Mesenchymal stem cell-mediated delivery of an oncolytic adenovirus enhances antitumor efficacy in hepatocellular carcinoma.

Oncolytic virotherapy is a promising alternative to conventional treatment, yet systemic delivery of these viruses to tumors remains a major challenge. In this regard, mesenchymal stem cells (MSCs) with well-established tumor-homing properties could serve as a promising systemic delivery tool. In this study, we examined the feasibility of using human mesenchymal stem cells as a carrier to systemically deliver a hepatocellular carcinoma (HCC)-specific oncolytic adenovirus (HCC-oAd) in an HCC orthotopic tumor model. We showed that MSCs could be effectively infected by HCC-oAd through modification of the virus' fiber domain and that the virus replicated efficiently in the cell carrier. HCC-targeting oAd loaded in MSCs (HCC-oAd/MSC) effectively lysed HCC cells in vitro under both normoxic and hypoxic conditions as a result of the hypoxia responsiveness of HCC-oAd. Importantly, systemically administered HCC-oAd/MSC, which were initially infected with a low viral dose, homed to HCC tumors and resulted in a high level of virion accumulation in the tumors, ultimately leading to potent tumor growth inhibition. Furthermore, viral dose reduction and tumor localization of HCC-oAd/MSC prevented the induction of hepatotoxicity by attenuating HCC-oAd hepatic accumulation. Taken together, these results demonstrate that MSC-mediated systemic delivery of oAd is a promising strategy for achieving synergistic antitumor efficacy with improved safety profiles.