Rottlerin: a multifaced regulator of keratinocyte cell cycle.

In this study we showed that Rottlerin (also called Kamala or Mallotoxin), a natural product purified from Mallotus phillippinensis, is a potent suppressor of human keratinocytes (HaCaT cell line) proliferation. Following Rottlerin treatment, Thymidine incorporation into DNA and re-epithelialisation in a scratch wound model was decreased. At the molecular level, Rottlerin hampered the NFkB activation process, causing loss of cyclin D1 and promoting, in a PKCdelta-dependent pathway, ERK activation, which, in turn induced the cell cycle inhibitor p21 Cip1/Kip1. The NFkB-dependent drop in cyclin D1, along with the PKCdelta/ERK-dependent induction of p21 Cip1/Kip1, is responsible for growth arrest. These results open the way to further investigation on the Rottlerin therapeutic potential against keratinocyte hyper-proliferative disorders.