Lecture 22

• Cancer


  A group of diseases that involves unregulated cell growth and spread of cells of origin to other parts of the body
• It is difficult to know whether cancer will ever be cured
• Benign tumor


  • Cells divide rapidly but do not spread to other tissues (not cancer)
• Malignant tumor


  • Cells divide rapidly and spread to other tissues (cancer)
• Transformation


  A process by which normal cells acquire properties of cancer cells
• Transformation


  • Normal cells divide and die when specific signals are present
  • Cancer cells constantly divide and never die by ignoring the surrounding signals
• Hallmarks of cancer


  • Growth signal autonomy
  • Evasion of cell death
  • Metastasis and invasion
• Growth signal autonomy


  Cells can grow without growth factors
• Evasion of cell death

  Shuts down apoptosis
• Metastasis and invasion


  Spread and break through barriers
• Cancer is typically observed in older people because cancer mutations take years to happen
• Point mutation


  One type of DNA mutation where one base is changed in the DNA sequence
• Types of point mutations

  • Missense: alter a single amino acid
  • Nonsense: premature stop signals
• Chromosome mutation


  Pieces of chromosome are copied, deleted, or moved to change DNA sequence
• Germline mutation


  Inherited from sperm or egg at fertilization, every cell in the body has the mutation, half of the gametes have the mutation, can explain why some cancers are heritable
• Somatic mutation


  Arise in somatic cell after fertilization, occur after birth, are not passed down, can be spontaneous or induced by environment
• Proto-oncogene


  Normal gene that can change into oncogene
• Oncogene


  Mutated gene that can cause normal gene to become cancerous, when active expresses excessive cell growth and division
• RSV was the first known oncogenic virus, causing tumors in chickens
• Researchers identified the gene responsible for RSV's oncogenic properties as src
• ALV and RSV


  Both retroviruses that can cause cancer in chickens, but ALV doesn't contain the src gene
• 1. c- src

  The normal cellular counterpart of the src gene found in healthy cells, a non receptor tyrosine kinase that phosphorylates proteins, regulated by phosphorylation, activated by EGF/EGFR signaling
• Gain-of-function mutations


  Increase activity of a protein, can produce hyperactive proteins, increase gene expression, or create fusion proteins
• Gain-of-function mutations are associated with transformation