| Summary: | 碩士 === 高雄醫學大學 === 生物科技學系碩士班 === 97 === β-Cateninis a main factor controlling the canonical Wnt signaling pathways involved in morphogenesis and cancer development in mammalian cells(Johnson and Rajamannan, 2006; Takahashi-Yanaga and Sasaguri, 2007). We have established one stable cell line, PC3-f-β-Catenin-(T41A, S45A), that displays constitutively activeβ-Catenin/Tcf4 signaling to pursuit this pathways in development of prostate cancers. Interestingly, our cell model exhibits a less tight cell-cell adhesion with stronger invasiveness in comparison with that of PC3-control cells, which carry one empty vector to serve as the vehicle control. We further performed microarray analysis and real-time PCR in this cell model, demonstrating that MMP-2, MMP-7 and OPG (osteoprotegerin) are up-regulated byβ-Catenin/Tcf4 signaling. These results suggested β-Catenin/Tcf4 might involve in osteoblastic metastasis of prostate cancer. We are using osteotropic xenograft model in nude mice to address this issue. Our results demonstrated that over-expression ofβ-Catenin(T41A、S45A) did not alter growth rate of subcutaneous(SC) tumors, and in contrast, it dramatically changed the tumor of formation in bone environment, which were 100% for PC3-f-β-Catenin-(T41A, S45A) cells and 0% for PC3-mock cells. Significantly, we observed both osteoblastic and osteolytic lesions in this osteotropic xenograft tumor. Together, our results suggested that β-Catenin/Tcf4 signaling promoted osteotropic PCa growth and might determine formation of osteoblastic and osteolytic lesions.
In addition, we also obtained the other two stable lines, PC3-f-Tcf4 and PC3-f-ΔTcf4, that express the full-length and deletion (β-Catenin binding domain) form of Tcf4, respectively. In combination of those two lines with PC3-f-β-Catenin-(T41A, S45A), we asked how Tcf4/repressor complex convert into Tcf4/β-catenin complex. In electronic mobility shift assay (EMSA), we demonstrated that Tcf4/repressor complex always exists in the absence of ??-catenin, and Tcf4/β-catenin complex becomes dominant in the presence of β-Catenin. Significantly, β-catenin can not replace the repressor to interact with Tcf4 once Tcf4/repressor binds to DNA in vitro. These results suggested that the mechanism by which Tcf4/repressor complex convert into Tcf4/β-catenin complex is much more complicated than that of the previous proposal. Moreover, our results also showed that the repressor of Tcf4 in PC3 cells is not the repressor identified by other groups in different cell system
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