IM and Rap synergistically inhibit the proliferation of Ba/F3/kit cITD. (A) Ba/F3/kit WT and Ba/F3/kit cITD cells were treated with the indicated doses of (i) IM, (ii) Rap, and (iii) LY294002 for 48 hours. ³H-thymidine incorporation was determined. Control cells were treated with DMSO (dimethyl sulfoxide) vehicle. (B) Ba/F3/kit cITD cells were exposed to varying concentrations of IM and Rap at a constant ratio of 1000:1 for 48 hours. Proliferation was assessed by ³H-thymidine incorporation. The combination index was determined. Values below 1.0 correspond to synergy, with values below 0.3 corresponding to very strong synergy. Points are the mean of triplicate determinations; bar, ± SD.