Thrombin-cleaved Fragments of Osteopontin Are Overexpressed in Malignant Glial Tumors and Provide a Molecular Niche with Survival Advantage*
Thrombin-cleaved Fragments of Osteopontin Are Overexpressed in Malignant Glial Tumors and Provide a Molecular Niche with Survival Advantage*
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DOI：
10.1074/jbc.m112.362954
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发表时间：
2012-11
期刊：
影响因子：
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通讯作者：
Y. Yamaguchi;Z. Shao;Shadi Sharif;Xiao-Yan Du;T. Myles;M. Merchant;G. Harsh;M. Glantz;L. Recht-L.-Re
中科院分区：
文献类型：
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作者：
Y. Yamaguchi;Z. Shao;Shadi Sharif;Xiao-Yan Du;T. Myles;M. Merchant;G. Harsh;M. Glantz;L. Recht-L.-Re
背景：骨桥蛋白（OPN）在胶质母细胞瘤（GBM）中高度表达，并具有由蛋白水解裂解调节的炎症活性。结果：崩裂后的OPN在GBM中增加，导致GBM细胞黏附增强。OPN赋予GBM细胞抗凋亡能力。结论：骨桥蛋白水解水平的提高增加了GBM细胞对凋亡的抵抗。意义：OPN的裂解连接凝血和炎症，为GBM的发展提供了有利的生态位。骨桥蛋白（OPN）在恶性胶质母细胞瘤（GBM）中高度表达，其炎症活性受凝血酶和血浆羧肽酶B2 （CPB2）在高度保守的裂解位点的蛋白水解裂解所调节。与非癌症患者相比，所有癌症患者脑脊液（CSF）样本中的全长OPN （OPN- fl）均升高。然而，与系统性癌症和非癌症患者相比，GBM和非GBM胶质瘤中凝血酶-cleaved OPN （OPN- r）和凝血酶/ cpb2 -双cleaved OPN （OPN- l）水平明显升高。在GBM和非GBM脑脊液样本中，断裂的OPN分别占总OPN的23%和31%。OPN-R在GBM组织中也升高。凝血酶-抗凝血酶水平与断裂的OPN高度相关，但与OPN- fl无关，这表明断裂的OPN片段是由细胞外腔室中凝血酶和CPB2的增加引起的。GBM患者脑脊液中VEGF、CCL4水平升高，且与cleaved OPN水平相关。与OPN-FL相比，GBM细胞株对OPN-R和OPN-L的粘附性更强。与OPN的粘附改变了基因的表达，特别是与细胞过程、细胞周期调节、死亡和炎症有关的基因。OPN及其裂解形式促进了U-87 MG细胞的运动，并赋予其抗凋亡能力。虽然OPN中RGD基序的功能突变在很大程度上取消了这些功能，但OPNRAA-R恢复了显著的细胞结合和信号功能，这表明如果RGD基序无法获得，OPN- r中的SVVYGLR基序可能替代RGD基序。OPN切割通过允许更多的细胞结合在小生境中获得抗凋亡特性，从而有助于GBM的发展。
Background: Osteopontin (OPN) is highly expressed in glioblastoma (GBM) and possesses inflammatory activity modulated by proteolytic cleavage. Results: Cleaved OPN was increased in GBM and led to more adhesion of GBM cells. OPN conferred resistance to apoptosis in GBM cells. Conclusion: Increased osteopontin proteolysis increased GBM cell resistance to apoptosis. Significance: OPN cleavage links coagulation and inflammation providing a favorable niche for GBM development. Osteopontin (OPN), which is highly expressed in malignant glioblastoma (GBM), possesses inflammatory activity modulated by proteolytic cleavage by thrombin and plasma carboxypeptidase B2 (CPB2) at a highly conserved cleavage site. Full-length OPN (OPN-FL) was elevated in cerebrospinal fluid (CSF) samples from all cancer patients compared with noncancer patients. However, thrombin-cleaved OPN (OPN-R) and thrombin/CPB2-double-cleaved OPN (OPN-L) levels were markedly increased in GBM and non-GBM gliomas compared with systemic cancer and noncancer patients. Cleaved OPN constituted ∼23 and ∼31% of the total OPN in the GBM and non-GBM CSF samples, respectively. OPN-R was also elevated in GBM tissues. Thrombin-antithrombin levels were highly correlated with cleaved OPN, but not OPN-FL, suggesting that the cleaved OPN fragments resulted from increased thrombin and CPB2 in this extracellular compartment. Levels of VEGF and CCL4 were increased in CSF of GBM and correlated with the levels of cleaved OPN. GBM cell lines were more adherent to OPN-R and OPN-L than OPN-FL. Adhesion to OPN altered gene expression, in particular genes involved with cellular processes, cell cycle regulation, death, and inflammation. OPN and its cleaved forms promoted motility of U-87 MG cells and conferred resistance to apoptosis. Although functional mutation of the RGD motif in OPN largely abolished these functions, OPNRAA-R regained significant cell binding and signaling function, suggesting that the SVVYGLR motif in OPN-R may substitute for the RGD motif if the latter becomes inaccessible. OPN cleavage contributes to GBM development by allowing more cells to bind in niches where they acquire anti-apoptotic properties.