Biological process

• Contact inihibition: normal cell do not invade the territory of the cells surrounding them or not their own. Cancer cells lose this inhibition and will grow uncontrollably = forming tumors
• The rate at which cells multiply varies in different tissues

  • rapid: bone marrow, hair follicles, GI
  • slow: myocardium, neuronsm cartilage
• Stem cell proliferation

  • controlled by intracellular mechanism
  • natural process of growth and division
  • balance between making new cells and losing old ones
• Cancer cell proliferation

  • different response to intracellular signals
  • equilibrium is dysregulated and haphazard
  • multiply rapidly and continuously forming tumors that grow larger over time
• A change of DNA leads to mutation of the stem cell. # processes can follow

  • cell death: apoptosis or result of damage
  • recognize damage (DNA): repair itself
  • survive: pass along the damage, can become malignant
• Cellular differentiation: cell progresses from a state of immaturity to a state of maturity. Each cell has its specific function
• Neoplasm: abnormal growth of new tissue. It can be malignant (cancerous) or benign
• Benign neoplasm:

  • well differentiated
  • usually encapsulated
  • expansive mode of growth
  • similar characteristics to parent cell
  • metastasis is absent + rarely reoccurs
• Malignant neoplasm

  • undifferentiated, rarely uncapsulated
  • able to metastasize
  • infiltrative and expansive growth
  • frequent recurrence
  • moderate to marked vascularity
  • becomes less like parent cell
• Stages of development of cancer

  1. initiation: mutation of the cell genetic structure due to error that occured during DNA replication
  2. promotion: alteration in genetic structure, reversible proliferation of altered cells
  3. progression: increase growth rate of tumor, spread to cancer (metastasis)
• 1-Initiation: carcinogens can alter DNA and will replicate the same genetic alteration before cell division

  • carcinogens: chemicals, radiation, virus and bacteria, genetic susceptibility
  • effect of carcinogens are usually irreversible and additive during this stage
• 2-Promotion: Increased proliferation of altered cells increases mutagenesis (DNA mutation). The activity of promoters are irreversible but reduction of them can prevent cancer development
• Promoters of mutagenesis

  • dietary fat
  • obesity
  • cigarette
  • alcohol
• Promotion ranges from 1 to 40 years. The time is takes for cancer to become detectable is based on the mitotic (division) rate in tissue where cancer originates and environmental influence
• For the disease to be clinically evident, the tumor must reach a critical mass that can be detected
• 3-Progression: characterized by increases growth rate of tumor, invasiveness and metastasis
• A well established tumor is when certain alterations took place enabling the tumor to survive and thrive in its primary environment and the process of metastasis (secondary environment)
• Frequent sites of metastasis

  • lungs
  • brain
  • bones
  • liver
  • adrenal glands
• The immune system response is to reject or destroy abnormal cells. Cancer cells may be destroyed when perceived as abnormal cells or may not be detected as cancer cells because they arise from normal human cells
• Immunological surveillance prevents transformed cells from developing into clinically detectable tumours by detecting antigens and destroying abnormal cells
• Immunological escape: mechanism by which cancer cells can escape immunological surveillance