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Issues in Risk Assessment (1993) / Chapter Skim
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BIOLOGICAL FACTORS IN TWO-STAGE MODELS
Pages 223-225

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From page 223...
... Two-stage models are based on the assumptions that carcinogenesis is a multistage process, and that in its simplest form, two critical events are sufficient to convert normal cells to cancer cells (e.g., retinoblastoma in children)
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From page 224...
... Somatic mutations depend on the mutation rate per cell division and the number of cell divisions per unit time; retinoblastomas do not develop in adults because the retinal cells have differentiated and no longer divide. In embryonal tissues such as retina, there is no conditional cell division; a mutation results in a clone of cells carrying the mutation.
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From page 225...
... He suggested that the one-hit model may be more appropriate for cancers that arise from exposure to ionizing radiation, potent alkylating agents, or in transgenic mice developing lung cancer, for example, but he admitted that the multiclonal nature of the response indicated that a second event would have to be postulated. The mouse skin tumor model is a well known example of two-stage tumors induced by xenobiotics.
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Key Terms

  • liver tumors
  • lung tumors
  • suppressor genes
  • cell division
  • cell lung

  • embryonal tissues
  • gene carriers
  • skin tumor
  • hereditary cancers
  • tumor types

  • mutations depend
  • nonhereditary form
  • furan produces
  • maronpot suggests
  • print version

  • involved goes
  • mice developing
  • mice exposed
  • cram obtains
  • assessment methodology

  • cell proliferative
  • conditional cell
  • human tumors
  • unleaded gas
  • stem cells

  • develop osteosarcoma
  • discussion dealt
  • proliferative response
  • chloride increased
  • proliferation appears


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