4.6. IC50 Determination

Cell line IC50s for vandetanib were obtained for a panel of 20 cell lines. Cells were plated on 96-well plates at a concentration of 15,000 cells/mL (3000 cells/well) prior to treatment with vandetanib (serially diluted from 160 μM to 0.25 μM) for 24 h. IC50 was measured five days following drug treatment via cellular metabolism of resazurin. Cell culture media was replaced with Fluorobrite^TM media containing 10 μg/mL resazurin. Resazurin metabolism into fluorescent resorufin was monitored for up to 4 h, at which point fluorescence emission at 590 nm was measured with a Perkin Elmer Envision 2103 plate reader (Waltham, MA, USA), and the dose corresponding to 50% survival was determined from the survival curves using Graphpad Prism (San Diego, CA, USA).