# Targeting Neuropeptide Y/DPP4 Signalling Suppresses Ewing Sarcoma Survival and Improves Monocyte Viability

## TL;DR

This study shows that blocking the NPY/DPP4 signaling pathway can reduce Ewing sarcoma survival and improve monocyte function, offering a potential new treatment strategy.

## Contribution

The study identifies NPY/DPP4 signaling as a novel therapeutic target for Ewing sarcoma by linking it to tumor survival and immune cell function.

## Key findings

- NPY and DPP4 promote Ewing sarcoma survival through autocrine/paracrine signaling.
- DPP4 inhibitor linagliptin suppresses Ewing sarcoma viability, especially under hypoxia.
- NPY and DPP4 reduce monocyte viability, suggesting a role in immune suppression.

## Abstract

Survival rates for metastatic Ewing sarcoma (EwS) have remained persistently low over recent decades, highlighting the need for more effective chemotherapeutic options. Potential targets may be found within the Neuropeptide Y (NPY) signalling pathway that has been implicated in EwS cell survival. However, confounding factors include hypoxia that modulates NPY signalling, dipeptidyl peptidase-4 (DPP4/CD26) that cleaves NPY and interactions via NPY signalling from infiltrating immune cells. We investigated these interactions in A673 and SK-ES-1 EwS cell lines and THP-1 monocytes to identify therapeutic targets suitable for drug repurposing. Both EwS cell lines secreted NPY into conditioned media and extracellular vesicles. Recombinant NPY enhanced viability of both A673 and SK-ES-1 cells; however, the NPY1R antagonist BMS-193885 reduced viability in A673 cells only. Recombinant DPP4 widely promoted EwS viability and, under hypoxic conditions, it increased cell metabolism. The DPP4 inhibitor linagliptin, which is used clinically, consistently suppressed EwS viability with elevated sensitivity under hypoxia, where there was increased cell death of SK-ES-1 cells. Conversely, in THP-1 monocytes, NPY suppressed metabolism, BMS-193885 increased live-cell staining and DPP4 induced cell death. These findings suggest that NPY and DPP4 enhance EwS survival through autocrine/paracrine signalling while reducing monocyte viability. Thus, targeting the NPY/DPP4 signalling axis may provide therapeutic benefit by directly suppressing EwS growth and enhancing efficacy of immunotherapy.