Photocarcinogenesis Flashcards
define clonal evolution
series of mutations that accumulate in several generations
cell eventually becomes mutated enough to be cancerous
define oncogene
over active form of a gene that positively regulates cell division
doesnt require GF
proto-oncogene
normal not yet mutated form of oncogene
oncogene examples
Ras, Raf
what is inactivated during tumour growth
tumour suppressor
what type of skin cancer can sunbeds cause
ALL
what type of skin cancer does chronic long term exposure cause
SCC
what type of skin cancer does burning and intense intermittent exposure cause
melanoma and BCC
DOUBLE RISK
what are 2 genetic predispositions to skin cancer
albinism and xeroderma pigmentosum
xeroderma pigmentosum
ability to repair damage caused by UV light is impaired, patients have extreme photosensitivity
what happens neurologically in xeroderma pigmentosum
neurological degeneration
defect in what genes causes xeroderma pigmentosum
NER genes
what autoimmune conditions inc risk of skin cancer
crohns (80%) and UC (23%)
what effect does organ transplantation have on skin cancer risk
NMSC risk 29-33 times higher (especially SCC) malignant melanoma risk more than double
UVB effect on DNA
DIRECT
the signature type of DNA damage is PYRIMIDINE DIMER
what is the signature mutation of UVB
TT to CC
name 2 types of UVB induced DNA lesion
cyclobutane pyrimidine dimer (CPD) and 6-4PP
what bonding is present in CPD and 6-4PP
covalent
how are CPD and 6-4PP removed
nucleotide excision repair
UVA damage to DNA
indirect via oxidation of DNA bases espeically dG to 8-oxo-dG
UVA signature mutation
C to A point mutation
how are oxidised bases (UVA) repaired
base excision repair
what type of skin cancer does UVA cause
non melanoma skin cancer
