PTEN-regulated AKT/FoxO3a/Bim signaling contributes to Human cell glioblastoma apoptosis by platinum-maurocalcin conjugate

A previous report has shown that a chimera between a platinum complexing agent (1) and the cell penetrating peptide maurocalcin, synthesized with D-amino acids, (DMCa), termed Pt-1-DMCa, is a highly successful anticancer compound that works by targeting the intracellular redox system in glioblastoma (GBM) cells. However, the detailed cellular mechanism whereby the conjugate specifically kills tumor cells remains unclear. Herein, we show that Pt-1-DMCa induces apoptosis in Human U87 GBM cells through reactive oxygen species (ROS)-dependent modulation of the PI3K/AKT/FoxO3a signalling pathway. First, we found that Pt-1-DMCa treatment of these cells induces inhibition of AKT and nuclear accumulation of FoxO3a thereby facilitating transcription of the target genes Bim and PTEN. Modulation of the AKT/FoxO3a/Bim signaling pathway by RNA interference confirms that these signaling events are critical for Pt-1-DMCa-induced apoptosis of U87 GBM cells. Furthermore, we reveal that FoxO3a-mediated up-regulation of PTEN exerts an additional inhibitory effect on the AKT survival pathway. Thus, our results demonstrate that the conjugate can induce ROS-dependent FoxO3a-mediated apoptosis in U87 cells through PTEN-mediated inhibition of the PI3K/AKT survival axis. Our results help elucidate the molecular mechanisms underlying Pt-1-DMCa-induced cell death in U87 GBM cells and support a theoretical basis for future applications of the MCa peptide. (C) 2016 Elsevier Ltd. All rights reserved.