Breast Cancer

• Diet
• Environment
• Genetic propensity
• Birth control

• 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

• Analysis of 314 breast tissue samples
• 38.5% had sequences similar to MMTV
• Not reliable because not in all populations

• 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

• 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

• Control of repoduction & increased nutrition = more menstrual cycles
• More menstrual cycles = increased risk of breast cancer

• Early onset of menses
• Delay to initial child's birth
• Less time spent nursing children

Increase menstrual cycle = Periodic high levels of estrogen and progesterone = stimulate cell division = increases chance of mutations in genes that control tumor growth

• 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