Diet and Cancer

Series EditorAdriana Albini

For further volumes:http://www.springer.com/series/8049

Gabriella Calviello · Simona SeriniEditors

Dietary Omega-3Polyunsaturated Fatty Acidsand Cancer

123

EditorsProf. Gabriella CalvielloUniversita Cattolica SacroCuore - RomaIstituto di Patologia GeneraleLargo F. Vito, 100168 RomaItalyg.calviello@rm.unicatt.it

Dr. Simona SeriniUniversita Cattolica SacroCuore - RomaIstituto di Patologia GeneraleLargo F. Vito, 100168 RomaItalyserini_s@yahoo.it

ISBN 978-90-481-3578-3 e-ISBN 978-90-481-3579-0DOI 10.1007/978-90-481-3579-0Springer Dordrecht Heidelberg London New York

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Contents

Part I Possible Mechanisms

1 Possible Mechanisms of ω-3 PUFA Anti-tumour Action . . . . . . . 3Michael B. Sawyer and Catherine J. Field

Part II ω-3 PUFAs and Colon Cancer

2 ω-3 PUFAs and Colon Cancer: Epidemiological Studies . . . . . . 41Yasumi Kimura

3 ω-3 PUFAs and Colon Cancer: Experimental Studies andHuman Interventional Trials . . . . . . . . . . . . . . . . . . . . . 67Simona Serini, Elisabetta Piccioni, and Gabriella Calviello

Part III ω-3 PUFAs and Hormone-Related Cancers (Breast and Prostate)

4 ω-3 PUFAs and Breast Cancer: Epidemiological Studies . . . . . . 93Paul D. Terry and Pamela J. Mink

5 ω-3 PUFAs and Prostate Cancer: Epidemiological Studies . . . . . 109Pierre Astorg

6 ω-3 PUFAs: Interventional Trials for the Prevention andTreatment of Breast and Prostate Cancer . . . . . . . . . . . . . . 149Isabelle M. Berquin, Iris J. Edwards, Joseph T. O’Flaherty, andYong Q. Chen

7 ω-3 PUFAs, Breast and Prostate Cancer: Experimental Studies . . 167Iris J. Edwards, Isabelle M. Berquin, Yong Q. Chen, andJoseph T. O’Flaherty

Part IV ω-3 PUFAs and Other Cancers

8 ω-3 PUFAs and Other Cancers . . . . . . . . . . . . . . . . . . . . 191Kyu Lim and Tong Wu

v

vi Contents

9 The Influence of ω-3 PUFAs on Chemo- or RadiationTherapy for Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . 219W. Elaine Hardman

10 ω-3 PUFAs and Cachexia . . . . . . . . . . . . . . . . . . . . . . . 231Michael J. Tisdale

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

Contributors

Pierre Astorg Unité Nutrition et Régulation Lipidique des Fonctions Cérébrales(NuReLiCe), INRA, 78352 Jouy-en-Josas, France, pierre.astorg@jouy.inra.fr

Isabelle M. Berquin Departments of Cancer Biology and Comprehensive CancerCenter, Wake Forest University School of Medicine, Winston-Salem, NC27157, USA, iberquin@wfubmc.edu

Gabriella Calviello Institute of General Pathology, Catholic University, L.go F.Vito 1, 00168 Rome, Italy, g.calviello@rm.unicatt.it

Yong Q. Chen Departments of Cancer Biology and Comprehensive CancerCenter, Wake Forest University School of Medicine, Winston-Salem, NC 27157,USA, yqchen@wfubmc.edu

Iris J. Edwards Department of Pathology and Comprehensive Cancer Center,Wake Forest University School of Medicine, Medical Center Boulevard,Winston-Salem, NC 27157, USA, iedwards@wfubmc.edu

Catherine J. Field Alberta Institute for Human Nutrition, 4-126A HRIF East,University of Alberta, Edmonton, AB, Canada, catherine.field@ualberta.ca

W. Elaine Hardman Department of Biochemistry and Microbiology, ByrdBiotechnology Science Center, Marshall University School of Medicine,Huntington, WV 25755, USA, hardmanw@marshall.edu

Yasumi Kimura Department of Nutrition and Life Science, Fukuyama University,Fukuyama, Hiroshima, 729-0292, Japan, kimura@fubac.fukuyama-u.ac.jp

Kyu Lim Department of Biochemisty, Cancer Research Institute and InfectionSignaling Network Research Center, College of Medicine, Chungnam NationalUniversity, Daejeon, Korea, kyulim@cnu.ac.kr

Pamela J. Mink Department of Epidemiology, Rollins School of Public Health,Emory University, Atlanta, GA, USA, pmink@sph.emory.edu

Joseph T. O’Flaherty Departments of Internal Medicine and ComprehensiveCancer Center, Wake Forest University School of Medicine, Winston-Salem, NC27157, USA, joflaher@wfubmc.edu

vii

viii Contributors

Elisabetta Piccioni Institute of General Pathology, Catholic University, L.go F.Vito 1, 00168 Rome, Italy, epiccioni@rm.unicatt.it

Michael B. Sawyer Departments of Oncology, University of Alberta, Edmonton,AB, Canada, michsawy@cancerboard.ab.ca

Simona Serini Institute of General Pathology, Catholic University, L.go F. Vito 1,00168 Rome, Italy, serini_s@yahoo.it

Paul D. Terry Department of Epidemiology, Rollins School of Public Health,Emory University, Atlanta, GA, USA, pdterry@sph.emory.edu

Michael J. Tisdale Nutritional Biomedicine, School of Life and Health Sciences,Aston University, Birmingham, B4 7ET, UK, m.j.tisdale@aston.ac.uk

Tong Wu Department of Pathology, University of Pittsburgh School of Medicine,Pittsburgh, PA, USA, wut@upmc.edu

Introduction: Omega-3 PUFAs,Why Do We Speak About Them?

Gabriella Calviello and Simona Serini

Abstract In spite of the fact that few dietary components are so widely recog-nized as able to improve human health such as ω-3 polyunsaturated fatty acids(PUFAs), so that their sector in the nutritional market has been increasingly grow-ing worldwide, many unresolved questions still remain about them. In particular,there is urgent need for better understanding their possible role as anti-neoplasticagents. First of all, the chemical structure, the intracellular metabolism, and thedietary sources and bioavailability of these dietary fatty acids will be described inthis introductive chapter to make easier the comprehension of the remaining partsof the book. Afterward, a brief outline of ω-3 PUFA reported benefits in differ-ent fields of human health will be provided. In this introductive part we will tacklealso the problem of the discrepancies occurring between the results of most experi-mental studies on animals and cultured cells, which, almost univocally, suggest thebeneficial anti-neoplastic effects of these fatty acids, and the outcome of several ofthe epidemiological observational studies, which, conversely, shows a scarce or nullpositive association between high intake of fish or fish oil at high content in ω-3PUFAs and prevention of different kinds of cancer. Finally, a brief outline of theorganization of the present book will be provided.

Keywords ω-3 PUFA · Metabolism · Dietary sources · Bioavailability ·Anti-neoplastic effects

Introduction

There are few dietary components that are so widely recognized as able to improvehuman health like ω-3 polyunsaturated fatty acids (PUFAs), and whose sector inthe nutritional market has been increasingly growing worldwide. However, despite

G. Calviello (B)Institute of General Pathology, School of Medicine, Catholic University, L.go F. Vito 1 00168Rome, Italye-mail: g.calviello@rm.unicatt.it

ix

x Introduction: Omega-3 PUFAs, Why Do We Speak About Them?

their large fame and easy commercial availability, many unresolved questions stillremain about them. For instance, may their intake represent an actual preventivestrategy against cancer? Is their ingestion safe for healthy people? Do they have thepotential to act as chemotherapic agents in combination or not with other conven-tional anti-cancer therapies? Which kind of cancer patients could actually benefitfrom treatments with ω-3 PUFAs? At what stages of cancer growth and progressiontheir intake could be considered really fruitful? The present book has been thoughtin order to collect the findings and opinions of several influential scientists in thefields and thus to help answering these and other questions. The beneficial effectof ω-3 PUFAs on hormone-related cancers (breast and prostate cancer) and coloncancer has received most of the attention, and for this reason they will be treatedin separate chapters. ω-3 PUFAs, however, appear to exert their positive influencealso toward a number of other kinds of cancers, including leukemias/lymphomas,melanoma, neuroblastoma, liver, and lung cancer. However, before treating thesespecific topics, a general introduction will be furnished in this chapter with the aimto clarify some basic aspects regarding ω-3 PUFAs, such as their chemical struc-ture and metabolism, their sources and bioavailability, and the other diseases whoseincidence or progression can be favorably affected by these fatty acids.

Chemistry and Metabolism of ω-3 PUFAs

Fatty acids (FA) are constituted by carbon chains of various lengths in which car-bons are bound by single or double bonds. A methyl group is present at one end(the “n” or “ω” end) and a carboxyl group at the other end. The lack or pres-ence of double bonds between the carbons defines the two classes of saturatedand unsaturated fatty acids (UFA). Depending on the presence of one or more dou-ble bonds in the carbon chain, UFAs are divided into monounsaturated fatty acids(MUFAs) and PUFAs. The prevalent PUFAs found in nature belong to the ω-3and ω-6 classes of PUFAs, whose first double bond is, respectively, placed eitherthree carbons (in the ω-3 or n–3 position) or six carbons (in the ω-6 or n–6 posi-tion) from the methyl end of the carbon chain. The three main dietary ω-3 PUFAsare α-linolenic acid (C18:3 n–3, all-cis-9,12,15-octadecatrienoic acid, ALA), eicos-apentaenoic acid (C20:5 n–3, all-cis-eicosa-5,8,11,14,17-pentaenoic acid, EPA),and docosahexaenoic acid (C22:6 n–3, all-cis-docosa-4,7,10,13,16,19-hexaenoicacid, DHA) (Fig. 1). ALA, together with linoleic acid (LA, 18:2 n:6), is consideredthe “essential fatty acid” (EFA), namely the diet must necessarily provide them,since the desaturase needed to place the double bond in position ω-3 or ω-6 inthe PUFAs is lacking in mammals. On the other hand, this desaturase is presentin vegetables, which, therefore, represent the main dietary source of ALA and LAfor mammals. Many commonly used vegetables oils are enriched in LA (corn, saf-flower, and soybean oils), whereas canola oil, ground flaxseed, and walnuts containhigh levels of ALA. PUFAs belonging to one of the two different classes (ω-3 orω-6) are not interconvertible into PUFAs of the other class. In our tissues, ALA andLA can be metabolized by the sequential action of several desaturases and elon-gases to produce EPA and arachidonic acid (AA, 20:4 n–6), respectively. Further

G. Calviello and S. Serini xi

COOHEPA

1

2

3

ω

ω

ω

COOH

1

2

3

DHA

COOHALA

1

2

3

Fig. 1 Chemical structuresof the major dietary ω-3PUFAs. ALA: α-linolenicacid; EPA: eicosapentaenoicacid; DHA: docosahexaenoicacid

desaturase, elongase, and partial peroxisomal beta-oxidation steps are needed [1, 2]to generate ω-3 PUFAs longer than EPA, such as DHA (for a detailed descriptionof all the reactions, see Fig. 7.1). It has been shown that the ALA affinity for �6-desaturase is higher than that of LA. However, if the Western diet is adopted, inwhich LA is present in higher amounts than ALA, LA becomes the EFA preferen-tially desaturated [3]. As a result, the endogenous production of EPA and DHA bythe precursor ALA is not very efficient in humans, and the efficiency of the conver-sion of ALA to EPA or DHA becomes particularly low in preterm infants and mayalso decline with old age [4]. Consequently, the main sources of EPA and DHA areanimal tissues deriving from poultry, fat fish, and seafood, which contain high levelsof these fatty acids. However, the current dietary supplies of the majority of Westerncountries are able to furnish very low amounts of ω-3 PUFAs. It has been calculatedthat the dietary ratio of ω-6 to ω-3 PUFAs ranges from 15/1 to 16.7/1 in Westerndiets and, therefore, is much lower than the ratio of 1/1 present in wild animal’s andprobably also in our ancestor’s diets [5]. In the short periods of time over the past100–150 years an absolute and relative change of ω-3/ω-6 PUFA ratio in Westerndiets has occurred which could help to explain the increasing incidence of somekinds of human diseases [5]. Both ω-3 PUFAs and ω-6 PUFAs have the potential toinfluence gene expression and the unchanged dietary ratio between ω-6 PUFAs andω-3 PUFAs of 1/1 over millions of years could have substantially influenced geneticmodifications and human evolution. Now, a substantial decrease in EPA and DHAincorporated in cellular membranes and the concomitant increase in AA may haveproduced dangerous consequences for human health.

Intracellular Metabolism of ω-3 PUFAs and Competitionwith Arachidonic Acid

At this point, the description of the oxidative metabolism of AA and EPA, and, inparticular, of the influence of ω-3 PUFAs on the oxidative metabolism of AA, seemsparticularly useful to understand the possible benefits deriving from the substitution

xii Introduction: Omega-3 PUFAs, Why Do We Speak About Them?

of AA for these fatty acids in membranes. Following a series of cellular stimula-tions, AA is released from membranes by the action of phospholipase A2 (PLA2)and metabolized by cyclooxygenase (COX) and lipoxygenase (LOX) enzymes intothe oxygenated metabolites prostaglandins (PG), thromboxanes (TX), leukotrienes(LT), and hydro fatty acids, collectively known as eicosanoids [6] (Fig. 2). TheAA-derived eicosanoids are biologically highly efficient, acting at very small con-centrations. They have the potential to influence key events of physiological andpathological processes, including proliferation, survival, and inflammation [7]. Theformation of the AA products is normally controlled, but in some pathologicalconditions such as cancer excessive amounts are produced [8]. After ingestionof fish or fish oil, dietary EPA and DHA may induce a decreased eicosanoidproduction by AA and reduce all the molecular responses related to the oxida-tive metabolism of AA in different ways including (a) the partial replacementof AA in cell membranes, since they compete with it for acylation in positionsn-2 of membrane phospholipids; (b) the direct competition of EPA and AA for

PLA2

AA EPA

2-series PGs2-series TXs

3-series PGs3-series TXs

COX-1COX-2

4-series LTs 5-series LTs

5 LOX 12-LOX 15- LOX

PLA2

AA EPACOX-1COX-2

5 LOX 12-LOX 15- LOX

Fig. 2 Competition between arachidonic acid (AA) and eicosapentaenoic acid (EPA) forcyclooxygenases (COX) and lipoxygenases (LOX). Phospholipase A2 (PLA2) catalyzes thehydrolysis of membrane phospholipids to release free AA and EPA. Afterward, free AA and EPAare converted by the same enzyme COX and LOX to their oxygenated metabolites prostaglandins(PGs), tromboxanes (TXs), and leukotrienes (LTs), collectively named eicosanoids. AA- andEPA-derived eicosanoids possess different biological activities. Plenty of works have shown pro-inflammatory and pro-carcinogenic activities for AA-derived eicosanoids (see the text for furtherdetails)

G. Calviello and S. Serini xiii

COX and 5-LOX, and production of EPA-derived eicosanoids (3-series TX, 3-series PG, and 5-series LT), which show lower biological activity than AA-derivedeicosanoids [9] (Fig. 2); (c) the EPA- and DHA-induced reduction of COX-2, theinducible form of COX, which is expressed mainly during inflammation and tumorgrowth [10, 11].

Moreover, recently it was found that both EPA and DHA may be metab-olized to previously unknown potent bioactive (in the nM range) eicosanoidand docosanoid products with anti-inflammatory and protective properties [12].They have been comprised in the classes of resolvins, docosatriens, and pro-tectins. Resolvins derived from EPA and DHA are named resolvins E andD [13]. DHA is the parent compound for docosatrienes, containing conju-gated triene structures [14]. “Neuroprotectins” indicate docosatrienes and D-seriesresolvins that have been shown to exert neuroprotective and anti-inflammatoryactions [14]. Aspirin can trigger in vivo the synthesis of a further highly activeseries of these compounds (17 R–D-series resolvins and docosatrienes) [14](Fig. 3).

PLA2

AspirinCOX-2

LOX

ResolvinsE-series (E1 and E2) 17S-Resolvins

D-series (RvD1-D4)

Protectin D1/ Neuroprotectin D1

DHA

17R-ResolvinsD-series(AT RvD1-D4)

EPA

MicrobialP450 LOX

LOX

PLA2PLA2

AspirinCOX-2

LOX

ResolvinsE-series (E1 and E2) -

DHAEPA

MicrobialP450 LOX

LOX

Fig. 3 Formation of novel discovered potent bioactive eicosanoids and docosanoids from eicos-apentaenoic acid (EPA) and docosahexaenoic acid (DHA). The figure reports the recent acqui-sitions according to which EPA and DHA may be metabolized to previously unknown novelcompounds (named resolvins and protectins) with high potency as anti-inflammatory and pro-resolving agents [see the text and Ref. [13] for further details]. PLA2: phospholipase A2; COX:cyclooxygenase; LOX: lipoxygenase

xiv Introduction: Omega-3 PUFAs, Why Do We Speak About Them?

Dietary Sources and Bioavailability of ω-3 PUFAs

Fatty fish is a good natural source for the long-chain ω-3 PUFAs EPA and DHA.Fish oil supplements are other sources artificially added to the diet and include fishoil capsules containing high levels of EPA and/or DHA and food enriched with fishoils. Recently, given the possible contamination of marine fish, effort has been madeto obtain purified ω-3 PUFAs from a source different from fish, and algal oils havebeen obtained from cultured microalgae, which could represent a quite safe andconvenient source of non-fish-derived ω-3 PUFAs. Recently also walnuts have beenconsidered a good source of ω-3 fatty acids [15], being rich in ALA. Even thoughthe conversion of ALA into longer ω-3 PUFAs (see above) is generally consideredlow, it has been shown that a moderate consumption of walnuts (4 walnuts/day for 3weeks) markedly increases the blood levels of ALA and of its metabolic derivative,EPA. Probably, as suggested by the authors, plant ALA, at the high levels found inappropriate food items, such as walnuts, may favorably affect the ω-3 long-chainPUFA status.

Bioavailability of ω-3 PUFAs is generally evaluated measuring their amount orconcentrations in total lipids or lipid fractions (free fatty acids, triglycerides, phos-pholipids, cholesterol esters) in plasma, serum, lymph, platelets, and red blood cellsas well as in the tissues under study. For instance, if we consider plasma total lipids,high amount of ω-3 PUFAs may be incorporated into them. For instance, start-ing from a basal serum total lipid level of about 20 μM EPA and 80 μM DHA inhumans [16], a dietary fish oil supplementation (3.0 g/day EPA + DHA) or dailyservings of salmon (1.2 g/day EPA + DHA) [17, 18] may allow an enrichment oftotal serum lipids ranging from 100 to 130% for EPA and from 25 to 45% for DHA.Even higher increases have been reported for total phospolipids after dietary sup-plementation with EPA + DHA ethyl esters (1.9 and 0.9 g/day, respectively) (250%for EPA and 40% for DHA) [17, 18]. However, a not completely clarified aspect ofPUFA metabolism is what is the best ω-3 PUFA source to obtain an optimal absorp-tion. It was recently shown that, irrespective of the source of ω-3 PUFAs present informula supplements for infants (either egg PL or low EPA fish oil and fungal TG),the concentrations of EPA and DHA achieved in the different infant lipid plasmafractions (total PL, TG, and CE) were very similar [19]. Accordingly, the intake ofequivalent doses of EPA and DHA given either as a mixture of EPA and DHA ethylesters or as a natural fish oil (containing mainly ω-3 PUFAs esterified to TG) ledto similar serum levels of EPA and DHA in adults [20]. However, recently, it wasfound that high concentrations of ω-3 PUFAs in plasma were achieved better if thedietary source of these fatty acids was fish (containing mainly ω-3 PUFAs esterifiedin glycerol lipids), rather than capsules containing ω-3 PUFA ethyl esters [18–22]. Recently it was also reported that algal-oil DHA capsules and cooked salmonwere bioequivalent in providing DHA to plasma and red blood cells [23]. Eventhough levels of EPA and DHA in serum or plasma lipids may give important infor-mation regarding the bioavailability of these fatty acids, recently the enrichmentof erythrocyte membranes (the so called ω-3 index) has been considered a betterbiomarker for ω-3 PUFAs [24], at least to establish the risk of coronary heart disease

G. Calviello and S. Serini xv

mortality, especially sudden cardiac death. Also in other pathologic fields this indexmay be useful, mirroring the incorporation of these FA in cell membranes of otherbody districts, where ω-3 PUFAs may actually produce their beneficial effects. Theuse of this index appears interesting, since it is just the membrane enrichment withω-3 PUFAs which is often considered crucial to explain their beneficial effects.Moreover, according to many authors, the membrane ω-3/ω-6 PUFA ratio has beenconsidered even a better index to explain their beneficial effects [25].

Beneficial Effects of ω-3 PUFAs on Human Health

Currently, the beneficial action of ω-3 polyunsaturated fatty acids (PUFAs) in can-cer prevention, therapy, and cachexia is supported by plenty of evidence that willbe examined in the following chapters with detail [26–30]. However, the first obser-vation of a possible beneficial healthy effect of ω-3 PUFAs, dating back to aboutfour decades ago, was the relationship existing between the low mortality fromcardiovascular diseases of Greenland Inuit populations and their high consump-tion of fish [31]. Nowadays, the role of ω-3 PUFAs as nutritional factors with thepotential to prevent the incidence as well as to lower the progression of differentchronic pathologic conditions has been well established. Most of the results havebeen obtained in the cardiovascular field, and now it is well recognized that ω-3PUFAs beneficially improve dyslipidemias, especially lowering plasma levels oftriglycerides [32]. Moreover, it has been proven that they slightly decrease bloodpressure [33], inhibit the formation of atherosclerotic plaque [34], and reduce therisk of sudden death [35], cardiac arrhythmias [36], and stroke [37] in individualswith established cardiac pathologies. Furthermore, they can be useful in prevent-ing the pathological vascular complications of diabetes [38]. On this basis, manynutritionist and cardiologist agencies worldwide agree in recommending at leasttwo or three fish portions/week for the primary and secondary prevention of cardio-vascular diseases and supplementations of ω-3 PUFAs as fish oil extracts [39–41].Consequently, the prescription of fish oil capsules has currently become commonin clinical cardiology practice. The increased sales of drinks and food products for-tified with ω-3 PUFAs worldwide also demonstrate the extreme popularity of thenotion that ω-3 PUFAs exert various health effects. Recently, their dietary intakehas been also recommended during pregnancy and lactation [4, 42] since it hasbeen established that ω-3 PUFAs exert crucial effects on growth and neurologi-cal development of fetuses and newborn infants [43, 44]. Plenty of data have beenpublished on the subject, and it has been shown that maternal plasma phospolipid(PL) concentration of PUFAs increases during pregnancy, probably mobilized frommaternal stores [45]. Especially DHA increases in plasma PL, and this is relatedto the fact that fetus needs PUFAs, especially DHA, for the normal developmentof its brain and retina [46, 47]. It has been shown that during pregnancy womenmay become increasingly deficient in DHA [45], and probably the maternal capac-ity to meet the high fetal requirement for DHA [48] may work at its limits or

xvi Introduction: Omega-3 PUFAs, Why Do We Speak About Them?

even be inadequate. Moreover, observational and interventional studies have clar-ified the positive influence of ω-3 PUFAs on gestation length, birth weight, and riskfor early premature birth [49]. Consensus recommendations and practice guidelinesfor pregnancy supported by different health agencies have been recently reviewed[50]. On the basis of all the recommendations published, the aim to be achievedby pregnant and lactating women should be an average daily intake of at least200 mg DHA. In spite of that, as demonstrated by a study recently carried out[51], there is not enough awareness of the importance of ω-3 PUFA consumptionduring pregnancy among pregnant women, and the limited knowledge obtained bywomen derived mostly from popular books and magazines. Moreover, the impor-tance of an increased dietary intake of ω-3 PUFAs has been recently recognizedfor the prevention of neurodegenerative pathologies [52, 53]. Epidemiological stud-ies have indicated the possibility that dietary EPA and DHA may modify the riskand progression of Alzheimer’s disease (AD). In particular, longitudinal prospec-tive studies have shown the inverse relationship existing between fish intake andAD dementia [54–57] and cross-sectional analyses have linked low levels of DHAin plasma lipids or phospholipid DHA levels and a low ω-3 PUFA/ω-6 PUFA ratioin the erythrocyte membranes with cognitive decline, dementia, and AD in partic-ular [58–61]. Moreover, a series of experimental studies on mouse models of ADhave investigated the role of ω-3 PUFAs in the development of AD. These stud-ies demonstrated that pre-administration of DHA to rats infused with the amyloidpeptide Aβ1-40, whose formation in brain is considered crucial in the pathogene-sis of AD, had profoundly beneficial effects in decreasing the decline of learningability [62]. Also experiments with different transgenic rat models of AD showedunivocally that the dietary supplementation with DHA decreased the levels of Aβ

[63–66] improving the animal cognitive functions. Similarly, their benefits havebeen demonstrated in immunity and inflammatory disorders [67, 68]. They haveshown to decrease colonic damage and inflammation, weight loss, and mortality inanimal models of colitis [69]; to reduce joint inflammation; and to improve clini-cal symptoms in subjects affected by rheumatic diseases, in particular, rheumatoidarthritis (RA) [70]. They are thought to exert their action modifying the inflam-matory lipid mediator profile, leukocyte chemotaxis, and inflammatory cytokineproduction [69].

Studies on ω-3 PUFAs and Cancer: Discrepancies Betweenthe results of In Vitro and In Vivo Experimental Studiesand Human Observational Studies

Very interesting results have been obtained with ω-3 PUFAs also in the oncologyfield, and they will represent the subject of the following chapters. However, on thebasis of the results analyzed in this book, it will appear clear that many inconsis-tencies exist among the epidemiological observational studies examining the risk

G. Calviello and S. Serini xvii

of different kinds of cancer in human populations ingesting variable amounts offood containing ω-3 PUFAs. This seems quite intriguing, considering that, on thecontrary, the results of all the experimental studies clearly and univocally indicatethe powerful anti-tumor effectiveness of ω-3 PUFAs. A number of reasons mayprobably concur to create this discrepancy. In Chapters 2 and 4, the limitations suf-fered by the epidemiological studies in defining the actual level of daily dietaryintake of ω-3 PUFAs on the basis of the consumption of fish or other dietary sourcesof these fatty acids will be examined in detail. It should be underlined, however, thatin many studies also the ω-3 PUFA concentration in red blood cells, serum, or adi-pose tissue is often used as an objective biomarker of fatty acid intake. To try toexplain these discrepancies it may be also useful to consider the interesting recentlyprospected possibility that the anti-tumoral effect of these fatty acids among thehuman population may vary in dependence on the possession of individual geneticfeatures, and that high intakes of ω-3 PUFAs would be associated with a lower riskof neoplasia only among those individuals with genetic variants associated with aparticular type of cancer [71]. This possibility will be treated in Chapter 5 as far asprostate cancer is concerned.

Controlled and definite concentrations of ω-3 PUFAs are instead adminis-tered to cultured cells and animals in the experimental studies [26]. It is alsotrue that, in a very few studies, the concentrations used in vitro are higherthan those achievable in plasma of human populations, even of high fishconsumers.

Moreover, it should not be underestimated that a long-term dietary intake offishes may supply concomitantly both ω-3 PUFAs and carcinogenic compounds,which, as well known, often contaminate fish tissues. It has become clear that notonly wild fish but also farmed fatty fish which are commonly bred and eaten, suchas salmon, may be highly contaminated by carcinogens such as pesticides [72].For instance, organochlorine pesticides may accumulate easily in fatty fishes andexert carcinogenic effects, particularly enhancing the risk of hormone-dependentforms of cancers [29]. Thus, the concomitant intake may complicate the interpre-tation of the epidemiological studies, especially those regarding breast and prostatecancers, which may be induced by the organochlorine pesticides. The lack of agree-ment among epidemiological observational results represents a big drawback andmay help to explain why just a few number of clinical intervention trials withω-3 PUFAs have been so far performed in patients at risk for cancer, especiallyif compared to those conducted in cardiovascular patients. In view of the possi-ble carcinogen contamination of fish tissues, highly purified PUFAs, oils rich inω-3 PUFAs or fish from uncontaminated sources should be used for interventiontrials and prevention studies. To this aim, alternative and safer, but still natural,ω-3 PUFA sources, such as cultured microalgae have been proposed [73, 74].Recently, we indicated an artificial lake, whose waters were subject to constantpurification and almost free of pollutants, as a model of basin which could furnishuncontaminated fish, particularly indicated for pregnant women and infants afterweaning [75].

xviii Introduction: Omega-3 PUFAs, Why Do We Speak About Them?

Effect of ω-3 PUFAs in Cancer: Organization of the Present Book

The present book was designed to cover in an exhaustive way all the main aspectsconcerning the possible effects of ω-3 PUFAs against cancer. To this aim, the firstchapter will analyze the mechanisms of ω-3 PUFA anti-tumoral action. Chapters2 and 3 will treat the effects of ω-3 PUFAs against some of the most frequentcancers among Western population, namely colon cancer and hormone-related can-cers (breast and prostate cancer), all of them proven to be sensitive to dietarychemoprevention. Separate sections inside Chapters 2 and 3 will cover experi-mental studies, including those performed on animal, cell culture models, humaninterventional studies, and human epidemiological observational studies. Chapter4 will provide the available information regarding the effects of ω-3 PUFAs onother kinds of cancers. Afterward, a subject of great interest at the moment will betreated (Chapter 5), namely the possible use of ω-3 PUFAs in combination withconventional anti-cancer agents. Finally, the anticachetic potential of these dietarycompounds will be analyzed.

References

1. Sprecher H. New advances in fatty-acid biosynthesis. Nutrition 1996; 12(1 Suppl):S5–S7.2. Sprecher H, Luthria DL, Mohammed BS, Baykousheva SP. Reevaluation of the pathways for

the biosynthesis of polyunsaturated fatty acids. J Lipid Res 1995; 36(12):2471–7.3. Salem N Jr, Wegher B, Mena P, Uauy R. Arachidonic and docosahexaenoic acids are biosyn-

thesized from their 18-carbon precursors in human infants. Proc Natl Acad Sci USA 1996;93(1):49–54.

4. McCann JC, Ames BN. Is docosahexaenoic acid, an n-3 long-chain polyunsaturated fatty acid,required for development of normal brain function? An overview of evidence from cognitiveand behavioral tests in humans and animals. Am J Clin Nutr 2005; 82(2):281–95.

5. Simopoulos AP. Evolutionary aspects of diet, the omega-6/omega-3 ratio and genetic varia-tion: nutritional implications for chronic diseases. Biomed Pharmacother 2006; 60(9):502–7.

6. Samuelsson B, Dahlen SE, Lindgren JA, Rouzer CA, Serhan CN. Leukotrienes and lipoxins:Structures, biosynthesis, and biological effects. Science 1987; 237(4819):1171–6.

7. Funk CD. Prostaglandins and leukotrienes: advances in eicosanoid biology. Science 2001;294(5548):1871–5.

8. Karmali RA. Eicosanoids in neoplasia. Prev Med 1987; 16(4) 493–502.9. Lands WE. Biochemistry and physiology of n-3 fatty acids. FASEB J 1992; 6(8):2530–6.

10. Swamy MV, Cooma I, Patlolla JM, Simi B, Reddy BS, Rao CV. Modulation ofcyclooxygenase-2 activities by the combined action of celecoxib and decosahexaenoicacid: Novel strategies for colon cancer prevention and treatment. Mol Cancer Ther 2004;3(2):215–21.

11. Tapiero H, Ba GN, Couvreur P, Tew KD. Polyunsaturated fatty acids (PUFA) and eicosanoidsin human health and pathologies. Biomed Pharmacother 2002; 56(5):215–22.

12. Serhan CN. Novel eicosanoid and docosanoid mediators: Resolvins, docosatrienes, andneuroprotectins. Curr Opin Clin Nutr Metab Care 2005; 8(2): 115–21.

13. Serhan CN, Chiang N. Endogenous pro-resolving and anti-inflammatory lipid mediators: anew pharmacologic genus. Br J Pharmacol 2008; 153(Suppl 1):S200–15.

14. Serhan CN, Arita M, Hong S, Gotlinger K. Resolvins, docosatrienes, and neuroprotectins,novel omega-3-derived mediators, and their endogenous aspirin-triggered epimers. Lipids2004; 39(11):1125–32.

G. Calviello and S. Serini xix

15. Marangoni F, Colombo C, Martiello A, Poli A, Paoletti R, Galli C. Levels of the n-3 fatty acideicosapentaenoic acid in addition to those of alpha linolenic acid are significantly raised inblood lipids by the intake of four walnuts a day in humans. Nutr Metab Cardiovasc Dis 2007;17(6):457–61.

16. Harper CR, Edwards MJ, De Filippis AP, Jacobson TA. Flaxseed oil increases the plasmaconcentrations of cardioprotective (n-3) fatty acids in humans. J Nutr 2006; 136(1); 83–7.

17. Cao J, Schwichtenberg KA, Hanson NQ, Tsai MY. Incorporation and clearance of omega-3 fatty acids in erythrocyte membranes and plasma phospholipids. Clin Chem 2006;52(12):2265–72.

18. Elvevoll EO, Barstad H, Breimo ES, Brox J, Eilertsen KE, Lund T, et al. Enhanced incorpo-ration of n-3 fatty acids from fish compared with fish oils. Lipids 2006; 41(12):1109–14.

19. Sala-Vila A, Castellote AI, Campoy C, Rivero M, Rodriguez-Palmero M, López-SabaterMC. The source of long-chain PUFA in formula supplements does not affect the fatty acidcomposition of plasma lipids in full-term infants. J Nutr 2004; 134(4):868–73.

20. Krokan HE, Bjerve KS, Mørk E. The enteral bioavailability of eicosapentaenoic acid anddocosahexaenoic acid is as good from ethyl esters as from glyceryl esters in spite of lowerhydrolytic rates by pancreatic lipase in vitro. Biochim Biophys Acta 1993; 1168(1):59–67.

21. Cobiac L, Clifton PM, Abbey M, Belling GB, and Nestel PJ. Lipid, lipoprotein, and hemo-static effects of fish vs. fish-oil n-3 fatty acids in mildly hyperlipidemic males. Am J Clin Nutr1991; 53(5):1210–6.

22. Visioli F, Risé P, Barassi MC, Marangoni F, Galli C. Dietary intake of fish vs. formulationsleads to higher plasma concentrations of n-3 fatty acids. Lipids 2003; 38(4):415–8.

23. Arterburn LM, Oken HA, Bailey Hall E, Hamersley J, Kuratko CN, Hoffman JP. Algal-oilcapsules and cooked salmon: nutritionally equivalent sources of docosahexaenoic acid. J AmDiet Assoc 2008; 108(7):1204–9.

24. Harris WS. The omega-3 index as a risk factor for coronary heart disease. Am J Clin Nutr2008; 87(6):1997S–2002S.

25. Hibbeln JR, Salem N Jr. Dietary polyunsaturated fatty acids and depression: when cholesteroldoes not satisfy. Am J Clin Nutr 1995; 62(1):1–9.

26. Calviello G, Serini S, Palozza P. n-3 polyunsaturated fatty acids as signal transductionmodulators and therapeutical agents in cancer. Curr Signal Transduct Ther 2006; 1:255–71.

27. Calviello G, Serini S, Piccioni E. n-3 Polyunsaturated fatty acids and the prevention ofcolorectal cancer: molecular mechanisms involved. Curr Med Chem 2007; 14(29):3059–69.

28. Calviello G, Serini S, Piccioni E, Celleno L. Beneficial effects of n-3 PUFAs on UV-inducedSkin Damage and tumorigenesis. In: Eetu P. Heikkinen, ed. Fish Oils and Health, NovaScience Publishers. New York, 2008, pp. 141–58.

29. Terry PD, Rohan TE, Wolk A. Intakes of fish and marine fatty acids and the risks of cancersof the breast and prostate and of other hormone-related cancers: a review of the epidemiologicevidence. Am J Clin Nutr 2003; 77(3):532–43.

30. Brown TT, Zelnik DL, Dobs AS. Fish oil supplementation in the treatment of cachexia inpancreatic cancer patients. Int J Gastrointest Cancer 2003; 34(2–3):143–50.

31. Dyerberg J. Coronary heart disease in Greenland Inuit: a paradox. Implications for westerndiet patterns. Arctic Med Res 1989; 48(2):47–54.

32. Kinsella JE, Lokesh B, Stone RA. Dietary n-3 polyunsaturated fatty acids and amelioration ofcardiovascular disease: possible mechanisms. Am J Clin Nutr 1990; 52(1):1–28.

33. Mozaffarian D. Fish, n-3 fatty acids, and cardiovascular haemodynamics. J Cardiovasc Med(Hagerstown) 2007; 8(Suppl 1):S23–6.

34. De Caterina R, Massaro M. Omega-3 fatty acids and the regulation of expression ofendothelial pro-atherogenic and pro-inflammatory genes. J Membr Biol 2005; 206(2):103–16.

35. Russo GL. Dietary n-6 and n-3 polyunsaturated fatty acids: From biochemistry to clinicalimplications in cardiovascular prevention. Biochem Pharmacol 2009; 77(6):937–46.

36. Xiao YF, Sigg DC, Leaf A. The antiarrhythmic effect of n-3 polyunsaturated fatty acids: mod-ulation of cardiac ion channels as a potential mechanism. J Membr Biol 2005; 206(2):141–54.

xx Introduction: Omega-3 PUFAs, Why Do We Speak About Them?

37. Bouzan C, Cohen JT, Connor WE, Kris-Etherton PM, Gray GM, König A, et al. A quantitativeanalysis of fish consumption and stroke risk. Am J Prev Med 2005; 29(4):347–52.

38. Nettleton JA, Katz R. n-3 long-chain polyunsaturated fatty acids in type 2 diabetes: a review.J Am Diet Assoc 2005; 105(3):428–40.

39. Gebauer SK, Psota TL, Harris WS, Kris-Etherton PM. n-3 fatty acid dietary recommendationsand food sources to achieve essentiality and cardiovascular benefits. Am J Clin Nutr 2006;83(6 Suppl):1526S–35S.

40. Breslow JL. n-3 fatty acids and cardiovascular disease. Am J Clin Nutr 2006; 83(6Suppl):1477S–82S.

41. Lombardo YB, Chicco AG. Effects of dietary polyunsaturated n-3 fatty acids on dyslipidemiaand insulin resistance in rodents and humans. J Nutr Biochem 2006; 17(1):1–13.

42. Jensen CL. Effects of n-3 fatty acids during pregnancy and lactation. Am J Clin Nutr 2006;83(6 Suppl):1452S–7S.

43. Makrides M, Gibson RA. Long-chain polyunsaturated fatty acid requirements during preg-nancy and lactation. Am J Clin Nutr 2000; 71(1 Suppl):307S–11S.

44. Sattar N, Berry C, Greer IA. Essential fatty acids in relation to pregnancy complications andfetal development. Br J Obstet Gynaecol 1998; 105(12):1248–55.

45. Al MD, van Houwelingen AC, Kester AD, Hasaart TH, de Jong AE, Hornstra G. Maternalessential fatty acid patterns during normal pregnancy and their relationship to the neonatalessential fatty acid status. Br J Nutr 1995; 74(1):55–68.

46. Martinez M. Dietary poly-unsaturated fatty acids in relation to neural development in humans.Progr Lipid Res 1989; 28: 123–33.

47. Makrides M, Simmer K, Goggin M, Gibson RA. Erythrocyte docosahexaenoic acid correlateswith the visual response of healthy, term infants. Pediatr Res 1993; 33(4):425–7.

48. Innis SM. Essential fatty acids in growth and development. Prog Lipid Res 1991; 30(1):39–103.

49. Cetin I, Koletzko B. Long-chain omega-3 fatty acid supply in pregnancy and lactation. CurrOpin Clin Nutr Metab Care 2008; 11(3):297–302.

50. Koletzko B, Lien E, Agostoni C, Böhles H, Campoy C, Cetin I, et al. The roles of long-chainpolyunsaturated fatty acids in pregnancy, lactation and infancy: review of current knowledgeand consensus recommendations. J Perinat Med 2008; 36(1):5–14.

51. Sinikovic DS, Yeatman HR, Cameron D, Meyer BJ. Women’s awareness of the impor-tance of long-chain omega-3 polyunsaturated fatty acid consumption during pregnancy:Knowledge of risks, benefits and information accessibility. Public Health Nutr 2009; 12(4):562–9.

52. Alessandri JM, Guesnet P, Vancassel S, Astorg P, Denis I, Langelier B,et al. Polyunsaturatedfatty acids in the central nervous system: evolution of concepts and nutritional implicationsthroughout life. Reprod Nutr Dev 2004; 44(6):509–38.

53. Friedland RP. Fish consumption and the risk of Alzheimer disease: is it time to make dietaryrecommendations? Arch Neurol 2003; 60(7):923–4.

54. Kalmijn S, Launer LJ, Ott A, Witteman JC, Hofman A, Breteler MM. Dietary fat intakeand the risk of incident dementia in the Rotterdam Study. Ann Neurol 1997; 42(5):776–82.

55. Barberger-Gateau P, Letenneur L, Deschamps V, Peres K, Dartigues JF, Renaud S. Fish, meat,and risk of dementia: Cohort study. BMJ 2002; 325(7370):932–3.

56. Morris MC, Evans DA, Bienias JL, Tangney CC, Bennett DA, Wilson RS, et al. Consumptionof fish and n-3 fatty acids and risk of incident Alzheimer disease. Arch Neurol 2003;60(7):940–6.

57. van Gelder BM, Tijhuis M, Kalmijn S, Kromhout D. Fish consumption, n-3 fatty acids, andsubsequent 5-y cognitive decline in elderly men: the Zutphen Elderly Study. Am J Clin Nutr2007; 85(4):1142–7.

58. Soderberg M, Edlund C, Kristensson K, Dallner G. Fatty acid composition of brain phospho-lipids in aging and in Alzheimer’s disease. Lipids 1991; 26(6):421–5.

G. Calviello and S. Serini xxi

59. Conquer JA, Tierney MC, Zecevic J, Bettger WJ, Fisher RH. Fatty acid analysis ofblood plasma of patients with Alzheimer’s disease, other types of dementia, and cognitiveimpairment. Lipids 2000; 35(12):1305–12.

60. Schaefer EJ, Bongard V, Beiser AS, Lamon-Fava S, Robins SJ, Au R, et al. Plasma phos-phatidylcholine docosahexaenoic acid content and risk of dementia and Alzheimer disease:the Framingham Heart Study. Arch Neurol 2006; 63(11):1545–50.

61. Heude B, Ducimetiere P, Berr C. EVA Study. Cognitive decline and fatty acid composition oferythrocyte membranes – The EVA Study. Am J Clin Nutr 2003; 77(4):803–8.

62. Hashimoto M, Hossain S, Shimada T, Sugioka K, Yamasaki H, Fujii Y, et al. Docosahexaenoicacid provides protection from impairment of learning ability in Alzheimer’s disease modelrats. J Neurochem 2002; 81(5):1084–91.

63. Cole GM, Frautschy SA. Docosahexaenoic acid protects from amyloid and dendritic pathol-ogy in an Alzheimer’s disease mouse model. Nutr Health 2006; 18(3):249–59.

64. Calon F, Lim GP, Yang F, Morihara T, Teter B, Ubeda O, et al. Docosahexaenoic acidprotects from dendritic pathology in an Alzheimer’s disease mouse model. Neuron 2004;43(5):633–45.

65. Lim GP, Calon F, Morihara T, Yang F, Teter B, Ubeda O, et al. A diet enriched with the omega-3 fatty acid docosahexaenoic acid reduces amyloid burden in an aged Alzheimer mouse model.J Neurosci 2005; 25(12):3032–40.

66. Oksman M, Iivonen H, Hogyes E, Amtul Z, Penke B, Leenders I, et al. Impact of different sat-urated fatty acid, polyunsaturated fatty acid and cholesterol containing diets on beta-amyloidaccumulation in APP/PS1 transgenic mice. Neurobiol Dis 2006; 23(3):563–72.

67. Calder PC. n-3 polyunsaturated fatty acids, inflammation, and inflammatory diseases. Am JClin Nutr 2006; 83(6 Suppl):1505S–19S.

68. Wong KW. Clinical efficacy of n-3 fatty acid supplementation in patients with asthma. J AmDiet Assoc 2005; 105(1):98–105.

69. Calder PC. Polyunsaturated fatty acids, inflammatory processes and inflammatory boweldiseases. Mol Nutr Food Res 2008; 52(8):885–97.

70. Proudman SM, Cleland LG, James MJ. Dietary omega-3 fats for treatment of inflammatoryjoint disease: efficacy and utility. Rheum Dis Clin North Am 2008; 34(2):469–79.

71. Poole EM, Bigler J, Whitton J, Sibert JG, Kulmacz RJ, Potter JD, et al. Genetic variabilityin prostaglandin synthesis, fish intake and risk of colorectal polyps. Carcinogenesis 2007;28(6):1259–63.

72. Hites RA, Foran JA, Schwager SJ, Knuth BA, Hamilton MC, Carpenter DO. Global assess-ment of polybrominated diphenyl ethers in farmed and wild salmon. Environ Sci Technol2004; 38(19):4945–9.

73. Sijtsma L, de Swaaf ME.Biotechnological production and applications of the omega-3 polyun-saturated fatty acid docosahexaenoic acid. Appl Microbiol Biotechnol 2004; 64(2):146–53.

74. Pulz O, Gross W. Valuable products from biotechnology of microalgae. Appl MicrobiolBiotechnol 2004; 65(6):635–648.

75. Calviello G, Serini S, Piccioni E, Rinaldi C, Mostra D, Damiani G. Fish species liv-ing in an artificial lake with high quality waters as an optimal source of n-3 PUFAs.http://www.issfal.org.uk/pufa-recommendations.html