Chemical-induced carcinogenesis

• Neoplasm (Tumor)

  • lesion resulting from abnormal and uncontrolled cell growth (neoplasia)
  • characterized by swelling or increase in size
  • Benign: Benign neoplasms may grow large; do not spread into, or invade, nearby tissues or other parts of the body
  • Malignant (Cancer): Malignant neoplasms can spread into, or invade, nearby tissues or other parts of the body through the blood and lymph systems.
• • Hyperplasia: an increase in the number of cells in a tissue that appear normal under a microscope
  • Dysplasia: the cells look abnormal under a microscope but are not cancer
  • Hyperplasia and dysplasia may or may not become cancer
• Characteristics of cancer

  1. Self-sufficiency in growth signals: has their own signals; normally receive signals then divide
  2. Insensitivity to anti-growth signal
  3. Evade apoptosis
  4. Replicative immortality (X die)
• Characteristics of cancer

  1. Sustained angiogenesis: grow new blood vessels (gain nutrients + spread to other places)
  2. Tissue invasion and metastasis (spread)
  3. Reprogramming of energy metabolism
  4. Evading immune destruction
• Chemical carcinogens

  • agents that increase likelihood of cancer formation
  • change the rate/ frequency of cancer formation on exposure
• Genotoxic carcinogen

  • Mutagenic (add on DNA)
  • Tumorigenicity: Dose responsive (increase exposure = increase rate)
  • no theoretical threshold (no definitive dose where cancer develops)
  • 3 subtypes: complete carcinogens, procarcinogens, co-carcinogens
• Non-genotoxic (Epigenetic) carcinogen

  • Non mutagenic
  • Dose response
  • Threshold + Reversible
  • Species, Strains, Tissue specificity (only respond if target receptor/ tissue exist) e.g. Breast cancer