Enhanced cell surface CD44 variant (v6, v9) expression by osteopontin in breast cancer epithelial cells facilitates tumor cell migration: Novel post-transcriptional, post-translational regulation
Enhanced cell surface CD44 variant (v6, v9) expression by osteopontin in breast cancer epithelial cells facilitates tumor cell migration: Novel post-transcriptional, post-translational regulation
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DOI：
10.1007/s10585-006-9007-0
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发表时间：
2005-12-01
影响因子：
4
通讯作者：
Denhardt, David T.
中科院分区：
文献类型：
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作者：
Khan, Subarna A.;Cook, Amy C.;Denhardt, David T.
骨桥蛋白（Osteopontin， OPN）是一种糖基化的分泌磷酸化蛋白，具有细胞附着因子和趋化因子的功能。OPN的表达升高使转化细胞的转移能力增强，提示OPN可能促进肿瘤的恶性进展。OPN通过与整合素和CD44细胞表面受体的相互作用刺激乳腺癌细胞的迁移。我们假设OPN调节特异性CD44亚型表达促进乳腺癌细胞迁移。我们检测了21NT致瘤性人乳腺癌细胞系在CMV启动子控制下，在mRNA和蛋白水平上对CD44表达的调控，以响应OPN表达的工程化增加。CD44s异构体mRNA表达显著上调，而CD44v6、v8、v9和v10 mRNA水平无变化。细胞表面CD44s、v6和v9蛋白水平升高，但细胞总蛋白水平仅CD44s和v6显著升高。这表明OPN可以在转录和转录后（蛋白质的数量和定位）水平上调节CD44的表达。为了验证OPN调节CD44表达的功能后果，我们证明暴露于抗pan CD44抗体、抗cd44v6和抗cd44v9功能阻断抗体可以减少OPN介导的细胞迁移。我们的数据提供了证据，证明在21NT细胞中，OPN增强CD44s mRNA的表达，在mRNA水平不变的情况下增加CD44变体形式的细胞表面表达，并刺激细胞迁移。
Osteopontin (OPN) is a glycosylated, secreted phosphoprotein that functions both as a cell attachment and chemotactic factor. Elevated expression of OPN confers enhanced metastatic ability on transformed cells, suggesting that OPN may contribute to the malignant progression of tumors. Migration of mammary carcinoma cells is stimulated by OPN via interactions with integrins and CD44 cell surface receptors. We hypothesized that OPN modulates specific CD44 isoform expression to facilitate breast cancer cell migration. The 21NT tumorigenic human breast cancer cell line was examined for regulation of CD44 expression at both the mRNA and protein levels in response to an engineered increase in OPN expression under CMV promoter control. Significant up-regulation of CD44s isoform mRNA expression was observed, but no change in CD44v6, v8, v9 or v10 mRNA levels. While there were elevated levels of CD44s, v6 and v9 protein at the cell surface, at the level of total cellular protein only CD44s and v6 were markedly increased. This suggests that OPN can regulate CD44 expression at both transcriptional and post-transcriptional (both amount and localization of protein) levels. To validate the functional consequence of OPN regulation of CD44 expression, we demonstrate that OPN-mediated cell migration was reduced by exposure to a anti-pan CD44 antibody, and to anti-CD44v6 and anti-CD44v9 function-blocking antibodies. Our data provide evidence that in 21NT cells OPN enhances CD44s mRNA expression, increases cell surface expression of CD44 variant forms without a change in mRNA levels, and stimulates cell migration.