Abstract
Mesenchymal stem cells (MSCs) have been studied for their potential in facilitating tumor-targeted delivery of chemotherapeutics due to their tumor-homing characteristics. We hypothesized that targeting effectiveness of MSCs can be further enhanced by incorporating tumor-targeting ligands on MSC surfaces that will allow for enhanced arrest and binding within the tumor tissue. We utilized a unique strategy of modifying MSCs with synthetic antigen receptors (SARs), targeting specific antigens overexpressed on cancer cells. MSCs were surface-functionalized by first incorporating recombinant protein G (PG) on the surface, followed by binding of the targeting antibody to the PG handle. We functionalized MSCs with antibodies targeting a tyrosine kinase transmembrane receptor protein, epidermal growth factor receptor (EGFR), overexpressed in non-small-cell lung cancer (NSCLC). The efficacy of MSCs functionalized with anti-EGFR antibodies (cetuximab and D8) was determined in murine models of NSCLC. Cetuximab-functionalized MSCs demonstrated improved binding to EGFR protein and to EGFR overexpressing A549 lung adenocarcinoma cells. Further, cetuximab-functionalized MSCs loaded with paclitaxel nanoparticles were efficient in slowing orthotopic A549 tumor growth and improving the overall survival relative to that of other controls. Biodistribution studies revealed a six-fold higher retention of EGFR-targeted MSCs than non-targeted MSCs. Based on these results, we conclude that targeting ligand functionalization could be used to enhance the concentration of therapeutic MSC constructs at the tumor tissue and to achieve improved antitumor response.