We previously reported that mouse mammary carcinoma cell lines (MMT060562 and BALB/c‐MC) induced osteoclast formation through production of prostaglandin E2 (PGE2) in cocultures with mouse bone marrow cells, but the mechanism(s) of PG production remained unclear. In the present in vitro and in vivo studies, we tested the involvement of cyclo‐oxygenase‐2 (COX‐2), an inducible rate‐limiting enzyme in PG biosynthesis, in the stimulation of osteoclast formation by mouse mammary carcinoma cell lines. Addition of a selective COX‐2 inhibitor, JTE‐522, to cocultures of mammary carcinoma cell lines and bone marrow cells lowered PGE2 concentration in the culture media and inhibited osteoclast formation in a dose‐dependent manner. Northern blotting showed a very high level of COX‐2 messenger RNA (mRNA) expression in MMT060562. The mRNA expression was low in BALB/c‐MC, but it increased when BALB/c‐MC and bone marrow cells were cocultured. The results of immunocytochemistry for COX‐2 protein in respective cultures were compatible with the results of COX‐2 mRNA. In vivo, BALB/c‐MC injected into the heart of Balb/c mice metastasized to bone and formed osteolytic lesions in their hindlimbs. Histological examination revealed that tumor cells had metastasized to the bone marrow cavity and destroyed the bone trabeculae. Immunohistochemistry demonstrated that bone marrow stromal cells adjacent to tumor cells expressed COX‐2 protein. These findings suggest that COX‐2 plays an important role in the osteolysis of bone metastasis in vivo as well as in osteoclast formation in cocultures used as an in vitro model of metastatic bone disease.
我们以前曾报道过小鼠乳腺癌
细胞系(MMT060562 和 BALB/c-MC)在与小鼠骨髓细胞共培养时通过产生
前列腺素 E2(
PGE2)诱导破骨细胞形成,但
PG 的产生机制仍不清楚。在目前的体外和体内研究中,我们检测了环氧化酶-2(COX-2)参与刺激小鼠乳腺癌
细胞系破骨细胞形成的情况,环氧化酶-2 是
PG 生物合成过程中的一种诱导性限速酶。在乳腺癌
细胞系和骨髓细胞的共培养物中加入一种选择性 COX-2
抑制剂 JTE-522,可降低
培养基中
PGE2 的浓度,并以剂量依赖的方式抑制破骨细胞的形成。Northern 印迹显示,MMT060562 中 COX-2 信使 RNA (mRNA) 的表达
水平非常高。在 BALB/c-MC 中,mRNA 的表达量较低,但当 BALB/c-MC 与骨髓细胞共培养时,mRNA 的表达量有所增加。各培养物中 COX-2 蛋白的免疫细胞
化学结果与 COX-2 mRNA 的结果一致。在体内,注入 BAlb/c 小鼠心脏的 BALB/c-MC 转移到骨,并在其后肢形成溶骨病变。组织学检查显示,肿瘤细胞已转移到骨髓腔,并破坏了骨小梁。免疫组化显示,肿瘤细胞附近的骨髓基质细胞表达 COX-2 蛋白。这些发现表明,COX-2 在体内骨转移的溶骨过程中以及在作为转移性骨病体外模型的
细胞培养物中的破骨细胞形成过程中发挥着重要作用。