156 EFFECT OF 2-METHOXYESTRADIOL (2-ME) ON HUMAN UTERINE LEIOMYOSARCOMA

Abstract

2-Methoxyestradiol (2-ME) is an endogenous metabolite of 17β-oestradiol (E2) and has affinity for oestrogen receptors. It was reported as a promising antitumour drug due to antiproliferative activity in many tumour cell types. It has also been used in several preclinical and clinical studies for treatment of solid tumours. Thus, several studies have been conducted to investigate the cytotoxic effect of 2-ME on tumour cell lines in which it induced G₂/M cell cycle arrest and subsequent apoptosis. Uterine leiomyosarcoma is a rare form of malignant smooth muscle cell tumour in the uterus muscle layer. This tumour is also influenced by oestrogen, which acts as a promoter. The purpose of this study was to examine the antiproliferative effect of 2-ME in vitro and in vivo. To perform in vitro experiments, we evaluated the antiproliferative effect of 2-ME on SK-LMS-1 cells using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and Western blot. In vivo experiment also investigated the effect of 2-ME on uterine leiomyoma by measuring tumour size and Western blotting. Employing the mouse xenograft model using human leiomyosarcoma SK-LMS-1 cell line compared with the positive control flavopiridol for 2 weeks, mice were divided into 4 groups (6 mice per each group); VE, 2-ME (75 or 150 mg kg^–1), or flavopiridol (7.5 mg kg^–1). All experimental procedures were performed in triplicate. P-values were calculated using one-way ANOVA, followed by Tukey’s test for multiple comparisons of columns. Data were considered statistically significant at P < 0.05. In vitro, we confirmed that 2-ME at 10^–5 M and flavopiridol have an antiproliferative influence on SK-LMS-1 cells, but the same effect at 10^–7 M or 10^–6 M dose of 2-ME were not detected. These 2 doses showed little proliferative response in the MTT assay. Also, BAX/BCL-2 and LC3 expression were increased by 2-ME (10^–5 M) treatment in Western blot analysis. In the in vivo xenograft study, application of 2-ME (75 mg kg^–1) resulted in an increased tumour size but 150 mg kg^–1 of 2-ME and flavopiridol decreased the size. In a previous study, we found that 2-ME has 2 types of action in an in vitro and an in vivo model. The 2-ME, which is used as a therapeutic agent for solid cancers, has not only apoptotic but also a proliferative effect, depending on the dose. We expect that 2-ME may be a potential therapeutic reagent for human uterine leiomyoma, but the appropriate dose of 2-ME should be used for oestrogen-response tumour treatment.