title: The RNA binding proteins RBM38 and DND1 are repressed in AML and have a novel function in APL differentiation.
abstract: The RNA binding proteins RBM binding motif protein 38 (RBM38) and DEAD END 1 (DND1) selectively stabilize mRNAs by attenuating RNAse activity or protecting them from micro(mi)RNA-mediated cleavage. Furthermore, both proteins can efficiently stabilize the mRNA of the cell cycle inhibitor p21(CIP1). Since acute myeloid leukemia (AML) differentiation requires cell cycle arrest and RBM38 as well as DND1 have antiproliferative functions, we hypothesized that decreased RBM38 and DND1 expression may contribute to the differentiation block seen in this disease. We first quantified RBM38 and DND1 mRNA expression in clinical AML patient samples and CD34(+) progenitor cells and mature granulocytes from healthy donors. We found significantly lower RBM38 and DND1 mRNA levels in AML blasts and CD34(+) progenitor cells as compared to mature neutrophils from healthy donors. Furthermore, the lowest expression of both RBM38 and DND1 mRNA correlated with t(8;21). In addition, neutrophil differentiation of CD34(+) cells in vitro with G-CSF (granulocyte colony stimulating factor) resulted in a significant increase of RBM38 and DND1 mRNA levels. Similarly, neutrophil differentiation of NB4 acute promyelocytic leukemia (APL) cells was associated with a significant induction of RBM38 and DND1 expression. To address the function of RBM38 and DND1 in neutrophil differentiation, we generated two independent NB4RBM38 as well as DND1 knockdown cell lines. Inhibition of both RBM38 and DND1 mRNA significantly attenuated NB4 differentiation and resulted in decreased p21(CIP1) mRNA expression. Our results clearly indicate that expression of the RNA binding proteins RBM38 and DND1 is repressed in primary AML patients, that neutrophil differentiation is dependent on increased expression of both proteins, and that these proteins have a critical role in regulating p21(CIP1) expression during APL differentiation.
authors.affiliation: Division of Experimental Pathology, Institute of Pathology, University of Bern, Bern, Switzerland; Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland. Electronic address: julianwampfler@hotmail.com.
authors.forename: Julian
authors.initials: J
authors.lastname: Wampfler
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, United States. Electronic address: federzon@scripps.edu.
authors.forename: Elena A
authors.initials: EA
authors.lastname: Federzoni
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, United States. Electronic address: betorbet@scripps.edu.
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Torbett
authors.affiliation: Department of Medical Oncology, Inselspital, Bern University Hospital, Bern, Switzerland. Electronic address: martin.fey@insel.ch.
authors.forename: Martin F
authors.initials: MF
authors.lastname: Fey
authors.affiliation: Division of Experimental Pathology, Institute of Pathology, University of Bern, Bern, Switzerland; Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland. Electronic address: mario.tschan@pathology.unibe.ch.
authors.forename: Mario P
authors.initials: MP
authors.lastname: Tschan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015153:Blotting, Western; D002454:Cell Differentiation; D005260:Female; D015973:Gene Expression Regulation, Leukemic / Q000502:physiology*; D055785:Gene Knockdown Techniques; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000473:pathology*; D015473:Leukemia, Promyelocytic, Acute / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D009504:Neutrophils / Q000473:pathology*; D016601:RNA-Binding Proteins / Q000096:biosynthesis*; D060888:Real-Time Polymerase Chain Reaction; D055815:Young Adult
chemical_list: C528453:Dnd1 protein, human; D009363:Neoplasm Proteins; C515435:RBM38 protein, human; D016601:RNA-Binding Proteins
keywords: Acute myeloid leukemia; Acute promyelocytic leukemia; DND1; Neutrophil differentiation; RBM38