摘要

1. CD69於慢性髓性白血病細胞株K562的細胞命運之角色The role of CD69 in the cell fate of chronic myelogenous leukemia cell line K562 • K562細胞是由表現Bcr-Abl的chronic myelogenous leukemia (CML)所建立的細胞株。CML是幹原細胞不正常的髓性細胞增殖性疾病（myeloproliferative disorder），此種細胞失去分化能力。Activin A 是多功能型的細胞激素（pleiotropic cytokine），屬於TGF-β(transforming growth factor TGF-β) 超級家族的一員。已知Activin A 是誘導細胞分化成紅血球系的因子。在過去的研究，我們利用p38路徑的細胞命運決定的角色當工具，去分析K562細胞的增生與分化機制。之前，我們已經利用PCR-select cDNA subtraction analysis 篩選到一個基因參與在K562的不分化狀態。在本論文，我們發現一個基因，CD69，可以被Activin A負調控，而且當p38 MAPK抑制劑SB203580與Activin A一起使用時，可以恢復它的表現量。大量表現p38 dominant negative mutants，p38αAF或p38βAF，於K562細胞中，Activin A抑制CD69表現的能力會被降低、且增加細胞增生和降低細胞分化。我們更進一步證明，Activin A會透過抑制Erk1/2活性來抑制CD69表現。我們利用Bcr-Abl酪氨酸激脢 的抑制劑STI571處理K562 細胞，會降低細胞的CD69 mRNA和蛋白的表現。除此之外，我們發現在BaF3細胞中，Bcr-Abl 會正調控CD69 promoter活性。為了證明CD69在CML細胞功能的角色，我們建立了可以表現CD69的質體。在未來我將證實CD69在K562細胞增生和分化的角色。

2. The K562 cells are one of the Bcr-Abl expressing chronic myelogenous leukemia (CML) cell lines. CML is a clonal myelo-proliferative disorder of the stem cells, which have lost their differentiation activity. Activin A is a pleiotropic cytokine belonging to the transforming growth factor (TGF)- superfamily. Activin A is known to be a commitment factor for erythroid differentiation. In a previous study, we showed that the cell fate determining role of the p38 MAPK pathway may be used as a tool to understand the molecular mechanisms for the proliferation and differentiation of K562 cells. Previously, we have used the PCR-select cDNA subtraction analysis to screen for genes involved in the undifferentiated status of K562 cells. In this study, we found that CD69 was down regulated by Activin A, and its expression level was restored by using the combination of p38 MAPK inhibitor SB203580 with Activin A. The Activin A-inhibited CD69 expression was reduced in K562-derived cells stably overexpressing the p38 dominant negative mutants, p38αAF or p38βAF, which was associated with increased cell proliferation and decreased differentiation. We further demonstrated that Activin A inhibited CD69 expression by deactivating ERK1/2. The exposure of K562 cells to the Bcr-Abl tyrosine kinase inhibitor STI571 resulted in decreased expression of CD69 mRNA and protein. In addition, Bcr-Abl was found to up-regulate CD69 promoter activity in BaF3 cells. To investigate the role of CD69 for CML cell function, the CD69 expressing plasmids were constructed. The role of CD69 in cell proliferation and differentiation of K562 cell was examined in the near future.