Breast Cancer

  1. Breast cancer is influenced by...
    • Diet
    • Environment
    • Genetic propensity
    • Birth control
  2. Hypothesis of origin of breast cancer
    • Increase in house mice population in high population densities
    • Mice carry MMTV (Mouse mammary tumor virus) = mouse equivalent of breast cancer
    • Suspicions that a similar virus contributes to breast cancer in humans
  3. First evidence to support hypothesis
    • Analysis of 314 breast tissue samples
    • 38.5% had sequences similar to MMTV
    • Not reliable because not in all populations
  4. 2nd piece of evidence
    • Geographical frequency of breast cancer similar to geographical distribution of the house mouse species
    • Mus domesticus (house strain) more infected with MMTV than related Mus musculus
    • Domesticus in Western Europe and Musculs in Eastern Europe = higher rate of breast cancer in Western Europe
    • Not reliable b/c data works for other hypotheses
    • No evidence for human-human transmission of MMTV b/c tissue can't be isolated
  5. Koch's postulates
    • Idealized goal for human pathogenic disease causation
    • 1. Pathogen present in all cases of disease and not present in healthy animals
    • 2. Should be able to grow in pure culture
    • 3. Give the animal the pathogen and it should cause disease in the animal
    • 4. Organism reisolated and shown to be the same as the orginal pathogen
  6. Environmental contributor to breast cancer
    • Control of repoduction & increased nutrition = more menstrual cycles
    • More menstrual cycles = increased risk of breast cancer
  7. Breast cancer risks
    • Early onset of menses
    • Delay to initial child's birth
    • Less time spent nursing children
  8. Molecular model to explain risks
    Increase menstrual cycle = Periodic high levels of estrogen and progesterone = stimulate cell division = increases chance of mutations in genes that control tumor growth
  9. Epidemiological evidence (Dogon women)
    • Ages 20-35 spend less time menstruating - pregnant or lactational amenorrha
    • <30% are undergoing menstrual cycling
    • 100 cycles vs 400-500 in North American women
    • Breast cancer rates about 10% the North American rate
    • Every pregnancy in NA women is correlated with 10% in probability of ovarian or uterine cancer
Card Set
Breast Cancer
Week 1 lecture