Lamers et al. BMC Cancer 2012, 12:285 http://www.biomedcentral.com/1471-2407/12/285 Page 5 of 10 Figure 1 Gain of BIRC5 and BIRC6 and loss of CASP9 in neuroblastoma tumors. a: The percentage of genomic aberrations is presented on the Y-axis and all selected genes in the intrinsic apoptotic pathway on the X-axis. Red bars indicate gained genes and green bars indicate lost genes. When a bar is green/red combined, it means that both gains and losses in that gene occurred. The red horizontal line represents the cut- off for further analysis. b: Chromosome 2 is represented with the regions of 2p that are gained in our dataset of 88 neuroblastoma tumors. The BIRC6 locus is indicated with a red arrow. c: Boxplots of BIRC6 mRNA expression in tumors with or without gain of BIRC6. d: Boxplots of BIRC6 mRNA expression in 3 neuroblastoma datasets (red), adult tumors (blue) and various normal tissues (green). The boxes represent the 25th to 75th percentile with the median depicted as a horizontal line. Extremes are indicated by the whiskers, and the presence of outliers is indicated by (o). BIRC6 expression in tumors with and without BIRC6 gain, which shows that tumors with BIRC6 gain have sig- nificantly higher BIRC6 RNA levels (Student T-test: P = 3.1*10-6) (Figure 1c). Moreover, BIRC6 is also highly expressed compared to several adult tumors and various normal tissues (Figure 1d). These findings suggest that the aberrant expression of BIRC6 is at least partially caused by genomic aberrations often occurring in neuro- blastoma tumors. BIRC6 knockdown induces apoptosis in neuroblastoma cells We investigated whether the high BIRC6 levels indeed counteract apoptosis in neuroblastoma. We used 2