Upregulation of thromboxane synthase in human colorectal carcinoma and the cancer cell proliferation by thromboxane A2

Tumor growth of colorectal cancers accompanies upregulation of cyclooxygenase-2, which catalyzes a conversion step from arachidonic acid to prostaglandin H2 (PGH2). Here, we compared the expression levels of thromboxane synthase (TXS), which catalyzes the conversion of PGH2 to thromboxane A2 (TXA2), between human colorectal cancer tissue and its accompanying normal mucosa. It was found that TXS protein was consistently upregulated in the cancer tissues from different patients. TXS was also highly expressed in human colonic cancer cell lines. Depletion of TXS protein by the antisense oligonucleotide inhibited proliferation of the cancer cells. This inhibition was rescued by the direct addition of a stable analogue of TXA2. The present results suggest that overexpression of TXS and subsequent excess production of TXA2 in the cancer cells may be involved in the tumor growth of human colorectum.