Late-phase miRNA-controlled oncolytic adenovirus for selective killing of cancer cells

Area of Science:

• Oncolytic Virotherapy
• Molecular Virology
• Gene Therapy

Background:

• Adenoviruses are engineered for cancer therapy, with miRNA targeting of early genes improving tumor specificity.
• Current strategies focus on regulating early viral genes for tissue-specific detargeting.

Purpose of the Study:

• To investigate the feasibility of regulating late viral genes, specifically the fiber protein (L5), using microRNA (miRNA) for adenoviral tissue-specific selectivity.
• To engineer an adenovirus (Ad-L5-8miR148aT) with miRNA target sites in the 3'UTR of the L5 gene.

Main Methods:

• Engineered Ad-L5-8miR148aT with eight miR-148a binding sites in the L5 3'UTR.
• Evaluated miRNA-dependent regulation in vitro through viral release assays and serial infections.
• Assessed in vivo efficacy and safety in mouse models, including patient-derived xenografts.

Main Results:

• In vitro, miR-148a regulation reduced viral fiber expression by 70% and viral release by 10,000-fold after serial infections.
• In vivo, liver production of infectious viral particles was significantly impaired.
• Ad-L5-8miR148aT showed reduced hepatotoxicity, retained lytic activity in cancer cells, and demonstrated potent anti-tumor responses.

Conclusions:

• MicroRNA control of late viral proteins is a viable strategy for achieving tissue-specific selectivity in adenoviruses.
• This novel approach enhances adenovirus safety by reducing off-target effects in healthy tissues.
• Regulating late gene expression offers a new avenue for developing safer and more effective oncolytic adenoviruses.