Phytochemcials in Cancer Prevention

1. Phytochemcials in Cancer Prevention Michael J. Wargovich, Ph.D.

2. What Is Chemoprevention? • The science of trying to apply natural and synthetic compounds to interfere with the earliest stages of carcinogenesis, before invasive cancer appears

5. The Ideal Chemopreventive Agent • Is effective • Easily administered • Preferably once/twice day • Little or ideally no toxicity • Affordable

6. Mechanisms of Chemoprevention • Antioxidants: defense against radicals • Phase 1 enzyme inducers • Phase 2 enzyme inducers • Anti-proliferative agents • Anti-hormonal compounds • Disruption of mutational gain or loss of function • Epigenetic effects

7. Antioxidants • Oxygen is actually a very toxic substance • Antioxidants are the first line defense mechanism against oxidative damage in plants • Fruits and vegetables are loaded with antioxidant chemicals

8. Total Daily Intake of Antioxidants

10. Flavanone Flavonol Flavanol e.g. e.g. hesperetin quercetin e.g. epicatechin onion, cranberry, red apple Citrus fruit, orange red wine, green tea, many fruit and vegetables as procyanidins in apple, chocolate OH OH HO O OH OH Hydroxycinnamate e.g. caffeic acid most fruit especially tomato, apple some vegetables e.g. egg plant grains COOH OH OH OH OH HO O OH OH O Anthocyanidin e.g. cyanidin major constituents of dark red fruit berries e.g. raspberries OH OH OH OH + HO HO O O OH OH OH

11. Green Tea • Epidemiologic studies support a protective effect for green tea but not black tea in prevention of certain cancers • Animal studies are highly supportive of a preventive effect of green tea, GTP, and purified polyphenols, especially EGCG against certain cancers Camellia sinensis

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13. Evidence for Tea Drinking and Prevention of Human Cancer • Ecological Studies • Cohort Studies • Case-Control Studies

15. Bioflavonoids • Naturally occurring chemicals present in many fruits and vegetables • Major flavonoids in onion are quercetin and its glycoside, rutin • Can reach appreciable levels in onions but tea also is a major source

16. Bioflavonoids and Reduced Risk for Heart Disease • Quercetin inhibits oxidation of LDL cholesterol • Inhibits development of fatty streaks in animals

17. Agents That Influence Drug Metabolism

18. Surh et al Nat Reviews 3:2003

19. Garlic • Consumption in China and Italy linked to lower gastric cancer risk • Sulfur compounds inhibit cancers of colon, breast, esophagus, lung, skin • Primarily acts through modulation of Phase 1 ( activation) and Phase 2 (detoxification) enzymes Allium sativum

20. Organosulfur Compounds in Garlic Alliin • Member of the plant genus Allium • Over 20 different compounds in garlic are being tested for cancer inhibition. • Diallyl sulfide was the first organosulfur compound known to inhibit experimentally-induced cancer. • Proposed mechanisms of chemoprotection lie in modification of carcinogen metabolism and/or detoxification. Allinase Allicin Lipophilic compounds diallyl sulfide diallyl disulfide methyl propyl sulfide dipropyl disulfide dimethyl trisulfide methyl propyl trisulfide methyl propyl thiosulfinate Water soluble compounds L-cysteine S-allyl-l-cysteine S-methyl-l-cysteine L-methionine

21. CYP2E1 and Colon Cancer Dimethylhydrazine (DMH) Model CH3-NH-NH-CH3 1,2-Dimethylhydrazine LIVER COLON CH3-N=N-CH3 azomethane CYP2E1 Spontaneous breakdown H3C + N2 CH3-N N CH3-N=N-CH3 methyldiazonium O azoxymethane CYP2E1 CH3-N=N-CH2OH methylazoxymethanol

22. Cyp2e1 • One subset of many cytochromes P450 • Main task is to activate compounds; eliminate them from the body • This enzymes metabolizes many small molecular weight compounds • Ethanol, nitrosamines, hydrazines

23. Typical Chemoprevention Assays in Rodents

25. Chemopreventive activity of oil-soluble OSCs in ACF assay(M. Wargovich, 1997)

26. Antiproliferative or Growth Suppressing Agents:Modulation of Cell Signaling

27. COX Inhibitors Reduce Colorectal Carcinogenesis – Observational Data

28. How Do NSAIDs Work? • Aspirin transfers acetyl group to serine on the cyclooxygenase enzyme, blocking its affinity for arachidonic acid • All other NSAIDs are competitive inhibitors of the COX enzymes

29. BIOLOGICAL ROLE OF PROSTANOIDS

30. Inflammation and Cancer • Chronic, clinically invisible, unresolved inflammation may create a very high risk for common cancers • Tumors corrupt the inflammatory pathway to survive

31. A model of chronic inflammationsetting a threshold for cancer Chronic Inflammation Esophagitis Gastritis Colitis Pancreatitis Hepatitis Initiation Tumor Mutation ROS/RNS Growth advantage ROS/RNS Replacement hyperproliferation Cell damage Promotion  apoptosis  angiogenesis

32. Loss of 18q APC mutation K-ras mutation p53 mutation COX-2 Overexpression Multistage Colon Carcinogenesis

33. NSAIDs Inhibit ACFs in the Colon

34. NSAIDS, COX Specificity and Chemoprevention COX 1COX 2 100% Indomethacin 0% Sulindac Piroxicam Diclofenac Naproxen Meclofenamate Etodolac Nimsulide Celecoxib 0% 100%

35. Toxicity of NSAIDs • Ibuprofen • Diclofenac • Naproxen • Ketoprofen • Indomethacin • Piroxicam • - + • +/- + • +/- + • + ++ • +++ +++ • +++ +++ Compound Toxicity* Inhibit ACF? * Clinical manifestations: Colitis, perforation, fistulae, GI bleeding Peptic and small bowel ulcers, strictures

36. 35 35 Late treatment (days 55-80) Early treatment (days 30-80) 30 30 25 25 20 20 * Multiplicity (tumors/animal) 15 15 * * * 10 10 5 5 0 0 Vehicle 1500 50 Vehicle 150 500 1500 50 500 Piroxicam Celecoxib Celecoxib Piroxicam (mg/kg diet) (mg/kg diet) Celecoxib Inhibits Tumor Multiplicity in the MIN Mouse Model * P < 0.05; n=12/group Jacoby et al: Cancer Res 60:5040-4, 2000

37. Effect of COX-2 Selective Inhibition on Colorectal Adenomas in Patients with FAP Steinbach et al, NEJM, 2000

41. Plant-based NSAIDS...

43. Herbal NSAIDS • Overuse could potentially result in bleeding, prolonged platelet aggregation, and ulceration • Combined use might reduce the need for high strength NSAIDs • Could help in long term chemoprevention trials for colon and breast cancer

44. Are there plant-based NSAIDS? • If so, the source should: • Have anti-inflammatory effects • Be available for oral use • Be safe • Efficacious

45. Resveratrol (Red Grapes) • A phytoalexin in red grapes • Inhibits cell transformation in cultured tumor cells • Inhibits cell proliferation in cells in culture and in tumors grown in mice • Inhibits mammary cancer in rats • Induces apoptosis

46. Epidemiological Studies of Tea and Cancer • Ecologic, case-control and cohort studies have been performed. • Studies are difficult to compare. No standard method of tea intake • Several cancer sites investigated: • Stomach, colon, esophagus, prostate, lung • Duration of tea consumption is important • Earlier in life, stronger the effect

47. Results of Animal Studies With Tea Yang CS. Personal Communication

49. How Do Tea Polyhenols Prevent Colon Cancer? • By inhibiting cell proliferation and inducing apoptosis? • Yes. • By influence on cell signaling pathways? • Yes. • By influence on nuclear transcription factors? • Yes. • By inhibition of prostanoid biosynthesis? • Yes. • By epigenetic mechanisms? • Our current research

50. Anti-proliferation effects of EGCG EGCG µM EGCG µM 48 hr 72 hr