| Summary: | 碩士 === 國立陽明大學 === 生命科學暨基因體科學研究所 === 96 === Colorectal cancer (CRC) is the fourth leading cause of cancer-related death in Taiwan. The poor prognosis of CRC patients is mostly due to the presence of metastatic disease. By cDNA microaraay analyses performed in our lab, the ligand of CD44 variant isoform (CD44V), osteopontin (OPN), was identified to be frequently over-expressed in human gastric cancer. Based on the observations that overexpression of CD44v is a common event in gastrointestinal track cancers and is correlated to poorer prognosis, we further explored the biological consequence of OPN-induced CD44 ligation. We found that ligation of CD44 confers cells increased survival through activation of Src-integrin signal. Because OPN and CD44V are also frequently overexpressed in human CRC, in this study, I explore the role of CD44 clustering in colorectal cancer cell lines, in particular its effects on cell migration and invasion. Cell lines derived from CRC were screened for the expression of CD44 isoforms (CD44S and CD44V). Colon cancer-derived HCT116 and H3347 cells were chosen for this study, and the ability of cell migration and invasion were examined by Boyden chamber assays. Antibody-induced crosslinking was performed to mimic ligand-induced clustering of CD44. Our data showed that ligation of CD44 promotes cell migration and invasion in both the CD44-expressing HCT116 and H3347 cells. My results further showed that CD44 ligation induces cell morphological changes, as evidenced by the presence of increased membrane protrusions as well as the formation of filopodia. The CD44-mediated cytoskeleton reorganization was accompanied with the presence of more abundant focal adhesions and increased level of phosphorylation of focal adhesion proteins paxillin and FAK. In agreement, cell spreading and cell adhesion were facilitated by CD44 ligation. Increased serection of MMP-2 and MMP-9 was also observed As a consequence, CD44 ligation promotes cell movement as monitored by live cell imaging system, whereas reducing CD44 expression by lentiviral vector-based shRNA technique led to decreased cell migration. Based on these data, it is conclude that ligation of CD44 induces cell cytoskeleton reorganization and promotes cell movement, leading to increased cell migration and invasion
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