Transcript Cancer cells grow and divide when they should not

The Cell cycle: Mitosis
http://www.youtube.com/watch?v=C6hn3sA0ip0
At what stage do the chromosomes line up in the
center of the cell?
25%
A.
B.
C.
D.
25%
25%
B.
C.
25%
Prophase
Metaphase
Anaphase
Telophase
A.
D.
When do the microtubules retract and pull the sister
chromatids to opposite poles of the cell?
25%
A.
B.
C.
D.
25%
25%
B.
C.
25%
Prophase
Telophase
Metaphase
Anaphase
A.
D.
Cell cycle control and mutation
• Normal cells halt at
checkpoints – proteins
survey the condition of the
cell
• Cancer cells skip these
checkpoints
Cancer cells skip checkpoints due to DNA damage
• DNA can be physically damaged, or undergo mutation
– changes the structure and function of the protein coded by
the DNA
– mutations may be inherited, spontaneous or caused by
carcinogens
How can DNA damage happen?
25%
A.
B.
C.
D.
25%
25%
B.
C.
25%
Exposure to carcinogens
Exposure to radiation
Replication errors
All of the above
A.
D.
•
Mutations often occur in proto-oncogenes – genes that
code for cell cycle control proteins and regulatory proteins
Stimulates cell division
when conditions are RIGHT
OVER-stimulates cell division
when conditions are WRONG
• Tumor suppressor genes – stop cell division if conditions are not
favorable
– When mutated, can allow cells to override checkpoints
Stops cell division
Fails to stop cell division
Example proto-oncogene:
• HER2: senses growth factors and activates cell division
– Mutations that activate HER2 are found in many
aggressive breast cancers
Example tumor suppressor gene:
• BRCA1: repairs DNA breaks
– mutations that inactivate BRCA1 are associated with
breast and ovarian cancers
Mutations in these are associated with Hereditary
Cancers
A single mutation is not sufficient for
the development of cancer
• Multiple hit model – process of cancer
development requires multiple
mutations
• may be inherited (familial risk), most
are probably acquired
Cancer progression
•
Loss of contact inhibition – cells will
now pile up on each other
•
Angiogenesis – tumor gets its own blood
supply by making blood vessles
•
Loss of anchorage dependence
– enables a cancer cell to move
to another location
Metastasis of cancer cells
1. Cancer cells build their own blood vessels
2. invade surrounding blood vessels
3. transported by the circulatory system to distant
sites
4. invade new tissue and grow in
a new location