The mechanisms by which AML1/ETO (A/E) fusion protein induces leukemogenesis in acute myeloid leukemia (AML) without mutagenic events remain elusive. Here we show that interactions between A/E and hypoxia-inducible factor 1α (HIF1α) are sufficient to prime leukemia cells for subsequent aggressive growth. In agreement with this, HIF1α is highly expressed in A/E-positive AML patients and strongly predicts inferior outcomes, regardless of gene mutations. Co-expression of A/E and HIF1α in leukemia cells causes a higher cell proliferation rate in vitro and more serious leukemic status in mice. Mechanistically, A/E and HIF1α form a positive regulatory circuit and cooperate to transactivate DNMT3a gene leading to DNA hypermethylation. Pharmacological or genetic interventions in the A/E-HIF1α loop results in DNA hypomethylation, a re-expression of hypermethylated tumor-suppressor p15(INK4b) and the blockage of leukemia growth. Thus high HIF1α expression serves as a reliable marker, which identifies patients with a poor prognosis in an otherwise prognostically favorable AML group and represents an innovative therapeutic target in high-risk A/E-driven leukemia.

Lack of immunogenicity of cancer cells has been considered a major reason for their failure in induction of a tumor specific T cell response. In this paper, we present evidence that decitabine (DAC), a DNA methylation inhibitor that is currently used for the treatment of myelodysplastic syndrome (MDS), acute myeloid leukemia (AML) and other malignant neoplasms, is capable of eliciting an anti-tumor cytotoxic T lymphocyte (CTL) response in mouse EL4 tumor model. C57BL/6 mice with established EL4 tumors were treated with DAC (1.0 mg/kg body weight) once daily for 5 days. We found that DAC treatment resulted in infiltration of IFN-γ producing T lymphocytes into tumors and caused tumor rejection. Depletion of CD8+, but not CD4+ T cells resumed tumor growth. DAC-induced CTL response appeared to be elicited by the induction of CD80 expression on tumor cells. Epigenetic evidence suggests that DAC induces CD80 expression in EL4 cells via demethylation of CpG dinucleotide sites in the promoter of CD80 gene. In addition, we also showed that a transient, low-dose DAC treatment can induce CD80 gene expression in a variety of human cancer cells. This study provides the first evidence that epigenetic modulation can induce the expression of a major T cell co-stimulatory molecule on cancer cells, which can overcome immune tolerance, and induce an efficient anti-tumor CTL response. The results have important implications in designing DAC-based cancer immunotherapy.

Purpose: Whether isocitrate dehydrogenase (IDH) gene aberrations affected prognosis of patients with acute myeloid leukemia (AML) was controversial. Here, we conducted a meta-analysis to evaluate their prognostic value.Experimental Design: PubMed, Embase, Cochrane, and Chinese databases were searched to identify studies exploring how IDH gene aberrations affected AML outcome. Pooled HRs and relative risks (RR) were calculated, along with 95% confidence intervals (CI).Results: Thirty-three reports were included.

Acute erythroid leukemia (AEL), characterized by a predominant erythroid proliferation, is a subtype of acute myelogenous leukemia. The genetic basis of AEL remains poorly defined. Through whole-exome sequencing, we identified high frequencies of mutations in CEBPA (32.7%), GATA2 (22.4%), NPM1 (15.5%), SETBP1 (12.1%) and U2AF1 (12.1%). Structure prediction analysis revealed that most of the GATA2 mutations were located at the DNA-binding N-terminal zinc-finger near the DNA-binding interface, suggesting that mutations could result in at least partial inactivation of GATA2 protein. On co-transfection of a GATA-responsive reporter construct together with plasmids expressing either GATA2 wild-type or GATA2 ZF1 mutants (P304H, L321P and R330X) in 293T cells, we found a reduced transcriptional activation in cells transfected with GATA2 mutants. To determine whether reduced GATA2 function is involved in leukemogenesis of AEL, we transfected 32D cells with GATA2 mutants and evaluated the impact of GATA2 mutations on erythroid differentiation. Our data revealed an increased expression of erythroid-related antigens Ter-119, β-globin and βh1-globin, as well as increased hemoglobin positivity in 32D cells transfected with GATA2 mutants compared with control cells. Our results suggest that the decline of GATA2 resulting from mutations contributes to the erythroid commitment, differentiation and the development of AEL.

No abstract