Ghigo D, Arese M, Todde R, Vecchi A, Silvagno F, Costamagna C, Dong Q G, Alessio M, Heller R, Soldi R, Trucco F, Garbarino G, Pescarmona G, Mantovani A, Bussolino F, Bosia A
Department of Genetics, Biology and Medical Chemistry, University of Torino, Italy.
J Exp Med. 1995 Jan 1;181(1):9-19. doi: 10.1084/jem.181.1.9.
Endothelioma cell lines transformed by polyoma virus middle T antigen (mTa) cause cavernous hemangiomas in syngeneic mice by recruitment of host cells. The production of nitric oxide (NO), as measured by nitrite and citrulline production, was significantly higher in mTa-transformed endothelial cells in comparison with nontransformed control cells. The maximal activity of NO synthase (NOS) was about 200-fold higher in cell lysates from the tEnd.1 endothelioma cell line than in lysates from nontransformed controls, whereas the affinity for arginine did not differ. The biochemical characterization of NOS and the study of mRNA transcripts indicate that tEnd.1 cells express both the inducible and the constitutive isoforms. NOS hyperactivity is not a simple consequence of cell transformation but needs a tissue-specific mTa expression. Since tEnd.1-conditioned medium induces NOS activity in normal endothelial cells, most likely NOS hyperactivity in endothelioma cells is attributable to the release of a soluble factor. This NOS-activating factor, which seems to be an anionic protein, could stimulate tEnd.1 cells to express NOS by an autocrine way. By the same mechanism, tEnd.1 cells could induce NOS in the neighboring endothelial cells, and NO release could play a role in the hemangioma development. Such hypothesis is confirmed by our in vivo experiments, showing that the administration of the NOS inhibitor L-canavanine to endothelioma-bearing mice significantly reduced both the volume and the relapse time of the tumor.
由多瘤病毒中T抗原（mTa）转化的内皮瘤细胞系通过募集宿主细胞在同基因小鼠中引发海绵状血管瘤。通过亚硝酸盐和瓜氨酸生成量测定的一氧化氮（NO）产量，与未转化的对照细胞相比，在mTa转化的内皮细胞中显著更高。tEnd.1内皮瘤细胞系的细胞裂解物中一氧化氮合酶（NOS）的最大活性比未转化对照的裂解物高约200倍，而对精氨酸的亲和力没有差异。NOS的生化特性及mRNA转录本研究表明，tEnd.1细胞同时表达诱导型和组成型同工型。NOS活性过高不是细胞转化的简单结果，而是需要组织特异性的mTa表达。由于tEnd.1条件培养基可诱导正常内皮细胞中的NOS活性，内皮瘤细胞中NOS活性过高很可能归因于一种可溶性因子的释放。这种NOS激活因子似乎是一种阴离子蛋白，可能通过自分泌方式刺激tEnd.1细胞表达NOS。通过相同机制，tEnd.1细胞可诱导相邻内皮细胞中的NOS，且NO释放可能在血管瘤发展中起作用。我们的体内实验证实了这一假设，即给携带内皮瘤的小鼠施用NOS抑制剂L-刀豆氨酸可显著减小肿瘤体积并延长肿瘤复发时间。
