15-hydroxyprostaglandin dehydrogenase is down-regulated in colorectal cancer

Prostaglandin E₂ (PGE₂) can stimulate tumor progression by modulating several proneoplastic pathways, including proliferation, angiogenesis, cell migration, invasion, and apoptosis. Although steady-state tissue levels of PGE₂ stem from relative rates of biosynthesis and breakdown, most reports examining PGE₂ have focused solely on the cyclooxygenase-dependent formation of this bioactive lipid. Enzymatic degradation of PGE₂ involves the NAD⁺-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH). The present study examined a range of normal tissues in the human and mouse and found high levels of 15-PGDH in the large intestine. By contrast, the expression of 15-PGDH is decreased in several colorectal carcinoma cell lines and in other human malignancies such as breast and lung carcinomas. Consistent with these findings, we observe diminished 15-Pgdh expression in Apc^Min+/- mouse adenomas. Enzymatic activity of 15-PGDH correlates with expression levels and the genetic disruption of 15-Pgdh completely blocks production of the urinary PGE₂ metabolite. Finally, 15-PGDH expression and activity are significantly down-regulated in human colorectal carcinomas relative to matched normal tissue. In summary, these results suggest a novel tumor suppressive role for 15-PGDH due to loss of expression during colorectal tumor progression.