Investigation of the Regulation of Bmi1 by Emt Regulator Twist1 in the Promotion and Maintenance of Acute Myeloid Leukemia Stem Cells

Acute myeloid leukemia (AML) is one of the most common hematological malignancies in Taiwan. In spite of the high susceptibility of leukemic blasts to chemotherapeutic agents and considerable advances in therapeutic approaches, only about 30~40% of young adults afflicted with the disease are cured, and the outcome is far more dismal in the elder patients. It is widely speculated that there is a subpopulation of AML cells referred to as "leukemia stem cells" (LSC) that alone have long-term repopulating potential and the ability to propagate and maintain the AML phenotype. Eradication of this stem-cell compartment of AML is considered essential to the eventual cure of the disease. Bmi1, a member of Polycomb group (PcG) genes which are important regulators during development, plays an essential role in maintaining the self-renewal capacity of hematopoietic stem cells (HSCs). Bmi1 has also been suggested to be critical in leukemogenesis, as Bmi1 expression is required for maintenance and self-renewal of LSCs. Twist1 was initially identified as a master regulator of embryonic morphogenesis and later found to be an important metastasis regulator as well. We recently found that Twist1 activated Bmi1 expression in a head and neck cancer cell model. Knowing that BMI1 expression is required for maintenance of LSCs, we therefore speculate that Twist1 might govern the pathogenesis of development of AML as well. Preliminary data demonstrated that Bmi1 could be upregulated by Twist1 overexpression in AML cells. This proposal firstly aims to confirm that whether Twist1 overexpression promotes stemness of AML. We will also investigate the role of Bmi1 in Twist1-induced stemness of AML. Different approaches will be applied to elucidate the molecular mechanism. Phenotypic assays for confirming Twist1/Bmi1 overexpression induced stemness, including flowcytometric analysis of stem cell markers, in vitro/in vivo tumorigenecity assays, self-renew/differentiation assays, will also be performed in different clones of AML cells. Bioinformatic approaches will be used to identify the novel downstream targets in Twist1/Bmi1-mediated stemness. The collective effect of Twist1, Bmi1 and other downstream targets in promoting AML stemness will also be investigated. Finally, the clinical significance of Twist1, Bmi1, and novel downstream targets will be tested by tissue microarray-immunohistochemistry method in AML samples. We will also try to find the effective combination of available molecular targeted agents and chemotherapy in treating LSCs. These results will be an important breakthrough in elucidation of the mechanism of Twist1-mediated stemness in AML cells, and will provide valuable information for developing future strategies in the treatment of AML. 表 C011 共 頁 第 頁

Project ID:PC10001-1139
External Project ID:NSC99-2314-B182-009-MY3