Angiogenesis and Tumor Growth

肿瘤的存活、生长和扩散依赖于由新生血管、现有血管的共生和干细胞分化为内皮细胞所确保的充足的血液供应。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永生化细胞的培养上清通常含有内皮细胞增殖的抑制物。从淋巴母细胞系VDS-O细胞培养上清液中纯化了一种内皮细胞抑制物，并鉴定其为钙网蛋白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)抑制内皮细胞的增殖，但不抑制其他系细胞的增殖，并抑制体内血管生成。我们将其命名为钙网蛋白血管抑素的NH2末端结构域。当接种到裸鼠体内时，血管抑素减少了Burkitt淋巴瘤、结肠癌、乳腺癌、黑色素瘤、横纹肌肉瘤、肺腺癌和Wilms肿瘤的生长。与血管抑素相比，全长钙网织蛋白、缺少NH2末端1-120个氨基酸的钙网织蛋白以及包含120-180个氨基酸的内部钙网织蛋白片段可以抑制血管内皮细胞的增殖、血管生成和体内肿瘤生长。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织蛋白全长分子可到达的区域，并定位于钙网织蛋白NH2结构域内的61个氨基酸片段。因此，我们已经确定钙网蛋白和血管抑素是在临床前肿瘤模型中抑制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.