Abstract 3105: Neuropeptide Y Y5 receptor in neuroblastoma chemoresistance
Authors: Trinh Emily , Czarnecka Magdalena , Hong Sung-Hyeok , Lu Congyi , Martin Samantha , Galli Susana , Izycka-Swieszewska Ewa , Kuan-Celarier Anna , Christian David , Horton Meredith , Tilan Jason U. , Kitlinska Joanna B. 
Published: May 2015

Abstract
Neuroblastoma (NB) is a pediatric tumor with heterogeneous phenotypes. While low stage tumors carry favorable prognosis, over 50% of high risk NB relapses after treatment with fatal outcome. Thus, developing therapies targeting this refractory form of NB remains an unsolved clinical problem. Neuropeptide Y (NPY) is a sympathetic neurotransmitter released from NB cells. High systemic levels of NPY are associated with poor clinical outcome of the disease, which is in agreement with its proliferative effect in NB cells and angiogenic properties. While all of the above functions of NPY are mediated mainly by its Y2 receptor (Y2R), predominantly expressed in NB and endothelial cells, some NB cell lines additionally express NPY Y5R. The goal of our study was to elucidate functions of Y5R/NPY pathway in NB. We have shown that, in contrast to the constitutively expressed Y2R, expression of Y5R was induced in pro-apoptotic conditions, such as serum deprivation, hypoxia or lack of attachment. Under such cellular stress, blocking Y5R by its selective antagonist or siRNA augmented NB cell death, suggesting pro-survival activity of Y5R/NPY axis. This effect was associated with a decrease in activity of p44/42 MAPK, a known mediator of NPY neuroprotective actions. This anti-apoptotic activity of Y5R contributed to chemoresistance of NB cells. Expression of Y5R and NPY was significantly increased in NB cells treated in vitro with chemotherapy. This effect was more pronounced in cells derived from relapsing tumors of patients that were previously treated with chemotherapy, suggesting pre-activation of the pathways inducing Y5R/NPY expression in these cells. Additionally, these refractory NB cell lines had elevated basal levels of Y5R and NPY expression, as compared to corresponding cell lines derived from the same patients at diagnosis. In line with this observation, 100% of surviving NB cells in tissues derived from chemotherapy-treated NB tumors was highly positive for Y5R, while in non-treated tumors only single, isolated Y5R-positive cells were observed. Blocking Y5R in chemoresistant NB cells rich in this receptor sensitized them to chemotherapy-induced apoptosis, as shown by a decrease in the number of viable cells and increase in caspase 3/7 activity. Consequently, Y5R significantly inhibited growth of NB xenografts derived from chemoresistant NB cells, which was associated with a 4-fold increase in cell death, while no significant changes in the levels of NB cell proliferation and tumor vascularization was observed. In summary, Y5R/NPY axis is an inducible pro-survival pathway activated in NB under cellular stress. This Y5R-mediated anti-apoptotic effect contributes to NB chemoresistance, implicating this receptor as a novel therapeutic target for patients with refractory NB, thus far lacking adequate treatment.
Citation Format: Emily Trinh, Magdalena Czarnecka, Sung-Hyeok Hong, Congyi Lu, Samantha Martin, Susana Galli, Ewa Izycka-Swieszewska, Anna Kuan-Celarier, David Christian, Meredith Horton, Jason U. Tilan, Joanna B. Kitlinska. Neuropeptide Y Y5 receptor in neuroblastoma chemoresistance. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3105. doi:10.1158/1538-7445.AM2014-3105