AUTHOR=Bao Guangcheng , Sun Jun , Zheng Helin , Hou Jingxin , Huang Jie , Wei Jie , Fu Yuanqiao , Qiu Jiawen , Zou Xuefeng , Xiang Bin , Cai Jinhua TITLE=Visualization of microRNA-21 Dynamics in Neuroblastoma Using Magnetic Resonance Imaging Based on a microRNA-21-Responsive Reporter Gene JOURNAL=Frontiers in Oncology VOLUME=11 YEAR=2021 URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2021.747305 DOI=10.3389/fonc.2021.747305 ISSN=2234-943X ABSTRACT=Background

MicroRNAs (miRs) have been shown to be closely associated with the occurrence and development of tumors and to have potential as diagnostic and therapeutic targets. The detection of miRs by noninvasive imaging technology is crucial for deeply understanding their biological functions. Our aim was to develop a novel miR-21-responsive gene reporter system for magnetic resonance imaging (MRI) visualization of the miR-21 dynamics in neuroblastoma.

Methods

The reporter gene ferritin heavy chain (FTH1) was modified by the addition of 3 copies of the sequence completely complementary to miR-21 (3xC_miR-21) to its 3’-untranslated region (3’ UTR) and transduced into SK-N-SH cells to obtain SK-N-SH/FTH1-3xC_miR-21 cells. Then, the antagomiR-21 was delivered into cells by graphene oxide functionalized with polyethylene glycol and dendrimer. Before and after antagomiR-21 delivery, FTH1 expression, MRI contrast and intracellular iron uptake were assayed in vitro and in vivo.

Results

In the SK-N-SH/FTH1-3xC_miR-21 cells, FTH1 expression was in an “off” state due to the combination of intratumoral miR-21 with the 3’ UTR of the reporter gene. AntagomiR-21 delivered into the cells bound to miR-21 and thereby released it from the 3’ UTR of the reporter gene, thus “switching on” FTH1 expression in a dose-dependent manner. This phenomenon resulted in intracellular iron accumulation and allowed MRI detection in vitro and in vivo.

Conclusion

MRI based on the miR-21-responsive gene reporter may be a potential method for visualization of the endogenous miR-21 activity in neuroblastoma and its response to gene therapy.