Development and validation of a LC method for determination of genistein in topical nanoemulsions

The aim of this study was to develop and validate an isocratic LC method for the quantification of genistein in topical nanoemulsions. The analyses were performed at room temperature on a reversed-phase C18 column using a mobile phase composed of methanol/water/acetonitrile (70:25:5, w/w/w) at 1.0 ml x min(-1). The detection was carried out on a UV detector at 327 nm. The linearity, in the range of 25-75 microg/ml, presented a determination coefficient (r2) higher than 0.999, calculated by the least square method. No interferences from the excipients (egg-lecithin, octyldodecanol or medium chain triglycerides) were detected. The R.S.D. values for intra- and inter-day precision experiments were lower than 2.3%. The recovery of genistein from nanoemulsions ranged from 96.6% to 106.6%. The excellent performance of the method, its linearity, accuracy and precision, demonstrate that it can be readily used to quantify genistein incorporated in nanoemulsions.

Pomegranate derived products for cancer chemoprevention

Because treatment options for advanced metastasized cancers remain inadequate, developing effective approaches for the prevention of cancer has become an important goal to reduce cancer burden. One such strategy is through chemoprevention, preferably by the use of non-toxic dietary substances and botanical products. Pomegranate, used for centuries for its medicinal properties is now being recognized as a potential chemopreventive and anticancer agent. Increasing body of evidence has underscored the cancer preventive efficacy of pomegranate both in vitro and in vivo animal models. The emerging data provide new insights into the molecular framework needed to establish novel mechanism-based chemopreventive strategies for various human cancers.

Inhibition of tumorigenesis in ApcMin/+ mice by a combination of (-)-epigallocatechin-3-gallate and fish oil

The effect of a combination of (-)-epigallocatechin-3-gallate (EGCG) with fish oil on intestinal tumorigenesis in Apc (Min/+) mice fed a high-fat diet was investigated in the present study. The combined treatment of EGCG and fish oil for 9 weeks reduced the tumor number by 53% as compared to controls while neither agent alone had a significant effect. Apoptosis was significantly increased in all treatment groups. beta-Catenin nuclear positivity in adenomas from the combination group was lower than control mice, implicating the modulation of Wnt signaling by the combination. Fish oil and the combination significantly reduced prostaglandin E 2 (PGE 2) levels in small intestinal tumors as compared to controls, suggesting modulation of aberrant arachidonic acid metabolism by fish oil. Akt phosphorylation in adenomas was significantly reduced in all treatment groups, which may have contributed to the observed increase in apoptosis. The results indicate that a combination of low doses of EGCG and fish oil can inhibit tumor multiplicity in Apc (Min/+) mice.

Antioxidant action of Andrographis paniculata on lymphoma

Regulation of the balance between production of reactive oxygen species (ROS) by cellular processes and its removal by antioxidant defense system maintains normal physiological processes. Any condition leading to increased ROS results in oxidative stress which has been related with a number of diseases including cancer. Improvement in antioxidant defense system is required to overcome the damaging effects of oxidative stress. Therefore in the present study, effect of the aqueous extract of a medicinal plant Andrographis paniculata (AP) on antioxidant defense system in liver is investigated in lymphoma bearing AKR mice. Estimating catalase, superoxide dismutase and glutathione S transferase monitored the antioxidant action. Oral administration of the aqueous extract of A. paniculata in different doses causes a significant elevation of catalase, superoxide dismutase and glutathione S transferase activities. It reveals the antioxidant action of the aqueous extract of AP, which may play a role in the anticarcinogenic activity by reducing the oxidative stress. LDH activity is known to increase in various cancers due to hypoxic condition. Lactate dehydrogenase is used as tumor marker. We find a significant decrease in LDH activity on treatment with AP, which indicates a decrease in carcinogenic activity. A comparison with Doxorubicin (DOX), an anticancerous drug, indicates that the aqueous extract of AP is more effective than DOX with respect to its effect on catalase, superoxide dismutase, glutathione S transferase as well as on lactate dehydrogenase activities in liver of lymphoma bearing mice.

Chemoprevention of Carcinogenic Progression to Esophageal Adenocarcinoma by the Manganese Superoxide Dismutase Supplementation

PURPOSE

Oxidative stress is related to the carcinogenic pathway of reflux esophagitis to Barrett's metaplasia to esophageal adenocarcinoma (EAC). Recent studies have shown that a decreased manganese superoxide dismutase (MnSOD) level is associated with the increased incidences of Barrett's esophagus (BE) and EAC. The aim of this study was to investigate MnSOD supplementation as a chemopreventive agent to prevent oxidative injury and subsequent BE and EAC formation.

EXPERIMENTAL DESIGN

Our esophagoduodenal anastomotic (EDA) model was done on rats according to our established procedure and treated with Mn(III)tetrakis(4-benzoic acid) porphyrin (MnTBAP; 10 mg/kg, i.p. every 3 days). Histologic changes were determined after the EDA model at 1, 3, and 6 months. Lipid peroxidation and 8-hydroxy-deoxyguanosine for DNA oxidative damage were determined by thiobarbituric acid-reactive substance assay and immunohistochemical staining. Enzymatic activities of MnSOD and Cu/ZnSOD were evaluated, and the rate of proliferation was determined by proliferating cell nuclear antigen staining.

RESULTS

Severe esophagitis was seen in 100% of the EDA rats, and morphologic transformation within the esophageal epithelium was observed with intestinal metaplasia (40% of animals) and cancer (40% of animals) identified after 3 months. Decreased oxidative damage, along with the decreased degree of esophagitis and incidence of BE (20%) and EAC (0%), was found in MnTBAP-treated EDA rats comparing with the saline-treated EDA control. Decreased proliferation (46%) and increased SOD enzymatic activities (25%) were also found in the EDA rats treated with MnTBAP.

CONCLUSION

MnTBAP protected rat esophageal epithelium from oxidative injury induced by EDA, and it could prevent the transformation of esophageal epithelial cell to BE to EAC by preservation of antioxidants.

Elemental Selenium at Nano Size (Nano-Se) as a Potential Chemopreventive Agent with Reduced Risk of Selenium Toxicity: Comparison with Se-Methylselenocysteine in Mice

Selenium (Se) is an essential trace element with a narrow margin between beneficial and toxic effects. As a promising chemopreventive agent, its use requires consumption over the long term, so the toxicity of Se is always a crucial concern. Based on clinical findings and recent studies in selenoprotein gene-modified mice, it is likely that the antioxidant function of one or more selenoproteins is responsible for the chemopreventive effect of Se. Furthermore, upregulation of phase 2 enzymes by Se has been implicated as a possible chemopreventive mechanism at supranutritional dietary levels. Se-methylselenocysteine (SeMSC), a naturally occurring organic Se product, is considered as one of the most effective chemopreventive selenocompounds. The present study revealed that, as compared with SeMSC, elemental Se at nano size (Nano-Se) possessed equal efficacy in increasing the activities of glutathione peroxidase, thioredoxin reductase, and glutathione S-transferase, but had much lower toxicity as indicated by median lethal dose, acute liver injury, survival rate, and short-term toxicity. Our results suggest that Nano-Se can serve as a potential chemopreventive agent with reduced risk of Se toxicity.

Urinary excretion of total isothiocyanates from cruciferous vegetables shows high dose-response relationship and may be a useful biomarker for isothiocyanate exposure

BACKGROUND

Isothiocyanates (ITCs), hydrolysis products from glucosinolates, are a family of biologically active compounds originating from cruciferous vegetables. Many ITCs are assumed to have cancer preventive effects and to further evaluate these potential health effects, reliable biomarkers of ITC exposure are needed.

AIM OF THE STUDY

In this study we investigated the ability of urinary ITC excretion to reflect a low or high daily intake of cruciferous vegetables.

METHODS

The design was a controlled human crossover study (n = 6). Subjects consumed a self-restricted glucosinolate-free diet 48 h before the study-day where a basic diet supplemented with 80 or 350 g of mixed cruciferous vegetables was consumed. All urine was collected in intervals during the 48 h period after ingestion of the cruciferous vegetables. Total ITC in the cruciferous mixture and total ITC and their metabolites in urine was quantified as the cyclocondensation product of 1,2-bezenedithiol by high performance liquid chromatography.

RESULTS

The total urinary excretion of ITCs correlated significantly with the two doses of ITC from diets with high or low cruciferous content (r (s )= 0.90, P < 0.01). The fraction of urinary ITC excreted was 69.02 +/- 11.57% and 74.53 +/- 8.39% of the amounts ingested for 80 and 350 g cruciferous vegetables, respectively.

CONCLUSION

The results in this study indicate that the urinary excretion of ITCs, measured by use of the cyclocondesation reaction, is a useful and precise tool that may be used as a biomarker of ITC exposure in population based studies.

Berry anthocyanins as novel antioxidants in human health and disease prevention

Edible berries, a potential source of natural anthocyanin antioxidants, have demonstrated a broad spectrum of biomedical functions. These include cardiovascular disorders, advancing age-induced oxidative stress, inflammatory responses, and diverse degenerative diseases. Berry anthocyanins also improve neuronal and cognitive brain functions, ocular health as well as protect genomic DNA integrity. This chapter demonstrates the beneficial effects of wild blueberry, bilberry, cranberry, elderberry, raspberry seeds, and strawberry in human health and disease prevention. Furthermore, this chapter will discuss the pharmacological benefits of a novel combination of selected berry extracts known as OptiBerry, a combination of wild blueberry, wild bilberry, cranberry, elderberry, raspberry seeds, and strawberry, and its potential benefit over individual berries. Recent studies in our laboratories have demonstrated that OptiBerry exhibits high antioxidant efficacy as shown by its high oxygen radical absorbance capacity (ORAC) values, novel antiangiogenic and antiatherosclerotic activities, and potential cytotoxicity towards Helicobacter pylori, a noxious pathogen responsible for various gastrointestinal disorders including duodenal ulcer and gastric cancer, as compared to individual berry extracts. OptiBerry also significantly inhibited basal MCP-1 and inducible NF-kappabeta transcriptions as well as the inflammatory biomarker IL-8, and significantly reduced the ability to form hemangioma and markedly decreased EOMA cell-induced tumor growth in an in vivo model. Overall, berry anthocyanins trigger genetic signaling in promoting human health and disease prevention.

Chemopreventive effects of orange peel extract (OPE). II: OPE inhibits atypical hyperplastic lesions in rodent mammary gland

Cancer chemoprevention via the ingestion of natural substances is a current topic of considerable interest. Flavonoids are a family of biologically active phytochemicals having a variety of biological effects. Orange peel extract (OPE) is an abundant source of polymethoxyflavones (PMFs) with potential chemopreventive properties. The OPE used here was a mixture containing tangeretin (19.0%), heptamethoxyflavone (15.24%), tetramethoxyflavone (13.6%), nobiletin (12.49%), hexamethoxyflavone (11.06%), and sinensitin (9.16%). C57Bl/6 mice were fed a new "Western-style" diet (NWD), which had previously induced atypical hyperplasias in mammary gland, and NWD supplemented with a standardized OPE containing 30% PMFs. Mice were fed one of four diets: (1) AIN-76A diet (control); (2) NWD; 0.25% OPE in NWD; or (4) 0.5% OPE in NWD. After 3 months of feeding, atypical hyperplasias developed in mammary glands of mice fed NWD, but not in controls. After feeding OPE in NWD, atypical hyperplasias per mouse decreased in frequency compared to feeding NWD alone (P < .05 in mice fed 0.25% OPE). Apoptosis increased in OPE-treated groups (P < .01) with no inhibition of mitosis. Thus, a standardized preparation of OPE with 30% PMFs decreased development of an atypical hyperplastic lesion and increased apoptosis in ductal epithelial cells of mouse mammary gland.

Chemopreventive effects of orange peel extract (OPE). I: OPE inhibits intestinal tumor growth in ApcMin/+ mice

Orange peel is a rich source of flavonoids with polymethoxyflavones as major constituents, compounds associated with potential antioxidant, anti-inflammatory, and antitumor activities. We studied the effect of an orange peel extract (OPE) on intestinal tumor growth in Apc(Min/+) mice, a mouse model for human familial adenomatous polyposis (FAP). The OPE contained 30% polymethoxyflavones, a mixture that included tangeretin (19.0%), heptamethoxyflavone (15.24%), tetramethoxyflavone (13.6%), nobiletin (12.49%), hexamethoxyflavone (11.06%), and sinensitin (9.16%). Apc(Min/+) mice were fed one of four diets: (1) AIN-76A control diet; (2) a new Western-style diet (NWD), i.e., AIN-76A diet modified with decreased calcium, vitamin D, and methyl-donor nutrients and increased lipid content); (3) NWD with 0.25% OPE; and (4) NWD with 0.5% OPE, with all additives premixed in the diet. After 9 weeks of feeding NWD to the Apc(Min/+) mice, tumors increased mainly in the colon, with tumor multiplicity increasing 5.3-fold and tumor volume increasing 6.7-fold. After feeding 0.5% OPE in NWD, the development of tumors markedly decreased, with multiplicity decreasing 49% in the small intestine and 38% in the colon. NWD also led to increased apoptosis in intestinal tumors, and 0.5% OPE in NWD further increased apoptosis in tumors of the small and large intestine. Findings indicated that OPE inhibited tumorigenesis in this preclinical mouse model of FAP, and increased apoptosis may have contributed to this effect.

Thiols and the chemoprevention of cancer

Thiols such as glutathione interfere with the complex carcinogenic process. Under stress conditions, they scavenge harmful molecules: Glutathione conjugation of electrophilic carcinogens may prevent tumor initiation, and reduced thiols may defend against oxidative stress. Thus, associated chemopreventive strategies involve enhancement of antioxidant or conjugating capacity by increasing the levels of, particularly, glutathione through precursor application or synthesis stimulation and by inducing the corresponding enzymes. The antioxidant potential of thiols is, however, a part of a more general capacity to regulate redox status even in the absence of unequivocal stress conditions. Redox status controls the activities of various cellular signalling proteins through oxidation or reduction of particular sensor structures that are also mostly thiols. The development of feasible chemotherapeutic strategies on the basis of this complex system of redox-sensitive messenger proteins is a goal in ongoing and future research.

Potential of diallyl sulfide bearing pH-sensitive liposomes in chemoprevention against DMBA-induced skin papilloma

Diallyl sulfide (DAS), an active component of garlic, possesses strong anti-neoplastic properties against various forms of cancer. In the present study, we have evaluated chemo-preventive effects of liposomized DAS (conventional egg PC and pH-sensitive liposomes) against DMBA-induced skin papilloma. Various liposome-based novel formulations of DAS (250 microg/mouse) were applied topically, after one hour of exposure to DMBA (52 microg/mouse/dose), to the animals. The animals were treated thrice weekly for the total period of 12 weeks. The efficacy of the various liposomal formulations of DAS was evaluated on the basis of parameters such as incidence of tumorogenesis and total numbers and sizes of induced tumor nodules. The liposomized DAS formulations also were assessed for their effect on the expression of p53wt, p53mut, and p21/Waf1. The results of the present study showed that liposomized DAS could effectively delay the onset of tumorogenesis and reduce the cumulative numbers and sizes of tumor papillomas in treated mice. Treatment of DMBA-exposed animals with the liposomal formulation of DAS ensued in upregulation of p53wt and p21/Waf1, while levels of p53mut expression reduced down. The promising chemo-preventive nature of liposomal DAS may form the basis for establishing effective means of controlling various forms of cancer, including skin papilloma.

Inhibition of carcinogenesis by tea constituents

The possible cancer preventive activity of tea has received much attention in recent years. The inhibitory activities of tea and tea constituents against carcinogenesis at different organ sites have been demonstrated in many animal models. The effect of tea consumption on human cancers, however, remains inconclusive. The mechanisms of action of tea polyphenols, especially EGCG, the most abundant and active catechin, have been extensively investigated. Most of the studies, however, were based on cell culture systems, and these mechanisms need to be evaluated and verified in animal models or humans in order to gain more understanding on the effect of tea consumption on human cancer. Human intervention trials are warranted to determine the possible prevention of cancer of specific sites by preparation of tea constituents.

Intake of specific carotenoids and the risk of epithelial ovarian cancer

There has been considerable interest in the role of carotenoids in the chemoprevention of cancer. However, few studies have examined the association between intake of specific carotenoids and the risk of epithelial ovarian cancer and the results for carotenoids have been inconclusive. To investigate whether the intake of α-carotene, β-carotene, β-cryptoxanthin, lutein and zeaxanthin, and lycopene is inversely associated with ovarian cancer risk, a case–control study was conducted in China during 1999–2000. The cases were 254 patients with histologically confirmed epithelial ovarian cancer and 652 age-matched controls were randomly recruited during the same period. Habitual dietary intake and lifestyle were collected by face-to-face interview using a validated and reliable FFQ. The US Department of Agriculture nutrient composition database was used to calculate the intake of specific carotenoids. Unconditional logistic regression analyses were used to estimate OR and 95 % CI, accounting for age, locality, education, BMI, smoking, tea drinking, parity, oral contraceptive use, hormone replacement therapy, menopausal status, family history of ovarian cancer, physical activity and energy intake. Compared with the highest v. the lowest quartile of intake, the adjusted OR were 0·39 (95 % CI 0·23, 0·66) for α-carotene, 0·51 (95 % CI 0·31, 0·84) for β-carotene, 0·51 (95 % CI 0·31, 0·83) for β-cryptoxanthin, 0·45 (0·27, 0·76) for lutein and zeaxanthin, and 0·33 (95 % CI 0·20, 0·56) for total carotenoids, with statistically significant tests for trend. It is concluded that a higher intake of carotenoids can reduce the risk of epithelial ovarian cancer.

Lycopene from heat-induced cis-isomer-rich tomato sauce is more bioavailable than from all-trans-rich tomato sauce in human subjects

Lycopene is present mainly as cis-isomers in human serum and tissues whereas all-trans-lycopene predominates in tomato products, suggesting that all-trans-lycopene is isomerised in the body or is less bioavailable. The objectives of the present study were to develop processing conditions for tomatoes to obtain products with different cis-trans-lycopene isomer distribution and to assess their bioavailability. Healthy adult subjects (n 12) were recruited for this randomised cross-over trial. Each intervention was preceded by a 2-week washout period. Two tomato sauces, one rich in all-trans-lycopene (32·5 mg total lycopene/100 g sauce; 5 % cis-isomers), the other high in cis-lycopene (26·4 mg total lycopene/100 g sauce; 45 % cis-isomers), were produced by different heat-processing techniques. Each sauce (150 g) was served in a standardised meal at 08.00 hours after overnight fasting. Plasma TAG-rich lipoprotein fractions over 9.5 h following test-meal consumption as a measure of lycopene absorption were obtained and expressed as baseline-corrected area under the concentration v. time curves (AUC), using HPLC-electrochemical detection. AUC values adjusted for the amount lycopene consumed showed that total, total cis-, and all-trans-lycopene responses were significantly higher from the cis-isomer-rich sauce, compared with the all-trans-rich sauce, being 7·30 (sem 1·45) v. 4·74 (sem 1·08) nmol × h/l (P = 0·002), 3·80 (sem 0·76) v. 1·98 (sem 0·37) nmol × h/l (P = 0·0005) and 3·50 (sem 0·76) v. 2·76 (sem 0·76) nmol × h/l (P = 0·01), respectively. The present study demonstrates significant lycopene bioavailability from cis-lycopene-rich tomato sauce and highlights the importance of considering isomer-distribution for lycopene bioavailability. Furthermore, processing parameters can be controlled to alter isomer patterns of tomato products and influence lycopene bioavailability.

Chemopreventive effect of aerosolized polyphenon E on lung tumorigenesis in A/J mice

Effective chemoprevention of lung cancer in high-risk patients through the administration of pharmacologic or nutritional agents is urgently needed. Aerosol inhalation can deliver chemopreventive agents directly to the respiratory tract to inhibit the tumorigenic process. In this study, polyphenon E (PolyE) and (-)-epigallocatechin-3-gallate (EGCG) were administered by aerosol delivery to A/J mice beginning 2 weeks after carcinogen treatment and continuing daily by inhalation throughout the remainder of the study (20 weeks). PolyE decreased tumor load by approximately 59%. However, EGCG, both at the same dose and at a higher dose, failed to inhibit lung carcinogenesis. These results indicate that aerosol delivery of PolyE, but not EGCG, may be a useful chemopreventive protocol in subjects at high risk for lung cancer.

Anticarcinogenic activity of selenium-enriched green tea extracts in vivo

Both selenium and green tea have been shown to have potential antitumor effects. Here we have investigated the anticarcinogenic effect of the selenium-enriched green tea extract (Se-TE) in a Kunming mice model transplanted with human hepatoma cells HepG2. Mice were assigned to 8 groups consisting of 10 mice each after tumor cell inoculation. The control group received only water, whereas the remaining groups received regular green tea extract (RT), Se-TE which was produced by fertilization with selenite on tea leaves, selenite, and RT + selenite. After the mice were fed intragastrically with these agents for 8 days, tumor growth in RT-, Se-TE-, and selenite-fed mice was significantly suppressed, compared with that in control mice (P < 0.001). Supplementation with Se-TEs and selenite was able to elevate mice blood and liver Se concentrations, but did not significantly enhance selenoprotein glutathione peroxidase and other antioxidant enzyme superoxide dismutase activity in mice blood and liver. These results suggest that the antitumor function of Se-TEs may be attributed to the oxidative stress induced by selenium and green tea components in a suitable selenium supplementation pathway.

Redox molecules and cancer prevention: the importance of understanding the role of the antioxidant network

Cancer has a complex etiology with multiple risk factors that involve the interplay between genetic and environmental influences. There is compelling evidence that dietary plant foods appear to be protective against certain type of cancers. Among a number of mechanistic hypotheses, diet-derived antioxidants have been proposed to contribute to explain these findings. However, contrasting results from intervention trials have raised strong concerns about the influence of antioxidants on human health. A vulnerable point of the research on antioxidants is the lack of information on the effect of the whole array of dietary antioxidants in cancer prevention because so far mainly single molecules have been investigated. Total antioxidant capacity (TAC) considers the single antioxidant activity as well as the synergistic interactions of the redox molecules present in complex matrixes, giving an insight into the assessment of the non-enzymatic antioxidant network. This article will outline the state of art of the research on TAC and cancer, describing the plasma non-enzymatic antioxidant network and its association with diet. The feasibility of TAC assessment as an innovative tool for investigating the association between dietary antioxidants, oxidative stress, and cancer will be also discussed.

Nutrient intake and risk of squamous cell carcinoma of the esophagus: a case-control study in Uruguay

In 1996-2004 a case-control study on nutrient intake, dietary constituents and risk of squamous cell carcinoma of the esophagus was conducted in Montevideo, Uruguay. In fact, Uruguay, and especially its northern provinces, which border Brazil, are high-risk areas. The study included 234 cases and 936 controls. The controls were hospitalized patients with non-neoplastic disease, which was not related to tobacco smoking and alcohol drinking, and without recent changes in their diets. Controls were frequency matched to cases on age (10-yr intervals), sex, and residence (Montevideo and other provinces). Dietary constituents were energy adjusted using the residuals method and then categorized in quartiles according to the distribution of the controls. The final model included linoleic acid, lycopene, alpha-carotene, beta-cryptoxanthin, vitamin A, monounsaturated fat, total carbohydrates, beta-carotene, and folate. The odds ratio (OR) for high intake of linoleic acid was 1.4 (95% confidence interval, CI = 1.2-1.6), whereas lycopene displayed a strong protective effect (OR = 0.7; 95% CI = 0.6-0.9). The possible role of these and other dietary constituents in esophageal carcinogenesis is discussed.

The green tea polyphenol, epigallocatechin-3-gallate inhibits telomerase and induces apoptosis in drug-resistant lung cancer cells

Epidemiological studies on humans and investigations in animal models suggest that consumption of green tea has anti-cancer effects. Small-cell lung carcinoma (SCLC) has a poor prognosis, particularly due to the development of drug resistance. We investigated the effects of the green tea polyphenol, epigallocatechin-3-gallate (EGCG) on human SCLC cells. EGCG had similar effects (IC(50) of approximately 70 microM) on drug-sensitive (H69) and drug-resistant (H69VP) SCLC cells, indicating that it is not part of the drug resistance phenotype expressed in these cells. In both cell lines, incubation in EGCG at 1 x IC(50) for 24h resulted in 50-60% reduced telomerase activity as measured by a PCR-based assay for telomeric repeats. Colorimetric assays of cells treated for 36 h with EGCG demonstrated a reduction in activities of caspases 3 (50%) and 9 (70%) but not caspase 8, indicating initiation of apoptosis. DNA fragmentation as measured by ELISA occurred within cells treated with EGCG and this was confirmed by TUNEL staining. Flow cytometric analysis of SCLC cells incubated for 36 h in EGCG indicated a cell-cycle block in S phase. These data indicate the potential use of EGCG, and possibly green tea, in treating SCLC.

Hepatoprotective effects of lupeol and mango pulp extract of carcinogen induced alteration in Swiss albino mice

Lupeol, a triterpene present in mango and other fruits, is known to exhibit a number of pharmacological properties including antioxidant, antilithiatic, and antidiabetic effects. In the present study, chemopreventive properties of lupeol and mango pulp extract (MPE) were evaluated against 7,12-dimethylbenz(a)anthracene (DMBA) induced alteration in liver of Swiss albino mice. Lupeol (25 mg/kg body weight, bw) or 1 mL of 20% w/v aqueous MPE/mouse were daily given once for 1 wk after a single dose of DMBA (50 mg/kg bw). Lupeol/MPE supplementation effectively influenced the DMBA induced oxidative stress, characterized by restored antioxidant enzyme activities and decrease in lipid peroxidation. A reduction of apoptotic cell population in the hypodiploid region was observed in lupeol and MPE supplemented animals. The inhibition of apoptosis was preceded by decrease in reactive oxygen species (ROS) level and restoration of mitochondrial transmembrane potential followed by decreased DNA fragmentation. In DMBA treated animals, downregulation of antiapoptotic Bcl-2 and upregulation of proapoptotic Bax and Caspase 3 in mouse liver was observed. These alterations were restored by lupeol/MPE, indicating inhibition of apoptosis. Thus, lupeol/MPE was found to be effective in combating oxidative stress induced cellular injury of mouse liver by modulating cell-growth regulators.

A Randomized Trial of Lycopene Supplementation in Tobago Men with High Prostate Cancer Risk

This unblinded, randomized, Phase I clinical trial was conducted to determine whether lycopene supplementation lowered serum prostate specific antigen (PSA), surrogate endpoint for prostate cancer initiation or progression, in men with elevated prostate cancer risk. Afro-Caribbean men (n=81) with high-grade prostatic intraepithelial neoplasia, atypical foci or repeated non-cancerous biopsies, ascertained in a population-based screening program, were randomized to four months intervention with 30 mg/day lycopene (Lyc-O-Mato) plus a multivitamin, or to multivitamin, only. Serum PSA and lycopene were compared at randomization, 1, and 4 mo using two-sided chi2 and t-tests for independent samples. Treatment groups were similar at baseline. Serum lycopene levels approximately doubled in the lycopene intervention group. Serum PSA declined during the first month of treatment, but returned to randomization level by month 4. The PSA response was nearly identical in both treatment groups. No adverse effects attributed to lycopene supplementation were documented. We conclude that the PSA lowering response to antioxidant supplementation observed in previous 3-wk studies in men awaiting prostatectomy may have been a transient response, perhaps not specific to lycopene. Lowering of serum PSA may not be an appropriate endpoint for the long-term studies needed to evaluate lycopene supplementation for reducing prostate cancer initiation or progression.

Cranberry and blueberry: Evidence for protective effects against cancer and vascular diseases

Growing evidence from tissue culture, animal, and clinical models suggests that the flavonoid-rich fruits of the North American cranberry and blueberry (Vaccinium spp.) have the potential ability to limit the development and severity of certain cancers and vascular diseases including atherosclerosis, ischemic stroke, and neurodegenerative diseases of aging. The fruits contain a variety of phytochemicals that could contribute to these protective effects, including flavonoids such as anthocyanins, flavonols, and proanthocyanidins; substituted cinnamic acids and stilbenes; and triterpenoids such as ursolic acid and its esters. Cranberry and blueberry constituents are likely to act by mechanisms that counteract oxidative stress, decrease inflammation, and modulate macromolecular interactions and expression of genes associated with disease processes. The evidence suggests a potential role for dietary cranberry and blueberry in the prevention of cancer and vascular diseases, justifying further research to determine how the bioavailability and metabolism of berry phytonutrients influence their activity in vivo.

Whole-food sources of vitamin A more effectively inhibit female rat sexual maturation, mammary gland development, and mammary carcinogenesis than retinyl palmitate

Previous work using an adolescent rat model for breast cancer showed increased tumor occurrence in rats fed a chemopreventive dose of vitamin A. Preclinical models for nutrient-cancer interactions utilizing defined diets do not replicate the complexity of the human diet and may be inadequate to investigate food patterns associated with reduced cancer risk in humans. To evaluate this concept, the effects of vitamin A on sexual maturation, mammary gland development, and sensitivity to carcinogenesis were determined in the context of a human food-based diet (whole food diet). At 20 d of age (p20), female rats received either a whole-food diet with adequate levels of vitamin A, a diet with a 5.5-fold increase in vitamin A from fruits and vegetables (S diet), or a diet with a 6.2-fold increase in vitamin A provided as retinyl palmitate (RP diet). To determine the effect of dietary intervention on pubertal mammary gland development, the dietary intervention period was restricted to postnatal d 21-63. Rats were injected with 50 mg 1-methyl-1-nitrosourea/kg body weight at d 66. Compared with adolescent rats that consumed the Ad diet, consumption of S and RP diets reduced mammary cancer multiplicity (relative risk approximately 0.7, P < or = 0.002), which was associated with a reduction in alveolar gland development. The S diet suppressed the onset of sexual maturation (P < 0.001) and inhibited markers of mammary alveologenesis more than the RP diet. These data demonstrate that the amount and source of vitamin A consumed by adolescent female rats can influence the onset of puberty, mammary gland alveolar development, and breast cancer risk and highlight the relevance of utilizing whole-food diets to evaluate the role of dietary factors in cancer prevention.

Berry phytochemicals, genomic stability and cancer: Evidence for chemoprotection at several stages in the carcinogenic process

Consumption of a diet high in plant-based foods is associated with a decreased risk of epithelial cell cancers at several sites. Cytoprotectants in fruits and vegetables include vitamins, minerals and numerous micronutrients. While there is little evidence uniquely linking berry consumption with lower cancer risk, berries contain high levels of compounds believed to reduce malignant transformation, including the polyphenol flavonoids and anthocyanins. There is strong and convincing evidence that berry extracts and berry phytochemicals modulate biomarkers of DNA damage and indicators of malignant transformation in vitro and in vivo. Data from numerous cell culture and animal models indicate that berry components such as the anthocyanins are potent anticarcinogenic agents and are protective against genomic instability at several sites in the carcinogenic pathway. Anticarcinogenic mechanisms include modulation of carcinogen activation and detoxification, decreased DNA binding of the carcinogen, inhibition of oxidative DNA damage, alteration in cell signalling and malignant transformation and inhibition of cell invasiveness and metastasis. Exactly which berry constituents are cytoprotective remains uncertain and in the majority of in vitro and in vivo studies the concentration of extract or phytochemical employed is non-nutritional. Evidence for an anticarcinogenic effect in human studies is weak.

Chemopreventive potential of zinc in experimentally induced colon carcinogenesis

The present study was performed to evaluate the efficacy of zinc treatment on colonic antioxidant defense system and histoarchitecture in 1,2-dimethylhydrazine- (DMH) induced colon carcinogenesis in male Sprague-Dawley rats. The rats were segregated into four groups viz., normal control, DMH treated, zinc treated, DMH+zinc treated. Colon carcinogenesis was induced through weekly subcutaneous injections of DMH (30 mg/kg body weight) for 16 weeks. Zinc (in the form of zinc sulphate) was supplemented to rats at a dose level of 227 mg/L in drinking water, ad libitum for the entire duration of the study. Increased tumor incidence, tumor size and number of aberrant crypt foci (ACF) were accompanied by a decrease in lipid peroxidation, glutathione-S-transferase, superoxide dismutase (SOD) and catalase. On the contrary, significantly increased levels of reduced glutathione (GSH) and glutathione reductase (GR) were observed in DMH treated rats. Administration of zinc to DMH treated rats significantly decreased the tumor incidence, tumor size and aberrant crypt foci number with simultaneous enhancement of lipid peroxidation, SOD, catalase and glutathione-S-transferase. Further, the levels of GSH and GR were also decreased following zinc supplementation to DMH treated rats. Well-differentiated signs of dysplasia were evident in colonic tissue sections by DMH administration alone. However, zinc treatment to DMH treated rats greatly restored normalcy in the colonic histoarchitecture, with no apparent signs of neoplasia. EDXRF studies revealed a significant decrease in tissue concentrations of zinc in the colon following DMH treatment, which upon zinc supplementation were recovered to near normal levels. In conclusion, the results of this study suggest that zinc has a positive beneficial effect against chemically induced colonic preneoplastic progression in rats induced by DMH.

Intake of fruits and vegetables and polymorphisms in DNA repair genes in bladder cancer

The objective is to investigate the relationships between fruit and vegetable intake, DNA repair gene polymorphisms and the risk of bladder cancer. We have analyzed a hospital-based case-control study of 266 individuals with incident, histologically confirmed bladder cancer diagnosed between 1994 and 2003. Controls (n = 193) were patients treated for benign diseases recruited daily in a random fashion from the same hospital as the cases. All cases and controls were interviewed face-to-face for major risk factors, along fruit and vegetable consumption. Odds ratios (ORs) for fruit and vegetable intake and DNA repair gene polymorphisms were adjusted for age and smoking status, using unconditional logistic regression. A statistically significant decreased risk was observed for fruit and vegetable intake above median (versus below the median) [unadjusted OR 0.61, confidence interval (CI) 95% 0.50-0.96 and OR 0.54, CI 95% 0.39-0.80, respectively]; the decreased risk persisted after adjustment for age and cigarette smoking (OR 0.73, CI 95% 0.49-1.01 and OR 0.86, CI 95% 0.56-1.08, respectively). The fruits and vegetables associated with decreased risks included leafy green vegetables, cruciferous vegetables, apples and citrus fruits. We did not find any interactions between DNA repair gene polymorphisms and fruit and vegetable intake. This study found a reduced risk associated with fruit and vegetable intake. No interaction was observed between fruit and vegetable consumption and DNA repair gene polymorphisms.

Chemopreventive characteristics of avocado fruit

Phytochemicals are recognized as playing an important role in cancer prevention by fruits and vegetables. The avocado is a widely grown and consumed fruit that is high in nutrients and low in calories, sodium, and fats. Studies have shown that phytochemicals extracted from the avocado fruit selectively induce cell cycle arrest, inhibit growth, and induce apoptosis in precancerous and cancer cell lines. Our recent studies indicate that phytochemicals extracted with chloroform from avocado fruits target multiple signaling pathways and increase intracellular reactive oxygen leading to apoptosis. This review summarizes the reported phytochemicals in avocado fruit and discusses their molecular mechanisms and targets. These studies suggest that individual and combinations of phytochemicals from the avocado fruit may offer an advantageous dietary strategy in cancer prevention.

Results of a Phase II trial of oral bexarotene (Targretin) combined with interferon alfa-2b (Intron-A) for patients with cutaneous T-cell lymphoma

BACKGROUND

Bexarotene is one of the most active single agents for the treatment of recurring or refractory cutaneous T-cell lymphoma (CTCL). Interferon alfa has also been used for many years as an effective treatment for this disease. The results in recent case reports of the combination of bexarotene and interferon alfa have been promising. Based on more extensive results reported with the combination of other retinoids with interferon alfa, the present study attempted to determine the response rate, response duration, and safety of bexarotene (Targretin capsules, Ligand Pharmaceuticals, San Diego, Calif) alone and then with the addition of interferon alfa-2b (Intron-A, Schering-Plough, Kenilworth, NJ).

METHODS

Patients with biopsy-proven CTCL, TNM stages IB, IIA, IIB-IV, were treated with oral bexarotene 300 mg/m2/day for at least 8 weeks. If a complete response was not seen after 8 weeks, interferon alfa-2b 3 million units (MU) subcutaneously was added, and increased to 5 MU if tolerated, 3 times a week.

RESULTS

A total of 22 patients were enrolled at 5 sites, and 18 patients were assessable for response. Overall response rate for combined bexarotene and interferon alfa was 39% (95% confidence interval [CI]: 17%-64%), including 1 patient with a clinical complete response, 6 patients with partial response, 3 patients with stable disease, and 8 patients with progressive disease. Three partial responses were first noted during the bexarotene-alone phase. Adverse events were generally manageable, and only 1 patient was withdrawn from study for hypertriglyceridemia.

CONCLUSIONS

The addition of interferon alfa-2b did not increase the response rate that would have been expected with bexarotene alone.

Sulforaphane as a promising molecule for fighting cancer

A number of natural compounds with inhibitory effects on tumorigenesis have been identified from our diet. Several studies have documented the cancer-preventive activity of a significant number of isothiocyanates (ITCs), the majority of which occur in plants, especially in Cruciferous vegetables. The most characterized ITC is sulforaphane (SFN). SFN has received a great deal of attention because of its ability to simultaneously modulate multiple cellular targets involved in cancer development, including: (i) DNA protection by modulating carcinogen-metabolizing enzymes and blocking the action of mutagens; (ii) inhibition of cell proliferation and induction of apoptosis, thereby retarding or eliminating clonal expansion of initiated, transformed, and/or neoplastic cells; (iii) inhibition of neoangiogenesis, progression of benign tumors to malignant tumors, and metastasis formation. SFN is therefore able to prevent, delay, or reverse preneoplastic lesions, as well as to act on cancer cells as a therapeutic agent. Taking into account this evidence and its favorable toxicological profile, SFN can be viewed as a conceptually promising agent in cancer prevention and/or therapy.

Phytochemicals and cancer

Epidemiological studies showing a protective effect of diets rich in fruits and vegetables against cancer have focused attention on the possibility that biologically-active plant secondary metabolites exert anti-carcinogenic activity. This huge group of compounds, now collectively termed ‘phytochemicals’, provides much of the flavour and colour of edible plants and the beverages derived from them. Many of these compounds also exert anti-carcinogenic effects in animal models of cancer, and much progress has been made in defining their many biological activities at the molecular level. Such mechanisms include the detoxification and enhanced excretion of carcinogens, the suppression of inflammatory processes such as cyclooxygenase-2 expression, inhibition of mitosis and the induction of apoptosis at various stages in the progression and promotion of cancer. However, much of the research on phytochemicals has been conducted in vitro, with little regard to the bioavailability and metabolism of the compounds studied. Many phytochemicals present in plant foods are poorly absorbed by human subjects, and this fraction usually undergoes metabolism and rapid excretion. Some compounds that do exert anti-carcinogenic effects at realistic doses may contribute to the putative benefits of plant foods such as berries, brassica vegetables and tea, but further research with human subjects is required to fully confirm and quantify such benefits. Chemoprevention using pharmacological doses of isolated compounds, or the development of ‘customised’ vegetables, may prove valuable but such strategies require a full risk–benefit analysis based on a thorough understanding of the long-term biological effects of what are often surprisingly active compounds.

A European carotenoid database to assess carotenoid intakes and its use in a five-country comparative study

A food frequency questionnaire (FFQ) and carotenoid database with information onα- and β-carotene, lutein, lycopene and β-cryptoxanthin was prepared and used to compare the carotenoid intakes in five European countries: UK, Republic of Ireland, Spain, France and The Netherlands. Eighty, age- (25–45 years) and sex-matched volunteers were recruited in each of the five countries. A FFQ and carotenoid database was prepared of the most commonly consumed carotenoid rich foods in the participating countries and the information was used to calculate frequency and intake of carotenoid-rich foods. The median total carotenoid intake based on the sum of the five carotenoids, was significantly higher (P<0.05) in France (16.1 mg/day) and lower in Spain (9.5 mg/day,) than the other countries, where the average intake was approximately 14 mg/day. Comparison of dietary source of carotenoids showed that carrots were the major source of β-carotene in all countries except Spain where spinach was most important. Likewise, carrots were also the main source ofα-carotene. Tomato or tomato products, were the major source of lycopene. Lutein was mainly obtained from peas in Republic of Ireland and the UK, however, spinach was found to be the major source in other countries. In all countries, β-cryptoxanthin was primarily obtained from citrus fruit. Comparing the data with that from specific European country studies suggests that the FFQ and carotenoid database described in the present paper can be used for comparative dietary intake studies within Europe. The results show that within Europe there are differences in the specific intake of some carotenoids which are related to different foods consumed by people in different countries.

Effects of ingestion of tomatoes, tomato juice and tomato purée on contents of lycopene isomers, tocopherols and ascorbic acid in human plasma as well as on lycopene isomer pattern

Tomatoes are an important part of the diet. Lycopene, the predominant carotenoid in tomatoes, is hypothesised to mainly mediate the health benefits of tomato products. Anticancer activity of tomato products and lycopene has been suggested by numerous studies. The aim of the present study was to investigate the effect of ingestion of three different tomato-based foodstuffs on plasma contents of lycopene, tocopherols and ascorbic acid. Because isomers of lycopene may have different biological activities, a special interest was to look how the lycopene isomer pattern is changed depending on the matrix of tomato products. Following a 2-week depletion phase volunteers ingested 12·5mg lycopene/d for 4 weeks comprising tomatoes, tomato juice or tomato purée. The basal levels of lycopene in plasma were comparable for all groups and decreased significantly during the 2 weeks of depletion to approximately half of the basal values. Following intervention, plasma lycopene concentration increased significantly. Conversely, supplementation did not significantly affect levels of tocopherols and ascorbic acid in plasma. Regarding isomers of lycopene, the (Z)-lycopene:(all-E)-lycopene plasma isomer ratio was significantly changed during the study for all groups. A remarkable enrichment of the relative contents of (5Z)-lycopene was observed during the depletion period, which supports the hypothesis that lycopene (Z)-isomers are formed within the human body after ingestion of (all-E)-lycopene. After dietary intervention with lycopene-rich products the isomer ratios returned to those observed at the start of the study. Further investigations will clarify the process of isomerisation in more detail.

Antioxidant status and risk of cancer in the SU.VI.MAX study: is the effect of supplementation dependent on baseline levels?

The SUpplementation en VItamines et Mineraux AntioXydants (SU.VI.MAX) study, a randomised double-blind, primary-prevention trial showed that after 7·5 years, low-dose antioxidant supplementation lowered the total cancer incidence in men, but not in women. To explain this difference in the impact of antioxidant supplementation in men and women, we hypothesised that the effect of supplementation is dependent on initial antioxidant status; 12 741 French adults (7713 females aged 35–60 years; 5028 males aged 45–60 years) received daily antioxidant supplementation (120 mg vitamin C, 30 mg vitamin E, 6 mg β-carotene, 100 μg Se, 20 mg Zn daily) or a matching placebo. Cut-off limits for baseline serum concentrations of the different antioxidant vitamins and minerals were defined as follows for both men and women: 0·3 μmol/l for β-carotene, 11·4 μmol/l for vitamin C, 15 μmol/l for vitamin E, 0·75 μmol/l for Se and 10·7 μmol/l for Zn. The percentage of men with serum concentrations under cut-off limits was higher for vitamins C and E and β-carotene in those who developed a cancer than in those who did not. The risk of cancer was higher in men with baseline concentrations of serum vitamin C or vitamin E under cut-off limits, but not in women. The effect of supplementation was greater in men with baseline serum concentrations of vitamin C, vitamin E and β-carotene below the cut-off limits compared with those above it. This effect was maintained only for vitamin E after adjustment for age, tobacco, and alcohol consumption and BMI. No effect of supplementation could be seen in women. Baseline antioxidant status is related to the risk of cancer in men but not in women and therefore does not entirely explain the differences observed in the effect of antioxidant supplementation on cancer risk between sexes in the SU.VI.MAX study.

Is there a role for dietary salicylates in health?

Acetylsalicylic acid (aspirinTM; 2-acetoxybenzoic acid) has been used for >100 years for pain relief and to treat inflammatory conditions and fevers. More recently, regular intake has been associated with decreased incidence of certain cancers, particularly colon cancer. After absorption aspirin is very rapidly hydrolysed to salicylic acid (2-hydroxybenzoic acid). The anti-cancer effects of aspirin may be a result of salicylic acid reducing the transcription of prostaglandin H2-synthase and thereby the synthesis of pro-inflammatory and potentially-neoplastic prostaglandins. Salicylic acid is widely present in plants and functions as a hormonal mediator of the systemic acquired resistance response to pathogen attack and environmental stress. Thus, it is present in a large range of fruit, vegetables, herbs and spices of dietary relevance. Consequently, the recognised effect of consuming fruit and vegetables on lowering risk of colon cancer may be partly attributable to salicylates in plant-based foods. The present review discusses which types of fruit and vegetables are the richest source of salicylates and whether they are sufficiently released from the food matrix to modify the key cellular events associated with the pathogenesis of colon cancer.

Selenium in cancer prevention: a review of the evidence and mechanism of action

Se is an unusual trace element in having its own codon in mRNA that specifies its insertion into selenoproteins as selenocysteine (SeCys), by means of a mechanism requiring a large SeCys-insertion complex. This exacting insertion machinery for selenoprotein production has implications for the Se requirements for cancer prevention. If Se may protect against cancer, an adequate intake of Se is desirable. However, the level of intake in Europe and some parts of the world is not adequate for full expression of protective selenoproteins. The evidence for Se as a cancer preventive agent includes that from geographic, animal, prospective and intervention studies. Newly-published prospective studies on oesophageal, gastric-cardia and lung cancer have reinforced previous evidence, which is particularly strong for prostate cancer. Interventions with Se have shown benefit in reducing the risk of cancer incidence and mortality in all cancers combined, and specifically in liver, prostate, colo-rectal and lung cancers. The effect seems to be strongest in those individuals with the lowest Se status. As the level of Se that appears to be required for optimal effect is higher than that previously understood to be required to maximise the activity of selenoenzymes, the question has been raised as to whether selenoproteins are involved in the anti-cancer process. However, recent evidence showing an association between Se, reduction of DNA damage and oxidative stress together with data showing an effect of selenoprotein genotype on cancer risk implies that selenoproteins are indeed implicated. The likelihood of simultaneous and consecutive effects at different cancer stages still allows an important role for anti-cancer Se metabolites such as methyl selenol formed from γ-glutamyl-selenomethyl-SeCys and selenomethyl-SeCys, components identified in certain plants and Se-enriched yeast that have anti-cancer effects. There is some evidence that Se may affect not only cancer risk but also progression and metastasis. Current primary and secondary prevention trials of Se are underway in the USA, including the Selenium and Vitamin E Cancer Prevention Trial (SELECT) relating to prostate cancer, although a large European trial is still desirable given the likelihood of a stronger effect in populations of lower Se status.

A Role for Milk Proteins and their Peptides in Cancer Prevention

A role for the amount and type of dietary protein in the etiology of cancer has not been studied extensively. Nevertheless, there is no compelling evidence from epidemiological studies to indicate that protein, at levels usually consumed, is a risk factor for cancer. On the other hand, animal studies suggest that certain peptides and amino acids derived from dietary proteins may influence carcinogenesis. The predominant protein in milk, casein, its peptides, but not liberated amino acids, have antimutagenic properties. Animal models, usually for colon and mammary tumorigenesis, nearly always show that whey protein is superior to other dietary proteins for suppression of tumour development. This benefit is attributed to its high content of cystine/cysteine and gamma-glutamylcyst(e)ine dipeptides, which are efficient substrates for the synthesis of glutathione. Glutathione is an ubiquitous cellular antioxidant that directly or through its associated enzymes destroys reactive oxygen species, detoxifies carcinogens, maintains proteins in a reduced state and ensures a competent immune system. Various experiments showed that tumour prevention by dietary whey protein was accompanied by increased glutathione levels in serum and tissues as well as enhanced splenic lymphocyte proliferation, phagocytosis and natural killer, T helper and cytotoxic T cell activity. Whey protein components, beta-lactoglobulin, alpha-lactalbumin and serum albumin were studied infrequently, but results suggest they have anticancer potential. The minor component lactoferrin has received the most attention; it inhibits intestinal tumours and perhaps tumours at other sites. Lactoferrin acts by induction of apoptosis, inhibition of angiogenesis, modulation of carcinogen metabolising enzymes and perhaps acting as an iron scavenger. Supplementing cows with selenium increases the content of selenoproteins in milk, which on isolation inhibited colon tumorigenesis in rats.

Ins and outs of dietary phytochemicals in cancer chemoprevention

A voluminous number of evidence suggests that an increased consumption of fruit and vegetables is a relatively easy and practical strategy to reduce significantly the incidence of chronic diseases, such as cancer, cardiovascular diseases and other aging-related pathologies. This review will critically discuss the applications of chemical and dietary chemoprevention, intending the protecting effects against cancer of chemically synthesized molecules, or phytochemicals present in the regular diet. The length of chemopreventive treatments requires the administration of low doses of chemopreventive agents, to avoid toxic side effects. This poses the question, here discussed, of the bioavailability of these compounds, usually very modest. Another key issue is whether purified phytochemicals have the same protective effects, as do the whole food or mixture of foods in which these compounds are present. These aspects will be analysed at the light of the "antioxidant hypothesis" in cancer prevention and the "combination chemoprevention", both referring to the pleiotropic and synergistic effects of compounds present in the diet. Single molecules may evolve in perfect chemopreventive agents, as in the case of tamoxifen, or generate ambiguity. Resveratrol and quercetin represent two paradoxes, discussed here.

Natural chlorophyll inhibits aflatoxin B1-induced multi-organ carcinogenesis in the rat

Chemoprevention by chlorophyll (Chl) was investigated in a rat multi-organ carcinogenesis model. Twenty-one male F344 rats in three gavage groups (N = 7 rats each) received five daily doses of 250 microg/kg [(3)H]-aflatoxin B(1) ([(3)H]-AFB(1)) alone, or with 250 mg/kg chlorophyllin (CHL), or an equimolar amount (300 mg/kg) of Chl. CHL and Chl reduced hepatic DNA adduction by 42% (P = 0.031) and 55% (P = 0.008), respectively, AFB(1)-albumin adducts by 65% (P < 0.001) and 71% (P < 0.001), respectively, and the major AFB-N(7)-guanine urinary adduct by 90% (P = 0.0047) and 92% (P = 0.0029), respectively. To explore mechanisms, fluorescence quenching experiments established formation of a non-covalent complex in vitro between AFB(1) and Chl (K(d) = 1.22 +/- 0.05 microM, stoichiometry = 1Chl:1AFB(1)) as well as CHL (K(d) = 3.05 +/- 0.04 microM; stoichiometry = 1CHL:1AFB(1)). The feces of CHL and Chl co-gavaged rats contained 137% (P = 0.0003) and 412% (P = 0.0048) more AFB(1) equivalents, respectively, than control feces, indicating CHL and Chl inhibited AFB(1) uptake. However, CHL or Chl treatment in vivo did not induce hepatic quinone reductase (NAD(P)H:quinone oxidoreductase) or glutathione S-transferase (GST) above control levels. These results are consistent with a mechanism involving complex-mediated reduction of carcinogen uptake, and do not support a role for phase II enzyme induction in vivo under these conditions. In a second study, 30 rats in three experimental groups were dosed as in study 1, but for 10 days. At 18 weeks, CHL and Chl had reduced the volume percent of liver occupied by GST placental form-positive foci by 74% (P < 0.001) and 77% (P < 0.001), respectively compared with control livers. CHL and Chl reduced the mean number of aberrant crypt foci per colon by 63% (P = 0.0026) and 75% (P = 0.0004), respectively. These results show Chl and CHL provide potent chemoprotection against early biochemical and late pathophysiological biomarkers of AFB(1) carcinogenesis in the rat liver and colon.

Tumor-protective and tumor-promoting actions of dietary whey proteins in an N-methyl-N-nitrosourea model of rat mammary carcinogenesis

The mammary tumor-protective effects of dietary factors are considered to be mediated by multiple signaling pathways, consistent with the heterogeneous nature of the disease and the distinct genetic profiles of tumors arising from diverse mammary cell populations. In a 7,12-dimethylbenz(a)anthracene-induced model of carcinogenesis, we showed previously that female Sprague-Dawley rats exposed to AIN-93G diet containing whey protein hydrolysate (WPH) beginning at gestation Day 4 had reduced tumor incidence than those exposed to diet containing casein (CAS), due partly to increased mammary differentiation and reduced activity of phase I metabolic enzymes. Here, we evaluated the tumor-protective effects of these same dietary proteins to the direct-acting carcinogen N-methyl-N-nitrosourea (NMU). We found that lifetime exposure to WPH, relative to CAS, decreased mammary tumor incidence and prolonged the appearance of tumors in NMU-treated female rats, with no corresponding effects on tumor multiplicity. At 115 days post-NMU, histologically normal mammary glands from WPH-fed tumor-bearing rats had increased gene expression for the tumor suppressor BRCA1 and the differentiation marker kappa-casein than those of CAS-fed tumor-bearing rats. Tumor-bearing rats from the WPH group had more advanced tumors, with a greater incidence of invasive ductal carcinoma than ductal carcinoma in situ and higher serum C-peptide levels than corresponding rats fed CAS. WPH-fed tumor-bearing rats were also heavier after NMU administration than CAS tumor-bearing rats, although no correlation was noted between body weight and C-peptide levels for either diet group. Results demonstrate the context-dependent tumor-protective and tumor-promoting effects of WPH; provide support for distinct signaling pathways underlying dietary effects on development of mammary carcinoma; and raise provocative questions on the role of diet in altering the prognosis of existing breast tumors.

Folate and risk of breast cancer: a meta-analysis

BACKGROUND

Epidemiologic findings are inconsistent concerning risk for breast cancer associated with low folate intake or blood folate levels. We performed a meta-analysis of prospective and case-control studies to examine folate intake and levels in relation to risk of breast cancer.

METHODS

We searched MEDLINE for studies of this association that were published in any language from January 1, 1966, through November 1, 2006. Study-specific risk estimates were pooled by use of a random-effects model. All statistical tests were two-sided.

RESULTS

Folate intake in increments of 200 microg/day was not associated with the risk of breast cancer in prospective studies (estimated summary relative risk [RR] = 0.97, 95% confidence interval [CI] = 0.88 to 1.07, for dietary folate [eight studies; 302,959 participants and 8367 patients with breast cancer], and RR = 1.01, 95% CI = 0.97 to 1.05, for total folate [six studies; 306,209 participants and 8165 patients with breast cancer]) but was statistically significantly inversely associated with risk in case-control studies (estimated summary odds ratio [OR] = 0.80, 95% CI = 0.72 to 0.89, for dietary folate [13 studies; 8558 case patients and 10,812 control subjects], and OR = 0.93, 95% CI = 0.81 to 1.07, for total folate [three studies; 2184 case patients and 3233 control subjects]). High blood folate levels versus low levels were not statistically significantly associated with the risk of breast cancer in prospective studies (OR = 0.81, 95% CI = 0.59 to 1.10 [three studies]) or in case-control studies (OR = 0.41, 95% CI = 0.15 to 1.10 [two studies]). Among the two prospective studies and two case-control studies that stratified by alcohol consumption, high folate intake (comparing the highest with the lowest category) was associated with a statistically significant decreased risk of breast cancer among women with moderate or high alcohol consumption (summary estimate = 0.51, 95% CI = 0.41 to 0.63) but not among women with low or no alcohol consumption (summary estimate = 0.95, 95% CI = 0.78 to 1.15). Few studies examined whether the relation between folate intake and breast cancer was modified by intakes of methionine or vitamins B6 and B12, and the findings were inconsistent.

CONCLUSION

No clear support for an overall relationship between folate intake or blood folate levels and breast cancer risk was found. Adequate folate intake may reduce the increased risk of breast cancer that has been associated with moderate or high alcohol consumption.

Prolonged Effect of Calcium Supplementation on Risk of Colorectal Adenomas in a Randomized Trial

BACKGROUND

Calcium supplementation has been shown to decrease the risk of recurrence of colorectal adenomas in randomized trials. However, the duration of this protective effect after cessation of active supplementation is not known.

METHODS

In the Calcium Polyp Prevention Study, 930 subjects with a previous colorectal adenoma were randomly assigned from November 1988 through April 1992 to receive placebo or 1200 mg of elemental calcium daily for 4 years. The Calcium Follow-up Study was an observational phase of the trial that tracked adenoma occurrence for an average of 7 years after the end of randomized treatment and gathered information regarding the use of medications, vitamins, and supplements during that time. We obtained follow-up information for 822 subjects, 597 of whom underwent at least one colonoscopy after the end of study treatment and are included in this analysis. Generalized linear models were used to compute relative risks (RRs) and 95% confidence intervals (CIs) for the effect of randomized calcium treatment on risk of adenoma recurrence during the first 5 years after study treatment ended and during the subsequent 5 years. Statistical tests were two-sided.

RESULTS

During the first 5 years after randomized treatment ended, subjects in the calcium group still had a substantially and statistically significantly lower risk of any adenoma than those in the placebo group (31.5% versus 43.2%; adjusted RR = 0.63, 95% CI = 0.46 to 0.87, P = .005) and a smaller and not statistically significant reduction in risk of advanced adenomas (adjusted RR = 0.85, 95% CI = 0.43 to 1.69, P = .65). However, the randomized treatment was not associated with the risk of any type of polyp during the next 5 years. The findings were broadly similar when the analysis was restricted to subjects who did not report use of any calcium supplements after the treatment phase of the trial ended.

CONCLUSION

The protective effect of calcium supplementation on risk of colorectal adenoma recurrence extends up to 5 years after cessation of active treatment, even in the absence of continued supplementation.

Estimated Asian adult soy protein and isoflavone intakes

There is substantial interest in the possible anticancer effects of soy foods. In part, this is because of the historically low incidence rates of breast and prostate cancer in Asia. Of the several putative soybean chemopreventive agents, isoflavones have received the most attention. Awareness of this research has led increasing numbers of consumers to use soy foods, isoflavone-fortified foods, and isoflavone supplements. Therefore, there is a need for guidance regarding appropriate isoflavone intake levels. To this end, this article analyzed soy protein (as a surrogate for isoflavones) and isoflavone intake of the major soy food-consuming countries using individual dietary surveys for the bulk of the information. In total, 24 surveys from 4 countries that met the inclusion criteria were identified: Japan (n = 11), China (n = 7), Hong Kong (n = 4), and Singapore (n = 2). The results indicate that older Japanese adults consume approximately 6-11 g of soy protein and 25-50 mg of isoflavones (expressed as aglycone equivalents) per day. Intake in Hong Kong and Singapore is lower than in Japan, whereas significant regional intake differences exist for China. Evidence suggests that < or =10% of the Asian population consumes as much as 25 g of soy protein or 100 mg of isoflavones per day. The applicability of these findings for making soy intake recommendations for non-Asians is discussed.