Although we propose that differences in 15-PGDH activity in cancer tissue compared with cultured CRC cells may account for the contrasting relationship between 15-PGDH expression and PGE2 levels in CRCLM tissue versus cell-conditioned medium, we cannot completely rule out that inadvertent stimulation of PGE2 synthesis ex vivo occurred. The gene discussed is HPGD; the disease is colorectal carcinoma.