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The Hallmarks of Cancer

RELATIVE CONTRIBUTION OF OXIDATIVE STRESS TO HUMAN CANCER: EVIDENCE FROM CANCER EPIDEMIOLOGY Stefan Ambs, Ph.D. Laboratory of Human Carcinogenesis National Cancer Institute. The Hallmarks of Cancer. MECHANISMS LEADING TO OXIDATIVE STRESS.

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The Hallmarks of Cancer

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  1. RELATIVE CONTRIBUTION OF OXIDATIVE STRESS TO HUMAN CANCER: EVIDENCE FROM CANCER EPIDEMIOLOGY Stefan Ambs, Ph.D.Laboratory of Human CarcinogenesisNational Cancer Institute

  2. The Hallmarks of Cancer

  3. MECHANISMS LEADING TO OXIDATIVE STRESS

  4. EXPRESSION OF ANTIOXIDANT AND PROOXIDANT ENZYMES CHANGES IN CANCER Manganese Superoxide Dismutase many cancers candidate tumor suppressor gene Cu/Zn Superoxide Dismutase  Catalase  Glutathione Peroxidase-1  Cyclooxygenase-2, Lipoxygenases  Nitric Oxide Synthase-2  A prooxidant state is common in cancer cells Many cancers poorly metabolize hydrogen peroxide H2O2 concentration is commonly increased in human tumor cells Antioxidant Prooxidant

  5. Different Research Approaches to the Same Question Observational Research, Intervention Trial, Molecular and Cellular Research, Nutrition Research, Animal StudiesOxidative Stress Exposure to reactive oxygen (ROS) and nitrogen (RNS) species Cancer OnsetProgression

  6. Infections & Chronic Inflammation Environmental Occupational Factors Factors Diet Oxidative Stress, which leads to cancer, is influenced by diet, environmental factors, infections, occupational factors. Cancer

  7. PROOXIDANT STATE BY INHERITED PREDISPOSITION. Are there individuals with an inherited pro-oxidant state who have an increased risk of developing an illness like cancer?High risk: Wilson’s disease and hemochromatosis.Low risk: Defense genes such as SOD2(Val16Ala) or NQO1 (Pro187Ser)

  8. MnSOD Val16Ala GENOTYPE MODULATES BREAST CANCER SURVIVAL After 11 years only 50% of the patients with the Ala/Ala MnSOD genotype survive, whereas 60% survive with the Val/Ala genotype and 90% survive with the Val/Val genotype.

  9. CANCER CAUSES WORLDWIDE Cause % of all cancers Nutrition 30-35 Tobacco 15-30 Chronic Infections 10-20 High Penetrance Genes < 10 Any Other Individual Cause < 5 The International Agency for Research on Cancer

  10. WESTERN STYLE DIET INDUCES OXIDATIVE STRESS A diet high in fat and low in calcium & vitamin D induced changes in the colon of mice consistent with pro-oxidant redox changes in colon epithelial cells and a pro-inflammatory response by the organ

  11. NUTRITION AND CANCER Evidence • Migration Studies • Association Studies • Intervention Trials • A high intake of fruits, vegetables, tea, fish oil and selenium is associated with low risk. • A high intake of alcohol, red meat, animal fat, salted fish, charbroiled foods, salt-preserved foods, and contaminated foods is associated with high risk.

  12. COMMON DESIGNS IN EPIDEMIOLOGICAL STUDIES Case Control study Recruits cases and controls at the same time Previous exposures (e.g., diet) are assessed with questionnaire Investigates the frequency of exposure among cases and controls (retrospective assessment of exposure) Prospective study Disease-free participants with known exposure are followed-up to assess the relationship between disease development and exposure

  13. TOMATO-BASED PRODUCTS AN CANCER RISK. Raw tomatoes decreased the relative risk of getting prostate cancer to 0.89 whereas cooked products decreased the relative risk to 0.81.

  14. FDA’S EVIDENCE-BASED REVIEW OF HEALTH CLAIMS FOR TOMATOES AND LYCOPENE Review to make “Qualified Health Claims” requested by Lycopene Health Claim Coalition (Heinz Company, LycoRed Natural Products Industries, The Prostate Cancer Foundation) and American Longevity, Inc. FDA found very limited evidence to support an association between tomato consumption and reduced risks of prostate, ovarian, gastric, and pancreatic cancers Preliminary scientific research suggests eating one-half to one cup of tomatoes and tomato sauce a week may reduce the risk of prostate cancer No credible evidence for lung, colorectal, breast, cervical, or endometrial cancer

  15. MORE RECENT RESULTS FROM OBSERVATIONAL STUDIES • Vitamin A, C, E, and folate, and lung cancer risk: Pooled analysis of 8 prospective studies (Int J Cancer 2006) • Data do not support the hypothesis that intakes of these vitamins and folate reduce lung cancer risk • Fruit, vegetables and prostate cancer risk: Results from the multiethnic cohort study (Cancer Causes Control 2006) • No significant associations; intake of tomato products is associated with a modest increase of risk (ptrend is .0001) • Regular multivitamin use and prostate cancer (JNCI 2007) • No association with localized cancer; increased risk of advanced disease (excessive use) • Dietary fibers and colorectal cancer risk: Pooled analysis of 13 prospective studies (JAMA 2005) • Data do not support the hypothesis that high fiber intake reduces colorectal cancer risk

  16. AGE-ADJUSTED PREVALENCE OF OBESITY FOR ADULTS IN THE UNITED STATES, 1960-2000 In 1960 11% of the men and 15% of the women were obese. In 1970 12% of the men and 16% of the women were obese. In 1980 13% of the men and 17% of the women were obese In 1990 21% of the men and 27% of the women were obese In 2000 29% of the men and 34% of the women were obese

  17. OVERWEIGHT AND OBESITY MAY ACCOUNT FOR 10% to 20% OF CANCER DEATHS IN THE US • Women RR§ • Multiple Myeloma 1.44 • Colorectal 1.46 • Ovarian 1.51 • Liver 1.68 • All Cancers 1.88 • Non-Hodgkin’s 1.95 • lymphoma • Breast 2.12 • Gall Bladder 2.13 • Esophagus 2.64 • Pancreas 2.76 • Cervix 3.20 • Kidney 4.75 • Uterus 6.25 Men RR • Prostate 1.34 • Non-Hodgkin’s 1.49 lymphoma • All Cancers 1.52 • Kidney 1.70 • Multiple Myeloma 1.71 • Gall Bladder 1.76 • Colorectal 1.84 • Esophagus 1.91 • Stomach 1.94 • Pancreas 2.61 • Liver 4.52

  18. INCREASED MORTALITY WITH HIGH BODY MASS INDEX

  19. EVIDENCE FOR ROS & RNS IN CANCER ETIOLOGY • Lung • Liver • Stomach • Bladder • Colorectal • Esophageal • Prostate • Leukemia • Skin • Kidney

  20. NON-STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) AND COLON CANCER RISK Summary of Prospective Studies

  21. ASPIRIN REDUCES RISK OF CANCER DEATHS

  22. CANCER CAUSES Cause % of all cancers Nutrition 30-35 Tobacco 15-30 Chronic Infections 10-20 High Penetrance Genes < 10 Any Other Individual Cause < 5

  23. ROS & RNS IN LUNG CANCER ETIOLOGY • Tobacco Smoke • Increases urinary 8-oxodG excretion by 30%-50% • Contains ROS and ROS-generating compounds • Induces monocyte recruitment and activation (ROS & RNS ) • Induces CYP450 and ROS as a byproduct of CYP450 metabolism • Asbestos/Silicosis  5,000 - 10,000 cases per year in the US • Persistent inflammation • Generation of radicals at particle surface and by particle-activated cells • Radon 15,000 cases per year in the US • Decays by alpha particle emission (H20  HO• + H•) • Asthma and Chronic Bronchitis • Asthma: OR 1.8 (95% CI 1.3 - 2.6) • Bronchitis: OR 1.7 (95% CI 1.1 - 2.7) independent of smoking

  24. LUNG CANCER PREVENTION TRIALS • Alpha-tocopherol Beta-carotene Trial (ATBC, Finland) • Carotenoid and Retinol Efficacy Trial (CARET, US) • Physicians’ Health Study (PHS, US) • Women’s Health Study (WHS, US)

  25. PREVENTION TRIAL RESULTS

  26. CONCLUSION FROM TRIALS • Pharmaceutical doses of antioxidants that apparently are nontoxic bioactive compounds in the general population may have adverse effects in individuals with high-risk behavior such as high smoking and alcohol intake

  27. CANCER CAUSES Cause % of all cancers Nutrition 30-35 Tobacco 15-30 Chronic Infections 10-20 High Penetrance Genes < 10 Any Other Individual Cause < 5

  28. INFECTIOUS AGENTS AND CANCER • Viruses cause about 10%-15% of all cancers worldwide • Bacteria about 5% • Parasites less than 1% IARC Data

  29. INFECTIONS ASSOCIATED WITH HUMAN CANCER Virus • Hepatitis B & C Virus cause liver cancer • Human Papilloma Virus causes cervical cancer • Epstein-Barr Virus causes Burkitt’s lymphoma • Human T-Cell Lymphotropic Virus causes Adult T-cell leukemia • HIV & HHV-8 cause Kaposi’s sarcoma • Helicobacter pylori causes gastric cancer • Schistosomes cause bladder cancer • Liver fluke causes cholangiosarcomas

  30. CANCER CAUSES Cause % of all cancers Nutrition 30-35 Tobacco 15-30 Chronic Infections 10-20 High Penetrance Genes < 10 Any Other Individual Cause < 5

  31. SKIN CANCER Skin Cancer Cases in the US (2002) • Basal Cell Carcinoma 900,000 • Squamous Cell Carcinoma 300,000 • Melanoma 54,000 • Major Cause: Sunlight • UVB radiation (290 - 320 nm) leads to DNA photoadducts • CC  TT transitions is the molecular signature of sunlight exposure • UVA radiation (320 - 400 nm) leads to oxidation reactions • Cellular photosensitizers generate 1O2 and O2 • UVA photons penetrate deeper into the epidermis layer than the • higher-energetic UVB radiation • –

  32. OXIDATIVE STRESS AND SKIN CANCER • UV radiation reduces activity of SOD and catalase • Tumor promoters in skin carcinogenesis • Active agents down-regulate SOD and catalase • Phorbol esters that do not stimulate superoxide production are inactive in tumor promotion

  33. Oxidative stress and cancer progression. ●Glucose deprivation, metabolic alterations, growth factor signaling, monocyte infiltration and exposure to heavy metals leads to oxidative stress. ● Poor blood supply and high energy use lead to hypoxia. ●Oxidative stress and hypoxia lead to genomic instaiblity, cell mobility, exgtracellular matrix and angiogenesis.

  34. NF-κB IN CANCER PROGRESSION • NF-κB pathway activation is frequently observed in metastatic human tumors • NF-κB knockout inhibits metastasis in a murine models of lung, liver and prostate cancer • Activators of NF-kB pathway • Environmental hazards (metals, smoking) • Infections • Physiological stress • Inflammation

  35. SUMMARY ●There is strong evidence that oxidative stress is involved in human cancer causation and promotes disease progression●Cancer epidemiology has not succeeded in linking specific antioxidants to a reduced cancer burden●Knowledge of tumor redox biology promises better prevention strategies and new treatment options

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