Reduction of UV-induced skin tumors in hairless mice by selective COX-2 inhibition

UV light is a complete carcinogen, inducing both basal and squamous cell sk in cancers, The work described uses the selective COX-2 inhibitor celecoxib to examine the efficacy of COX-2 inhibition in the reduction of UV light-i nduced skin tumor formation in hairless mice. UVA-340 sun lamps were chosen as a light source that effectively mimics the solar UVA and UVB spectrum. Hairless mice were irradiated for 5 days a week for a total dose of 2.62 J/ cm(2). When 90% of the animals had at least one tumor, the mice were divide d into two groups so that the tumor number and multiplicity were the same ( P < 0.31). Half of the mice were then fed a diet containing 1500 p.p.m. cel ecoxib. Tumor number, multiplicity and size were then observed for the next 10 weeks. Ninety-five percent of the tumors formed were histopathologicall y evaluated as squamous cell carcinoma, COX-2 expression and activity were increased in tumors. After 10 weeks, the difference in tumor number and mul tiplicity in the drug-treated group was 56% of UV controls (P < 0.001), The results show that the orally administered selective COX-2 inhibitor celeco xib prevents new tumor formation after the onset of photocarcinogenesis and suggest that treatment with celecoxib may be very useful in preventing UV- induced skin tumors in humans.