Lec 45 Flashcards
Why do cells become cancerous
cancer critical genes
Encode proteins involved in the cell cycle
Tumor suppressor gene
Inhibit cell cycle
mutation can happen to this to cause cancer
Proto-oncogenes
Promote cell cycle
mutation can occur to this
to cause cancer
Why cancer happens
New (somatic) mutations
Mutation happens within the person which alters the protein amount and activity
Why cancer happens
inherited mutation
Mutation is inherited from a parent
Alters protein amount and activity
Why cancer happens
viral infection
Some viruses deliberately cause cancer to facilitate their own reproduction
how much of cancer is caused by viral infection
more than 10 percent
Initiation can occur by either
Unregulated cell reproduction due to loss of tumor suppressor genes
Normal function of tumor suppressor genes
Inhibit cell proliferation
Causes cancer when non-functional
Rb stops cell cycle at
g1 checkpoint
Nonfunctional Rb cell can cause cancer
Initiation
Unregulated cell reproduction due to proto-oncogene turning into an
oncogene
Proto-oncogene normal function
Stimulate cell cycle
Can cause cancer if it becomes an overactive oncogene
HER2 example
Receiving too much of a GF/mitogen signal leads to over reproduction (initiation)
Progression
Genetic instability
Cancer cells acquire new mutations at more than the spontaneous rate because of a damaged p53 not patching up DNA damage
p53 is a
Tumor suppressor gene
PUMA is a
tumor suppressor gene because too few PUMA is dangerous
BCL2 is a
proto-oncogene because too many BCL2 proteins is dangerous
What proportion of human cancers have mutations in the TP53 gene
More than half
Properties that lead to metastasis/spread
Induce angiogenesis
Tumors can not grow without recruiting blood vessels because they need glucose and oxygen which comes from blood vessels
VEGF
positive mitogen/growth factor
harmful cells perform angiogenesis by releasing VEGF which recruit blood vessels which allow the cells to spread
Properties that lead to metastasis/spread
Invade neighboring tissue
Cancer cells spread if some of them dismantle the collagen (as if they were fibroblasts)
basically cancer cells pretend to be fibroblasts to breakdown collagen to move into new locations
Collagen
Contain cells
Fibroblasts
Normally move around by going through collagen
How many cells survive to reach new sites
0.1%
so many cells are in the new site though so it does not matter - they will be able to spread.
