Response of Walker 256 carcinosarcoma cells to 12-O-tetradecanoylphorbol 13-acetate: possible regulation by endogenous cyclooxygenase metabolites.

Walker 256 carcinosarcoma cells (Walker cells) maintained in suspension culture responded to stimulation with 12-O-tetradecanoylphorbol 13-acetate [(TPA) CAS: 16561-29-8] by becoming temporarily adherent to the substratum. Both the control and treated cells produced very low levels of cyclooxygenase metabolites as detected by radioimmunoassay procedures. Levels of prostaglandin F2 alpha, 6-keto prostaglandin F1 alpha (6-keto PGF1 alpha) (a prostacyclin metabolite), and thromboxane B2 were virtually the same as background, and prostaglandin E2 (PGE2) levels were only slightly higher. Studies employing high-performance liquid chromatography also failed to detect significant quantities of cyclooxygenase products in the supernatants from either the control or the stimulated Walker cells. Although the Walker cells maintained in culture failed to produce significant amounts of cyclooxygenase metabolites, they produced much greater amounts of these products, particularly PGE2 and 6-keto PGF1 alpha when they were maintained as an ascites tumor. Concomitant with the production of these metabolites was a loss in responsiveness to TPA in the adherence assay. Upon reestablishment in culture, the cells gradually reacquired the ability to respond to TPA. Over the same period, synthesis of cyclooxygenase products was curtailed. If the cells taken from ascites tumors were incubated with indomethacin so as to inhibit the production of cyclooxygenase metabolites, they rapidly regained responsiveness to TPA. These findings suggest that stimulus-coupled responses in the Walker cells may be regulated, at least in part, through the production of endogenous cyclooxygenase metabolites.