利用人類臍靜脈內皮細胞探討S1P調控VEGF-C及淋巴標記表現機制之研究

Abstract

在腫瘤的生成和轉移過程中，淋巴管新生是一個很重要的機制。目前關於淋巴管新生的機制研究尚未完全了解。神經鞘氨醇 1-磷酸鹽 (Sphingosine 1-phosphate, S1P)屬於小分子水解磷酸酯，透過和其受器的結合，進而調控許多不同的反應，包括細胞增生、細胞分化、發炎反應和血管新生等反應。前人的研究指出神經鞘氨醇 1-磷酸鹽在體內外皆能促進淋巴管新生。在我們的研究也發現在人類臍靜脈內皮細胞 (Human umbilical vein endothelial cells, HUVECs)中，神經鞘氨醇 1-磷酸鹽會促進C型血管內皮生長因子 (Vascular endothelial growth facter-C, VEGF-C)的表現，進而調控淋巴管標記因子的表現。藉由核酸干擾技術，我們證實神經鞘氨醇 1-磷酸鹽調控人類臍靜脈內皮細胞淋巴管新生是透過第二型基質金屬蛋白酶 (Matrix metalloproteinase-2, MMP-2)和第一型纖維母細胞生長因子接受器 (Fibroblast growth receptor-1, FGFR-1)之訊息傳導路徑，另外此機制是透過纖維母細胞生長因子-1 (Fibroblast growth factor-1, FGF-1)依賴傳導路徑，而非纖維母細胞生長因子-2 (FGF-2)。本實驗結果顯示出神經鞘氨醇 1-磷酸鹽對於調控淋巴管新生是一個很重要的因子。

Lymphangiogenesis is an essential process in regulating tumor growth and metastasis. Sphingosine 1-phosphate (S1P) is a potent bioactive phospholipid, which acts as a ligand for a family of G protein-coupled S1P receptors. Through binding to these receptors, S1P modulates multiple biological processes, including cell proliferation and differentiation, inflammatory responses, and angiogenesis. Previous reports showed that S1P induces lymphangiogenesis both in vitro and in vivo. In our present study, we demonstrated that S1P induces vascular endothelial growth factor receptor (VEGF)-C expression and further upregulates lymphatic marker expressions in human umbilical vein endothelial cells (HUVECs). We previously showed that activation of lysophophatidic acid (LPA) receptors enhanced VEGF-C expression through transactivating the epidermal growth factor receptor (EGFR). In contrast, S1P-induced VEGF-C expression was blocked by treatment with SU5402, a fibroblast growth factor (FGF) receptor inhibitor, while an EGFR inhibitor has no effect. By using FGFR-1 and matrix metalloproteinase (MMP)-2 small interfering (si)RNA, we demonstrated that S1P induced HUVECs lymphangiogenesis is mediated through a MMP-2/FGFR-1 -dependent pathway. In addition, S1P-induced phosphorylation of FGFR-1 was blocked by treatment with an MMP inhibitor. Moreover, we also demonstrated that FGF-1, but not FGF-2, participates in the transactivation process.These results demonstrate a novel transactivating signaling processes activated by S1P.