| 摘要: | Bcr-Abl是慢性骨髓性白血病(Chronic myelogenous leukemia , CML) 的主要致病因子，是由第9對染色體上的 Abl 與第22對染色體上的Bcr 發生轉位而產生，形成了Bcr-Abl 融合基因，轉錄出的Bcr-Abl蛋白具有持續活化態的tyrosine kinase活性，透過許多訊息傳遞路徑抑制細胞凋亡和分化能力導致細胞不斷增生。STI571(Imatinib mesylate )，可以抑制Bcr-Abl的tyrosine kinase活性，有效治療CML。然而，許多不同期的CML病患對STI571產生抗藥性。因此如果可以更了解Bcr-Abl所調控的訊息傳遞則可提供更多的治療方式。本實驗室先前篩選到CD69、CD24均表現在未分化的CML細胞株中，且也證實CD69與CD24都是屬於Bcr-Abl下游調控的蛋白。Bcr-Abl會誘導CD69及CD24表現，進而促進細胞增殖抑制細胞的凋亡與分化。過去實驗顯示，knock down CD69與CD24可以更有效的促進由STI571所誘導的細胞凋亡與分化且可觀察到hematopoietic stem cell (HSC) markers，例如：CXCR4、MDR-1、Notch-1等表現都有下降趨勢。過去只分別利用一個siRNA 序列knock down CD69和CD24，所以本篇論文將利用不同DNA序列的siRNA knock down CD69和CD24確認是否可以降低細胞存活率，促進細胞凋亡及分化。結果顯示，不同序列的siRNA knock down CD69與CD24後，也可以提升細胞對於STI571的敏感性造成細胞週期停留在G1 phase進一步的使細胞存活率下降，細胞凋亡比例增加。此外，降低CD69與CD24表現會促進細胞的分化，降低造血幹細胞標記、以及IL-8、VEGFA表現。所以於CML K562細胞，CD69和CD24會抑制細胞的凋亡和分化、促進細胞增生。未來也許可將knock down CD69和CD24與STI571聯合使用作為治療CML的方式。
Bcr-Abl is the major pathogenic factor of chronic myelogenous leukemia (CML). It results from translocation of ABL gene on chromosome 9 with BCR gene on chromosome 22, generating the Bcr-Abl fusion gene. This gene encodes Bcr-Abl oncoprotein that is a constitutive active tyrosine kinase and inhibits cell apoptosis and differentiation through various signaling pathways. STI571(Imatinib mesylate), a specific inhibitor of Bcr-Abl, is effective for CML treatment, but resistance develops in this disease. Therefore, it is important to decipher the mechanism of Bcr-Abl-mediated tumorigenicity in CML. In our previous study, we have identified that CD69 and CD24 genes express in CML cell line K562, and downstream targets of Bcr-Abl signaling. CD69 and CD24 play the roles of inhibition of cell apoptosis and differentiation, and promotion of cell proliferation. Our previous data also showed that knock down of CD69 or CD24 in K562 cells enhanced STI571-induced cell apoptosis, differentiation, growth inhibition, and reduction of hematopoietic stem cell markers such as CDCP-1, PECAM-1, MDR1, and Notch-1 with only one siRNA sequence. In this study, we use the different siRNA sequences to knock down CD69 and CD24 in K562 cells. We also found that CD69 and CD24 roles of CD69 and CD24 can enhance K562 cell sensitivity to STI571 and result in cell G1 arrest and cell apoptosis. In addition, inhibition of CD69 and CD24 not only reduced cell differentiation and HSC marker expressions but also increased the expressions of IL-8 and VEGFA. These results suggest that CD69 and CD24 play the important roles of proliferation, apoptosis, and differentiation in K562 cells. Co-treatment with targeting of CD69 or CD24 and STI571 may provide a promising treatment in CML. |
