Magnetic resonance imaging of stem cell application in oncology

There is a growing interest in using stem cells for therapeutic and diagnostic application in the field of oncology. Stem cells have the intrinsic ability to "home" towards growing tumors and are hypo-immunogenic, and, thus they are very promising vehicles of gene therapy and immunotherapy of cancer. For hematological malignancies, intravenous injection of autologous and allogeneic bone marrow suspensions, including hematopoietic progenitors, is a consolidated strategy to support the delivery of otherwise lethal doses of radiation therapy or chemotherapy. In addition, it has been demonstrated that patients who develop graft-versus-host disease have lower incidence of relapse, showing that the donor-derived immune system contributes to the eradication of leukemia. This phenomenon is due to elimination of leukemic stem cells by alloreactivity of the transplanted stem cells. The tumor-specific homing of stem cells opens the possibility of using stem cells in early cancer diagnosis. Nowadays, it is well know that tumor is a "cancer stem cells disease." Tumor stroma is composed of a variety of cells, including proliferating tumor cells, cancer stem cells, tumor fibroblasts, endothelial cells, lymphocytes and other cells, while cancer stem cells are the main component involved in tumor maintenance and progression. The possibility to in vivo identify and track cancer stem cells is of pivotal importance for cancer diagnosis and therapy response assessment. This chapter focuses primarily on the capability of using non-invasive MR imaging to (1) monitor the transplantation of therapeutic cells to the tumor sites, where these cells subsequently differentiate and proliferate; and (2) non-invasively track individual cancer cells, which is expected to provide more insight to the mechanisms of cancer development, dissemination, and responses to oncological therapies in the future.