在体肿瘤需要血液供给氧及营养物质。肿瘤只有诱导周围血管出芽并形成血管网方可增大至临床可见的大小。由于环境的变化或基因的改变,肿瘤细胞向血管生成表型转化。瘤细胞释放一些可弥散的信息分子诱导瘤周静息状态的毛细血管出芽形成新生毛细血管腔。新生血管增加了肿瘤氧和营养物的供给,有利于肿瘤的生长。瘤细胞进入循环始于新生血管的形成, In vivo tumors require blood to supply oxygen and nutrients. Tumors only induce peripheral vascular budding and the formation of vascular network can increase to the clinically visible size. Tumor cells are transformed into angiogenic phenotypes due to environmental changes or genetic changes. Tumor cells release some diffusible information molecules to induce perivascular resting state of capillaries to bud into the nascent capillaries. Neovascularization increases the supply of tumor oxygen and nutrients, favoring tumor growth. Tumor cells into the circulation began in the formation of neovascularization,