title: Role of reactive oxygen species in the synergistic cytotoxicity of safingol-based combination regimens with conventional chemotherapeutics.
abstract: Exploiting the sensitivity of cancer cells to reactive oxygen species (ROS) has been suggested as a strategy for the selective elimination of cancer cells. In this study, the ROS-generating sphingolipid safingol was combined with various conventional chemotherapeutics, and the potential synergism of the safingol-based combination regimen was assessed using a panel of cancer cell lines. The IC(50) values of safingol using as a single agent were 1.4-6.3 µM, which are concentrations that are clinically achievable. While synergism was dependent on the drug molar ratios, a 4:1 molar ratio of safingol to conventional chemotherapeutics exhibited a moderate to strong synergism in MDA-MB-231, JIMT-1, SKOV-3, U937 and KB cells, with combination indices ranging from 0.07 to 0.77. Furthermore, the addition of safingol may reduce the concentrations of conventional chemotherapeutics required to achieve 90% cell-kill by 1 to >3 log-folds. A significant reduction in the cytotoxicity of safingol-based drug combinations was observed in the presence of N-acetyl-L-cysteine, suggesting that ROS is an important factor in mediating the observed synergism. Taken together, our results suggest that the use of safingol-based drug combinations is promising as an effective strategy for cancer therapy and should be investigated.
authors.affiliation: Department of Pharmacy, Faculty of Science, National University of Singapore, Singapore 117543, Republic of Singapore.
authors.forename: Leong-Uung
authors.initials: LU
authors.lastname: Ling
authors.forename: Kuan-Boone
authors.initials: KB
authors.lastname: Tan
authors.forename: Gigi N C
authors.initials: GN
authors.lastname: Chiu