Galectin-1是一可與β-galactosides結合的lectins家族中的成員，以非共價鍵的方式鍵結組成同型二聚體，在每一個次單元上皆有碳水化合物辨識功能區。已有證據指出galectin-1蛋白牽涉許多生物功能，例如細胞增生、細胞貼附、細胞凋亡、轉移、以及免疫調節等。實驗室先前研究發現在腫瘤組織附近的間質組織與血管內皮細胞會高度表現galectin-1，也發現galectin-1會有選擇性的藉由碳水化合物辨識功能區與neuropilin-1 (NRP-1) 結合，而不會與VEGFR-1、VEGFR-2、或VEGFR-3結合，利用血管滲透分析的動物實驗發現galectin-1會增加血管通透性，迄今galectin-1增加內皮細胞血管通透性的機轉尚未釐清。在本研究論文中，首先我們利用細胞滲透分析技術，發現galectin-1不管在細胞實驗或動物實驗都能誘導人類血管內皮細胞通透性增加，利用免疫螢光染色實驗觀察VE-cadherin及F-actin發現在galectin-1處理下細胞和細胞之間的間隙會有所改變且細胞骨架會重新排列。除此之外，利用病毒感染技術將NRP-1基因沉默證實了galectin-1所誘導的通透性是需要NRP-1，並發現VEGF所誘發的血管內皮細胞通透性也減少。雖然galectin-1可導致血管內皮細胞的VEGFR-2磷酸化，但我們將VEGFR-2基因沉默並不影響galectin-1所引發的通透性，因此galectin-1結合NRP-1似乎並非透過活化VEGFR-2來使內皮細胞通透性增加。探討其細胞訊息傳遞的途徑，發現galectin-1誘發的血管內皮細胞滲透性增加可能與Akt的磷酸化有強烈的關係，因為利用Akt抑制劑可以很有效的抑制galectin-1所誘導通透性增加，而MAPK pathway也有可能牽涉其中。接下來利用動物模式，將galectin-1基因沉默的口腔癌細胞株打入免疫缺陷小鼠使其長腫瘤，結果發現galectin-1基因沉默使腫瘤血管滲透現象降低且使腫瘤生長變慢，最後也利用臨床檢體印證了galectin-1與血管滲透性有正相關。綜上所述，本研究釐清了galectin-1對於癌症的進展及其分子機制，指出腫瘤生成的微環境對整個癌化的過程扮演重要角色，未來galectin-1蛋白或許能成為治療腫瘤的目標。

Galectin-1 (Gal-1) is a member of the β-galatosides-binding lectin family. It is a noncovalent homodimer and each subunit contains one carbohydrate-recognition domain (CRD). Gal-1 has been implicated in certain biological processes, including cell proliferation, cell adhesion, apoptosis, metastasis, and immunoregulation. Gal-1 was recently identified as being overexpressed in tumor-associated stroma and capillary endothelial cells. In our previous studies, we found Gal-1 selectively bound neuropilin-1 (NRP1) but not VEGFR-1, VEGFR-2, or VEGFR-3, via the carbohydrate recognition domain and promoted vascular permeability by the Miles assay. However, the mechanism by which galectin-1 promotes endothelial cell permeability is still elusive. In this study we measured transendothelial passage of FITC-dextran and found that galectin-1 induced an increase in paracellular permeability of human umbilical vein endothelial cells (HUVECs) and functioned as an inducer of vascular permeability in vivo and in vitro. Immunofluorescence staining of VE-cadherin and phalloidin/actin indicated that the alteration of cell-cell junction and cytoskeleton rearrangement were found in the Gal-1-treated cells. Furthermore, silencing of NRP-1 expression suppressed Gal-1-induced HUVECs permeability and attenuated VEGF-induced permeability. Biochemical analyses revealed the phosphorylation of VEGFR-2 was also strongly induced by Gal-1, but silenceing of VEGFR-2 did not influence Gal-1-induce permeability. To identify the intracellular signal pathways that participate in Gal-1-induced endothelial permeability, we found Gal-1 can rapid induce the phosphorylation of ERK1/2, p38, and Akt in endothelial cells. Wortmannin (a specific chemical inhibitor of PI3K) abolished Gal-1-induced Akt activation and inhibited Gal-1-induced endothelial permeability, implying that PI3K/Akt pathway is essential for Gal-1-induced permeability. To further examine the effects of Gal-1 in xenograft tumor model, we found that knockdown of Gal-1 in HSC-3 reduced tumor vascular permeability and tumor size. In clinical oral squamous cell carcinoma (OSCC) specimens, fibrinogen immunohistochemistry provided evidence for a significant positive correlation between increased vascular permeability and the expression of Gal-1 in vascular endothelial cells. In conclusion, we investigated the possible molecular mechanisms of Gal-1-induced tumor vascular permeability, and it may be as a potential therapeutic target.

Amornphimoltham P, Patel V, Leelahavanichkul K, Abraham RT, Gutkind JS (2008). A retroinhibition approach reveals a tumor cell-autonomous response to rapamycin in head and neck cancer. Cancer Res 68: 1144-53.

Anderson JM, Fanning AS, Lapierre L, Van Itallie CM (1995). Zonula occludens (ZO)-1 and ZO-2: membrane-associated guanylate kinase homologues (MAGuKs) of the tight junction. Biochem Soc Trans 23: 470-5.

Baluk P, Morikawa S, Haskell A, Mancuso M, McDonald DM (2003). Abnormalities of basement membrane on blood vessels and endothelial sprouts in tumors. Am J Pathol 163: 1801-15.

Banerjee S, Mehta S, Haque I, Sengupta K, Dhar K, Kambhampati S et al (2008). VEGF-A165 induces human aortic smooth muscle cell migration by activating neuropilin-1-VEGFR1-PI3K axis. Biochemistry 47: 3345-51.

Barondes SH, Cooper DN, Gitt MA, Leffler H (1994). Galectins. Structure and function of a large family of animal lectins. J Biol Chem 269: 20807-10.

Becker PM, Waltenberger J, Yachechko R, Mirzapoiazova T, Sham JS, Lee CG et al (2005). Neuropilin-1 regulates vascular endothelial growth factor-mediated endothelial permeability. Circ Res 96: 1257-65.

Birnbaum D (1995). VEGF-FLT1 receptor system: a new ligand-receptor system involved in normal and tumor angiogenesis. Jpn J Cancer Res 86: inside cover.

Biron VA, Iglesias MM, Troncoso MF, Besio-Moreno M, Patrignani ZJ, Pignataro OP et al (2006). Galectin-1: biphasic growth regulation of Leydig tumor cells. Glycobiology 16: 810-21.

Carmeliet P, Jain RK (2000). Angiogenesis in cancer and other diseases. Nature 407: 249-57.

Clausse N, van den Brule F, Waltregny D, Garnier F, Castronovo V (1999). Galectin-1 expression in prostate tumor-associated capillary endothelial cells is increased by prostate carcinoma cells and modulates heterotypic cell-cell adhesion. Angiogenesis 3: 317-25.

Dejana E, Corada M, Lampugnani MG (1995). Endothelial cell-to-cell junctions. FASEB J 9: 910-8.

Dvorak AM, Kohn S, Morgan ES, Fox P, Nagy JA, Dvorak HF (1996). The vesiculo-vacuolar organelle (VVO): a distinct endothelial cell structure that provides a transcellular pathway for macromolecular extravasation. J Leukoc Biol 59: 100-15.

Ellerhorst J, Troncoso P, Xu XC, Lee J, Lotan R (1999). Galectin-1 and galectin-3 expression in human prostate tissue and prostate cancer. Urol Res 27: 362-7.

Elola MT, Chiesa ME, Alberti AF, Mordoh J, Fink NE (2005). Galectin-1 receptors in different cell types. J Biomed Sci 12: 13-29.

Fischer C, Sanchez-Ruderisch H, Welzel M, Wiedenmann B, Sakai T, Andre S et al (2005). Galectin-1 interacts with the {alpha}5{beta}1 fibronectin receptor to restrict carcinoma cell growth via induction of p21 and p27. J Biol Chem 280: 37266-77.

Furuse M, Hirase T, Itoh M, Nagafuchi A, Yonemura S, Tsukita S (1993). Occludin: a novel integral membrane protein localizing at tight junctions. J Cell Biol 123: 1777-88.

Gavard J, Gutkind JS (2006). VEGF controls endothelial-cell permeability by promoting the beta-arrestin-dependent endocytosis of VE-cadherin. Nat Cell Biol 8: 1223-34.

Gimbrone MA, Jr., Leapman SB, Cotran RS, Folkman J (1972). Tumor dormancy in vivo by prevention of neovascularization. J Exp Med 136: 261-76.

Gumbiner B, Lowenkopf T, Apatira D (1991). Identification of a 160-kDa polypeptide that binds to the tight junction protein ZO-1. Proc Natl Acad Sci U S A 88: 3460-4.

Hong TM, Chen YL, Wu YY, Yuan A, Chao YC, Chung YC et al (2007). Targeting neuropilin 1 as an antitumor strategy in lung cancer. Clin Cancer Res 13: 4759-68.

Horiguchi N, Arimoto K, Mizutani A, Endo-Ichikawa Y, Nakada H, Taketani S (2003). Galectin-1 induces cell adhesion to the extracellular matrix and apoptosis of non-adherent human colon cancer Colo201 cells. J Biochem 134: 869-74.

Houck KA, Ferrara N, Winer J, Cachianes G, Li B, Leung DW (1991). The vascular endothelial growth factor family: identification of a fourth molecular species and characterization of alternative splicing of RNA. Mol Endocrinol 5: 1806-14.

Houck KA, Leung DW, Rowland AM, Winer J, Ferrara N (1992). Dual regulation of vascular endothelial growth factor bioavailability by genetic and proteolytic mechanisms. J Biol Chem 267: 26031-7.

Hsieh SH, Ying NW, Wu MH, Chiang WF, Hsu CL, Wong TY et al (2008). Galectin-1, a novel ligand of neuropilin-1, activates VEGFR-2 signaling and modulates the migration of vascular endothelial cells. Oncogene.

Kawasaki T, Kitsukawa T, Bekku Y, Matsuda Y, Sanbo M, Yagi T et al (1999). A requirement for neuropilin-1 in embryonic vessel formation. Development 126: 4895-902.

Klagsbrun M, D'Amore PA (1996). Vascular endothelial growth factor and its receptors. Cytokine Growth Factor Rev 7: 259-70.

Lum H, Malik AB (1996). Mechanisms of increased endothelial permeability. Can J Physiol Pharmacol 74: 787-800.

McDonald DM (1994). Endothelial gaps and permeability of venules in rat tracheas exposed to inflammatory stimuli. Am J Physiol 266: L61-83.

Mehta D, Malik AB (2006). Signaling mechanisms regulating endothelial permeability. Physiol Rev 86: 279-367.

Miao HQ, Klagsbrun M (2000). Neuropilin is a mediator of angiogenesis. Cancer Metastasis Rev 19: 29-37.

Miao HQ, Lee P, Lin H, Soker S, Klagsbrun M (2000). Neuropilin-1 expression by tumor cells promotes tumor angiogenesis and progression. FASEB J 14: 2532-9.

Minshall RD, Malik AB (2006). Transport across the endothelium: regulation of endothelial permeability. Handb Exp Pharmacol: 107-44.

Morikawa S, Baluk P, Kaidoh T, Haskell A, Jain RK, McDonald DM (2002). Abnormalities in pericytes on blood vessels and endothelial sprouts in tumors. Am J Pathol 160: 985-1000.

Neufeld G, Cohen T, Gitay-Goren H, Poltorak Z, Tessler S, Sharon R et al (1996). Similarities and differences between the vascular endothelial growth factor (VEGF) splice variants. Cancer Metastasis Rev 15: 153-8.

Noji S, Nohno T, Koyama E, Ide H, Taniguchi S, Saito T (1992). Morphogenetic roles of retinoic acid. J Nutr Sci Vitaminol (Tokyo) Spec No: 481-4.

Olsson AK, Dimberg A, Kreuger J, Claesson-Welsh L (2006). VEGF receptor signalling - in control of vascular function. Nat Rev Mol Cell Biol 7: 359-71.

Pan Q, Chanthery Y, Liang WC, Stawicki S, Mak J, Rathore N et al (2007). Blocking neuropilin-1 function has an additive effect with anti-VEGF to inhibit tumor growth. Cancer Cell 11: 53-67.

Petreaca ML, Yao M, Liu Y, Defea K, Martins-Green M (2007). Transactivation of vascular endothelial growth factor receptor-2 by interleukin-8 (IL-8/CXCL8) is required for IL-8/CXCL8-induced endothelial permeability. Mol Biol Cell 18: 5014-23.

Phung TL, Eyiah-Mensah G, O'Donnell RK, Bieniek R, Shechter S, Walsh K et al (2007). Endothelial Akt signaling is rate-limiting for rapamycin inhibition of mouse mammary tumor progression. Cancer Res 67: 5070-5.

Phung TL, Ziv K, Dabydeen D, Eyiah-Mensah G, Riveros M, Perruzzi C et al (2006). Pathological angiogenesis is induced by sustained Akt signaling and inhibited by rapamycin. Cancer Cell 10: 159-70.

Predescu SA, Predescu DN, Malik AB (2007). Molecular determinants of endothelial transcytosis and their role in endothelial permeability. Am J Physiol Lung Cell Mol Physiol 293: L823-42.

Rabinovich GA (2005). Galectin-1 as a potential cancer target. Br J Cancer 92: 1188-92.

Scott K, Weinberg C (2004). Galectin-1: a bifunctional regulator of cellular proliferation. Glycoconj J 19: 467-77.

Senger DR, Van de Water L, Brown LF, Nagy JA, Yeo KT, Yeo TK et al (1993). Vascular permeability factor (VPF, VEGF) in tumor biology. Cancer Metastasis Rev 12: 303-24.

Soker S, Takashima S, Miao HQ, Neufeld G, Klagsbrun M (1998). Neuropilin-1 is expressed by endothelial and tumor cells as an isoform-specific receptor for vascular endothelial growth factor. Cell 92: 735-45.

Stan RV (2002). Structure and function of endothelial caveolae. Microsc Res Tech 57: 350-64.

Sumpio BE, Riley JT, Dardik A (2002). Cells in focus: endothelial cell. Int J Biochem Cell Biol 34: 1508-12.

Tchaikovski V, Fellbrich G, Waltenberger J (2008). The molecular basis of VEGFR-1 signal transduction pathways in primary human monocytes. Arterioscler Thromb Vasc Biol 28: 322-8.

Tischer E, Mitchell R, Hartman T, Silva M, Gospodarowicz D, Fiddes JC et al (1991). The human gene for vascular endothelial growth factor. Multiple protein forms are encoded through alternative exon splicing. J Biol Chem 266: 11947-54.

van den Brule FA, Waltregny D, Castronovo V (2001). Increased expression of galectin-1 in carcinoma-associated stroma predicts poor outcome in prostate carcinoma patients. J Pathol 193: 80-7.

Weis SM (2008). Vascular permeability in cardiovascular disease and cancer. Curr Opin Hematol 15: 243-9.

Zachary I, Gliki G (2001). Signaling transduction mechanisms mediating biological actions of the vascular endothelial growth factor family. Cardiovasc Res 49: 568-81.