Cyclooxygenase-2 and thromboxane synthase in non-endocrine and endocrine tumors: a review.

Prostaglandins (PG) are members of a large group of hormonally active fatty acids derived from free fatty acids. They are formed from arachidonic acid—the major PG precursor. Cyclooxygenase (COX)-1 and -2 are the rate-limiting steps in PG synthesis. COX-2 is overexpressed in many human non-endocrine and endocrine tumors including colon, breast, prostate, brain, thyroid, and pituitary. COX-2 has an important role in angiogenesis and tumor growth. Thromboxane synthase (TS) catalyzes the synthesis of thromboxane A2 (TXA2), which is derived from arachidonic acid and prostaglandin H2 and is a vasoconstrictor and inducer of platelet aggregation. TXA2 stimulates tumor growth and spread of some tumors and TS appears to have a critical role in tumorigenesis in some organ systems.