Photoreactivation of ultraviolet radiation-induced skin and eye tumors of Monodelphis domestica

Chronic exposure of the opossum Monodelphis domestica to UV radiation (UVR) leads to the formation of cutaneous and corneal tumors. Groups of shaved opossums were exposed 3 times/week to: (a) UVR alone; (b) UVR followed immediately by 1 h of photoreactivating light (PRL) (320-700 nm); (c) 1 h of PRL...

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Bibliographic Details
Published in:Cancer research (Chicago, Ill.) Ill.), 1991-12, Vol.51 (24), p.6539-6542
Main Authors: LEY, R. D, APPLEGATE, L. A, FRY, R. J. M, SANCHEZ, A. B
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Carcinogenesis, carcinogens and anticarcinogens
Cornea
Deoxyribodipyrimidine Photo-Lyase
DNA Repair
Eye Neoplasms - etiology
Medical sciences
Monodelphis domestica
Neoplasms, Radiation-Induced - etiology
Opossums - physiology
Physical agents
Pyrimidine Dimers
Skin Neoplasms - etiology
Tumors
Ultraviolet Rays
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Summary:Chronic exposure of the opossum Monodelphis domestica to UV radiation (UVR) leads to the formation of cutaneous and corneal tumors. Groups of shaved opossums were exposed 3 times/week to: (a) UVR alone; (b) UVR followed immediately by 1 h of photoreactivating light (PRL) (320-700 nm); (c) 1 h of PRL followed by UVR; and (d) 1 h of PRL alone. Exposures were terminated after 70 weeks of treatment. Analysis of data plotted as probability of tumor formation versus weeks from first exposure shows that post-UVR exposure to PRL significantly (P less than 0.005) delayed the time to appearance of cutaneous tumors from a 50% probability of tumor formation at 73 weeks for those animals exposed to UVR alone to 128 weeks for those animals exposed to PRL after UVR. Pre-UVR exposure to PRL delayed the appearance of tumors by 6 weeks when compared to the UVR alone group, but the difference between the two groups was not statistically significant. The yield (number of tumors/surviving animal) of cutaneous tumors at 70 and 110 weeks following initiation of treatments also was significantly less in those animals exposed to PRL after, but not before, UVR. Based on the specificity of the PR repair pathway to act only on pyrimidine dimers, these results suggest that dimers are involved in the induction of cutaneous tumors. The results obtained with the induction of corneal tumors are more difficult to interpret. While exposure to PRL significantly delayed the appearance of corneal tumors, the magnitude of the effect was the same regardless of whether the PRL was given before or after each UVR exposure.
ISSN:0008-5472
1538-7445