greek.doctor

14. Chemoprevention

  • Chemoprevention refers to the use of natural compounds to try to reduce the risk of or delay the development or recurrence of cancer
  • However, some chemopreventative agents turned out to be carcinogenic
    • Vitamin E supplements actually increase the risk for prostate cancer
    • Beta-carotene supplement increases the risk of lung cancer in smokers
  • Recent research has determined several potentially chemopreventative natural compounds
  • See also topic 2

Potentially chemopreventative natural compounds

  • Most of these have proven effect in vitro but not in vivo
  • Many of these are phytochemicals, chemical compounds of plant origin that are not nutrients, but which have other health effects
  • Most phytochemicals are found in the peel or outer parts of the fruit/vegetable
  • Many of the pigments found in fruits and vegetables are phytochemicals
    • Ensure that you consume fruits and vegetables of different colours
  • Types
    • Carotenoids
      • β-carotene
        • Found in carrots
      • Lutein
        • Found in spinach
      • Lycopene
        • Found in tomatoes
    • Glucosinolates
      • Found in brussel sprouts, broccoli, etc.
    • Flavonoids
    • Alkaloids
    • Resveratrol
      • Found in red wine, grapes, blueberries
    • Curcumin
    • Green tea
    • Black tea
  • Possible modes of action
    • Antioxidant effect
      • Inhibits reactive oxygen species (ROS)
    • Inhibit phase I biotransformation enzymes
    • Activate phase II biotransformation enzymes
    • Anti-inflammatory effect
      • Upregulation of NF-κB and COX-2 is common in many cancers
      • In vitro studies have shown that phytochemicals inhibit the expression of these pro-inflammatory proteins
    • Activation of MAPK
      • MAP kinase is involved in differentiation and apoptosis
    • Induction of apoptosis
    • Anti-angiogenesis
      • Phytochemicals can reduce VEGF and VEGF receptor expression
    • Regulation of intracellular signalling pathways
      • Phytochemicals can inhibit the Akt pathway
    • Inhibit tumour invasion
      • Tumours use MMPs to invade through basement membranes
      • Phytochemicals can reduce the expression of MMP and increase expression of MMP inhibitors