The SNP309 genotype influences sensitivity of B-CLL cells and B cells from healthy controls to in vitro-treatment with nutlin-3a. PBMCs from (A) B-CLL patients or (B) healthy donors with T/T, T/G or G/G SNP309 genotype were treated with increasing concentrations of nutlin-3a for 24 hours. Analysis of apoptosis in the CD19+CD5+ fraction (A, B-CLL) or CD19+ fraction (B, healthy controls) was performed by the annexin V–fluorescein isothiocyanate binding assay. The relative number of cells undergoing nutlin-3a-induced apoptosis are presented as the percentage of untreated control. Sample numbers within the respective genotype subgroup are indicated.