Hoxa9 and Meis1 are key targets for MLL-ENL-mediated cellular immortalization.
MLL fusion proteins are oncogenic transcription factors that are associated with aggressive lymphoid and myeloid leukemias. We constructed an inducible MLL fusion, MLL-ENL-ERtm, that rendered the transcriptional and transforming properties of MLL-ENL strictly dependent on the presence of 4-hydroxy-tamoxifen. MLL-ENL-ERtm-immortalized hematopoietic cells required 4-hydroxy-tamoxifen for continuous growth and differentiated terminally upon tamoxifen withdrawal. Microarray analysis performed on these conditionally transformed cells revealed Hoxa9 and Hoxa7 as well as the Hox coregulators Meis1 and Pbx3 among the targets upregulated by MLL-ENL-ERtm. Overexpression of the Hox repressor Bmi-1 inhibited the growth-transforming activity of MLL-ENL. Moreover, the enforced expression of Hoxa9 in combination with Meis1 was sufficient to substitute for MLL-ENL-ERtm function and to maintain a state of continuous proliferation and differentiation arrest. These results suggest that MLL fusion proteins impose a reversible block on myeloid differentiation through aberrant activation of a limited set of homeobox genes and Hox coregulators that are consistently expressed in MLL-associated leukemias.
Zeisig
Bernd B
BB
Department of Genetics, University Erlangen, Staudtstrasse 5, 91058 Erlangen, Germany.
Milne
Tom
T
García-Cuéllar
María-Paz
MP
Schreiner
Silke
S
Martin
Mary-Ellen
ME
Fuchs
Uta
U
Borkhardt
Arndt
A
Chanda
Sumit K
SK
Walker
John
J
Soden
Richard
R
Hess
Jay L
JL
Slany
Robert K
RK
D000818:Animals; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D007938:Leukemia / Q000235:genetics / Q000378:metabolism; D051379:Mice; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D051788:Myeloid-Lymphoid Leukemia Protein; D009363:Neoplasm Proteins / Q000235:genetics*; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000494:pharmacology; D015854:Up-Regulation
D018398:Homeodomain Proteins; C000616391:MEIS1 protein, human; C425207:MLL-ENL oncoprotein, human; C000616392:Meis1 protein, mouse; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins; D015514:Oncogene Proteins, Fusion; D011960:Receptors, Estrogen; C097899:homeobox protein HOXA9; D013629:Tamoxifen; D051788:Myeloid-Lymphoid Leukemia Protein; C016601:afimoxifene