(a) Clonogenic survival assay of dermal fibroblasts. Fibroblast cells (102 to 5 × 104) were incubated with 0–10 μM SU9518 in presence of 10 ng/ml PDGF-AB. Cultures were returned to the incubator for 14–17 days, after which they were stained with crystal violet (Sigma, Germany). Colonies were counted and the surviving percentage was determined for clonogenic survival after correcting for plating efficiency. Bars are means of 5 experiments ± SD. (b) Clonogenic survival assay of human dermal microvascular endothelial cells (HDMVECs). Endothelial cells were treated with 0–10 μM SU9518 in the presence of 10 ng/ml PDGF-AB in the media. Surviving fraction was calculated based on the number of colonies counted after 14–17 days. Bars are means of 5 experiments ± SD.