C10ORF10/DEPP, a transcriptional target of FOXO3 regulates ROS-sensitivity by destabilizing peroxisomes in human neuroblastoma

FOXO transcription factors control cellular formation of reactive oxygen species (ROS), which critically contribute to cell survival and cell death in neuroblastoma. Here, we report that C10orf10, also named “Decidual Protein induced by Progesterone (DEPP)”, is a direct transcriptional target of FOXO3 in human neuroblastoma. As FOXO3-mediated apoptosis involves a biphasic ROS accumulation, we analyzed cellular ROS levels in DEPP-knockdown cells by live-cell imaging. Knockdown of DEPP prevented the primary and secondary ROS accumulation during FOXO3 activation and attenuates FOXO3-induced apoptosis, whereas its overexpression raises cellular ROS levels and sensitizes to cell death. In neuronal cells, cellular steady state ROS are mainly detoxified in peroxisomes by the enzyme CAT/catalase. As DEPP contains a peroxisomal-targeting-signal-type-2 (PTS2) sequence at its N-terminus that enables protein import into peroxisomes, we analyzed the effect of DEPP on peroxisomal function by measuring the catalase enzyme activity. Catalase activity was reduced by conditional DEPP overexpression and significantly increased in DEPP-knockdown cells. Using live cell imaging and fluorescent peroxisomal and mitochondrial probes we demonstrate that DEPP localizes to peroxisomes and mitochondria in neuroblastoma cells. The combined data indicate that DEPP reduces peroxisomal activity and thereby impairs the cellular ROS detoxification capacity and contributes to death sensitization. SH-EP, NB15 neuroblastoma cells and CCRF-CEM-C7H2 acute lymphoblastic leukemia cells were infected with the retrovirus plasmid pLIB-FOXO3(A3)-Ertm-iresNeo. Gene expression measures of samples with activated FOXO3 transcription factor (3h OHT treated) have been compared to untreated samples (0h time point). To rule out gene regulations by estrogen samples treated for 3 hours with tamoxifen have been compared to the untreated samples. Only genes that were more than two-fold regulated in the first, but not in the second comparison were defined to be FOXO3 regulated.