Krebs und ErnährungSchutz und Risikofaktoren

Prof. Dr. Siegfried Knasmüller

Institut für Krebsforschung

Medizinische Universität Wien

1

Themen

• Einleitung

• Risikofaktoren

• Stabilisierende Faktoren

• Schutzfaktoren

2

Einleitung

3

In Nahrungsmitteln wurden zahlreiche Substanzen detektiert die in Versuchstieren Krebs auslösen

• Polyzyklische Kohlenwasserstoffe (PAKs)

• Heterozyklische aromatische Amine

• Nitrosamine

• Weitere Zersetzungsprodukte (Acrylamid, Furan, 5-Hydroxymethylfurfural)

• Schwermetalle

• Bestimmte Zusatzstoffe

• Pestizide und Herbizide

• PCBs und Dioxine

• Pilzgifte

• Pflanzliche Inhaltsstoffe

4

Entgiftung

Viele dieser Substanzen werden im menschlichen Körper durch Phase I-Enzyme aktiviert und durch Phase II-Enzyme entgiftet

5

Nitrosamine (NDEA)

CH3

CH3

N N O

Polyzyklische aromatische Kohlenwasserstoffe (B(a)P)

Heterozyklische aromatische Amine

(PhiP)

N

N

N

NH2

CH3

Aflatoxine (AFB1)

O

O

O

O O

OCH3H

H

CYP2E1 CYP1A1

NAT/OAT

CYP1A2 CYP3A4

GSTUGT SULT

DNA

Phase II

Phase I

“Natural pesticides“

Auch “gesunde“ pflanzliche Nahrungsmittel enthalten gentoxische Kanzerogene

6

Pflanzliche Kanzerogene

7

Einige besonders intensiv erforschte Verbindungen sind in Fleisch enthalten

Polyzyklische aromatische Heterozyklische aromatische Nitrosamine

Kohlenwasserstoffe Amine

B(a)P Phip NDEA

N

N

N

NH2

CH3

CH3

CH3

N N O

8

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Tatsächlich stellt der Verzehr von Fleisch einKrebsrisiko dar.

Fleischverzehr

• Deutschland: 61 kg/Kopf/Jahr

• Österreich: 67 kg/Kopf/Jahr

75-80% Schweinefleisch in Mitteleuropa

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Kolorektalkrebs

In drei großen Metaanaylsen wurden die Resultate von pro- und retrospektiven Studien ausgewertet. Norat und Kollegen (2002) wählten aufgrund definierter Kriterien aus 48 Studien 23 besonders sorgfältig durchgeführte Untersuchungen aus. Sie kommen zu dem Schluss, dass in der höchsten Quintile (94-126 g rotes Fleisch pro Tag) das Dickdarmkrebsrisiko um 35% erhöht ist. Diese Aussage betrifft den Konsum von verarbeitetem und unverarbeitetem Fleisch; betrachtet man lediglich unverarbeitetes Fleisch, ist der Zusammenhang immer noch signifikant.

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Wie gefährlich sind die einzelnen Faktoren?Risikoabschätzung von Lutz & Schlatter (1992)

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Besonders relevant:

• Alkohol

• Übergewicht

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Alkoholkonsum in Deutschland/Kopf/Jahr

• Bier: 150 l

• Wein: 25 l

• Spirituosen: 6 l

• Frankreich: 80l Wein/Kopf/Jahr

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Verstoffwechslungvon Alkohol

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Krebsauslösung durch Alkohol: Mechanismen

Synergieeffekte – Rauchen und Alkoholkonsum

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Übergewicht

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Extrapolation of the results of the BIOSAFE study (W.K.Lutz, Mutat. Res., 1999)

• Additional feed per day per animal: 3.2 g males, 2.9 g females

• Increase of tumor incidence 23 % in males and 18 % in females

• TD 50 value 16 g/kg/d

• Caloric over nutrition in Switzerland 5.5 kcal/d equivalent to 1.9 g/kg bw. Estimated increase of deaths due to diet related cancers 60.000 per Million !!!!!!!!!!!

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Obesity is at present exploding in human populations (also pets such as dogs cats and birds become obese !!!!!!)

• In 2030 1350 million people will have overweight (BMI 25-29.9)

• … and 573 million people will suffer from adipositas (BMI ≥ 30)

(Kelly T., Yang W., Chen C. S., Reynolds K., He J. (2008). Global burden of obesity in 2005 and projections to 2030. Int. J. Obes. (Lond.) 32, 1431–1437 )

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Abb.xx Verteilung von Adipositas und Übergewicht in verschiedenen Ländern(Quelle: WHO, http://apps.who.int/bmi/index.jsp). 21

22

Mechanismen der Krebsauslösung durch Übergewicht

Longo VD et al. Calorie restriction and cancerprevention: metabolic and molecularmechanisms trends Pharmacol Sci 2010;31: 89-98

23

Betroffene Organe: Männer

Callee EE et al. Overweight, obesity andmortality from cancer in a prospectivelystudied cohort of U.s. adults. N Engl J Med2003; 348: 1625-1638

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Betroffene Organe: FrauenCallee EE et al. Overweight, obesity andmortality from cancer in a prospectivelystudied cohort of U.s. adults. N Engl J Med2003; 348: 1625-1638

Internationales Abkommen gefordert

Schlechte Ernährung wirdnach Ansicht von UNO-Experten zu einem immergrößeren Gesundheitsrisikofür viele Menschen.

„Ein Teil der Welt isst sich imwahrsten Sinne des Worteszu Tode“, warntedie Generaldirektorin der

Weltgesundheitsorganisation(WHO), Margaret Chan, EndeMai (2014) in Genf.

25

Die Ergebnisse der “Margin of Exposure“ Berechnungen bestätigen die Annahme der relativ geringen Relevanz chemischer Kanzerogene in unseren Nahrungsmitteln.

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Some MOE values for dietary carcinogens

Compound Exposure MOE

B(a)P Food overall 20 000

PhiP Food overall - prostate 80 000

PhiP Food overall - breast 10 000

NDMA Bacon (20g) - sns 10 000

IQ Hamburger (85g) - sns 1 000 000

MeIQ Hamburger (85g) - sns 300 000

NPYR Bacon (20g) - sns 10 000

AFB1 Food overall liver 600 (!)

Acrylamid Food overall - sns 200

Lois Swirsky Gold, Bruce N. Ames, Thomas H. Slone. How Many Fold Lower Is Human Exposure Than the Dose That Gave Rodents Cancer: Margin of Exposure, MOE (Rodent Cancer Dose/Human Exposure). MOEtable.html, September 2008. pdfs/MOEtable.pdf. Benford et el. Food and Chemical Toxicology 48 (2010) S2–S24

27

Stabilisierende Faktoren

Anfang der 90er Jahre entstand eine neue Hypothese, die die Zusammenhänge zwischen Ernährung und Krebsauslösung betraf.

28

Bestimmte Vitamine und Spurenelemente die dermenschliche Körper benötigt und die nicht inausreichenden Mengen aufgenommen werden,bewirken eine Erhöhung des Erkrankungsrisikos.

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Stabilisierende Faktoren

Federführend waren B. Ames und M. Fenech

Nachweis, dass Folatmangel DNA-Instabilität auslöst

Vitamin B12 – Mangel führt ebenfalls zu Chromosomenschäden

Michael Fenech Bruce Ames

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Folsäure spielt bei der Synthese von DNA-Basen und bei der Methylierung von DNA-Basen eine zentrale Rolle

32

Eisen: ein “zwei- schneidiges“

Schwert33

Selen

34

Zink

35

Die täglichen Aufnahmemengenvon Spurenelementen und Vita-minen die zu optimalem Schutz vorKrebs und optimaler DNA Stabilitätführen sind derzeit nicht bekannt.

Die Festlegung der Aufnahme-mengen wurden basieren vor allemauf der Vermeidung von Mangel-erscheinungen.

Im Fall von Folsäure wurde gezeigt,dass die Mengen die erforderlichsind um chromosomale Schäden zuminimieren höher sind als die vonder DACH empfohlene täglicheZufuhr (300 µg/P/T).

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Schutzfaktoren

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Historisches

• 1960er Jahre: Schutz vor strahleninduzierten DNA-Schäden und Krebs durch S-haltige Aminosäuren und Vitamine.

• T. Kada: Suche nach DNA-protektiven Inhaltsstoffen in Pflanzen (u.a. Induktion von DNA-Reparaturenzymen).

• L. Wattenberg (Universität von Minnesota) Tierexperimente, Schutz vor PAKs.

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Schutzfaktoren

Nahrungsinhaltsstoffe die vor Chemikalien und anderen Faktoren schützen, die Krebs verursachen

• Schutz vor Radikalen

• Schutz vor krebsauslösenden Chemikalien

• Schutz vor weiteren Faktoren (z.B.: Übergewicht)

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Schutz vor Sauerstoffradikalen

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Knasmüller et al. BJN

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Knasmüller et al. BJN

Why do we believe that ROS cause cancer?

• Exposures which lead to ROS formation leads to cancer (e.g.peroxides and ionizing radiation which causes intracellular formationof ROS due to cleavage of water molecules.

• … all types of inflammations are associated with increased cancerrates (hepatitis, colitis, gastritis etc.).

• Mechanistically, it is known that ROS cause DNA damage which playsa key role in the etiology of cancer, furthermore there is also evidencethat they act as tumor promoters.

42

DNA damage occurs via direct oxidation of the DNA and indirectly (e.g. via lipid peroxidation)

lipid peroxidation

aldehydes

ketones

direct oxidation

of bases

base oxidation

ROS

mutations cancer

43

Knasmüller et al.Br J Nutr. 2008 99 E Suppl 1:ES3-52. doi: 10.1017/S0007114508965752.Use of conventional and -omics based methods for health claims of dietary antioxidants: a critical overview.

44

45

One of the most widely used approaches for human intervention trials are SCGE assays. By use of lesion specific restriction enzymes it is possible to detect oxidation of purines and pyrimidines .

Test cells with

chemical mutagens

„ex vivo“

Standard conditions

Isolate nuclei +

treat with lesion specific enzymesExperiments

concerning

repair

processes

Pre-damaged DNA Monitor comets

ROS

treatment

46

We detected protective effects with a variety of foods and individual compounds in these intervention studies

• Sumach: prevention of FPG and ENDO III lesions at a dose of 3 g/d (Chakraborty et al. Mutat Res. 2009 Feb 10;661(1-2):10-7)

• Gallic acid: prevention of FPG and ENDO III lesions at a dose of 12 mg/P/d (Ferk et al. Mutat Res. 2011 Oct 1;715(1-2):61-71)

• Xantohumol: prevention of FPG lesions, dose 12 mg/d (In preparation)

• Spinach prevention of oxidative lesions after intake of 220 g/P/d (Moser etal. Eur J Nutr. 2011 Oct;50(7): 587-94)

• Brussels sprouts: protection against oxidative lesions with 300 g/d (Hoelzlet al. Mol Nutr Food Res. 2008 Mar;52(3): 330-41)

• Coffee: prevention of oxidative lesions (Bichler et al. Food Chem Toxicol. 2007 Aug;45(8):1428-36; Misik et al. Mutat Res. 2010 Oct 13; 692(1-2):42-8)

47

With coffee and GA we demonstrated in animal models thatthey protect against induction of preneoplastic lesions bygamma radiation

cont 12Gy 12Gy0

5

10

15

20

25

30

35

40

45

50cont (No coffee and No Gamma-irradiation)

12Gy (Gamma-irradiation)

12Gy + coffee

n=8

n=8

n=12*

GS

T-p

+,

No

. o

f fo

ci/cm

2

cont 12Gy 12Gy0

5

10

15

20

25

30

35

40

45

50cont (No GA and no gamma-irradiation)

12Gy (Gamma-irradiation)

12Gy + GA

n=8

n=10

*

GS

T-P

+,

No

. o

f fo

ci/cm

2

48

… but do antioxidants protect humans against cancer ???

It was repeatedly claimed that vitamins A, C, E with are potent antioxidantsreduce the cancer incidence in humans, but the results of epidemiologicalstudies failed to confirm this hypothesis.

49

Sixty-seven randomised trials with 232,550 participants were included. Forty-seven trials including 180,938participants had low risk of bias. Twenty-one trials included 164,439 healthy participants. Forty-six trialsincluded 68111 participants with various diseases (gastrointestinal, cardiovascular, neurological, ocular,dermatological, rheumatoid, renal, endocrinological, or unspecified). Overall, the antioxidant supplementshad no significant effect on mortality in a random-effects meta-analysis (relative risk [RR] 1.02, 95%confidence interval [CI] 0.99 to 1.06), but significantly increased mortality in a fixed-effect model (RR 1.04,95% CI 1.02 to 1.06). In meta-regression analysis, the risk of bias and type of antioxidant supplement werethe only significant predictors of intertrial heterogeneity. In the trials with a low risk of bias, the antioxidantsupplements significantly increased mortality (RR 1.05, 95% CI 1.02 to 1.08). When the differentantioxidants were assessed separately, analyses including trials with a low risk of bias and excluding seleniumtrials found significantly increased mortality by vitamin A (RR 1.16, 95% CI 1.10 to 1.24), beta-carotene (RR1.07, 95% CI 1.02 to 1.11), and vitamin E (RR 1.04, 95% CI 1.01 to 1.07), but no significant detrimental effectof vitamin C (RR 1.06, 95% CI 0.94 to 1.20). Low-bias risk trials on selenium found no significant effect onmortality (RR 0.91, 95% CI 0.76 to 1.09).

Cochrane Database Syst Rev. 2012 Mar 14;3:CD007176

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After an average follow-up time of 11 years, 1,101 deaths were documented (cancer deaths =513 and cardiovascular deaths = 264). After adjustment for potential confounders, neither anyvitamin/mineral supplementation nor multivitamin supplementation at baseline was statisticallysignificantly associated with cancer, cardiovascular, or all-cause mortality. However, baselineusers of antioxidant vitamin supplements had a significantly reduced risk of cancer mortality(HR: 0.52; 95% CI: 0.28, 0.97) and all-cause mortality (HR: 0.58; 95% CI: 0.38, 0.88). Incomparison with never users, baseline non-users who started taking vitamin/mineralsupplements during follow-up had significantly increased risks of cancer mortality (HR: 1.74;95% CI: 1.09, 2.77) and all-cause mortality (HR: 1.58; 95% CI: 1.17, 2.14).

51

In some studies even an increase of the cancer rates was seen • SELECT study: Intake of Vitamin E (400IU, 7 years) leads to an increase

of the incidence of prostate cancer by 17% (Nicastro, Dunn Nutrients.2013; 5:1122-48).

• Finnish smokers study: increase of lung cancer (by 18%, N Engl J Med.1994: 330:1029-35) after intake of ß carotene (8yr, 20 mg ßcarotene/d, 8 yr).

• Similar effects were seen in the CARET study (Omenn et al. J NatlCancer Inst. 1996, 88:1550-9): 30 mg ß carotene/d +25000 IU retinolpalmitate → 28% more lung cancer.

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Why do we fail to find protective effects with dietary antioxidants ???• In the case of ß-carotene it was found that ROS cause cleavage of the

molecule and formation of DNA reactive breakdown products which(may) cause cancer.

• The supply of most individuals with antioxidant vitamin is in MiddleEurope probably sufficient, increase of the intake does not improvethe health condition.

• Maybe, excessive intake of antioxidants causes adverse effects asROS play an important role in the human body, e.g. in the cellularimmune response.

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Is there any possibility to save the “antioxidant theory”?

It is possible that dietary antioxidants are relevant for individuals who are exposed to increased levels of ROS (e.g. via inflammations) or due to obesity and diabetes). Recent findings with pre-diabetic individuals showed that they have increased rates of DNA damage which can be reduced by vitamin C.

54

Lee Wattenberg (Univ. of Minnesota) found in the 1980s that several constituents of dietary compounds (for example thebreakdown products of glucosinolates as well as coffee diterpenoids) protectrodents against induction of cancer by PAHs.He claimed that themain reason for theseprotective effects isinduction of GST.

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“Classical” design of in vitro experiments for the detection of antimutagens

+ +

S9 test compound Antimutagen

MIXLook for a protective effect

Indicator cells

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In the following years, THOUSANDS of studies were published which concerned the prevention of DNA damage or cancer by chemical carcinogens

Animal studies were only rarely performed as they are costly and labor intense.

Most investigations were in vitro experiments in which DNA potectiveproperties of dietary constituents were investigated, the most often used experimental model was the Salmonella/microsome assay.

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For example ca. 700 papers were published which concerned protective effects against HAAs

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The basic assumption behind these experiments was that everymethod which can be used for the detection of mutagens canbe also used for the identification of antimutagens.Unfortunately this concept is WRONG

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In vitro systems reflect the situation in humans only partly (i) they donot reflect the absorption in the GI tract and (ii) they do not reflectthe induction of drug metabolizing enzymes which is a importantmechanism of chemoprerevention of cancer (in general)

The figure shows the situation in experimentswith cells lacking enzymes (to whichexogenous activation mix is added).Promutagens are activated by enzymes (AE)forming ultimate DNA-reactive metabolites,which enter the cells and bind to DNA.Antimutagens (AM) can either inactivate thepromutagens by direct binding (1), byinhibition of the activating enzymes (2), or bydetoxification of the ultimate metabolites (3).The latter process may take place extra- orintracellulary (3). Another important mode ofaction is the induction of repair enzymes (4).

Nersesyan et al. 2009 -Chemoprevention of Cancer and DNA Damage by Dietary Factors, Eds: Knasmüller, DeMarini, Johnson, Gerhäuser; Wiley VCH 60

The figure shows the situation in cellspossessing phase I and phase II enzymes(without activation mixture). Also in thiscase antimutagens can directly inactivatemutagens extra- or intracellularly (1), orinhibit activating enzymes which arelocated in the target cells (2).Furthermore, the DNA-reactivemetabolites may be inactivated in thecells (3). Other mode of the action is theinduction of repair enzymes (4) or theinduction of detoxifying enzymes (DE, 5).This latter process is regulated bytranscription factors.

Nersesyan et al. 2009 - Chemoprevention of Cancer and DNA Damage by Dietary Factors, Eds: Knasmüller, DeMarini, Johnson, Gerhäuser; Wiley-VCH

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Schutzfaktoren

Was schützt den Menschen tatsächlich?

Zwei Beispiele:

Ballaststoffe Phytoöstrogene

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Ballaststoffe

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In the 1970s, Denis Parsons Burkitt, a US physician compared the stool volumes and weights of US Africans and black individuals who lived in Africa, he found pronounced differences and postulated that they are due to consumption of fiber via the dies, in parallel he found also strong difference in regard to the incidence of colon cancer, these observations lead to the “fiber hypothesis”

US African stools low volumelow fibercolon cancer ↑

African stoolshigh volumehigh fibercolon cancer ↓

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What is fiber ?According to a widely used definitionsfibers are compounds which are notabsorbed in the GI tract. Their chemicalstructures are heterogeneous.

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The amounts which are consumed are well known:

• in the US ca 15 g are consumed per person/d.

• in Europe, the daily intake values are higher (ca. 21 gin Middle Europe, up to 26 g in Northern Europeancountries).

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Mechanisms of cancer protection by fibers

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Results of animal studies (Sengupta et. al., 2009)

Most investigations concerned the impact of fibers on formation ofcolon cancer, the most frequently employed model werepreneoplastic foci which were induced by model compounds(AOM, DMH). In the majority of studies protective effects wereseen, but in some investigations (e.g. with bran) even an increaseof the lesions was observed which may be due to the fact that highdoses were fed to the animals which caused damage of the colonmucosa and as a consequence increased proliferation of the cells.

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Results of human studies1) Meta-analysis of 25 prospective studies: additional

consumption of 10g fibers/d leads to reduction of coloncancer risk by ca 10% (most pronounced effects: cereals fromleguminous plants) also consumption of fiber rich full grainproducts was found highly effective (Aune et al., 2011 BMJ.10;343:d6617)

2) EPIC (more than 500 000 participants), in the group with thehighest consumption level (more than 35 g/d) the risk is ca.40% lower as that seen in the group which consumed 15 g/dor less.

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Fibre and coloncancer

Aune et al. Annals of Oncology 23: 1394–1402, 2012 doi:10.1093/annonc/mdr589

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Wholegrain andcoloncancer

Aune et al. Annals of Oncology 23: 1394–1402, 2012 doi:10.1093/annonc/mdr589

Consumption of fibers leads also to a reduction of breast cancer incidence

Aune et al. Annals of Oncology 23: 1394–1402, 2012 doi:10.1093/annonc/mdr589

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Fibre and breast cancer

Phytoöstrogene

Lignane in Getreide Isoflavone in Soja

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Phytoestrogens have an impact on the effects ofsex hormones . The two main groups containedin our diet are lignans (in cereals) and isoflav-ones (in soy)

O

OR1

R2

OR3

OO

OH

OH

OH

OCCH2

O

OH

O

R4

Malonyl AgluconeGlucoside

Acetyl

Compound R1 R2 R3 R4

Daidzein H H H H

Glycitein H OCH3 H H

Genistein OH H H H

Formononetin H H CH3 H

Biochanin A OH H CH3 H

Puerarin H H H Glucose

4'

3'

7

6

8

Mortensen et al. 2009 Isoflavones: Sources, Intake, Fate in the Human Body, and Effects on Cancer. In Chemoprevention of Cancer and DNA Damage by Dietary Factors

74

Isoflavones in soy products

• Meat replacement products (200 mg/100g)

• Soy flours (170 mg/100g)

• Soy milk (8 mg/100g)

• Natto (80 mg/100g)

• Miso (40 mg/100g)

• Tempeh (40 mg/100g)

• Soy sauce (5 mg/100g)

• Tofu (30 mg/100g)

• Soy sprouts (12 mg/100g)

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Modes of action

Modulation of

estrogen

bioavailability

SHBG

E

Modulation of estrogen

biosynthesis

Modulation of estrogen

activation

Modulation of the

estrogenic response

E

E SO4

Mammalian lignans (ML)

aromatase

ETML

ML

E

E

MLML

Rep

ActRepor or

ERE

(promoter)

SHBG

E

SHBG

E

SHBG

E

SHBG

E

sulfatationH3C HO

HO oestradiol

H3C

CH3

O

HO

testosterone

aromatase

76

Phytoestrogens bind to estrogen receptors which act as transcription factors

77

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Cancer protective effects of phytoesterogenes

Impact on cancer risks

• Results of human studies indicatethat consumption of soy productsreduces the breast cancerincidence. These effect were onlyseen in Southeast Asian countrieswith high intake levels. There isalso some evidence for aprotective effect against prostatecancer .

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Schlussfolgerungen I1) Chemische Kanzerogene in Nahrungsmitteln, auf die sich die Forschung in derVergangenheit konzentrierte scheinen das humane Krebsrisiko nicht maßgeblich zubeeinflussen.

2) Dies trifft auch auf Schwermetalle sowie auf Herbizide und Pestizide zu.

3) Biologisch erzeugte Nahrungsmittel sind aus der Sicht der Krebsprävention nichtgesünder als Lebensmittel die mit konservativen Herstellungsverfahren produziert werden.

4) Relevante Risikofaktoren sind Fleischverzehr , Alkoholkonsum und in ganz besonderemAusmaß das Übergewicht.

5) Bestimmte Spurenelemente und Vitamine beeinflussen das Krebsrisiko, einige dieserSubstanzen werden dem Körper offensichtlich nicht in ausreichendem Maß über dieNahrung zugeführt.

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Schlussfolgerungen II

• 6) Die optimalen täglichen Aufnahmemengen dieser „stabilisierenden Faktoren“ sind im Hinblick auf die Vermeidung von Krebserkrankungen nicht bekannt.

• 7) Es sind eine Reihe von Nahrungsinhaltsstoffen bekannt die die Erkrankungshäufigkeit reduzieren ( Phytoöstrogene, Ballaststoffe, bestimmte Karotinoide etc.).

• 8) Das „Image“ antioxidativ wirksamer Vitamine hat sich in den letzten Jahren verschlechtert.

• 9) Die Relevanz von Substanzen, die vor chemischen Kanzerogenen schützen ist unklar, Verbindungen die Transkriptionsfaktoren aktivieren die für „Entgiftungsprozesse“ zuständig sind und oder Entzündungen vermeiden könnten durchaus projektive Eigenschaften haben.

• 10) Wahrscheinlich liegt die Zukunft in einer „individualisierten“ Krebsprophylaxe.

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Danke für Ihre Aufmerksamkeit

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