Drug interactions on HMC-1.1 cells and HMC-1.2 cells. The effects of various drug combinations on growth of HMC-1.1 cells (upper right, □) and HMC-1.2 cells (lower left, ▦) were determined by ³H-thymidine incorporation assay. Each drug combination was tested in at least 3 independent experiments. Drugs were applied at fixed ratio and resulting effects (and the type of drug interaction) were determined by Calcusyn software. Score: +, synergistic growth-inhibitory effect; ±, additive effect; -, less than additive (antagonistic) effect; n.t., not tested.