Chimeric Element-Regulated MRI Reporter System for Mediation of Glioma Theranostics

TL;DR

This study creates a system that uses a modified gene to improve MRI imaging and targeted drug delivery for glioma treatment.

Contribution

A novel chimeric element-regulated FTH1 system is developed for enhanced glioma imaging and therapy via TfR-mediated drug delivery.

Findings

The chimeric system significantly increased FTH1 expression and TfR upregulation in glioma cells.

Tf-LPD liposomes demonstrated TfR-dependent uptake and induced apoptosis in high-TfR cells.

In vivo, Tf-LPD reduced tumor growth and showed MR signal changes in chimeric-system xenografts.

Abstract

This study developed an FTH1 expression system regulated by chimeric elements, leveraging the mechanism whereby FTH1 overexpression induces intracellular iron deficiency to activate upregulation of transferrin receptor (TfR) expression. Through the specific binding between TfR and transferrin (Tf), the system enables targeted delivery of anti-tumor agents to glioma cells, achieving dual functions of MRI-based glioma imaging and targeted therapy.

Background and Purpose: Glioblastoma remains a therapeutic challenge with a poor prognosis despite multimodal treatments. Reporter-based magnetic resonance imaging (MRI) offers a promising approach for tumor visualization, but its efficacy depends on sufficient reporter gene expression. This study aimed to develop a chimeric element-regulated ferritin heavy chain 1 (FTH1) reporter system to enhance MRI-based glioma detection while enabling targeted therapy via transferrin receptor (TfR)-mediated drug delivery. Methods: Using gene cloning techniques, we constructed a chimeric FTH1 expression system comprising tumor-specific PEG3 promoter (transcriptional control), bFGF-2 5′UTR (translational enhancement), and WPRE (mRNA stabilization). Lentiviral vectors delivered constructs to U251 glioblastoma cells and xenografts. FTH1/TfR expression was validated by Western blot and immunofluorescence. Iron accumulation was assessed via Prussian blue staining and TEM. MRI evaluated T2 signal changes. Transferrin-modified doxorubicin liposomes (Tf-LPD) were characterized for size and drug loading and tested for cellular uptake and cytotoxicity in vitro. In vivo therapeutic efficacy was assessed in nude mouse models through tumor volume measurement, MR imaging, and histopathology. Results: The chimeric system increased FTH1 expression significantly over PEG3-only controls (p < 0.01), with an increase of nearly 1.5-fold compared to the negative and blank groups and approximately a two-fold increase relative to the single promoter group, with corresponding TfR upregulation. Enhanced iron accumulation reduced T2 relaxation times significantly (p < 0.01), improving MR contrast. Tf-LPD (115 nm, 70% encapsulation) showed TfR-dependent uptake, inducing obvious apoptosis in high-TfR cells compared with that in controls. In vivo, Tf-LPD reduced tumor growth markedly in chimeric-system xenografts versus controls, with concurrent MR signal attenuation. Conclusions: The chimeric regulatory strategy overcomes limitations of single-element systems, demonstrating significant potential for integrated glioma theranostics. Its modular design may be adaptable to other reporter genes and malignancies.

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