trichostatin-a and Leukemia--Myelomonocytic--Acute

Histone deacetylase (HDAC)-dependent transcriptional repression of the retinoic acid (RA)-signaling pathway underlies the differentiation block of acute promyelocytic leukemia. RA treatment relieves transcriptional repression and triggers differentiation of acute promyelocytic leukemia blasts, leading to disease remission. We report that transcriptional repression of RA signaling is a common mechanism in acute myeloid leukemias (AMLs). HDAC inhibitors restored RA-dependent transcriptional activation and triggered terminal differentiation of primary blasts from 23 AML patients. Accordingly, we show that AML1/ETO, the commonest AML-associated fusion protein, is an HDAC-dependent repressor of RA signaling. These findings relate alteration of the RA pathway to myeloid leukemogenesis and underscore the potential of transcriptional/differentiation therapy in AML.

Topics: Acetylation; Antineoplastic Agents; Cell Differentiation; Core Binding Factor Alpha 2 Subunit; Enzyme Inhibitors; Gene Expression Regulation, Leukemic; Histone Deacetylase Inhibitors; Histone Deacetylases; Histones; Humans; Hydroxamic Acids; Leukemia, Myeloid, Acute; Leukemia, Myelomonocytic, Acute; Oncogene Proteins, Fusion; RUNX1 Translocation Partner 1 Protein; Signal Transduction; Transcription Factors; Transcriptional Activation; Tretinoin; Tumor Cells, Cultured

t(8;21) and t(16;21) create two fusion proteins, AML-1-ETO and AML-1-MTG16, respectively, which fuse the AML-1 DNA binding domain to putative transcriptional corepressors, ETO and MTG16. Here, we show that distinct domains of ETO contact the mSin3A and N-CoR corepressors and define two binding sites within ETO for each of these corepressors. In addition, of eight histone deacetylases (HDACs) tested, only the class I HDACs HDAC-1, HDAC-2, and HDAC-3 bind ETO. However, these HDACs bind ETO through different domains. We also show that the murine homologue of MTG16, ETO-2, is also a transcriptional corepressor that works through a similar but distinct mechanism. Like ETO, ETO-2 interacts with N-CoR, but ETO-2 fails to bind mSin3A. Furthermore, ETO-2 binds HDAC-1, HDAC-2, and HDAC-3 but also interacts with HDAC-6 and HDAC-8. In addition, we show that expression of AML-1-ETO causes disruption of the cell cycle in the G(1) phase. Disruption of the cell cycle required the ability of AML-1-ETO to repress transcription because a mutant of AML-1-ETO, Delta469, which removes the majority of the corepressor binding sites, had no phenotype. Moreover, treatment of AML-1-ETO-expressing cells with trichostatin A, an HDAC inhibitor, restored cell cycle control. Thus, AML-1-ETO makes distinct contacts with multiple HDACs and an HDAC inhibitor biologically inactivates this fusion protein.

Topics: Amino Acid Sequence; Animals; Binding Sites; Cell Line; Core Binding Factor Alpha 2 Subunit; DNA-Binding Proteins; Enzyme Inhibitors; Histone Deacetylase Inhibitors; Histone Deacetylases; Hydroxamic Acids; Leukemia, Myelomonocytic, Acute; Mice; Models, Genetic; Molecular Sequence Data; Nuclear Proteins; Nuclear Receptor Co-Repressor 1; Oncogene Proteins, Fusion; Protein Structure, Tertiary; Proto-Oncogene Proteins; Repressor Proteins; RUNX1 Translocation Partner 1 Protein; Sequence Homology, Amino Acid; Sin3 Histone Deacetylase and Corepressor Complex; Transcription Factors; Transcription, Genetic; Translocation, Genetic