Characterization of signaling pathways regulating CD44 and OPN expression
| Autor: | Yu-Ling Wang, 汪玉玲 |
|---|---|
| Rok vydání: | 2008 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 96 Inappropriate activation of Wnt pathway is a frequent event in many cancers. It occurs mostly through mutations of either APC (adenomatousis polyposis coli) or ��-catenin and lead to the accumulation and nuclear translocation of stable ��-catenin and the activation of ��-catenin/TCF-mediated transcription, with up-regulated expression of a number of genes that contributes to tumor formation and progression. By comparative genomics approach, we have previously shown that the TCF downstream target genes OPN (osteopontin) and CD44, the principal receptor for OPN, are overexpressed in human gastric cancer, and OPN-mediated ligation of CD44 leads to increased cell survival through integrin activation. In addition, it is also observed that ligation of CD44 leads to increased expression of CD44 and other ��-catenin/TCF target genes. In this study, we further characterize the signaling pathway regulating OPN and CD44 expression. Our specific aims include: 1) to determine whether CD44 and OPN are Wnt pathway target gene, and 2) to determine whether CD44 ligation leads to a feed-back regulation of the expression of CD44 and OPN through ��-catenin/TCF pathway. We use reporter assay (TOPFlash and FOPFlash) to determined ��-catenin/TCF activity in different cancer cell lines, and we also perform immunofluoresence average to characterize subcellular localization of ��-catenin. As expected, the ��-catenin/TCF pathway is overactivated in many gastrointestinal cancer cell lines. Instead, this pathway remains intact and can be activated in the non-small cell lung cancer H1299 and A549 cells upon the treatment of Wnt3a. Our result showed that expression of OPN is increased in H1299 upon activation of the Wnt pathway and decreased upon inhibition of Wnt pathway, confirming that OPN is regulated by this pathway. CD44 and OPN are down-regulated in H3347 in which Wnt pathway is over-activated. We also observed that ligation of CD44 can increase the expression of OPN and CD44, but it has no effect on Wnt pathway sugges that CD44 ligation-mediated increase in CD44 and OPN expression is not mediated through Wnt pathway. It remains to be studied the molecular mechanisms signaling pathways through which ligation of CD44 leads to increased expression of OPN and CD44. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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