A decreased ability to repair chromosomal damage caused by
exposure to ultraviolet B (UV-B) radiation in test tubes may be
associated with an increased risk of the common skin cancers basal
cell carcinoma and squamous cell carcinoma, but not of melanoma,
according to a study in the December 21 issue of the Journal of the
National Cancer Institute.
Exposure to UV radiation from sunlight is a risk factor for the
two most common skin cancers, basal cell carcinoma and squamous
cell carcinoma, and for the less common and potentially lethal skin
cancer cutaneous malignant melanoma. UV-B radiation can cause
strands of DNA to break in sun-exposed skin or skin cells. People
with a condition called xeroderma pigmentosum are at a very high
risk of sunlight-induced skin cancer because their cells are unable
to repair these kinds of DNA and chromosomal damage. However,
scientists did not know if the frequency of UV-B induced chromatid
breaks, an indirect estimate of DNA repair capacity, is a risk
factor for skin cancer in the general population.
Li-E Wang, M.D., and Qingyi Wei, M.D., Ph.D., of the University
of Texas M. D. Anderson Cancer Center in Houston, and colleagues
set out to answer this question by studying 469 patients with both
melanoma or nonmelanoma skin cancers and 329 cancer-free patients.
They took blood samples from all of the patients and then measured
the number of chromatid breaks in the patients' cells 24 hours
after the blood samples were exposed to UV-B radiation.
They found that a high number of chromatid breaks was associated
with a nearly threefold increased risk of basal cell and squamous
cell carcinomas but was not associated with risk of melanoma. The
risk of the nonmelanoma skin cancers associated with chromatid
breaks increased with increased experimental exposure to UV-B
radiation. They also found that sensitivity to UV-B radiation may
interact with other known risk factors, such as hair color, skin
color, sunburn history, tanning ability, and freckling, to increase
risk of squamous cell and basal cell carcinomas, but they did not
find the same relationship between chromatid breaks and risk of
melanoma.
"These findings suggest that in vitro UVB-induced mutagen
sensitivity reflects susceptibility to [nonmelanoma skin cancer]
but not [cutaneous malignant melanoma]," the authors write. They
note that their findings should be investigated further in
prospective studies.
Journal of the National Cancer Institute
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