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Title: Combination of azathioprine and UVA irradiation is a major source of cellular 8-oxo-7,8-dihydro-2’-deoxyguanosine.
Authors: Cooke, Marcus S.
Duarte, Tiago L.
Cooper, Deborah
Chen, Jie
Nandagopal, Sridevi
Evans, Mark D.
First Published: 1-Oct-2008
Publisher: Elsevier
Citation: DNA Repair, 2008, 7 (12), pp. 1982-1989.
Abstract: Thiopurine antimetabolites, such as azathioprine (Aza) and 6-thioguanine (6-TG), are widely used in the treatment of cancer, inflammatory conditions and organ transplantation patients. Recent work has shown that cells treated with 6-TG and UVA generate ROS, with implied oxidatively generated modification of DNA. In a study of urinary 8-oxo-7,8-dihydro-2’-deoxyguanosine (8-oxodG) in renal transplant patients, we provided the first in vivo evidence linking Aza and oxidatively damaged DNA. Using the hOGG1 comet assay we herein demonstrate high levels of 8-oxodG and alkali-labile sites (ALS) in cells treated with biologically relevant doses of 6-TG, or Aza, plus UVA. This damage was induced dose-dependently. Surprisingly, given the involvement of 6-TG incorporation into DNA in its therapeutic effect, significant amounts of 8-oxodG and ALS were induced in quiescent cells, although less than in proliferating cells. We speculate that some activity of hOGG1 towards unirradiated, 6-TG treated cells, implies possible recognition of 6-TG or derivatives thereof. This is the first report to conclusively demonstrate oxidatively damaged DNA in cells treated with thiopurines and UVA. These data indicate that Aza-derived oxidative stress will occur in the skin of patients on Aza, following even low level UVA exposure. This is a probable contributor to the increased risk of non-melanoma skin cancer in these patients. However, as oxidative stress is unlikely to be involved in the therapeutic effects of Aza, intercepting ROS production in the skin could be a viable route by which this side effect may be minimised.
ISSN: 1568-7864
Type: Article
Rights: This is the author’s final draft of the paper published as DNA Repair, 2008, 7 (12), pp. 1982-1989. The final published version is available at, Doi: 10.1016/j.dnarep.2008.08.007.
Appears in Collections:Published Articles, Dept. of Cancer Studies and Molecular Medicine

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