Sorafenib and sodium valproate synergize in colony formation assays to kill rhabdomyosarcoma cells
Rhabdomyosarcoma (Rh41) cells were treated 12 h after plating as single cells (250-1500 cells/well) in sextuplicate with vehicle (DMSO), sorafenib (2.0-9.0 μM), sodium valproate (0.33-1.5 mM), or with both drugs combined, as indicated at a fixed concentration ratio to perform median dose-effect analyses for the determination of synergy. After drug exposure (48 h), the medium was changed and cells cultured in drug-free media for an additional 10 to 14 days. Cells were fixed and stained with crystal violet, and colonies of >50 cells/colony counted. Colony formation data were entered into the Calcusyn program, and combination index (CI) values were determined. A CI value of less than 1.00 indicates synergy; a CI value of greater than 1.00 indicates antagonism.
Cell Line | Sorafenib | Valproate | CI |
|---|---|---|---|
| μM | mM | ||
| Rh41 | 3.0 | 0.50 | 0.82 |
| 4.5 | 0.75 | 0.73 | |
| 6.0 | 1.00 | 0.40 | |
| 7.5 | 1.25 | 0.31 | |
|
| 9.0 | 1.50 | 0.12 |