Susceptibility to prostate cancer : a study of interactions between ultraviolet radiation and candidate genes
Prostate cancer is the third most common cancer in men and the second largest
killer behind lung cancer. The beneficial effect of ultraviolet radiation (UVR) on the
development of certain internal cancers including the prostate has previously been
shown. Epidemiological studies in the USA showed a link between latitude and
prostate cancer mortality and this led to confirmation of a protective effect of UVR in
the development of prostate cancer in a small group of 210 cancer patients recruited in
North Staffordshire, UK between 1999 and 2000. In this study, we confirmed this
association in a further group of 243 independently recruited prostate cancer patients.
We also showed that various parameters of UVR exposure have an increased
protective effect in the development of the disease in combination compared with
individually. Skin type was also found to be a risk factor in prostate cancer
development especially in men with low levels of UVR exposure.
The mechanism for this protective effect is postulated to involve vitamin D via
the interaction of UVR exposure on the skin. Polymorphisms in genes associated with
skin pigmentation (tyrosinase) and vitamin D (vitamin D receptor, vascular
endothelial growth factor) were also shown to be significantly associated with
prostate cancer risk, again, especially when patients were stratified by UVR exposure.
These findings provide further evidence that the mechanism behind the UVR effect
involves vitamin D.
The level of UVR that is needed to obtain this benefit needs to be ascertained
as it is well known that too much exposure to UVR increases individual risk of
developing skin cancer. Accordingly, these findings may eventually have major
public health implications.