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The Biomarkers of Nutrition for Development (BOND) project is designed to provide evidence-informed advice to anyone with an interest in the role of nutrition in health. The BOND program provides information with regard to selection, use, and interpretation of biomarkers of nutrient exposure, status, function, and effect, which will be especially useful for readers who want to assess nutrient status. To accomplish this objective, expert panels are recruited to evaluate the literature and to draft comprehensive reports on the current state of the art with regard to specific nutrient biology and available biomarkers for assessing nutritional status at the individual and population levels. Phase I of the BOND project includes the evaluation of biomarkers for 6 nutrients: iodine, folate, zinc, iron, vitamin A, and vitamin B-12. This review of vitamin A is the current article in this series. Although the vitamin was discovered >100 y ago, vitamin A status assessment is not trivial. Serum retinol concentrations are under homeostatic control due in part to vitamin A's use in the body for growth and cellular differentiation and because of its toxic properties at high concentrations. Furthermore, serum retinol concentrations are depressed during infection and inflammation because retinol-binding protein (RBP) is a negative acute-phase reactant, which makes status assessment challenging. Thus, this review describes the clinical and functional indicators related to eye health and biochemical biomarkers of vitamin A status (i.e., serum retinol, RBP, breast-milk retinol, dose-response tests, isotope dilution methodology, and serum retinyl esters). These biomarkers are then related to liver vitamin A concentrations, which are usually considered the gold standard for vitamin A status. With regard to biomarkers, future research questions and gaps in our current understanding as well as limitations of the methods are described.

Total antioxidant performance (TAP) measures antioxidant capacities in both hydrophilic and lipophilic compartments of serum and interactions known to exist between them. Our objective was to assess TAP levels in a subset of Jackson Heart Study (JHS) participants and to examine associations with dietary and total (diet + supplement) intakes of [alpha]-tocopherol, [gamma]-tocopherol (diet only), [beta]-carotene, vitamin C, fruit, vegetables, and nuts, and serum concentrations of [alpha]-tocopherol, [gamma]-tocopherol, and [beta]-carotene. We conducted a cross-sectional analysis of 420 (mean age 61 y; 254 women) African American men and women participating in the Diet and Physical Activity Sub-Study of the JHS in Jackson, Mississippi. In multivariate-adjusted models, we observed positive associations between total [alpha]-tocopherol, total and dietary [beta]-carotene, and total vitamin C intakes and TAP levels (P-trend < 0.05). Positive associations were also observed for vegetable, fruit, and total fruit and vegetable intakes (P-trend < 0.05). For serum antioxidant nutrients, [alpha]-tocopherol but not [beta]-carotene was associated with serum TAP levels. There were inverse associations for serum [gamma]-tocopherol and TAP levels. Associations for [alpha]-tocopherol were seen at intake levels much higher than the current Recommended Dietary Allowance. It may, therefore, be prudent to focus on increasing consumption of fruit, vegetables, nuts, and seeds to increase total antioxidant capacity.

Hepatocyte apoptosis in addition to oxidative stress could be a key component in the pathogenesis of nonalcoholic steatohepatitis (NASH). However, the underlying mechanisms of hepatocellular apoptotic response associated with oxidative stress have not been investigated in high-fat diet (HFD)--induced NASH models. In this study, Sprague-Dawley rats were fed either a Lieber-DeCarli control diet (CD; 35% energy from fat) or a HFD (71% energy from fat) for 6 wk. Pathologic lesions, lipid peroxidation products, and apoptotic hepatocytes in the liver were examined. The expressions of hepatic tumor necrosis factor-[alpha] (TNF[alpha]) and protein concentrations of cleaved caspase-3, cytochrome p4502E1 (CYP2E1), phosphorylated c-Jun [NH.sub.2]-terminal kinase (JNK), Bax, Bcl-2, and Bcl-xl were measured. Results showed that the key histological features of NASH, including steatosis, inflammatory cell infiltration, and ballooning degeneration of hepatocytes, were induced by HFD feeding, with increased hepatic TNF[alpha] mRNA expression. HFD-fed rats had elevated lipid peroxidation products and CYP2E1 protein in the liven The apoptotic hepatocytes were significantly greater in livers of rats fed HFD than in those fed CD, and these were associated with a higher level of cleaved caspase-3. In addition, HFD feeding increased both hepatic phosphorylated JNK and pro-apoptotic Bax but did not affect anti-apoptotic Bcl-2 and Bcl-xl compared with CD feeding. These data indicate that the increased oxidative stress and its associated JNK activation as well as an imbalance of pro- and anti-apoptotic proteins in the Bcl-2 family all contribute to high hepatocyte apoptosis that may play an important role in the pathogenesis of NASH in this model.

Recent in vitro evidence suggests that the antioxidant lycopene can prevent alcohol-induced oxidative stress and inflammation. However, knowledge of possible interactions in vivo between escalating doses of lycopene and chronic alcohol ingestion are lacking. In this study, we investigated potential interactions between alcohol ingestion and lycopene supplementation and their effect on hepatic lycopene concentration, cytochrome P4502E1 (CYP2E1) induction, and inflammation. Fischer 344 rats (6 groups, n = 10 per group) were fed either a liquid ethanol Lieber-DeCarli diet or a control diet (isocaloric maltodextrin substituted for ethanol) with or without lycopene supplementation at 2 doses (1.1 or 3.3 mg.kg body [weight.sup.-1] x [d.sup.-1]) for 11 wk. Plasma and hepatic concentrations of lycopene isomers were assessed by HPLC analysis. We examined expressions of hepatic CYP2E1 and tumor necrosis factor-[alpha] (TNF[alpha]) and the incidence of hepatic inflammatory foci. Both plasma and hepatic lycopene concentrations were greater in alcohol-fed rats than in control rats supplemented with identical doses of lycopene. In contrast, alcohol-fed rats had a lower percentage of lycopene cis isomers in the plasma and the liver compared with control rats fed the same dose of lycopene. Notably, lycopene supplementation at the higher dose significantly induced hepatic CYP2E1 protein, TNF[alpha] mRNA, and the incidence of inflammatory foci in the alcohol-fed rats but not in the control rats. These data indicate n interaction between chronic alcohol ingestion and lycopene supplementation and suggest a need for caution among individuals consuming high amounts of both alcohol and lycopene.

Data from epidemiologic, experimental, and animal studies indicate that diet plays an important role in the etiology of gastric cancer. High intake of fresh fruits and vegetables, lycopene and lycopene-containing food products, and potentially vitamin C and selenium may reduce the risk for gastric cancer. Data also suggest that high intake of nitrosamines, processed meat products, salt and salted foods, and overweight and obesity are associated with increased risk for gastric cancer. However, current data provide little support for an association of [beta]-carotene, vitamin E, and alcohol consumption with risk for gastric cancer.

Vitamin A (VA) kinetics, storage, and disposal rate were determined in well-nourished Chinese and U.S. adults using model-based compartmental analysis. [[sup.2][H.sub.8]]Retinyl acetate (8.9 [micro]mol) was orally administered to U.S. (n = 12; 69 [+ or -] 9 y; mean [+ or -] SD) and Chinese adults (n = 14; 64 [+ or -] 4 y) and serum tracer and VA concentrations were measured from 3 h to 56 d. Using the Windows version of the Simulation, Analysis and Modeling software, we determined that the average time from dosing until appearance of labeled retinol in serum was greater in U.S. subjects (40.6 [+ or -] 8.47 h) than in Chinese subjects (32.2 [+ or -] 5.84 h; P < 0.01). Model-predicted total traced mass (898 [+ or -] 637 vs. 237 [+ or -] 109 [micro]mol), disposal rate (14.7 [+ or -] 5.87 vs. 5.58 [+ or -] 2.04[micro]mol/d), and system residence time (58.9 [+ or -] 28.7 vs. 42.9 [+ or -] 14.6 d) were greater in U.S. than in Chinese subjects (P < 0.05). The model-predicted VA mass and VA mass estimated by deuterated retinol dilution at 3 and 24 d did not differ. VA disposal rate was positively correlated with VA traced mass in Chinese ([R.sup.2] = 0.556), U.S. ([R.sup.2] = 0.579), and all subjects ([R.sup.2] = 0.808). Additionally, VA disposal rate was significantly correlated with serum retinol pool size ([R.sup.2] = 0.227) and retinol concentration ([R.sup.2] = 0.330) in all subjects. Our results support the hypothesis that VA stores are the principle determinant of VA disposal rate in healthy, well-nourished adults.

In 1999 we proposed a Modified Food Guide Pyramid for adults aged 70+ y. It has been extensively used in a variety of settings and formats to highlight the unique dietary challenges of older adults. We now propose a Modified MyPyramid for Older Adults in a format consistent with the MyPyramidgraphic. It is not intended to substitute for MyPyramid, which is a multifunctional Internet-based program allowing for the calculation of individualized food-based dietary guidance and providing supplemental information on food choices and preparation. Pedagogic issues related to computer availability, Web access, and Internet literacy of older adults suggests a graphic version of MyPyramid is needed. Emphasized are whole grains and variety within the grains group; variety and nutrient density, with specific emphasis on different forms particularly suited to older adults' needs (e.g. frozen) in the vegetables and fruits groups; low-fat and non-fat forms of dairy products including reduced lactose alternatives in the milk group; low saturated fat and trans fat choices in the oils group; and low saturated fat and vegetable choices in the meat and beans group. UnderLying themes stress nutrient- and fiber-rich foods within each group and food sources of nutrients rather than supplements. Fluid and physical activity icons serve as the foundation of MyPyramid for Older Adults. A flag to maintain an awareness of the potential need to consider supplemental forms of calcium, and vitamins D and B-12 is placed at the top of the pyramid. Discussed are newer concerns about potential overnutrition in the current food landscape available to older adults.

Cigarette smoking increases the risk for gastric cancer. Higher intakes or blood levels of lycopene are associated with a decreased risk of gastric cancer. However, the biological mechanisms by which lycopene may protect against gastric carcinogenesis are poorly understood. We evaluated the effects of lycopene supplementation on smoke-induced changes in protein levels of p53, p53 target genes ([p21.sup.Waf1/Cip1] and Bax-1), cell proliferation, and apoptosis in the gastric mucosa of ferrets. Ferrets were assigned to cigarette smoke exposure or to no exposure and to no, low-dose, or high-dose lycopene supplementation (2 x 3 factorial design) for 9 wk. Lycopene concentrations were significantly elevated in a dose-dependent manner in the gastric mucosa of ferrets supplemented with lycopene alone, but were markedly reduced in ferrets supplemented with lycopene and exposed to smoke. Although ferrets were given lycopene containing 95% all-trans isomers, cis isomers were the predominant forms in the gastric mucosa. Total p53 and phosphorylated p53 levels were greater in ferrets exposed to smoke alone than in all other groups. Levels were ~300 and 500% of the controls, respectively. However, smoke-elevated total p53 and phosphorylated p53 were markedly attenuated by both doses of lycopene. [p21.sup.Waf1/Cip1] Bax-1, and cleaved caspase 3 were substantially decreased, whereas cyclin D1 and proliferating cellular nuclear antigen (PCNA) were increased in ferrets exposed to smoke alone. Lycopene prevented smoke-induced changes in [p21.sup.Waf1/Cip1], Bax-1, cleaved caspase 3, cyclin D1, and PCNA in a dose-dependent fashion. These data indicate that lycopene may prevent smoke exposure-induced changes in p53, p53 phosphorylation, p53 target genes, cell proliferation, and apoptosis in the gastric mucosa of ferrets. KEY WORDS: * lycopene * smoke * cell profiferation * apoptosis * ferrets

The consumption of adequate levels and proper balance of essential nutrients is critical for maintaining health. Despite tremendous studies in the area of nutrition and positive health, the implications on public health behavior of shifting the emphasis away from food towards nutrient supplements are unknown.

Chronic and excessive ethanol intake in rats results in low levels of hepatic retinoic acid (RA) either by inhibiting the biosynthesis of RA or by enhancing its catabolism of RA. Chronic ethanol intake also decreases both hepatic expression of insulin-like growth factor-I (IGF-I) and plasma IGF-I concentration in rats. It is not known whether RA supplementation in alcohol-fed rats can restore plasma IGF-I concentrations and hepatic IGF-I expression. In the present study, we examined both plasma IGF-I level and hepatic IGF-I mRNA expression in alcohol-fed rats with or without RA (100 [micro]g/kg body weight) supplementation for 6 mo. Hepatic IGF-I mRNA levels and plasma IGF-I concentration were decreased (84 and 29%, respectively) significantly in alcohol-fed rats compared with the control. In contrast, RA supplementation in ethanol-fed rats partially restored both hepatic IGF-I mRNA levels and plasma IGF-I concentration compared with rats fed ethanol alone. These data suggest that alcohol-impaired hepatic RA status contributes to the decreased plasma IGF-I level and hepatic IGF-I expression in alcoholics. J. Nutr. 134: 2953-2956, 2004. KEY WORDS: * retinoic acid * alcohol * IGF-I

We demonstrated previously that smoke exposure and/or high-dose [beta]-carotene supplementation decreases levels of retinoic acid and retinoic acid receptor [beta] (RAR[beta]) protein, but increase levels of c-Jun and proliferating cellular nuclear antigen protein in the lungs of ferrets. In contrast, low-dose [beta]-carotene can prevent the decreased lung retinoic acid and the smoke-induced lung lesions. In the present study, we investigated whether smoke exposure and/or [beta]-carotene supplementation could affect Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), and p53 in the lungs of ferrets. Ferrets were subjected to cigarette smoke exposure and either a high or low dose of [beta]-carotene (2 x 3 factorial design) for 6 mo. There were greater protein levels of phosphorylated JNK, p38, and c-Jun, but lower levels of MAPK phophatase-1 (MKP-1) in groups exposed to smoke and/or high dose [beta]-carotene. Both phosphorylated-p53 and total p53 were substantially increased in the lungs of these groups. In contrast, low-dose [beta]-carotene greatly attenuated the smoke-induced phosphorylation of JNK, p38, c-Jun, p53, and total p53, accompanied by upregulated MKP-1. Smoke exposure increased MAPK kinase-4 (MKK4) phosphorylation regardless of [beta]-carotene supplementation. These data indicate that restoration of retinoic acid and MKP-1 by low-dose [beta]-carotene in the lungs of ferrets may prevent the smoke-induced activation of the JNK-dependent signaling pathway, p38 MAPK, and the associated phosphorylation of p53, thereby lowering the risk of the smoke-related lung lesions. These data provide supportive evidence that the beneficial vs. detrimental effects of [beta]-carotene supplementation are related to the dosage of [beta]-carotene administered. KEY WORDS: * [beta]-carotene * smoke * signal transduction pathway

Low-dose [beta]-carotene (BC) supplementation, such as would be provided by daily consumption of ~5-9 servings of fruits and vegetables, has no apparent detrimental effects, but rather appears to have a protective effect against cigarette smoke-induced lung lesions in ferrets. In the present study, we investigated the effects of BC, [beta]-apo-14'-carotenoic acid (14'CA), or benzo[a]pyrene (BP; a primary lung carcinogen from cigarette smoke) treatments, either alone or in combination, on cell growth and expression of the retinoic acid receptor (RAR) of normal human bronchial epithelial (NHBE) cells. We found that both BC and 14'CA inhibited the growth of NHBE cells (P < 0.05) with or without BP. The level of RAR[beta], a tumor suppressor, but not RAR[beta] or RAR[gamma] was reduced by 50% in the NHBE cells treated with BP. However, treatment with either BC or 14'CA significantly induced the expression of RAR[beta] in the NHBE cells, and prevented the reduction of RAR[beta] by BP. Furthermore, 14'CA transactivated the RAR[beta] promoter primarily via its conversion to retinoic acid (RA). In the presence of 3-mercaptopropionic acid, an inhibitor of fatty acid oxidation, both RA formation and transactivation activity from 14'CA were decreased. These observations indicate that the growth inhibitory effects of BC and [beta]-apo-carotenoic acid are through their conversion to RA and upregulation of RAR[beta]. KEY WORDS: * [beta]-carotene * [beta]-apo-carotenoids * retinoic acid receptor * lung cancer

Previously, we found that exposing ferrets to cigarette smoke enhanced oxidative excentric cleavage of [beta]-carotene. In the present study, we examined whether [alpha]-tocopherol, ascorbic acid, or the two combined can prevent smoke-altered [beta]-carotene metabolism. In vitro incubation of [beta]-carotene (10 [micro]mol/L) with lung postnuclear fractions from ferrets exposed to cigarette smoke was carried out in the absence or presence of [alpha]-tocopherol (50 [micro]mol/L), ascorbic acid (10 or 50 [micro]mol/L), or both vitamins to evaluate their effects on the production of [beta]-apo-carotenals and retinoids from [beta]-carotene. The oxidative cleavage metabolites of [beta]-carotene, [beta]-apo-carotenals ([beta]-apo-14', [beta]-apo-12', [beta]-apo-10', and [beta]-apo-8'), retinoic acid (RA), and retinal were analyzed by HPLC. We found that the smoke-enhanced production of individual [beta]-apo-carotenals was significantly decreased by 36-77% when [alpha]-tocopherol (50 [micro]mol/L) and ascorbic acid (50 [micro]mol/L) were added together to the incubation mixture, [alpha]-Tocopherol alone had a modest effect. Ascorbic acid in the presence of [alpha]-tocopherol inhibited the production of [beta]-apo-carotenals in a dose-dependent manner, although ascorbic acid alone had no effect. In contrast, the production of RA and retinal among smoke-exposed ferrets was substantially increased (~3-fold, P < 0.05) when both [alpha]-tocopherol and ascorbic acid were added to the incubation mixtures. However, when ascorbic acid or [alpha]-tocopherol alone was added, the production of RA among smoke-exposed ferrets increased only modestly (80%, P < 0.05) and did not differ from the RA levels in control ferrets. In conclusion, these data indicate that [alpha]-tocopherol and ascorbic acid may act synergistically in preventing the enhanced oxidative excentric cleavage of [beta]-carotene induced by smoking exposure, thereby facilitating the conversion of [beta]-carotene into RA and retinal. KEY WORDS: * carotenoids * retinoids * [alpha]-tocopherol * ascorbic acid * cigarette smoke

[beta]-carotene and other carotenoids have been thought to have anti-cancer activity, either because of antioxidant activity or because of their ability to be converted to vitamin A. Nevertheless, two large scale intervention studies in humans using high doses of [beta]-carotene found that [beta]-carotene supplementation resulted in more lung cancer rather than less lung cancer among smoking and asbestos exposed populations. Studies conducted in the ferret have elucidated molecular mechanisms behind this observation, in that high-dose [beta]-carotene and smoke exposure in these animals leads to squamous metaplasia, a pre-cancerous lesion in the lung. High dose [beta]-carotene in the smoke exposed animals was found to give rise to a number of transient oxidative metabolites, which include P450 enzymes that result in the destruction of retinoic acid, and diminished retinoid signaling, and enhanced cell proliferation. In addition, eccentric cleavage [beta]-carotene metabolites facilitate the binding of smoke derived carcinogens to DNA. In other ferret studies low dose [beta]-carotene smoke exposure provided mild protection against squamous metaplasia. Thus, it appears that the explanation of the apparent paradoxical effects of [beta]-carotene on lung cancer is related to dose. The metabolism and breakdown of natural products should be thoroughly investigated in animal models before embarking on large scale intervention trials, particularly when using unusually high doses that greatly exceed normal dietary levels. KEY WORDS: * [beta]-carotene * carotenoids * vitamin A * retinoids * lung cancer * smoking

The oxidation of endogenous antioxidant nutrients in human plasma was determined to examine their activities against free radicals generated in the aqueous and lipid compartments of plasma. Free radicals were induced at a constant rate in the aqueous compartment by the hydrophilic radical generator, 2,2'-azobis-(2-amidinopropane) dihydrochloride (AAPH; 10-20 mmol/L) and in the lipid compartment by the lipophilic radical generator, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) (MeO-AMVN; 1-2 mmol/L). The depletion of endogenous plasma antioxidant nutrients (lutein, cryptoxanthin, [beta]-carotene, lycopene, [alpha]-tocopherol, ascorbic acid, uric acid) was determined after incubation with either AAPH or MeO-AMVN at 37[degrees]C using HPLC. The oxidation of the aqueous and lipid compartments of plasma was selectively monitored by a fluorimetric method using either the hydrophilic probe, 2',7'-dichlorodihydrofluorescein (DCFH) or the lipophilic probe, 4,4-difluoro-5-(4-phenyl-1,3-butadienyl) -4-bora-3a,4a-diazas-indacene-3-undecanoic acid (BODIPY 581/591). When plasma was incubated with AAPH, the rates of consumption of the antioxidant nutrients were as follows: ascorbic acid > [alpha]-tocopherol > uric acid > lycopene > lutein > cryptoxanthin > [beta]-carotene. When plasma was incubated with MeO-AMVN, [alpha]-tocopherol and carotenoids were depleted at similar rates anal ahead of the major water-soluble antioxidants. Our study indicates that the antioxidant nutrients present in both the lipid and aqueous compartments can remove free radicals generated in plasma, and their activity depends on the localization of the attacking radical species. KEY WORDS: * carotenoids * ascorbic acid * [alpha]-tocopherol * oxidizability * azo-initiator

In our previous studies, we found lower levels of retinoic acid (RA) in the lungs of ferrets exposed to cigarette smoke and/or a pharmacological dose of [beta]-carotene. To determine whether this is involved in excessive catabolism of RA via cytochrome P450 (CYP) induction, we carried out in vitro incubations of RA with the lung microsomal fractions of ferrets with or without CYP inhibitors and antibodies against CYP. The polar metabolites (4-oxo-RA and 18-hydroxy-RA) of RA metabolism after the incubation were analyzed by HPLC. Expressions of CYP (1A1, 1A2, 2E1 and 3A1) were examined using Western blot analysis. Incubation of various concentrations of RA with the lung microsomal fraction from ferrets exposed to cigarette smoke, a pharmacological dose of [beta]-carotene or their combination dose-dependently increased the levels of 4-oxo-RA and 18-hydroxy-RA compared with that of the control ferrets. At all RA concentrations, this increase was the greatest in lung tissue from the combined treatment group. Furthermore, this enhanced RA catabolism was substantially (~80%) inhibited by nonspecific CYP inhibitors (disulfiram and liarozole), but was partially (~50%) inhibited by resveratrol (CYP1A1 inhibitor), [alpha]-naphthoflavone (CYP1A2 inhibitor) and antibodies against CYP1A1 and CYP1A2. Cigarette smoke exposure and/or pharmacological doses of [beta]-carotene increased levels of CYP1A1 and 1A2 by three- to sixfold but not levels of 2E1 and 3A1 in ferret lung tissue. These findings suggest that low levels of RA in the lung of ferrets exposed to cigarette smoke and/or pharmacological doses of [beta]-carotene may be caused by the enhanced RA catabolism via induction of CYP, CYP1A1 and CYP1A2 in particular, which provides a possible explanation for enhanced lung carcinogenesis seen with pharmacological doses of [beta]-carotene supplementation in cigarette smokers. KEY WORDS: * cigarette smoke * [beta]-carotene * cytochrome P450 * retinoic acid

Both retinoids and carotenoids are potentially useful chemopreventive agents. In this study we tested the effect of synthetic excentric cleavage products of [beta]-carotene on the growth of the MCF-7, Hs578T and MDA-MB-231 human breast cancer cells. The apo-[beta]-carotenoic acids ([beta]-apo-CA) [beta]-apo-14'-, [beta]-apo-12'-, [beta]-apo-10'- and [beta]-apo-8'-CA are structurally similar to all-trans-retinoic acid (atRA) but have different side chain lengths. Nine days of treatment with atRA inhibited MCF-7 and Hs578T cell proliferation in a dose-dependent manner. [beta]-apo-14'-CA and [beta]-apo-12'-CA significantly inhibited MCF-7 growth, whereas only [beta]-apo-14'-CA inhibited Hs578T growth. None of these treatments inhibited the growth of MDA-MB-231 cells. Potential mechanisms of growth inhibition, i.e., regulation of the cell cycle control proteins E2F1 and retinoblastoma protein (RB), and effect on activator protein-1 (AP-1)-mediated gene regulation were examined. [beta]-apo-14'-CA and atRA inhibited the expression of E2F1 protein in MCF-7 and Hs578T cells. [beta]-apo-14'-CA, [beta]-apo-12'-CA and atRA down-regulated RB protein expression in MCF-7 but not in Hs578T cells. The effect of phorbol ester-induced transcriptional activation of a collagenase promoter-reporter gene construct was strongly inhibited by 1 [micro]mol/L [beta]-apo-14'-CA, atRA (MCF-7, Hs578T) or [beta]-apo-12'-CA (MCF-7). These effects were due neither to cellular conversion of [beta]-apo-CA to atRA nor to high affinity binding to the retinoid acid receptors. Thus, [beta]-apo-CAs were effective inhibitors of breast tumor cell proliferation, possibly mediated through down-regulation of cell cycle regulatory proteins and/or inhibition of AP-1 transcriptional activity. The ability of [beta]-apo-CA to regulate breast tumor cell growth independently of conversion to atRA suggests that these compounds may have fewer side effects than retinoids and, therefore, have a potential chemotherapeutic value that deserves further examination. KEY WORDS * [beta]-carotene * excentric cleavage * breast tumor cells * activator protein-1 * retinoblastoma protein * E2F1

Research has been conducted on the breast cancer. The effect of retinoids and carotenoids on breast cancer cells has been investigated.

Research to increase phytonutrients requires in vitro, animal, and human studies and establishing relevant biomarkers for chronic and fatal diseases. Data contributing to such study is developed through mechanistic, chemical, and genetic epidemiology.

Beta-carotene may act as an anticarcinogen, while its oxidized products may encourage cancer growth. The beta-carotene molecule's instability increases in the presence of free radicals, such as exist in the lungs of cigarette smokers. Antioxidants may help lower cancer risk.