Biology of Cancer

Two major dysfunctions in the process of cancer development:
- Defective cell proliferation (growth)
  - Stem cells
    - Undifferentiated cells
    - Ultimately differentiate and become mature, functioning cells of only that tissue
  - All cells are controlled by an intracellular mechanism that determines proliferation
    - Orderly process progressing from a state of immaturity to a state of maturity
    - Stable and will not change
  - Cancer cells grown in culture are characterized by loss of contact inhibition
    - Grow on top of one another and on top of or between normal cells
  - Cancer cells respond differently than normal cells to intracellular signals regulating equilibrium
    - Divide indiscriminately and continuously
      - Pyramid effect
- Defective cell differentiation
  - Two types of genes that can be affected by mutation are
    - Protooncogenes
      - Regulate normal cellular processes such as promoting growth
      - Genetic locks that keep cells functioning normally
      - Mutations that alter their expression can activate them to function as oncogenes
    - Tumor suppressor genes
      - Suppress growth
      - Function to regulate cell growth
        
        Prevent cells from going through the cell cycle
      - Mutations make them inactive
        
        Result in loss of suppression of tumor growth

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