2: Photocarcinogenesis Flashcards
What causes a cell to become cancerous?
Genetic mutations
What is clonal evolution?
Accumulation of mutations over multiple generations of cells
What are the hallmarks of cancer?
Uncontrolled cell division
Evade immune system
Invade tissues
Become immortal
Develop own blood supply
Don’t die
What aspect of the immune system can melanoma cells use to prevent their own destruction?
Cytokines
Which type of gene promotes cell division?
Oncogene
What is an example of an oncogene?
RAS
RAF
What is a proto-oncogene?
Unmutated oncogene i.e nothing is wrong with it yet
Which type of gene suppresses cell division?
Tumour suppressor
What is an example of a tumour suppressor gene?
Rb (retinoblastoma in cell cycle)
p53
What do oncogenes trigger?
Through which signalling molecule do they achieve this?
Cell division and proliferation
Growth factors
If a cell detects that its DNA is damaged, which tumour suppressor gene is activated?
p53
Which tumour suppressor gene halts the cell cycle if it detects DNA damage?
What happens to cells if their DNA cannot be repaired?
p53
Apoptosis
What are the two broad categories of skin cancer?
Malignant melanoma
Non-melanoma skin cancer
What are two types of non-melanoma skin cancer?
Basal cell carcinoma
Squamous cell carcinoma
In which epidermal layer are cancerous keratinocytes found in:
a) squamous cell carcinoma
b) basal cell carcinoma?
a) anywhere except the basal layer
b) basal layer only
What are the risk factors for skin cancer?
UV exposure
Genetics
Age
Immunosuppression
Chemical exposure
People with which category of skin are more likely to burn than tan?
I
People with ___ skin are less likely to develop skin cancer.
dark
Which pigment protects the DNA of basal cells from UV radiation?
Melanin
Which genetic condition causes patients not to produce melanin, increasing their chances of developing skin cancer?
Albinism
In which genetic condition does a patient’s DNA repair mechanism not work?
Xeroderma pigmentosum
Name some chemicals which are thought to increase a patient’s risk of non-melanoma skin cancer.
Coal tar pitch
Soot
Arsenic
Which two autoimmune GI conditions increase your chances of developing malignant melanoma?
Ulcerative colitis
Crohn’s disease
What are some examples of immunosuppressant drugs which increase your chance of developing skin cancer?
Azathioprine
Cyclosporin
Monoclonal antibodies
People who have received ___ ___ are more likely to develop skin cancer.
Organ transplants
probs cuz they’re on immunosuppressants
Which wavelengths of light are responsible for skin cancer?
UVA
UVB
Which wavelength of light causes direct DNA damage?
UVB
What wavelength of light causes indirect oxidative DNA damage?
UVA
What kind of DNA damage does UVA exposure cause?
Pyrimidine dimers between bases
Which wavelength causes pyrimidine dimers to be added to DNA?
Which wavelength causes oxidation of DNA bases?
UVB
UVA
By which mechanism does DNA repair itself after UVB radiation absorption?
How does this work?
Nucleotide excision repair
- Damaged base is cleaved off
- DNA polymerase fills in the gap using the other strand as a template
- DNA ligase seals up the gaps
Why does UV radiation cause immunosuppression?
Langerhans cells are depleted – less antigen presentation to T cells
Regulatory T cells produced
Anti-inflammatory cytokines produced
Mutations in which gene are associated with basal cell carcinoma?
PTCH1
Which signalling pathway is involved in basal cell carcinoma?
Hedgehog pathway
Which drug can be used to ?prevent basal cell carcinoma progression?
Vismodegib
Which signalling pathway is involved in the development of melanoma?
RAS / RAF pathway
Which type of drug can be used to block signalling pathways involved in the development of skin cancer?
Monoclonal antibodies
The gene for which protein, involved in the cell cycle, can mutate to cause familial melanoma?
CDK4
What should you do to cut your risk of developing skin cancer?
Sunscreen
Wear clothes
Avoid sun between 11am and 3pm
etc
