Synergistic cell inactivation of human NHIK 3025 cells by cinnamaldehyde in combination with cis-diamminedichloroplatinum(II).

The cell-inactivating effect induced by cinnamaldehyde in combination with cis-diamminedichloroplatinum(II) (cis-DDP) on human NHIK 3025 cells in culture was investigated. Cell inactivation was measured as a loss in the ability of single cells to give rise to macroscopic colonies following drug treatment. Although 2 h treatment of asynchronous cells with 0.3 mM cinnamaldehyde alone induced little cell inactivation, the drug combination of 0.3 mM cinnamaldehyde and 10 microM cis-DDP resulted in synergistic cell inactivation. Cinnamaldehyde potentiated the cell-inactivating effect of cis-DDP by a dose-modifying factor of 1.8. Drug synergism was found to occur only when cinnamaldehyde and cis-DDP were given in simultaneous combination. Treatment of synchronized cells demonstrated that cinnamaldehyde potentiated the inactivating effect of cis-DDP in all phases of the cell cycle. Cinnamic acid and cinnamyl alcohol were found to have no synergistic or potentiating effect on cell survival following treatment of cells with cis-DDP, thus indicating the importance of an aldehyde moiety for drug synergism.