MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene expression by inhibiting the translation of target transcripts. The expression profiles of miRNAs vary in different tissues and change with the development of diseases, including cancer. This feature has begun to be used for the modification of oncolytic viruses (OVs) in order to increase their selectivity and efficacy. OVs represent a relatively new class of anticancer drugs; they are designed to replicate in cancer tumors and destroy them. These can be natural viruses that can replicate within cancer tumor cells, or recombinant viruses created in laboratories. There are some concerns regarding OVs’ toxicity, due to their ability to partially replicate in healthy tissues. In addition, lytic and immunological responses upon OV therapy are not always sufficient, so various OV editing methods are used. This review discusses the latest results of preclinical and clinical studies of OVs, modifications of which are associated with the miRNA-mediated mechanism of gene silencing.

Background: Glioblastoma (GBM) is characterised by therapeutic resistance and high invasiveness, so the development of new treatments is essential. Oncolytic virotherapy using the vesicular stomatitis virus (VSV) is a promising approach as it is inherently tumour-selective and immunostimulatory. This study evaluated the antitumour efficacy of a recombinant VSV engineered to co-express mouse interleukin-12 and granulocyte-macrophage colony-stimulating factor (rVSV-dM51-mIL12-mGMCSF) using in vitro and in vivo U-87 MG models. Methods: The oncolytic activity of rVSV-dM51-mIL12-mGMCSF was evaluated in vitro against human U-87 MG and mouse GL-261 glioblastoma cells using flow cytometry (MOI 0.1) and MTT assays (MOIs 0.1 and 0.001). In vivo, tumour progression was monitored in U-87 MG xenograft mice for 30 days after inoculation. At the study endpoint, tumour tissues from treated and control animals were subjected to immunohistochemical (IHC) analysis; the H-score method was used to quantify expression of the Ki-67 proliferation marker, VSV glycoprotein (VSV-G), and mIL-12. Results: rVSV-dM51-mIL12-mGMCSF demonstrated oncolytic activity against both cell lines in vitro; however, its cytotoxicity was lower compared to the parental control virus (rVSV-dM51-GFP). In contrast, treatment in vivo resulted in greater tumour growth inhibition. IHC analysis revealed a significant reduction in the Ki-67 H-score alongside high levels of VSV glycoprotein and mIL-12 expression. These results confirm that, although the payloads do not enhance direct viral oncolysis in vitro, they significantly improve antitumour efficacy in vivo. Conclusions: rVSV-dM51-mIL12-mGMCSF effectively inhibited tumour growth in the U-87 MG xenograft model, supporting further evaluation of glioblastoma-directed oncolytic virotherapy.