Discuss the role of UV light and other environmental exposures in the pathogenesis of malignancy with particular reference to the skin

- Melanoma, SCC and BCC.

Which skin cancers is UV radiation linked to?

- Total cumulative exposure to UV.

Non-melanoma skin cancer is associated with what exposure to UV-rays?

- Intense and intermittent exposure.

Melanomas are associated with what exposure to UV-rays?

- Due to formation of pyrimidine dimers in DNA.

- Photon of UV light absorbed by DNA --> covalent cross-linking of pyrimidine bases --> distorted DNA helix + impairing proper matching of dimers with bases.

- These pyrimidine dimers are usually repaired by the nucleotide excision repair pathway but can be overwhelmed in excessive sun exposure.

Describe how UV rays cause carcinogenicity

- Carcinogenic, commonly causes melanoma in patients using tanning beds.

- Forms pyrimidine dimers but at a slower rate than UVB.

- Can penetrate windows and cloud cover.

Describe UVA

- Most carcinogenic form of UV.

- Causes pyrimidine dimers to form.

- Dimers usually repaired by nucleotide excision pathway but is overwhelmed in excessive sunlight.

- Cannot penetrate glass.

Describe UVB

- Natural chemical found in groundwater.

- Known to cause skin cancer as well as lung, bladder, liver and kidney.

- Interferes with DNA repair mechanisms.

Describe the role of arsenic in carcinogenesis