Suppression by nobiletin of the TPA-induced increase in PCNA-positive cells in mouse epidermis. Suppression by nobiletin of the TPA-induced increase in PCNA-positive cells in mouse epidermis. Three mice were used in one experimental group. Nobiletin (810 nmol/100 μl of acetone) was topically applied to the shaved area of dorsal skin 30 min before application of a TPA solution (8.1 nmol/100 μl of acetone). After 24 h, the same dosages of nobiletin or acetone were applied 30 min prior to a second TPA application. Methods for PCNA staining are described in “Materials and Methods.” Ac, acetone; NOB, nobiletin. Akira Murakami et al. Cancer Res 2000;60:5059-5066 ©2000 by American Association for Cancer Research