siRNA mediated inhibition of WEE1 results in decreased cell viability and increased apoptosis in vitro. (A) Kaplan-Meier plots for EFS and OS in 88 neuroblastoma patients (Amsterdam) based on median WEE1 mRNA expression. P values were obtained using log-rank test. Box and whiskers plots represent the expression of WEE1 in a cohort of 88 primary neuroblastoma tumors. Samples are grouped according to known risk factors and expression compared in each of; MYCN amplified versus Non MYCN amplified and INSS Stage 4 versus INSS Stage 1,2,3,4S. Statistical differences in median expression were analysed using two sided Mann–Whitney U tests. Dark shading indicates known higher risk factor. HR= Hazard Ratio. (B) Neuroblastoma MYCN-amplified cell lines Kelly (n=3), CHP-212 (n=3) and non-MYCN-amplified SK-N-AS (n=3) were transfected with siWEE1 /siNegative control (siNeg Control). Viability of cells was measured by MTS assay at 24 hr, 48 hr, 72 hr and 96 hr post transfection. (C) Mean percentage of annexin V+ Kelly, CHP-212 and SK-N-AS cells, from at least three independent experiments at 96 hr post transfection with siWEE1 /siNegative control (siNeg Control). (D) Images of siWEE1 inhibited cells versus siNegative controls (siNeg Control) in Kelly, CHP-212 and SK-N-AS.