Prostaglandins: Antiproliferative effect of PGD 2 on cultured human glioma cells

Summary Five cultured human glioma cell lines were investigated for their reaction to prostaglandin (PG) D 2 and E 2. In all cases a suppressive effect on DNA synthesis as assessed by³H-thymidine incorporation was seen with all test substances as early as six hours after the addition of the compounds in doses of usually 10^–5 M. A dose response curve was generated in four cases and showed an estimated ED 50 of about 5 · 10^–6 M. The effect was most pronounced at 12 hours after which the cultures began to recover except those which had been incubated with PGD 2. In those cultures which had been exposed to PGD 2 virtually no thymidine incorporation was seen after 24 hours and as long as 72 hours.In another set of experiments, the effect of PGD 2, PGE 2, two synthetic PGD 2 analogues, with a chlorine substitution in position 9 (DACl) or with a fluoride substitution in position 9 (DAF) and a synthetic prostacyclin-analogue (Iloprost) was investigated after single and repeated addition of the compounds. A second administration after 12 hours of incubation did not result in a further decrease in³H-thymidine incorporation like that observed during that first incubation period. In general the cells recovered after 24 hours total incubation time except those which had received PGD 2 or repeated doses of PGE 2. Only in those cells which had been treated with PGD 2, an almost complete blockade of³H-thymidine incorporation was seen even after the single administration. Parallel evaluation of the cells by flow cytometry showed effects on cell cycle distribution at different times of the incubation. After 12 hours cells began to accumulate in G2/M at levels of approximately twice control, the effect being the least pronounced for PGD 2. For this compound we observed a threefold increase in cells in the S phase. After 24 hours the cell cycle distribution had normalized for all compounds except PGD 2 where the arrest of cells in G2/M persisted to be about 2–3-fold control level until the end of the experiment.Our data suggest, that also in cultured human glioma cells, prostaglandins are effective in suppressing cellular DNA synthesis.Although the effect of PGD 2 can be achieved to some extent by PGE 2 and the analogues which are more stable to dehydrogenases and the metabolic conversion into other biologically active homologues, PGD 2 appears to have a unique quality of action, becoming apparent 24 hours after administration.Abbreviations PG prostaglandin - DME Dulbecco's modified Eagle medium - STV trypsin in phosphate buffered saline EDTA (versene) - PBS phosphate buffered saline - ICP impulse cytophotometry - TCA trichloroacetic acid - DACl 9-chloro-15-cyclohexyl-11,15-dihydroxypentanor-5,13-prostadienoic acid- and DAF=9-Fluoro-15-cyclohexyl-11,15-dihydroxypentanor-5,13-prostadienoic acidDedicated to Prof. Dr. Friedrich Loew on the occasion of his 65th birthday and the 25th anniversary of the Homburg Neurosurgical University Clinic, which has been founded and built up by him.