Molecular Analysis on Tumor Invasion and Metastasis of CD44 Variant Forms

CD 44是透明质酸的主要受体，参与许多生物学过程，包括细胞迁移、肿瘤侵袭和转移。为了检查CD 44变体分子如何促进肿瘤细胞侵袭和转移，将CD 44阴性人肺癌细胞系的标准CD 44 s（82 s）、CD 44 v8 -10（82 E）和模拟（82 pCI）转染子皮下注射到SCID小鼠中。在82 pCI和82 s来源的肿瘤中，多个不规则的坏死灶突出，而在82 E肿瘤中坏死很少。我们发现82 E肿瘤间质中的小血管比82 s和82 pCI肿瘤的小血管多。82 E细胞在mRNA和蛋白水平上显示血管内皮生长因子（VEGF）的产生增加。82 E细胞的VEGF mRNA水平以细胞密度依赖性方式增加，并且由于细胞表面携带透明质酸，因此通过用透明质酸酶处理来消除这种诱导的产生。此外，刺激性抗CD 44抗体的加入也增加了VEGF的产生。这些表明同型细胞-细胞接触通过细胞表面透明质酸的参与刺激CD 44 v8 -10，并导致VEGF的产生增强。因此，我们的研究表明，CD 44 v8 -10阳性癌症可能具有通过VEGF产生诱导血管生成而生长的优势。

CD44 is a major receptor for hyaluronan and is involved in many biological processes, including cell migration, tumor invasion, and metastasis. To examine how CD44 variant molecules contribute to the tumor cell invasion and metastasis, standard CD44s (82s), CD44v8-10 (82E) and mock (82pCI) transfectants of a CD44-negative human lung cancer cell line were subcutaneously injected into SCID mice. In 82pCI- and 82s-derived tumors, multiple irregular foci of necrosis were prominent, while necrosis was scant in 82E tumors. We found the increased small vessels in the stroma of 82E tumors compared to those of 82s and 82pCI tumors. 82E cells showed the enhanced production of vascular endothelial growth factor (VEGF) in both mRNA and protein levels. The levels of the VEGF mRNA from 82E cells increased in a cell-density dependent manner, and this induced production was abolished by the treatment with hyaluronidase as the cells carried hyaluronan on their surface. Furthermore, the addition of stimulatory anti-CD44 antibody also increased the production of VEGF. These suggest that a homotypic cell-cell contact stimulates the CD44v8-10 through the engagement of cell surface hyaluronan and resulted in the enhanced production of VEGF. Accordingly, our study indicates that CD44v8-10 positive cancer may have an advantage to grow by the induced angiogenesis through the VEGF production.