Chapter 1+2 Notes

• Cancer has aberrant chromosomes
• Tumour growth is based on a particular, incorrect chromosome combination


  Which is the cause of the abnormal growth characteristics passed on to daughter cells
• Cytogenetics


  Study of number and structure of chromosomes
• Cytogenetics


  1. Karyotype (number and appearance) of human chromosomes

  2. Metaphase Banding Staining Giemsa (G) chromosome banding technique

  3. Chromosome mapping

  4. Spectral karyotyping (SKY) – fluorescence painting of chromosomes
• Philadelphia chromosome in CML (chronic myelogenous leukemia)
• Chromosomal imbalances in cancer (gains and losses)
• Translocations = rearrangement of parts between nonhomologous chromosomes
• Inversions = segment of a chromosome is reversed end to end
• Genomic gains and losses in chromosomal imbalances
• Oncogenes promote cancer, Tumour Suppressor genes protect from cancer
• Both Oncogenes and Tumour Suppressor genes are misregulated in cancer
• Discovery of oncogenes by Payton Rous with Rous Sarcoma Virus (RSV) in 1910
• Tumours can be excised from tissue from one animal and forced to grow as a graft in the body of another animal
• RSV filtrate caused sarcoma and is transmissible
• In vitro transformation of normal cells to tumour cells after RSV infection
• Cancer cells lose contact inhibition and continue proliferation
• Contact inhibition


  • Proliferation stops upon cell contact; cancer cells lose contact inhibition and continue proliferation
• Morphology change in cells


  Cells become brighter, spindly, etc.; become elongated and grow as they touch each other
• Formation of monolayer of cells


  Cells form islands across the bottom of the dish, proliferate, fill up the space, resulting in confluent cultures; normal cells stop proliferating, resulting in a one-cell-thick layer called the monolayer
• Soft agar assay


  Cells suspended in an agar gel; layer of agar at the bottom with cells growing on top; cells moving rapidly and needing more glucose
• Tumorigenicity assay


  Ability of transformed cells to form tumors in mice; injections under the skin or organ-specific
• Continued presence of RSV is needed to maintain transformation
• RSV transforms normal fibroblast cells to highly proliferative, anchorage-independent, and tumorigenic cells
• Development of assays for experimental tumorigenesis
• RSV virus is required to initiate and maintain the transformed phenotype of fibroblast cells
• RSV can be passed from a transformed mother cell to its daughter cells
• Re-infection could not explain the stable transmission of RSV genome
• Virus integrates DNA; RSV is a retrovirus
• 1. src gene is required for transformation
• Viral transforming gene is borne by the RSV genome and acts as a potent Oncogen
• RSV is a retrovirus
• src gene is required for transformation
• Viral transforming gene


  • Borne by the RSV genome and acts as a potent Oncogene
  • Capable of transforming a hormell cell into a timer cell
• Detecting src gene in host genome DNA

  Southern blotting
• src gene is present in uninfected cells
• src sequences were found in both RSV infected and uninfected cells
• src gene


  • Normal, highly conserved gene of all vertebrate species
• src sequences were found in other species
• Kidnapping of src


  Suc-negative retrovirus; avian-leukosis virus (ALV)
• Proto-oncogenes


  • Cellular src or c-src is present in normal tissues
  • c-src is not cancer causing
  • c-src has a potential to transform cells under certain circumstances (if activated as in v-src)
  • c-src is a proto-oncogene