanoyl phorbol-13-acetate-caused skin tumor promotion in 7,12-dimethylbenz[a]anthracene-initiated mouse skin, which is associated with the inhibition of inflammatory responses

Grape seed proanthocyanidins (GSPs) possess anticarcinogenic activities. Here, we assessed the effects of dietary GSPs on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced skin tumor promotion in 7,12-dimethylbenz[a]anthracene (DMBA)-initiated mouse skin. Administration of dietary GSPs (0.2 and 0.5%, wt/wt) supplemented with control AIN76A diet resulted in significant inhibition of TPA-induced skin tumor promotion in C3H/HeN mice. The mice treated with GSPs developed a significantly lower tumor burden in terms of the percentage of mice with tumors (P < 0.05), total number of tumors per group (P < 0.01, n = 20) and total tumor volume per tumor-bearing mouse (P < 0.01-0.001) as compared with the mice that received the control diet. GSPs also delayed the malignant progression of papillomas into carcinomas. As TPA-induced inflammatory responses are used routinely as markers of skin tumor promotion, we assessed the effect of GSPs on biomarkers of TPA-induced inflammation. Immunohistochemical analysis and western blotting revealed that GSPs significantly inhibited expression of cyclooxygenase-2 (COX-2), prostaglandin E(2) (PGE(2)) and markers of proliferation (proliferating cell nuclear antigen and cyclin D1) in both the DMBA-initiated/TPA-promoted mouse skin and skin tumors. In short-term experiments in which the mouse skin was treated with acute or multiple TPA applications, we found that dietary GSPs inhibited TPA-induced edema, hyperplasia, leukocytes infiltration, myeloperoxidase, COX-2 expression and PGE(2) production in the mouse skin. The inhibitory effect of GSPs was also observed against other structurally different skin tumor promoter-induced inflammation in the skin. Together, our results show that dietary GSPs inhibit chemical carcinogenesis in mouse skin and that the inhibition of skin tumorigenesis by GSPs is associated with the inhibition of inflammatory responses caused by tumor promoters.

Pre- and post-initiation modulating effects of green tea ingestion on rat hepatocarcinogenesis

The purpose of this study was to investigate the effects of green tea ingestion on hepatocarcinogenesis before and after its initiation. Male Sprague-Dawley rats were fed an AIN76A diet with or without green tea. Initiation was induced by a single dose (200 mg/kg) of diethylnitrosamine at week 4 and 0.02% (w/w) 2-acetylaminofluorene was supplied in the diets. The control group had free access to water for 13 weeks (CTR13). Tea infusion was provided from the beginning of the experiment for 13 weeks (PRE13) or from the post-initiation stage until week 13 (POST13). Three other groups (CTR24, PRE24 and POST24) were added to examine the longer-term effects (24 weeks) with the same experimental design. The percentage area of liver sections that were positive for hepatic placental glutathione S-transferase (GST-P), which was used as a marker of preneoplastic lesions, was smaller in PRE13 (20.2 +/- 5.0%, mean +/- SD) and POST13 (26.0 +/- 4.8%) than in CTR13 (33.2 +/- 5.8%, p<0.05). Over the longer period, the GST-P lesions were significantly smaller for both PRE24 and POST24 (21.6 +/- 8.5% and 22.2 +/- 4.0%, respectively) than for CTR24 (28.6 +/- 5.1%, p<0.05), but there was no significant difference between PRE24 and POST24. The liver content of thiobarbituric acid reactive substances was significantly lower in the tea groups than in the controls (p<0.05). However, no significant differences were observed among groups of GST activity. The results show that tea consumption exhibits a stronger short-term initiation-inhibiting ability in liver carcinogenesis, but over a longer period, the preventive effects of green tea ingestion do not differ in post- and pre-initiation.

Effect of genistein on the bioavailability and intestinal cancer chemopreventive activity of (-)-epigallocatechin-3-gallate

The green tea (Camellia sinensis) catechin, (-)-epigallocatechin-3-gallate (EGCG), has shown cancer-preventive activity in animal models. Previously, we have reported the bioavailability of EGCG in rats and mice. Here, we report that cotreatment of HT-29 human colon cancer cells with genistein (from soy) increased cytosolic EGCG by 2- to 5-fold compared with treatment with EGCG only. Inclusion of genistein, at non-cytotoxic concentrations, increased the growth inhibitory effects of EGCG against HT-29 cells (up to 2-fold at 20 microM genistein). Intragastric coadministration of EGCG (75 mg/kg) and genistein (200 mg/kg) to CF-1 mice resulted in an increase in plasma half-life (t(1/2) 148.7 +/- 16.4 versus 111.5 +/- 23.4 min) and exposure (AUC(0-->infinity) 183.9 +/- 20.2 versus 125.8 +/- 26.4 microg/ml x min) of EGCG. Cotreatment with genistein also increased the maximal concentration (C(max)), 6 h exposure (AUC(0-->360 min)), and t(1/2) of EGCG in the small intestine by 2.0-, 4.7- and 1.4-fold, respectively, compared with mice treated with EGCG only. Contrary to our expectations, the combination of 0.01% EGCG in the drinking fluid and 0.2% genistein in the diet enhanced intestinal tumorigenesis in male adenomatous polyposis coli (APC)(min/+) mice. This combination increased the multiplicity of tumors in the medial and distal small intestine: the largest increase was in tumors >2 mm in diameter (4.3-fold compared with controls). This study demonstrates that although genistein can enhance EGCG bioavailability and in vitro growth inhibitory activity, this combination enhances tumorigenesis in the APC(min/+) mouse. These results further show the need for careful cancer prevention studies in animal models and for caution when interpreting data from in vitro studies.

Baicalin protects human fibroblasts against ultraviolet B-induced cyclobutane pyrimidine dimers formation

Exposure to ultraviolet B (UVB) irradiation is a major risk factor for the development of skin cancer. Therefore, it is important to identify agents that can offer protection against UVB-caused DNA damage. Photocarcinogenesis is caused largely by mutations at the sites of incorrectly repaired DNA photoproducts, of which the most common are the cyclobutane pyrimidine dimers (CPDs). In this study, a DNA damage model of UVB irradiation-induced fibroblasts was established. The immunocytochemical staining, immuno dot blotting and Western blotting were employed in the study. We demonstrated that pre-treatment of fibroblasts with Baicalin dose-dependently reduced the amount of UVB-generated CPDs. Compared with UVB irradiated cells, UVB-induced p53 accumulation was less pronounced in Baicalin-treated cells. Taken together, these results suggest that Baicalin prevent CPDs formation induced by UVB. Baicalin is therefore a promising protective substance against UVB radiation.

Putative cancer chemopreventive agents of dietary origin-how safe are they?

As cancer chemopreventive agents are intended for use by healthy individuals as prophylactics to prevent or retard the development of cancer, they must be amenable to ingestion over prolonged periods without toxicity. Therefore, putative chemopreventive agents need to undergo stringent testing to ensure their safety with regard to chronic exposure in humans. The diet is thought to be a source of chemopreventive agents, and dietary compounds are generally considered to be of low hazard, albeit this notion has not often been put to the test. Here the safety information available for 5 dietary putative chemopreventive compounds, indole-3-carbinol (I3C), curcumin, quercetin, epigallocatechin gallate (EGCG), and capsaicin is reviewed. For these agents, normal dietary intake, doses used in clinical trials, efficacious doses in rodents, and where available, toxic doses are compared. For curcumin, quercetin and capsaicin, toxicological data is only available from studies in rodents. Information on long-term effects in animals beyond 28 or 90 days is lacking for EGCG. Capsaicin and quercetin are suspected carcinogens. I3C and quercetin can modulate the absorption of other drugs given concomitantly. Without further investigation of their toxicology, it is difficult to recommend any of these agents for long-term use in the healthy population.

Inhibition of cell cycle progression by hydroxytyrosol is associated with upregulation of cyclin-dependent protein kinase inhibitors p21(WAF1/Cip1) and p27(Kip1) and with induction of differentiation in HL60 cells

Recent evidence indicates that the cancer preventive activity of olive oil can be mediated by the presence of minor components, such as antioxidant phenolic compounds. However, their mechanisms of action remain largely unknown. In this study, we investigated the in vitro effects of one of the main olive oil phenols, hydroxytyrosol [3,4-dihydroxyphenylethanol (3,4-DHPEA)], on proliferation, cell cycle progression, apoptosis, and differentiation of HL60 human promyelocytic leukemia cells. 3,4-DHPEA showed a potent inhibitory activity on DNA synthesis, as evidenced by a 92% reduction of [3H]-thymidine incorporation at 100 micromol/L, and an induced apoptosis, as evidenced by the release of cytosolic nucleosomes and flow cytometry. This phenol, 3,4-DHPEA, was also able to inhibit the progression of the cell cycle in synchronized HL60 cells, which accumulated in the G0/G1 phase of the cell cycle after 25 h of treatment. Furthermore, 3,4-DHPEA induced differentiation on HL60 cells with a maximum effect (22% of cells) at 100 micromol/L after 72 h of treatment. Among the different proteins involved in the regulation of the cell cycle, 3,4-DHPEA reduced the level of cyclin-dependent kinase (CDK) 6 and increased that of cyclin D3. With regard to the CDK inhibitors, p15 was not altered by 3,4-DHPEA treatment, whereas the expression of p21(WAF1/Cip1) and p27(Kip1) was increased at both protein and mRNA levels. To our knowledge, these results provide the first evidence that 3,4-DHPEA may effect the expression of genes involved in the regulation of tumor cell proliferation and differentiation.

Molecular targets of curcumin

Curcumin possesses anti-inflammatory activity and is a potent inhibitor of reactive-oxygen-generating enzymes such as lipoxygenase/cyclooxygenase, xanthine dehydrogenase/oxidase, and inducible nitric oxide synthase (iNOS); it is an effective inducer of heme oxygenase-1. Curcumin is also a potent inhibitor of protein kinase C (PKC), EGF-receptor tyrosine kinase, and IkappaB kinase. Subsequently, curcumin inhibits the activation of NF-KB and the expressions of oncogenes including c-jun, c-fos, c-myc, NIK, MAPKs, ERK, ELK, PI3K, Akt, CDKs, and iNOS. It is considered that PKC, mTOR, and EGFR tyrosine kinase are the major upstream molecular targest for curcumin intervention, whereas the nuclear oncogenes such as c-jun, c-fos, c-myc, CDKs, FAS, and iNOS might act as downstream molecular targets for curcumin actions. It is proposed that curcumin might suppress tumor promotion through blocking signal transduction pathways in the target cells. The oxidant tumor promoter TPA activates PKC by reacting with zinc thiolates present within the regulatory domain, whereas the oxidized form of cancer chemopreventive agent such as curcumin can inactivate PKC by oxidizing the vicinal thiols present within the catalytic domain. Recent studies indicated that proteasome-mediated degradation of cell proteins play a pivotal role in the regulation of several basic cellular processes, including differentiation, proliferation, cell cycling, and apoptosis. It has been demonstrated that curcumin-induced apoptosis is mediated through the impairment of the ubiquitin-proteasome pathway.

CURCUMIN: THE INDIAN SOLID GOLD

Turmeric, derived from the plant Curcuma longa, is a gold-colored spice commonly used in the Indian subcontinent, not only for health care but also for the preservation of food and as a yellow dye for textiles. Curcumin, which gives the yellow color to turmeric, was first isolated almost two centuries ago, and its structure as diferuloylmethane was determined in 1910. Since the time of Ayurveda (1900 Bc) numerous therapeutic activities have been assigned to turmeric for a wide variety of diseases and conditions, including those of the skin, pulmonary, and gastrointestinal systems, aches, pains, wounds, sprains, and liver disorders. Extensive research within the last half century has proven that most of these activities, once associated with turmeric, are due to curcumin. Curcumin has been shown to exhibit antioxidant, anti-inflammatory, antiviral, antibacterial, antifungal, and anticancer activities and thus has a potential against various malignant diseases, diabetes, allergies, arthritis, Alzheimer's disease, and other chronic illnesses. These effects are mediated through the regulation of various transcription factors, growth factors, inflammatory cytokines, protein kinases, and other enzymes. Curcumin exhibits activities similar to recently discovered tumor necrosis factor blockers (e.g., HUMIRA, REMICADE, and ENBREL), a vascular endothelial cell growth factor blocker (e.g., AVASTIN), human epidermal growth factor receptor blockers (e.g., ERBITUX, ERLOTINIB, and GEFTINIB), and a HER2 blocker (e.g., HERCEPTIN). Considering the recent scientific bandwagon that multitargeted therapy is better than monotargeted therapy for most diseases, curcumin can be considered an ideal "Spice for Life".

The effects of tetrahydrocurcumin and green tea polyphenol on the survival of male C57BL/6 mice

The effect of feeding of two different antioxidants, tetrahydrocurcumin (TC) and green tea polyphenols (PPs) on the survival of male C57BL/6 mice was examined. Mice that started to receive diets containing TC (0.2%) at the age of 13 months had significantly longer average life spans (days, mean +/- SD) than control mice (797.6 +/- 151.2 vs.882 +/- 154.6, both n = 50, controls vs. TC treated, plus 11.7%, P < 0.01). The 10% longest survival was also significantly greater in TC-treated mice (plus 6.5%, P < 0.01). In contrast, in mice that started to receive TC in their 19th month of life, no significant difference from the control mice was found for either the average life span or the 10% longest survival. In mice that received water containing PPs (80 mg/l), the average life span was also significantly longer than in the control mice (801 +/- 121.5 vs. 852.7 +/- 88.2, plus 6.4%, P < 0.05), although the 10% longest survival was not significantly different from that in the control mice (P > 0.05). The body weights of the TC (but not PP) fed mice, were slightly (2-4%) but significantly (P < 0.05) lower than the values for the corresponding ages in the control mice in the first six months of treatment. Thereafter, the difference in average body weight between the control and the TC-fed animals was totally lost. Although an additional contribution of an unintended slight decrease in food intake due to TC feeding (suspected due to the difference in body weight) is not excluded, we suggest that the feeding of nutritional antioxidants such as TC and PPs may have the potential to beneficially modify the life spans of animals.

NMR study of the solution structure of curcumin

Curcumin [1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione] is derived from the rhizomes of Curcuma longa. Although early studies concluded that curcumin exists predominantly as a keto-enol tautomer, 1b, in several recent articles the solution structure of curcumin has been represented as a beta-diketone tautomer, 1a. We have investigated the structure of curcumin in solvents ranging in polarity from CDCl3 to mixtures of DMSO-d6 in water, and in buffered aqueous DMSO-d6 solutions with pH values varying from 3 to 9. The solution structure of curcumin was determined on the basis of NMR techniques, including DEPT, HMQC, HMBC, and COSY. The results of the NMR studies show definitely that curcumin exists in solution as keto-enol tautomers, 1b.

Curcumin-induced apoptosis in human leukemia cell HL-60 is associated with inhibition of telomerase activity

Curcumin (diferuloylmethane), a natural cancer chemopreventive compound, has been tested for its action in acute myeloblastic leukemia cell line HL-60. The results clearly show that curcumin induces apoptosis in these cells as evidenced by the release of cytochrome c from mitochondria to the cytosol and increase in the DNA content in sub G1 region as observed in FACS analysis. Apoptosis is apparently mediated by up-regulation of apoptotic gene bax and simultaneous down-regulation of anti-apoptotic gene bcl-2 followed by activation of caspases 3 and 8 and degradation of PARP. Telomerase, a reverse transcriptase, has been found to be activated in more than 80% of human cancers and, therefore, can be considered as a potential marker for tumorigenesis. Certain natural compounds have the potential of inhibiting telomerase activity leading to suppression of cell viability and induction of apoptosis. The present study shows that curcumin-induced apoptosis coincides with the inhibition of telomerase activity in a dose dependent manner.

Up-regulation of CYP26A1 in adenomatous polyposis coli-deficient vertebrates via a WNT-dependent mechanism: implications for intestinal cell differentiation and colon tumor development

Mutations in the adenomatous polyposis coli (APC) tumor suppressor gene seem to underlie the initiation of many colorectal carcinomas. Loss of APC function results in accumulation of beta-catenin and activation of beta-catenin/TCF-dependent transcription. Recent studies have implicated APC in controlling retinoic acid biosynthesis during normal intestinal development through a WNT-independent mechanism. Paradoxically, however, previous studies found that dietary supplementation of Apc(MIN) mice with retinoic acid failed to abrogate adenoma formation. While investigating the above finding, we found that expression of CYP26A1, a major retinoic acid catabolic enzyme, was up-regulated in Apc(MIN) mouse adenomas, human FAP adenomas, human sporadic colon carcinomas, and in the intestine of apc(mcr) mutant zebrafish embryos. Mechanistically, cyp26a1 induction following apc mutation is dependent on WNT signaling as antisense morpholino knockdown of tcf4 or injection of a dnLEF construct into apc(mcr) mutant zebrafish suppressed expression of cyp26a1 along with known WNT target genes. In addition, injection of stabilized beta-catenin or dnGSK3beta into wild-type embryos induced cyp26a1 expression. Genetic knockdown or pharmacologic inhibition of cyp26a1 in apc(mcr) mutant zebrafish embryos rescued gut differentiation defects such as expression of intestinal fatty acid-binding protein and pancreatic trypsin. These findings support a novel role for APC in balancing retinoic acid biosynthesis and catabolism through WNT-independent and WNT-dependent mechanisms.

Suppression of N-nitrosodiethylamine induced hepatocarcinogenesis by silymarin in rats

Antioxidants are one of the key players in tumorigenesis, several natural and synthetic antioxidants were shown to have anticancer effects. In the present investigation the efficacy of silymarin on the antioxidant status of N-nitrosodiethylamine (NDEA) induced hepatocarcinogenesis in Wistar albino male rats were assessed. The animals were divided into five groups. The animals in the groups 1 and 3 were normal control and silymarin control, respectively. Groups 2, 4 and 5 were administered with 0.01% NDEA in drinking water for 15 weeks to induce hepatocellular carcinoma (HCC). Starting 1 week prior to NDEA administration group 4 animals were treated with silymarin in diet for 16 weeks, 10 weeks after NDEA administration group 5 animals were treated with silymarin and continued till the end of the experiment period (16 weeks). After the experimental period the body weight, relative liver weight, number of nodules, size of nodules, the levels of lipid peroxidation, glutathione (GSH), and the activities of antioxidant enzymes were assessed in both haemolysate and liver tissue. In group 2 hepatocellular carcinoma induced animals there was an increase in the number of nodules, relative liver weight. The levels of lipid peroxides were elevated with subsequent decrease in the body weight, (glutathione) GSH, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PD). In contrast, silymarin + NDEA treated groups 4 and 5 animals showed a significant decrease in the number of nodules with concomitant decrease in the lipid peroxidation status. The levels of GSH and the activities of antioxidant enzymes in both haemolysate and liver were improved when compared with hepatocellular carcinoma induced group 2 animals. The electron microscopy studies were also carried out which supports the chemopreventive action of the silymarin against NDEA administration during liver cancer progression. These findings suggest that silymarin suppresses NDEA induced hepatocarcinogenesis by modulating the antioxidant defense status of the animals.

Intakes of selected food groups and beverages and adult acute myeloid leukemia

Few studies have explored the association between diet and adult acute myeloid leukemia (AML). In a hospital-based case-control study among 111 cases and 439 controls, AML risk was negatively associated with milk intake among women (OR 0.25, 95% CI 0.08-0.73) and tea (OR 0.50, 95% CI 0.23-1.09), and positively associated among women with beer (OR 2.48, 95% CI 1.05-5.85), wine (OR 2.32, 95% CI 1.05-5.09), and beef (OR 4.78, 95% CI 1.35-16.94). Our findings support a role of diet in adult AML; however, further research is needed to explore gender differences in risk.

Inhibition of telomerase activity and induction of apoptosis by curcumin in K-562 cells

Telomerase, a reverse transcriptase that maintains telomere length, is highly activated in tumor cells and practically absent in somatic cells and hence considered a potential marker for tumorigenesis. A connection between telomerase activity and resistance to apoptosis has been established. Telomerase, therefore, has been proposed to represent a novel and potentially selective target for cancer therapy. Several synthetic compounds have been developed in recent years with a view to inhibit telomerase activity with telomere shortening below a critical length resulting in apoptosis. Such compounds are always highly toxic. Many plant-derived products act through the induction of apoptosis as a mechanism to suppress carcinogenesis. Curcumin, a phenolic compound isolated from the rhizome of the plant Curcuma longa Linn., has been reported to possess anti-tumor, apoptotic and anti-angiogenic properties. Apoptosis has emerged as the major mechanism by which anti-tumor agents eliminate pre-neoplastic cells or cells progressed to malignancy. The present study was undertaken to examine the mechanism of curcumin-induced apoptosis in human leukemia cell line K-562 with particular emphasis on the role of curcumin on telomerase activity. Induction of apoptosis by curcumin is initiated by the release of cytochrome c from mitochondria into the cytosol, and evidenced by the increase in DNA content in the sub-G1 region as obtained from FACS analysis. Apoptosis is mediated by the activation of caspases 3 and 8, up-regulation of the apoptotic gene bax with concomitant down-regulation of the anti-apoptotic gene bcl-2. Using TRAP assay it has been observed that curcumin inhibits telomerase activity in a dose and time-dependent manner, the inhibition being due to suppression of translocation of telomerase reverse transcriptase (TERT), a catalytic subunit, from cytosol to nucleus. Most significantly, the inhibition of telomerase activity by curcumin correlates with several parameters of apoptosis. The results suggest that telomerase status plays an important role in the induction of apoptosis in K-562 cells by curcumin.

Virgin olive oil phenols inhibit proliferation of human promyelocytic leukemia cells (HL60) by inducing apoptosis and differentiation

Although epidemiologic evidence and animal studies suggest that olive oil may prevent the onset of cancer, the components responsible for such an effect and their mechanisms of action remain largely unknown. In the present study, we investigated the effect of a virgin olive oil phenol extract (PE) on proliferation, the cell cycle distribution profile, apoptosis, and differentiation of the human promyelocytic cell line HL60. PE inhibited HL60 cell proliferation in a time- and concentration-dependent manner, as demonstrated by the viable cell count and 3-[4,5-dimethyl(thiazol-2-yl)]-3,5-diphenyltetrazolium bromide (MTT) metabolism. Cell growth was completely blocked at a PE concentration of 13.5 mg/L; apoptosis was also induced as detected by fluorescence microscopy and flow cytometry. Determination of the cell cycle distribution by flow cytometry revealed an accumulation of cells in the G(0)/G(1) phase. Two compounds isolated from PE, the dialdehydic forms of elenoic acid linked to hydroxytyrosol (3,4-DHPEA-EDA) and to tyrosol (pHPEA-EDA), were shown to possess properties similar to those of PE; they account for a part of the powerful effects exerted by the complex mixture of compounds present in PE. The concentrations of the different compounds in PE were determined by HPLC, and the purity of 3,4-DHPEA-EDA and pHPEA-EDA was ascertained by NMR. Treatment with PE induced a differentiation in HL60 cells, which subsequently acquired the ability to produce superoxide ions and reduce nitroblue tetrazolium to formazan. These results support the hypothesis that polyphenols play a critical role in the anticancer activity of olive oil.

Redox-sensitive transcription factors as prime targets for chemoprevention with anti-inflammatory and antioxidative phytochemicals

Oxidative stress has been implicated in various pathological conditions including cancer. However, the human body has an intrinsic ability to fight against oxidative stress. A wide array of phase 2 detoxifying or antioxidant enzymes constitutes a fundamental cellular defense system against oxidative and electrophilic insults. Transcriptional activation of genes encoding detoxifying and antioxidant enzymes by NF-E2 related factor 2 (Nrf2), a member of the cap'n'collar family of basic leucine zipper transcription factors, may protect cells and tissues from oxidative damage. Many chemopreventive and chemoprotective phytochemicals have been found to enhance cellular antioxidant capacity through activation of this particular transcription factor, thereby blocking initiation of carcinogenesis. A new horizon in chemoprevention research is the recent discovery of molecular links between inflammation and cancer. Components of the cell signaling pathways, especially those that converge on redox-sensitive transcription factors, including nuclear factor-kappaB (NF-kappaB) and activator protein 1 (AP-1) involved in mediating inflammatory response, have been implicated in carcinogenesis. A wide variety of chemopreventive and chemoprotective agents can alter or correct undesired cellular functions caused by abnormal proinflammatory signal transmission mediated by inappropriately activated NF-kappaB and AP-1. The modulation of cellular signaling by anti-inflammatory phytochemicals hence provides a rational and pragmatic strategy for molecular target-based chemoprevention.

Curcumin Suppresses Growth of Head and Neck Squamous Cell Carcinoma

PURPOSE

The purpose of this study was to determine whether curcumin would trigger cell death in the head and neck squamous cell carcinoma (HNSCC) cell lines CCL 23, CAL 27, and UM-SCC1 in a dose-dependent fashion.

EXPERIMENTAL DESIGN

HNSCC cells were treated with curcumin and assayed for in vitro growth suppression using 3-(4,5-dimethylthiozol-2-yl)-2,5-diphenyl tetrazolium bromide and fluorescence-activated cell sorting analyses. Expression of p16, cyclin D1, phospho-Ikappabeta, and nuclear factor-kappabeta (NF-kappabeta) were measured by Western blotting, gel shift, and immunofluorescence.

RESULTS

Addition of curcumin resulted in a dose-dependent growth inhibition of all three cell lines. Curcumin treatment resulted in reduced nuclear expression of NF-kappabeta. This effect on NF-kappabeta was further reflected in the decreased expression of phospho-Ikappabeta-alpha. Whereas the expression of cyclin D1, an NF-kappabeta-activated protein, was also reduced, there was no difference in the expression of p16 at the initial times after curcumin treatment. In vivo growth studies were done using nude mice xenograft tumors. Curcumin was applied as a noninvasive topical paste to the tumors and inhibition of tumor growth was observed in xenografts from the CAL27 cell line.

CONCLUSIONS

Curcumin treatment resulted in suppression of HNSCC growth both in vitro and in vivo. Our data support further investigation into the potential use for curcumin as an adjuvant or chemopreventive agent in head and neck cancer.

Biological properties of curcumin-cellular and molecular mechanisms of action

Curcuminoids, a group of phenolic compounds isolated from the roots of Curcuma longa (Zingiberaceae), exhibit a variety of beneficial effects on health and on events that help in preventing certain diseases. A vast majority of these studies were carried out with curcumin (diferuloyl methane), which is a major curcuminoid. The most detailed studies using curcumin include anti-inflammatory, antioxidant, anticarcinogenic, antiviral, and antiinfectious activities. In addition, the wound healing and detoxifying properties of curcumin have also received considerable attention. As a result of extensive research on the therapeutic properties of curcumin, some understanding on the cellular, molecular, and biochemical mechanism of action of curcumin is emerging. These findings are summarized in this review.

Suppression of protein kinase C and nuclear oncogene expression as possible action mechanisms of cancer chemoprevention by Curcumin

Curcumin (diferuloylmethane) is a major naturally-occurring polyphenol of Curcuma species, which is commonly used as a yellow coloring and flavoring agent in foods. Curcumin has shown anti-carcinogenic activity in animal models. Curcumin possesses anti-inflammatory activity and is a potent inhibitor of reactive oxygen-generating enzymes such as lipoxygenase/cyclooxygenase, xanthine dehydrogenase/oxidase and inducible nitric oxide synthase; and an effective inducer of heme oxygenase-1. Curcumin is also a potent inhibitor of protein kinase C (PKC), EGF(Epidermal growth factor)-receptor tyrosine kinase and IkappaB kinase. Subsequently, curcumin inhibits the activation of NF(nucleor factor)kappaB and the expressions of oncogenes including c-jun, c-fos, c-myc, NIK, MAPKs, ERK, ELK, PI3K, Akt, CDKs and iNOS. It is proposed that curcumin may suppress tumor promotion through blocking signal transduction pathways in the target cells. The oxidant tumor promoter TPA activates PKC by reacting with zinc thiolates present within the regulatory domain, while the oxidized form of cancer chemopreventive agent such as curcumin can inactivate PKC by oxidizing the vicinal thiols present within the catalytic domain. Recent studies indicated that proteasome-mediated degradation of cell proteins play a pivotal role in the regulation of several basic cellular processes including differentiation, proliferation, cell cycling, and apoptosis. It has been demonstrated that curcumin-induced apoptosis is mediated through the impairment of ubiquitin-proteasome pathway. Curcumin was first biotransformed to dihydrocurcumin and tetrahydrocurcumin and that these compounds subsequently were converted to monoglucuronide conjugates. These results suggest that curcumin-glucuronide, dihydrocurcumin-glucuronide, tetrahydrocurcumin-glucuronide and tetrahydrocurcumin are the major metabolites of curcumin in mice, rats and humans.

Amelioration of immune cell number depletion and potentiation of depressed detoxification system of tumor-bearing mice by curcumin

BACKGROUND

The true therapeutic benefit of the use of natural products, especially acceptable dietary components such as curcumin, which can spare the normal cells and boost host immunity, has opened new horizons in cancer prevention and treatment.

METHODS

In our model system we used Ehrlich's ascites carcinoma cells grown in peritoneal carity of Swiss albino mice and curcumin was fed every alternative day.

RESULTS

Here, we report that curcumin administration to tumor-bearing mice decreased tumor cell number significantly in a dose-dependent manner. Furthermore, tumor-induced depletion of immune cell number of the host, as was evidenced from the decrease in bone marrow progenitor as well as thymic and splenic mononuclear cell numbers, was reintrated by curcumin. In fact, curcumin inhibited tumor-induced apoptosis of both thymocytes and splenocytes thereby restoring immune cell numbers to normal level in treated Ehrlich's ascites carcinoma-bearing mice. Moreover, curcumin was not toxic to the host; rather in tumor-bearing mice it inhibited hematopoietic toxicity, acted as a hepatoprotective agent and activated depressed anti-oxidant and detoxification systems.

CONCLUSION

The ability of curcumin to regress tumor as well as to protect the host from tumor-induced immunosuppression and toxicity strongly supports the candidacy of curcumin as a potential agent for the dietary therapy of cancer.

Signal transduction network leading to COX-2 Induction: a road map in search of cancer chemopreventives

Cancer is still a major global health concern even after an everlasting strive in conquering this dread disease. Emphasis is now given to chemoprevention to reduce the risk of cancer and also to improve the quality of life among cancer afflicted individuals. Recent progress in molecular biology of cancer has identified key components of the cellular signaling network, whose functional abnormality results in undesired alterations in cellular homeostasis, creating a cellular microenvironment that favors premalignant and malignant transformation. Multiple lines of evidence suggest an elevated expression of cyclooxygenase-2 (COX-2) is causally linked to cancer. In response to oxidative/pro-inflammatory stimuli, turning on unusual signaling arrays mediated through diverse classes of kinases and transcription factors results in aberrant expression of COX-2. Population-based as well as laboratory studies have explored a broad spectrum of chemopreventive agents including selective COX-2 inhibitors and a wide variety of anti-inflammatory phytochemicals, which have been shown to target cellular signaling molecules as underlying mechanisms of chemoprevention. Thus, unraveling signaling pathways regulating aberrant COX-2 expression and targeted blocking of one or more components of those signal cascades may be exploited in searching chemopreventive agents in the future.

Environmental and chemical carcinogenesis

People are continuously exposed exogenously to varying amounts of chemicals that have been shown to have carcinogenic or mutagenic properties in experimental systems. Exposure can occur exogenously when these agents are present in food, air or water, and also endogenously when they are products of metabolism or pathophysiologic states such as inflammation. It has been estimated that exposure to environmental chemical carcinogens may contribute significantly to the causation of a sizable fraction, perhaps a majority, of human cancers, when exposures are related to "life-style" factors such as diet, tobacco use, etc. This chapter summarizes several aspects of environmental chemical carcinogenesis that have been extensively studied and illustrates the power of mechanistic investigation combined with molecular epidemiologic approaches in establishing causative linkages between environmental exposures and increased cancer risks. A causative relationship between exposure to aflatoxin, a strongly carcinogenic mold-produced contaminant of dietary staples in Asia and Africa, and elevated risk for primary liver cancer has been demonstrated through the application of well-validated biomarkers in molecular epidemiology. These studies have also identified a striking synergistic interaction between aflatoxin and hepatitis B virus infection in elevating liver cancer risk. Use of tobacco products provides a clear example of cancer causation by a life-style factor involving carcinogen exposure. Tobacco carcinogens and their DNA adducts are central to cancer induction by tobacco products, and the contribution of specific tobacco carcinogens (e.g. PAH and NNK) to tobacco-induced lung cancer, can be evaluated by a weight of evidence approach. Factors considered include presence in tobacco products, carcinogenicity in laboratory animals, human uptake, metabolism and adduct formation, possible role in causing molecular changes in oncogenes or suppressor genes, and other relevant data. This approach can be applied to evaluation of other environmental carcinogens, and the evaluations would be markedly facilitated by prospective epidemiologic studies incorporating phenotypic carcinogen-specific biomarkers. Heterocyclic amines represent an important class of carcinogens in foods. They are mutagens and carcinogens at numerous organ sites in experimental animals, are produced when meats are heated above 180 degrees C for long periods. Four of these compounds can consistently be identified in well-done meat products from the North American diet, and although a causal linkage has not been established, a majority of epidemiology studies have linked consumption of well-done meat products to cancer of the colon, breast and stomach. Studies employing molecular biomarkers suggest that individuals may differ in their susceptibility to these carcinogens, and genetic polymorphisms may contribute to this variability. Heterocyclic amines, like most other chemical carcinogens, are not carcinogenic per se but must be metabolized by a family of cytochrome P450 enzymes to chemically reactive electrophiles prior to reacting with DNA to initiate a carcinogenic response. These same cytochrome P450 enzymes--as well as enzymes that act on the metabolic products of the cytochromes P450 (e.g. glucuronyl transferase, glutathione S-transferase and others)--also metabolize chemicals by inactivation pathways, and the relative amounts of activation and detoxification will determine whether a chemical is carcinogenic. Because both genetic and environmental factors influence the levels of enzymes that metabolically activate and detoxify chemicals, they can also influence carcinogenic risk. Many of the phenotypes of cancer cells can be the result of mutations, i.e., changes in the nucleotide sequence of DNA that accumulate as tumors progress. These can arise as a result of DNA damage or by the incorporation of non-complementary nucleotides during DNA synthetic processes. Based upon the disparity between the infrequency of spontaneous mutations and the large numbers of mutations reported in human tumors, it has been postulated that cancers must exhibit a mutator phenotype, which would represent an early event in cancer progression. A mutator phenotype could be generated by mutations in genes that normally function to guarantee genetic stability. These mutations presumably arise via DNA damage by environmental or endogenous agents, but it remains to be determined whether the acquisition of a mutator phenotype is a necessary event during tumor progression.

Lupeol modulates NF-kappaB and PI3K/Akt pathways and inhibits skin cancer in CD-1 mice

Chemoprevention has become an effective cancer control modality; however, the search for novel agent(s) for the armamentarium of cancer chemoprevention continues. We argue that agents capable for inhibition of promotion stage of tumorigenesis with the ability to intervene at several critical pathways in the tumorigenesis process will have greater advantage over other single-target agents. Lupeol, a triterpene, is the principal constituent of common fruit plants such as olive, mango, fig and medicinal herbs that have been used to treat skin aliments. Lupeol has been reported to possess a wide range of medicinal properties that include strong antioxidant, antimutagenic, anti-inflammatory and antiarthritic effects. In the present study, we show that Lupeol possesses antitumor-promoting effects in a mouse skin tumorigenesis model. We first determined the effect of topical application of Lupeol to CD-1 mouse against 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-induced conventional markers and other novel markers of skin tumor promotion. We found that topical application of Lupeol (1-2 mg/mouse) 30 min prior to TPA (3.2 nmol/mouse) application onto the skin of CD-1 mice afforded significant inhibition, in a time- and dose-dependent manner, against TPA-mediated increase in (i) skin edema and hyperplasia, (ii) epidermal ornithine decarboxylase (ODC) activity, and (iii) protein expression of ODC, cyclo-oxygenase-2 and nitric oxide synthase. As of the role of nuclear factor kappa B (NF-kappaB) and phosphatidyl inositol 3-kinase (PI3K)/Akt signaling in tumor promotion, we next determined the effect of topical application of Lupeol to mouse skin against these signaling pathways. We found that Lupeol treatment to mouse skin resulted in the inhibition of TPA-induced (i) activation of PI3K, (ii) phosphorylation of Akt at Thr(308), (iii) activation of NF-kappaB and IKKalpha, and (iv) degradation and phosphorylation of IkappaBalpha. The animals pretreated with Lupeol showed significantly reduced tumor incidence, lower tumor body burden and a significant delay in the latency period for tumor appearance. At the termination of the experiment at 28 weeks, 100% of the animals in TPA-treated group exhibited seven to eight tumors/mouse, whereas only 53% of the mice receiving Lupeol prior to TPA treatment exhibited one to three tumors/mouse. These results for the first time provide evidence that Lupeol possesses antiskin tumor-promoting effects in CD-1 mouse and inhibits conventional as well as novel biomarkers of tumor promotion. We suggest that Lupeol is an attractive antitumor-promoting agent that must be evaluated in tumor models other than skin carcinogenesis.

Immunomodulatory activity of curcumin: suppression of lymphocyte proliferation, development of cell-mediated cytotoxicity, and cytokine production in vitro

Curcumin (diferuloylmethane), a major curcumanoid found in the spice turmeric, exhibits anti-inflammatory, anti-oxidant, and chemopreventive activities. However, the effect of curcumin on the development of T cell-mediated immunological responses largely remains unknown. In this study we have investigated the effect of curcumin on mitogen/antigen induced proliferation of splenic lymphocytes, induction of cytotoxic T lymphocytes (CTLs), lymphokine activated killer (LAK) cells, and the production of cytokines by T lymphocytes and macrophages. We found that mitogen, interleukin-2 (IL-2) or alloantigen induced proliferation of splenic lymphocytes, and development of cytotoxic T lymphocytes is significantly suppressed at 12.5-30 micromol/L curcumin. The generation of LAK cells at similar concentrations was less sensitive to the suppressive effect of curcumin compared to the generation of antigen specific CTLs. Curcumin irreversibly impaired the production of these immune functions, since lymphoid cells failed to respond to the activation signals following 8h pretreatment with curcumin. Curcumin also inhibited the expression/production of IL-2 and interferon-gamma (IFN-gamma) by splenic T lymphocytes and IL-12 and tumor necrosis factor-alpha (TNF-alpha) by peritoneal macrophages irreversibly. Curcumin inhibited the activation of the transcription factor nuclear factor kappaB (NF-kappaB) without affecting the levels of constitutively expressed NF-kappaB. The latter result suggests that curcumin most likely inhibits cell proliferation, cell-mediated cytotoxicity (CMC), and cytokine production by inhibiting NF-kappaB target genes involved in induction of these immune responses.

Differentiation-Promoting Activity of Pomegranate (Punica granatum) Fruit Extracts in HL-60 Human Promyelocytic Leukemia Cells

Differentiation refers to the ability of cancer cells to revert to their normal counterparts, and its induction represents an important noncytotoxic therapy for leukemia, and also breast, prostate, and other solid malignancies. Flavonoids are a group of differentiation-inducing chemicals with a potentially lower toxicology profile than retinoids. Flavonoid-rich polyphenol fractions from the pomegranate (Punica granatum) fruit exert anti-proliferative, anti-invasive, anti-eicosanoid, and pro-apoptotic actions in breast and prostate cancer cells and anti-angiogenic activities in vitro and in vivo. Here we tested flavonoid-rich fractions from fresh (J) and fermented (W) pomegranate juice and from an aqueous extraction of pomegranate pericarps (P) as potential differentiation-promoting agents of human HL-60 promyelocytic leukemia cells. Four assays were used to assess differentiation: nitro blue tetrazolium reducing activity, nonspecific esterase activity, specific esterase activity, and phagocytic activity. In addition, the effect of these extracts on HL-60 proliferation was evaluated. Extracts W and P were strong promoters of differentiation in all settings, with extract J showing only a relatively mild differentiation-promoting effect. The extracts had proportional inhibitory effects on HL-60 cell proliferation. The results highlight an important, previously unknown, mechanism of the cancer preventive and suppressive potential of pomegranate fermented juice and pericarp extracts.

Nutritional and botanical modulation of the inflammatory cascade--eicosanoids, cyclooxygenases, and lipoxygenases--as an adjunct in cancer therapy

Emerging on the horizon in cancer therapy is an expansion of the scope of treatment beyond cytotoxic approaches to include molecular management of cancer physiopathology. The goal in these integrative approaches, which extends beyond eradicating the affected cells, is to control the cancer phenotype. One key new approach appears to be modulation of the inflammatory cascade, as research is expanding that links cancer initiation, promotion, progression, angiogenesis, and metastasis to inflammatory events. This article presents a literature review of the emerging relationship between neoplasia and inflammatory eicosanoids (PGE2 and related prostaglandins), with a focus on how inhibition of their synthesizing oxidases, particularly cyclooxygenase (COX), offers anticancer actions in vitro and in vivo. Although a majority of this research emphasizes the pharmaceutical applications of nonsteroidal anti-inflammatory drugs and selective COX-2 inhibitors, these agents fail to address alternate pathways available for the synthesis of proinflammatory eicosanoids. Evidence is presented that suggests the inhibition of lipoxygenase and its by-products-LTB4, 5-HETE, and 12-HETE-represents an overlooked but crucial component in complementary cancer therapies. Based on the hypothesis that natural agents capable of modulating both lipoxygenase and COX may advance the efficacy of cancer therapy, an overview and discussion is presented of dietary modifications and selected nutritional and botanical agents (notably, omega-3 fatty acids, antioxidants, boswellia, bromelain, curcumin, and quercetin) that favorably influence eicosanoid production.

Anthocyanin- and hydrolyzable tannin-rich pomegranate fruit extract modulates MAPK and NF-?B pathways and inhibits skin tumorigenesis in CD-1 mice

Chemoprevention has come of age as an effective cancer control modality; however, the search for novel agent(s) for the armamentarium of cancer chemoprevention continues. We argue that agents capable of intervening at more than one critical pathway in the carcinogenesis process will have greater advantage over other single-target agents. Pomegranate fruit extract (PFE) derived from the tree Punica granatum possesses strong antioxidant and antiinflammatory properties. Pomegranate fruit was extracted with acetone and analyzed based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and found to contain anthocyanins, ellagitannins and hydrolyzable tannins. We evaluated whether PFE possesses antitumor-promoting effects. We first determined the effect of topical application of PFE to CD-1 mice against 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced conventional markers and other novel markers of skin tumor promotion. We found that topical application of PFE (2 mg/mouse) 30 min prior to TPA (3.2 nmole/mouse) application on mouse skin afforded significant inhibition, in a time-dependent manner, against TPA-mediated increase in skin edema and hyperplasia, epidermal ornithine decarboxylase (ODC) activity and protein expression of ODC and cyclooxygenase-2. We also found that topical application of PFE resulted in inhibition of TPA-induced phosphorylation of ERK1/2, p38 and JNK1/2, as well as activation of NF-kappaB and IKKalpha and phosphorylation and degradation of IkappaBalpha. We next assessed the effect of skin application of PFE on TPA-induced skin tumor promotion in 7,12-dimethylbenz(a)anthracene-initiated CD-1 mouse. The animals pretreated with PFE showed substantially reduced tumor incidence and lower tumor body burden when assessed as total number of tumors per group, percent of mice with tumors and number of tumors per animal as compared to animals that did not receive PFE. In TPA-treated group, 100% of the mice developed tumors at 16 weeks on test, whereas at this time in PFE-treated group, only 30% mice exhibited tumors. Skin application of PFE prior to TPA application also resulted in a significant delay in latency period from 9 to 14 weeks and afforded protection when tumor data were considered in terms of tumor incidence and tumor multiplicity. The results of our study provide clear evidence that PFE possesses antiskin-tumor-promoting effects in CD-1 mouse. Because PFE is capable of inhibiting conventional as well as novel biomarkers of TPA-induced tumor promotion, it may possess chemopreventive activity in a wide range of tumor models. Thus, an in-depth study to define active agent(s) in PFE capable of affording antitumor-promoting effect is warranted.

Tailoring cancer chemoprevention regimens to the individual

The present article, which is a tribute to the memory of Dr. Edward Bresnick, emphasizes the importance of environmental and life-style factors for cancer causation in the human population and points out approaches to cancer prevention. These approaches include vaccinations for the prevention of cancers that are caused by infectious agents as well as the use of cancer chemopreventive agents. The use of tamoxifen and letrozole to prevent breast cancer, finasteride to prevent prostate cancer, sunscreens or topical applications of 5-fluorouracil to prevent sunlight-induced skin cancer, and aspirin or calcium to prevent colon cancer are a few examples of cancer chemoprevention in high risk individuals and in the general population. An underdeveloped area of cancer chemoprevention is the use of combinations of agents that work by different mechanisms. It was pointed out that animal studies indicate that many cancer chemopreventive agents inhibit carcinogenesis under one set of experimental conditions but enhance carcinogenesis under another set of experimental conditions. These observations suggest that tailoring the chemopreventive regimen to the individual or to groups of individuals living under different environmental conditions or with different mechanisms of carcinogenesis may be an important aspect of cancer chemoprevention in human populations. How to tailor cancer chemoprevention regimens to the individual is an important challenge for the future.

Arachidonic acid cascade inhibitors modulate phorbol ester-induced oxidative stress in female ICR mouse skin: differential roles of 5-lipoxygenase and cyclooxygenase-2 in leukocyte infiltration and activation

We recently developed a short-term assay for skin H2O2 generation induced by double 12-O-tetradecanoylphorbol-13-acetate (TPA) applications for mechanistic study on skin epidermal carcinogenesis. In the present study, we investigated the individual roles of arachidonic acid metabolism in H2O2 generation in mouse skin inflammation. The experiments using inhibitors of arachidonic acid (AA) metabolism showed that corticosteroid and a lipoxygenase (LO) inhibitor expectedly suppressed double TPA application-induced H2O2 generation through the interference of chemotactic action but not by direct decomposition or scavenging. We also demonstrated that the treatment of AA (1 mumol) and 5-LO metabolites including leukotriene B4 (LTB4) partly mimicked, though soybean LO-derived lipid hydroperoxide and prostaglandins did not, the priming effect evaluated by edema formation and leukocyte infiltration. We also confirmed that inflammatory leukocytes accumulated by LTB4 generated a significant amount of H2O2 by TPA stimulation. These results suggested that 5-LO metabolites of AA are the potential key molecules in the TPA-induced priming event. Interestingly, the cyclooxygenase (COX-) 2-selective inhibitor nimesulide (NS) and celecoxib (CXB) showed different responses than those of other inhibitors. These agents showed no specific potential to inhibit the priming event but significantly suppressed H2O2 generation, lipid peroxidation, and hyperplasia in mouse skin. From the results based on an in vitro leukocyte differentiation model, we speculated that the antioxidant effect of the COX-2 inhibitors might be partly associated with both counteraction of proinflammatory cytokine-enhanced ROS generation and inhibition of CD11b, an important molecule for cell adhesion, expression. Indeed, the topical application of NS attenuated the number of infiltrated leukocytes induced by TPA in mouse skin. Thus, these gathered data indicated the differential roles of 5-LO and COX-2 in leukocyte adhesion, infiltration, and H2O2 generation.

Effects of dietary antioxidants and 2-amino-3-methylimidazo[4,5-f]- quinoline (IQ) on preneoplastic lesions and on oxidative damage, hormonal status, and detoxification capacity in the rat

The potential beneficial or adverse affect of prolonged dietary administration of moderate to high doses (1-100 mg/kg diet) of the antioxidants, lycopene, quercetin and resveratrol or a mixture of lycopene and quercetin was investigated in male F344 rats. Selected markers for toxicity and defense mechanisms were assayed in blood, liver and colon and the impact of the antioxidant administrations on putative preneoplastic changes in liver and colon was assessed. The dietary carcinogen, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) (200 mg/kg diet) served as a pro-oxidant, genotoxicity and general toxicity control. IQ increased the levels of protein and DNA oxidation products in plasma, the area of glutathione S-transferase-placental form positive (GST-P) foci in the liver as well as the number of colonic aberrant crypt foci (ACF). All antioxidants and the antioxidant combination significantly increased the level of lymphocytic DNA damage, to an extent comparable with the effect induced by IQ. In contrast to the control group where no GST-P foci were detected, GST-P foci were detected in animals exposed to quercetin, lycopene and the combination of the two. However, the increase in the volume of GST-P foci did not reach statistical significance. The present results indicate that moderate to high doses of common dietary antioxidants can damage lymphocyte DNA and induce low levels of preneoplastic liver lesions in experimental animals. Long-term exposure to moderate to high doses of antioxidants may thus via pro-oxidative mechanisms and non-oxidative mechanisms modulate carcinogenesis.

Dietary feeding of proanthocyanidins from grape seeds prevents photocarcinogenesis in SKH-1 hairless mice: relationship to decreased fat and lipid peroxidation

The use of dietary botanicals is receiving considerable interest in the protection of skin from the adverse biological effects of solar ultraviolet (UV) radiation. Dietary feeding of proanthocyanidins extracted from grape seeds (GSP) (0.2 and 0.5%, w/w) in AIN76 control diet to SKH-1 hairless mice resulted in prevention of photocarcinogenesis in terms of tumor incidence (20-95%), tumor multiplicity (46-95%) and tumor size (29-94%) against UVB-induced complete (both initiation + promotion), initiation and promotion stages of photocarcinogenesis. Feeding of GSP (0.5%, w/w) also resulted in prevention of malignant transformation of UVB-induced papillomas to carcinomas in terms of carcinoma incidence (45%), carcinoma multiplicity (61%) and carcinoma size (75%) compared with non-GSP treated mice following UVB-induced complete carcinogenesis protocol at the end of 30 weeks. Biochemical analysis revealed that treatment of GSP in vivo and in vitro systems significantly inhibited UVB- or Fe3+-induced lipid peroxidation by 57-66% (P<0.01) and 41-77% (P< 0.05-0.001), respectively, thus suggesting the antioxidant mechanism of photoprotection by GSP. Long-term feeding of GSP did not show apparent signs of toxicity in mice when determined in terms of body weight, diet consumption and physical characteristics of internal body organs like spleen, liver and kidney. Feeding of GSP also did not show apparent signs of toxicity when determined in terms of total body mass (mass of lean + fat), total bone mineral density and total bone mineral content by employing dual-energy X-ray absorptiometry (DXA). DXA analysis also revealed that feeding of GSP significantly decreased tissue fat level (24-27%, P<0.05) without changing the total body mass of the animals compared with non-GSP-fed animals. This can be attributed to increased lipolysis or decreased synthesis of fat due to administration of GSP. Together, it can be suggested that inhibition of photocarcinogenesis by GSP treatment may be associated with the reduction in UVB-induced oxidative damage and tissue fat content.

The effects of coffee on enzymes involved in metabolism of the dietary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in rats

The effects of coffee on the metabolism and genotoxicity of the dietary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were investigated. Coffee diminished the bacterial mutagenicity of PhIP in the Ames reversion assay through inhibition of cytochrome P450 1A2 (CYP1A2), a key enzyme involved in the metabolic activation of PhIP. When given as part of the diet (0, 1 or 5% w/w) to male Fischer-344 rats for 2 weeks, coffee affected the expression of hepatic enzymes involved in PhIP metabolism. Coffee increased the expression of CYP1A2 by 16-fold in the 5% coffee-treated group, and approximately half of this inductive effect was attributed to caffeine. Coffee also increased the expression of enzymes involved in the detoxication of PhIP. A 2-fold increase in expression of glutathione S-transferase alpha was observed, UDP-glucuronosyl transferase (UGTs) activities of p-nitrophenol increased 2-fold, while N(2)-and N3-glucuronidation of the genotoxic metabolite 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (HONH-PhIP) increased by 1.3-fold in the 5% coffee-treated over the control group. The amount of PhIP (0.75 mg/kg, 24 h) eliminated in urine as the N(2)-and N3-glucuronide conjugates of HONH-PhIP increased by 1.8- and 2.5-fold, respectively, in the 5% coffee-treated group over control rats, suggesting either increased rates of N-oxidation of PhIP or N-glucuronidation of HONH-PhIP. Despite the strong induction of CYP1A2, there was no increase in PhIP-DNA adduct formation in colon and pancreas while liver adducts decreased by 50% over control animals. These data suggest that the effect of coffee on inhibition of PhIP N-oxidation and ensuing DNA damage is more important in vivo than its effect on induction of PhIP N-hydroxylation.

4-Hydroxy-3-methoxybenzoic acid methyl ester: a curcumin derivative targets Akt/NF kappa B cell survival signaling pathway: potential for prostate cancer management

Transcription factor NFkappaB and the serine/threonine kinase Akt play critical roles in mammalian cell survival signaling and have been shown to be activated in various malignancies including prostate cancer (PCA). We have developed an analogue of curcumin called 4-hydroxy-3-methoxybenzoic acid methyl ester (HMBME) that targets the Akt/NFkappaB signaling pathway. Here, we demonstrate the ability of this novel compound to inhibit the proliferation of human and mouse PCA cells. HMBME-induced apoptosis in these cells was tested by using multiple biochemical approaches, in addition to morphologic analysis. Overexpression of constitutively active Akt reversed the HMBME-induced growth inhibition and apoptosis, illustrating the direct role of Akt signaling in HMBME-mediated growth inhibition and apoptosis. Further, investigation of the molecular events associated with its action in LNCaP cells shows that: 1) HMBME reduces the level of activated form of Akt (phosphorylated Akt); and 2) inhibits the Akt kinase activity. Further, the transcriptional activity of NFkappaB, the DNA-binding activity of NFkappaB, and levels of p65 were all significantly reduced following treatment with HMBME. Overexpression of constitutively active Akt, but not the kinase dead mutant of Akt, activated the basal NFkappaB transcriptional activity. HMBME treatment had no influence on this constitutively active Akt-augmented NFkappaB transcriptional activity. These data indicate that HMBME-mediated inhibition of Akt kinase activity may have a potential in suppressing/decreasing the activity of major survival/antiapoptotic pathways. The potential use of HMBME as an agent that targets survival mechanisms in PCA cells is discussed.