High expression of prostaglandin EP4 receptor mRNA in feline head and neck squamous cell carcinoma.

Feline head and neck squamous cell carcinoma (HNSCC) has limited treatment options. Previous studies suggest inflammation, mediated by cyclooxygenase-2 and prostaglandin E2 (PGE2), may play a developmental role. PGE2 signals through 1 of 4 receptors: EP1, EP2, EP3, and EP4. Increased expression of EP4 is associated with the development of multiple human and canine cancers but has not been evaluated in feline neoplasms. The objective of this study was to describe the mRNA expression of the EP4 receptor gene (ptger4) in feline HNSCC compared to normal oral mucosal. Archived HNSCC (n = 18) and normal oral mucosa (n = 20) were evaluated for ptger4 using RNA in-situ hybridization (RNAscope). HALO was used to quantify RNAscope signals. Data were expressed as copy number, H-index, and percent probe positivity. In HNSCC and normal oral mucosa, mRNA of ptger4 was identified. The mRNA expression in HNSCC samples was significantly higher in copy number (P < 0.0001), H-index (P < 0.0001), and percent probe positivity (P < 0.0001) compared to normal oral mucosa. High EP4 receptor expression suggests inflammation may play a role in the development of feline HNSCC. Therapeutically targeting the EP4 receptor with antagonists may add to the current treatment options for this devastating cancer.