Beta-carotene modulates human prostate cancer cell growth and may undergo intracellular metabolism to retinol

The Influence of β-Carotene and Its Liposomal Form on the Expression of EMT Markers and Androgen-Dependent Pathways in Different Prostate Cell Lines

Prostate cancer (PCa) is the most common malignancy in men. Although the prognosis in the early stages is good, the treatment of advanced PCa remains a formidable challenge. Even after an initial response to hormone therapy or chemotherapy, recurrences are frequent and resistance to any systemic treatment is common. β-Carotene (BC), a plant-derived tetraterpene, is known for its antioxidant capacity and can modulate multiple cellular signaling pathways, potentially affecting androgen synthesis. We investigated the influence of BC (dissolved in EtOH/THF with a cell culture medium or encapsulated in liposomes (LP-BCs)) on the viability, migration potential, and connective tissue cleavage capabilities of several PCa cell lines (Du145, LNCaP, PC-3, and 22Rv1) and a healthy prostate model (RWPE cells). BC significantly reduced the proliferative capacity of all investigated cell lines at various concentrations (1.5-30 µM) and decreased cell migration. However, it significantly increased the expression of epidermal-mesenchymal transition (EMT) master proteins in all cancer cell lines and RWPE (p < 0.05) These effects were not observed with LP-BCs. This study suggests that LP-BCs, with their higher antiproliferative capabilities and pronounced inhibition of the EMT, may be a more effective form of possible PCa prevention or treatment than the free form. LPs may also modulate lipid metabolism in PCa cells.

Beta-carotene exerted anti-proliferative and apoptotic effect on malignant mesothelioma cells

High blood levels of β-carotene and increased intake in the diets are inversely proportional to incidence of many cancer types. Antioxidant activity of β-carotene was proposed to be related with its antitumor effect. Despite this plant derivative substance being sought in many cancer types, the effectiveness of β-carotene against malignant mesothelioma remained unclear. Therefore, the present study aims to explore the impact of β-carotene on cell viability, apoptosis, and oxidative stress in mesothelioma cells. Human mesothelioma cell SPC212 were treated with β-carotene (3.125-200 μM) for 24, 48, 72, and 96 h. Cytotoxicity was measured with the MTT assay (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide). Annexin-V/propidium iodide (PI) and caspase 3/7 biomarkers were used to identify apoptotic cells. Finally, the oxidative stress was evaluated with flow cytometry. The results of the measurements indicated a significant decline in viable mesothelioma cancer cell numbers upon β-carotene treatment in time- and concentration-dependent manner when compared to control cells. Furthermore, β-carotene treatment led to apoptosis induction according to both annexin V/PI and caspase 3/7 assays. Furthermore, β-carotene increased oxidative stress in SPC212 cells. These results show how β-carotene affects proliferative, apoptotic, and oxidative properties in SPC212 malignant pleural mesothelioma cells and provide useful insights into future studies.

Enhanced cytotoxic activity of beta carotene conjugated liposomes towards breast cancer cell line: comparative studies with cyclophosphamide

This work aims to evaluate cyclophosphamide (Cyclo) cytotoxic efficacy combined with liposomes in the presence or absence of beta carotene (beta) by detecting the effects of these compounds on the breast cancer cell line (MCF-7) DNA damage. The IC50 value for beta in cytotoxic assay with MCF-7 treated cells was 21.15 μg/ml, while with liposomal beta (LipoBeta) being 121 μg/ml. The free Cyclo IC50 value was 719.86 μg/ml, its liposomal form (LipoCyclo) was 172 μg/ml. The results indicated that in contrast with Cyclo and control values, all comet assay parameters for the LipoBeta were significantly increased (P < 0.05). In MCF-7 cells treated with beta, the findings show a higher intensity of comet tail than those treated with LipoBeta. The presence of several double-strand breaks suggests this high intensity relative to the head. The molecular combination between Cyclo and liposomes in the presence or absence of beta was characterized. Dynamic light scattering measurements confirmed the mono-dispersity of all samples. The incorporation of Cyclo or beta into liposomes exhibited a slight shift to higher temperature compared to the main peak of empty liposomes that exists at 101.5°C which creates a conformational disorder within the phospholipids. The FTIR study showed structural alterations in vesicles after liposome encapsulation.

Antioxidant Activity and Healthy Benefits of Natural Pigments in Fruits: A Review

Natural pigments, including carotenoids, flavonoids and anthocyanidins, determine the attractive color of fruits. These natural pigments are essential secondary metabolites, which play multiple roles in the whole life cycle of plants and are characterized by powerful antioxidant activity. After decades of research and development, multiple benefits of these natural pigments to human health have been explored and recognized and have shown bright application prospects in food, medicine, cosmetics and other industries. In this paper, the research progress of natural fruit pigments in recent years was reviewed, including the structural characteristics and classification, distribution in fruits and analysis methods, biosynthetic process, antioxidant capacity and mechanism, bioaccessibility and bioavailability, and health benefits. Overall, this paper summarizes the recent advances in antioxidant activity and other biological functions of natural fruit pigments, which aims to provide guidance for future research.

Diapolycopenedioic-acid-diglucosyl ester and keto-myxocoxanthin glucoside ester: Novel carotenoids derived from Exiguobacterium acetylicum S01 and evaluation of their anticancer and anti-inflammatory activities

Inflammation is pivotal for the development of gastrointestinal cancer and linked to poor survival and limited therapeutic options. In this study, six structurally different carotenoids were isolated and identified from the methanolic extract of Exiguobacterium acetylicum S01 namely lycopene (Car-I), diapolycopenedioic-acid-diglucosyl-ester (Car-II), β-carotene (Car-III), zeaxanthin (Car-IV), astaxanthin (Car-V), and keto-myxocoxanthin glucoside-ester (Car-VI). Further, their anti-cancer, anti-inflammatory, and antioxidant potentials were evaluated. The MTT assay was used to determine the effect of carotenoids on viability of colorectal cancer (HT-29) as well as peripheral blood mononuclear cells (PBMCs). Results revealed that all the six carotenoids were demonstrated a significant inhibition of HT-29 cells viability in a dose-dependent manner whereas there was no cytotoxic effect in PBMCs. The study also recorded that six carotenoids considerably inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) production, tumor necrosis factor-alpha (TNF-α), and lipid peroxidation in PBMCs. Moreover, antioxidant potentials of Car-II and Car-VI were significantly (p = 0.001) higher than ascorbic acid as determined by a 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay. Therefore, our results ascertained the role of carotenoids derived from E. acetylicum S01 in developing potential therapeutic agents for inflammation-associated cancer.

High-level β-carotene production from xylose by engineered Saccharomyces cerevisiae without overexpression of a truncated HMG1 (tHMG1)

β-Carotene is a natural pigment and health-promoting metabolite, and has been widely used in the nutraceutical, feed, and cosmetic industries. Here, we engineered a GRAS yeast Saccharomyces cerevisiae to produce β-carotene from xylose, the second most abundant and inedible sugar component of lignocellulose biomass. Specifically, a β-carotene biosynthetic pathway containing crtYB, crtI, and crtE from Xanthophyllomyces dendrorhous was introduced into a xylose-fermenting S. cerevisiae. The resulting strain produced β-carotene from xylose at a titer threefold higher than from glucose. Interestingly, overexpression of tHMG1, which has been reported as a critical genetic perturbation to enhance metabolic fluxes in the mevalonate pathway and β-carotene production in yeast when glucose is used, did not further improve the production of β-carotene from xylose. Through fermentation profiling, metabolites analysis, and transcriptional studies, we found the advantages of using xylose as a carbon source, instead of glucose, for β-carotene production to be a more respiratory feature of xylose consumption, a larger cytosolic acetyl-CoA pool, and an upregulated expression level of rate-limiting genes in the β-carotene-producing pathway, including ACS1 and HMG1. As a result, 772.8 mg/L of β-carotene was obtained in a fed-batch bioreactor culture with xylose feeding. Considering the inevitable large scale production of xylose when cellulosic biomass-based bioeconomy is implemented, our results suggest xylose utilization is a promising strategy for overproduction of carotenoids and other isoprenoids in engineered S. cerevisiae.

Screening of In Vitro Health Benefits of Tangerine Tomatoes

Tomatoes have been associated with various health benefits, including the prevention of chronic diseases. The cis-isomers of lycopene occurring in tangerine tomatoes were, through clinical trials, proven to be more bioavailable than the all-trans lycopene found in red tomatoes. Nonetheless, scientific evidence regarding the bioactivities of the tangerine tomatoes is lacking. In this article, the antioxidant, anticancer, and anti-inflammatory properties of extracts prepared from four different tomato varieties, namely Alfred, Olga's Round Golden Chicken Egg, Golden Green, and Golden Eye, were investigated. While the antioxidant capacities of the extracts were measured through the ferric reducing antioxidant power (FRAP) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays, their anti-proliferative properties in prostate cancer cell lines were examined through the Sulforhodamine-B (SRB) assay. The anti-inflammatory activities of the extracts were assessed through the toll-like receptor (TLR)2, TLR4, and nucleotide-binding oligomerization domain containing protein 2 (NOD2)-mediated inflammatory pathways. Our results show that the tangerine tomatoes had lower IC50 values in both the anticancer and anti-inflammatory assays compared to the red tomatoes. Specifically, the half-maximal inhibitory concentration (IC50) values of the tangerine tomatoes in LNCaP cells were approximately two to three fold lower than the red tomato (IC50: 14.46, 5.62, and 8.08 mg dry tomato equivalent/mL from Alfred hexane-acetone, Olga's Round Golden Chicken Egg hexane, and Golden Green hexane, respectively). These findings indicate that the tangerine varieties, Olga's Round Golden Chicken Egg and Golden Green, possess greater potential to be used in conjunction with treatment and for the prevention of cancer and inflammatory-related diseases than the Alfred (red) and Golden Eye (high beta-carotene) varieties.

Role of Zucchini and Its Distinctive Components in the Modulation of Degenerative Processes: Genotoxicity, Anti-Genotoxicity, Cytotoxicity and Apoptotic Effects

Zucchini (Cucurbita pepo subsp. pepo) is a seasonal vegetable with high nutritional and medical values. Many useful properties of this fruit are attributed to bioactive compounds. Zucchini fruits ("Yellow" and "Light Green" varieties) and four distinctive components (lutein, β-carotene, zeaxanthin and dehydroascorbic acid) were selected. Firstly, the lutein, β-carotene, zeaxanthin and dehydroascorbic acid contents were determined in these fruits. Then, in order to evaluate the safety and suitability of their use, different assays were carried out: (i) genotoxicity and anti-genotoxicity tests to determine the safety and DNA-protection against hydrogen peroxide; (ii) cytotoxicity; and (iii) DNA fragmentation and Annexin V/PI (Propidium Iodide) assays to evaluate the pro-apoptotic effect. Results showed that: (i) all the substances were non-genotoxic; (ii) all the substances were anti-genotoxic except the highest concentration of lutein; (iii) "Yellow" zucchini epicarp and mesocarp exhibited the highest cytotoxic activity (IC50 > 0.1 mg/mL and 0.2 mg/mL, respectively); and (iv) "Light Green" zucchini skin induced internucleosomal DNA fragmentation, β-carotene being the possible molecule responsible for its pro-apoptotic activity. To sum up, zucchini fruit could play a positive role in human health and nutrition due to this fruit and its components were safe, able to inhibit significantly the H₂O₂-induced damage and exhibit anti-proliferative and pro-apoptotic activities toward HL60 (human promyelocytic leukemia cells) tumor cells. The information generated from this research should be considered when selecting potential accessions for breeding program purposes.

Enzymology of retinoic acid biosynthesis and degradation

All-trans-retinoic acid is a biologically active derivative of vitamin A that regulates numerous physiological processes. The concentration of retinoic acid in the cells is tightly regulated, but the exact mechanisms responsible for this regulation are not completely understood, largely because the enzymes involved in the biosynthesis of retinoic acid have not been fully defined. Recent studies using in vitro and in vivo models suggest that several members of the short-chain dehydrogenase/reductase superfamily of proteins are essential for retinoic acid biosynthesis and the maintenance of retinoic acid homeostasis. However, the exact roles of some of these recently identified enzymes are yet to be characterized. The properties of the known contributors to retinoid metabolism have now been better defined and allow for more detailed understanding of their interactions with retinoid-binding proteins and other retinoid enzymes. At the same time, further studies are needed to clarify the interactions between the cytoplasmic and membrane-bound proteins involved in the processing of hydrophobic retinoid metabolites. This review summarizes current knowledge about the roles of various biosynthetic and catabolic enzymes in the regulation of retinoic acid homeostasis and outlines the remaining questions in the field.

Tomato-based food products for prostate cancer prevention: what have we learned?

Evidence derived from a vast array of laboratory studies and epidemiological investigations have implicated diets rich in fruits and vegetables with a reduced risk of certain cancers. However, these approaches cannot demonstrate causal relationships and there is a paucity of randomized, controlled trials due to the difficulties involved with executing studies of food and behavioral change. Rather than pursuing the definitive intervention trials that are necessary, the thrust of research in recent decades has been driven by a reductionist approach focusing upon the identification of bioactive components in fruits and vegetables with the subsequent development of single agents using a pharmacologic approach. At this point in time, there are no chemopreventive strategies that are standard of care in medical practice that have resulted from this approach. This review describes an alternative approach focusing upon development of tomato-based food products for human clinical trials targeting cancer prevention and as an adjunct to therapy. Tomatoes are a source of bioactive phytochemicals and are widely consumed. The phytochemical pattern of tomato products can be manipulated to optimize anticancer activity through genetics, horticultural techniques, and food processing. The opportunity to develop a highly consistent tomato-based food product rich in anticancer phytochemicals for clinical trials targeting specific cancers, particularly the prostate, necessitates the interactive transdisciplinary research efforts of horticulturalists, food technologists, cancer biologists, and clinical translational investigators.

beta-Carotene and beta-cryptoxanthin but not lutein evoke redox and immune changes in RAW264 murine macrophages

The mechanism of immunological benefits induced by carotenoids has not been fully elucidated. Here, we investigated some of the immunity-related properties of beta-carotene and two other carotenoids, beta-cryptoxanthin, and lutein, on the murine macrophages cell line RAW264. beta-Carotene added to the culture medium accumulated in the cells in a time- and dose-dependent manner. The accumulation was positively correlated with cellular lipid peroxidation, demonstrating the pro-oxidative activity of beta-carotene, and also with the synthesis of glutathione, an intracellular antioxidant. Conversely, accumulation of beta-carotene was negatively correlated with the transcription of immune-active molecules, such as IL-1beta, IL-6, and IL-12 p40, in cells stimulated by LPS and INF-gamma. The transcription of the pro-inflammatory cytokines IL-1beta and IL-6 was more sensitive to the accumulation of beta-carotene than was IL-12 p40. The accumulation of beta-cryptoxanthin in cells resulted in effects similar to those of beta-carotene. However, lutein accumulated minimally and did not significantly affect the cells. These results demonstrate that beta-carotene, and beta-cryptoxanthin as well, can accumulate in RAW264 cells and induce changes in intracellular redox status, which in turn regulate the immune function of macrophages.

Current concepts in diet and prostate cancer

Increasing evidence suggests that diet influences the initiation and progression of prostate cancer. Herein, we review associations of specific foods and nutrients with prostate cancer, summarizing important and clinically relevant emerging data on this complex topic. Foods and nutrients associated with a decreased risk of prostate cancer include lycopene, soy, cruciferous vegetables, vitamin E and selenium. Although prospective clinical trials of dietary supplements and dietary modification to prevent or control prostate cancer are underway, definitive clinical evidence is currently lacking.

Agents used for chemoprevention of prostate cancer may influence PSA secretion independently of cell growth in the LNCaP model of human prostate cancer progression

BACKGROUND

The aim of this study was to evaluate the inhibitory growth effects of different potential chemopreventive agents in vitro and to determine their influence on PSA mRNA and protein expression with an established screening platform.

METHODS

LNCaP and C4-2 cells were incubated with genistein, seleno-L-methionine, lycopene, DL-alpha-tocopherol, and trans-beta-carotene at three different concentrations and cell growth was determined by the MTT assay. PSA mRNA expression was assessed by quantitative real-time RT-PCR and secreted PSA protein levels were quantified by the microparticle enzyme immunoassay.

RESULTS

Genistein, seleno-l-methionine and lycopene inhibited LNCaP cell growth, and the proliferation of C4-2 cells was suppressed by seleno-L-methionine and lycopene. PSA mRNA expression was downregulated by genistein in LNCaP but not C4-2 cells. No other compound tested altered PSA mRNA expression. PSA protein expression was downregulated by genistein, seleno-L-methionine, DL-alpha-tocopherol in LNCaP cells. In C4-2 cells only genistein significantly reduced the secretion of PSA protein.

CONCLUSIONS

In the LNCaP progression model PSA expression depends on the compound, its concentration and on the hormonal dependence of the cell line used and does not necessarily reflect cell growth or death. Before potential substances are evaluated in clinical trials using PSA as a surrogate end point marker, their effect on PSA mRNA and protein expression has to be considered to correctly assess treatment response by PSA.

The sensitivity to beta-carotene growth-inhibitory and proapoptotic effects is regulated by caveolin-1 expression in human colon and prostate cancer cells

Although several mechanisms have been proposed to explain the putative role of beta-carotene in cancer, no studies have investigated a possible influence of beta-carotene on caveolin-1 (cav-1) pathway, an important intracellular signaling deregulated in cancer. Here, different human colon and prostate cancer cell lines, expressing (HCT-116, PC-3 cells) or not (Caco-2, LNCaP cells) cav-1, were treated with varying concentrations of beta-carotene (0.5-30 muM) for different periods of time (3-72 h) and the effects on cell growth were investigated. The results of this study show that (i) beta-carotene acted as a growth-inhibitory agent in cav-1-positive cells, but not in cav-1-negative cells; (ii) in cav-1-positive cells, the carotenoid downregulated in a dose- and time-dependent manner the expression of cav-1 protein and messenger RNA levels and inhibited AKT phosphorylation which, in turn, stimulated apoptosis by increasing the expression of beta-catenin and c-myc and the activity of caspases-3, -7, -8 and -9; when the carotenoid was removed from culture medium, a progressive increase in cell growth was observed with respect to beta-carotene-treated cells and (iii) the transfection of cav-1 in cav-1-negative cells increased cell sensitivity to beta-carotene by inducing apoptosis. This effect was accompanied by a reduction of both cav-1 and AKT phosphorylation and by an increase of c-myc and beta-catenin expression. Silencing of c-Myc attenuated beta-carotene-induced apoptosis and beta-catenin expression. All together, these data suggest that the modulation of cav-1 pathway by beta-carotene could be a novel mechanism by which the carotenoid acts as a potent growth-inhibitory agent in cancer cells.

Lifestyle during and after cancer treatment

The aim of this overview was to examine the evidence for links between lifestyle during and after cancer treatment and quality of life, risk of treatment side-effects, rate of progression and prevention of relapse. The reviewed studies were divided into categories according to the role lifestyle plays in progression, during treatment, and in relapse prevention. The evaluated evidence was utilised to show potential lifestyle interventions to facilitate well-being and quality-of-life initiatives. There is now persuasive evidence that dietary choice and exercise can improve the physical and psychological function of patients with cancer. There is also persuasive evidence that lifestyle choice can prevent cancer or the reoccurrence of cancer in susceptible individuals, and possibly improve survival.

Protective effect of Dunaliella salina (Volvocales, Chlorophyta) against experimentally induced fibrosarcoma on wistar rats

The beta-carotene-yielding microalga, Dunaliella salina (Dunal) Teod. maintained in De Walne's medium was harvested and lyophilized. Fibrosarcoma was induced in rats by 20-methylcholanthrene. 0.5 g and 1.0 g of lyophilized D. salina powder was administered to the rats orally through carboxy methyl cellulose. Cisplatin was administered along with vitamin E to compare the protective effect of D. salina against fibrosarcoma. Administration of D. salina decreased the levels of cholesterol and lactate dehydrogenase as well as the activities of catalase, superoxide dismutase, serum aspartate aminotransaminase, serum alanine aminotransferase, when compared to control. A significant reduction in the levels of hepatic and renal RNA and DNA was observed in the sarcoma rats when treated with D. salina powder. Histopathological studies of tumor tissues showed regenerative and regressive changes. beta-carotene globules isolated from the powder of Dunaliella salina confirmed the presence of 9-cis-beta-carotene and all-trans-beta-carotene.

A prospective study of lycopene and tomato product intake and risk of prostate cancer

BACKGROUND

Dietary lycopene and tomato products may reduce risk of prostate cancer; however, uncertainty remains about this possible association.

METHODS

We evaluated the association between intake of lycopene and specific tomato products and prostate cancer risk in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, a multicenter study designed to investigate cancer early detection methods and etiologic determinants. Participants completed both a general risk factor and a 137-item food frequency questionnaire at baseline. A total of 1,338 cases of prostate cancer were identified among 29,361 men during an average of 4.2 years of follow-up.

RESULTS

Lycopene intake was not associated with prostate cancer risk. Reduced risks were also not found for total tomato servings or for most tomato-based foods. Statistically nonsignificant inverse associations were noted for pizza [all prostate cancer: relative risk (RR), 0.83; 95% confidence interval (95% CI), 0.67-1.03 for >or=1 serving/wk versus < 0.5 serving/mo; P(trend)=0.06 and advanced prostate cancer: RR, 0.79; 95% CI, 0.56-1.10; P(trend)=0.12] and spaghetti/tomato sauce consumption (advanced prostate cancer: RR=0.81, 95% CI, 0.57-1.16 for >or=2 servings/wk versus<1 serving/mo; P(trend)=0.31). Among men with a family history of prostate cancer, risks were decreased in relation to increased consumption of lycopene (P(trend)=0.04) and specific tomato-based foods commonly eaten with fat (spaghetti, P(trend)=0.12; pizza, P(trend)=0.15; lasagna, P(trend)=0.02).

CONCLUSIONS

This large study does not support the hypothesis that greater lycopene/tomato product consumption protects from prostate cancer. Evidence for protective associations in subjects with a family history of prostate cancer requires further corroboration.

Biosynthesis of 14C-phytoene from tomato cell suspension cultures (Lycopersicon esculentum) for utilization in prostate cancer cell culture studies

This work describes the development and utilization of a plant cell culture production approach to biosynthesize and radiolabel phytoene and phytofluene for prostate cancer cell culture studies. The herbicide norflurazon was added to established cell suspension cultures of tomato (Lycopersicon esculentum cv. VFNT cherry), to induce the biosynthesis and accumulation of the lycopene precursors, phytoene and phytofluene, in their natural isomeric forms (15-cis-phytoene and two cis-phytofluene isomers). Norflurazon concentrations, solvent carrier type and concentration, and duration of culture exposure to norflurazon were screened to optimize phytoene and phytofluene synthesis. Maximum yields of both phytoene and phytofluene were achieved after 7 days of treatment with 0.03 mg norflurazon/40 mL fresh medium, provided in 0.07% solvent carrier. Introduction of 14C-sucrose to the tomato cell culture medium enabled the production of 14C-labeled phytoene for subsequent prostate tumor cell uptake studies. In DU 145 prostate tumor cells, it was determined that 15-cis-phytoene and an oxidized product of phytoene were taken up and partially metabolized by the cells. The ability to biosynthesize, radiolabel, and isolate these carotenoids from tomato cell cultures is a novel, valuable methodology for further in vitro and in vivo investigations into the roles of phytoene and phytofluene in cancer chemoprevention.

Carotenoid actions and their relation to health and disease

Based on extensive epidemiological observation, fruits and vegetables that are a rich source of carotenoids are thought to provide health benefits by decreasing the risk of various diseases, particularly certain cancers and eye diseases. The carotenoids that have been most studied in this regard are beta-carotene, lycopene, lutein and zeaxanthin. In part, the beneficial effects of carotenoids are thought to be due to their role as antioxidants. beta-Carotene may have added benefits due its ability to be converted to vitamin A. Additionally, lutein and zeaxanthin may be protective in eye disease because they absorb damaging blue light that enters the eye. Food sources of these compounds include a variety of fruits and vegetables, although the primary sources of lycopene are tomato and tomato products. Additionally, egg yolk is a highly bioavailable source of lutein and zeaxanthin. These carotenoids are available in supplement form. However, intervention trials with large doses of beta-carotene found an adverse effect on the incidence of lung cancer in smokers and workers exposed to asbestos. Until the efficacy and safety of taking supplements containing these nutrients can be determined, current dietary recommendations of diets high in fruits and vegetables are advised.

Relationship Between Plasma Carotenoids and Prostate Cancer

Carotenoids, particularly lycopene, are thought to decrease prostate cancer risk, but the relationship between plasma carotenoid concentrations and risk in various populations has not been well characterized. Comparing 118 non-Hispanic Caucasian men mainly from southeast Texas with nonmetastatic prostate cancer with 52 healthy men from the same area, we conducted a case-control analysis evaluating associations between risk and plasma levels of total carotenoids, beta-cryptoxanthin, alpha- and trans-beta-carotene, lutein and zeaxanthin, total lycopenes, trans-lycopene, total cis-lycopenes, and cis-lycopene isoforms 1, 2, 3, and 5. Risk for men with high plasma levels of alpha-carotene, trans-beta-carotene, beta-cryptoxanthin, and lutein and zeaxanthin was less than half that for those with lower levels. In contrast, we observed no significant associations for total lycopenes, all-trans-lycopene, and cis-lycopene isomer peaks 2, 3, and 5, although high levels of cis-lycopene isomer peak 1 were inversely associated with risk. Analysis of men with aggressive disease (Gleason scores of > or =7, n = 88) vs. less aggressive cases (Gleason scores of <7, n = 30) failed to reveal significant associations between carotenoid levels and the risk of diagnosis with aggressive disease. These findings suggest that, in these men, higher circulating levels of alpha-cryptoxanthin, alpha-carotene, trans-beta-carotene, and lutein and zeaxanthin may contribute to lower prostate cancer risk but not to disease progression.

Inhibition of prostate cancer cell growth by an avocado extract: role of lipid-soluble bioactive substances

Although the avocado is known as a rich source of monounsaturated fatty acids, there has been far less attention given to its content of other bioactive substances including carotenoids, which might contribute to cancer preventive properties similar to those attributed to other fruits and vegetables. The yellow-green color of the avocado prompted us to study the carotenoid content of this fruit using established methods in our laboratory. The California Hass avocado (Persea americana Mill.) was selected for study, because it is the most commonly consumed variety in the southwest United States. These avocados were found to contain the highest content of lutein among commonly eaten fruits as well as measurable amounts of related carotenoids (zeaxanthin, alpha-carotene, and beta-carotene). Lutein accounted for 70% of the measured carotenoids, and the avocado also contained significant quantities of vitamin E. An acetone extract of avocado containing these carotenoids and tocopherols was shown to inhibit the growth of both androgen-dependent (LNCaP) and androgen-independent (PC-3) prostate cancer cell lines in vitro. Incubation of PC-3 cells with the avocado extract led to G(2)/M cell cycle arrest accompanied by an increase in p27 protein expression. Lutein alone did not reproduce the effects of the avocado extract on cancer cell proliferation. In common with other colorful fruits and vegetables, the avocado contains numerous bioactive carotenoids. Because the avocado also contains a significant amount of monounsaturated fat, these bioactive carotenoids are likely to be absorbed into the bloodstream, where in combination with other diet-derived phytochemicals they may contribute to the significant cancer risk reduction associated with a diet of fruits and vegetables.

The effect of β-carotene and its derivatives on cytotoxicity, differentiation, proliferative potential and apoptosis on the three human acute leukemia cell lines: U-937, HL-60 and TF-1

The influence of beta-carotene (BC) and its derivatives on differentiation, proliferation and apoptosis in three human acute leukemia cell lines was studied. We investigated: (i) the cellular uptake of BC, (ii) the cytotoxicity, (iii) the effect on cell cycle progression and/or apoptosis. The dose- and time-dependent pattern of cellular BC uptake in all studied cell lines was seen. We did not observe any cytotoxic effect of BC and ATRA in the chosen concentrations. There was only limited effect of BC on gene expression. The microarrray analysis of U-937 cell line exposed to BC for 72 h showed an increased expression of BAX gene. This finding was confirmed by real-time Q-PCR analysis, and supported by a flow cytometry apoptosis tests. We did not observe any influence of studied components on cellular proliferation. The induction of differentiation after incubation with ATRA in HL-60 cells was noted. The induction of cellular apoptosis by BC was seen in all studied cell lines. We demonstrated that BC used in the concentrations achievable in vivo does not affect the proliferation and differentiation process of the studied leukemic cell lines, but can influence and enhance the apoptosis by modulating the expression of the regulatory genes.

Different effect of beta-carotene on proliferation of prostate cancer cells

It was shown that high doses of beta-carotene (>30 microM) decrease proliferation of prostate cancer cells in vitro. However, it is rather doubtful whether such concentration of beta-carotene is really accessible at cellular level. We studied the effect of 3 and 10 microM beta-carotene on proliferation and gene expression in LNCaP and PC-3 prostate cancer cell lines. Beta-carotene--more efficiently absorbed from medium by androgen-sensitive LNCaP cells--increased proliferation of LNCaP cells whereas it had weaker effect on PC-3 cells. Initial global analysis of expression of genes in both cell lines treated with 10 microM beta-carotene (Affymetrix HG-U133A) showed remarkable differences in number of responsive genes. Their recognition allows for conclusion that differences between prostate cancer cell lines in response to beta-carotene treatment are due to various androgen sensitivities of LNCaP and PC-3 cells. Detailed analysis of expression of selected genes in beta-carotene treated LNCaP cells at the level of mRNA and protein indicated that the observed increase of proliferation could have been the result of slight induction of a few genes affecting proliferation (c-myc, c-jun) and apoptosis (bcl-2) with no significant effect on major cell cycle control genes (cdk2, RB, E2F-1).

Mechanisms of genomic and non-genomic actions of carotenoids

Carotenoids are highly bioactive dietary compounds that have the potential to have significant effects on human health. It is becoming increasingly clear that the various biological effects that carotenoids exert could be driven via a number of different mechanisms. These include direct pro- and antioxidant effects, redox sensitive cell signalling, vitamin A signalling pathways and other as yet unidentified mechanisms. This article provides an overview of the known effects of carotenoids and discusses the use of model systems and functional genomic approaches further to elucidate their modes of action.

Neoxanthin and fucoxanthin induce apoptosis in PC-3 human prostate cancer cells

Neoxanthin and fucoxanthin, which have the characteristic structure of 5,6-monoepoxide and an allenic bond, were previously found to reduce the viability of human prostate cancer cells most intensively among 15 dietary carotenoids tested. In the present study, the induction of apoptosis in PC-3 cells by these two carotenoids was characterized by morphological changes, DNA fragmentation, an increased percentage of hypodiploid cells, and cleavages of caspase-3 and PARP. The ratio of apoptotic cells reached more than 30% after treatment for 48 h with 20 microM carotenoids. They reduced the expression of Bax and Bcl-2 proteins, but not Bcl-X(L). Fucoxanthin accumulated in the cells at the same level as neoxanthin. Moreover, fucoxanthinol, a deacetylated product of fucoxanthin, formed in the cells treated with fucoxanthin and reached a level comparable to that of fucoxanthin after incubation for 24 h. Treatment by fucoxanthinol alone also induced apoptosis in PC-3 cells. Thus, neoxanthin and fucoxanthin treatments were found to induce apoptosis through caspase-3 activation in PC-3 human prostate cancer cells.

Tomato phytochemicals and prostate cancer risk

Mounting evidence over the past decade suggests that the consumption of fresh and processed tomato products is associated with reduced risk of prostate cancer. The emerging hypothesis is that lycopene, the primary red carotenoid in tomatoes, may be the principle phytochemical responsible for this reduction in risk. A number of potential mechanisms by which lycopene may act have emerged, including serving as an important in vivo antioxidant, enhancing cell-to-cell communication via increasing gap junctions between cells, and modulating cell-cycle progression. Although the effect of lycopene is biologically relevant, the tomato is also an excellent source of nutrients, including folate, vitamin C, and various other carotenoids and phytochemicals, such as polyphenols, which also may be associated with lower cancer risk. Tomatoes also contain significant quantities of potassium, as well as some vitamin A and vitamin E. Our laboratory has been interested in identifying specific components or combination of components in tomatoes that are responsible for reducing prostate cancer risk. We carried out cell culture trials to evaluate the effects of tomato carotenoids and tomato polyphenols on growth of prostate cancer cells. We also evaluated the ability of freeze-dried whole-tomato powder or lycopene alone to reduce growth of prostate tumors in rats. This paper reviews the epidemiological evidence, evaluating the relationship between prostate cancer risk and tomato consumption, and presents experimental data from this and other laboratories that support the hypothesis that whole tomato and its phytochemical components reduce the risk of prostate cancer.

Dietary influences on endocrine-inflammatory interactions in prostate cancer development

Prostate cancer is the most frequently diagnosed non-cutaneous cancer and is the second leading cause of cancer death in American men. The focus of this review is to define the relationship between hormonal (testosterone/estrogens) stimulation of chronic inflammation, generation of reactive oxygen species (ROS), and uncontrolled prostate cell proliferation, and review putative dietary chemoprevention strategies that focus on these processes. It has been proposed that elevated estrogen in men who already have high blood testosterone are at high risk for prostate cancer. We hypothesized that elevated estrogen, in the presence of testosterone, causes prolonged activation of a redox-sensitive transcription factor, nuclear factor kappa B (NF kappa B), that initiates and amplifies an inflammatory cascade within the prostate and results in sustained oxidative and nitrative damage. The inflammatory cascade is proposed to link with uncontrolled proliferation through up-regulated Wnt signal and abnormal catenin accumulation in the prostate. Finally, a strategy that emphasizes a "whole food" based approach to cancer prevention by selecting food products that bear anti-inflammatory and anti-proliferative properties may be most promising as an effective dietary chemopreventive strategy.

Mechanism of activation of caspase cascade during beta-carotene-induced apoptosis in human tumor cells

In this study, we examined possible mechanisms of caspase activation during carotenoid-induced apoptosis in tumor cells. We found that beta-Carotene induces apoptosis by the activation of caspase-3 in human leukemia (HL-60), colon adenocarcinoma (HT-29) as well as melanoma (SK-MEL-2) cell lines. This activation is dose dependent and follows that of caspase-8 and caspase-9. Although caspase-8 cleavage is an early event, reaching its maximum activation at 3 h, caspase-9 reaches its maximum activation only at 6 h. The addition of IETD-CHO, a caspase-8-specific inhibitor, completely prevents beta-Carotene-induced apoptosis, whereas only a partial prevention was observed in the presence of LEHD-CHO, a caspase-9-specific inhibitor. beta-Carotene activates caspase-9 via cytochrome c release from mitochondria and loss of mitochondrial membrane potential (Dym). Concomitantly, a dose-dependent decrease in the antiapoptotic protein Bcl-2 and a dose-dependent increase in the cleaved form of BID (t-BID) are observed. Moreover, NF-kB activation is involved in beta-Carotene-induced caspase cascade. These results support a pharmacological role for beta-Carotene as a candidate antitumor agent and show a possible sequence of molecular events by which this molecule may induce apoptosis in tumor cells.

Beta-carotene and beta-apo-14'-carotenoic acid prevent the reduction of retinoic acid receptor beta in benzo[a]pyrene-treated normal human bronchial epithelial cells

Low-dose beta-carotene (BC) supplementation, such as would be provided by daily consumption of approximately 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 RARbeta, a tumor suppressor, but not RARalpha or RARgamma, was reduced by 50% in the NHBE cells treated with BP. However, treatment with either BC or 14'CA significantly induced the expression of RARbeta in the NHBE cells, and prevented the reduction of RARbeta by BP. Furthermore, 14'CA transactivated the RARbeta 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 RARbeta.

Plasma and Dietary Carotenoids, and the Risk of Prostate Cancer

The association between plasma carotenoids and prostate cancer risk was investigated in a case-control study nested within the prospective Health Professionals Follow-up Study. We matched 450 incident prostate cancer cases diagnosed from 1993-1998 to 450 controls by age, time, month, and year of blood donation. Modest inverse, but not statistically significant, associations were observed among plasma alpha-carotene, beta-carotene, and lycopene concentrations, and overall risk of prostate cancer diagnosis [odds ratio (highest versus lowest quintile; OR), alpha-carotene: OR, 0.67 [95% confidence interval (CI), -0.40-1.09]; beta-carotene: OR, 0.78 (95% CI, 0.48-1.25); lycopene: OR, 0.66 (95% CI, 0.38-1.13)]. The inverse association between plasma lycopene concentrations and prostate cancer risk was limited to participants who were 65 years or older (OR, 0.47; 95% CI, 0.23-0.98) and without a family history of prostate cancer (OR, 0.48; 95% CI, 0.26-0.89). Combining, older age and a negative family history provided similar results (OR, 0.43; 95% CI, 0.18-1.02). Inverse associations between beta-carotene and prostate cancer risk were also found among younger participants (<65 years of age; OR, 0.36; 95% CI, 0.14-0.91; P(trend) = 0.03). Combining dietary intake and plasma data confirmed our results. We found a statistically significant inverse association between higher plasma lycopene concentrations and lower risk of prostate cancer, which was restricted to older participants and those without a family history of prostate cancer. This observation suggests that tomato products may exhibit more potent protection against sporadic prostate cancer rather than those with a stronger familial or hereditary component. In addition, our findings also suggest that among younger men, diets rich in beta-carotene may also play a protective role in prostate carcinogenesis.

Critical review of complementary therapies for prostate cancer

Despite its prominence as the most frequently diagnosed solid tumor among men in the United States, relatively little is known about the etiology of prostate cancer. Furthermore, research into treatment strategies for prostate cancer continues to lag behind research for the other most common cancers. At the same time, however, the popularity of complementary therapies among prostate cancer patients continues to grow. In this article, we provide a critical review of the most recent evidence for dietary modifications, food supplements, and herbs in prostate cancer prevention and treatment. Despite encouraging data for some of these interventions, even the strongest proponents of complementary therapy agree that only randomized controlled trials can provide sufficient evidence on which to create universal guidelines. However, such trials are highly complex and expensive, and they require lengthy follow-up. Until such trials are completed, an opportunity exists for health care professionals to improve their knowledge and understanding of the current evidence for or against complementary therapy in prostate cancer.

The role of nutrition in preventing prostate cancer: a review of the proposed mechanism of action of various dietary substances

BACKGROUND

Dietary modifications to prevent prostate cancer (PCa) continue to gain attention as research demonstrates that various dietary nutrients/supplements are related to decreased risk of developing prostate cancer (PCa). Several studies have focused on the antioxidant and nonantioxidant effects of various dietary substances in the prevention of PCa. Research into the mechanisms by which PCa is prevented, or its disease severity is reduced by dietary micronutrients and vitamins continues to enrich our understanding of the mechanisms by which PCa is initiated and progresses.

METHODS

We reviewed the literature on dietary nutrients with antioxidant properties that have been shown to have a positive effect in reducing the incidence or preventing the occurrence of PCa including carotenoids (e.g., lycopene), retinoids (e.g., vitamin A), vitamin E, vitamin C, selenium, and polyphenols. Other nutrients examined included vitamin D and calcium.

RESULTS

Many dietary micronutrients have demonstrated significant and complex effects on PCa cell proliferation, differentiation, and signaling related to the initiation, progression, and regression of PCa.

CONCLUSION

Understanding the mechanisms by which various dietary nutrients exert their effects on PCa may make it possible to design effective drugs for treating PCa and to promote better nutrition and lifestyle changes in those at risk for PCa.

Tomatoes, lycopene, and prostate cancer: progress and promise

Prostate cancer has emerged as a major public health problem in nations that have an affluent culture with an aging population. The search for etiologic risk factors and an emphasis on the development of chemopreventive agents has gained momentum over the last decade. Among the landmark epidemiologic findings during this period has been the association between the consumption of tomato products and a lower risk of prostate cancer. The traditional reductionist scientific approach has led many investigators to propose that lycopene, a carotenoid consumed largely from tomato products, may be the component responsible for lowering the risk of prostate cancer. Thus, many laboratory and clinical studies are now underway with the goal of assessing the ability of pure lycopene to serve as a chemopreventive agent for prostate and other malignancies. The focus on lycopene should continue, and an improved understanding of lycopene absorption, distribution, role in antioxidant reactions, and metabolism is critical in the quest to elucidate mechanisms whereby this compound could possibly reduce prostate cancer risk. In contrast to the pharmacologic approach with pure lycopene, many nutritional scientists direct their attention upon the diverse array of tomato products as a complex mixture of biologically active phytochemicals that together may have anti-prostate cancer benefits beyond those of any single constituent. These contrasting approaches will continue to be explored in clinical, laboratory and epidemiologic studies in the near future, providing hope that the next generation will benefit from this knowledge and experience a lower risk of prostate cancer.

Evidence that the human gene for prostate short-chain dehydrogenase/reductase (PSDR1) encodes a novel retinal reductase (RalR1)

All-trans-retinoic acid is a metabolite of vitamin A (all-trans-retinol) that functions as an activating ligand for a family of nuclear retinoic acid receptors. The intracellular levels of retinoic acid in tissues are tightly regulated, although the mechanisms underlying the control of retinoid metabolism at the level of specific enzymes are not completely understood. In this report we present the first characterization of the retinoid substrate specificity of a novel short-chain dehydrogenase/reductase (SDR) encoded by RalR1/PSDR1, a cDNA recently isolated from the human prostate (Lin, B., White, J. T., Ferguson, C., Wang, S., Vessella, R., Bumgarner, R., True, L. D., Hood, L., and Nelson, P. S. (2001) Cancer Res. 61, 1611-1618). We demonstrate that RalR1 exhibits an oxidoreductive catalytic activity toward retinoids, but not steroids, with at least an 800-fold lower apparent K(m) values for NADP+ and NADPH versus NAD+ and NADH as cofactors. The enzyme is approximately 50-fold more efficient for the reduction of all-trans-retinal than for the oxidation of all-trans-retinol. Importantly, RalR1 reduces all-trans-retinal in the presence of a 10-fold molar excess of cellular retinol-binding protein type I, which is believed to sequester all-trans-retinal from nonspecific enzymes. As shown by immunostaining of human prostate and LNCaP cells with monoclonal anti-RalR1 antibodies, the enzyme is highly expressed in the epithelial cell layer of human prostate and localizes to the endoplasmic reticulum. The enzymatic properties and expression pattern of RalR1 in prostate epithelium suggest that it might play a role in the regulation of retinoid homeostasis in human prostate.

Acyclic carotenoids and their oxidation mixtures inhibit the growth of HL-60 human promyelocytic leukemia cells

Lycopene has been known as a potential food component for cancer prevention, since tomato consumption was shown to be associated with reduced risk of certain cancers. We used HL-60 cells as a model of cancer cells to investigate whether acyclic carotenoids, such as phytoene, phytofluene, and zeta-carotene present in tomatoes, other than lycopene, as well as oxidation mixtures of these carotenoids, are potentially involved in the cancer-preventive action of tomatoes. When HL-60 cells were grown in the carotenoid-supplemented medium for 120 hours, zeta-carotene and phytofluene at 10 microM inhibited cell growth to 3.7% and 22.6% of the growth in control culture, respectively, although they were extremely unstable in the culture medium. The oxidation mixture of each carotenoid, which was prepared by incubation in toluene at 37 degrees C for 24 hours, more strongly inhibited cell growth than each intact carotenoid. The growth inhibition by lycopene was remarkably enhanced by its oxidation before supplementation to the medium. Phytofluene, zeta-carotene, and the oxidation mixture of lycopene induced apoptosis in HL-60 cells during incubation for 24 hours. The addition of alpha-tocopherol to the medium did not eliminate growth inhibition by the oxidation mixture of lycopene. These results suggest that the acyclic carotenoids inhibit cell growth through apoptosis induction and that oxidation products of the carotenoids participate in the growth inhibition.

Regulation of cell cycle progression and apoptosis by beta-carotene in undifferentiated and differentiated HL-60 leukemia cells: possible involvement of a redox mechanism

Although epidemiologic studies have demonstrated that a high intake of vegetables containing beta-carotene lowers the risk of cancer, recent intervention studies have revealed that beta-carotene supplementation to smokers resulted in a high incidence of lung cancer. We hypothesized that beta-carotene may act as a pro- or anticancerogenic agent by modulating pathways involved in cell growth and that such a modulation may involve a redox mechanism. To test this hypothesis, cell proliferation, apoptosis and redox status were evaluated in undifferentiated and dimethylsulfoxide-differentiated HL-60 cells exposed to beta-carotene. The carotenoid modified cell cycle progression and induced apoptosis in a dose-dependent manner. These effects were more remarkable in undifferentiated cells than in differentiated cells. In accord with these findings, in undifferentiated cells, beta-carotene was more effective in decreasing cyclin A and Bcl-2 expression and in increasing p21 and p27 expression. Neither Bcl-xL nor Bax expression were significantly modified by the carotenoid. From a mechanistic point of view, the delay in cell growth by beta-carotene was highly coincident with the increased intracellular reactive oxygen species production and oxidized glutathione content induced by the carotenoid. Moreover, alpha-tocopherol minimized the effects of beta-carotene on cell growth. These data provide evidence that beta-carotene modulates molecular pathways involved in cell cycle progression and apoptosis and support the hypothesis that a redox mechanism may be implicated. They also suggest that differentiated cells may be less susceptible to the carotenoid than highly neoplastic undifferentiated cells.

Beta-carotene inhibits growth of human colon carcinoma cells in vitro by induction of apoptosis

Epidemiological studies suggest that beta-carotene is able to modulate the risk of cancer. A number of in vitro studies reported that beta-carotene inhibits the growth of cancer cells; however, so far little is known about the molecular mechanisms of the antiproliferative effect of beta-carotene. Here we have investigated the effects of two beta-carotene preparations, (i) beta-carotene dissolved in tetrahydrofuran (final concentration in cell culture medium: 0.5%) and (ii) beta-carotene incorporated in a water dispersible bead form, on cultured human colon carcinoma cells HT29. The treatment of cells with beta-carotene up to 30 microM for 72 h led to a significant increase in the cellular beta-carotene concentration and formation of retinol. Beta-Carotene showed only low cytotoxicity for confluent cells tested up to 30 microM, but at dietary relevant concentrations for the intestinal tract (10, 30 microM) beta-carotene was strongly cytotoxic for growing cells and induced apoptosis in HT29 cells as assessed by the Annexin-V assay (the maximal effect was observed 15 h after treatment with beta-carotene). Exposure of cells to retinol at concentrations yielding cellular retinol levels similar to those observed by beta-carotene treatment had no antiproliferative or cytotoxic effect. Furthermore, beta-carotene did not affect the activation of the extracellular signal-regulated kinases (ERK1 and ERK2) that are essential for cellular growth. In summary, beta-carotene can inhibit growth of human colon carcinoma cells in vitro by induction of apoptosis in proliferating cells.

Carotenoids affect proliferation of human prostate cancer cells

We investigated whether various carotenoids present in foodstuffs were potentially involved in cancer-preventing action on human prostate cancer. The effects of 15 kinds of carotenoids on the viability of three lines of human prostate cancer cells, PC-3, DU 145 and LNCaP, were evaluated. When the prostate cancer cells were cultured in a carotenoid-supplemented medium for 72 h at 20 micromol/L, 5,6-monoepoxy carotenoids, namely, neoxanthin from spinach and fucoxanthin from brown algae, significantly reduced cell viability to 10.9 and 14.9% for PC-3, 15.0 and 5.0% for DU 145, and nearly zero and 9.8% for LNCaP, respectively. Acyclic carotenoids such as phytofluene, zeta-carotene and lycopene, all of which are present in tomato, also significantly reduced cell viability. On the other hand, phytoene, canthaxanthin, beta-cryptoxanthin and zeaxanthin did not affect the growth of the prostate cancer cells. DNA fragmentation of nuclei in neoxanthin- and fucoxanthin-treated cells was detected by in situ TdT-mediated dUTP nick end labeling (TUNEL) assay. Neoxanthin and fucoxanthin were found to reduce cell viability through apoptosis induction in the human prostate cancer cells. These results suggest that ingestion of leafy green vegetables and edible brown algae rich in neoxanthin and fucoxanthin might have the potential to reduce the risk of prostate cancer.

N-(4-hydroxyphenyl)retinamide (4-HPR) decreases neoplastic properties of human prostate cells: an agent for prevention

The development of prostate cancer through a multistep process of carcinogenesis may have a long latent period of 20-30 years. It is possible that progression to a malignant state could be blocked or reversed during this time. This study focuses on the ability of the synthetic retinoid, N-(4-hydroxyphenyl)-retinamide (4-HPR), to reverse changes associated with malignant transformation and tumor progression, towards a normal phenotype. To examine the responsiveness of cells at different steps of prostate carcinogenesis, three immortalized, but non-tumorigenic (RWPE-1, WPE1-7 and WPE1-10), and one human prostate carcinoma cell line (DU-145), were used. The effects of 4-HPR on cell proliferation, expression of intermediate filament proteins cytokeratin 18 and vimentin, and tumor suppressor proteins p53 and pRb were examined by immunostaining and compared. Results show that 4-HPR caused inhibition of growth in all cell lines in a dose-dependent manner. 4-HPR induced an increase in staining for cytokeratin 18, a marker of differentiation for prostate epithelial cells. While all cell lines showed strong immunostaining for vimentin, treatment with 4-HPR for 8 days caused a marked decrease in staining for vimentin in all cell lines. In an in vitro assay, 4-HPR also caused inhibition of invasion by DU-145 cells in a dose-dependent manner. Furthermore, 4-HPR treatment was effective in significantly decreasing the abnormal nuclear staining for the tumor suppressor proteins p53 and pRb. Because 4-HPR decreased invasion-associated vimentin expression, inhibited invasion, and normalized p53 and pRb immunostaining, we propose that 4-HPR may be an effective agent for secondary and tertiary prevention, i.e. promotion and progression stages, respectively, of prostate cancer.

beta-carotene at high concentrations induces apoptosis by enhancing oxy-radical production in human adenocarcinoma cells

This is the first report demonstrating a relationship between apoptosis induction and changes of intracellular redox potential in the growth-inhibitory effects of high concentrations of beta-carotene in a tumor cell line. beta-Carotene inhibited the growth of human WiDr colon adenocarcinoma cells in a dose- and time-dependent manner, induced apoptosis, and blocked Bcl-2 expression. These effects were accompanied by an enhanced production of intracellular reactive oxygen species (ROS). The addition of the antioxidant alpha-tocopherol blocked both the pro-oxidant and the growth-inhibitory effects of the carotenoid. These findings suggest that beta-carotene may act as an inductor of apoptosis by its pro-oxidant properties.

beta-Carotene stability and uptake by prostate cancer cells are dependent on delivery vehicle

Cell culture systems provide an opportunity to evaluate the effects of carotenoids on molecular and cellular processes involved in proliferation and differentiation of prostate cancer cells. The stability and cellular uptake of beta-carotene (BC) by prostate cancer cells were investigated in vitro by use of various delivery methods and three human prostate adenocarcinoma cell lines: PC-3, DU 145, and LNCaP. Recovery of BC from the media (prepared from water-dispersible BC beadlets) significantly (p < 0.05) decreased after 12 hours in culture and continued to significantly decrease (p < 0.05) after 24, 48, 72, and 96 hours, an observation primarily attributed to BC degradation rather than isomerization, metabolism, or cellular uptake. The uptake of BC by prostate cancer cells was compared when delivered by tetrahydrofuran, BC-enriched bovine serum, water-dispersible BC beadlets, and artificial liposomes. Recovery of BC after three days in culture from enriched bovine serum medium was significantly (p < 0.05) greater than recovery from medium prepared by beadlets, tetrahydrofuran, or artificial liposomes. We conclude that BC is relatively unstable in vitro and that degradation products may contribute to biological responses. Furthermore, our studies indicate that enriched bovine serum provides a stable and physiological approach to carotenoid treatment of cells in culture.