MiR-125b, a Target of CDX2, Regulates Cell Differentiation through Repression of the Core Binding Factor in Hematopoietic Malignancies

Kang-Yu Lin,Xing-Ju Zhang,Dan-Dan Feng,Hua Zhang,Cheng-Wu Zeng,Bo-Wei Han,Ai-Dong Zhou,Liang-Hu Qu,Ling Xu,Yue-Qin Chen

doi:10.1074/jbc.m111.269670

Abstract

MicroRNA-125b (miR-125b), a small noncoding RNA molecule, has been found to be deregulated and functions as an oncogene in many cancers including hematopoietic malignancies. However, the mechanisms accounting for miR-125b dysregulation remain to be elucidated. The present study aims to identify the factors that might contribute to up-regulation of miR-125b in human hematopoietic malignancies and its downstream targets for lineage-specific differentiation. We at first reported that CDX2, a homeobox transcription factor, binds to promoter regions of the miR-125b gene and activates transcriptional regulation of miR-125b in malignant myeloid cells. We further revealed that increasing levels of CDX2 in malignant myeloid cells activate miR-125b expression, which in turn inhibits core binding factor β (CBFβ) translation, thereby counteracting myeloid cell differentiation, at least for granulocytic lineage, and promoting leukemogenesis. Interestingly, we found that this novel pathway including CDX2, miR-125b, and CBFβ was mediated by undergoing all-trans-retinoic acid induction. Once differentiation ensues with all-trans-retinoic acid treatment, CDX2 activity decreases, leading to a reduction in miR-125b transcription and up-regulation of CBFβ in myeloid cells and in patients. The study provides a new mechanism that contributes to hematopoietic malignancies, which could involve deregulation of miR-125b and its up- and downstream factors. As altered expression of miRNAs has been reported in a wide range of malignancies, delineating the underlying molecular mechanisms of aberrant miRNA expression and characterizing the upstream and downstream factors will help to understand important steps in the pathogenesis of these afflictions.

Highlights

The mechanisms account for the miR-125b dysregulation in cancer cells
The results showed that only CDX2 could stimulate the miR-125b promoter, whereas PU.1, C/EBP␣, and GATA1 did not show contributions on transcription activity (Fig. 1B, right), suggesting that CDX2 might be the activator of miR-125b
We found that the expression levels of miR-125b and CDX2 were highly expressed in all samples at diagnosis and markedly reduced in all of the diagnosis/complete remission samples compared (Fig. 5, B and C), indicating that the expression level of miR-125b mRNA positively correlates with CDX2 mRNA, and their expressions respond with all-trans-retinoic acid (ATRA) treatment

Summary

Background

Results: miR-125b, activating by CDX2, a homeobox transcription factor, regulates cell differentiation through repression of the core binding factor. We at first reported that CDX2, a homeobox transcription factor, binds to promoter regions of the miR-125b gene and activates transcriptional regulation of miR-125b in malignant myeloid cells. We further revealed that increasing levels of CDX2 in malignant myeloid cells activate miR-125b expression, which in turn inhibits core binding factor ␤ (CBF␤) translation, thereby counteracting myeloid cell differentiation, at least for granulocytic lineage, and promoting leukemogenesis. We revealed that up-regulation of miR-125b is due to activation by the homeobox transcription factor CDX2 and in turn inhibits myeloid cell differentiation. We further demonstrate that miR-125b directly targets core binding factor ␤ (CBF␤) in myeloid cells and mediated myeloid cell differentiation, at least for granulocytic lineage This pathway is activated by ATRA induction. These results shed light on the ATRA-dependent therapy mechanism and potentially provides the knowledge necessary to design novel targeted therapies for hematopoietic malignancy

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION