PTGS2 and hepatocellular carcinoma: Recently, Loo et al. (2017) reported that the expression of cyclooxygenase 2 (COX-2), a rate limiting enzyme involved in prostaglandin biosynthesis, is increased in senescent hepatic stellate cells and triggers the overproduction of the SASP prostaglandin E2 (PGE2) via PGE2 receptor EP4, limiting anti-tumor immunity in obesity-associated HCC [60].