Gene mutations: Development of cancer

• Inherited
  • About 5% to 10% of all cancers or predisposition to cancers are inherited
  • Lead to a very high risk for cancer
• Acquired
  • Most cancers are acquired
    • Chemical
      • Many chemicals have been identified as carcinogens over the years
        • Benzene
        • Arsenic
        • Formaldehyde
    • Radiation
      • Radiation can cause cancer in almost any human tissue
      • Damage occurs to DNA
      • Ultraviolet radiation is associated with melanoma and squamous and basal cell carcinoma
        • Sunlight is main source of UV exposure
    • Viral

• Promotion
  • Characterized by reversible proliferation of altered cells
  • Activities of promotion are reversible
    • Obesity
    • Smoking, alcohol
    • Dietary fat
• Latent period
  • May range from 1 to 40 years
  • Length of latent period associated with mitotic rate of tissue of origin and environmental factors
  • For disease to be clinically evident, tumor must reach a critical mass that can be detected
• Progression
  • Characterized by
    • Increased growth rate of tumor
    • Invasiveness
    • Metastasis (spread of the cancer to a distant site)
      • The most frequent sites of metastasis are lungs, liver, bone, brain and cerebrospinal, and adrenal gland
      • The pathogenesis of cancer metastasis.
        • To produce metastases, Tumor Cells must detach from the primary tumor and enter the circulation, survive in the circulation to rest in the capillary bed, adhere to capillary basement membrane, gain entrance into the organ parenchyma, respond to growth factors, proliferate and induce angiogenesis, and evade host defenses.
      • Detached cells can invade lymph nodes and vascular vessels to travel to distant sites
      • Most mobile tumor cells do not survive
      • Surviving tumor cells must create an environment conducive to growth and development

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