Rapamycin inhibits HMC-1 (D816V) proliferation. (A-B) Rapamycin activity was assessed on the proliferation of HMC-1 (D816V; A) and α-155 (V560G; B), respectively. Cells were incubated with different concentrations (5 and 50 nM) of rapamycin (▪ and ▦, respectively) or with medium alone containing diluted-ethanol rapamycin buffer (□) for 24 to 72 hours. (C-D) HMC-1 (D816V; C) and α-155 (V560G; D), respectively, were incubated alone (□), with rapamycin (5 nM; ▪), with imatinib (1 μM; ▦), or both imatinib and rapamycin (dotted columns) for 24 and 48 hours. Numbers of viable cells were assessed by trypan blue exclusion. Data represent means ± SD of 3 separate experiments, each plated in triplicate.