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Background: The number of endometrial cancer (EC) cases is escalating rapidly, with no evident improvements in survival rates. The downregulation of progesterone receptor, resulting in progestin resistance, is presently a major problem regarding the therapeutic aspect. On the basis of this, we can focus more on the downstream signaling pathways that are controlled by progesterone. Lipid biosynthesis mediated by sterol regulatory element-binding protein-1/fatty acid synthase (SREBP-1/FASN) is of utmost importance to the growth and the proliferation of EC cells, so we hypothesize that SREBP-1/FASN might be involved in suppressing the proliferation and promoting apoptosis in EC cells through the effects induced by progesterone., Material and Methods: The Cell Counting Kit-8 was used to analyze the growth inhibition ratio of Ishikawa cells upon treatment with megestrol acetate (MA; MA is a progesterone derivative, also known as 17α-acetoxy-6-dehydro-6-methylprogesterone) and to determine the 50% inhibitory concentration. Apoptosis ratio was analyzed by treatment of the cells with MA at 50% inhibitory concentration at different time intervals using Annexin V-FITC/propidium iodide. The protein and messenger RNA levels of SREBP-1 and FASN were compared between the experimental and control groups (MA-treated Ishikawa cells were considered to be the experimental group)., Results: The experimental group showed obvious growth inhibition that was time and concentration dependent. The apoptosis ratio was also significantly higher in the experimental group compared with the control group (P < 0.01). The protein and messenger RNA levels of SREBP-1 and FASN were significantly reduced by MA too., Conclusions: Sterol regulatory element-binding protein-1/FASN is involved in the proliferation suppression and apoptosis promotion brought about by MA in Ishikawa cells.

Objective: To detect the expression change of claudin-4 in Ishikawa endometrial adenocarcinoma cell line in response to progesterone. To determine whether claudin-4 is involved in the anticancer effect of progesterone., Methods: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to determine the 50% inhibitory concentration (IC50) of megestrol acetate (MA) in treating Ishikawa cells. After the Ishikawa cells were treated with MA at IC50, cell apoptosis was examined by flow cytometry and transmission electron microscopy. The messenger RNA and protein expression levels of claudin-4 were further quantified by real-time polymerase chain reaction and Western blot. The localization of claudin-4 was examined by immunofluorescent staining., Results: The IC50 of MA on Ishikawa cells was 15 mg/L incubated for 72 hours. Apoptosis percentage was elevated from 0.07% ± 0.02% to 3.93% ± 0.81% after MA treatment. The expression of claudin-4 at both protein and messenger RNA levels was significantly decreased after the treatment of MA (P < 0.05). The localization of claudin-4 transferred from cytomembrane to cytoplasm and nucleus., Conclusion: Megestrol acetate can inhibit the growth of Ishikawa cells. It may work through decreasing claudin-4 expression and cell apoptosis. The localization change of claudin-4 may also be involved in the anticancer effect of progesterone.