Assessing the transformation ability of CD44s and CD44v6 in IEC-6 normal intestinal epithelial cells
| Autor: | Wen-Chen Huang, 黃文辰 |
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| Rok vydání: | 2015 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 103 CD44 is not only a biomarker frequently used for isolating various CSCs, but also contributes to their stemness. Our previous study has shown that hyaluronic acid (HA), by interacting with CD44, activates c-Src kinase which subsequently upregulates the expression of the Snail which in turn directly diminishes the expression of miR-203, a well-known tumor suppressor and a stemness inhibitor, leading to an increase in the stemness of HCT-15 and HT-29 human CRC cells. Due to an alternative splicing of its primary transcript, CD44 proteins can exist as either a standard (CD44s) or different variant (CD44v) isoforms and the latter ones are predominantly expressed in tumor tissues. Among CD44v’s, the CD44v6 was found to cooperate with c-Met and activate EMT, hence increasing migration, invasion and metastasis of CRC cells. Even though the crucial roles of CD44, especially its variant isoforms, in the malignant progression of different types of tumors were well documented, little is known about the transformation abilities of CD44s and CD44v in normal intestinal epithelial cells. To answer these intriguing questions, ICE-6 normal rat small intestinal epithelial cells were chosen as a model and stable clones overexpressing human genes encoding CD44v6 and CD44s, respectively, were established. I found that although the growth rates of both CD44v6- and CD44s -overexpressing clones were similar to that of the parental IEC-6 cells, they exhibited higher saturation density and better survival, respectively, in a regular and a serum-free condition. The latter was due to a stronger anti-apoptotic effect. In accordance, protein levels of two anti-apoptotic factor, Bcl-2 and Bcl-xL, were found to be upregulated in CD44v6-overexpressing clones. Moreover, these clones also formed more colonies in soft agar and more large-size spheres in a defined medium than the CD44s-overexpressing clones. Intriguingly, the levels of Lgr5, a marker for both normal and cancerous intestinal stem cells, were markedly increased in CD44v6-overexpressing clones. Taken together, overexpression of both CD44v6 and CD44s in IEC-6 normal intestinal epithelial cells could induce their transformation, and the former had a much higher potency than the latter. These observations warrant a further investigation of the mechanisms underlying CD44v6-induced transformation of IEC-6 cells as well as that underlying a stronger transforming ability of CD44v6. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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