Abstract 5822: Increase in protein expression and copy number drives the activation of NPY/Y5R pro-survival loop in chemotherapy-treated neuroblastoma

Abstract

Abstract Neuroblastoma (NB) is a tumor derived from neural crest cells, primitive progenitors of sympathetic ganglia. It accounts for 6-10% of all pediatric cancers with approximately 700 new cases per year throughout the US. Although there are highly effective therapies for patients with low-risk and intermediate-risk disease who have local relapses, recurrent disease in patients with high-risk NB is mostly refractory to therapy. Neuropeptide Y (NPY) is a sympathetic neurotransmitter highly expressed in NB. Its elevated release from tumor tissue is associated with unfavorable clinical outcome. NPY, acting via its Y5 receptor (Y5R), stimulates NB cell survival and chemoresistance, however the mechanisms underlying NPY/Y5R axis activation in these tumors remain unclear. The aim of this work was to investigate the correlation between the expression of NPY and NPY5R proteins and the copy number status of the NPY and NPY5R genes in pre- and post-chemotherapy NB. Eighty-five tissue samples, including specimens from the primary tumors, distant metastases and local relapses, pre- and post-chemotherapy, were collected from the Hospital Pequeno Principe, Parana, Brazil. Protein expression was investigated by immunohistochemistry. Copy number alterations (CNAs) for NPY and NPY5R genes were determined using TaqMan copy number assay. Additionally, FISH analysis was performed to assess MYCN amplification status, a genetic marker of high risk NB. Our results show that elevated extracellular NPY staining, which reflects peptide release, correlates with patients’ age above 18 months, relapse and poor clinical outcome. Moreover, the intensity of NPY staining was increased in chemotherapy-treated NBs, as compared to tumors at diagnosis. However, the differences in NPY CNAs between these samples were not statistically significant. Thus, chemotherapy-induced increase in NPY levels observed in post-treatment NB is driven by its elevated expression rather than genomic changes. For NPY5R, significantly higher level of CNAs was observed in the post-chemotherapy samples (P<0.05), independently of the MYCN status. These findings are in line with previous studies reporting elevated NPY5R expression in chemotherapy-treated NB tumors and cell lines. Therefore, for this receptor genomic changes may play an important role in conferring chemotherapy-driven Y5R up-regulation. Altogether, our results confirm activation of NPY/Y5R pro-survival loop in chemotherapy-treated NB tumors. However, these coordinated increases in the NPY and NPY5R expression levels are driven by different molecular mechanisms. Citation Format: Selene Elifio-Esposito, Akanksha Mahajan, Aline S. Fonseca, Susana Galli, Lucia Noronha, Lisiane C. Poncio, Bonald C. Figueiredo, Joanna B. Kitlinska, Luciane R. Cavalli. Increase in protein expression and copy number drives the activation of NPY/Y5R pro-survival loop in chemotherapy-treated neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5822. doi:10.1158/1538-7445.AM2017-5822