MicroRNA-532 and microRNA-3064 inhibit cell proliferation and invasion by acting as direct regulators of human telomerase reverse transcriptase in ovarian cancer.

Lin Bai,Jie Bai,Luo-Ying Zhang,Hui Wang,Ai-Hua Wang,Klaus Roemer

doi:10.1371/journal.pone.0173912

Abstract

Human telomerase reverse transcriptase (hTERT) plays a crucial role in ovarian cancer (OC) progression. However, the mechanisms underlying hTERT upregulation in OC, and the specific microRNAs (miRNAs) involved in the regulation of hTERT in OC cells, remains unclear. We performed a bioinformatics search to identify potential miRNAs that bind to the 3'-untranslated region (3'-UTR) region of the hTERT mRNA. We examined the expression levels of miR-532/miR-3064 in OC tissues and normal ovarian tissues, and analyzed the correlation between miRNA expression and OC patient outcomes. The impacts of miR-532/miR-3064 on hTERT expression were evaluated by western blot analysis and hTERT 3'-UTR reporter assays. We investigated the effects of miR-532/miR-3064 on proliferation and invasion in OC cells. We found that miR-532 and miR-3064 are down-regulated in OC specimens. We observed a significant association between reduced miR-532/miR-3064 expression and poorer survival of patients with OC. We confirmed that in OC cells, these two miRNAs downregulate hTERT levels by directly targeting its 3'-UTR region, and inhibited proliferation, EMT and invasion of OC cells. In addition, the overexpression of the hTERT cDNA lacking the 3'-UTR partially restored miR-532/miR-3064-inhibited OC cell proliferation and invasion. The silencing of hTERT by siRNA oligonucleotides abolished these malignant features, and phenocopied the effects of miR-532/miR-3064 overexpression. Furthermore, overexpression of miR-532/miR-3064 inhibits the growth of OC cells in vivo. Our findings demonstrate a miR-532/miR-3064-mediated mechanism responsible for hTERT upregulation in OC cells, and reveal a possibility of targeting miR-532/miR-3064 for future treatment of OC.

Highlights

Ovarian cancer (OC) is a highly aggressive disease and represents the most lethal gynecologic tumor in the world [1, 2]
MicroRNA-532 and microRNA-3064 target Human telomerase reverse transcriptase (hTERT) in ovarian cancer human tumors, telomeres are continuously elongated by human telomerase reverse transcriptase, which adds repeat sequences of DNA to the ends of chromosomes [3]. hTERT is widely expressed in more than 85% of human tumors including OC [4], and it has been shown to promote the epithelial-to-mesenchymal transition (EMT), invasion and proliferation of OC cells [5, 6]
This study shows that miR-532 and miR-3064 that were down-regulated in OC tissues, can suppress the proliferation, EMT and invasion of OC cells by directly repressing hTERT expression

Summary

Introduction

Ovarian cancer (OC) is a highly aggressive disease and represents the most lethal gynecologic tumor in the world [1, 2]. Recent advances have implicated numerous genetic and epigenetic alterations in the underlying biology of OC metastasis. HTERT is widely expressed in more than 85% of human tumors including OC [4], and it has been shown to promote the epithelial-to-mesenchymal transition (EMT), invasion and proliferation of OC cells [5, 6]. The transcriptional factor Slug is a well-documented EMT initiator in different cancers [7, 8], and hTERT induces OC cell invasion by upregulating Slug expression [5, 9]. The siRNA-mediated knockdown of hTERT and targeted inhibition of telomerase activity using the telomerase inhibitor BIBR1532 decreased hTERT expression and inhibited the proliferation and invasion of tumor cells [10, 11]

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Conclusion