The Role of p75NTR and Its Signaling Pathways in Fenretinide (4HPR)-Induced Apoptosis in Neuroblastoma Cells (P06.003)

Abstract

Objective: The overall goal is to understand the role of p75NTR and its signaling pathways in Fenretinide (4-hydroxyphenyl retinamide - 4HPR) induced apoptosis in neuroblastoma cells and determine some of the signaling pathways that mediate this effect. Understanding the role of p75NTR in mediating 4HPR-induced apoptosis will facilitate development of targeted therapies for the treatment of neuroblastoma by providing insight into pathways that could be targeted for combination chemotherapy. Background 4HPR is well tolerated in clinical trials and has been shown to cause apoptosis by increasing ROS generation in cancer cells. Targeting minimal residual disease in neuroblastoma involves sensitizing these tumors to chemotherapeutics by manipulating receptor signaling. p75NTR has a pro/anti-apoptotic role depending on the intracellular conditions. Design/Methods: S-type neuroblastoma cells (SH-EP1, SK-N-AS, SK-N-MC) with varying amounts of p75NTR are used to determine the effect of p75NTR signaling on the 4HPR-concentration curve. Changes in oxidative stress as a result of 4HPR treatment are recorded using western blotting and fluorescent microscopy. Results: 4HPR reduces cell viability in a variety of neuroblastoma cell lines when they are treated for 24(15%)-72 hrs (40%). p75NTR expression is pro-apoptotic and sensitizes SH-EP1 cells by decreasing viability, metabolic health and upregulating 4HPR-induced apoptosis. Treatment of SH-EP1 cells with 4HPR for 72 hours revealed no change in production of cellular OH- or cytoslic O2- but a sharp increase was observed in mitochondrial O2- production(Scr>p75shRNA transfected SH-EP1). Scavenging oxygen radicals in the mitochondria or inhibiting Complex II inhibits the pro-apoptotic effect of Fenretinide. Akt signaling is upregulated in SH-EP1 cells with p75shRNA compared to native SH-EP1 cells. Conclusions: This will facilitate the sensitization of minimal residual disease and preventing recurrence using combination chemotherapeutics for treatment by creating conditions of increased oxidative stress and enhance response by tumors to conventional chemotherapeutics causing apoptosis. Disclosure: Dr. Ganeshan has nothing to disclose. Dr. Schor has nothing to disclose.