Inhibition Of A431 Cell Xenografted Tumor Angiogenesis By Down-regulation Of FUT1/FUT4

Lewis Y (LeY) antigen is highly expressed in a variety of human carcinomas of epithelial cell origin, and correlates with the enhanced neoplastic cell proliferation, invasion, metastasis and poor prognosis. LeY has led to its selection as an antigenic target relatively homogeneous expression in primary and metastatic lesions. Recent studies suggest antibody-based functional blockade of LeY may provide a novel therapeutic approach for the treatment of LeY-positive cancers. Fucosyltransferase I and IV (FUT1/FUT4) are the key enzymes for fucosylated LeY oligo- saccharide synthesis. The augmented LeY synthesis in cancers may be caused by the abnormal expression of FUT1/FUT4.In the past year, we concentrated on detecting the effect of FUT1/FUT4 siRNAs on tumor proliferation. We observed that treatment of tumor cells that were inoculated into the nude mice with FUT1/FUT4 siRNA impeded greatly tumor proliferation, the inhibitory effect of knocking down FUT1/FUT4 expression on tumor cell growth correlates with the decreased LeY expression. To further investigate the mechanism of epithelial tumor cell growth inhibited via inhibiting the synthesis of LeY by RNAi technology, we analyzed the relation between LeY and cancer angiogenesis.The over-expression VEGF of solid tumor produce abnormal growth signal to endothelial cells, so it is thought as one of the important factors inducing tumor angiogenesis, and VEGF level in tumor tissue is correlated with micro-vessel density (MVD). The purpose of this study is to make a preliminary test on whether LeY expression is associated with MVD in xenograft cancer models. To evaluate the changes of the FUT1/FUT4 and LeY oligosaccharide expression in xenograft cancer treated by FUT1/FUT4 siRNA, the excised tumor tissues are analyzed by RT-PCR for FUT1/FUT4, Western blot for VEGF and immunohistochemistry staining for LeY synthesis. The association between LeY expression and vessels density was explored by using CD34 antibody via counting MVD.The results demonstrate that, FUT1/FUT4 siRNA plasmids down- regulated LeY synthesis level, suppressed the expression of VEGF, and consequently reduced cancer angiogenesis in excised tumor tissues of xenograft cancer model. Thus it provides a new experimental basis for the mechanism of siRNA inhibiting the growth of the tumor. To study the expression and regulation of the fucosyltransferase, which not only conduces to study the mechanism of oligosaccharides in the process of tumor, proliferation; it may also serve as a new approach for further understanding mechanism of LeY on inhibiting cancer proliferation.