Chromatin analysis in human endometrial adenocarcinoma before and after treatment with 6-methyl-17-hydroxyprogesterone acetate (MPA)

Effect of Medroxyprogesterone Acetate and of Some Antiinflammatory Agents on Mouse Erythroleukemia Cell Differentiation

The effects of medroxyprogesterone acetate (MPA) on differentiation were examined using mouse erythroleukemia (MEL) cells and compared with those of antiinflammatory agents. MPA at low doses (10−6 - 10−7 M) induced 10–15 % cells to differentiate, whereas high doses (10−4 - 10−5 M) caused a 30 % inhibition of dimethylsulfoxide (DMSO)-induced differentiation. Dexamethasone (10−4 - 10−8 M), a steroid antiinflammatory agent, significantly inhibited (77–70 %) DMSO-induced differentiation, whereas indomethacin, aspirin, flurbiprofen and BW755c (non steroid antiinflammatory agents) at the same concentrations had no effect. If added 24 h before DMSO, the inhibitory effects of MPA and dexamethasone increased to 65 % and 95 %, respectively, whereas indomethacin (10−5 M) caused only a 30 % inhibition and the other drugs were inactive. None of these antiinflammatory agents affected differentiation when used without DMSO. MPA and dexamethasone inhibitory effects on DMSO-induced differentiation did not seem to be mediated through the inhibition of the synthesis of prostaglandins, since non-steroid prostaglandin inhibitors were slighly active only when added 24 h before DMSO.

Two mechanisms of chromatin compaction

2 types of chromatin compaction were studied by cytochemical and ultrastructural approach. The 1st type was induced by cultivating transformed cells with dimethylsulfoxide. It caused cell transition into a more differentiated state coupled with the appearance of multiple small chromatin condensates. The 2nd type was induced by nonionic detergent Triton X-100 and/or saline penetration inside the nuclei. It was found to be connected with hypercompaction of chromocenters with their integral areas left unincreased. Both types of chromatin compaction differ in their capacity to induce toluidine blue polymerization on DNA substrate and in stability of DNA towards an early step of acid hydrolysis. The relation of the 2 mechanisms of chromatin compaction to different ways of DNA folding is discussed.