646. Utilization of Human Mesenchymal Stem Cells for Delivery of Targeted Oncolytic Adenoviruses into Orthotopic Lung Tumors
Authors: Tanja Hakkarainen, Merja Särkioja, Petri Lehenkari, Susanna Miettinen, Timo Ylikomi, Anna Kanerva, Akseli Hemminki
Journal: Molecular Therapy (2006)

Background: Conditionally replicative adenoviruses (CRAds) are widely studied tools for cancer gene therapy. The utility of CRAds is based on their ability to destroy tumor by oncolysis. Unfortunately, systemic adenoviral delivery into tumors and metastases is currently inefficient due to liver sequestration of intravenous virus and a neutralizing antibody response that hinders readministration. One potential solution for improving tumor targeting might be to engineer cells as viral carriers, thereby combining cellular tropism for tumors with the oncolytic effect provided by CRAds.Aim: The aim of the project is to utilize human mesenchymal stem cells (hMSC) as CRAd carriers. Specifically, we'll investigate the capacity of capsid modified adenoviruses to infect and replicate in hMSCs. Further, biodistribution, tumor homing ability and tumor killing efficacy of CRAd loaded hMSCs in orthotopic murine models will be evaluated.Methods: Bone marrow and fat tissue derived mesenchymal stem cells were transduced with Ad3 receptor, αvβ integrin and heparan sulphate proteoglycan (HSPG) targeted luciferase expressing replication deficient adenoviruses. Transduction efficiencies were determined with luciferase assay. In order to study the viral replication rates in hMSCs, cells were infected with panel of capsid modified Δ24-based CRAds and analyzed with MTS assay.Results: HSPG and αvβ integrin targeted viruses enhanced the transduction efficiencies up to 900 and 200 times in bone marrow derived hMSCs and up to 10000 and 1000 times in fat tissue derived hMSCs, respectively, when compared to control Ad5 virus. Also, a minor infectivity enhancement was seen with Ad3 targeted virus. When viral replication was studied, the obtained results were parallel to transduction efficiency data. In comparison to wild type virus, HSPG and αvβ integrin targeted CRAds showed significantly higher replication rates. Although Ad3 targeting did not remarkably improve transduction efficiency, it enhanced viral replication when compared to wild type virus.Cocnlusions: Infectivity of hMSCs can be significantly enhanced via targeting of viruses to αvβ integrins and HSPGs. Furthermore, hMSCs are capable of supporting replication and viral release of infectivity enhanced CRAds. Thus, these preliminary in vitro results suggests, that hMSCs could be a potentially powerful tool in delivering genes to tumors. Next, the potency of CRAd loaded hMSCs in vivo will be evaluated in an orthotopic lung cancer model. Background: Conditionally replicative adenoviruses (CRAds) are widely studied tools for cancer gene therapy. The utility of CRAds is based on their ability to destroy tumor by oncolysis. Unfortunately, systemic adenoviral delivery into tumors and metastases is currently inefficient due to liver sequestration of intravenous virus and a neutralizing antibody response that hinders readministration. One potential solution for improving tumor targeting might be to engineer cells as viral carriers, thereby combining cellular tropism for tumors with the oncolytic effect provided by CRAds. Aim: The aim of the project is to utilize human mesenchymal stem cells (hMSC) as CRAd carriers. Specifically, we'll investigate the capacity of capsid modified adenoviruses to infect and replicate in hMSCs. Further, biodistribution, tumor homing ability and tumor killing efficacy of CRAd loaded hMSCs in orthotopic murine models will be evaluated. Methods: Bone marrow and fat tissue derived mesenchymal stem cells were transduced with Ad3 receptor, αvβ integrin and heparan sulphate proteoglycan (HSPG) targeted luciferase expressing replication deficient adenoviruses. Transduction efficiencies were determined with luciferase assay. In order to study the viral replication rates in hMSCs, cells were infected with panel of capsid modified Δ24-based CRAds and analyzed with MTS assay. Results: HSPG and αvβ integrin targeted viruses enhanced the transduction efficiencies up to 900 and 200 times in bone marrow derived hMSCs and up to 10000 and 1000 times in fat tissue derived hMSCs, respectively, when compared to control Ad5 virus. Also, a minor infectivity enhancement was seen with Ad3 targeted virus. When viral replication was studied, the obtained results were parallel to transduction efficiency data. In comparison to wild type virus, HSPG and αvβ integrin targeted CRAds showed significantly higher replication rates. Although Ad3 targeting did not remarkably improve transduction efficiency, it enhanced viral replication when compared to wild type virus. Cocnlusions: Infectivity of hMSCs can be significantly enhanced via targeting of viruses to αvβ integrins and HSPGs. Furthermore, hMSCs are capable of supporting replication and viral release of infectivity enhanced CRAds. Thus, these preliminary in vitro results suggests, that hMSCs could be a potentially powerful tool in delivering genes to tumors. Next, the potency of CRAd loaded hMSCs in vivo will be evaluated in an orthotopic lung cancer model.