ABSTRACT
Acute graft-versus-host disease (aGVHD) remains a major complication of allogeneic hematopoietic stem cell transplant (alloHSCT), underscoring the need to further elucidate its mechanisms and develop novel treatments. Based on recent observations that microRNA-155 (miR-155) is up-regulated during T-cell activation, we hypothesized that miR-155 is involved in the modulation of aGVHD. Here we show that miR-155 expression was up-regulated in T cells from mice developing aGVHD after alloHSCT. Mice receiving miR-155-deficient donor lymphocytes had markedly reduced lethal aGVHD, whereas lethal aGVHD developed rapidly in mice recipients of miR-155 overexpressing T cells. Blocking miR-155 expression using a synthetic anti-miR-155 after alloHSCT decreased aGVHD severity and prolonged survival in mice. Finally, miR-155 up-regulation was shown in specimens from patients with pathologic evidence of intestinal aGVHD. Altogether, our data indicate a role for miR-155 in the regulation of GVHD and point to miR-155 as a novel target for therapeutic intervention in this disease.
Subject(s)
Graft vs Host Disease/genetics , MicroRNAs/physiology , Acute Disease , Animals , Cells, Cultured , Female , Gene Expression Regulation/genetics , Genetic Therapy , Graft vs Host Disease/etiology , Graft vs Host Disease/metabolism , Humans , Lymphocyte Activation/genetics , Male , Mice , Mice, Inbred C57BL , Mice, Inbred DBA , Mice, Transgenic , MicroRNAs/genetics , MicroRNAs/metabolism , Spleen/cytology , Spleen/metabolism , Spleen/transplantation , T-Lymphocytes/metabolismABSTRACT
MicroRNAs (miRNAs) are associated with cytogenetics and molecular subtypes of acute myelogeneous leukemia (AML), but their impact on AML pathogenesis is poorly understood. We have previously shown that miR-29b expression is deregulated in primary AML blasts. In this work, we investigated the functional role of miR-29b in leukemogenesis. Restoration of miR-29b in AML cell lines and primary samples induces apoptosis and dramatically reduces tumorigenicity in a xenograft leukemia model. Transcriptome analysis after ectopic transfection of synthetic miR-29b into leukemia cells indicates that miR-29b target apoptosis, cell cycle, and proliferation pathways. A significant enrichment for apoptosis genes, including MCL-1, was found among the mRNAs inversely correlated with miR-29b expression in 45 primary AML samples. Together, the data support a tumor suppressor role for miR-29 and provide a rationale for the use of synthetic miR-29b oligonucleotides as a novel strategy to improve treatment response in AML.
Subject(s)
Gene Expression Regulation, Leukemic , Leukemia, Myeloid, Acute/genetics , MicroRNAs/genetics , Animals , Apoptosis/genetics , Blotting, Northern , Blotting, Western , Cell Proliferation , Female , Gene Expression , Humans , Mice , Mice, Nude , Oligonucleotide Array Sequence Analysis , Reverse Transcriptase Polymerase Chain Reaction , Transfection , Xenograft Model Antitumor AssaysABSTRACT
Aberrant DNA hypermethylation contributes to myeloid leukemogenesis by silencing structurally normal genes involved in hematopoiesis. MicroRNAs (miRNAs) are noncoding RNAs that regulate gene expression by targeting protein-coding mRNAs. Recently, miRNAs have been shown to play a role as both targets and effectors in gene hypermethylation and silencing in malignant cells. In the current study, we showed that enforced expression of miR-29b in acute myeloid leukemia cells resulted in marked reduction of the expression of DNA methyltransferases DNMT1, DNMT3A, and DNMT3B at both RNA and protein levels. This in turn led to decrease in global DNA methylation and reexpression of p15(INK4b) and ESR1 via promoter DNA hypomethylation. Although down-regulation of DNMT3A and DNMT3B was the result of a direct interaction of miR-29b with the 3' untranslated regions of these genes, no predicted miR-29b interaction sites were found in the DNMT1 3' untranslated regions. Further experiments revealed that miR-29b down-regulates DNMT1 indirectly by targeting Sp1, a transactivator of the DNMT1 gene. Altogether, these data provide novel functional links between miRNAs and aberrant DNA hypermethylation in acute myeloid leukemia and suggest a potentially therapeutic use of synthetic miR-29b oligonucleotides as effective hypomethylating compounds.