血管新生 (angiogenesis) 是只從舊有血管長出心血管的過程，通常是發生在損傷修復、組織新生以及女性的生理週期。血管新生的過程包括了內皮細胞間質的酵素性分解、內皮細胞的遷移、內皮細胞的增生，最後長出新的血管。血管新生作用是目前腫瘤發育上的一個重要的課題，不管在生理上或病理上都扮演十分重要的角色，因此抑制血管新生是癌症治療的策略之一。血管靜止蛋白 (angiostatin)是血纖維蛋白溶酶原前四個kringle的一個片段蛋白，目前發現它能非常有效的抑制血管新生。許多研究都指出不同的kringle片段具有不同的抑制血管新生能力。本實驗室之前發現三個血纖維蛋白溶酶原片段蛋白(K185-548、K1106-548與K1134-548)，這三個但白對內皮細胞增生和移動的抑制效果明顯比血管靜止蛋白(K1-4)來的顯著，為了更近一步探討此三個蛋白在動物實驗中是否能抑制腫瘤生長，本實驗室利用反轉錄病毒分別將K185-548、K1106-548以及K1134-548的基因送至帶有黑色素細胞瘤的小鼠腫瘤上，並觀察腫瘤大小的差異，實驗結果發現施以此三個片段基因處理的小鼠腫瘤體積比對照組小，尤其是K185-548。以血纖維蛋白溶酶原片段處理牛副動脈內皮細胞(CPAE)後，發現這些貼附的細胞開始走向細胞凋亡(apoptosis; anoikis)，並且觀察到caspase-8、-9、-3與-2的活化，以及cytochrome c從粒線體釋放至細胞質中。然而，我們卻發現要大量的抑制劑才能抑制細胞走向細胞凋亡的現象。另一方面，由於這些血纖維蛋白溶酶原是透過integrin與細胞結合。在許多不同的細胞株中，FAK的磷酸化會造成細胞內很多訊號分子的活化，因此我們推測血纖維蛋白溶酶原所引發的FAK磷酸化很有可能與細胞經蛋白處理後造成其失去與ECM物質之間的作用力有關。另一方面，我們也發現細胞內調控蛋白合成的分子Akt，其磷酸化的程度也因為受到K185-548的調控而下降。

　　Angiogenesis, formation of new blood vessels from existing endothelium, occurs during wound repair, organ regeneration and menstrual cycle. The process of angiogenesis consists of basement membrane degradation, migration and proliferation of endothelial cell. It is accepted that tumor growth and metastasis depend on angiogenesis, so that the anti-angiogenic strategies have been applied for cancer therapy. Angiostatin, a kringle-containing fragment of plasminogen, is a potent inhibitor of angiogenesis. Many studies demonstrated that individual or multiple kringle fragments of angiostatin had different inhibitory activities on angiogenesis. Studies in our laboratory found that three plasminogen fragments, K185-548, K1106-548 and K1134-548, had higher inhibitory effect on proliferation of endothelial cells and migration than K1-4. In vitro assays revealed that three fragments acted as a potent inhibitor of endothelial cells. To study if they can also inhibit tumor growth in vivo, transient transfections of retroviral vectors that contained these fragments were performed on 293T cells by calcium phosphate method. The animal experiment showed that retroviral vectors bearing the three different plasminogen fragments could reduce the tumor volume of melanoma-bearing mice, especially K185-548. Endothelial cells (CPAE) were also shown to undergo apoptosis in response to plasminogen fragments. Caspase-8, -9, -3, and -2 were activated and cytosolic levels of cytochrome c was increased. However, we found that cells underwent apoptosis even treated with Z-DQMD-FMK (caspase-3 inhibitor). On the other hand, CPAE cells adhered to plasminogen fragments in an integrin-dependent manner. Phosphorylation of FAK, which leads to the activation of various signaling molecules, was reduced by plasminogen fragments, suggesting that dephosphorylatin of FAK may contribute to loss of focal adhesions and cell-matrix interactions.

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