Downregulation of hTERT: An Important As2O3 Induced Mechanism of Apoptosis in Myelodysplastic Syndrome

Weilai Xu,Yungui Wang,Wenbin Qian,Jie Jin,Hongyan Tong,Xuefeng Liu

doi:10.1371/journal.pone.0113199

Abstract

Two myelodysplastic syndrome (MDS) celllines, MUTZ-1 and SKM-1 cells, were used to study the effect of arsenic trioxide (As2O3) on hematological malignant cells. As2O3 induced this two cell lines apoptosis via activation of caspase-3/8 and cleavage of poly (ADP-ribose) polymerase (PARP), a DNA repair enzyme. As2O3 reduced NF-κB activity, which was important for inducing MUTZ-1 and SKM-1 cells apoptosis. As2O3 also inhibited the activities of hTERT in MUTZ-1 and SKM-1 cells. Moreover, the NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC), had no effect on caspase-8 activation, although PDTC did inhibit MUTZ-1 and SKM-1 cells proliferation. Incubation of MUTZ-1 cells with a caspase-8 inhibitor failed to block As2O3-induced inhibition of NF-κB activity. Our findings suggest that As2O3 may induce apoptosis in MUTZ-1 and SKM-1 cells by two independent pathways: first, by activation of caspase-3/8 and PARP; and second, by inhibition of NF-κB activity, which results in downregulation of hTERT expression. We conclude that hTERT and NF-κB are important molecular targets in As2O3-induced apoptosis.

Highlights

Arsenic trioxide (As2O3), an inorganic compound originally isolated and used by traditional Chinese medicine as a therapeutic reagent, is an effective drug for treating acute promyelocytic leukemia (APL) [1,2,3]
First we evaluated the effect of As2O3 on MUTZ-1 and SKM-1 cells proliferation using the MTT assay
Using cell and molecular biological approaches, we investigated the effects of As2O3 on two myelodysplastic syndromes (MDS) cell lines, MUTZ-1 and SKM-1 cells, and explored potential mechanisms for induction of apoptosis in these cells

Summary

Introduction

Arsenic trioxide (As2O3), an inorganic compound originally isolated and used by traditional Chinese medicine as a therapeutic reagent, is an effective drug for treating acute promyelocytic leukemia (APL) [1,2,3]. Numerous experimental and clinical investigations have demonstrated that As2O3 induces apoptosis in cancer cell lines, and is an effective drug in the treatment of patients with hematological. Previous studies have demonstrated that As2O3 induces apoptosis in malignant cells, such as NB4 cells (an APL cell line) and endometrial cancer cells [13,14]. In addition to inducing apoptosis, As2O3 may have an antitumor effect on endometrial carcinoma cells by inhibiting hTERT mRNA transcription and telomerase activity [14]. Further studies have shown that As2O3 inhibits NF-kB activity [15,16], which is a known transcriptional regulator of hTERT expression. Based on the evidence provided by previous studies, we speculated that As2O3-induced apoptosis involves regulation of components in signal transduction pathways, such as the hTERT and NF-kB pathways, in leukemia cells. We determined a possible molecular mechanism of As2O3-induced apoptosis by evaluating the expression levels of hTERT and NF-kB in MDS undergoing apoptosis

Methods

Results

Conclusion