EphB2/R-Ras signaling regulates glioma cell adhesion, growth, and invasion
EphB2/R-Ras signaling regulates glioma cell adhesion, growth, and invasion
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DOI：
10.1016/s0002-9440(10)62998-7
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发表时间：
2005-08-01
影响因子：
6
通讯作者：
Berens, ME
中科院分区：
文献类型：
--
作者：
Nakada, M;Niska, JA;Berens, ME
Eph受体酪氨酸激酶介导神经发育过程，如边界形成、血管生成和细胞迁移。最近，我们发现EphB2在胶质瘤细胞中的过表达导致细胞黏附减少，细胞侵袭增加。由于R-RAS已被证明在EphB2的整合素活性调节中起关键作用，我们探讨了EphB2在胶质瘤侵袭中的生物学作用是否由下游的R-RAS激活所介导。在EphB2激活时，R-RAS与受体结合并高度磷酸化。通过siRNA抑制内源性R-RAS的表达可消除EphB2对体外培养的大鼠脑切片中胶质瘤细胞的黏附、增殖和侵袭的影响。对EphB2激活的抗增殖反应与丝裂原活化蛋白激酶活性被抑制是一致的。此外，R-RAS在侵袭性胶质瘤细胞中高度磷酸化。在人脑肿瘤标本中，R-RAS的表达和磷酸化与胶质瘤的分级有关。对侵袭性胶质母细胞瘤细胞的激光捕获显微切割显示，100%(8/8)的活检标本中R-RAS基因表达升高(1.5~26倍)，免疫组织化学显示R-RAS主要定位于胶质母细胞瘤细胞。胶质母细胞瘤组织中R-RAS的磷酸化率与EphB2的磷酸化率呈正相关。这些结果表明，R-RAS在脑胶质瘤的病理过程中发挥了重要作用，进一步提示EphB2/R-RAS信号通路是一个潜在的治疗靶点。
Eph receptor tyrosine kinases mediate neurodevelopmental processes such as boundary formation, vasculogenesis, and cell migration. Recently, we found that overexpression of EphB2 in glioma cells results in reduced cell adhesion and increased cell invasion. Since R-Ras has been shown to play a critical role in EphB2 regulation of integrin activity, we explored whether the biological role of EphB2 in glioma invasion is mediated by downstream R-Ras activation. On EphB2 activation, R-Ras associated with the receptor and became highly phosphorylated. Depletion of endogenous R-Ras expression by siRNA abrogated EphB2 effects on glioma cell adhesion, proliferation, and invasion in ex vivo rat brain slices. Anti-proliferative responses to EphB2 activation were consistent with suppressed mitogen-activated protein kinase activity. Moreover, R-Ras was highly phosphorylated in the invading glioma cells. In human brain tumor specimens, R-Ras expression and phosphorylation correlated with increasing grade of gliomas. Laser capture microdissection of invading glioblastoma cells revealed elevated R-Ras mRNA (1.5- to 26-fold) in 100% (eight of eight) of biopsy specimens, and immunohistochemistry revealed high R-Ras localization primarily in glioblastoma cells. The phosphorylation ratio of R-Ras positively correlated with the phosphorylation ratio of EphB2 in glioblastoma tissues. These results demonstrate that R-Ras plays an important role in glioma pathology, further suggesting the EphB2/R-Ras signaling pathway as a potential therapeutic target.