Yamahata Hitoshi, Takeshima Hideo, Kuratsu Jun-Ichi, Sarker Krishna Pada, Tanioka Koji, Wakimaru Naruhito, Nakata Masanori, Kitajima Isao, Maruyama Ikuro
Department of Neurosurgery, Faculty of Medicine, Kagoshima University, Japan.
Int J Oncol. 2002 May;20(5):921-8.
Thrombin is a key enzyme in the blood coagulation system where it converts fibrinogen to fibrin. It participates in a variety of biological processes such as the induction of mitogenesis and of morphological changes, the production of cytokines and growth factors, and apoptosis. To clarify the role of thrombin in the proliferation of human malignant gliomas, we investigated its effect on the expression of vascular endothelial growth factor (VEGF) in vitro and determined its intrinsic expression in human glioma tissues. In 3 human glioma cell lines tested, U-87 MG, U-251 MG, and U-105 MG, thrombin induced the VEGF mRNA expression and protein in a dose- and time-dependent manner. The thrombin receptor expression was detectable by RT-PCR and immunoblot. The secretion of VEGF protein in glioma cells was stimulated by the thrombin receptor agonist peptide and the induction of VEGF was significantly blocked by the thrombin inhibitor hirudin, indicating that the up-regulation of VEGF was mediated by the thrombin/thrombin receptor pathway. Immunoblot analysis demonstrated that prothrombin, the precursor of thrombin, was distributed in all 10 glioma tissues examined. In situ hybridization and immunohistochemical analysis revealed the co-localization of prothrombin mRNA-positive and GFAP-positive cells in the glioma tissues. Although various factors may be involved in the up-regulation of VEGF, our results suggest that human gliomas per se express prothrombin, and that thrombin, converted from prothrombin in glioma tissues, substantially stimulates angiogenesis in an autocrine fashion.
凝血酶是血液凝固系统中的关键酶，它可将纤维蛋白原转化为纤维蛋白。它参与多种生物学过程，如诱导有丝分裂和形态变化、细胞因子和生长因子的产生以及细胞凋亡。为了阐明凝血酶在人类恶性胶质瘤增殖中的作用，我们在体外研究了其对血管内皮生长因子（VEGF）表达的影响，并测定了其在人类胶质瘤组织中的内在表达。在测试的3种人类胶质瘤细胞系U-87 MG、U-251 MG和U-105 MG中，凝血酶以剂量和时间依赖性方式诱导VEGF mRNA表达和蛋白表达。通过RT-PCR和免疫印迹可检测到凝血酶受体表达。凝血酶受体激动剂肽刺激胶质瘤细胞中VEGF蛋白的分泌，凝血酶抑制剂水蛭素显著阻断VEGF的诱导，表明VEGF的上调是由凝血酶/凝血酶受体途径介导的。免疫印迹分析表明，凝血酶的前体凝血酶原分布在所检测的所有10个胶质瘤组织中。原位杂交和免疫组化分析显示，胶质瘤组织中凝血酶原mRNA阳性细胞和GFAP阳性细胞共定位。尽管VEGF的上调可能涉及多种因素，但我们的结果表明，人类胶质瘤本身表达凝血酶原，并且在胶质瘤组织中由凝血酶原转化而来的凝血酶以自分泌方式大量刺激血管生成。
