ABSTRACT
Adenosine deaminase associated with RNA1 (ADAR1) deregulation contributes to therapeutic resistance in many malignancies. Here we show that ADAR1-induced hyper-editing in normal human hematopoietic progenitors impairs miR-26a maturation, which represses CDKN1A expression indirectly via EZH2, thereby accelerating cell-cycle transit. However, in blast crisis chronic myeloid leukemia progenitors, loss of EZH2 expression and increased CDKN1A oppose cell-cycle transit. Moreover, A-to-I editing of both the MDM2 regulatory microRNA and its binding site within the 3' UTR region stabilizes MDM2 transcripts, thereby enhancing blast crisis progenitor propagation. These data reveal a dual mechanism governing malignant transformation of progenitors that is predicated on hyper-editing of cell-cycle-regulatory miRNAs and the 3' UTR binding site of tumor suppressor miRNAs.
Subject(s)
Adenosine Deaminase/genetics , Blast Crisis/genetics , Cyclin-Dependent Kinase Inhibitor p21/genetics , Enhancer of Zeste Homolog 2 Protein/genetics , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics , MicroRNAs/genetics , Proto-Oncogene Proteins c-mdm2/genetics , RNA-Binding Proteins/genetics , 3' Untranslated Regions , Animals , Cell Cycle , Female , Gene Editing , Gene Expression Regulation, Neoplastic , Gene Regulatory Networks , HEK293 Cells , Humans , K562 Cells , Male , Mice , Neoplasm TransplantationABSTRACT
Post-transcriptional adenosine-to-inosine RNA editing mediated by adenosine deaminase acting on RNA1 (ADAR1) promotes cancer progression and therapeutic resistance. However, ADAR1 editase-dependent mechanisms governing leukemia stem cell (LSC) generation have not been elucidated. In blast crisis chronic myeloid leukemia (BC CML), we show that increased JAK2 signaling and BCR-ABL1 amplification activate ADAR1. In a humanized BC CML mouse model, combined JAK2 and BCR-ABL1 inhibition prevents LSC self-renewal commensurate with ADAR1 downregulation. Lentiviral ADAR1 wild-type, but not an editing-defective ADAR1(E912A) mutant, induces self-renewal gene expression and impairs biogenesis of stem cell regulatory let-7 microRNAs. Combined RNA sequencing, qRT-PCR, CLIP-ADAR1, and pri-let-7 mutagenesis data suggest that ADAR1 promotes LSC generation via let-7 pri-microRNA editing and LIN28B upregulation. A small-molecule tool compound antagonizes ADAR1's effect on LSC self-renewal in stromal co-cultures and restores let-7 biogenesis. Thus, ADAR1 activation represents a unique therapeutic vulnerability in LSCs with active JAK2 signaling.
Subject(s)
Adenosine Deaminase/metabolism , Cell Self Renewal , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/pathology , MicroRNAs/metabolism , RNA-Binding Proteins/metabolism , Adenosine Deaminase/genetics , Animals , Base Sequence , Cell Self Renewal/genetics , Fusion Proteins, bcr-abl/metabolism , Gene Expression Regulation, Leukemic , Janus Kinase 2/metabolism , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics , Mice , Neoplastic Stem Cells/metabolism , Neoplastic Stem Cells/pathology , RNA Editing/genetics , RNA-Binding Proteins/genetics , Signal Transduction/geneticsABSTRACT
ADAR (adenosine deAminase acting on RNA) editases catalyze the deamination of adenosine to inosine (A-to-I), a post-transcriptional modification that alters coding and non-coding RNA stability and function. ADAR editases such as ADAR1 have recently been shown to play a key role in normal stem cell maintenance. While ADAR mutations are associated with hereditary autoimmune diseases such as Aicardi-Goutières syndrome, ADAR copy-number alterations and editase activation have been associated with progression of a broad array of malignancies. In this review we discuss evidence linking aberrant A-to-I editing to cancer and other degenerative diseases, and the mechanisms that may be targeted by novel therapeutic strategies.
Subject(s)
Neoplasms/genetics , Neurodegenerative Diseases/genetics , RNA Editing , RNA/genetics , Adenosine Deaminase/genetics , Adenosine Deaminase/metabolism , Animals , Humans , Neoplasms/enzymology , Neoplasms/metabolism , Neurodegenerative Diseases/enzymology , Neurodegenerative Diseases/metabolism , RNA/metabolismABSTRACT
The existence and identification of adult renal stem cells is a controversial issue. In this study, renal stem cells were identified from cultures of clonal human nephrospheres. The cultured nephrospheres exhibited the activation of stem cell pathways and contained cells at different levels of maturation. In each nephrosphere the presence of 1.12-1.25 cells mirroring stem cell properties was calculated. The nephrosphere cells were able to generate three-dimensional tubular structures in 3D cultures and in vivo. In clonal human nephrospheres a PKH(high) phenotype was isolated using PKH26 epifluorescence, which can identify quiescent cells within the nephrospheres. The PKH(high) cells, capable of self-renewal and of generating a differentiated epithelial, endothelial and podocytic progeny, can also survive in vivo maintaining the undifferentiated status. The PKH(high) status, together with a CD133(+)/CD24(-) phenotype, identified a homogeneous cell population displaying in vitro self-renewal and multipotency capacity. The resident adult renal stem cell population isolated from nephrospheres can be used for the study of mechanisms that regulate self-renewal and differentiation in adult renal tissue as well as in renal pathological conditions.
