HPGD and colorectal carcinoma: Given the counter-intuitive observation that PGE2 levels were higher in the central area of CRCLM, in which expression of the main catabolic enzyme 15-PGDH was elevated, we performed a series of experiments, which were designed to investigate the relationship between 15-PGDH expression and levels of PGE2 in cell-conditioned medium, using HCA-7 human CRC cells, which constitutively express high levels of COX-2 and release large quantities of PGE2 into cell culture medium [28].