Angiogenesis and Tumor Growth

肿瘤的生存、生长和扩散依赖于新生血管、现有血管的选择和干细胞向内皮细胞分化所保证的充足的血液供应。因此，血管生成抑制剂可能是治疗癌症的新工具。我们观察到ebv永生化细胞的上清液通常含有内皮细胞增殖抑制剂。我们从淋巴母细胞VDS-O细胞系的上清液中纯化了一种内皮细胞抑制剂，并将其鉴定为钙网蛋白nh2末端片段的混合物。重组纯化的钙网蛋白nh2末端片段（氨基酸1-180）对内皮细胞的增殖有抑制作用，但对其他细胞系细胞的增殖无抑制作用，并抑制体内血管生成。我们将钙网蛋白的nh2末端结构域命名为血管抑素。当注射到胸腺小鼠体内时，血管抑素可以抑制伯基特淋巴瘤、结肠癌、乳腺腺癌、黑色素瘤、横纹肌肉瘤、肺腺癌和肾母细胞瘤的生长。与血管抑素相比，全长钙网蛋白、缺乏NH2末端1-120个氨基酸的钙网蛋白和包含120-180个氨基酸的钙网蛋白片段在体内抑制内皮细胞增殖、血管生成和肿瘤生长。这些结果表明，血管抑素的抗血管生成和抗肿瘤活性存在于钙网蛋白全长分子可接近的结构域，并定位于钙网蛋白NH2结构域内的61个氨基酸片段。因此，我们已经确定钙调蛋白和血管抑素是抑制临床前肿瘤模型中肿瘤生长的新型血管生成抑制剂。

Survival, growth and spread of tumors depend upon an adequate blood supply ensured by neovascularization, cooption of existing vessels and stem cell differentiation into endothelial cells. Thus, inhibitors of angiogenesis may represent novel tools for the treatment of cancer. We observed that supernatants of EBV-immortalized cell generally contain inhibitors of endothelial cells proliferation. From supernatants of the lymphoblastic VDS-O cell line we purified an endothelial cell inhibitor, and identified it as a mixture of NH2-terminal fragments of calreticulin. The recombinant purified NH2-terminal fragments of calreticulin (amino acids 1-180) inhibited the proliferation of endothelial cells but not the proliferation of cells of other lineages, and suppressed angiogenesis in vivo. We have named this NH2-terminal domain of calreticulin vasostatin. When inoculated into athymic mice, vasostatin reduced growth of Burkitt lymphoma, colon carcinoma, breast adenocarcinoma, melanoma, rhabdomyosarcoma, lung adenocarcinoma and Wilms tumors. Full-length calreticulin, calreticulin lacking the NH2 terminal 1-120 amino acids, and an internal calreticulin fragment encompassing amino acids 120-180 inhibited endothelial cell proliferation, angiogenesis, and tumor growth in vivo comparably to vasostatin. These results suggest that the antiangiogenic and antitumor activities of vasostatin reside in a domain that is accessible from the full-length calreticulin molecule and localized to an internal 61 amino acids fragment within the NH2 domain of calreticulin. Thus, we have identified calreticulin and vasostatin as novel angiogenesis inhibitors that suppress tumor growth in preclinical tumor models.