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Cell Cycle
CANCER
Apoptosis is programmed cell death.
– a normal feature of
healthy organisms
– caused by a cell’s webbed fingers
production of
self-destructive
enzymes
– occurs in
development
of infants
– Cancer cells do not
undergo apoptosis
Signals for cell division
• Internal – checkpoints regulated (turned “on”
and “off” by proteins called cyclins.
• External – regulated by environmental factors
outside of the cell
External factors
• Growth factors
– Proteins released by some
cells that stimulate other
cells to divide
• density-dependent
inhibition
–crowded cells stop
dividing
• anchorage dependence
–to divide cells must
be attached to a
substrate
Cancer – uncontrolled cell division
Tumors
- uncontrolled growth
- cell cycle has no control
2 TYPES
Benign – noncancerous
Malignant – cancer
- metastasizes - spreads throughout the body
- lethal
Metastasis – spread of cancer cells
normal cell
cancer cell
bloodstream
Development of Cancer
• Cancer develops after 6 key
mutations (“hits”)
1) unlimited growth
• turn on growth promoter genes
It’s like an
2) ignore checkpoints
out-of-control
car with many
• turn off tumor suppressor systems failing!
genes
3) escape apoptosis
• turn off suicide genes
4) immortality = unlimited divisions
• turn on chromosome maintenance genes
5) promotes blood vessel growth
• turn on blood vessel growth genes
6) overcome anchor & density dependence
• turn off touch-sensor gene
What causes these “hits”?
• Mutations in cells can be triggered by
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UV radiation
chemical exposure
radiation exposure
heat
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cigarette smoke
pollution
age
genetics