Ambivalent Effects of Atorvastatin on Angiogenesis, Epidermal Cell Proliferation and Tumorgenesis in Animal Models

Background: A growing body of preclinical data indicates that statins may possess antineoplastic properties however, some studies have raised the possibility that statins may also have carcinogenic potential. Methods: An air pouch model was used for angiogenesis. Single or multiple applications of croton oil on the back of Swiss albino mice with or without initiation by dimethylbenz(a)antheracene (DMBA) were used to evaluate the skin tumorgenesis, ultrastructural and histological alterations. Results: Atorvastatin (orally, 10 mg/kg/day) produced a significant (P<0.05) reduction in angiogenesis. Concurrent administration of mevalonate reversed the anti-angiogenic effect of atorvastatin. However, local injection of atorvastatin (200 µg) into the pouches induced a significant (P<0.5) increase in angiogenesis that was not reversed by co-administration of mevalonate. The disturbance of cell polarity, inflammatory response, thickness of epidermal layer, and mitotic index induced by croton oil were inhibited markedly and dose-dependently (P<0.001) by pre-treatment with atorvastatin. In spite of the strong anti-inflammatory and anti-proliferative effects of atorvastatin on epidermal cell proliferation, it was identified that the same doses of atorvastatin in DMBA-initiated and croton oil-promoted skin tumorgenesis in mice increased the incidence of tumors and their conversion into malignant carcinoma. Conclusion: The reasons for these discrepancies remain unclear, and could be related to ambivalent effects of atorvastatin on angiogenesis or to specific differences in the experimental conditions. It is suggested that the pro-angiogenic effect of the drug, which could be responsible for promotion of skin tumors, is independent of the 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibition that can be mediated directly by atorvastatin.