Department of Animal and Human Biology, University of Torino, Torino, Italy.
Oncogene. 2012 Jan 12;31(2):200-12. doi: 10.1038/onc.2011.231. Epub 2011 Jun 20.
Changes in intracellular calcium Ca(2+) levels control critical cytosolic and nuclear events that are involved in the initiation and progression of tumor angiogenesis in endothelial cells (ECs). Therefore, the mechanism(s) involved in agonist-induced Ca(2+)(i) signaling is a potentially important molecular target for controlling angiogenesis and tumor growth. Several studies have shown that blood vessels in tumors differ from normal vessels in their morphology, blood flow and permeability. We had previously reported a key role for arachidonic acid (AA)-mediated Ca(2+) entry in the initial stages of tumor angiogenesis in vitro. In this study we assessed the mechanism involved in AA-induced EC migration. We report that TRPV4, an AA-activated channel, is differentially expressed in EC derived from human breast carcinomas (BTEC) as compared with 'normal' EC (HMVEC). BTEC display a significant increase in TRPV4 expression, which was correlated with greater Ca(2+) entry, induced by AA or 4αPDD (a selective TRPV4 agonist) in the tumor-derived ECs. Wound-healing assays revealed a key role of TRPV4 in regulating cell migration of BTEC but not HMVEC. Knockdown of TRPV4 expression completely abolished AA-induced BTEC migration, suggesting that TRPV4 mediates the pro-angiogenic effects promoted by AA. Furthermore, pre-incubation of BTEC with AA induced actin remodeling and a subsequent increase in the surface expression of TRPV4. This was consistent with the increased plasma membrane localization of TRPV4 and higher AA-stimulated Ca(2+) entry in the migrating cells. Together, the data presented herein demonstrate that: (1) TRPV4 is differentially expressed in tumor-derived versus 'normal' EC; (2) TRPV4 has a critical role in the migration of tumor-derived but not 'normal' EC migration; and (3) AA induces actin remodeling in BTEC, resulting in a corresponding increase of TRPV4 expression in the plasma membrane. We suggest that the latter is critical for migration of EC and thus in promoting angiogenesis and tumor growth.
细胞内钙离子 (Ca(2+)) 水平的变化控制着内皮细胞 (EC) 中肿瘤血管生成起始和进展所涉及的关键细胞质和核事件。因此，激动剂诱导的 Ca(2+) 信号转导所涉及的机制是控制血管生成和肿瘤生长的潜在重要分子靶点。几项研究表明，肿瘤中的血管在形态、血流和通透性方面与正常血管不同。我们之前曾报道过花生四烯酸 (AA) 介导的 Ca(2+) 内流在体外肿瘤血管生成的初始阶段中起着关键作用。在这项研究中，我们评估了 AA 诱导的 EC 迁移所涉及的机制。我们报告说，TRPV4 是一种由 AA 激活的通道，在源自人类乳腺癌 (BTEC) 的 EC 中与“正常” EC (HMVEC) 相比差异表达。BTEC 显示 TRPV4 表达显著增加，这与肿瘤衍生 EC 中 AA 或 4αPDD（一种选择性 TRPV4 激动剂）诱导的 Ca(2+) 内流增加相关。划痕愈合试验表明 TRPV4 在调节 BTEC 细胞迁移中起着关键作用，但对 HMVEC 没有作用。TRPV4 表达的敲低完全消除了 AA 诱导的 BTEC 迁移，表明 TRPV4 介导了 AA 促进的促血管生成作用。此外，BTEC 用 AA 预孵育诱导肌动蛋白重塑，并随后增加 TRPV4 的表面表达。这与迁移细胞中 TRPV4 的质膜定位增加和 AA 刺激的 Ca(2+) 内流增加一致。总之，本文提供的资料表明：(1) TRPV4 在源自肿瘤的 EC 与“正常” EC 之间差异表达；(2) TRPV4 在源自肿瘤的但不是“正常” EC 的迁移中发挥关键作用；(3) AA 在 BTEC 中诱导肌动蛋白重塑，导致质膜中 TRPV4 表达相应增加。我们认为后者对于 EC 的迁移至关重要，从而促进血管生成和肿瘤生长。
