Arsenic Trioxide Suppresses the Expression of EVI-1 Gene and Regulates Related Hematopoietic Transcription Factors in THP-1 Cells

Introduction

Acute myeloid leukemia (AML) is a malignant clonal hematopoietic stem cell disease. Ecotropic viral integration site-1(EVI-1) has been recognized as one of the most dominant oncogenes associated with murine and human myeloid leukemia. EVI-1 harbors several hallmark functions that are normally associated with leukemogenesis. Overexpression EVI-1 upregulates the transcription of the transcription factor gene GATA-2, which plays a critical role in the maintenance of hematopoietic stem cells.EVI-1 also binds to the transcription factors GATA-1,PU.1,RUNX-1,SCL and LMO2 thereby inhibiting their activity and blocking the differentiation of hematopoietic progenitors. Arsenic trioxide (ATO), which was used as a traditional Chinese medicine, has shown excellent therapeutic efficiency for acutepromyelocyticleukemia. A previous study has demonstrated that ATO targets EVI-1 protein to induce apoptosis . However, the molecular mechanisms underlying this regulation of AML cells by ATO have not been fully elucidated. We aim to expand our understanding of the cellular regulation and effect of ATO on EVI-1 and several related transcription factors (such as GATA1, GATA2, RUNX-1, LMO2, PU-1) in human acute monocytic leukemia THP-1 cells.

Methods

The endogenous expression of EVI-1 is higher in THP-1 cells, which was confirmed through gene analysis sequencing and comparison with Genbank.THP-1 cells were treated with various concentrations of ATO( 0,1,3,5¦ÌM) for 24h, 48h and 72h. Expressions of EVI-1,and related transcription factor genes(GATA-2 ,GATA-1, RUNX-1,MPO,LMO,PU.1,SCL2) were determined by qRT-PCR.

Results

Compared to controls, THP-1 cells with high expression of EVI-1 gene were selected to confirm that overexpression of EVI-1 can promote the expression of GATA-2 , and reduce the level of GATA-1, RUNX-1, MPO, LMO, PU.1, SCL2 simultaneously in vitro(Fig.1).To determine whether ATO is able to directly regulate EVI-1 and related transcription factor genes expression in THP-1 cells, we examined their mRNA expression by qRT-PCR after treatment with different concentrations of ATO. We found that ATO has the ability to down regulate EVI-1 gene in a dose-dependent and time-dependent manner( Fig.2a).Moreover, GATA-2 gene expression decreased when THP-1 cells were treated with ATO(Fig.2b). We examined the related transcription factors expression and found that ATO suppressed the expression levels of PU.1, RUNX-1, SCL and LMO2 (Fig.2c, 2d, 2e) in THP-1 cells. Interestingly, exposure to increasing concentrations of ATO for increasing lengths of time was associated with gradual promotion in the expression of GATA-1 mRNA( Fig 2f).

Summary

We verified that the endogenous expression of EVI-1 is higher in THP-1 cells, which confirmed THP-1 cells can be a vitro model to investigate EVI-1 gene functions. Meanwhile, related transcription factor gene GATA-2, which is regarded as EVI-1 regulatory element, is upregulated in THP-1 cells. Moreover, GATA-1, which is essential for erythroid differentiation, and other related transcription factor genes (PU.1, RUNX-1, SCL and LMO2) decreased in THP-1 cells. ATO dose-and time-dependently decreased expressions of EVI-1 and GATA-2 gene and regulated those related transcription factors in EVI-1-overexpressing cells compared with control cells.

Disclosure: No relevant conflicts of interest to declare.