Figure 2. OSU-03012 toxicity in transformed cells is enhanced by Lapatinib. (A) GBM5; (B) GBM6; (C) GBM12; (D) GBM14 cells were treated with vehicle (DMSO); OSU-03012 (OSU) (1 μM) and/or Lapatinib (1.0 μM) as indicated. Cells were isolated 24h and 48h later and viability determined by trypan blue exclusion assay (n = 3 ± SEM). (E) DAOY, D283 and VC312 cells were treated with vehicle (DMSO); OSU-03012 (OSU) (1 μM) and/or Lapatinib (1.0 μM) as indicated. Cells were isolated 48h later and viability determined by trypan blue exclusion assay (n = 3 ± SEM). (F and G) GBM6 and GBM12 cells were plated as single cells in sextuplicate. Twelve h after plating cells were treated with OSU (0–250 nM) and Lapatinib (0–1.0 μM) at a fixed concentration ratio. After 48h media was removed, the cells washed and drug free media added. Colonies formed over ~14 d. A colony was defined as a group of > 50 cells. A combination index of < 1.00 indicates a synergy of drug interaction (n = 3 ±SEM).