Investigation of the effect of CD9 on endometrial cancer cell invasion

最近，我们报道了CD9可能通过调节整合素功能参与滋养层样绒毛膜癌细胞系BeWo的侵袭。本研究采用免疫组化方法研究了月经周期中子宫内膜是否表达CD9。发现CD9在整个月经周期的腺上皮细胞表面上强烈表达，染色强度没有任何明显差异。免疫印迹分析证实，CD9与整合素β 1、α 3和α 6在人子宫内膜中存在相关性。CD9在子宫内膜增生过长的上皮细胞中呈阳性表达，而在子宫内膜腺癌中表达减弱。为了阐明CD9表达降低在子宫内膜癌中的意义，使用体外侵袭测定系统来评估抗CD9单克隆抗体对子宫内膜癌细胞系的侵袭特性的影响。抗CD9单克隆抗体可显著增强RL95 - 2和石川细胞系的侵袭能力，但不影响细胞增殖。由于CD9与人子宫内膜中的整合素β 1、α 3和α 6相关，我们研究了CD9与子宫内膜癌细胞系RL 95 - 2中这些整合素之间的功能关系。抗整合素β 1、α 3和α 6单克隆抗体可抑制RL 95 - 2细胞的侵袭。抗整合素α 3单克隆抗体处理RL 95 - 2细胞后，抗CD9单克隆抗体对RL 95 - 2细胞的侵袭也有促进作用。相反，当用整合素α 6和β 1的单克隆抗体处理时，它没有效果。这些结果表明，CD9是深入参与子宫内膜癌细胞系的侵袭特性。这种参与部分由整合素α 6和β 1介导，这表明CD9可能参与预防子宫内膜癌侵袭。

Recently we reported that CD9 is involved in the invasion of a trophoblast-like choriocarcinoma cell line, BeWo, probably through the regulation of integrin functions. This study investigated immunohistochemically whether CD9 is expressed in the endometrium during the menstrual cycle. CD9 was found to be intensely expressed on the cell surface of the glandular epithelium throughout the menstrual cycle without any apparent differences in staining intensity. In addition, western blotting analysis of the affinity-purified proteins confirmed that CD9 was associated with integrin β1, α3 and α6 in the human endometrium. Next, the expression of CD9 examined showed positive expression on the epithelial cells of endometrial hyperplasia, but reduced expression in endometrial adenocarcinomas. In order to clarify the significance of the reduced CD9 expression in endometrial cancer, an in vitro invasion assay system was used to assess the effect of anti-CD9 monoclonal antibody on the invasive properties of endometrial cancer cell lines. Anti-CD9 monoclonal antibody significantly enhanced invasion of RL95-2 and Ishikawa cell line without affecting cell proliferation. Since CD9 is associated with integrins βl, α3 and α6 in human endometrium, we investigated the functional relationship between CD9 and these integrins in endometrial cancer cell line RL 95-2. Monoclonal antibodies against the integrins β1, α3 and α6 inhibited RL 95-2 cell invasion. Anti-CD9 monoclonal antibody also showed a stimulatory effect on RL 95-2 cell invasion when treated with anti-integrin α3 monoclonal antibody. In contrast, it had no effect when treated with the monoclonal antibodies for integrin α6 and βl. These findings indicate that CD9 is deeply involved in the invasive properties of endometrial carcinoma cell line. This involvement is partially mediated by integrin α6 and β1, which suggests the possible involvement Of CD9 in the prevention of endometrial cancer invasion.