Investigation of the effect of CD9 on endometrial cancer cell invasion

最近我们报道CD9参与了滋养层细胞样绒癌细胞系BeWo的侵袭，可能是通过对整合素功能的调节。本研究采用免疫组织化学方法研究CD9在月经周期子宫内膜中的表达。CD9在整个月经周期中腺上皮细胞表面均有强烈表达，但染色强度无明显差异。此外，Western blotting分析证实CD9与人子宫内膜中的整合素β1、α3和α6相关。其次，CD9在子宫内膜增生症的上皮细胞中呈阳性表达，而在子宫内膜腺癌中的表达减弱。为明确CD9在子宫内膜癌中表达下调的意义，采用体外侵袭实验系统检测抗CD9单抗对子宫内膜癌细胞系侵袭特性的影响。抗CD9单抗可显著增强RL95-2和Ishikawa细胞的侵袭力，但不影响细胞增殖。鉴于CD9在人子宫内膜中与整合素βL、α3和α6相关，我们研究了CD9与这些整合素在子宫内膜癌细胞株RL 95-2中的功能关系。抗整合素β1、α3和α6的单抗可抑制RL 95 2细胞的侵袭。抗整合素α-3单抗对RL95-2细胞的侵袭也有促进作用。而抗整合素α-6和β-L的单抗对子宫内膜癌细胞的侵袭无明显影响，提示CD9与子宫内膜癌细胞的侵袭特性密切相关。α-6和β-1可能参与了子宫内膜癌侵袭的预防。

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.