Email updates

Keep up to date with the latest news and content from BMC Cancer and BioMed Central.

Open Access Highly Accessed Research article

MicroRNA-34a is a tumor suppressor in choriocarcinoma via regulation of Delta-like1

Ronald TK Pang12, Carmen ON Leung1, Cheuk-Lun Lee12, Kevin KW Lam1, Tian-Min Ye1, Philip CN Chiu12 and William SB Yeung12*

Author Affiliations

1 Department of Obstetrics and Gynaecology, The University of Hong Kong, Pokfulam Road, Hong Kong, China

2 Center for Reproduction, Development and Growth, The University of Hong Kong, Pokfulam Road, Hong Kong, China

For all author emails, please log on.

BMC Cancer 2013, 13:25  doi:10.1186/1471-2407-13-25

Published: 18 January 2013

Abstract

Background

Choriocarcinoma is a gestational trophoblastic tumor which causes high mortality if left untreated. MicroRNAs (miRNAs) are small non protein-coding RNAs which inhibit target gene expression. The role of miRNAs in choriocarcinoma, however, is not well understood. In this study, we examined the effect of miR-34a in choriocarcinoma.

Methods

MiR-34a was either inhibited or ectopically expressed transiently in two choriocarcinoma cell lines (BeWo and JEG-3) respectively. Its actions on cell invasion, proliferation and colony formation at low cell density were examined. The miR-34a putative target Notch ligand Delta-like 1 (DLL1) was identified by adoption of different approaches including: in-silico analysis, functional luciferase assay and western blotting. Real-time quantitative polymerase chain reaction was used to quantify changes in the expression of matrix proteinase in the treated cells. To nullify the effect of miR-34a ectopic expression, we activated Notch signaling through force-expression of the Notch intracellular domain in the miR-34a force-expressed cells. In addition, we studied the importance of DLL1 in BeWo cell invasion through ligand stimulation and antibody inhibition. Furthermore, the induction in tumor formation of miR-34a-inhibited BeWo cells in SCID mice was investigated.

Results

Transient miR-34a force-expression significantly suppressed cell proliferation and invasion in BeWo and JEG-3 cells. In silicon miRNA target prediction, luciferase functional assays and Western blotting analysis demonstrated that miR-34a regulated DLL1 expression in both cell lines. Although force-expression of miR-34a suppressed the expression of DLL1 and NOTCH1, the extent of suppression was higher in DLL1 than NOTCH1 in both cell lines. MiR-34a-mediated DLL1 suppression led to reduced matrix metallopeptidase 9 and urokinase-type plasminogen activator expression. The effect of miR-34a on cell invasion was partially nullified by Notch signaling activation. DLL1 ligand stimulated while anti-DLL1 antibody treatment suppressed cell invasion. Mice inoculated with BeWo cells transfected with miR-34a inhibitor had significantly larger xenografts and stronger DLL1 expression than those with cells transfected with the control inhibitor.

Conclusions

MiR-34a reduced cell proliferation and invasiveness, at least, partially through its inhibitory effect on DLL1.

Keywords:
miR-34a; DLL1; Choriocarcinoma; Invasion; Notch