Photocarcinogenesis Flashcards
what is a proto-oncogene?
the normal, unmutated form of an oncogene
what is an oncogene
over-active form of a gene that positively regulates cell division
what is a tumour suppressor?
inactive/non-functional form of a gene that negatively regulates cell division
do tumour suppressor genes use a negative or positive feedback mechanism
negative
example of an oncogene?
Ras
Raf
growth factor receptors
example of a tumour suppressor gene?
Rb
Tp53
what happens to proto-oncogenes to promote cell division and proliferation?
growth factor binds to GF receptor GDP--> GTP switches Ras ON Binds to Raf Cell division etc etc
what happens when oncogenes to cause cancer?
Ras is constantly switched on
3 jobs of p53 to prevent cancer?
Halts faulty cells at G1 checkpoint
DNA repair activated
Apoptosis triggered
Most likely skin cancer you would get from long term sun exposure?
SCC
Most likely skin cancers you would get from intense intermittent sun exposure eg holiday
- Melanoma
2. BCC
Most likely skin cancer you would get from sunbeds?
SCC
What kind of immunosuppressing conditions heighten melanoma risk?
Crohn’s (80%)
UC (23%)
Organ transplantation
Which kind of UV exposure causes direct DNA damage?
UVB
which kind of UV exposure causes indirect DNA damage?
UVA
what mutations occur as a result of UVB damage?
pyrimidine dimer (TT -> CC)
How is direct DNA damage repaired?
nucleotide excision repair
How indirect DNA damage repaired?
base excision repair
Most common mutation in indirect DNA damage?
C->A point mutation
how can UV damage cause immunosuppression
less langerhans cells,
uv-induced generation of T cells will have immunosuppressive activity
Most common mutation in BCC?
PTCH1
Most common mutations causing melanoma?
Ras, Raf, MAPK
