Effects of acyclo-retinoic acid and lycopene on activation of the retinoic acid receptor and proliferation of mammary cancer cells

Carotenoid metabolites, their tissue and blood concentrations in humans and further bioactivity via retinoid receptor-mediated signalling

Many epidemiological studies have emphasised the relation between carotenoid dietary intake and their circulating concentrations and beneficial health effects, such as lower risk of cardiometabolic diseases and cancer. However, there is dispute as to whether the attributed health benefits are due to native carotenoids or whether they are instead induced by their metabolites. Several categories of metabolites have been reported, most notably involving (a) modifications at the cyclohexenyl ring or the polyene chain, such as epoxides and geometric isomers, (b) excentric cleavage metabolites with alcohol-, aldehyde- or carboxylic acid-functional groups or (c) centric cleaved metabolites with additional hydroxyl, aldehyde or carboxyl functionalities, not counting their potential phase-II glucuronidated / sulphated derivatives. Of special interest are the apo-carotenoids, which originate in the intestine and other tissues from carotenoid cleavage by β-carotene oxygenases 1/2 in a symmetrical / non-symmetrical fashion. These are more water soluble and more electrophilic and, therefore, putative candidates for interactions with transcription factors such as NF-kB and Nrf2, as well as ligands for RAR-RXR nuclear receptor interactions. In this review, we discuss in vivo detected apo-carotenoids, their reported tissue concentrations, and potential associated health effects, focusing exclusively on the human situation and based on quantified / semi-quantified carotenoid metabolites proven to be present in humans.

RNA-Seq analysis of the pyloric caecum, liver, and muscle reveals molecular mechanisms regulating fillet color in rainbow trout

BACKGROUND

The characteristic pink-reddish color in the salmonids fillet is an important, appealing quality trait for consumers and producers. The color results from diet supplementation with carotenoids, which accounts for up to 20-30% of the feed cost. Pigment retention in the muscle is a highly variable phenotype. In this study, we aimed to understand the molecular basis for the variation in fillet color when rainbow trout (Oncorhynchus mykiss) fish families were fed an Astaxanthin-supplemented diet. We used RNA-Seq to study the transcriptome profile in the pyloric caecum, liver, and muscle from fish families with pink-reddish fillet coloration (red) versus those with lighter pale coloration (white).

RESULTS

More DEGs were identified in the muscle (5,148) and liver (3,180) than in the pyloric caecum (272). Genes involved in lipid/carotenoid metabolism and transport, ribosomal activities, mitochondrial functions, and stress homeostasis were uniquely enriched in the muscle and liver. For instance, the two beta carotene genes (BCO1 and BCO2) were significantly under-represented in the muscle of the red fillet group favoring more carotenoid retention. Enriched genes in the pyloric caecum were involved in intestinal absorption and transport of carotenoids and lipids. In addition, the analysis revealed the modulation of several genes with immune functions in the pyloric caecum, liver, and muscle.

CONCLUSION

The results from this study deepen our understanding of carotenoid dynamics in rainbow trout and can guide us on strategies to improve Astaxanthin retention in the rainbow trout fillet.

Systemic Photoprotection in Melanoma and Non-Melanoma Skin Cancer

Non-melanoma skin cancers (NMSCs), which include basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and actinic keratosis (AK), are the most common cancer diseases in the Caucasian race. If diagnosed late and improperly treated, BCC and SCC can become locally advanced and metastasize. Malignant melanoma (MM) is less frequent but more lethal than NMSC. Given the individual and social burdens of skin cancers, performing an adequate prevention is needed. Ultraviolet (UV) ray exposure is one of the main risk factors for skin cancer. Thus, the first-choice prevention strategy is represented by photoprotection that can be both topical and systemic. The latter consists of the oral administration of molecules which protect human skin against the damaging effects of UV rays, acting through antioxidant, anti-inflammatory, or immunomodulator mechanisms. Although several compounds are commonly used for photoprotection, only a few molecules have demonstrated their effectiveness in clinical trials and have been included in international guidelines for NMSC prevention (i.e., nicotinamide and retinoids). Moreover, none of them have been demonstrated as able to prevent MM. Clinical and preclinical data regarding the most common compounds used for systemic photoprotection are reported in this review, with a focus on the main mechanisms involved in their photoprotective properties.

Nutritional and Nonnutritional Content of Underexploited Edible Seaweeds

Macroalgae are a valuable source of highly bioactive primary and secondary metabolites that may have useful bioapplications. To investigate the nutritional and nonnutritional contents of underexploited edible seaweeds, proximate composition, including protein, fat, ash, vitamins A, C, and E, and niacin, as well as important phytochemicals, including polyphenols, tannins, flavonoids, alkaloids, sterols, saponins, and coumarins, were screened from algal species using spectrophotometric methods. Ash content ranged from 3.15-25.23% for green seaweeds, 5-29.78% for brown algae, and 7-31.15% for red algae. Crude protein content ranged between 5 and 9.8% in Chlorophyta, 5 and 7.4% in Rhodophyta, and between 4.6 and 6.2% in Phaeophyceae. Crude carbohydrate contents ranged from 20 to 42% for the collected seaweeds, where green algae had the highest content (22.5-42%), followed by brown algae (21-29.5%) and red algae (20-29%). Lipid content was found to be low in all the studied taxa at approximately 1-6%, except for Caulerpa prolifera (Chlorophyta), which had a noticeable higher lipid content at 12.41%. These results indicated that Phaeophyceae were enriched with a high phytochemical content, followed by that of Chlorophyta and Rhodophyta. The studied algal species contained a high amount of carbohydrate and protein, indicating that they could be considered as a healthy food source.

Lycopene intake induces colonic regulatory T cells in mice and suppresses food allergy symptoms

BACKGROUND

Food allergy (FA) is a common disease in children; thus, a high level of safety is required for its prevention and treatment. Colonic regulatory T cells (Tregs) have been suggested to attenuate FA. We investigated the Treg-inducing ability and anti-FA effects of carotenoids, a pigment contained in vegetables and fruits.

METHODS

C57BL/6N mice were fed a diet containing 0.01% (w/w) of lycopene, β-carotene, astaxanthin or lutein for 4 weeks, and the population of colonic Tregs was assessed. Subsequently, to evaluate the Treg-inducing ability of lycopene, splenic naïve CD4⁺ T cells from BALB/c mice were cultured with anti-CD3/CD28 antibody, TGF-β and lycopene, and the frequencies of Tregs were examined. The effect of 0.1% (w/w) lycopene containing diet on FA was investigated in OVA-induced FA model BALB/c mice.

RESULTS

In screening, only lycopene significantly increased the frequency and number of colonic Tregs. Lycopene also increased Treg differentiation in splenic naïve CD4⁺ T cells. In FA mice, lycopene feeding significantly increased the number of colonic Tregs and attenuated allergic symptoms. The expression levels of IL-4, IL-9 and IL-13 mRNA in colonic mucosa were also significantly reduced by lycopene. IL-9 is known to induce proliferation of mast cells, and we found that lycopene feeding significantly reduced the number of mast cells in the colonic mucosa of FA mice.

CONCLUSION

Our results suggest that lycopene, a carotenoid present in many common foods on the market, may have the potential to induce colonic Tregs and suppress FA symptoms.

New Insights into Molecular Mechanism behind Anti-Cancer Activities of Lycopene

Lycopene is a well-known compound found commonly in tomatoes which brings wide range of health benefits against cardiovascular diseases and cancers. From an anti-cancer perspective, lycopene is often associated with reduced risk of prostate cancer and people often look for it as a dietary supplement which may help to prevent cancer. Previous scientific evidence exhibited that the anti-cancer activity of lycopene relies on its ability to suppress oncogene expressions and induce proapoptotic pathways. To further explore the real potential of lycopene in cancer prevention, this review discusses the new insights and perspectives on the anti-cancer activities of lycopene which could help to drive new direction for research. The relationship between inflammation and cancer is being highlighted, whereby lycopene suppresses cancer via resolution of inflammation are also discussed herein. The immune system was found to be a part of the anti-cancer system of lycopene as it modulates immune cells to suppress tumor growth and progression. Lycopene, which is under the family of carotenoids, was found to play special role in suppressing lung cancer.

Mechanistic aspects of carotenoid health benefits - where are we now?

Dietary intake and tissue levels of carotenoids have been associated with a reduced risk of several chronic diseases, including cardiovascular diseases, type 2 diabetes, obesity, brain-related diseases and some types of cancer. However, intervention trials with isolated carotenoid supplements have mostly failed to confirm the postulated health benefits. It has thereby been speculated that dosing, matrix and synergistic effects, as well as underlying health and the individual nutritional status plus genetic background do play a role. It appears that our knowledge on carotenoid-mediated health benefits may still be incomplete, as the underlying mechanisms of action are poorly understood in relation to human relevance. Antioxidant mechanisms - direct or via transcription factors such as NRF2 and NF-κB - and activation of nuclear hormone receptor pathways such as of RAR, RXR or also PPARs, via carotenoid metabolites, are the basic principles which we try to connect with carotenoid-transmitted health benefits as exemplified with described common diseases including obesity/diabetes and cancer. Depending on the targeted diseases, single or multiple mechanisms of actions may play a role. In this review and position paper, we try to highlight our present knowledge on carotenoid metabolism and mechanisms translatable into health benefits related to several chronic diseases.

Algae-Derived Bioactive Compounds with Anti-Lung Cancer Potential

Lung cancer is one of the major causes of death worldwide. Natural molecules with anti-lung cancer potential are of a great interest and considered as very promising alternative to substitute or enhance the efficiency of the conventional drugs. Recently, algae as source of high value-added compounds are considered as very promising source of these bioactive molecules. These are secondary metabolites that consist mainly of derivatives of peptides, carbohydrates, and lipids with various structures. Accordingly, various mechanisms by which different algae molecules demonstrate attenuation of tumor angiogenesis were stated and discussed. The mode of action of the algae bioactives is closely related to their nature and chemical structure. Furthermore, this literature review considers the synergistic effect between microalgae bioactives and conventional drugs and discuss the economic feasibility of producing microalgae bioactives at large scale to conclude with some future perspectives related to algae-based drug discovery.

Mechanistic understanding of β-cryptoxanthin and lycopene in cancer prevention in animal models

To better understand the potential function of carotenoids in the chemoprevention of cancers, mechanistic understanding of carotenoid action on genetic and epigenetic signaling pathways is critically needed for human studies. The use of appropriate animal models is the most justifiable approach to resolve mechanistic issues regarding protective effects of carotenoids at specific organs and tissue sites. While the initial impetus for studying the benefits of carotenoids in cancer prevention was their antioxidant capacity and pro-vitamin A activity, significant advances have been made in the understanding of the action of carotenoids with regards to other mechanisms. This review will focus on two common carotenoids, provitamin A carotenoid β-cryptoxanthin and non-provitamin A carotenoid lycopene, as promising chemopreventive agents or chemotherapeutic compounds against cancer development and progression. We reviewed animal studies demonstrating that β-cryptoxanthin and lycopene effectively prevent the development or progression of various cancers and the potential mechanisms involved. We highlight recent research that the biological functions of β-cryptoxanthin and lycopene are mediated, partially via their oxidative metabolites, through their effects on key molecular targeting events, such as NF-κB signaling pathway, RAR/PPARs signaling, SIRT1 signaling pathway, and p53 tumor suppressor pathways. The molecular targets by β-cryptoxanthin and lycopene, offer new opportunities to further our understanding of common and distinct mechanisms that involve carotenoids in cancer prevention. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

9-Cis-13,14-dihydroretinoic acid, a new endogenous mammalian ligand of retinoid X receptor and the active ligand of a potential new vitamin A category: vitamin A5

The identity of the endogenous RXR ligand has not been conclusively determined, even though several compounds of natural origin, including retinoids and fatty acids, have been postulated to fulfill this role. Filling this gap, 9-cis-13,14-dihydroretinoic acid (9CDHRA) was identified as an endogenous RXR ligand in mice. This review examines the physiological relevance of various potential endogenous RXR ligands, especially 9CDHRA. The elusive steps in the metabolic synthesis of 9CDHRA, as well as the nutritional/nutrimetabolic origin of 9CDHRA, are also explored, along with the suitability of the ligand to be the representative member of a novel vitamin A class (vitamin A5).

Lycopene inhibits hepatic stellate cell activation and modulates cellular lipid storage and signaling

Hepatic stellate cells are liver-specific perivascular cells, identified as the major source of collagen in liver fibrosis, following their activation and conversion to myofibroblast-like cells. Lycopene is a carotenoid with biological activities and protective effects described in different pathologies, but little is known about its role in liver protection. We evaluated the influence of lycopene on the cell cycle and lipid metabolism and monitored the possible pathways involved in lycopene inhibition of stellate cell activation. Lycopene induced expression of the lipocyte phenotype, with an accumulation of fat droplets in cytoplasm, with high synthesis and turnover of phospholipids and triglycerides. Cell proliferation analysis showed that lycopene reduced the growth of GRX cells. Lycopene induced an arrest in the G0/G1 phase, followed by a decrease of cells in the G2/M phase, regardless of the concentration of lycopene used. Lycopene modulated relevant signaling pathways related to cholesterol metabolism, cellular proliferation, and lipid metabolism. Also, lycopene treatment increased the expression of RXR-α, RXR-β, and PPARγ, important biomarkers of liver regeneration. These results show that lycopene was able to negatively modulate events related to the activation of hepatic stellate cells through mechanisms that involve changes in expression of cellular lipid metabolism factors, and suggest that this compound might provide a novel pharmacological approach for the prevention and treatment of fibrotic liver diseases.

β-Carotene in the human body: metabolic bioactivation pathways - from digestion to tissue distribution and excretion

β-Carotene intake and tissue/blood concentrations have been associated with reduced incidence of several chronic diseases. Further bioactive carotenoid-metabolites can modulate the expression of specific genes mainly via the nuclear hormone receptors: retinoic acid receptor- and retinoid X receptor-mediated signalling. To better understand the metabolic conversion of β-carotene, inter-individual differences regarding β-carotene bioavailability and bioactivity are key steps that determine its further metabolism and bioactivation and mediated signalling. Major carotenoid metabolites, the retinoids, can be stored as esters or further oxidised and excreted via phase 2 metabolism pathways. In this review, we aim to highlight the major critical control points that determine the fate of β-carotene in the human body, with a special emphasis on β-carotene oxygenase 1. The hypothesis that higher dietary β-carotene intake and serum level results in higher β-carotene-mediated signalling is partly questioned. Alternative autoregulatory mechanisms in β-carotene / retinoid-mediated signalling are highlighted to better predict and optimise nutritional strategies involving β-carotene-related health beneficial mediated effects.

Substrate Specificity of Purified Recombinant Chicken β-Carotene 9',10'-Oxygenase (BCO2)

Provitamin A carotenoids are oxidatively cleaved by β-carotene 15,15'-dioxygenase (BCO1) at the central 15-15' double bond to form retinal (vitamin A aldehyde). Another carotenoid oxygenase, β-carotene 9',10'-oxygenase (BCO2) catalyzes the oxidative cleavage of carotenoids at the 9'-10' bond to yield an ionone and an apo-10'-carotenoid. Previously published substrate specificity studies of BCO2 were conducted using crude lysates from bacteria or insect cells expressing recombinant BCO2. Our attempts to obtain active recombinant human BCO2 expressed in Escherichia coli were unsuccessful. We have expressed recombinant chicken BCO2 in the strain E. coli BL21-Gold (DE3) and purified the enzyme by cobalt ion affinity chromatography. Like BCO1, purified recombinant chicken BCO2 catalyzes the oxidative cleavage of the provitamin A carotenoids β-carotene, α-carotene, and β-cryptoxanthin. Its catalytic activity with β-carotene as substrate is at least 10-fold lower than that of BCO1. In further contrast to BCO1, purified recombinant chicken BCO2 also catalyzes the oxidative cleavage of 9-cis-β-carotene and the non-provitamin A carotenoids zeaxanthin and lutein, and is inactive with all-trans-lycopene and β-apocarotenoids. Apo-10'-carotenoids were detected as enzymatic products by HPLC, and the identities were confirmed by LC-MS. Small amounts of 3-hydroxy-β-apo-8'-carotenal were also consistently detected in BCO2-β-cryptoxanthin reaction mixtures. With the exception of this activity with β-cryptoxanthin, BCO2 cleaves specifically at the 9'-10' bond to produce apo-10'-carotenoids. BCO2 has been shown to function in preventing the excessive accumulation of carotenoids, and its broad substrate specificity is consistent with this.

Substrate specificity of purified recombinant human β-carotene 15,15'-oxygenase (BCO1)

Humans cannot synthesize vitamin A and thus must obtain it from their diet. β-Carotene 15,15'-oxygenase (BCO1) catalyzes the oxidative cleavage of provitamin A carotenoids at the central 15-15' double bond to yield retinal (vitamin A). In this work, we quantitatively describe the substrate specificity of purified recombinant human BCO1 in terms of catalytic efficiency values (kcat/Km). The full-length open reading frame of human BCO1 was cloned into the pET-28b expression vector with a C-terminal polyhistidine tag, and the protein was expressed in the Escherichia coli strain BL21-Gold(DE3). The enzyme was purified using cobalt ion affinity chromatography. The purified enzyme preparation catalyzed the oxidative cleavage of β-carotene with a Vmax = 197.2 nmol retinal/mg BCO1 × h, Km = 17.2 μM and catalytic efficiency kcat/Km = 6098 M(-1) min(-1). The enzyme also catalyzed the oxidative cleavage of α-carotene, β-cryptoxanthin, and β-apo-8'-carotenal to yield retinal. The catalytic efficiency values of these substrates are lower than that of β-carotene. Surprisingly, BCO1 catalyzed the oxidative cleavage of lycopene to yield acycloretinal with a catalytic efficiency similar to that of β-carotene. The shorter β-apocarotenals (β-apo-10'-carotenal, β-apo-12'-carotenal, β-apo-14'-carotenal) do not show Michaelis-Menten behavior under the conditions tested. We did not detect any activity with lutein, zeaxanthin, and 9-cis-β-carotene. Our results show that BCO1 favors full-length provitamin A carotenoids as substrates, with the notable exception of lycopene. Lycopene has previously been reported to be unreactive with BCO1, and our findings warrant a fresh look at acycloretinal and its alcohol and acid forms as metabolites of lycopene in future studies.

Carotenoid metabolism in mammals, including man: formation, occurrence, and function of apocarotenoids

Vitamin A was recognized as an essential nutrient 100 years ago. In the 1930s, it became clear that dietary β-carotene was cleaved at its central double to yield vitamin A (retinal or β-apo-15'-carotenal). Thus a great deal of research has focused on the central cleavage of provitamin A carotenoids to form vitamin A (retinoids). The mechanisms of formation and the physiological role(s) of noncentral (eccentric) cleavage of both provitamin A carotenoids and nonprovitamin A carotenoids has been less clear. It is becoming apparent that the apocarotenoids exert unique biological activities themselves. These compounds are found in the diet and thus may be absorbed in the intestine, or they may form from enzymatic or nonenzymatic cleavage of the parent carotenoids. The mechanism of action of apocarotenoids in mammals is not fully worked out. However, as detailed in this review, they have profound effects on gene expression and work, at least in part, through the modulation of ligand-activated nuclear receptors. Understanding the interactions of apocarotenoids with other lipid-binding proteins, chaperones, and metabolizing enzymes will undoubtedly increase our understanding of the biological roles of these carotenoid metabolites.

Lycopene and beta-carotene induce growth inhibition and proapoptotic effects on ACTH-secreting pituitary adenoma cells

Pituitary adenomas comprise approximately 10-15% of intracranial tumors and result in morbidity associated with altered hormonal patterns, therapy and compression of adjacent sella turcica structures. The use of functional foods containing carotenoids contributes to reduce the risk of chronic diseases such as cancer and vascular disorders. In this study, we evaluated the influence of different concentrations of beta-carotene and lycopene on cell viability, colony formation, cell cycle, apoptosis, hormone secretion, intercellular communication and expression of connexin 43, Skp2 and p27(kip1) in ACTH-secreting pituitary adenoma cells, the AtT20 cells, incubated for 48 and 96 h with these carotenoids. We observed a decrease in cell viability caused by the lycopene and beta-carotene treatments; in these conditions, the clonogenic ability of the cells was also significantly decreased. Cell cycle analysis revealed that beta-carotene induced an increase of the cells in S and G2/M phases; furthermore, lycopene increased the proportion of these cells in G0/G1 while decreasing the S and G2/M phases. Also, carotenoids induced apoptosis after 96 h. Lycopene and beta-carotene decreased the secretion of ACTH in AtT20 cells in a dose-dependent manner. Carotenoids blocked the gap junction intercellular communication. In addition, the treatments increased the expression of phosphorylated connexin43. Finally, we also demonstrate decreased expression of S-phase kinase-associated protein 2 (Skp2) and increased expression of p27(kip1) in carotenoid-treated cells. These results show that lycopene and beta-carotene were able to negatively modulate events related to the malignant phenotype of AtT-20 cells, through a mechanism that could involve changes in the expression of connexin 43, Skp2 and p27(kip1); and suggest that these compounds might provide a novel pharmacological approach to the treatment of Cushing's disease.

Lycopene-derived bioactive retinoic acid receptors/retinoid-X receptors-activating metabolites may be relevant for lycopene's anti-cancer potential

Dietary consumption of tomato products and especially the red tomato pigment lycopene has been associated with lower risk of cancer. New evidence is emerging toward metabolic pathways mediating the anti-cancer activities of lycopene. In this review, we explore associations between tomatoes and lycopene intake and cancer and relate this to the metabolic activation pathways of lycopene via carotene oxygenases and further carotenoid/retinoid-metabolizing enzymes to apo-lycopenoids. Several of these apo-lycopenoids have already been identified but up to date no direct connection between lycopene metabolism and apo-lycopenoids mediated receptor activation pathways has been established. Retinoic acid receptors/retinoid-X receptors activation pathways in particular, may be mediated via lycopene metabolites that are related to retinoic acids. Various studies have shown an association between lower concentration of insulin-like growth factor-1 upon lycopene treatment, cancer incidences, and retinoid-mediated signaling. In this review, we interrelate tomato/lycopene ingestion and cancer incidence, with metabolic activation of lycopene and retinoid-mediated signaling. The aim is to discuss a potential mechanism to explain lycopene related anti-cancer activities by modulation of insulin-like growth factor-1 concentrations via lycopene metabolite activation of retinoid-mediated signaling.

Lycopene induces retinoic acid receptor transcriptional activation in mice

SCOPE

Lycopene is a lipophilic carotenoid and provides the red colour to tomatoes and tomato product. Various studies indicated that lycopene and tomatoes/tomato products are able to positively influence various diseases associated with a chronic inflammation. The mechanism of action of lycopene to elicit these effects is partly unknown. A possible mechanism is that biological metabolites of lycopene may activate nuclear hormone receptors in mammalian cells. The aim of this study was to investigate the potential of orally administered lycopene and all-trans retinoic acid (ATRA) for the induction of the retinoic acid receptor (RAR) in a transgenic retinoic acid response-element (RARE)-reporter mouse system.

METHODS AND RESULTS

Orally administered lycopene (100 mg/kg bw in beadlets, n = 6) and ATRA as an endogenous RAR ligand (50 mg/kg bw, n = 6) for the induction of the retinoic acid receptor in male mice using a transgenic RARE-reporter mouse system.

CONCLUSION

Lycopene treatments induced RARE-mediated cell signalling indicated by quantified bioimaging, increased luciferase activity and up-regulated the retinoid target genes in selected organs of the mice. We conclude that lycopene can induce RAR-transcriptional activation in mice and lycopene might be a precursor of still non-identified biologically active metabolites.

Lycopene metabolism and its biological significance

The beneficial effects of a high intake of tomatoes and tomato products on the risk of certain chronic diseases have been presented in many epidemiologic studies, with the suggestion that lycopene (a major carotenoid in tomatoes) is a micronutrient with important health benefits. Within the past few years, we have gained greater knowledge of the metabolism of lycopene and the biological effects of lycopene derivatives. In particular, the characterization and study of β-carotene 9',10'-oxygenase has shown that this enzyme can catalyze the excentric cleavage of both provitamin and non-provitamin A carotenoids to form apo-10'-carotenoids, including apo-10'-lycopenoids from lycopene. This raised an important question of whether the effect of lycopene on various cellular functions and signaling pathways is a result of the direct actions of intact lycopene or its derivatives. Several reports, including our own, support the notion that the biological activities of lycopene can be mediated by apo-10'-lycopenoids. More research is clearly needed to identify and characterize additional lycopene metabolites and their biological activities, which will potentially provide invaluable insights into the mechanisms underlying the effects of lycopene in humans.

Comparative antioxidant effects of lycopene, apo-10'-lycopenoic acid and apo-14'-lycopenoic acid in human macrophages exposed to H2O2 and cigarette smoke extract

Much of the beneficial effects of tomato lycopene in the prevention of chronic diseases has been attributed to its antioxidant properties, which could be mediated by its metabolites and/or oxidation products. However, the biological functions of these lycopene derivatives remain still unknown. In the present study, we evaluated and compared the antioxidant efficacy of the lycopene eccentric cleavage products apo-10'-lycopenoic acid and apo-14'-lycopenoic acid in counteracting the oxidative effects of H(2)O(2) and cigarette smoke extract (CSE) in THP-1 macrophages. Both apo-10'-lycopenoic acid and apo-14'-lycopenoic acid were able to inhibit spontaneous and H(2)O(2)-induced ROS production in a dose-dependent manner. Such an effect was accompanied by an inhibition of MAPK phosphorylation, by NF-κB inactivation, and by inhibition of hsp-70 and hsp-90 expressions. Both apo-lycopenoic acids also decreased CSE-induced ROS production, 8-OHdG formation and reduced the increase in NOX-4 and COX-2 expressions caused by CSE. However, in both the models of oxidative stress, apo-14'-lycopenoic acid was much more potent as an antioxidant than apo-10'-lycopenoic acid, showing antioxidant properties similar to lycopene. These data strongly suggest that apo-lycopenoic acids, and particularly apo-14'-lycopenoic acid, may mediate some of the antioxidant functions of lycopene in cells.

Cancer chemoprevention by carotenoids

Carotenoids are natural fat-soluble pigments that provide bright coloration to plants and animals. Dietary intake of carotenoids is inversely associated with the risk of a variety of cancers in different tissues. Preclinical studies have shown that some carotenoids have potent antitumor effects both in vitro and in vivo, suggesting potential preventive and/or therapeutic roles for the compounds. Since chemoprevention is one of the most important strategies in the control of cancer development, molecular mechanism-based cancer chemoprevention using carotenoids seems to be an attractive approach. Various carotenoids, such as β-carotene, a-carotene, lycopene, lutein, zeaxanthin, β-cryptoxanthin, fucoxanthin, canthaxanthin and astaxanthin, have been proven to have anti-carcinogenic activity in several tissues, although high doses of β-carotene failed to exhibit chemopreventive activity in clinical trials. In this review, cancer prevention using carotenoids are reviewed and the possible mechanisms of action are described.

Carotenoids and apocarotenoids in cellular signaling related to cancer: a review

The basis for the vivid color of carotenoids and their antioxidant activity is the multiple conjugated double bonds, which are characteristic for these phytonutrients. Moreover, the cleavage of these oxidation-prone double bonds leads to the formation of apocarotenoids. A large number of carbonyl-containing oxidation products are expected to be produced as a result of carotenoid oxidation and these can be further metabolized into the corresponding acids and alcohols. As discussed in this review, many, but not all, of these potential products have been detected and identified in plants as well as in human and animal plasma and tissues. Some of these compounds were found to be biologically active as anticancer agents. In addition to the inhibition of cancer cell proliferation, several carotenoid metabolites were shown to modulate the activity of various transcription systems. These include ligand-activated nuclear receptors, such as the retinoic acid receptor, retinoid X receptor, peroxisome proliferator-activated receptor and estrogen receptor, as well as other transcription systems that have an important role in cancer, such as the electrophile/antioxidant response element pathway and nuclear factor-κB. Therefore, apocarotenoids can be considered as natural compounds with multifunctional, rather than monofunctional, activity and, thus, can be useful in the prevention of cancer and other degenerative diseases.

Biological activity of lycopene metabolites: implications for cancer prevention

While early studies focused on the potential roles in health and disease of provitamin A carotenoids, such as beta-carotene, research over the past decade has provided a framework for our understanding of the functions of non-provitamin A carotenoids such as lycopene, especially in regards to its association with a reduced risk of a number of chronic diseases, including cancer. Recent data suggests that lycopene metabolites may possess specific biological activities on several important cellular signaling pathways and molecular targets. Carotenoid metabolites may have more important biological roles than their parent compounds in human health and disease. This notion has been reinforced by the observation of both beneficial and detrimental effects of carotenoid metabolites in cancer prevention.

Estradiol and tamoxifen differently affects the inhibitory effects of vitamin A and their metabolites on the proliferation and expression of alpha2beta1 integrins in MCF-7 breast cancer cells

PURPOSE

Retinoids are well known inhibitors of estrogen-dependent breast cancer cell growth and differentiation. alpha2beta1 integrins are involved in the normal growth and differentiation of breast cells, they also take part in many pathological processes including malignancies. The aim of the study was to evaluate the effect of estradiol and tamoxifen on the inhibitory action of retinoids on the proliferation of MCF-7 breast cancer cells and alpha2beta1 integrin expression.

MATERIALS AND METHODS

Evaluation was based on [3H]thymidine incorporation and the proliferative activity of PCNA- and Ki 67-positive cells. Expression of alpha2beta1 was assessed through immunocytochemical analysis.

RESULTS

Treatment of cancer cells with the examined compounds and tamoxifen (10 microM) revealed that only 13-cis retinoic acid (13-cis RA) and all-trans retinoic acid (ATRA) (10(-5) M) decreased cells proliferation compared to the tamoxifen group (30.84%+/-3.32, p<0.01 and 31.05%+/-4.67, p<0.01, respectively). The lowest fraction of PCNA positive cells was also observed after the simultaneous addition ATRA (10(-5) M) and tamoxifen (10 microM) (30.75%+/-0.95, p<0.01, compared to the tamoxifen group). Our results showed that the decrease of alpha2beta1 integrin expression by 13-cis RA (10(-5) M, 49.6+/-3.25%) and ATRA (10-9 M, 15.0%+/-5.0) was augmented by tamoxifen and to a lesser extent by estradiol, particularly in the case of ATRA at 10(-7) or 10(-9) M.

CONCLUSIONS

This data suggest that tamoxifen augments the inhibitory effect of retinoids on proliferation and alpha2beta1 integrin expression in MCF-7 cells.

The chemistry of novel xanthophyll carotenoids

Natural product isolates are typically not developed as drug candidates because of the difficulty in obtaining the desired stable molecular orientation (ie, stereochemistry), purity, and scale required to meet pharmaceutical industry standards. Recent advances in medicinal and process chemistry have played key roles in transforming a class of dietary natural products-carotenoids-into potential medical therapeutics. Carotenoids are natural pigments derived from the acyclic C40 isoprenoid lycopene, which can also be classified as a tetraterpene. Carotenoids are classified on their chemical composition as either carotenes or xanthophylls. There are 5 C40 carotenoids manufactured synthetically on an industrial scale, including lycopene, ss,ss-carotene, and canthaxanthin (which are achiral compounds); zeaxanthin (produced in enantiopure form, as the 3R,3'R enantiomer); and astaxanthin (produced as mixture of configurational isomers) for use as nutritional supplements and for animal feed additives in poultry farming and aquaculture that are essential for the animals' growth, health and reproduction. The xanthophyll astaxanthin shows pharmaceutical potential, but the configurational complexity has thus far made it difficult to synthesize an enantiopure form on a large scale. Astaxanthin has 2 identical asymmetric carbon atoms (position 3 and 3') and can therefore exist in 4 different configurations, providing 3 different configurational isomers: (3S,3'S) and (3R,3'R), which are enantiomers, and (3R,3'S) and (3S,3'R), which are identical (a meso form). An enantiopure industrial scale synthesis of astaxanthin (3S,3'S) has recently been developed by BASF AG. The desired stereochemistry (chirality) is introduced early in the synthetic process by a proprietary catalytic reaction using an intermediate of the existing technical astaxanthin production process as a substrate. By controlling this essential process, it is possible to produce pharmaceutical quality astaxanthin in quantities large enough to support drug development programs for medical therapies.

The growth-inhibitory effects of tomatoes digested in vitro in colon adenocarcinoma cells occur through down regulation of cyclin D1, Bcl-2 and Bcl-xL

In the present study, we utilised an in vitro digestion procedure to deliver molecules contained in tomatoes to cultured cells and to analyse potential mechanisms underlying the antitumoural effects of tomatoes reported in the literature. Ripe tomatoes underwent in vitro simulated digestion and the aqueous fraction obtained was delivered to HT-29 and HCT-116 colon adenocarcinoma cells. The amount of lycopene released during digestion and transferred to the aqueous fraction during digestion was 10-fold lower than that present in tomato homogenate before digestion. The carotenoid was accumulated by colon adenocarcinoma cells in a dose-dependent manner after the addition of tomato digestate (20-100 ml/l) for 24 h. Tomato digestate inhibited the growth of HT-29 and HCT-116 cells in a dose-dependent manner. Growth inhibition resulted from an arrest of cell cycle progression at the G0/G1 phase and by apoptosis induction. A down regulation of cyclin D1, Bcl-2 and Bcl-xL expression was also observed, without apparent changes in p53, p21, p27 and Bax. In conclusion, the present data demonstrate that the in vitro digestion procedure represents a useful approach to supply tomato to colon cultured cells. Moreover, we have shown that tomato digestate is able to inhibit the growth of colon cancer cells by modulating the expression of regulators of the cell cycle and apoptosis.

Apo-10'-lycopenoic acid inhibits lung cancer cell growth in vitro, and suppresses lung tumorigenesis in the A/J mouse model in vivo

High intake of lycopene has been associated with a lower risk of a variety of cancers including lung cancer. We recently showed that lycopene can be converted to apo-10'-lycopenoids [Hu et al. (2006). J. Biol. Chem., 281, 19327-19338] in mammalian tissues both in vitro and in vivo, raising the question of whether apo-10'-lycopenoids have biological activities against lung carcinogenesis. In the present study, we report that apo-10'-lycopenoic acid inhibited the growth of NHBE normal human bronchial epithelial cells, BEAS-2B-immortalized normal bronchial epithelial cells and A549 non-small cell lung cancer cells. This inhibitory effect of apo-10'-lycopenoic acid was associated with decreased cyclin E, inhibition of cell cycle progression from G(1) to S phase and increased cell cycle regulators p21 and p27 protein levels. In addition, apo-10'-lycopenoic acid transactivated the retinoic acid receptor beta (RARbeta) promoter and induced the expression of RARbeta. We further examined the effect of apo-10'-lycopenoic acid treatment on 4-(N-methyl-N-nitrosamino)-1-(3-pyridal)-1-butanone (NNK)-induced lung tumorigenesis in the A/J mouse model. We found that the lung tumor multiplicity was decreased dose dependently from an average of 16 tumors per mouse in the NNK injection alone group, to an average of 10, 7 and 5 tumors per mouse in groups injected with NNK and supplemented with 10, 40 and 120 mg/kg diet of apo-10'-lycopenoic acid, respectively. These observations demonstrate that apo-10'-lycopenoic acid is a biological active metabolite of lycopene and suggest that apo-10'-lycopenoic acid is a potential chemopreventive agent against lung tumorigenesis.

Lycopene differentially induces quiescence and apoptosis in androgen-responsive and -independent prostate cancer cell lines

BACKGROUND & AIMS

Lycopene has been credited with a number of health benefits including a decrease in prostate cancer risk. Our study investigates the molecular mechanism underlying anti-cancer activity of lycopene-based products in androgen-responsive (LNCaP) and androgen-independent (PC3) cells.

METHODS

The effect of lycopene-based agents on prostate cancer growth and survival were examined using proliferation assays, bromodeoxyuridine incorporation and flow cytometric analysis of cellular DNA content. Biochemical effects of lycopene treatment were investigated by immunoblotting for changes in the absolute levels and phosphorylation states of cell cycle regulatory and signalling proteins.

RESULTS

LNCaP and PC3 cells treated with the lycopene-based agents undergo mitotic arrest, accumulating in G0/G1 phase. Immunoblot screening indicated that lycopene's antiproliferative effects are likely achieved through a block in G1/S transition mediated by decreased levels of cyclins D1 and E and cyclin dependent kinase 4 and suppressed Retinoblastoma phosphorylation. These responses correlated with decreased insulin-like growth factor-I receptor expression and activation, increased insulin-like growth factor binding protein 2 expression and decreased AKT activation. Exposure to lycopene at doses as low as 10 nM for 48 h induced a profound apoptotic response in LNCaP cells. In contrast PC3 cells were resistant to apoptosis at doses up to 1 microM.

CONCLUSIONS

Lycopene exposure can suppress phosphatidylinositol 3-kinase-dependent proliferative and survival signalling in androgen-responsive LNCaP and androgen-independent PC3 cells suggesting that the molecular mechanisms for the cytostatic and cytotoxic actions of lycopene involve induction of G0/G1 cell cycle arrest. This study supports further examination of lycopene as a potential agent for both the prevention and treatment of prostate cancer.

Lycopenoids: are lycopene metabolites bioactive?

In vitro lycopene is the most potent antioxidant among carotenoids. While antioxidant function may be relevant to health, we hypothesize that metabolites of lycopene may be bioactive and responsible for the beneficial effects of tomato product consumption. We term these metabolites "lycopenoids," which we believe may be produced from carotenoid monooxygenase (CMO) II, paralleling the production of retinoids from beta-carotene by CMO I. We present evidence suggesting that tomato carotenoid metabolites may be responsible for the reduced risk of prostate cancer seen in men consuming high levels of tomato products. Finally, we identify gaps in knowledge in this evolving area of carotenoid research.

Modulation of the growth hormone-insulin-like growth factor (GH-IGF) axis by pharmaceutical, nutraceutical and environmental xenobiotics: an emerging role for xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. A review

The growth hormone-insulin-like growth factor (GH-IGF) axis has gained considerable focus over recent years. One cause of this increased interest is due to a correlation of age-related decline in plasma GH/IGF levels with age-related degenerative processes, and it has led to the prescribing of GH replacement therapy by some practitioners. On the other hand, however, research has also focused on the pro-carcinogenic effects of high GH-IGF levels, providing strong impetus for finding regimes that reduce its activity. Whereas the effects of GH/IGF activity on the action of xenobiotic-metabolizing enzyme systems is reasonably well appreciated, the effects of xenobiotic exposure on the GH-IGF axis has not received substantial review. Relevant xenobiotics are derived from pharmaceutical, nutraceutical and environmental exposure, and many of the mechanisms involved are highly complex in nature, not easily predictable from existing in vitro tests and do not always predict well from in vivo animal models. After a review of the human and animal in vivo and in vitro literature, a framework for considering the different levels of direct and indirect modulation by xenobiotics is developed herein, and areas that still require further investigation are highlighted, i.e. the actions of common endocrine disruptors such as pesticides and phytoestrogens, as well as the role of xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. It is anticipated that a fuller appreciation of the existing human paradigms for GH-IGF axis modulation gained through this review may help explain some of the variation in levels of plasma IGF-1 and its binding proteins in the population, aid in the prescription of particular dietary regimens to certain individuals such as those with particular medical conditions, guide the direction of long-term drug/nutraceutical safety trials, and stimulate ideas for future research. It also serves to warn athletes that using compounds touted as performance enhancing because they promote short-term GH release could in fact be detrimental to performance in the long-run.

Lycopene inhibition of IGF-induced cancer cell growth depends on the level of cyclin D1

BACKGROUND

Insulin-like growth factors (IGFs) play an important role in normal and cancerous cell proliferation. Moreover, in recent studies IGF-I has been implicated as a major cancer risk factor. The tomato carotenoid lycopene and all-trans retinoic acid (atRA) have been shown to inhibit growth factor-induced proliferation of different types of cancer cells. This action is associated with inhibition of cell cycle progression in G0/G1 phase. Cyclin D1 acts as a growth factor sensor in G1 phase and is overexpressed in many breast cancer tumors. We have previously demonstrated that slowdown of serum-stimulated cell cycle progression from G1 to S phase by lycopene correlates with reduction in cyclin D1 levels, suggesting that the expression of this protein is a main target for lycopene's action.

AIM OF THE STUDY

To determine whether the reported reduction in cyclin D1 level is the key mechanism for lycopene and atRA inhibitory action on IGF-I-induced cell cycle progression.

RESULTS

Human breast (MCF-7) and endometrial (ECC-1) cancer cells were synchronized in G0/G1 phase by serum deprivation followed by stimulation with IGF-I. Cell treatment with lycopene and atRA inhibited IGF-I-stimulated cell cycle progression from G1 to S phase and decreased retinoblastoma protein (pRb) phosphorylation. These events were associated with a reduction in cyclin D1 and p21(CIP1/WAF1) level, but not that of p27(KIP1). To test the hypothesis that the decrease in cyclin D1 has a major role in the inhibitory effects of lycopene and atRA, we examined the ability of these two agents to suppress cell cycle progression in MCF-7.7D1.13 cells which are capable of expressing cyclin D1 under the control of the Zn-inducible metallothionein promoter. Our results showed that ectopic expression of cyclin D1 can overcome cell cycle inhibition caused by lycopene and atRA.

CONCLUSIONS

Our findings suggest that attenuation of cyclin Dl levels by lycopene and atRA is an important mechanism for the reduction of the mitogenic action of IGF-I.

Lycopene

Oxidative stress is now recognized as an important etiological factor in the causation of several chronic diseases including cancer, cardiovascular diseases, osteoporosis, and diabetes. Antioxidants play an important role in mitigating the damaging effects of oxidative stress on cells. Lycopene, a carotenoid antioxidant, has received considerable scientific interest in recent years. Epidemiological, tissue culture, and animal studies provide convincing evidence supporting the role of lycopene in the prevention of chronic diseases. Human intervention studies are now being conducted to validate epidemiological observations and to understand the mechanisms of action of lycopene in disease prevention. To obtain a better understanding of the role of lycopene in human health, this chapter reviews the most recent information pertaining to its chemistry, bioavailability, metabolism, role in the prevention of prostate cancer and cancer of other target organs, its role in cardiovascular diseases, osteoporosis, hypertension, and male infertility. A discussion of the most relevant molecular markers of cancer is also included as a guide to future researchers in this area. The chapter concludes by reviewing global intake levels of lycopene, suggested levels of intake, and future research directions.

Lycopene induces apoptosis in immortalized fibroblasts exposed to tobacco smoke condensate through arresting cell cycle and down-regulating cyclin D1, pAKT and pBad

There is a lot of interest in the health benefits of dietary carotenoids and on the relationship of these compounds with smoke. In particular, it is unknown if the enhanced cancer risk observed in smokers following beta-carotene supplementation can be also found using other carotenoids. Here, we studied the effects of the tomato carotenoid lycopene on molecular pathways involved in cell cycle progression, apoptosis and survival in immortalized RAT-1 fibroblasts exposed to cigarette smoke condensate (TAR). Lycopene (0.5-2.0 microM) inhibited cell growth in a dose-and time-dependent manner, by arresting cell cycle progression and by promoting apoptosis in cells exposed to TAR. The arrest of cell cycle was independent of p53 and of 8-OH-dG DNA damage and related to a decreased expression of cyclin D1. Moreover, the carotenoid up-regulated apoptosis and down-regulated the phosphorylation of AKT and Bad in cells exposed to TAR. Such an effect was associated to an inhibition of TAR-induced expression of Cox-2 and hsp90, which is known to maintain AKT activity. This study suggests that lycopene, differently from beta-carotene, can exert protective effects against cigarette smoke condensate.

The biodistribution of a single oral dose of [14C]-lycopene in rats prefed either a control or lycopene-enriched diet

Lycopene (lyc) has emerged as a primary candidate for dietary interventions of prostate cancer; however, research regarding its absorption, tissue distribution, and metabolism is limited. Previously, we evaluated the biodistribution (3-168 h) of a single oral dose of 14C-lyc in rats prefed lyc for 30 d. The liver was the primary depot for lyc, and the 14C and 14C-polar products appeared in tissues as early as 3 h after dosing. In the current study, F344 rats (n = 48) were randomly assigned to 1 of 4 groups prefed either a control or lyc-enriched diet (0.25 g lyc/kg diet) for 30 d and killed at 5 or 24 h after receiving a single oral dose of 14C-lyc. The percentage of the 14C dose absorbed at 24 h was lower (5.5 +/- 0.5%) in lyc-prefed (LP) rats than in control-prefed (CP) rats (6.9 +/- 0.4%, P < 0.04). Hepatic total 14C and 14C-lyc in CP rats was greater than in LP rats at 24 h (P < 0.005). A portion of 14C was delivered to extrahepatic tissues as early as 5 h, irrespective of diet. Of the tissues analyzed, an increase in the percentage in 14C-polar products occurred between 5 and 24 h only in the prostate and seminal vesicles, suggesting increased accumulation of 14C-polar products in these tissues, irrespective of prior dietary treatment. These data suggest that lyc absorption, tissue uptake, and catabolism were affected by prefeeding and that lyc can be partially taken up by extrahepatic tissues from the postprandial triglyceride-rich fraction.

Thermal degradation products formed from carotenoids during a heat-induced degradation process of paprika oleoresins (Capsicum annuum L.)

The high-temperature treatment of paprika oleoresins (Capsicum annuum L.) modified the carotenoid profile, yielding several degradation products, which were analyzed by HPLC-APCI-MS. From the initial MS data, compounds were grouped in two sets. Set 1 grouped compounds with m/z 495, and set 2 included compounds with m/z 479, in both cases for the protonated molecular mass. Two compounds of the first set were tentatively identified as 9,10,11,12,13,14,19,20-octanor-capsorubin (compound II) and 9,10,11,12,13,14,19,20-octanor-5,6-epoxide-capsanthin (compound IV), after isolation by semipreparative HPLC and analysis by EI-MS. Compounds VII, VIII, and IX from set 2 were assigned as 9,10,11,12,13,14,19,20-octanor-capsanthin and isomers, respectively. As these compounds were the major products formed in the thermal process, it was possible to apply derivatization techniques (hydrogenation and silylation) to analyze them by EI-MS, before and after chemical derivatization. Taking into account structures of the degradation products, the cyclization of polyolefins could be considered as the general reaction pathway in thermally induced reactions, yielding in the present study xylene as byproduct and the corresponding nor-carotenoids.

Carotenoids activate the antioxidant response element transcription system

Epidemiologic studies have found an inverse association between consumption of tomato products and the risk of certain types of cancers. However, the mechanisms underlying this relationship are not completely understood. One mechanism that has been suggested is induction of phase II detoxification enzymes. Expression of phase II enzymes is regulated by the antioxidant response element (ARE) and the transcription factor Nrf2 (nuclear factor E2-related factor 2). In this study, we determined the role of this transcription system in the induction of phase II enzymes by carotenoids. We found that in transiently transfected cancer cells, lycopene transactivated the expression of reporter genes fused with ARE sequences. Other carotenoids such as phytoene, phytofluene, β-carotene, and astaxanthin had a much smaller effect. An increase in protein as well as mRNA levels of the phase II enzymes NAD(P)H:quinone oxidoreductase and γ-glutamylcysteine synthetase was observed in nontransfected cells after carotenoid treatment. Ethanolic extract of lycopene containing unidentified hydrophilic derivatives of the carotenoid activated ARE with similar potency to lycopene. The potency of the carotenoids in ARE activation did not correlate with their effect on intracellular reactive oxygen species and reduced glutathione level, which may indicate that ARE activation is not solely related to their antioxidant activity. Nrf2, which is found predominantly in the cytoplasm of control cells, translocated to the nucleus after carotenoid treatment. Interestingly, part of the translocated Nrf2 colocalized with the promyelocytic leukemia protein in the promyelocytic leukemia nuclear bodies. The increase in phase II enzymes was abolished by a dominant-negative Nrf2, suggesting that carotenoid induction of these proteins depends on a functional Nrf2 and the ARE transcription system.

Carotenoids and transcription

The possible involvement of several transcription systems in the anticancer activity of carotenoids is the focus of this review. Carotenoids modulate the basic mechanisms of cell proliferation, growth factor signaling, gap junctional intercellular communication, and produce changes in the expression of many proteins participating in these processes. The changes in the expression of multiple proteins suggest that the initial effect of carotenoids involves modulation of transcription. We and others have found evidence for the role of several transcription systems, such as the retinoid receptors, activator protein-1 (AP-1), peroxisome proliferator-activated receptors (PPAR), xenobiotic receptors and the antioxidant response element (ARE), in the anticancer activity of carotenoids. The observed modulation of a network of transcription systems may provide the molecular basis for the synergistic anticancer effects of the combinations of various carotenoids together with other dietary and pharmacologic compounds.

Lycopene inhibits the growth of normal human prostate epithelial cells in vitro

Lycopene has repeatedly been shown to inhibit the growth of human prostate cells in vitro. However, previous studies with lycopene have focused on cancer specimens, and it is still unclear whether this carotenoid affects the growth of normal human prostate cells as well. Therefore, we investigated the effects of lycopene on normal human prostate epithelial cells (PrEC) by treating them with synthetic all-E-lycopene (up to 5 micromol/L) and assessing proliferation via [3H]thymidine incorporation. The effects of lycopene on cell cycle progression were investigated via flow cytometry. To elucidate whether lycopene modulates cyclins involved in cell cycle progression, protein expressions of cyclins D1 and E were analyzed. The results show that lycopene significantly inhibited the growth of PrEC in a dose-dependent fashion. Flow cytometry revealed a significant cell cycle arrest in the G0/G1 phase. This effect was confirmed by inhibition of cyclin D1 protein expression, whereas cyclin E levels remained unchanged. The results demonstrate that lycopene inhibits growth of nonneoplastic PrEC in vitro. We hypothesize that lycopene might likewise inhibit the growth of prostatic epithelial cells in vivo. This might have an effect on prostate development and/or on enlargement of prostate tissue as found in benign prostate hyperplasia, a potential precursor of prostate cancer.

The effects of lycopene on the proliferation of human breast cells and BRCA1 and BRCA2 gene expression

The purpose of this study was to demonstrate the effects of lycopene, the major tomato carotenoid, on the expression of the BRCA1 and BRCA2 genes in three breast tumour cell lines, MCF-7, HBL-100, MDA-MB-231 and the fibrocystic breast cell line MCF-10a. Flow cytometry analysis showed a G(1)/S phase cell cycle-arrest after treatment of the cells with 10 microM lycopene for 48 h. mRNA expression was studied by quantitative reverse transcription-polymerase chain reaction using the Taqman method. We observed an increase of BRCA1 and BRCA2 mRNA in the oestrogen receptor (ER)-positive cell lines (MCF-7 and HBL-100), and a decrease (MDA-MB-231) or no change (MCF-10a) in the ER-negative cell lines. BRCA1 and BRCA2 proteins were quantified by perfusion affinity chromatography. No variation in their expression was observed. These preliminary results on the effects of lycopene on the expression of BRCA1 and BRCA2 oncosuppressor genes in breast cancer may reflect cross-talk between the oestrogen and retinoic acid receptor (RAR) pathways.

The role of carotenoids in the prevention of human pathologies

Reactive oxygen species (ROS) and oxidative damage to biomolecules have been postulated to be involved in the causation and progression of several chronic diseases, including cancer and cardiovascular diseases, the two major causes of morbidity and mortality in Western world. Consequently dietary antioxidants, which inactivate ROS and provide protection from oxidative damage are being considered as important preventive strategic molecules. Carotenoids have been implicated as important dietary nutrients having antioxidant potential, being involved in the scavenging of two of the ROS, singlet molecular oxygen (1O2) and peroxyl radicals generated in the process of lipid peroxidation. Carotenoids are lipophilic molecules which tend to accumulate in lipophilic compartments like membranes or lipoproteins. Chronic ethanol consumption significantly increases hydrogen peroxide and decreases mitochondrial glutathione (GSH) in cells overexpressing CYP2E1. The depletion of mitochondrial GSH and the rise of hydrogen peroxide are responsible for the ethanol-induced apoptosis. Increased intake of lycopene, a major carotenoid in tomatoes, consumed as the all-trans-isomer attenuates alcohol induced apoptosis in 2E1 cells and reduces risk of prostate, lung and digestive cancers. Cancer-preventive activities of carotenoids have been associated as well as with their antioxidant properties and the induction and stimulation of intercellular communication via gap junctions which play a role in the regulation of cell growth, differentiation and apoptosis. Gap junctional communication between cells which may be a basis for protection against cancer development is independent of the antioxidant property.

[14C]-lycopene and [14C]-labeled polar products are differentially distributed in tissues of F344 rats prefed lycopene

Epidemiologic evidence suggests a possible role for lycopene-rich foods in the prevention of prostate cancer and cardiovascular disease. Despite active research in disease reduction, there is a paucity of information on the absorption, biodistribution and metabolism of lycopene. The aim of this study was to evaluate the biodistribution of 14C-lycopene (specific activity, 1.83 microCi/mg) and 14C-labeled products after an oral dose of 22 microCi of 14C-lycopene in male rats that had been prefed a lycopene-containing diet (0.25 g lycopene/ kg diet) for 30 d. The percentage of 14C excreted in feces and urine over the 168 h was 68%. Quantitatively, serum 14C levels were maintained between 3 and 24 h then decreased at 72 h (P < 0.05). At all time points the majority of tissue 14C was in the liver (approximately 72%), although total hepatic 14C decreased after 24 h. In a comparison of the extrahepatic tissue at 168 h, the 14C was greatest in adipose tissue followed by spleen and then adrenal; approximately 80% of the 14C in the liver was in the cis and all-trans configuration at all time points. At 3 h, the 14C in seminal vesicles was primarily in the all-trans plus 5-cis forms (70%), but by 168 h, 55% of 14C was present as 14C-polar products. Despite the presence of unlabeled lycopene in the prostate, the primary 14C form was in 14C-polar products (67-92%), even at 3 h. The percentage and amount of 14C-polar products in the dorsolateral prostate lobe increased from 3 to 24 h and then reached a plateau. The data suggest that lycopene may be metabolized differently among tissues in rats prefed lycopene.

Correlation of serum retinol and its relation with lipid prolile in Indian cancer patients

The present study was undertaken to investigate the relation of retinol with lipid profile of patients with cancers of breast, stomach, oesophagus, colon, gallbladder, pancreas, lung and cervix. Serum retinol was assayed in 120 patients and 40 healthy normal control by reverse phase HPLC using CLC-ODS C-18 columns and retinyl acetate as an internal standard.Significant decease in serum cholesterol and LDL was observed in patients with cancers of esophagus, colon, stomach, pancreas and gallbladder respectively.Retinol was reduced in all forms of cancers but pronounced decrease was observed in oesophagus, gallbladder, pancreas, stomach and colon. Serum Retinol in all patients was directly correlated with total cholesterol and LDL. These findings suggest that therapeutic modalities of this vitamin could be planned for these patients, as vitamin A is known to act as an antioxidant for prevention of certain cancers.

Modulation of transcriptional activity by antioxidant carotenoids

It is widely accepted that diet changes are a powerful means to prevent cancer. The possible involvement of transcriptional activity in the anticancer activity of carotenoids will be the focus of this review. Carotenoids function as potent antioxidants, and this is clearly a major mechanism of their action. In addition carotenoids action involves interference in several pathways related to cancer cell proliferation and includes changes in the expression of many proteins participating in these processes such as connexins, phase II enzymes, cyclins, cyclin-dependent kinases and their inhibitors. These changes in protein expression suggest that the initial effect involves modulation of transcription by ligand-activated nuclear receptors or by other transcription factors. It is feasible to suggest that carotenoids and their oxidized derivatives interact with a network of transcription systems that are activated by different ligands at low affinity and specificity and that this activation leads to the synergistic inhibition of cell growth.

Lycopene in serum, skin and adipose tissues after tomato-oleoresin supplementation in patients undergoing haemorrhoidectomy or peri-anal fistulotomy

Lycopene, the main carotenoid found in tomatoes and tomato-based products, has been reported to be protective against several types of cancer. Assessment of changes in plasma concentration of carotenoids following ingestion of lycopene-rich food sources does not necessarily predict changes in lycopene concentration or distribution of its isomers in other body tissues. Our aim was to determine the relationship between concentrations of lycopene and other tomato carotenoids in human serum and body tissues after tomato-oleoresin supplementation. Tomato lycopene oleoresin (30 mg/d) or a placebo was administered for 1 to 7 weeks to seventy-five volunteers undergoing elective haemorrhoidectomy or peri-anal fistulotomy. Carotenoid concentration and isomer distribution in blood and in the surgically removed skin and adipose tissues was measured by HPLC. The serum concentration of lycopene increased after supplementation from 0.26 (SD 0.12) to 0.52 (SD 0.25) micromol/l (n 35; P<0.0001). In the placebo group (n 40), lycopene serum concentration did not change significantly. Serum lycopene concentration after treatment was 2.2-fold greater in the lycopene group than in the placebo group, a slightly higher ratio than that found in skin and adipose tissue (1.6- and 1.4-fold higher than the placebo, respectively). A significant correlation between serum and tissue concentrations was found for both beta-carotene and lycopene in the placebo group, whereas in the lycopene-supplemented group the correlation between serum and tissues remained the same for beta-carotene but for lycopene was weak. Lycopene supplementation did not significantly change the proportion of all-trans v. cis isomers in the serum and tissues, despite the fact that more than 90 % of the supplemented lycopene was in the all-trans form. These results show that tomato-oleoresin supplementation increases lycopene concentrations in serum and in adipose tissue and skin. The ability to increase lycopene levels in tissues is one of the prerequisites for using it as a food supplement with health benefits.

A C35 carotenoid biosynthetic pathway

Upon coexpression with Erwinia geranylgeranyldiphosphate (GGDP) synthase in Escherichia coli, C(30) carotenoid synthase CrtM from Staphylococcus aureus produces novel carotenoids with the asymmetrical C(35) backbone. The products of condensation of farnesyldiphosphate and GDP, C(35) structures comprise 40 to 60% of total carotenoid accumulated. Carotene desaturases and carotene cyclases from C(40) or C(30) pathways accepted and converted the C(35) substrate, thus creating a C(35) carotenoid biosynthetic pathway in E. coli. Directed evolution to modulate desaturase step number, together with combinatorial expression of the desaturase variants with lycopene cyclases, allowed us to produce at least 10 compounds not previously described. This result highlights the plastic and expansible nature of carotenoid pathways and illustrates how combinatorial biosynthesis coupled with directed evolution can rapidly access diverse chemical structures.