Mesenchymal Stem Cells‐Based Targeting Delivery System: Therapeutic Promises and Immunomodulation against Tumor

The inherent homing ability toward tumor sites of mesenchymal stem cells (MSCs) after systemic delivery has, during the past decade, created an impetus to develop these stem cells as living carriers for successful tumor‐targeted therapy. Nevertheless, the controversies about the role of MSCs in promoting or inhibiting tumor progress are impeding the potential clinical application of this system, which is partly due to the contradictory immunomodulation capability. Therefore, in this review, updated progress in the applications of MSCs as the cellular carrier for tumor‐targeting therapy, are summarized. In addition, the immunomodulating capability of MSCs and its influences on tumor progress and metastasis are highlighted. Finally, the advantages and potential risks of MSCs concerning their modulation of immune responses and the factors determining their immune properties are emphasized. It is hoped that the challenges surrounding the impacts on immune response induced by the administration of MSCs summarized in this review will provide a critical guidance for the rational design and proper application of MSCs‐based targeting delivery system for tumor therapy. Mesenchymal stem cells‐based targeting delivery system (MSCs‐TDDS) has shown enormous potential in tumor therapy for highly selective tumor elimination. The current progress and superiority of MSCs‐TDDS are highlighted. Also, concerns about the immunomodulatory effects of MSCs on tumorigenesis are addressed, and the impacts of immune suppression or activation by MSCs are thoroughly summarized and discussed.