Implications: This report describes a novel role for HDAC1 as a cofactor for the leukemogenic fusion protein CBFb-SMMHC and shows that inhibitors of HDAC1 effectively target leukemia cells expressing the fusion protein in vivo.
Acute myeloid leukemia (AML) is often characterized by the presence of specific, recurrent chromosomal abnormalities. One of the most common aberrations, inversion of chromosome 16 [inv(16)], generates the fusion oncogene CBFB-MYH11. Previously, we used a mouse knock-in model to show that Cbfb-MYH11 induces changes in gene expression and results in the accumulation of abnormal myeloid cells, a subset of which are enriched for leukemia stem cell (LSC) activity. One gene upregulated by Cbfb-MYH11 encodes the cytokine receptor IL1RL1 (ST2). IL1RL1 and its ligand IL-33 are known regulators of mature myeloid cells, but their roles in AML are not known. Here, we use Cbfb-MYH11 knock-in mice to show that IL1RL1 is expressed by cell populations with high LSC activity, and that the cell surface expression of IL1RL1 is dynamic, implying that the expression of IL1RL1 is not restricted to a specific stage of differentiation. We also show that treatment with IL-33 increased serial replating ability and expression of pro-survival proteins in vitro. Finally, we show that IL1RL1+ cells can survive chemotherapy better than IL1RL1− cells in vivo. Collectively, our results indicate that IL1RL1 is dynamically expressed in Cbfb-MYH11+ leukemia cells and promotes their survival.
Approximately 10% of cases of childhood cancer arise in the context of a cancer predisposition syndrome (CPS) [1]. Among the rare CPS, Li-Fraumeni syndrome (LFS, MIM#151623) is relatively common and estimated to account for >1% of cases of childhood cancer [2]. LFS is a dominantly inherited condition caused by pathogenic germline variants in the TP53 tumor suppressor gene [3, 4]. Children with LFS are predisposed to a range of neoplasms such as osteosarcoma, adrenocortical carcinoma, medulloblastoma, choroid plexus carcinoma, anaplastic rhabdomyosarcoma, and (frequently hypodiploid) acute lymphoblastic leukemia (LFS-ALL) [5, 6]. Notably,
Inversion of chromosome 16 (inv(16)) generates the CBFβ-SMMHC fusion protein and is found in nearly all patients with acute myeloid leukemia subtype M4 with Eosinophilia (M4Eo). Expression of CBFβ-SMMHC is causative for leukemia development, but the molecular mechanisms underlying its activity are unclear. Recently, there have been important advances in defining the role of CBFβ-SMMHC and its binding partners, the transcription factor RUNX1 and the histone deacetylase HDAC8. Importantly, initial trials demonstrate that small molecules targeting these binding partners are effective against CBFβ-SMMHC induced leukemia. This review will discuss recent advances in defining the mechanism of CBFβ-SMMHC activity, as well as efforts to develop new therapies for inv(16) AML.
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