Photocarcinogenesis Flashcards
Describe how a cancer cell emerges from multi-step gene damage
series of mutations accumulate in successive generations (clonal evolution)
a cell accumulates enough mutations to become cancerous
What are the Hallmarks of Cancer?
Sustained proliferative signalling Evading growth suppressors Acting Invasion and Metastasis Enabling Replicative immortality Inducing angiogenesis Resisting cell death
What are the Emerging Hallmarks of cancer?
Deregulating cellular energetics
Avoiding immune destruction
What are the enabling characteristics of cancer?
Tumour-promoting inflammation
What is an oncogene?
Over-active form of a gene that positively regulates cell division
Drives tumour formation when activity or copy number is increased
Give examples of oncogenes
Ras, Raf, growth factor receptors
What is a Proto-oncogene?
normal, not yet mutated, form of an oncogene
What is a tumour suppressor?
Inactive or non-functional form of a gene that negatively regulates cell division
Prevents the formation of a tumour when functioning normally
Give examples of tumour suppressors
p53
Rb
What is different in the Ras pathway when a mutation occurs?
Ras is constantly on and stimulating cell division
usually it has the ability to turn off and halt this process
What happens when there is a lack of p53
DNA damage is unrepaired in the G1 checkpoint, therefore mutations are carried down during cell division
How many different Fitzpatrick Skin Types are there?
Skin type I - always burns, never tans Skin type II - usually burns, can tan Skin type III - can burn, but usually tans Skin type IV - always tans, never burns Skin type V - ‘brown’ skin Skin type VI - ‘black’ skin
What type of melanin can be found in Skin Type 1 that is responsible for freckling?
Pheomelanin
What occupational chemical exposures can increase the risk of non-melanoma skin cancer?
Coal tar pitch Soot Creosote Petroleum products, such as mineral oil or motor oil Shale oils Arsenic
By what percentage do IBD conditions increase the risk of skin cancer?
Ulcerative colitis 23% higher risk of malignant melanoma
Crohn’s disease 80% higher risk of malignant melanoma
Can UVA or UVB penetrate through glass?
UVA
Does UVA or UVB cause sunburn?
UVB
Does UVA or UVB cause pigmentation and skin ageing?
Both UVA and UVB
What is the difference in damage caused by UVA and UVB
UVB causes DIRECT DNA damage
UVA causes INDIRECT oxidative damage
What is the range of wavelengths for UVA?
320-400nm
What si the range of wavelengths for UVB?
290-320nm
What variation of DNA damage is typical of UV damage?
Pyrimidine Dimer (T=T)
What are the 2 major types of UVB induced DNA lesion?
cyclobutane pyrimidine dimers (CPDs)
MORE COMMON
pyrimidine–pyrimidone (6–4) photo-products
MORE DAMAGING
Both = formed by covalent bonding between adjacent pyrimidines on the same DNA strand
Name a common oxidation of a DNA base caused by UVA
deoxyguanosine to form 8-oxo-deoxyguanosine
this can then incorrectly base pair as G-A instead of the usual G-C
