On the basis of an in vitro study, PGE2 upregulates ACE2 and TMPRSS2 in human gingival fibroblasts [29], an outcome that should also be appraised in the case of lung epithelial cells given that an increased concentration of PGE2 was found in the urine samples of COVID-19 patients, indicating generally higher levels of this cytokine in their circulation [55]. This evidence concerns the gene TMPRSS2 and COVID-19.