Modulation of prostaglandin biosynthesis in murine mammary adenocarcinoma tumor cells

In efforts to exploit the differential oxygen levels within the subcompartments of solid neoplasms, this project has focused on modulating prostaglandin (PG) biosynthesis under aerobic and hypoxic conditions. Mammary adenocarcinoma tumor cells (Line 4526), either intact or sonicated, were incubated with either 2.0 uM 14C-arachidonic acid (AA) or 20.0 uM 14C-PGH2, respectively. Following metabolism, products were extracted, separated by thin layer chromatography and analyzed by radiochromatographic scan. PGE2 was predominantly formed with minimal amounts of PGF2a or PGD2. Indomethacin and ibuprofen inhibited the PGE2 formation from AA with an IC50 value of 6.3 x 10-8 and 9.6 x 10-5M, respectively. Suspended cells in glass vials were made hypoxic by flushing with N2 for varying time intervals to study AA metabolism. A time-dependent inhibition of PG biosynthesis was observed under hypoxia, and by 30 min, the PGE2 synthesis was reduced by 50% which was further inhibited by indomethacin. Misonidazole, a 2-nitroimidazole analogue, partially reversed the inhibition of PGE2 synthesis under hypoxia by 49% at 100 uM. However, misonidazole did not affect PG biosynthesis under aerobic conditions. The stimulation of PGE2 biosynthesis by misonidazole under hypoxia was blocked by indomethacin, suggesting that misonidazole can not act independently of the cyclooxygenase