Abstract 4352: Systemic levels of neuropeptide Y are elevated in Ewing's sarcoma patients
Authors: Tilan Jason U. , Mtaweh Haifa , Everhart Lindsay M. , Long Jessica , Barkauskas Donald A. , Krailo Mark , Jeha Dima , Toretsky Jeffrey , Kitlinska Joanna 
Published: June 2012

Neuropeptide Y (NPY) is a neurotransmitter, which is released from normal sympathetic neurons, as well as tumors of sympathetic origin, such as neuroblastoma and pheochromocytoma. In neuroblastoma patients, the elevated systemic levels of NPY are associated with poor clinical outcome. We have found that, despite their different origin, Ewing's sarcoma cells (ES) also express and release NPY, which can stimulate angiogenesis via its endothelial Y2 receptor (Y2R) and induce apoptosis in ES cells via Y1 and Y5R. These seemingly opposing functions beg the question: Which of these NPY-mediated actions is clinically relevant? Thus, we sought to determine whether release of NPY from ES tumors will result in elevated systemic levels of the peptide and establish the potential correlation of NPY levels with clinical features of this devastating disease.

Analysis of ES cell lines revealed NPY expression at the mRNA level in all investigated cell lines. NPY release (measured by ELISA) into culture media of ES cell lines bearing EWS/FLI type I translocations was not detectable. Interestingly, those bearing type II and III were found at levels comparable to that of sympathetic neuroblastoma. Analysis of serum NPY levels of 248 ES patients with localized disease (collected by Children's Oncology Group under the protocol # AEWS0031) revealed a similar trend in NPY release from tumor tissue. In particular, overall NPY levels were elevated in ES patients versus healthy controls and osteosarcoma patients (p=0.0069), with two distinct groups – ES patients that release NPY similarly to healthy controls and those at significantly higher levels. Furthermore, increased levels of NPY were associated with pelvic tumors (p&lt;0.001), which carry a worse prognosis. The angiogenic properties of NPY are favored with a processing enzyme found to be expressed in ESFT, dipeptidyl peptidase IV (DPPIV), which converts NPY to a Y2R agonist. Thus, we also looked at the DPPIV activity in sera of ES patients and found it to be significantly lower than that of osteosarcoma patients (p=0.0254), but only slightly decreased relative to healthy controls. This suggests that the activity measured in the sera was not derived from tumor-associated DPPIV, but rather the enzyme was shed from other sources, such as immune or endothelial cells. Surprisingly, increased levels of DPPIV activity were found to have a strong predictive value of event free survival. Since DPPIV is known to be involved in immune function, this result may reflect an impaired immune response in ES patients with worse survival.

In summary, this is the first report of elevated NPY levels and the first study on DPPIV activity in ES patients. We have found that NPY release was elevated in pelvic ES tumors, while higher DPPIV activity was associated with better prognosis. However, further study and analysis, such as levels of NPY and DPPIV in ES patients with metastatic disease, is needed to fully clarify the role of NPY in ES patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4352. doi:10.1158/1538-7445.AM2011-4352