Fish consumption and prostate cancer risk: a review and meta-analysis

Fish intake and the risk of brain tumor: a meta-analysis with systematic review

Background

Fish, rich in ω-3 polyunsaturated fatty acids, has been found to be associated with lower risk of several types of cancer risk, and beneficial for brain development. However, the association between fish intake and brain tumor risk is still inconsistent. Therefore, we conducted a meta-analysis to clarify the association.

Methods

Relevant studies were identified from PubMed and EMBASE databases. The pooled relative risks were obtained by the fixed-effects model when no substantial heterogeneity was observed. Otherwise, the random-effects model was employed. Subgroup and publication bias analyses were also performed.

Results

Nine observational studies were included in the meta-analysis. The pooled relative risk of brain cancer for the highest vs. lowest category of fish intake was 0.83 (95% confidence interval [CI]: 0.70–0.99). No significant heterogeneity was detected. Dose-response analysis showed that the RR per 100 g/day increase in fish intake was 0.95 (95% CI: 0.91–0.98). The results remained unchanged in subgroup and sensitivity analyses.

Conclusions

The results of our meta-analysis suggest that fish intake might be associated with lower risk of brain cancer risk. The finding should be further confirmed by future cohort studies with validated questionnaires and strict control of confounders.

Electronic supplementary material

The online version of this article (doi:10.1186/s12937-016-0223-4) contains supplementary material, which is available to authorized users.

Fish consumption and prostate cancer risk and mortality in a Danish cohort study

Within the Danish 'Diet, Cancer and Health' cohort, we aimed to investigate the association between prediagnostic fish intake (total, lean, fatty) and (a) incidence of total and high-grade prostate cancer and (b) the risk of all-cause and prostate cancer-specific mortality among men with prostate cancer. Among 27 178 men, 1690 prostate cancer cases were identified through 2012. Of these, 1042 had a Gleason score of 7 or above and 498 had a Gleason score of 8 or above at the time of diagnosis; 364 died (n=228 from prostate cancer) during follow-up through 2013. Cox proportional hazard models were used for the statistical analyses. No association between any type of fish intake and risk of total prostate cancer or high-grade prostate cancer (Gleason score≥7 or ≥8) was found. For all-cause mortality, we found no association for any type of fish intake. For prostate cancer-specific mortality, only a higher intake of fatty fish was associated with a higher mortality [per daily 25 g increment in intake (mortality rate ratio=1.27; 95% confidence interval: 1.04-1.55; P=0.02)]. In conclusion, no strong association was found between fish consumption and the risk of or mortality from prostate cancer. Only a higher intake of fatty fish was associated with a higher risk of prostate cancer-specific mortality.

Diet, Lifestyles, Family History, and Prostate Cancer Incidence in an East Algerian Patient Group

Prostate cancer (PC) is the fourth most common cancer in men and the sixth leading cause of death in Algeria. To examine the relationship between lifestyle factors, including diet, and family history and PC risk, a case-control study was performed in an eastern Algerian population, comprising 90 patients with histologically confirmed PC and 190 controls. Data collection was carried out through a structured questionnaire and statistical analysis was performed to evaluate the different variables. The data showed that consumption of lamb and beef meat and high intake of animal fat and dairy products increased PC risk. Seven to thirteen vegetables servings per week and fourteen or more servings decreased PC risk by 62% and 96%, respectively. Seven to fourteen fruit servings per week decrease PC risk by 98%. Green tea consumption reduced the risk of PC but the results were statistically borderline. Increased risk was observed for individuals with family history of PC in first and in second degree. A positive strong association was also found for alcohol and smoking intake and a dose-response relationship existed for quantity and history of smoking. This study suggests that dietary habits, lifestyle factors, and family history have influence on the development of PC in Algerian population.

Prostate cancer progression and mortality: a review of diet and lifestyle factors

PURPOSE

To review and summarize evidence on the role of diet and lifestyle factors and prostate cancer progression, with a specific focus on habits after diagnosis and the risk of subsequent disease recurrence, progression, or death.

METHODS

Given the well-documented heterogeneity of prostate cancer and the long survivorship of the majority of diagnoses, our goal was to summarize and describe modifiable risk factors for clinically relevant prostate cancer. We focused where possible on epidemiologic studies of post-diagnostic habits and prostate cancer progression, defined as recurrence (e.g., PSA risk, secondary treatment), metastasis, or death. Where data were limited, we also describe evidence on risk factors and indicators of prostate cancer aggressiveness at diagnosis.

RESULTS

A variety of dietary and lifestyle factors appear to affect prostate cancer progression. Several generally widely recommended lifestyle factors such as not smoking, maintaining a healthy body weight, and regular vigorous physical exercise also appear to affect prostate cancer progression. Several dietary factors, such as tomato sauce/lycopene, cruciferous vegetables, healthy sources of vegetable fats, and coffee, may also have a role in reducing risk of prostate cancer progression.

CONCLUSION

Diet and lifestyle factors, in particular exercise and smoking cessation, may reduce the risk of prostate cancer progression and death. These promising findings warrant further investigation, as their overall impact might be large.

Omega-3 polyunsaturated fatty acids and cancer: lessons learned from clinical trials

Over the past decades, extensive studies have addressed the therapeutic effects of omega-3 polyunsaturated fatty acids (omega-3 FAs) against different human diseases such as cardiovascular and neurodegenerative diseases, cancer, etc. A growing body of scientific research shows the pharmacokinetic information and safety of these natural occurring substances. Moreover, during recent years, a plethora of studies has demonstrated that omega-3 FAs possess therapeutic role against certain types of cancer. It is also known that omega-3 FAs can improve efficacy and tolerability of chemotherapy. Previous reports showed that suppression of nuclear factor-κB, activation of AMPK/SIRT1, modulation of cyclooxygenase (COX) activity, and up-regulation of novel anti-inflammatory lipid mediators such as protectins, maresins, and resolvins, are the main mechanisms of antineoplastic effect of omega-3 FAs. In this review, we have collected the available clinical data on the therapeutic role of omega-3 FAs against breast cancer, colorectal cancer, leukemia, gastric cancer, pancreatic cancer, esophageal cancer, prostate cancer, lung cancer, head and neck cancer, as well as cancer cachexia. We also discussed the chemistry, dietary source, and bioavailability of omega-3 FAs, and the potential molecular mechanisms of anticancer and adverse effects.

Associations between unprocessed red and processed meat, poultry, seafood and egg intake and the risk of prostate cancer: A pooled analysis of 15 prospective cohort studies

Reports relating meat intake to prostate cancer risk are inconsistent. Associations between these dietary factors and prostate cancer were examined in a consortium of 15 cohort studies. During follow-up, 52,683 incident prostate cancer cases, including 4,924 advanced cases, were identified among 842,149 men. Cox proportional hazard models were used to calculate study-specific relative risks (RR) and then pooled using random effects models. Results do not support a substantial effect of total red, unprocessed red and processed meat for all prostate cancer outcomes, except for a modest positive association for tumors identified as advanced stage at diagnosis (advanced(r)). For seafood, no substantial effect was observed for prostate cancer regardless of stage or grade. Poultry intake was inversely associated with risk of advanced and fatal cancers (pooled multivariable RR [MVRR], 95% confidence interval, comparing ≥ 45 vs. <5 g/day: advanced 0.83, 0.70-0.99; trend test p value 0.29), fatal, 0.69, 0.59-0.82, trend test p value 0.16). Participants who ate ≥ 25 versus <5 g/day of eggs (1 egg ∼ 50 g) had a significant 14% increased risk of advanced and fatal cancers (advanced 1.14, 1.01-1.28, trend test p value 0.01; fatal 1.14, 1.00-1.30, trend test p value 0.01). When associations were analyzed separately by geographical region (North America vs. other continents), positive associations between unprocessed red meat and egg intake, and inverse associations between poultry intake and advanced, advanced(r) and fatal cancers were limited to North American studies. However, differences were only statistically significant for eggs. Observed differences in associations by geographical region warrant further investigation.

Maternal dietary supplementation with omega-3 polyunsaturated fatty acids confers neuroprotection to the newborn against hypoxia-induced dopamine dysfunction

INTRODUCTION

Up to 84% of prematurely born infants suffer hypoxic, anoxic, and ischemic insults. Those infants with subsequent behavioral, motor or cognitive dysfunction represent 8-11% of all live births. Yet, no interventions employed during pregnancy attenuate risk of morbidity in those at-risk infants. Dietary supplementation with omega-3 polyunsaturated fatty acids (ω-3 PUFAs) has been shown to reduce stroke-induced neuropathology in rat models emulating this adverse clinical event. To extend those studies we sought to determine whether maternal dietary supplementation with ω-3 PUFAs would confer neuroprotection against hypoxia-induced neurochemical dysfunction in newborn rat pups exposed to repetitive hypoxic insults.

METHODS

We provided pregnant rats with either a ω-3 PUFA enriched diet or else a standard rat chow diet. At postnatal day 7, pups were assigned randomly to either repetitive hypoxic insults or repetitive bursts of room air. On postnatal day 12, pups were sacrificed and brain dopamine levels characterized.

RESULTS

Baseline brain dopamine levels did not differ between rat pups born to dams who received ω-3 PUFA enriched versus standard rat chow diets. Rat pups born to dams maintained on normal diets, who were exposed to five days of repetitive hypoxic insults, experienced a 57% reduction in striatal dopamine levels accompanied by significant apoptosis. In contrast, ω-3 PUFA-enriched newborn pups experienced no loss in striatal dopamine levels, and only minimal apoptosis.

CONCLUSIONS

Our findings suggest that it may be feasible to confer neuroprotection against hypoxia-induced dopamine dysfunction to newborns likely to experience hypoxic insults. This could significantly improve the outcomes of those 8-11% of newborns who would otherwise experience hypoxia-induced behavioral, motor and cognitive dysfunction.

Development and Application of a Lifestyle Score for Prevention of Lethal Prostate Cancer

BACKGROUND

Several lifestyle factors have been associated with risk of lethal prostate cancer, but little is known about their combined effect. Our objective was to develop and apply a lifestyle score for prevention of lethal prostate cancer.

METHODS

We developed a lifestyle score among 42 701 men in the Health Professionals Follow-up Study (HPFS) followed from 1986 to 2010 and applied it among 20 324 men in the Physicians' Health Study (PHS) followed from 1982 to 2010. One point was given for each of: not currently smoking or quit 10 or more years ago, body mass index under 30 kg/m(2), high vigorous physical activity, high intake of tomatoes and fatty fish, and low intake of processed meat. Diet-only scores (range = 0-3) and total scores (range = 0-6) were calculated. We used multivariable Cox proportional hazards regression to estimate the risk of lethal prostate cancer, adjusting for potential risk factors of lethal prostate cancer. All statistical tests were two-sided.

RESULTS

We observed 576 lethal prostate cancer events in HPFS and 337 in PHS. Men with 5-6 vs 0-1 points had a 68% decreased risk of lethal prostate cancer (hazard ratio [HR] = 0.32, 95% confidence interval [CI] = 0.19 to 0.52) in HPFS and a non-statistically significant 38% decreased risk (HR = 0.62, 95% CI = 0.30 to 1.26) in PHS. For dietary factors only, men with 3 vs 0 points had a 46% decreased risk (HR = 0.54, 95% CI = 0.30 to 0.96) in the HPFS and a non-statistically significant 30% decreased risk (HR = 0.70, 95% CI = 0.40 to 1.23) in PHS.

CONCLUSIONS

Adhering to a healthy lifestyle, defined by not smoking, normal body weight, high physical activity, and a healthy diet, may lower risk of lethal prostate cancer.

The high prevalence of undiagnosed prostate cancer at autopsy: implications for epidemiology and treatment of prostate cancer in the Prostate-specific Antigen-era

Widespread prostate-specific antigen (PSA) screening detects many cancers that would have otherwise gone undiagnosed. To estimate the prevalence of unsuspected prostate cancer, we reviewed 19 studies of prostate cancer discovered at autopsy among 6,024 men. Among men aged 70-79, tumor was found in 36% of Caucasians and 51% of African-Americans. This enormous prevalence, coupled with the high sensitivity of PSA screening, has led to the marked increase in the apparent incidence of prostate cancer. The impact of PSA screening on clinical practice is well-recognized, but its effect on epidemiologic research is less appreciated. Before screening, a larger proportion of incident prostate cancers had lethal potential and were diagnosed at advanced stage. However, in the PSA era, overall incident prostate cancer mainly is indolent disease, and often reflects the propensity to be screened and biopsied. Studies must therefore focus on cancers with lethal potential, and include long follow-up to accommodate the lead time induced by screening. Moreover, risk factor patterns differ markedly for potentially lethal and indolent disease, suggesting separate etiologies and distinct disease entities. Studies of total incident or indolent prostate cancer are of limited clinical utility, and the main focus of research should be on prostate cancers of lethal potential.

Omega-3 Polyunsaturated Fatty Acids: The Way Forward in Times of Mixed Evidence

Almost forty years ago, it was first hypothesized that an increased dietary intake of omega-3 polyunsaturated fatty acids (PUFA) from fish fat could exert protective effects against several pathologies. Decades of intense preclinical investigation have supported this hypothesis in a variety of model systems. Several clinical cardiovascular studies demonstrated the beneficial health effects of omega-3 PUFA, leading medical institutions worldwide to publish recommendations for their increased intake. However, particularly in recent years, contradictory results have been obtained in human studies focusing on cardiovascular disease and the clinical evidence in other diseases, particularly chronic inflammatory and neoplastic diseases, was never established to a degree that led to clear approval of treatment with omega-3 PUFA. Recent data not in line with the previous findings have sparked a debate on the health efficacy of omega-3 PUFA and the usefulness of increasing their intake for the prevention of a number of pathologies. In this review, we aim to examine the controversies on the possible use of these fatty acids as preventive/curative tools against the development of cardiovascular, metabolic, and inflammatory diseases, as well as several kinds of cancer.

A Perspective on Prostate Carcinogenesis and Chemoprevention

In this perspective, modifiable carcinogenic factors for the prostate are summarized. This is followed by a discussion of how current knowledge about causation of prostate cancer and chemoprevention of prostate cancer can be used to develop preventive strategies. Prostate cancer is a slowly developing cancer which offers opportunities for preventive interventions. Only a few randomized clinical trials of prostate cancer prevention have been completed. The SELECT study with selenium and vitamin E did not find protective effects, but in two trials with 5α-reductase inhibitors risk was reduced about 25%, showing that chemoprevention is possible and indicating that the androgen receptor is a suitable target. Besides smoking cessation and reduction of obesity, there are no known dietary or life style interventions that will have a major impact on prostate cancer risk. Inflammation of the prostate is an attractive target and aspirin may be a promising candidate agent, but has not been addressed yet in preclinical and clinical studies. Antioxidants other than selenium and vitamin E are unlikely to be very effective and data on several dietary supplements are not encouraging. More candidate agents need to be identified and tested in relevant and adequate preclinical models and Phase II trials that have predictive value for outcome of Phase III randomized studies. Doing this will require a systematic approach comparing preclinical and clinical study outcomes to determine their predictive value of preventive efficacy.

Systematic review of prostate cancer risk and association with consumption of fish and fish-oils: analysis of 495,321 participants

INTRODUCTION

Fish-oils have a potential role in inflammation, carcinogenesis inhibition and favourable cancer outcomes. There has been increasing interest in the relationship of diet with cancer incidence and mortality, especially for eicosapantaenoic acid (EPA) and docosahexaenoic acid (DHA). This systematic-analysis of the literature aims to review evidence for the roles of dietary-fish and fish-oil intake in prostate-cancer (PC) risk, aggressiveness and mortality.

METHODS

A systematic-review, following PRISMA guidelines was conducted. PubMed, MEDLINE and Embase were searched to explore PC-risk, aggressiveness and mortality associated with dietary-fish and fish-oil intake. 37 studies were selected.

RESULTS

A total of 495,321 (37-studies) participants were investigated. These revealed various relationships regarding PC-risk (n = 31), aggressiveness (n = 8) and mortality (n = 3). Overall, 10 studies considering PC-risk found significant inverse trends with fish and fish-oil intake. One found a dose-response relationship whereas greater intake of long-chain-polyunsaturated fatty acids increased risk of PC when considering crude odds-ratios [OR: 1.36 (95% CI: 0.99-1.86); p = 0.014]. Three studies addressing aggressiveness identified significant positive relationships with reduced risk of aggressive cancer when considering the greatest intake of total fish [OR 0.56 (95% CI 0.37-0.86)], dark fish and shellfish-meat (p < 0.0001), EPA (p = 0.03) and DHA (p = 0.04). Three studies investigating fish consumption and PC-mortality identified a significantly reduced risk. Multivariate-OR (95% CI) were 0.9 (0.6-1.7), 0.12 (0.05-0.32) and 0.52 (0.30-0.91) at highest fish intakes.

CONCLUSIONS

Fish and fish-oil do not show consistent roles in reducing PC incidence, aggressiveness and mortality. Results suggest that the specific fish type and the fish-oil ratio must be considered. Findings suggest the need for large intervention randomised placebo-controlled trials.

A higher dietary ratio of long-chain omega-3 to total omega-6 fatty acids for prevention of COX-2-dependent adenocarcinomas

Compelling evidence that daily low-dose aspirin decreases risk for a number of adenocarcinomas likely reflects the fact that a modest but consistent inhibition of cyclooxygenase-2 (COX-2) activity can have a meaningful protective impact on risk for such cancers. The cancer-promoting effects of COX-2 are thought to be mediated primarily by prostaglandin E2 (PGE2), synthesized from arachidonic acid. The long-chain omega-3s eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), abundant in many fatty fish, can interfere with the availability of arachidonate to COX-2 by multiple complementary mechanisms; moreover, the PGE3 produced by COX-2 from EPA is a competitive inhibitor of the receptors activated by PGE2. These considerations have given rise to the hypothesis that a high dietary intake of EPA/DHA, relative to omega-6 (from which arachidonate is generated), should lessen risk for a number of adenocarcinomas by impeding PGE2 production and activity-while not posing the risk to vascular health associated with COX-2-specific nonsteroidal antiinflammatory agents. Analyses that focus on studies in which the upper category of fish consumption (not fried or salt-preserved) is 2 or more servings weekly, and on studies that evaluate the association of long-term fish oil supplementation with cancer risk yields a number of findings that are consistent with the hypothesis. Further studies of this nature may help to clarify the impact of adequate regular intakes of long-chain omega-3 on cancer risk, and perhaps provide insight into the dose-dependency of this effect.

The use of dietary supplements to alleviate androgen deprivation therapy side effects during prostate cancer treatment

Prostate cancer (PCa), the most commonly diagnosed cancer and second leading cause of male cancer death in Western societies, is typically androgen-dependent, a characteristic that underlies the rationale of androgen deprivation therapy (ADT). Approximately 90% of patients initially respond to ADT strategies, however many experience side effects including hot flashes, cardiotoxicity, metabolic and musculoskeletal alterations. This review summarizes pre-clinical and clinical studies investigating the ability of dietary supplements to alleviate adverse effects arising from ADT. In particular, we focus on herbal compounds, phytoestrogens, selenium (Se), fatty acids (FA), calcium, and Vitamins D and E. Indeed, there is some evidence that calcium and Vitamin D can prevent the development of osteoporosis during ADT. On the other hand, caution should be taken with the antioxidants Se and Vitamin E until the basis underlying their respective association with type 2 diabetes mellitus and PCa tumor development has been clarified. However, many other promising supplements have not yet been subjected large-scale clinical trials making it difficult to assess their efficacy. Given the demographic trend of increased PCa diagnoses and dependence on ADT as a major therapeutic strategy, further studies are required to objectively evaluate these supplements as adjuvant for PCa patients receiving ADT.

[Importance of long chain omega-3 fatty acids in prostate cancer]

The benefits of long chain polyunsaturated omega-3 fatty acids (n-3 PUFA) from fish or administered as supplements remain controversial regarding prostate cancer (PCa). Based on the currently available evidence no clear benefit of n-3 PUFA intake to generally reduce PCa incidence has been found. On the other hand n-3 PUFAs have a clear influence on the development of already existing PCa. The intake of n-3-PUFAs considerably reduces the risk of metastasis and PCa-related mortality.

Omega-3 polyunsaturated fatty acid intake through fish consumption and prostate specific antigen level: results from the 2003 to 2010 National Health and Examination Survey

The etiology of prostate cancer is uncertain, but intake of omega-3 polyunsaturated fatty acids (n-3 PUFAs) may play a role. We evaluated prostate specific antigen (PSA) levels with fish consumption (the primary source of n-3 PUFAs) and calculated PUFA intake. Serum PSA concentrations were available from 6018 men who participated in the 2003-2010 National Health and Nutrition Examination Survey (NHANES). Fish consumption was calculated via 30-day Food Frequency Questionnaire data, whereas n-3 PUFA intake was calculated from 24-h dietary recalls. We employed multivariable logistic and linear regression models to evaluate the association of these exposure variables with PSA levels while controlling for relevant covariates. PSA levels were lower in men who ate more breaded fish, but no other types of fish consumption or n-3 PUFA intake were associated with PSA levels. Our findings provide little evidence for a role of fish or n-3 PUFA consumption in influencing PSA levels.

Cancer incidence in a cohort with high fish consumption

PURPOSE

Evidence suggests that fish-derived omega-3 polyunsaturated fatty acids inhibit cancer promotion and progression. On the other hand, fish may contain endocrine-disrupting and potentially carcinogenic environmental contaminants. Our objective was to describe cancer incidence among the Finnish professional fishermen and their wives who are presumed to eat a lot of fish, partly from the contaminated Baltic Sea. Additionally, we wanted to see whether occupational characteristics are reflected in the fishermen's cancer pattern.

METHODS

All Finnish fishermen during 1980-2002 were identified from the Professional Fishermen Register (n = 6,410) and their wives from the National Population Information System (n = 4,260). The cohort was linked with the Finnish Cancer Registry data until 2011, and the standardized incidence ratios (SIR) were calculated based on national incidence rates.

RESULTS

The total cancer incidence among the fishermen and their wives was the same as in the Finnish general population. Among the fishermen, the incidence was increased for lip (SIR 2.17, 95 % confidence interval 1.26-3.47) and testis (2.51, 1.15-4.75) and decreased for colon (0.72, 0.52-0.98) cancers.

CONCLUSIONS

We cannot exclude the possibility that the observed excess in testis cancer among the fishermen could reflect life-long high exposure to environmental contaminants. An excess in lip cancer has been repeatedly observed among outdoor workers due to high exposure to ultraviolet radiation, whereas high physical activity during fishing is the most likely explanation for the deficit in colon cancer.

Effects of Marine Phospholipids Extract on the Lipid Levels of Metastatic and Nonmetastatic Prostate Cancer Patients

High intake of omega-3 fatty acids (n-3 FAs) from fish has shown to reduce metastatic progression of prostate cancer. This clinical trial investigated the influence of high n-3 FA intake (marine phospholipids, MPL) on the FA composition of blood lipids, lysophosphatidylcholine (LPC), and on lipoproteins in prostate cancer patients and elderly men without prostate cancer. MPL supplementation resulted in a significant increase of n-3 FAs (eicosapentaenoic and docosahexaenoic acid) in blood lipids, while arachidonic acid (n-6 FA) decreased significantly. Low density lipoprotein (LDL) and high density lipoprotein (HDL) increased significantly, but the LDL increase was observed only in subjects with an inactive tumour. Similarly, LPC plasma concentration increased significantly only in patients without tumour. The missing increase of LDL and LPC after MPL supplementation in patients with actively growing (metastasizing) prostate cancer suggests that tumour cells have an elevated demand for LDL and LPC. Due to the MPL-induced increase of n-3 FAs in these blood lipids, it can be assumed that especially actively growing and metastasizing prostate cancer cells are provided with elevated amounts of these antimetastatic n-3 FAs. A hypothetic model explaining the lower incidence of metastatic progression in prostate cancer patients with high fish consumption is presented.

Beyond androgen deprivation: ancillary integrative strategies for targeting the androgen receptor addiction of prostate cancer

The large majority of clinical prostate cancers remain dependent on androgen receptor (AR) activity for proliferation even as they lose their responsiveness to androgen deprivation or antagonism. AR activity can be maintained in these circumstances by increased AR synthesis--often reflecting increased NF-κB activation; upregulation of signaling pathways that promote AR activity in the absence of androgens; and by emergence of AR mutations or splice variants lacking the ligand-binding domain, which render the AR constitutively active. Drugs targeting the N-terminal transactivating domain of the AR, some of which are now in preclinical development, can be expected to inhibit the activity not only of unmutated ARs but also of the mutant forms and splice variants selected for by androgen deprivation. Concurrent measures that suppress AR synthesis or boost AR turnover could be expected to complement the efficacy of such drugs. A number of nutraceuticals that show efficacy in prostate cancer xenograft models--including polyphenols from pomegranate, grape seed, and green tea, the crucifera metabolite diindolylmethane, and the hormone melatonin--have the potential to suppress AR synthesis via downregulation of NF-κB activity; clinical doses of salicylate may have analogous efficacy. The proteasomal turnover of the AR is abetted by diets with a high ratio of long-chain omega-3 to omega-6 fatty acids, which are beneficial in prostate cancer xenograft models; berberine and sulforaphane, by inhibiting AR's interaction with its chaperone Hsp90, likewise promote AR proteasomal degradation and retard growth of human prostate cancer in nude mice. Hinge region acetylation of the AR is required for optimal transactivational activity, and low micromolar concentrations of the catechin epigallocatechin-3-gallate (EGCG) can inhibit such acetylation--possibly explaining the ability of EGCG administration to suppress androgenic activity and cell proliferation in prostate cancer xenografts. Hence, it is proposed that regimens featuring an N-terminal domain-targeting drug, various nutraceuticals/drugs that downregulate NF-κB activity, and/or supplemental intakes of fish oil, berberine, sulforaphane, and EGCG have potential for blocking proliferation of prostate cancer by targeting its characteristic addiction to androgen receptor activity.

Mediterranean diet and prostate cancer risk and mortality in the Health Professionals Follow-up Study

BACKGROUND

Prostate cancer (PCa) mortality rates are lower in the Mediterranean countries compared with northern Europe. Although specific components of the Mediterranean diet (Med-Diet) may influence PCa risk, few studies have assessed the traditional Med-Diet pattern with the risk of incident advanced or lethal PCa or with disease progression among men diagnosed with nonmetastatic PCa.

OBJECTIVE

To determine whether the traditional Med-Diet pattern is associated with risk of incident advanced or lethal PCa and with PCa-specific and overall mortality among men with PCa.

DESIGN, SETTING, AND PARTICIPANTS

We prospectively followed 47 867 men in the Health Professionals Follow-up Study followed from 1986 to 2010. The case-only analysis included 4538 men diagnosed with nonmetastatic PCa, followed from diagnosis to lethal outcome or to January 2010.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

We used Cox proportional hazards models to examine traditional and alternative Med-Diet scores in relation to PCa incidence outcomes (advanced and lethal disease). In a case-only survival analysis, we examined postdiagnostic Med-Diet and risk of lethal (metastases or PCa death) and fatal PCa as well as overall mortality among men diagnosed with nonmetastatic disease.

RESULTS AND LIMITATIONS

Between 1986 and 2010, 6220 PCa cases were confirmed. The Med-Diet was not associated with risk of advanced or lethal PCa. In the case-only analysis, there was no association between the Med-Diet after diagnosis and risk of lethal or fatal PCa. However, there was a 22% lower risk of overall mortality (hazard ratio: 0.78; 95% confidence interval, 0.67-0.90; p(trend)=0.0007) among men with greater adherence to the Med-Diet after PCa diagnosis. We found similar associations for the alternative score.

CONCLUSIONS

A higher Med-Diet score was not associated with risk of advanced PCa or disease progression. Greater adherence to the Med-Diet after diagnosis of nonmetastatic PCa was associated with lower overall mortality.

Fish intake and ovarian cancer risk: a meta-analysis of 15 case-control and cohort studies

Background

Previous epidemiological studies have shown that fish consumption may modify the risk of ovarian cancer. However, these studies yielded controversial results. The present meta-analysis was undertaken to evaluate the relationship between fish intake and ovarian cancer risk.

Methods

A literature search was carried out using Pubmed, Embase, and Cochrane Library Central database for all relevant studies up to August 2013. We pooled the relative risks (RR) from individual studies using fixed-effect or random-effect model, and carried out heterogeneity and publication bias analyses.

Results

A total of 15 (ten case–control, and five cohort) studies were included in the present meta-analysis, representing data for 889,033 female subjects and 6,087 ovarian cancer cases. We found that total fish intake was not significantly associated with the risk of ovarian cancer among cohort studies (RR = 1.04 95% CI [0.89, 1.22]) as well as case–control studies (RR = 0.90, 95% CI [0.73,1.12]). There was no evidence of publication bias as suggested by Begg's test (P = 0.55) and Egger's test(P = 0.29).

Conclusions

The present meta-analysis showed that total fish consumption was not significantly associated with the risk of ovarian cancer. Further analysis on different fish species and food preparation methods should be conducted in future studies.

Arachidonic acid induction of Rho-mediated transendothelial migration in prostate cancer

BACKGROUND

Bone metastases in prostate cancer (CaP) result in CaP-related morbidity/mortality. The omega-6 polyunsaturated fatty acid (PUFA) arachidonic acid (AA) and lipophilic statins affect metastasis-like behaviour in CaP cells, regulating the critical metastatic step of CaP migration to the bone marrow stroma.

METHODS

Microscopic analysis and measurement of adhesion and invasion of CaP cells through bone marrow endothelial cells (BMEC) was undertaken with AA stimulation and/or simvastatin (SIM) treatment. Amoeboid characteristics of PC-3, PC3-GFP and DU-145 were analysed by western blotting and Rho assays.

RESULTS

The CaP cell lines PC-3, PC3-GFP and DU-145 share the ability to migrate across a BMEC layer. Specific amoeboid inhibition decreased transendothelial migration (TEM). AA stimulates amoeboid characteristics, driven by Rho signalling. Selective knock-down of components of the Rho pathway (RhoA, RhoC, Rho-associated protein kinase 1 (ROCK1) and ROCK2) showed that Rho signalling is crucial to TEM. Functions of these components were analysed, regarding adhesion to BMEC, migration in 2D and the induction of the amoeboid phenotype by AA. TEM was reduced by SIM treatment of PC3-GFP and DU-145, which inhibited Rho pathway signalling.

CONCLUSIONS

AA-induced TEM is mediated by the induction of a Rho-driven amoeboid phenotype. Inhibition of this cell migratory process may be an important therapeutic target in high-risk CaP.

Targeting survival pathways in chronic myeloid leukaemia stem cells

Chronic myeloid leukaemia (CML) is a clonal myeloproliferative disorder characterized by the presence of a fusion oncogene BCR-ABL, which encodes a protein with constitutive TK activity. The implementation of tyrosine kinase inhibitors (TKIs) marked a major advance in CML therapy; however, there are problems with current treatment. For example, relapse occurs when these drugs are discontinued in the majority of patients who have achieved a complete molecular response on TKI and these agents are less effective in patients with mutations in the BCR-ABL kinase domain. Importantly, TKI can effectively target proliferating mature cells, but do not eradicate quiescent leukaemic stem cells (LSCs), therefore allowing disease persistence despite treatment. It is essential that alternative strategies are used to target the LSC population. BCR-ABL activation is responsible for the modulation of different signalling pathways, which allows the LSC fraction to evade cell death. Several pathways have been shown to be modulated by BCR-ABL, including PI3K/AKT/mTOR, JAK-STAT and autophagy signalling pathways. Targeting components of these survival pathways, alone or in combination with TKI, therefore represents an attractive potential therapeutic approach for targeting the LSC. However, many pathways are also active in normal stem cells. Therefore, potential targets must be validated to effectively eradicate CML stem cells while sparing normal counterparts. This review summarizes the main pathways modulated in CML stem cells, the recent developments and the use of novel drugs to target components in these pathways which may be used to target the LSC population.

LINKED ARTICLES

This article is part of a themed section on Emerging Therapeutic Aspects in Oncology. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.169.issue-8.

Omega-3 fatty acids and cardiovascular disease: new developments and applications

The omega-3 fatty acids (FA) found in fish oils, eicosapentaenoic and docosahexaenoic acids (EPA and DHA, respectively), have been extensively studied therapeutically in a wide variety of disease conditions, but in none more than cardiovascular disease (CVD). Our review summarizes mechanisms of action, recent meta-analyses of CVD outcome trials, sources (fish and supplements), and recommendations for use of omega-3 FA in clinical practice. With the ability to now measure the omega-3 FA biostatus through blood tests, patients can achieve cardioprotective levels by either taking fish oil supplements or simply eating more oily fish. Two omega-3 FA formulations (both in the ethyl ester form) have been approved by the US Food and Drug Administration (FDA) for the treatment of patients with very high triglyceride levels (> 500 mg/dL); one contains both EPA and DHA, whereas the other contains only EPA. The agents have been extensively tested in 2 patient populations, those with very high triglycerides and those with triglycerides between 200 and 500 mg/dL while on background statin therapy. In general, treatment with EPA+DHA appears to lower patient triglycerides more effectively, but in those patients with very high triglyceride levels, use of EPA+DHA also raised low-density lipoprotein cholesterol levels, whereas EPA alone did not. Both formulations, at doses that do not lower triglycerides, have been shown to reduce CVD events in some, but not all, studies. Given the favorable risk-to-benefit ratio for these essentially nutritional agents, use is expected to continue to expand.

The strategies to control prostate cancer by chemoprevention approaches

Prostate cancer (PCA) is the most commonly diagnosed cancer in men in the United States with growing worldwide incidence. Despite intensive investment in improving early detection, PCA often escapes timely detection and mortality remains high; this malignancy being the second highest cancer-associated mortality in American men. Collectively, health care costs of PCA results in an immense financial burden that is only expected to grow. Additionally, even in cases of successful treatment, PCA is associated with long-term and pervasive effects on patients. A proactive alternative to treat PCA is to prevent its occurrence and progression prior to symptomatic malignancy. This may serve to address the issue of burgeoning healthcare costs and increasing number of sufferers. One potential regimen in service of this alternative is PCA chemoprevention. Here, chemical compounds with cancer preventive efficacy are identified on the basis of their potential in a host of categories: their historical medicinal use, correlation with reduced risk in population studies, non-toxicity, their unique chemical properties, or their role in biological systems. PCA chemopreventive agents are drawn from multiple broad classes of chemicals, themselves further subdivided based on source or potential effect, with most derived from natural products. Many such compounds have shown efficacy, varying from inhibiting deregulated PCA cell signaling, proliferation, epithelial to mesenchymal transition (EMT), invasion, metastasis, tumor growth and angiogenesis and inducing apoptosis. Overall, these chemopreventive agents show great promise in PCA pre-clinical models, though additional work remains to be done in effectively translating these findings into clinical use.

The biology and natural history of prostate cancer: a short introduction

This chapter aims to serve as a quick glance outlining an overall picture of mainstream thoughts, and to serve as a point of departure for more thorough discussions. The introduction of PSA testing has immensely complicated research in prostate cancer epidemiology and biology and added new clinical and biological domains. As for many cancers, age and ethnic origin are the strongest known risk factors. While migrant studies imply that environment and/or personal life style is important, epidemiological studies have failed to establish any strong leads. Despite the known androgen dependence of prostate cancer, there is little to support that circulating levels of androgens, estrogens or 5-alpha-reductase are associated with risk of developing the disease. However, a consistent finding is a positive association with levels of Insulin-like Growth Factor-1 (IGF-1). Prostate cancer is one of the cancers most strongly related to inherited susceptibility, even when taking into account that family history of prostate cancer triggers PSA testing among relatives. A number of somatic genetic alterations (amplifications, deletions, point mutations, translocations) are associated with prostate cancer risk. Findings for alterations in FASN, HPN, AMACR and MYC have been fairly consistent. Recent research shows that the notion of "hormone-independent prostate cancer" has to be revised: most prostate cancers remain dependent on androgen receptor signalling also after progression despite traditional androgen deprivation therapy. Traditional markers of stage and type of disease still play a major role for prognostication and treatment decisions. Prostate cancer is one of the few cancers where patients have been recommended watchful waiting or active surveillance. This provides opportunities for studies of natural history of the disease. The understanding of prostate cancer aetiology and natural history has progressed slowly. However, the current situation is positively challenging and opens up possibilities for fruitful research.

A low dietary ratio of omega-6 to omega-3 Fatty acids may delay progression of prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer-related deaths in men. Studies show that consumption of polyunsaturated fatty acids (PUFA) modulates the development and progression of prostate cancer. High amounts of omega-6 fatty acids have been linked with increased prostate cancer risk, whereas omega-3 fatty acids have been shown to inhibit PCa growth. However, because omega-3 and omega-6 are both essential fatty acids and part of a complete diet, it is more relevant to determine the ideal ratio of the two that would allow patients to benefit from the therapeutic properties of omega-3 fatty acids. LNCaP prostate cancer cells were treated with dietary-based ratios of omega-6 to omega-3 fatty acids under hormone-deprivation conditions, and effects on various cellular processes were determined. A low omega-6 to omega-3 PUFA ratio can delay the progression of cells toward castration-resistance by suppressing pathways involved in prostate cancer progression, such as the Akt/mTOR/NFκB axis. It also suppresses the expression of cyclin D1, and activation of caspase-3 and annexin V staining shows induction of proapoptotic events. Taken together, our data demonstrates that maintaining a low omega-6 to omega-3 fatty acids ratio can enhance efficacy of hormone ablation therapy.

Diet and cancer: risk factors and epidemiological evidence

BACKGROUND

Diet represents 30-35% of risk factors that contribute to the onset of cancer. Some foods and dietary patterns have been linked to the risk of various cancers. However epidemiological available data are not consistent for many foods and the associations with cancer risk remain unclear. The concerns about this issue are considered like a "Hot topic" for oncologists and general population.

OBJECTIVE

The aim of this report is to present a review of the published epidemiologic research to date reflecting the most current scientific evidence related to diet and cancer risk.

DESIGN

EMBASE and PubMed-NCBI were searched for relevant articles up to October 2013 that identified potentials interactions between foods or dietary patterns with cancer risk.

RESULTS

There is no conclusive evidence as an independent risk factor for isolated nutrients versus adoption of dietary patterns for cancer risk. Moderate physical activity after breast cancer diagnosis contributes to 40% reduction of recurrence/disease-specific mortality. Cancer colon risk derived from meat intake is influenced by both total intake and its frequency. The interaction of phenolic compounds on metabolic and signaling pathways like P450, MAP kinase, PI3 kinase, IGF-1, NF-kB and ROS seems to exert an inhibitory effect on cell proliferation and tumor metastasis and induces apoptosis in various types of cancer cells, including colon, lung, prostate, hepatocellular or breast cancer.

CONCLUSIONS

There is a direct relationship between unhealthy diet and lifestyle with the increase of tumor development and cancer risk. For this reason, a good nutritional status based on a balanced diet constitutes one of the main preventive factors from tumors. However the mixed results from epidemiologic studies hinder to get unequivocal and consistent evidence about the interaction between diet and cancer risk. More epidemiological studies will be needed in the future to clarify this issue.

The association between fish consumption and risk of renal cancer: a meta-analysis of observational studies

Background

Several case-control studies and cohort studies have investigated the association between fish intake and renal cancer risk, however, they yielded conflicting results. To our knowledge, a comprehensive assessment of the association between fish consumption and risk of renal cancer has not been reported. Hence, we conducted a systematic literature search and meta-analysis to quantify the association between fish consumption and renal cancer.

Methods

A systematic search was performed using the PubMed, Embase, and Cochrane Library Central database for case-control and cohort studies that assessed fish intake and risk of renal cancer. Two authors independently assessed eligibility and extracted data. Fixed-effect and random-effect models were used to estimate summary relative risks (RR) and the corresponding 95% confidence intervals (CIs). Subgroup analyses, sensitivity analysis and cumulative meta-analysis were also performed.

Results

A total of 12 case-control studies and three cohort studies published between 1990 and 2011 were included in the meta-analysis, involving 9,324 renal cancer cases and 608,753 participants. Meta-analysis showed that fish consumption did not significantly affect the risk of renal cancer (RR=0.99, 95% CI [0.92,1.07]). In our subgroup analyses, the results were not substantially affected by study design, region, gender, and confounder adjustments. Furthermore, sensitivity analysis confirmed the stability of results.

Conclusions

The present meta-analysis suggested that there was no significant association between fish consumption and risk of renal cancer. More in-depth studies are warranted to report more detailed results, including stratified results by fish type, preparation method, and gender.

Effect of a low-fat fish oil diet on proinflammatory eicosanoids and cell-cycle progression score in men undergoing radical prostatectomy

We previously reported that a 4- to 6-week low-fat fish oil (LFFO) diet did not affect serum insulin-like growth factor (IGF)-1 levels (primary outcome) but resulted in lower omega-6 to omega-3 fatty acid ratios in prostate tissue and lower prostate cancer proliferation (Ki67) as compared with a Western diet. In this post hoc analysis, the effect of the LFFO intervention on serum pro-inflammatory eicosanoids, leukotriene B4 (LTB4) and 15-S-hydroxyeicosatetraenoic acid [15(S)-HETE], and the cell-cycle progression (CCP) score were investigated. Serum fatty acids and eicosanoids were measured by gas chromatography and ELISA. CCP score was determined by quantitative real-time reverse transcriptase PCR (RT-PCR). Associations between serum eicosanoids, Ki67, and CCP score were evaluated using partial correlation analyses. BLT1 (LTB4 receptor) expression was determined in prostate cancer cell lines and prostatectomy specimens. Serum omega-6 fatty acids and 15(S)-HETE levels were significantly reduced, and serum omega-3 levels were increased in the LFFO group relative to the Western diet group, whereas there was no change in LTB4 levels. The CCP score was significantly lower in the LFFO compared with the Western diet group. The 15(S)-HETE change correlated with tissue Ki67 (R = 0.48; P < 0.01) but not with CCP score. The LTB4 change correlated with the CCP score (r = 0.4; P = 0.02) but not with Ki67. The LTB4 receptor BLT1 was detected in prostate cancer cell lines and human prostate cancer specimens. In conclusion, an LFFO diet resulted in decreased 15(S)-HETE levels and lower CCP score relative to a Western diet. Further studies are warranted to determine whether the LFFO diet antiproliferative effects are mediated through the LTB4/BLT1 and 15(S)-HETE pathways.

Mechanisms of omega-3 polyunsaturated fatty acids in prostate cancer prevention

This review focuses on several key areas where progress has been made recently to highlight the role of omega-3 polyunsaturated fatty acid in prostate cancer prevention.

Plasma phospholipid fatty acids, dietary fatty acids and prostate cancer risk

Animal and experimental studies have demonstrated that long-chain n-3 fatty acids inhibit the development of prostate cancer, whereas n-6 fatty acids might promote it. We performed a case-cohort analysis within the Melbourne Collaborative Cohort Study using a random sample of 1,717 men and 464 prostate cancer cases to investigate associations between fatty acids assessed in plasma phospholipids (PPLs) or diet (estimated using a 121-item food frequency questionnaire) and prostate cancer risk. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox regression. Prostate cancer risk was positively associated with %PPL saturated fatty acids (SFAs); HR [95% CI] = 1.51 [1.06, 2.16] (Q5 vs. Q1, fifth vs. first quintile); p-trend = 0.003. HRs (Q5 to Q2 vs. Q1) were significantly elevated for %PPL palmitic acid. %PPL oleic acid was inversely associated with risk, HR = 0.62 [0.43, 0.91] (Q5 vs. Q1); p-trend = 0.04. No statistically significant linear trends were observed for dietary intakes. The HRs were elevated for moderate intakes of linoleic acid (Q2 and Q3 vs. Q1, 1.58 [1.10, 2.28] and 1.70 [1.18, 2.46], respectively), but the increase was not significant for higher intakes (Q4 and Q5). No association varied significantly by tumour aggressiveness (all p-homogeneity > 0.1). Prostate cancer risk was positively associated with %PPL SFA, largely attributable to palmitic acid and inversely associated with %PPL monounsaturated fatty acids, largely attributable to oleic acid. Higher risks were also observed for dietary n-6 polyunsaturated fats, primarily linoleic acid.

Evidence of health benefits of canola oil

Canola oil-based diets have been shown to reduce plasma cholesterol levels in comparison with diets containing higher levels of saturated fatty acids. Consumption of canola oil also influences biological functions that affect various other biomarkers of disease risk. Previous reviews have focused on the health effects of individual components of canola oil. Here, the objective is to address the health effects of intact canola oil, as this has immediate practical implications for consumers, nutritionists, and others deciding which oil to consume or recommend. A literature search was conducted to examine the effects of canola oil consumption on coronary heart disease, insulin sensitivity, lipid peroxidation, inflammation, energy metabolism, and cancer cell growth. Data reveal substantial reductions in total cholesterol and low-density lipoprotein cholesterol, as well as other positive actions, including increased tocopherol levels and improved insulin sensitivity, compared with consumption of other dietary fat sources. In summary, growing scientific evidence supports the use of canola oil, beyond its beneficial actions on circulating lipid levels, as a health-promoting component of the diet.

Mediterranean Diet Score and prostate cancer risk in a Swedish population-based case-control study

Several individual components of the Mediterranean diet have been shown to offer protection against prostate cancer. The present study is the first to investigate the association between adherence to the Mediterranean diet and the relative risk of prostate cancer. We also explored the usefulness of the Mediterranean Diet Score (MDS) in a non-Mediterranean population. FFQ data were obtained from 1482 incident prostate cancer patients and 1108 population-based controls in the Cancer of the Prostate in Sweden (CAPS) study. We defined five MDS variants with different components or using either study-specific intakes or intakes in a Greek reference population as cut-off values between low and high intake of each component. Unconditional logistic regression was used to estimate the relative risk of prostate cancer for high and medium v. low MDS, as well as potential associations with the individual score components. No statistically significant association was found between adherence to the Mediterranean diet based on any of the MDS variants and prostate cancer risk (OR range: 0·96-1·19 for total prostate cancer, comparing high with low adherence). Overall, we found little support for an association between the Mediterranean diet and prostate cancer in this Northern European study population. Despite potential limitations inherent in the study or in the build-up of a dietary score, we suggest that the original MDS with study-specific median intakes as cut-off values between low and high intake is useful in assessing the adherence to the Mediterranean diet in non-Mediterranean populations.

Consumption of fish products across the lifespan and prostate cancer risk

Objective

To examine whether fish and fish oil consumption across the lifespan is associated with a lower risk of prostate cancer.

Design

The study was nested among 2268 men aged 67–96 years in the AGES-Reykjavik cohort study. In 2002 to 2006, dietary habits were assessed, for early life, midlife and later life using a validated food frequency questionnaire. Participants were followed for prostate cancer diagnosis and mortality through 2009 via linkage to nationwide cancer- and mortality registers. Adjusting for potential confounders, we used regression models to estimate odds ratios (ORs) and hazard ratios (HRs) for prostate cancer according to fish and fish oil consumption.

Results

Among the 2268 men, we ascertained 214 prevalent and 133 incident prostate cancer cases, of which 63 had advanced disease. High fish consumption in early- and midlife was not associated with overall or advanced prostate cancer. High intake of salted or smoked fish was associated with a 2-fold increased risk of advanced prostate cancer both in early life (95% CI: 1.08, 3.62) and in later life (95% CI: 1.04, 5.00). Men consuming fish oil in later life had a lower risk of advanced prostate cancer [HR (95%CI): 0.43 (0.19, 0.95)], no association was found for early life or midlife consumption.

Conclusions

Salted or smoked fish may increase risk of advanced prostate cancer, whereas fish oil consumption may be protective against progression of prostate cancer in elderly men. In a setting with very high fish consumption, no association was found between overall fish consumption in early or midlife and prostate cancer risk.