Goldshmidt Orit, Zcharia Eyal, Abramovitch Rinat, Metzger Shula, Aingorn Helena, Friedmann Yael, Schirrmacher Volker, Mitrani Eduardo, Vlodavsky Israel
Department of Oncology, Hadassah-Hebrew University Hospital, Jerusalem 91120, Israel.
Proc Natl Acad Sci U S A. 2002 Jul 23;99(15):10031-6. doi: 10.1073/pnas.152070599. Epub 2002 Jul 3.
The present study emphasizes the importance of cell surface expression and secretion of heparanase (endo-beta-D-glucuronidase) in tumor angiogenesis and metastasis. For this purpose, nonmetastatic Eb mouse lymphoma cells were transfected with the predominantly intracellular human heparanase or with a readily secreted chimeric construct composed of the human enzyme and the chicken heparanase signal peptide. Eb cells overexpressing the secreted heparanase invaded a reconstituted basement membrane to a much higher extent than cells overexpressing the intracellular enzyme. Cell invasion was inhibited in the presence of laminaran sulfate, a potent inhibitor of heparanase activity and experimental metastasis. The increased invasiveness in vitro was reflected in vivo by rapid and massive liver colonization and accelerated mortality. In fact, mice inoculated with cells expressing the secreted enzyme succumb because of liver metastasis and dysfunction, as early as 10 days after s.c. inoculation of the cells, when their tumor burden did not exceed 1% of body weight. Cell surface localization and secretion of heparanase markedly stimulated tumor angiogenesis, as demonstrated by a 4-6-fold increase in vessel density and functionality evaluated by MRI of tumors produced by cells expressing the secreted vs. the nonsecreted heparanase, consistent with actual counting of blood vessels. Altogether, our results indicate that the potent proangoigenic and prometastatic properties of heparanase are tightly regulated by its cellular localization and secretion. The increased potency of the secreted enzyme makes it a promising target for anticancer drug development.
本研究强调了乙酰肝素酶（内切-β-D-葡糖醛酸酶）的细胞表面表达及分泌在肿瘤血管生成和转移中的重要性。为此，将主要定位于细胞内的人乙酰肝素酶或由人酶与鸡乙酰肝素酶信号肽组成的易于分泌的嵌合构建体转染至非转移性Eb小鼠淋巴瘤细胞。与过表达细胞内酶的细胞相比，过表达分泌型乙酰肝素酶的Eb细胞侵袭重组基底膜的程度要高得多。在存在硫酸昆布多糖（一种有效的乙酰肝素酶活性抑制剂及实验性转移抑制剂）的情况下，细胞侵袭受到抑制。体外侵袭性的增加在体内表现为迅速且大量的肝脏定植以及死亡率加快。事实上，接种表达分泌型酶的细胞的小鼠早在皮下接种细胞后10天就因肝转移和肝功能障碍而死亡，此时它们的肿瘤负荷不超过体重的1%。如通过对表达分泌型与非分泌型乙酰肝素酶的细胞所产生肿瘤的MRI评估血管密度和功能增加4至6倍所证明，乙酰肝素酶的细胞表面定位及分泌显著刺激肿瘤血管生成，这与血管实际计数结果一致。总之，我们的结果表明，乙酰肝素酶强大的促血管生成和促转移特性受到其细胞定位和分泌的严格调控。分泌型酶效力的增强使其成为抗癌药物开发的一个有前景的靶点。
