miR-34a induces the downregulation of both E2F1 and B-Myb oncogenes in leukemic cells.

Abstract

PURPOSE:

To elucidate new molecular mechanisms able to downregulate the mRNA levels of key oncogenes, such as B-Myb and E2F1, in a therapeutic perspective.

EXPERIMENTAL DESIGN:

B-Myb and E2F1 mRNA levels were evaluated in primary B chronic lymphocytic leukemia (B-CLL, n = 10) and acute myeloid leukemia (AML, n = 5) patient cells, in a variety of p53(wild-type) and p53(mutated/deleted) leukemic cell lines, as well as in primary endothelial cells and fibroblasts. Knockdown experiments with siRNA for p53 and E2F1 and overexpression experiments with miR34a were conducted to elucidate the role of these pathways in promoting B-Myb downregulation.

RESULTS:

In vitro exposure to Nutlin-3, a nongenotoxic activator of p53, variably downregulated the expression of B-Myb in primary leukemic cells and in p53(wild-type) myeloid (OCI, MOLM) and lymphoblastoid (SKW6.4, EHEB) but not in p53(mutated) (NB4, BJAB, MAVER) or p53(deleted) (HL-60) leukemic cell lines. The transcriptional repression of B-Myb was also observed in primary normal endothelial cells and fibroblasts. B-Myb downregulation played a critical role in the cell-cycle block in G(1) phase induced by Nutlin-3, as shown by transfection experiments with specific siRNA. Moreover, we have provided experimental evidence suggesting that miR-34a is a central mediator in the repression of B-Myb both directly and through E2F1.

CONCLUSIONS:

Owing to the role of B-Myb and E2F1 transcription factors in controlling cell-cycle progression of leukemic cells, the downregulation of these oncogenes by miR-34a suggests the usefulness of therapeutic approaches aimed to modulate the levels of miR-34a.

• Authors: Giorgio Zauli, Rebecca Voltan, Maria Grazia di Iasio, Raffaella Bosco, Elisabetta Melloni, Maria Elena Sana, Paola Secchiero
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 17 Issue 9 Pg. 2712-24 (May 01 2011) ISSN: 1557-3265 [Electronic] United States
• PMID: 21367750 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: ©2011 AACR.

Chemical References

• Cell Cycle Proteins
• E2F1 Transcription Factor
• Imidazoles
• MIRN34 microRNA, human
• MYBL2 protein, human
• MicroRNAs
• Piperazines
• Trans-Activators
• nutlin 3

Topics

• Base Sequence
• Cell Cycle Proteins (genetics, metabolism)
• Cell Line, Tumor
• Cells, Cultured
• Down-Regulation (drug effects, genetics)
• E2F1 Transcription Factor (genetics, metabolism)
• Gene Expression Regulation, Leukemic (drug effects, genetics)
• HCT116 Cells
• HL-60 Cells
• Humans
• Imidazoles (pharmacology)
• Leukemia (genetics, pathology)
• MicroRNAs (genetics, physiology)
• Models, Biological
• Oncogenes (genetics)
• Piperazines (pharmacology)
• Sequence Homology, Nucleic Acid
• Trans-Activators (genetics, metabolism)
• Transfection