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Prostate Health

April 2009

Vitamin D and sunlight: strategies for cancer prevention and other health benefits.

Vitamin D deficiency is a worldwide health problem. The major source of vitamin D for most humans is sensible sun exposure. Factors that influence cutaneous vitamin D production include sunscreen use, skin pigmentation, time of day, season of the year, latitude, and aging. Serum 25-hydroxyvitamin D [25(OH)D] is the measure for vitamin D status. A total of 100 IU of vitamin D raises blood level of 25(OH)D by 1 ng/mL. Thus, children and adults who do not receive adequate vitamin D from sun exposure need at least 1000 IU/D vitamin D. Lack of sun exposure and vitamin D deficiency have been linked to many serious chronic diseases, including autoimmune diseases, infectious diseases, cardiovascular disease, and deadly cancers. It is estimated that there is a 30 to 50% reduction in risk for developing colorectal, breast, and prostate cancer by either increasing vitamin D intake to least 1,000 IU/D vitamin D or increasing sun exposure to raise blood levels of 25(OH)D >30 ng/mL. Most tissues in the body have a vitamin D receptor. The active form of vitamin D, 1,25-dihydroxyvitamin D, is made in many different tissues, including colon, prostate, and breast. It is believed that the local production of 1,25(OH)(2)D may be responsible for the anticancer benefit of vitamin D. Recent studies suggested that women who are vitamin D deficient have a 253% increased risk for developing colorectal cancer, and women who ingested 1,500 mg/d calcium and 1,100 IU/D vitamin D(3) for 4 yr reduced risk for developing cancer by >60%.

Clin J Am Soc Nephrol. 2008 Sep;3(5):1548-54

Dietary intake of n-3 and n-6 fatty acids and the risk of prostate cancer.

BACKGROUND: Laboratory studies have shown that n-3 fatty acids inhibit and n-6 fatty acids stimulate prostate tumor growth, but whether the dietary intake of these fatty acids affects prostate cancer risk in humans remains unclear. OBJECTIVE: We prospectively evaluated the association between intakes of alpha-linolenic (ALA; 18:3n-3), eicosapentaenoic (EPA; 20:5n-3), docosahexaenoic (DHA; 22:6n-3), linoleic (LA; 18:2n-6), and arachidonic (AA; 20:4n-6) acids and prostate cancer risk. DESIGN: A cohort of 47,866 US men aged 40-75 y with no cancer history in 1986 was followed for 14 y. RESULTS: During follow-up, 2,965 new cases of total prostate cancer were ascertained, 448 of which were advanced prostate cancer. ALA intake was unrelated to the risk of total prostate cancer. In contrast, the multivariate relative risks (RRs) of advanced prostate cancer from comparisons of extreme quintiles of ALA from nonanimal sources and ALA from meat and dairy sources were 2.02 (95% CI: 1.35, 3.03) and 1.53 (0.88, 2.66), respectively. EPA and DHA intakes were related to lower prostate cancer risk. The multivariate RRs of total and advanced prostate cancer from comparisons of extreme quintiles of the combination of EPA and DHA were 0.89 (0.77, 1.04) and 0.74 (0.49, 1.08), respectively. LA and AA intakes were unrelated to the risk of prostate cancer. The multivariate RR of advanced prostate cancer from a comparison of extreme quintiles of the ratio of LA to ALA was 0.62 (0.45, 0.86). CONCLUSIONS: Increased dietary intakes of ALA may increase the risk of advanced prostate cancer. In contrast, EPA and DHA intakes may reduce the risk of total and advanced prostate cancer.

Am J Clin Nutr. 2004 Jul;80(1):204-16

Cyclooxygenase-2 and cyclooxygenase-2 inhibitors in prostate cancer

Cyclooxygenase-2 (Cox-2) is over-expressed in prostate cancer (PCa) and involved in its development and progression by facilitating inflammatory response, reducing cell apoptosis, increasing angiogenesis and damaging DNA oxidation. Selective Cox-2 inhibitors suppress PCa growth through various channels and therefore have a promising application value in the management of prostate cancer.

Zhonghua Nan Ke Xue. 2008 Nov;14(11):1031-4

Multi-targeted prevention of cancer by sulforaphane.

Isothiocyanates are found in cruciferous vegetables such as broccoli, Brussels sprouts, cauliflower, and cabbage. Epidemiologic studies suggest that cruciferous vegetable intake may lower overall cancer risk, including colon and prostate cancer. Sulforaphane (SFN) is an isothiocyanate found in cruciferous vegetables and is especially high in broccoli and broccoli sprouts. SFN has proved to be an effective chemoprotective agent in cell culture, carcinogen-induced and genetic animal cancer models, as well as in xenograft models of cancer. Early research focused on the “blocking activity” of SFN via Phase 2 enzyme induction, as well as inhibition of enzymes involved in carcinogen activation, but there has been growing interest in other mechanisms of chemoprotection by SFN. Recent studies suggest that SFN offers protection against tumor development during the “post-initiation” phase and mechanisms for suppression effects of SFN, including cell cycle arrest and apoptosis induction are of particular interest. In humans, a key factor in determining the efficacy of SFN as a chemoprevention agent is gaining an understanding of the metabolism, distribution and bioavailability of SFN and the factors that alter these parameters. This review discusses the established anti-cancer properties of SFN, with an emphasis on the possible chemoprevention mechanisms. The current status of SFN in human clinical trials also is included, with consideration of the chemistry, metabolism, absorption and factors influencing SFN bioavailability.

Cancer Lett. 2008 Oct 8;269(2):291-304

Serum alpha-tocopherol and gamma-tocopherol in relation to prostate cancer risk in a prospective study.

The Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study demonstrated a 32% reduction in prostate cancer incidence in response to daily alpha-tocopherol supplementation. We examined baseline serum concentrations of alpha-tocopherol and gamma-tocopherol to compare their respective associations with prostate cancer risk. From the ATBC Study cohort of 29,133 Finnish men, 50-69 years old, we randomly selected 100 incident prostate cancer case patients and matched 200 control subjects. Odds ratios and 95% confidence intervals (CIs) were estimated for the serum tocopherols (measured by high-performance liquid chromatography) using logistic regression models. All P values were two-sided. Odds ratios for the highest versus the lowest tertiles were 0.49 (95% CI = 0.24 to 1.01, P(trend) = .05) for alpha-tocopherol and 0.57 (95% CI = 0.31 to 1.06, P(trend) = .08) for gamma-tocopherol. Further analyses indicated that the association of high serum tocopherols with low prostate cancer risk was stronger in the alpha-tocopherol-supplemented group than in those not receiving alpha-tocopherol. Participants with higher circulating concentrations of the major vitamin E fractions, alpha-tocopherol and gamma-tocopherol, had similarly lower prostate cancer risk.

J Natl Cancer Inst. 2005 Mar 2;97(5):396-9

The effect of alpha- and gamma-tocopherol and their carboxyethyl hydroxychroman metabolites on prostate cancer cell proliferation.

It is known that gamma-tocopherol inhibits human prostate cancer cell proliferation via down-regulation of cyclin-related signalling but tocopherol and tocotrienol metabolites with a shortened phytyl chain, carboxyethyl hydroxychromans, were not previously investigated as anti-proliferative agents. In this study, the effect of the two main tocopherols, namely, alpha-tocopherol and gamma-tocopherol, and their corresponding metabolites (alpha- and gamma-carboxyethyl hydroxychromans) was studied on proliferation and cyclin D1 expression of the prostate cancer cell line PC-3. The hydrosoluble vitamin E analogues Trolox and alpha-tocopherol succinate were also tested. The most effective inhibitors of PC-3 proliferation were gamma-tocopherol and gamma-carboxyethyl hydroxychroman. Their effect was discernable at 1 microM and reached a plateau at concentrations > or = 10 microM with maximal inhibition values ranging between 70 and 82%. alpha-Tocopherol, alpha-carboxyethyl hydroxychroman, and the analogue Trolox were much less effective; a weak effect was observed for concentrations < or = 10 microM and a maximal inhibition of less than 45% was found at 50 microM concentration. PC-3 cells showed higher inhibition, particularly by the gamma derivatives, than HTB-82 and HECV cells. Tocopherols and carboxyethyl hydroxychromans exerted an inhibitory effect on cyclin D1 expression parallel to the retardation of cell growth. gamma-Carboxyethyl hydroxychroman and gamma-tocopherol showed effects also upstream of the cyclin modulation. Furthermore, the inhibition of cyclin D1 expression by gamma-carboxyethyl hydroxychroman was competed for by alpha-carboxyethyl hydroxychroman. In conclusion, this study shows that carboxyethyl hydroxychroman metabolites are as effective as their vitamin precursors to inhibit PC-3 growth by specific down-regulation of cyclin expression, with the gamma forms being the most effective ones. Although the inhibition of PC-3 cell growth and diminution of cyclin expression are clearly visible, more subtle mechanistic effects of tocopherols and their corresponding carboxyethyl hydroxychroman metabolites deserve further investigations.

Arch Biochem Biophys. 2004 Mar 1;423(1):97-102

Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT).

CONTEXT: Secondary analyses of 2 randomized controlled trials and supportive epidemiologic and preclinical data indicated the potential of selenium and vitamin E for preventing prostate cancer. OBJECTIVE: To determine whether selenium, vitamin E, or both could prevent prostate cancer and other diseases with little or no toxicity in relatively healthy men. DESIGN, SETTING, AND PARTICIPANTS: A randomized, placebo-controlled trial (Selenium and Vitamin E Cancer Prevention Trial [SELECT]) of 35,533 men from 427 participating sites in the United States, Canada, and Puerto Rico randomly assigned to 4 groups (selenium, vitamin E, selenium + vitamin E, and placebo) in a double-blind fashion between August 22, 2001, and June 24, 2004. Baseline eligibility included age 50 years or older (African American men) or 55 years or older (all other men), a serum prostate-specific antigen level of 4 ng/mL or less, and a digital rectal examination not suspicious for prostate cancer. INTERVENTIONS: Oral selenium (200 microg/d from L-selenomethionine) and matched vitamin E placebo, vitamin E (400 IU/d of all rac-alpha-tocopheryl acetate) and matched selenium placebo, selenium + vitamin E, or placebo + placebo for a planned follow-up of minimum of 7 years and a maximum of 12 years. MAIN OUTCOME MEASURES: Prostate cancer and prespecified secondary outcomes, including lung, colorectal, and overall primary cancer. RESULTS: As of October 23, 2008, median overall follow-up was 5.46 years (range, 4.17-7.33 years). Hazard ratios (99% confidence intervals [CIs]) for prostate cancer were 1.13 (99% CI, 0.95-1.35; n = 473) for vitamin E, 1.04 (99% CI, 0.87-1.24; n = 432) for selenium, and 1.05 (99% CI, 0.88-1.25; n = 437) for selenium + vitamin E vs 1.00 (n = 416) for placebo. There were no significant differences (all P>.15) in any other prespecified cancer end points. There were statistically nonsignificant increased risks of prostate cancer in the vitamin E group (P = .06) and type 2 diabetes mellitus in the selenium group (relative risk, 1.07; 99% CI, 0.94-1.22; P = .16) but not in the selenium + vitamin E group. CONCLUSION: Selenium or vitamin E, alone or in combination at the doses and formulations used, did not prevent prostate cancer in this population of relatively healthy men.

JAMA. 2009 Jan 7;301(1):39-51

The association of fatty acids with prostate cancer risk.

BACKGROUND: Animal studies indicate that omega-6 fatty acids promote and omega-3 fatty acids inhibit tumor development. This pilot study was designed to evaluate whether these fatty acids are associated with human prostate cancer. METHODS: Levels of erythrocyte membrane omega-3 and omega-6 fatty acids were determined for 67 incident prostate cancer cases and 156 population-based controls. RESULTS: Prostate cancer risk was increased in the highest compared to the lowest quartile of alpha-linolenic acid (OR = 2.6, 95% CI = 1.1-5.8, trend P = 0.01). Positive associations were also observed with higher levels of linoleic acid (OR = 2.1, 95% CI = 0.9-4.8) and total omega-6 fatty acids (OR = 2.3, 95% CI = 1.0-5.4). CONCLUSIONS: Results are consistent with other studies showing that linoleic and total omega-6 fatty acids increase risk of prostate cancer. Contrary to animal studies, alpha-linolenic acid was also positively associated with risk. Further research will be required to clarify the role of these fatty acids in human prostate cancer.

Prostate. 2001 Jun 1;47(4):262-8

Involvement of arachidonic acid metabolism and EGF receptor in neurotensin-induced prostate cancer PC3 cell growth.

Dietary fats, which increase the risk of prostate cancer, stimulate release of intestinal neurotensin (NT), a growth-promoting peptide that enhances the formation of arachidonic acid metabolites in animal blood. This led us to use PC3 cells to examine the involvement of lipoxygenase (LOX) and cyclooxygenase (COX) in the growth effects of NT, including activation of EGF receptor (EGFR) and downstream kinases (ERK, AKT), and stimulation of DNA synthesis. NT and EGF enhanced [3H]-AA release, which was diminished by inhibitors of PLA2 (quinacrine), EGFR (AG1478) and MEK (U0126). NT and EGF phosphorylated EGFR, ERK and AKT, and stimulated DNA synthesis. These effects were diminished by PLA2 inhibitor (quinacrine), general LOX inhibitors (NDGA, ETYA), 5-LOX inhibitors (Rev 5901, AA861), 12-LOX inhibitor (baicalein) and FLAP inhibitor (MK886), while COX inhibitor (indomethacin) was without effect. Cells treated with NT and EGF showed an increase in 5-HETE levels by HPLC. PKC inhibitor (bisindolylmaleimide) blocked the stimulatory effects of NT, EGF and 5-HETE on DNA synthesis. We propose that 5-LOX activity is required for NT to stimulate growth via EGFR and its downstream kinases. The mechanism may involve an effect of 5-HETE on PKC, which is known to facilitate MEK-ERK activation. NT may enhance 5-HETE formation by Ca2+-mediated and ERK-mediated activation of DAG lipase and cPLA2. NT also upregulates cPLA2 and 5-LOX protein expression. Thus, the growth effects of NT and EGF involve a feed-forward system that requires cooperative interactions of the 5-LOX, ERK and AKT pathways.

Regul Pept. 2006 Jan 15;133(1-3):105-14

Activation of the orphan nuclear receptor RORalpha counteracts the proliferative effect of fatty acids on prostate cancer cells: crucial role of 5-lipoxygenase.

The incidence of prostate carcinoma is very low in Eastern countries, such as Japan, suggesting that life style conditions may play a crucial role in the development of this pathology. Dietary omega-6 polyunsaturated fatty acids, such as linoleic (LA) and arachidonic (AA) acids, have been shown to stimulate the proliferation of prostate cancer cells after being converted into 5-HETE by means of the 5-lipoxygenase (5-LOX) pathway. Blockade of 5-LOX activity has been proposed as an attractive target for the prevention of the mitogenic action of dietary fats on prostate cancer. The 5-LOX gene has been shown to carry a response element for the orphan nuclear receptor RORalpha (for its RORalpha1 isoform in particular) in its promoter region. We attempt to clarify whether activation of RORalpha might modulate the expression of 5-LOX, thus interfering with the mitogenic activity of fatty acids in prostate cancer cells. We show that in androgen-independent DU 145 prostate cancer cells, LA, AA and their metabolite 5-HETE exert a strong stimulatory action on cell proliferation. This effect is completely counteracted by the simultaneous treatment of the cells with a non redox inhibitor of 5-LOX activity. We then demonstrate that: i) RORalpha, and specifically its RORalpha1 isoform, is expressed in DU 145 cells; ii) activation of RORalpha, by means of the thiazolidinedione derivative CGP 52,608 (the synthetic RORalpha activator), significantly reduces 5-LOX expression, both at mRNA (as evaluated by comparative RT-PCR) and at protein (as investigated by Western blot analysis) level (this was confirmed by the reduced activity of 5-LOX in CGP 52,608 treated cells); and iii) the treatment of DU 145 cells with CGP 52,608 completely abrogated the proliferative action of both LA and AA. These results have been confirmed in another androgen-independent prostate cancer cell line (PC3). Our data indicate that, by decreasing the expression of 5-LOX, activation of RORalpha might interfere with the mitogenic activity of fatty acids on prostate cancer. We have shown previously that CGP 52,608 reduces the proliferation and the metastatic behavior of DU 145 cells. These observations indicate that the orphan nuclear receptor RORalpha might be considered as a molecular target for the development of new chemopreventive or chemotherapeutic strategies for prostate carcinoma.

Int J Cancer. 2004 Oct 20;112(1):87-93

Arachidonic acid stimulates prostate cancer cell growth: critical role of 5-lipoxygenase.

Arachidonic acid (5,8,11,14-eicosatetraenoic acid), a member of the omega-6 poly-unsaturated fatty acids, was found to be an effective stimulator of human prostate cancer cell growth in vitro at micromolar concentrations. Selective blockade of the different metabolic pathways of arachidonic acid (e.g. ibuprofen for cyclooxygenase, SKF-525A for cytochrome P-450, baicalein and BHPP for 12-lipoxygenase, AA861 and MK886 for 5-lipoxygenase, etc.) revealed that the growth stimulatory effect of arachidonic acid is inhibited by the 5-lipoxygenase specific inhibitors, AA861 and MK886, but not by others. Addition of the eicosatetraenoid products of 5-lipoxygenase (5-HETEs) showed stimulation of prostate cancer cell growth similar to that of arachidonic acid, whereas the leukotrienes were ineffective. Moreover, the 5-series of eicosatetraenoids could reverse the growth inhibitory effect of MK886. Finally, prostate cancer cells fed with arachidonic acid showed a dramatic increase in the production of 5-HETEs which is effectively blocked by MK886. These experimental observations suggest that arachidonic acid needs to be metabolized through the 5-lipoxygenase pathway to produce 5-HETE series of eicosatetraenoids for its growth stimulatory effects on human prostate cancer cells.

Biochem Biophys Res Commun. 1997 Jun 18;235(2):418-23

Elevated 12-lipoxygenase mRNA expression correlates with advanced stage and poor differentiation of human prostate cancer.

OBJECTIVES. Prostate cancer is the most frequently diagnosed cancer and the second leading cause of cancer death in males in the United States. The mortality is due mainly to distant metastasis. Therefore, predicting the prognosis of prostate cancer patients is an important clinical problem. Previously, we demonstrated that a 12-lipoxygenase (12-LOX) metabolite of arachidonic acid, 12(S)-hydroxyeicosatetraenoic acid, enhances the invasiveness of prostate cancer cells and that a 12-LOX-selective inhibitor [N-benzyl-N-hydroxy-5-phenylpentanamide] reduces experimental metastasis in animal model systems. In this study, we investigated the potential of 12-LOX as a predictor for the aggressiveness of prostate cancer. METHODS. The mRNA expression level of 12-LOX in 122 matching prostate normal and cancerous tissues were measured by quantitative reverse transcription- polymerase chain reaction. Possible association between 12-LOX expression and histologic grade, pathologic and clinical stage, margin positivity, age, and race was analyzed. RESULTS. 12-LOX mRNA levels were elevated in cancer cells and the expression associated with poor differentiation and invasiveness of prostate cancer. Overall, 46 (38%) of 122 evaluable patients showed elevated levels of 12-LOX mRNA in prostate cancer tissues compared with the matching normal tissues. A statistically significantly greater number of cases were found to have an elevated level of 12-LOX among T3, high grade, and surgical margin-positive than T2, intermediate, and low grade, and surgical margin-negative prostatic adenocarcinomas. CONCLUSIONS. Our data suggest that elevation of 12-LOX mRNA expression occurs more frequently in advanced stage, high-grade prostate cancer and that 12-LOX may serve as an indicator for progression and prognosis of prostate cancer. This enzyme also may be a novel target for the development of anti-invasive and antimetastatic agents.

Urology. 1995 Aug;46(2):227-37