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HBIO2 > Cancer
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  • Carcinogens (agents that can cause cancer)
    • Such as smoke, radiation
    • Cause mutations in the genes which control cell division (oncogenes)
    • Divide uncontrollably to produce a mass of cells - tumour
  • Tumour cells do not respond to signals from nerves and hormones
    • Continue to grow
    • No programmed cell death occurs
  • Types
    • Benign - does not spread from its origin (this is not cancer!)
    • Malignant - this is cancer
      • Spread throughout the body invading other tissues and destroying them
      • Cells can break off from the primary malignant tumour
      • They can travel/spread via the lymph system
      • Cause secondary tumours at other places (metastasis)
      • Hard to find and difficult to remove (all of) them
  • Cancer may take many years to develop with few or no symptoms
    • Usually advanced when discovered
    • Cancer in the lungs
      • Can cause coughing up blood (haemoptysis)
      • Can block airways causing lung infections (pneumonia)
      • Removing all/part of the lung may be effective provided metastasis is not well advanced

Smoking and Cancer

  • Smokers 18x more likely to develop lung cancer than non-smokers
  • Causes one third of all deaths from cancer
  • Increased risk
    • Starting at young age
    • Smoking high amount of cigarettes per day
    • High tar content of cigarettes
    • Long time of smoking
  • Decreased risk
    • Stopped smoking
  • Toxins also enter the blood and are excreted via the urine
    • Bladder cancer

Genes and Cancer

  • Evidence
    • Tendency to develop cancer seems to be inherited
    • Tumour cells in some cancers have abnormal chromosomes
    • There is a positive correlation between mutations and carcinogens
  • Oncogenes
    • Genes that turn cells into cancer (oncology = study of cancer)
    • Found when proto-oncogenes (normal versions of genes) mutate and become overactive
  • RAS oncogenes
    • G-proteins are found on plasma membranes and enable cells to respond to growth factors
    • They are normally activated by enzymes found within the cell (GTPase)
    • Mutation of the RAS gene causes the production of GTPase deficient G-proteins
    • The mutated G-proteins remain active for longer causing tumours
  • Myc oncogenes
    • Myc gene produces a protein needed for normal cell division
    • Common mutation switches the myc proto-oncogene from chromosome 8 to 14
    • There, it acts as an oncogene / abnormal cell division / tumour
    • When both ras and myc oncogenes present together, malignant cells result
  • Tumour suppressor genes
    • Reduce normal activity by inhibiting cell division
    • Initiate cell death (apoptosis) if the cell’s DNA is damaged (due to mutations)
    • Mutation of this gene can cause a loss of its function
    • This will result in tumours