193. RORY+ NEUTROPHILS: A NOVEL THERAPEUTIC TARGET IN GASTRO-ESOPHAGEAL ADENOCARCINOMA

Background

High neutrophil-to-lymphocyte ratio (NLR) is associated with worse oncological outcomes. No current therapies target this emergency myelopoiesis-driven (EM) phenotype. EM, driven by retinoic-acid orphan receptor gamma (RORy), is the phenomenon where cancer cells secrete various factors, skewing normal hematopoiesis towards increased production of pro-tumour RORy+ neutrophils. These neutrophils correlate with advanced stage disease. Additionally, RORy ablation reduces tumour burden in vivo. Our study explores the undescribed roles and therapeutic potential of RORy+ neutrophils in GEA.

Methods: Peripheral blood collected from treatment-naïve GEA patients were lysed and stained for flow cytometry for the following markers: CD66b, CD11b, RORy, interleukin-17 (IL-17) and programmed death-ligand 1 (PD-L1).5x106 YTN16-GFP cells, a murine gastric cancer cell line, were injected in the flank of C57Bl/6 mice. 7 days post-tumour inoculation, 25 mg/kg of a novel experimental RORy inhibitor (Compound #10) was injected subcutaneously on a daily basis till endpoint. Tumour size and circulating NLR were monitored on a weekly basis throughout the experiment. Blood and tumour were also collected at endpoint and stained for flow cytometry.

Results

Our data demonstrate that: Treatment-naïve GEA patients with a high NLR (NLR > 4) have increased prevalence of circulating RORy+ neutrophils compared to low NLR (NLR < 4) GEA patients and healthy volunteers.Circulating RORy+ neutrophils have a higher expression of PD-L1 and IL-17 compared to RORy (−) neutrophils, hinting towards a pro-inflammatory and immunosuppressive phenotype.Anti-RORy treatment in a murine gastric cancer model results in reduced tumour burden and reduced percentage of intratumoural RORy+ neutrophils. Treated mice also exhibited a less immunosuppressive intratumoural microenvironment.

Conclusion

We are the first to associate a high circulating NLR with higher prevalence of circulating RORy+ neutrophils in GEA, thus demonstrating evidence of emergency myelopoiesis in those patients. Additionally, we show that RORy+ neutrophils are a major player in cancer progression. More importantly, these results define a novel therapeutic target that can be utilized to improve patient outcomes, namely GEA patients with a high NLR, a patient subgroup known to have worse outcomes.