Mesenchymal Stem/Stromal Cell Recruitment by Central Nervous System Tumors

Mesenchymal stem/stromal cells (MSCs) are adult, nonhematopoietic, multipotent progenitor cells, originally isolated from the bone marrow, which are traditionally characterized in vitro by their plastic adherence, trimesenchymal differentiation, and expression of a panel of distinguishing surface markers. Endogenous MSCs exist in most tissues, including the central nervous system. Endogenous MSCs were identified as a stromal component of the brain tumor microenvironment, suggesting an innate ability of MSCs to home to tumor tissue and to play a trophic role in brain tumor biology. It has been suggested that exogenously grown MSCs, derived from the bone marrow or from adipose tissue, may be useful in the treatment of cancer, because they can home to tumors and deliver therapeutic molecules. MSCs are especially useful to treat glioblastoma (GBM), the most common and most deadly primary adult brain tumor, because they can potentially cross the blood-tumor barrier and localize to GBMs after systemic injection. Here we describe the ability of exogenous MSCs to home to brain tumors and ways to exploit MSCs as therapeutic delivery vehicles. We also discuss the controversy surrounding the natural role of endogenous MSCs in the development and progression of GBM. Finally, we discuss current clinical trials of MSCs and their future prospects for GBM therapy.