A SALL4/MLL/HOXA9 pathway in murine and human myeloid leukemogenesis
Ailing Li, … , Daniel G. Tenen, Li Chai
Ailing Li, … , Daniel G. Tenen, Li Chai
Published September 24, 2013
Citation Information: J Clin Invest. 2013;123(10):4195-4207. https://doi.org/10.1172/JCI62891.
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Research Article Oncology

A SALL4/MLL/HOXA9 pathway in murine and human myeloid leukemogenesis

Abstract

The embryonic self-renewal factor SALL4 has been implicated in the development of human acute myeloid leukemia (AML). Transgenic mice expressing the human SALL4B allele develop AML, which indicates that this molecule contributes to leukemia development and maintenance. However, the underlying mechanism of SALL4-dependent AML progression is unknown. Using SALL4B transgenic mice, we observed that HoxA9 was significantly upregulated in SALL4B leukemic cells compared with wild-type controls. Downregulation of HoxA9 in SALL4B leukemic cells led to decreased replating capacity in vitro and delayed AML development in recipient mice. In primary human AML cells, downregulation of SALL4 led to decreased HOXA9 expression and enhanced apoptosis. We found that SALL4 bound a specific region of the HOXA9 promoter in leukemic cells. SALL4 overexpression led to enhanced binding of histone activation markers at the HOXA9 promoter region, as well as increased HOXA9 expression in these cells. Furthermore, we observed that SALL4 interacted with mixed-lineage leukemia (MLL) and co-occupied the HOXA9 promoter region with MLL in AML leukemic cells, which suggests that a SALL4/MLL pathway may control HOXA9 expression. In summary, our findings revealed a molecular mechanism for SALL4 function in leukemogenesis and suggest that targeting of the SALL4/MLL/HOXA9 pathway would be an innovative approach in treating AML.

Authors

Ailing Li, Youyang Yang, Chong Gao, Jiayun Lu, Ha-Won Jeong, Bee H. Liu, Ping Tang, Xiaopan Yao, Donna Neuberg, Gang Huang, Daniel G. Tenen, Li Chai

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Figure 6

Identification of a SALL4 DNA binding site in the promoter region of HOXA9 by EMSA assays.

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Identification of a SALL4 DNA binding site in the promoter region of HOX...
(A) Human HOXA9 promoter region. Corresponding locations of amplicons for qPCR and oligo probes for EMSA are indicated. Left: 3 probe sequences. Right: Mutant probe sequences of probe 3. (B) EMSAs were performed to identify the SALL4 DNA binding cells to the HOXA9 promoter region using nuclear extracts from 293T cells transfected with a SALL4 expression construct. Of 3 pairs of oligonucleotide sequences, only probe 3 was specifically bound by SALL4 protein (lane 8); however, this shift could be prevented by competition from 200-fold excess of nonlabeled probe (lane 9). (C) Endogenous SALL4 from THP1 nuclear extracts bound probe 3 specifically (lanes 1–3). Lanes 4–6 show nuclear extracts from 293T-SALL4 as a positive control. (D) SALL4 antibody abolished SALL4 and probe 3 binding (lane 4), but not IgG control antibody (lane 5). (E) Among the 5 mutant probes, only mutant probe 2 (lane 5) failed to inhibit wild-type probe 3 binding to SALL4 protein.