We previously reported that a phenolic compound,
petasiphenol, was a selective inhibitor of
DNA polymerase lambda (pol lambda) in vitro. We found here that another phenolic compound,
curcumin (
diferuloylmethane), which is known as an anti-chronic inflammatory agent and is structurally quite similar to
petasiphenol, was also a potent pol lambda inhibitor. The IC(50) values of
petasiphenol and
curcumin were 7.8 and 7.0 microM, respectively.
Curcumin, as well as
petasiphenol, did not influence the activities of replicative
DNA polymerases, such as alpha, gamma, delta, and epsilon, but also showed no effect even on the pol beta activity belonging to the X family.
Curcumin could prevent the growth of human NUGC-3
cancer cells with LD(50) values of 13 microM, and halted them at the G2/M phase in the cell cycle, whereas
petasiphenol suppressed the cell growth at 66 microM and arrested the cells at the G1 phase. These data showed that
curcumin and
petasiphenol were slightly different functionally. We also previously reported that novel anti-inflammatory terpeno
benzoic acids and
triterpenoids were inhibitors of mammalian
DNA polymerases. They could also efficiently inhibit the pol lambda activity, although they influenced the other polymerase species to the same extent, suggesting that there may be a physiological relationship between pol lambda inhibition and anti-12-O-tetradecanoylphorbol-13-acetate-induced
inflammation. Expectedly,
petasiphenol also showed an anti-12-O-tetradecanoylphorbol-13-acetate-induced inflammatory effect in mice. This finding may provide clues to investigating the molecular mechanism of
inflammation.