First, we performed reverse transcription-quantitative polymerase chain reaction (RT-qPCR) to examine the mRNA expression levels of mPGES-1 (encoded by PTGES) and PGE2 receptors (EP1–4, encoded by PTGER1–4) in the nasal polyps of ECRS or non-ECRS patients. Here, PTGER1 is linked to Nasal polyposis.