Our long-term objectives are to advance the understanding of the molecular mechanism(s) that govern the self-renewal property of leukemic stem cells (LSCs). LSCs are cells that can give rise to leukemia in transplant models, and therefore have self-renewal properties. It is hypothesized that these cells are not targeted under current chemotherapy regimens and therefore account for drug resistance and leukemia relapse. Identifying genes or signaling pathways involved in the self-renewal of LSCs will likely promote the development of more effective treatments for leukemia and other cancers. Bmi-1 is a key element involved in LSC self-renewal, and is aberrantly upregulated in LSCs. The underlying cause(s) for deregulation of Bmi-1 in LSCs remain unknown. We have discovered that SALL4, a newly identified pluripotency factor and a novel oncogene, is aberrantly expressed in human acute myeloid leukemia (AML). Transgenic mice that mimic this aberrant expression of SALL4B, one of the SALL4 isoforms, develop AML.8 Further studies on these SALL4B mice have led to the identification and characterization of LSCs in the SALL4B-induced AML mouse model. Parallel to gain-of-function studies, knockdown of SALL4 expression in leukemic cell lines triggers cell apoptosis and growth arrest. While upregulation of Bmi-1 is found in the SALL4B-induced LSCs, downregulation of SALL4 leads to decreased expression of Bmi-1. Restoring Bmi-1 expression in SALL4 knockdown leukemic cell lines rescues the apoptotic phenotype. More detailed studies have demonstrates that Bmi-1 is a direct target of SALL4 in bone marrow cells. Based on these findings, we hypothesize that deregulation of SALL4B plays a key role in promoting self-renewal of LSCs by activation of Bmi-1. To prove this hypothesis, I propose to 1) Determine the functional role(s) of SALL4 in self-renewal of normal hematopoietic stem cell (HSCs) and LSCs;and 2) Define the mechanism of SALL4 enhancement of self-renewal of HSCs and LSCs with a focus on its up-regulation of Bmi-1. These two groups of experiments will serve to better understand the critical mechanism(s) in leukemogenesis, and potentially develop novel strategies to combat leukemia.

Public Health Relevance

In United States, there are 33,000 new cases of leukemia (blood cancer) with a death rate of 23,000 every year. Despite chemotherapy and bone marrow transplantation, most leukemia relapses and has a high-mortality rate. One recent approach to decrease the incidence of relapse involves targeting """"""""leukemic stem cell (LSC)"""""""", and we propose to test the functional role of a novel oncogene SALL4 in LSCs and its potential usage in treating leukemia.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
3R01HL092437-01A1S1
Application #
7864588
Study Section
Cancer Molecular Pathobiology Study Section (CAMP)
Program Officer
Thomas, John
Project Start
2009-07-01
Project End
2011-06-30
Budget Start
2009-07-01
Budget End
2011-06-30
Support Year
1
Fiscal Year
2009
Total Cost
$266,062
Indirect Cost
Name
Brigham and Women's Hospital
Department
Type
DUNS #
030811269
City
Boston
State
MA
Country
United States
Zip Code
02115
Li, A; Jiao, Y; Yong, K J et al. (2015) SALL4 is a new target in endometrial cancer. Oncogene 34:63-72
Ueno, Shikiko; Lu, Jiayun; He, Jie et al. (2014) Aberrant expression of SALL4 in acute B cell lymphoblastic leukemia: mechanism, function, and implication for a potential novel therapeutic target. Exp Hematol 42:307-316.e8
Wang, Fei; Zhao, Wenxiu; Kong, Nikki et al. (2014) The next new target in leukemia: The embryonic stem cell gene SALL4. Mol Cell Oncol 1:e969169
Tang, P; Gao, C; Li, A et al. (2013) Differential roles of Kras and Pten in murine leukemogenesis. Leukemia 27:1210-4
Yong, Kol Jia; Gao, Chong; Lim, Joline S J et al. (2013) Oncofetal gene SALL4 in aggressive hepatocellular carcinoma. N Engl J Med 368:2266-76
Li, Ailing; Yang, Youyang; Gao, Chong et al. (2013) A SALL4/MLL/HOXA9 pathway in murine and human myeloid leukemogenesis. J Clin Invest 123:4195-207
Gao, Chong; Kong, Nikki R; Li, Ailing et al. (2013) SALL4 is a key transcription regulator in normal human hematopoiesis. Transfusion 53:1037-49
Gao, Chong; Dimitrov, Todor; Yong, Kol Jia et al. (2013) Targeting transcription factor SALL4 in acute myeloid leukemia by interrupting its interaction with an epigenetic complex. Blood 121:1413-21
Hobbs, Robin M; Fagoonee, Sharmila; Papa, Antonella et al. (2012) Functional antagonism between Sall4 and Plzf defines germline progenitors. Cell Stem Cell 10:284-98
Gao, Chong; Kong, Nikki R; Chai, Li (2011) The role of stem cell factor SALL4 in leukemogenesis. Crit Rev Oncog 16:117-27

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