Nutrition intervention trials in Linxian, China: multiple vitamin/mineral supplementation, cancer incidence, and disease-specific mortality among adults with esophageal dysplasia

Antioxidant supplements for prevention of gastrointestinal cancers: a systematic review and meta-analysis

BACKGROUND

Oxidative stress can cause cancer. Our aim was to establish whether antioxidant supplements reduce the incidence of gastrointestinal cancer and mortality.

METHODS

With the Cochrane Collaboration methodology, we reviewed all randomised trials comparing antioxidant supplements with placebo for prevention of gastrointestinal cancers. We searched electronic databases and reference lists (February, 2003). Outcome measures were incidence of gastrointestinal cancers, overall mortality, and adverse effects. Outcomes were analysed with fixed-effect and random-effects model meta-analyses and were reported as relative risk with 95% CIs.

FINDINGS

We identified 14 randomised trials (n=170,525). Trial quality was generally high. Heterogeneity of results was low to moderate. Neither the fixed-effect (relative risk 0.96, 95% CI 0.88-1.04) nor random-effects meta-analyses (0.90, 0.77-1.05) showed significant effects of supplementation with beta-carotene, vitamins A, C, E, and selenium (alone or in combination) versus placebo on oesophageal, gastric, colorectal, pancreatic, and liver cancer incidences. In seven high-quality trials (n=131727), the fixed-effect model showed that antioxidant significantly increased mortality (1.06, 1.02-1.10), unlike the random-effects meta-analysis (1.06, 0.98-1.15). Low-quality trials showed no significant effect of antioxidant supplementation on mortality. The difference between the mortality estimates in high-quality and low-quality trials was significant (Z=2.10, p=0.04 by test of interaction). beta-carotene and vitamin A (1.29, 1.14-1.45) and beta-carotene and vitamin E (1.10, 1.01-1.20) significantly increased mortality, whereas beta-carotene alone only tended to increase mortality (1.05, 0.99-1.11). In four trials (three with unclear or inadequate methodology), selenium showed significant beneficial effect on the incidence of gastrointestinal cancer.

INTERPRETATION

We could not find evidence that antioxidant supplements can prevent gastrointestinal cancers; on the contrary, they seem to increase overall mortality. The potential preventive effect of selenium should be studied in adequate randomised trials.

Mechanisms of mammary cancer chemoprevention by organoselenium compounds

Searching for optimal diets and for naturally occurring agents in routinely consumed foods that may inhibit cancer development, although challenging, constitutes a valuable and plausible approach to finding ways to control and prevent cancer. To date, the use of the micronutrient selenium in human clinical trials is limited but the outcome of these investigations indicates that selenium is one of the most promising agents. Data presented in this mini-review indicate that the dose and the form (structure) in which selenium is used are the most critical determinants of success in future clinical trials. The focus of this mini-review is on the mechanisms of mammary cancer chemoprevention by organoselenium compounds. Among the naturally occurring organoselenium compounds, Se-Methylselenocysteine is more efficacious than the most extensively studied forms, such as selenomethionine. However, we showed that synthetic organoselenium compounds can be tailored to achieve greater chemopreventive efficacy with minimal side effects by structural modifications; it is evident that synthetic agents are superior to the inorganic selenite, naturally occurring selenium compounds and their sulfur-containing analogs. We have demonstrated that 1,4-phenylenebis (methylene) selenocyanate (p-XSC) and its putative metabolite glutathione conjugate (p-XSeSG) are highly promising agents in the chemoprevention of mammary carcinogenesis in the 7,12-dimethylbenz[a]anthracene (DMBA)-rat mammary tumor model system. Both compounds inhibit the initiation phase of carcinogenesis by inhibiting DMBA-DNA adduct formation in the target organ in vivo. cDNA microarray analysis indicates that both selenium compounds alter genes in a manner that leads to inhibition of cell proliferation and induction of apoptosis; modulation of apoptosis and cell proliferation can account for chemoprevention during the post-initiation phase of mammary carcinogenesis. Using a rat mammary cancer cell line, we compared p-XSC and p-XSeSG as inhibitors of cell proliferation; depending on the selenium dose and time point selected, p-XSC was comparable to or better than p-XSeSG. Collectively, the results described here, suggest that the molecular targets modulated by organoselenium compounds are highly useful indicators of success in clinical cancer chemoprevention trials.

Hormones and Supplements: Do They Work?: Micronutrient Supplementation in Later Life: Limited Evidence for Benefit

The importance of attaining adequate macronutrient and micronutrient intake throughout the life course is essential for the maintenance of health. Claims have been made for the benefits of micronutrient supplementation in later life, and this review considers the strength of the evidence behind these claims focusing on studies with cardiovascular, cancer, eye health, immune, and cognitive end points. While observational data suggest the presence of a link between dietary micronutrient intake and health outcomes, evidence from large randomized controlled trials does not support the use of antioxidant vitamin or mineral supplements among well-nourished older populations. Moreover, there is evidence of possible adverse affects of micronutrient supplementation. In conclusion, the considerable enthusiasm for the use of micronutrient, especially antioxidant, supplements as anti-aging treatments or as treatments for specific diseases of later life is not supported by the currently available scientific literature.

Role of Se-dependent glutathione peroxidases in gastrointestinal inflammation and cancer

Increase in reactive oxygen species plays an integral part in the inflammatory response, and chronic inflammation increases cancer risk. Selenium-dependent glutathione peroxidase (GPX) is well recognized for its antioxidant, and thus anti-inflammatory, activity. However, due to the multiple antioxidant families present in the gastrointestinal tract, it has been difficult to demonstrate the importance of individual antioxidant enzymes. Using genetically altered mice deficient in individual Gpx genes has provided insight into the physiological functions of these genes. Insufficient GPX activity in the mucosal epithelium can trigger acute and chronic inflammation. The presence of certain microflora, such as Helicobacter species, may affect cancer risk significantly. However, when damaged cells have progressed into a precancerous status, increased GPX activity may become procarcinogenic, presumably due to inhibition of hydroperoxide-mediated apoptosis. This review summarizes the current view of GPX in inflammation and cancer with emphasis on the GI tract.

Dietary depletion of vitamin E and vitamin A inhibits mammary tumor growth and metastasis in transgenic mice

We showed previously that dietary antioxidant depletion enhances tumor reactive oxygen species (ROS) and apoptosis, resulting in a reduction in brain tumor size in the TgT(121) transgenic mouse model, a nonmetastatic tumor model. Here, in a transgenic mouse model of mammary tumorigenesis with defined rates of tumor growth and lung-targeted metastasis, we determined the ability of dietary antioxidant depletion to inhibit tumor growth and metastasis. Compared with control mice fed a standard diet, antioxidant-depleted mice exhibited tumor-targeted generation of ROS manifested by increased levels of oxidatively modified DNA/RNA (8- hydroxy-2'-deoxyguanine, 8-hydroxyguanine) and lipid peroxidation (4-hydroxy-2-nonenal) in primary and metastatic tumor foci. In addition to increased tumor-targeted ROS, the number of apoptotic cells was increased approximately 500% (P < 0.01) and terminal dUTP nucleotide DNA end-labeling-positive cells 200% (P < 0.01) in mice fed the antioxidant-depleted diet, whereas the percentage of tumor cells undergoing mitosis was >50% lower than in controls (P < 0.01). The proportional distribution of small (<1.5 cm) and large (> or = 1.5 cm) primary mammary tumors differed. The mice fed the antioxidant-depleted diet had more small primary tumors (P <0.05) and fewer large primary tumors (P < 0.05). Importantly, they also had fewer lung metastatic tumor foci compared with mice fed the control diet (4.5 +/- 1.3 vs. 15.8 +/- 8.5 foci/lung, P < 0.01). These findings may be important in understanding the role of dietary antioxidant vitamins in tumor growth and metastasis.

Diet, nutrition and the prevention of cancer

OBJECTIVE

To assess the epidemiological evidence on diet and cancer and make public health recommendations.

DESIGN

Review of published studies, concentrating on recent systematic reviews, meta-analyses and large prospective studies.

CONCLUSIONS AND RECOMMENDATIONS

Overweight/obesity increases the risk for cancers of the oesophagus (adenocarcinoma), colorectum, breast (postmenopausal), endometrium and kidney; body weight should be maintained in the body mass index range of 18.5-25 kg/m(2), and weight gain in adulthood avoided. Alcohol causes cancers of the oral cavity, pharynx, oesophagus and liver, and a small increase in the risk for breast cancer; if consumed, alcohol intake should not exceed 2 units/d. Aflatoxin in foods causes liver cancer, although its importance in the absence of hepatitis virus infections is not clear; exposure to aflatoxin in foods should be minimised. Chinese-style salted fish increases the risk for nasopharyngeal cancer, particularly if eaten during childhood, and should be eaten only in moderation. Fruits and vegetables probably reduce the risk for cancers of the oral cavity, oesophagus, stomach and colorectum, and diets should include at least 400 g/d of total fruits and vegetables. Preserved meat and red meat probably increase the risk for colorectal cancer; if eaten, consumption of these foods should be moderate. Salt preserved foods and high salt intake probably increase the risk for stomach cancer; overall consumption of salt preserved foods and salt should be moderate. Very hot drinks and foods probably increase the risk for cancers of the oral cavity, pharynx and oesophagus; drinks and foods should not be consumed when they are scalding hot. Physical activity, the main determinant of energy expenditure, reduces the risk for colorectal cancer and probably reduces the risk for breast cancer; regular physical activity should be taken.

Review of vitamin E and selenium in the prevention of prostate cancer: implications of the selenium and vitamin E chemoprevention trial

The National Cancer Institute in cooperation with the Southwest Oncology Group has begun one of the largest prostate cancer prevention studies to date, the Selenium and Vitamin E Chemoprevention Trial (SELECT). The purpose of this article is to review the evidence and discuss the individual antioxidant compounds under study. The authors comprehensively reviewed the peer-reviewed literature on the chemoprevention of prostate cancer with emphasis on the antioxidants vitamin E and selenium. The credible leads for the primary prevention of prostate cancer using selenium and vitamin E have emerged as secondary findings from randomized controlled trials with corroborative evidence from observational and in vitro studies. Selenium and vitamin E are widely available compounds that are safe if taken in moderation, with relatively few adverse effects. The evidence in support of the antioxidants in the primary prevention of prostate cancer is promising, and the next step in definitively answering the question has been addressed by the investigators of SELECT. The SELECT study will define the role of the antioxidants selenium and vitamin E in the prevention of prostate cancer; complete data from the study will be available in 12 years.

Selenium and its relationship to cancer: an update

Selenomethionine (Semet) is the major seleno-compound in cereal grains and enriched yeast whereas Se-methylselenocysteine (SeMCYS) is the major seleno-compound in Se-accumulator plants and some plants of economic importance such as garlic and broccoli exposed to excess Se. Animals can metabolize both Semet and SeMCYS. Epidemiological studies have indicated an inverse relationship between Se intake and the incidence of certain cancers. Blood or plasma levels of Se are usually lower in patients with cancer than those without this disorder, but inconsistent results have been found with toenail-Se values and the incidence of cancer. There have been eight trials with human subjects conducted on the influence of Se on cancer incidence or biomarkers, and except for one, all have shown a positive benefit of Se on cancer reduction or biomarkers of this disorder. This is consistent with about 100 small-animal studies where Se has been shown to reduce the incidence of tumours in most of these trials. Se-enriched yeast is the major form of Se used in trials with human subjects. In the mammary-tumour model, SeMCYS has been shown to be the most effective seleno-compound identified so far in reduction of tumours. Several mechanisms have been proposed on the mechanism whereby Se reduces tumours. Even though SeMCYS was shown to be the most effective seleno-compound in the reduction of mammary tumours, it may not be the most effective seleno-compound for reduction of colon tumours.

Selenium: epidemiology and basic science

PURPOSE

The trace element selenium, a constituent of antioxidant enzymes, has been proposed as a chemopreventive agent for prostate and other cancers.

MATERIALS AND METHODS

Published epidemiological and scientific studies relating to the potential clinical and molecular role of selenium in preventing cancer are reviewed and summarized. A unifying hypothesis underlying observations on the effect of selenium on early events in carcinogenesis is presented.

RESULTS

A large body of epidemiological evidence, including observational, case-control, cohort and randomized controlled clinical trials, support the proposition that selenium may prevent prostate cancer in humans. The available data suggest a beneficial effect for men with low baseline serum or toenail selenium levels, without preexisting tumors, with serum prostate specific antigen less than 4 ng/ml and in current or former smokers. Molecular data demonstrate that selenium prevents clonal expansion of nascent tumors by causing cell cycle arrest, promoting apoptosis, and modulating p53 dependent DNA repair mechanisms.

CONCLUSIONS

These observations give strong scientific support to ongoing clinical trials testing the ability of selenium to prevent prostate cancer and the progression of high grade prostatic intraepithelial neoplasia to cancer.

Vitamin E: the evidence for multiple roles in cancer

There is accumulating evidence that vitamin E may have different roles in the prevention and treatment of cancer. The purpose of this review is to summarize and evaluate this evidence and to suggest future avenues of research. A comprehensive literature review of vitamin E and cancer was conducted. Articles were organized into the following categories: 1) cancer prevention, 2) direct antineoplastic activity, 3) augmentation of chemotherapy effects, and 4) attenuation or treatment of chemotherapy toxicity. The evidence was systematically evaluated using guidelines developed by the U.S. Preventative Services Task Force. There is evidence to suggest that those individuals with higher serum vitamin E levels and those receiving vitamin E supplementation have a decreased risk of some cancers, including lung, prostate, stomach, and gastrointestinal carcinoma. However, these results differed depending on the study design and the population studied. There is insufficient evidence to support anticancer activity and attenuation of chemotherapy toxicity by vitamin E. Vitamin E is likely to be important in the prevention of some cancers. The therapeutic role of vitamin E is poorly understood. Further research will be required before routine use of vitamin E in patients with cancer can be advocated in the clinical setting.

Prospective study of serum selenium concentrations and esophageal and gastric cardia cancer, heart disease, stroke, and total death

BACKGROUND

We previously reported an inverse association between prediagnostic serum selenium concentrations and the risk of esophageal squamous cell carcinoma (ESCC) and gastric cardia cancer (GCC) but not gastric noncardia cancer (GNCC) in a nested study from the Nutrition Intervention Trial in Linxian, China.

OBJECTIVE

We examined the relation between baseline serum selenium and the subsequent risk of death from ESCC, GCC, GNCC, heart disease (HD), stroke, and total death over 15 y of follow-up (1986-2001).

DESIGN

We measured baseline serum selenium concentrations in 1103 subjects randomly selected from a larger trial cohort. We identified 516 deaths during the 15-y follow up, including 75 from ESCC, 36 from GCC, 116 from HD, and 167 from stroke. Relative risks (RRs) and 95% CIs were estimated by using Cox proportional hazards regression models. Reported RRs estimated the change in risk conferred by a 25% increase in serum selenium relative to the population distribution. All estimates were adjusted for sex, age, smoking, drinking, and serum cholesterol.

RESULTS

We found significant inverse associations between baseline serum selenium and death from ESCC (RR: 0.83; 95% CI: 0.71, 0.98) and GCC (0.75; 0.59, 0.95). Trends toward inverse associations were noted for death from HD (0.89; 0.78, 1.01; P = 0.07), but no association was noted for total death (0.96; 0.90, 1.02) or stroke (0.99; 0.88, 1.11).

CONCLUSION

Population-wide selenium supplementation in the region of China with low serum selenium and high incidences of ESCC and GCC merits serious consideration.

Clinical models for testing chemopreventative agents in prostate cancer and overview of SELECT: the Selenium and Vitamin E Cancer Prevention Trial

Target populations for chemoprevention trials should include those at higher than average risk for the development of prostate cancer as defined by explicit epidemiologic and genetic criteria. Such populations include a "primary prevention" group without histologic or clinical evidence of cancer, and several clinical models of "secondary prevention," including those with clinically evident disease prior to definitive therapy and those at high risk of recurrence after therapy based on histology and/or biochemical status. Each risk group and clinical model has potential advantages and disadvantages, and the mechanisms which underlie disease development and progression in each group may be unique. These observations give rise to many potential clinical trials of specific agents. These trials should also include collection of data on potentially confounding influences on disease development and progression. Preclinical, epidemiologic, and Phase II data suggest that both selenium and vitamin E have potential efficacy in prostate cancer prevention. The experience of the Prostate Cancer Prevention Trial (PCPT) demonstrates the interest and dedication of healthy men to long-term studies of cancer prevention. SELECT, the Selenium and Vitamin E Cancer Prevention Trial, is an intergroup phase III, randomized, double-blind, placebo-controlled, population-based clinical trial designed to test the efficacy of selenium and vitamin E alone and in combination in the prevention of prostate cancer which builds on secondary analyses of large-scale chemoprevention trials for other cancers and the lessons of PCPT.

Diet and oral, pharyngeal, and esophageal cancer

Cancers of the upper digestive tract, including those arising in the oral cavity, pharynx, and esophagus, present a significant public health problem worldwide. These cancers are associated with high morbidity and mortality, and identification of protective factors is very important. A number of epidemiological studies have examined the association between vegetables, fruits, carotene, vitamin A, vitamin C, and vitamin E and oral, pharyngeal, and esophageal cancers. The results of 35 epidemiological studies, including one prospective cohort study, one nested case-control study, two randomized controlled trials, nine population-based case-control studies, and 22 hospital-based case-control studies, in addition to in vitro and animal studies, were examined to determine whether the criteria for causal assumption were satisfied for a protective role of these dietary components against development of oral, pharyngeal, and esophageal cancers. There is enough evidence to point to a preventive role of vegetable intake, including green vegetables, cruciferous vegetables, and yellow vegetables, total fruit intake, and citrus fruit intake. Yellow fruits are likely to be protective. Carotene, vitamin C, and vitamin E are protective, most likely in combination with each other and other micronutrients. The role of vitamin A is not clear because of conflicting findings in the studies reviewed.

Prospective study of serum vitamin E levels and esophageal and gastric cancers

Participants in the General Population Trial, a randomized nutrition intervention trial in Linxian, China, who received a combination of selenium, beta-carotene, and vitamin E supplements, had statistically significantly lower cancer mortality rates than those who did not receive the supplements. In the current study, we used a case-cohort design to examine the association between pre-trial serum vitamin E levels and the risks of developing esophageal and gastric cancers during the trial. We measured serum alpha- and gamma-tocopherol and cholesterol levels in 1072 case patients with incident esophageal squamous cell carcinoma (ESCC), gastric cardia cancer (GCC), or gastric noncardia cancer (GNCC) and in 1053 control subjects. The relative risks for comparisons of the highest to the lowest quartiles of serum alpha-tocopherol were 0.63 (95% confidence interval [CI] = 0.44 to 0.91) for ESCC, 0.84 (95% CI = 0.55 to 1.26) for GCC, and 2.05 (95% CI = 0.89 to 4.75) for GNCC. Serum gamma-tocopherol level was not associated with the incidence of any of these cancers. Our findings provide support for the role of alpha-tocopherol in the etiology of upper gastrointestinal cancers.

Design and synthesis of 4,6-di-tert-butyl-2,3-dihydro-5-benzofuranols as a novel series of antiatherogenic antioxidants

Antioxidants have been considered as potential antiatherogenic agents by inhibiting oxidation of low-density lipoprotein (LDL), albeit vitamin E, a natural antioxidant, has failed to show reduction on atherosclerosis in clinical trials. We have rationally designed and synthesized a novel series of antioxidants, 4,6-di-tert-butyl-2,3-dihydro-5-benzofuranols, to overcome the clinical limitation of vitamin E. In vitro, the compounds showed a potent inhibitory effect on lipid peroxidation detected as 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]pyrazin-3-one (MCLA)-dependent chemiluminescence in linoleic acid autoxidation. They also inhibited the LDL oxidation induced by Cu(2+), and the inhibition is more potent than that of vitamin E and probucol. In vivo, 4,6-di-tert-butyl-2,3-dihydro-2,2-dipentyl-5-benzofuranol (BO-653, 1f), an optimal compound, showed the highest concentration in plasma and LDL fraction in Watanabe heritable hyperlipidemic rabbits, due to its high affinity to LDL. The isolated LDL samples from the 1f-treated rabbits showed potent resistibility to LDL oxidation. Compound 1f has been taken into clinical trials.

The selenium and vitamin E cancer prevention trial

BACKGROUND

Evidence suggests that both selenium and vitamin E reduce the risk of prostate cancer. The Selenium and Vitamin E Cancer Prevention Trial (SELECT) is a randomized, prospective, double-blind study designed to determine whether selenium and vitamin E alone and in combination can reduce the risk of prostate cancer among healthy men.

MATERIALS AND METHODS

The preclinical and epidemiological evidence supporting a role for selenium and vitamin E as chemopreventive agents in prostate cancer are reviewed, and details of the trial design are presented. RESULTS. Preclinical, epidemiological, and phase III data from randomized, placebo-controlled clinical trials suggest that both selenium and vitamin E have potential efficacy in prostate cancer prevention. SELECT is a 2x2 factorial study with an accrual goal of 32,400 men with nonsuspicious DRE and serum PSA of 4 ng/ml or lower.

CONCLUSIONS

SELECT is the second large-scale study of chemoprevention for prostate cancer. Enrollment began in 2001 with final results anticipated in 2013.

Cardiovascular risk factors, monitoring, and therapy for HIV-infected patients

Cardiovascular complications are important contributors to morbidity and mortality in HIV-infected patients. These complications can usually be detected at subclinical levels with monitoring, which can help guide targeted interventions. This article reviews available data on types and frequency of cardiovascular manifestations in HIV-infected patients and proposes monitoring strategies aimed at early subclinical detection. In particular, we recommend routine echocardiography for HIV-infected patients, even those with no evidence of cardiovascular disease. We also review preventive and therapeutic cardiovascular interventions. For procedures that have not been studied in HIV-infected patients, we extrapolate from evidence-based guidelines for the general population.

SELECT: the selenium and vitamin E cancer prevention trial

PURPOSE

Growing evidence suggests that both selenium and vitamin E may reduce the risk of prostate cancer. SELECT is a randomized, prospective, double-blind study designed to determine if selenium and vitamin E can reduce the risk of prostate cancer among healthy men.

MATERIALS AND METHODS

The preclinical and epidemiologic evidence regarding chemoprevention with selenium and vitamin E were reviewed. Secondary analyses from randomized trials of both agents were included in the analysis. Data from these analyses as well as evidence from the Prostate Cancer Prevention Trial were used to develop the schema of SELECT.

RESULTS

Preclinical, epidemiologic, and Phase III data suggest that both selenium and vitamin E have potential efficacy in prostate cancer prevention. The experience of the Prostate Cancer Prevention Trial and the rapid accrual of SELECT during its first year demonstrate the interest and dedication of healthy men to long-term studies of cancer prevention. A total of 32,400 men are planned to be randomized in SELECT.

CONCLUSIONS

SELECT is the second large-scale study of chemoprevention for prostate cancer. Enrollment began in 2001 with final results anticipated in 2013.

Selenium as a 'nutraceutical': how to conciliate physiological and supra-nutritional effects for an essential trace element

PURPOSE OF REVIEW

To review how selenium has been appreciated in nutrition and therapeutics for the last few decades.

RECENT FINDINGS

Selenium is a powerful micronutrient constituting the active centre of about 20 eukaryotic proteins highly relevant in biochemistry, mostly for redox state-regulating properties. This element is now better recognized as a biologically important nutrient. Insufficient dietary intake for satisfying biological requirements in several physiological or pathological conditions has been demonstrated, and it is now established that inadequate intake has adverse consequences for disease susceptibility and the maintenance of optimal health. The 'recommended dietary allowances' for selenium actually seem inadequately defined considering not only the recent evolutions of selenium biochemistry, but also the way in which selenium requirements are estimated. Indeed, the element also seems active at supra-nutritional levels of dietary intake, mostly in the field of cancer prevention, and maybe also at pharmacological levels as an adjuvant treatment of some cancers.

SUMMARY

Selenium perfectly illustrates the concept of 'nutraceutical' and the need for changing paradigms in nutrition. Indeed, intakes for satisfying physiological needs as reflected by classical selenium-dependent biochemical functions (mostly glutathione peroxidase activity) only explain a part of selenium biological potency. Other beneficial effects can be obtained at higher nutritional intakes, which in turn implies specified chemical forms and doses. Studies are under way to document these effects in a more complete and convincing manner.

The effect of diet on risk of cancer

Diet-related factors are thought to account for about 30% of cancers in developed countries. Obesity increases the risk of cancers in the oesophagus, colorectum, breast, endometrium, and kidney. Alcohol causes cancers of the oral cavity, pharynx, larynx, oesophagus, and liver, and causes a small increase in the risk of breast cancer. Adequate intakes of fruit and vegetables probably lower the risk for several types of cancer, especially cancers of the gastrointestinal tract. The importance of other factors, including meat, fibre, and vitamins, is not yet clear. Prudent advice is to eat a varied diet including plenty of fruit, vegetables, and cereals to maintain a healthy bodyweight with the help of regular physical activity and to restrict consumption of alcohol.

Molecular mechanisms of cancer prevention by selenium compounds

Selenium compounds that are chemopreventive in animal models inhibit cell growth and induce apoptosis in vitro, and this could explain how they reduce the outgrowth of tumor cells in vivo. Our recent work has shown that primary cultures of oral carcinoma biopsies are significantly more sensitive than normal oral mucosa cultures to induction of apoptosis by a natural selenium metabolite [selenodiglutathione (SDG)], and this is associated with induction of Fas ligand, a well-known mediator of apoptosis in other contexts, and activation of so-called stress kinase signaling pathways, particularly the Jun NH2-terminal kinase (JNK). Heme oxygenase, another marker of stress responses, is also induced by selenite and SDG. The selective activation of the Fas pathway in carcinomas could be responsible directly for their destruction by apoptosis or target them for attack by immunologic responses. In contrast, although the potent pharmacological selenium chemopreventive agent 1,4-phenylenebis(methylene)selenocyanate (p-XSC) also induces Fas ligand, heme oxygenase, and stress kinase pathways, apoptosis/Fas induction is not so strongly JNK-dependent and p-XSC does not show tumor selectivity. These differences in mechanism between SDG and p-XSC may be due to the manner in which they induce redox changes in the cells, since although the effects of SDG and p-XSC are prevented by antioxidants such as glutathione or N-acetylcysteine, hydroxyl radical scavengers such as mannitol or pyrrolidine dithiocarbamate only protect against the effects of p-XSC.

RhCG is downregulated in oesophageal squamous cell carcinomas, but expressed in multiple squamous epithelia

To better understand the molecular events underlying the development of oesophageal cancer, we have isolated the genes dysregulated in primary oesophageal cancer tissues using a modified differential display polymerase chain reaction (DD-PCR). In the present study, a gene designated C15orf6 was identified. The C15orf6 gene, encompassing 25 kb, is composed of 11 exons with a mRNA of 1948 bp. Database searching showed that C15orf6 was 100% homologous to the Rh type C-glycoprotein (RhCG) with the same open reading frame, but 16 bp longer than RhCG at the 5'-end. The gene was highly expressed in human oesophagus, cervix, oral cavity, skin and kidney, but undetectable in the other 14 adult normal tissues examined. Northern blot, RT-PCR and western blot analysis showed that RhCG/C15orf6 was frequently lost or dramatically reduced in primary oesophageal cancer tissues (30/34) compared with the corresponding normal oesophageal mucosa. Three oesophageal-cancer cell lines tested lacked RhCG/C15orf6 expression. Immunohistochemistry revealed that in normal oesophageal tissues, RhCG/C15orf6 was mainly expressed in the plasma membrane of the epithelial cells. In addition, Rh-associated glycoprotein (RhAG) expression was also commonly silenced in both oesophageal cancer cell lines (2/3) and primary oesophageal cancer tissues (11/13). To our knowledge, this is the first time that RhAG expression has been seen in oesophageal epithelium and extends the functional role of the RhAG protein beyond the erythrocyte. These data suggest that inactivation of RhCG/C15orf6 and RhAG occurs frequently during the development of human oesophageal cancer.

Effects of 1,4-phenylenebis(methylene)selenocyanate (p-XSC) and vitamin E on 4-nitroquinoline-N-oxide (4-NQO)-induced mutagenesis in lacZ mouse upper aerodigestive tissue

The effects of dietary administration of 1,4-phenylenebis(methylene)selenocyanate (p-XSC) and Vitamin E on 4-nitroquinoline-N-oxide (4-NQO)-induced mutagenesis in lacZ mouse upper aerodigestive tissues were investigated. 4-NQO was a potent mutagen in tongue, other pooled oral tissues and esophagus when given in drinking water for 4 weeks at a concentration of 20 microg/ml [corrected]. The mutant fractions (MFs) in these tissues were: 144+/-73, 130+/-52 and 61+/-24 mutants/10(5), respectively. Background levels were 3.7+/-1.9 in tongue, 2.9+/-1.2 in esophagus and 2.4+/-1.0 in pooled oral tissue. Vitamin E at levels of 200 and 400 IU/kg diet led to no significant effects on mutagenesis although a small decrease in the MF was observed in all tissues at the higher dose. Dietary p-XSC at levels of 2.5 and 10 ppm selenium also resulted in no statistically significant effects on mutagenesis, but mutagenesis was somewhat reduced in esophagus and pooled oral tissue at the higher dose. However, the combination of the low doses of p-XSC and Vitamin E resulted in nearly a 40% decrease in mutagenesis in tongue and esophagus, and this decrease was statistically significant (P=0.008 and 0.023, respectively. No inhibition was observed using a combination of the higher doses of p-XSC and Vitamin E. These results lend support to the use of low doses of inhibitors of mutagenesis in combinations. The application of in vivo mutagenesis assays to the screening of chemopreventive agents enables investigators to evaluate potential inhibitors when given individually and in combinations on the initiation stage of carcinogenesis in a short-term in vivo bioassay.

Antioxidant and antiproliferative activities of raspberries

Raspberries are rich in phenolic phytochemicals. To study the health benefits of raspberries, four fresh raspberry varieties (Heritage, Kiwigold, Goldie, and Anne) were evaluated for total antioxidant and antiproliferative activities. The total amount of phenolics and flavonoids for each of the four raspberry varieties was determined. The Heritage raspberry variety had the highest total phenolic content (512.7 +/- 4.7 mg/100 g of raspberry) of the varieties measured followed by Kiwigold (451.1 +/- 4.5 mg/100 g of raspberry), Goldie (427.5 +/- 7.5 mg/100 g of raspberry), and Anne (359.2 +/- 3.4 mg/100 g of raspberry). Similarly, the Heritage raspberry variety contained the highest total flavonoids (103.4 +/- 2.0 mg/100 g of raspberry) of the varieties tested, followed by Kiwigold (87.3 +/- 1.8 mg/100 g of raspberry), Goldie (84.2 +/- 1.8 mg/100 g of raspberry), and Anne (63.5 +/- 0.7 mg/100 g of raspberry). The color of the raspberry juice correlated well to the total phenolic, flavonoid, and anthocyanin contents of the raspberry. Heritage had the highest a/b ratio and the darkest colored juice, and the Anne variety showed the lowest phytochemical content and the palest color. Heritage raspberry variety had the highest total antioxidant activity, followed by Kiwigold and Goldie, and the Anne raspberry variety had the lowest antioxidant activity of the varieties tested. The proliferation of HepG(2) human liver cancer cells was significantly inhibited in a dose-dependent manner after exposure to the raspberry extracts. The extract equivalent to 50 mg of Goldie, Heritage, and Kiwigold fruit inhibited the proliferation of those cells by 89.4 +/- 0.1, 88 +/- 0.2, and 87.6 +/- 1.0%, respectively. Anne had the lowest antiproliferative activity of the varieties measured but still exhibited a significant inhibition of 70.3+/- 1.2% with an extract equivalent to 50 mg of fruit. The antioxidant activity of the raspberry was directly related to the total amount of phenolics and flavonoids found in the raspberry (p < 0.01). No relationship was found between antiproliferative activity and the total amount of phenolics/flavonoids found in the same raspberry (p > 0.05).

Triacylglycerols, glycerophospholipids, tocopherols, and tocotrienols in berries and seeds of two subspecies (ssp. sinensis and mongolica) of Sea Buckthorn (Hippophaë rhamnoides)

Berries and seeds of two subspecies (ssp. sinensis and mongolica) of sea buckthorn (Hippophaë rhamnoides L.) were compared in terms of triacylglycerols, glycerophospholipids, tocopherols, and tocotrienols. The berries of ssp. mongolica contained less oleic acid (4.6 vs 20.2%, p < 0.001) and more palmitic (33.9 vs 27.4%, p < 0.01) and palmitoleic (32.8 vs 21.9%, p < 0.05) acids in triacylglycerols than those of ssp. sinensis. The proportions of linoleic acid (32.1 vs 22.2%, p < 0.01, in berries; 47.7 vs 42.7%, p < 0.05, in seeds) and palmitic acid (21.1 vs 16.4%, p < 0.001, in berries; 17.0 vs 14.1%, p < 0.05, in seeds) in glycerolphospholipids were higher in ssp. mongolica than in ssp. sinensis, and vice versa with oleic acid (4.3 vs 18.5% in berries, 10.0 vs 22.2% in seeds, p < 0.001). A higher proportion of alpha-linolenic acid was also found in the glycerophospholipids of ssp. sinensis berries (16.2 vs 10.1%, p < 0.001). alpha-, beta-, gamma-, and delta-tocopherols constituted 93-98% of total tocopherols and tocotrienols in seeds, and alpha-tocopherol alone constituted 76-89% in berries. The total contents of tocopherols and tocotrienols varied within the ranges of 84-318 and 56-140 mg kg(-1) in seeds and whole berries, respectively. The seeds of ssp. mongolica were a better source of tocopherols and tocotrienols than those of ssp. sinensis (287 vs 122 mg kg(-1), p < 0.001). The compositional differences between the two subspecies should be considered when the berries are bred and exploited for nutritional purposes.

Randomised beta-carotene supplementation and incidence of cancer and cardiovascular disease in women: is the association modified by baseline plasma level?

In a nested case-control study of 513 women with cancer; 130 with cardiovascular disease and equal numbers of controls, we found no effect of randomised beta-carotene on risk of cancer or cardiovascular disease within any quartile of baseline plasma beta-carotene, nor was there a trend across quartiles (P for trend 0.15 and 0.62, respectively).

Dietary patterns and adenocarcinoma of the esophagus and distal stomach

BACKGROUND

Dietary pattern analysis is a unique approach to studying relations between diet and disease.

OBJECTIVE

Our objective was to describe the dietary patterns of an eastern Nebraska population and investigate the associations between those dietary patterns and risks of adenocarcinoma of the esophagus and distal stomach.

DESIGN

We recruited 124 subjects with esophageal adenocarcinoma, 124 subjects with distal stomach adenocarcinoma, and 449 control subjects in a population-based, case-control study.

RESULTS

Six dietary patterns were identified with the use of cluster analysis. The first dietary pattern represented healthy food choices and had higher energy contributions from fruit and vegetables and grain products and lower energy contributions from red meats, processed meats, and gravy than did the other dietary patterns. In contrast, a second dietary pattern was high in meats and low in fruit and cereals. The other 4 dietary patterns were each characterized by a concentrated energy source: salty snacks, desserts, milk, and white bread, respectively. The test of overall difference in cancer risk across dietary patterns was significant for distal stomach adenocarcinoma (P = 0.04) but not for esophageal adenocarcinoma. Risk of esophageal adenocarcinoma was inversely associated with intakes of dairy products, fish, all vegetables, citrus fruit and juices, and dark bread and was positively associated with gravy intake. Risk of distal stomach adenocarcinoma was positively associated with red meat intake.

CONCLUSIONS

Our study suggests that a diet high in fruit and vegetables may decrease the risk of esophageal adenocarcinoma and that a diet high in meats may increase the risk of distal stomach adenocarcinoma.

Cardiovascular monitoring and therapy for HIV-infected patients

Cardiovascular complications are important contributors to morbidity and mortality in HIV-infected patients. These complications can usually be detected at subclinical levels with monitoring, which can help guide targeted interventions. This article reviews available data on types and frequency of cardiovascular manifestations in HIV+ patients and proposes monitoring strategies aimed at early subclinical detection. In particular, we recommend routine echocardiography for HIV+ patients, even those with no evidence of cardiovascular disease. We also review preventive and therapeutic cardiovascular interventions. For procedures that have not been studied in HIV+ patients, we extrapolate from evidence-based guidelines for the general population.

SELECT: the next prostate cancer prevention trial. Selenum and Vitamin E Cancer Prevention Trial

PURPOSE

Growing evidence implies that selenium and vitamin E may decrease the risk of prostate cancer. The Selenium and Vitamin E Cancer Prevention Trial (SELECT) is a randomized prospective double-blind study designed to determine whether selenium and vitamin E decrease the risk of prostate cancer in healthy men.

MATERIALS AND METHODS

The preclinical and epidemiological evidence regarding chemoprevention with selenium and vitamin E were reviewed. Secondary analyses from randomized trials of the 2 agents were included in the current analysis. Data from these analyses as well as evidence from the Prostate Cancer Prevention Trial were used to develop the SELECT schema.

RESULTS

Preclinical, epidemiological and phase III data imply that selenium and vitamin E have potential efficacy for prostate cancer prevention. The experience of the Prostate Cancer Prevention Trial shows the interest and dedication of healthy men to long-term studies of cancer prevention. A total of 32,400 men are planned to be randomized in SELECT.

CONCLUSIONS

SELECT is the second large-scale study of chemoprevention for prostate cancer. Enrollment in the study is planned to begin in 2001 with final results anticipated in 2013.

Diet and cancer prevention

Research from several sources provides strong evidence that vegetables, fruits, and whole grains, dietary fibre, certain micronutrients, some fatty acids and physical activity protect against some cancers. In contrast, other factors, such as obesity, alcohol, some fatty acids and food preparation methods may increase risks. Unravelling the multitude of plausible mechanisms for the effects of dietary factors on cancer risk will likely necessitate that nutrition research moves beyond traditional epidemiological and metabolic studies. Nutritional sciences must build on recent advances in molecular biology and genetics to move the discipline from being largely 'observational' to focusing on 'cause and effect'. Such basic research is fundamental to cancer prevention strategies that incorporate effective dietary interventions for target populations.

The protective role of selenium on genetic damage and on cancer

Collectively, results from epidemiologic studies, laboratory bioassays, and human clinical intervention trials clearly support a protective role of selenium against cancer development. Several hypotheses have been proposed to explain these observations. Increased genomic instability, either inherent or induced by exogenous agents (mutagens or carcinogens), has been considered as a primary event leading to neoplastic transformation. This report deals specifically with the evidence for a role of selenium in the inhibition of carcinogen-induced covalent DNA adduct formation and retardation of oxidative damage to DNA, lipids and proteins, and for modulating cellular and molecular events that are critical in cell growth inhibition and in the multi-step carcinogenesis process. At present, the bulk of our knowledge on the role of selenium on genetic stability is based primarily on animal data and from studies conducted in in vitro systems. Studies performed in vitro showed that the dose and form of selenium compounds are critical factors with regard to cellular responses. Inorganic (at doses up to 10microM) and organic selenium compounds (at doses equal to or greater than 10microM) elicit distinctly different cellular responses. The recommended daily allowance (RDA) is 50-70 microgramSe per day for healthy adults; with 40 microgramSe as minimum requirement. Less than 11 microgramSe will definitely put people at risk of deficiency that would be expected to cause genetic damage. Daily doses of 100-200 microgramSe inhibited genetic damage and cancer development in humans. About 400 microgramSe per day is considered an upper limit. Clearly, doses above the RDA are needed to inhibit genetic damage and cancer. However, it has been hypothesized that the intake of excessive doses of selenium may cause oxidative damage, leading to genomic instability. The use of a cocktail consisting of selenium, and other vitamins and minerals appears to be a promising approach to inhibit genetic damage and the development of cancer. It is the author's recommendation that development of mechanism-based hypotheses that can be tested in pilot studies in different populations prior to a large-scale clinical trial in humans, is of paramount importance in order to better understand the role of selenium on genetic stability and cancer.

Retinoic acid receptor-alpha messenger RNA expression is increased and retinoic acid receptor-gamma expression is decreased in Barrett's intestinal metaplasia, dysplasia, adenocarcinoma sequence

BACKGROUND

Expression levels of the retinoic acid receptors (RAR-alpha, RAR-beta, and RAR-gamma) are significantly different in neoplastic tissues compared with non-neoplastic tissues for some tumors. This study investigated whether retinoic acid receptor messenger RNA (mRNA) expression levels are altered in Barrett's esophagus and Barrett's adenocarcinoma tissues.

METHODS

Relative mRNA expression levels of the RARs were quantified by using the ABI 7700 Sequence Detector (Taqman) system in Barrett's intestinal metaplasia (n = 15), dysplasia (n = 6), adenocarcinoma (n = 17), and matching normal esophagus tissues (n = 36).

RESULTS

RAR-alpha expression was significantly increased, and RAR-gamma expression was significantly decreased, at higher stages in the Barrett's sequence. There was almost complete loss of RAR-gamma expression (relative expression level < or = 1) in a majority (70%) of the dysplasia and adenocarcinoma tissues. There were significant differences in RAR-alpha and RAR-gamma expression in histopathologically normal tissues in patients with cancer versus patients without cancer. RAR-beta expression levels were significantly elevated in adenocarcinoma versus normal esophagus tissues. The RAR expression profile was similar for cancers arising within the esophagus and for cancers arising at the gastroesophageal junction.

CONCLUSIONS

RAR mRNA expression levels are significantly different in Barrett's tissues compared with normal esophagus tissues, and these levels are significantly different in Barrett's dysplasia and adenocarcinoma tissues compared with nondysplastic tissues. These results suggest that RAR mRNA levels may be useful biomarkers for this disease and that gastroesophageal junction adenocarcinomas are genetically similar to esophageal adenocarcinomas. These results also suggest that a cancer field is present in the esophagus in patients with cancer and that genetic alterations can precede histopathologic alterations in this disease.

An analysis of cancer prevention by selenium

The nutritional functions of selenium (Se) are recognized as being due to a number of Se-containing proteins. It is not clear, however, whether any of these function in the anti-tumorigenic effects of Se most of which have been demonstrated for Se exposures greater than those required for selenoprotein expression. Indeed, other anti-tumorigenic mechanisms have been demonstrated for certain Se-metabolites. The Nutritional Prevention of Cancer Trial found supplemental Se (200 microg/day, as Se-enriched yeast) to be associated with significant reductions in cancer risks in subjects with pre-treatment plasma Se concentrations below ca. 120 ng/ml (1.5 nmoles/ml), which level would appear to require food-Se intakes of ca. 1.5 microg/kg body weight/day. However, the putative anti-carcinogenic Se-metabolite(s) should be more relevant than total plasma Se as a supplementation target for cancer prevention. These may be components of the non-protein-bound fraction of Se in plasma, which constitutes 2-4% of total plasma Se.

Novel human esophagus-specific gene c1orf10: cDNA cloning, gene structure, and frequent loss of expression in esophageal cancer

We have identified a novel human gene, designated C1orf10, using modified differential display PCR. The C1orf10 gene, which spans 5 kb in length, is composed of three exons. The deduced protein contains 495 amino acids with one transmembrane domain. The amino acid sequence of C1orf10 is characterized by the presence of a calcium-binding motif of about 90 amino acids at its N-terminal and a conserved consecutive repeat sequence of 60 amino acids that was identified previously only in bacterial ice nucleation proteins. In normal adult tissues, C1orf10 is highly expressed only in the esophagus and was undetectable in a total of 15 other tissues examined, suggesting its important role in esophageal cells. The expression of C1orf10 is either dramatically reduced or absent in esophageal cancer cell lines (3/3) as well as primary esophageal cancer tissues (35/37) compared with the corresponding normal esophageal mucosa. Using a radiation hybrid panel, C1orf10 was found to be located on chromosome 1q21. These findings suggest that expression of C1orf10 is unique to esophageal cells and that loss of its expression may play a role in the development of esophageal cancer.

Supercritical CO(2) extraction of beta-carotene and lycopene from tomato paste waste

Lycopene and beta-carotene were extracted from tomato paste waste using supercritical carbon dioxide (SC-CO(2)). To optimize supercritical fluid extraction (SFE) results for the isolation of lycopene and beta-carotene, a factorial designed experiment was conducted. The factors assessed were the temperature of the extractor (35, 45, 55, and 65 degrees C), the pressure of the extraction fluid (200, 250, and 300 bar), addition of cosolvent (5, 10, and 15% ethanol), extraction time (1, 2, and 3 h), and CO(2) flow rate (2, 4, and 8 kg/h). The total amounts of lycopene and beta-carotene in the tomato paste waste, extracts, and residues were determined by HPLC. A maximum of 53.93% of lycopene was extracted by SC-CO(2) in 2 h (CO(2) flow rate = 4 kg/h) at 55 degrees C and 300 bar, with the addition of 5% ethanol as a cosolvent. Half of the initially present beta-carotene was extracted in 2 h (flow rate = 4 kg/h), at 65 degrees C and 300 bar, also with the addition of 5% ethanol.

Primary cancer prevention trials

Great progress has been made in cancer chemoprevention during the past 2 decades. Nevertheless, the field could benefit from the experiences of investigators studying the prevention of cardiovascular disease. During the past 50 years, prevention of cardiovascular disease has gone from a dream to a reality, with major clinical impact. The trend during the last 30 years has been impressive and sustained. From 1987 to 1994, there was a sustained major decrease in age-adjusted mortality from coronary heart disease in both men (from 3.1 to 2.2 per thousand persons) and women (from 1.1 to 0.9 per thousand persons). This trend is believed to have resulted from improvements in the treatment of myocardial infarction and, more substantively, from improvements in secondary prevention. This explanation is consistent with earlier computer simulations of trends in cardiovascular mortality during the 1980s, which estimated that 25% of the declines were attributable to primary prevention and 70% were caused by reductions in risk factors or treatment. The greatest effect of primary prevention had previously been noted in the late 1960s and 1970s. Most of these important findings occurred before cholesterol-lowering drugs became widely available, so further improvements are expected. Researchers in cancer prevention should follow in the footsteps of their cardiovascular colleagues. The tools are now available to make prevention of cancer a clinical reality. As the science of prevention improves, it must be remembered that effective and efficient preventive services do not help if they are not used. It is difficult to motivate practitioners and patients to implement preventive services. Also, preventive services are often considered a luxury. Persons without health insurance and those covered by Medicaid are much more likely to be diagnosed with late-stage cancer; therefore, they are key cohorts to target for effective preventive approaches. Finally, the most effective cancer prevention program will probably use both rational drug therapy targeting specific risk factors and public health efforts to promote healthy lifestyle choices in the population at large.

Lack of correlation between expression of retinoic acid receptor-beta and loss of heterozygosity on chromosome band 3p24 in esophageal cancer

Loss of heterozygosity (LOH) on chromosome arm 3p occurs frequently in human cancers, including esophageal cancer, suggesting that tumor suppressor genes may be located on this chromosome arm. The retinoic acid receptor-beta (RARB) gene is localized on chromosome band 3p24, and its expression is progressively lost during esophageal carcinogenesis. Furthermore, growth inhibition of esophageal cancer cell lines by all-trans retinoic acid has been associated with the constitutive and induced expression of RARB. We therefore assessed LOH on chromosome arm 3p and RARB expression in esophageal cancer to investigate the mechanism of altered RARB expression during carcinogenesis. We first analyzed LOH in 65 paired surgical specimens of normal mucosa and esophageal cancer by using 10 microsatellite markers, which resulted in 44 informative cases for subsequent study. LOH on chromosome band 3p24 was found to occur at an overall rate of 36.4% (16/44) by three markers (D3S1293, THRB, and D3S1283). LOH for these three individual markers was 14.0%, 47.4%, and 20.9%, respectively. Meanwhile, RARB expression was lost in 43.2% (19/44) of these 44 samples. The loss of RARB expression was not correlated with LOH on chromosome band 3p24 (gamma = -0.22, -0.069, and -0.02, P = 0.15, 0.78, and 0.9 for D3S1293, THRB, and D3S1283, respectively), although both altered RARB expression and LOH in esophageal cancer were statistically significant (P = 0.001 and 0.0001, respectively), indicating that the loss of RARB expression cannot be explained by LOH on 3p24.

Update from Asia. Asian studies on cancer chemoprevention

In Asia, nontoxic dietary products are considered desirable primary prevention vehicles for conquering cancer. As early as 1978, investigators in Korea carried out extensive long-term anticarcinogenicity experiments using the mouse lung tumor model and observed an anticarcinogenic effect of Panax ginseng C.A. Meyer extract in 1980. The results showed that natural products can provide hope for human cancer prevention. A newly established nine-week medium-term model using mouse lung tumors (Yun's model) could confirm the anticarcinogenicity of ginseng that varies according to its type and age. Subsequently, the ginseng was shown by epidemiological studies to be a nonorgan-specific cancer preventive agent associated with a dose-response relationship. The anticarcinogenic effects of vegetarian foods common at every dining table in Korea and some synthetics were also studied using Yun's nine-week model. In brief, ascorbic acid, soybean lecithin, capsaicin, biochanin A, Ganoderma lucidum, caffeine, and a novel synthetic 2-(allylthio)pyrazine decrease the incidence of mouse lung tumors, whereas fresh ginseng (4 years old), carrot, spinach, Sesamum indicum, beta-carotene, and 13-cis retinoic acid do not. This result regarding beta-carotene is consistent with the ineffective findings of the ATBC trial, the CARET trial, and the Physicians' Health Study. In 1983, a cancer chemoprevention study group was first established in Japan. Subsequently, (-)-epigallocatechin gallate, cryptoporic acid E, and sarcophytol A from natural products, and synthetic acyclic retinoid and canventol were shown to be anticarcinogenic or chemopreventive in human subjects. Despite the frequent consumption of tea wordwide as a beverage and current experimental evidence of anticarcinogenesis, including controversial results of epidemiological studies, more systematic clinical trials for confirmation of preventive activity of tea against cancer are needed. Placebo-controlled intervention trials of dietary fiber are under study in Japan. In the past decade, new triterpenoids were isolated from various natural sources, and its biological activities were investigated in Asia. In the late 1970s a comprehensive chemoprevention program was established at the Institute of Materia Medica, Chinese Academy of Medical Sciences. Since then, many retinoid compounds have been synthesized and screened in the search for chemopreventive cancer agents. The National Cancer Institute (USA) and China are jointly engaged in the two-nutrition intervention in Linxian, China. The results of joint study of the general population and of dysplasia in China should stimulate further research to clarify the potential benefits of micronutrient supplements. We need to clarify if there is a connection between the lower rates of cancer mortality in Korea and the frequent consumption of anticarcinogenic vegetables or traditional foods, including ginseng and Ganoderma lucidum. The constituents of the nontoxic stable dietary products promise to be the future hope for conquering cancers in the coming years.

[High temperature "matè" infusion drinking in a population at risk for squamous cell carcinoma of the esophagus]

"Matè", a popular hot infusion of a herb (Ilex paraguayensis) drunk in large volumes, is a known risk factor for squamous cell carcinoma of the esophagus and there is a suspicion that high temperature of boiled water used for the infusion may contribute for carcinogenesis.

METHODS

We measured the temperature of "matè" infusion drunk by a sample of the population at risk for this carcinoma in Taquara, southern Brazil. We interviewed inhabitants for drinking habits and the temperature of the infusion was measured with high precision thermometers. Temperature of the infusion was asked to consumers and their estimate compared to our measurements. We considered 60 degrees C or higher as "hot".

RESULTS

In 36 residencies, 107 individuals were drinking "matè". Most individuals drank it daily (97.2%), and the medium daily volume was 1,265 ml (SD +/- 1,132 mL) ranging from 250 to 6,000 mL. The measured temperature was 60 degrees C or higher in 72% of residencies with medium of 63.4 degrees C (51-78 degrees C) and median 64.4 degrees C.

CONCLUSION

In this study, "matè" was consumed in large volumes at high temperature and individuals did not estimate correctly the temperature of infusion. High temperatures of "matè" may contribute to carcinogenesis in this population.

Beta-carotene supplementation and incidence of cancer and cardiovascular disease: the Women's Health Study

BACKGROUND

In observational studies, individuals with high intakes of fruits and vegetables containing beta-carotene experience lower risks of developing cancer. However, the few randomized trials of beta-carotene supplementation show no overall benefits; some even suggest harm. This trial was designed to test the effects of beta-carotene supplementation in women.

METHODS

The Women's Health Study is a randomized, double-blind, placebo-controlled trial originally testing aspirin, vitamin E, and beta-carotene in the prevention of cancer and cardiovascular disease among 39 876 women aged 45 years or older. The beta-carotene component was terminated early after a median treatment duration of 2.1 years (range = 0.00-2. 72 years). Statistical tests were two-sided.

RESULTS

Among women randomly assigned to receive beta-carotene (50 mg on alternate days; n = 19 939) or placebo (n =19 937), there were no statistically significant differences in incidence of cancer, cardiovascular disease, or total mortality after a median of 4.1 years (2.1 years' treatment plus another 2.0 years' follow-up). There were 378 cancers in the beta-carotene group and 369 cancers in the placebo group (relative risk [RR] = 1.03; 95% confidence interval [CI] = 0.89-1. 18). There were no statistically significant differences for any site-specific cancer or during years 1 and 2 combined and years 3 and up combined. For cardiovascular disease, there were no statistically significant differences for myocardial infarction (42 in the beta-carotene group versus 50 in the placebo group), stroke (61 versus 43), deaths from cardiovascular causes (14 versus 12), or the combined end point of these three events (116 versus 102; among women with more than one event, only the first was counted). Deaths from any cause were similar in the two groups (59 versus 55). Among smokers at baseline (13% of all women), there were no statistically significant differences in overall incidence of cancer (RR = 1.11; 95% CI = 0.78-1.58) or cardiovascular disease (RR = 1.01; 95% CI = 0. 62-1.63).

CONCLUSION

Among apparently healthy women, there was no benefit or harm from beta-carotene supplementation for a limited period on the incidence of cancer and of cardiovascular disease.