Cancer Biology

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Cancer Biology
2011-04-19 15:20:50
Cancer Biology

The biology of Cancer
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  1. What is cancer?
    • Unrestrained division of cells
    • -failure of the cell cycle
    • -normal cells respond to signals that dictate whether to divide
    • *cancer cells become autonomous from such signals
  2. Neoplasia
    Abnormal cell growth

    Benign- slow growth, non-invasive, no metastasis (spread)

    Malignant- rapid growth, invasive, potential metastasis

    Benign tumors can become malignant
  3. Malignant vs. Benign
  4. How do cancer cells gain this autonomy?
    Normal cells become cancerous through mutations to a cell's genome

    • Generally from an accumulation of mutations
    • -produce proteins that disrupt cell cycle
    • -why cancer mostly affects midle-aged to elderly
    • -mutations usually somatic (not heritable)
  5. Two requirements for cells to become cancerous
    • Mutation affecting genes that induce cell division
    • Mutation affecting genes that suppress cell division

    "their accelerators must get stuck and their breaks must fail"
  6. Target Genes
    • Oncogenes
    • -Normally induce cell division
    • -When mutated, can cause cancer by being stuck "on"
    • example: RAS

    • Tumor Suppressor Genes
    • -Normally suppress cell division
    • -when mutated, can cause cancer by being stuck "off"
    • example: p53
  7. Oncogenes
  8. Tumor Supressor Genes
  9. The Six Halmarks of Cancer
    • Immortality
    • -Continuous cell division & limitless replication

    • Produce "Go" Signals
    • -Growth factors & oncogenes

    • Override "stop" signals
    • -Anti-growth signals from tumor suppressor genes

    • Resist Cell Death
    • -Apoptosis

    • Angiogensis
    • -New blood vessel growth into cell

    • Metastasis
    • -Spread to other sites

  10. What is tumor angiogenesis?
  11. Metastasis
  12. Successive Rounds of Mutation
    • Cancer is a multi-gene, multi-step disease
    • -from an orignal abnormal cell (clonal origin)
    • -Accumulation of mutations result in progression from a mildly unusual cell to a tumor
    • -tumor cells can further mutate and become malignant
    • -Death from cancer generally from spread/invasion of malignant cells into normal tissue.
  13. What can cause these mutations?
    • Viruses
    • -ex: HPV & Cervical cancer

    • Bacteria
    • -ex: H. pylori & stomach cancer

    • Chemicals
    • -ex: B[a]P (in coal tar) & lung cancer

    • UV & Ionizing Radiation
    • -ex: Skin cancer

    these agents are all considered mutagens
  14. Mutagens
    • Can change an organism's DNA
    • -exposure therefore increases mutation frequency

    • Viruses: insertional mutation
    • Chemicals: Bind to DNA
    • Radiation: Breaks DNA strands

    Carcinogen: directly involved in causing cancer
  15. Genes, Lifestyle, & Environment
    Cancer is a complex disease: no single cause

    • Lots of risk factors:
    • tobacco use
    • alcohol consumption
    • age
    • genetic makeup & family history
    • diet & physical activity
    • exposure to infectious agents
    • exposure to pollutants/toxins
  16. Cancer Therapies
    • Cancer is a systemic (whole body) disease
    • -50% of patients experience metastasis

    • Systemic therapy: distributed throughout body
    • -normal and cancerous tissues
    • EX: drug therapy (chemo)

    • Local therapy: directed toward certain area
    • EX: radiation, surgery

    • ideal treatment
    • -effective
    • -tumor-specific
    • -minimal toxicity
  17. Chemotherapy (Cytotoxics)
    • Use of chemicals to kill rapidly dividing cells
    • -like cancer cells
    • but also can affect normal tissue
    • -bone marrow, digestive tract, hair follicles
  18. Chemotherapy
    • Administration of chemotherapy
    • -injected into veins, muscle, or tumor
    • -or taken in pill form

    • Toxicity effects
    • -range from acute to long-term (chronic)
    • *Nausea & vomiting
    • *alopecia (hair loss)
    • *Neurotoxicity
    • *renal, cardiac, pulmonary, etc. toxicity
    • *sterility

    Some find chemo controversial due to the permanent damage it can cause
  19. Chemotherapy Efficacy
    • Some cancers respond better than others
    • -Testicular: 70-90% cure rate
    • -Significantly prolongs patient life in others: leukemia in children, ovarian, colon
    • -Depends heavily on how early cancer is detected.
  20. Targeted Therapies
    Often in conjunction with chemotherapy

    Several focus on molecular/genetic changes in cancer cells & tries to target them

    • -Protein products specific to cancer cells
    • -Cell components important to maintaining malignancy
  21. Types of Targeted Therapies
    • Radiation: ionizing radiation waves aimed at tumor
    • -Cancer cells more sensitive to single-strand breaks in DNA

    • Hormonal therapies for cancers of areas highly regulated by hormones
    • -ex: breast & prostate cancers
    • -to decrease cell growth & induce apoptosis
  22. Reducing Your Risk
    • Non-modifiable risk factors exist, but you can reduce your risk of cancer (or prolong getting it)
    • -avoid tabacco use
    • -avoid or limit alcohol consumption
    • -protect yourself from the sun
    • -avoid behaviors that will put you at risk of contraciting certain viruses/bacteria
    • -consult doctors about any hormonal supplements
    • -know your family history & get yourself examined often
    • -maintain good physical health