Photocarcinogenesis Flashcards
What is carcinogenesis?
Carcinogenesis is the process by which a normal cell becomes a malignant cancer cell
What gene damage takes place for uncontrolled cell proliferation?
gain of function of oncogenes (accelerator)
AND
loss of function of tumour suppressors (brakes)
Describe tumour suppression?
CDKI, p53, retinoblastoma (Rb) - often inactivated by mutation or by loss of heterozygosity
Describe ocogenes
CYCLINS, RAS, MYC “proto-oncogenes” - activated by mutation or by copy gain
What are the hallmarks of cancer?
- Autonomous growth signals
- Insensitivity to anti-growth signals
- Resist cell death (apoptosis)
- Limitless potential to divide
- Angiogenesis
- Invasion and metastasis
How are Dimers removed?
Nucleotide excision repair
What does NER and BER stand for?
Nucleotide Excision Repair
Base Excision Repair
What does DSB and MMR stand for?
Double Strand Break Repair
Mismatch Repair
What wavelength of UVB is the principle carcinogen?
290-320nm
What type of damage do UVB and UVA cause?
UVB = direct DNA damage UVA = indirect oxidative damage
What type of mutation does UVB generate?
C-T or CC-TT ‘signature’ mutations
What changes does UVA induce?
Guanine oxidation products in DNA. A specific marker for this is 80HdG (8 hydroxydeoxy guanosine)
What cells are effected in UV induced immunosuppression?
Dendritic cells, they lose the ability to present antigen
Why do ‘red heads’ do worse in the sun?
The have:
- Pheomelanin instead of eumelanin
- Pheomelanin absorbs UV less efficiently
- Unable to tan in an effective way
What is the TP53 mutation?
found in AK, carcinoma-in-situ & SCC
