The impact of Mesenchymal Stem Cells and their secretome as a treatment for gliomas

In recent years, we have witnessed a significant increase in the amount of studies using Mesenchymal Stem Cells (MSCs) for cancer therapy, mostly as vectors for drug or gene delivery strategies. This is because of their intrinsic capacity of homing into tumor niches. However, the interactions between MSCs themselves and tumor cells is not fully understood, with contradictory results frequently being observed regarding their effects on cancer cell invasion and proliferation. This poses an important question of safety in respect to the application of these cells. The source of the MSC population used, as well as the type of cancer cells under study might strongly influence this interaction. Moreover, differences in isolation protocols, culture media compositions, time of culture and conditioned media collection, or even timing and mode of MSCs administration to in vivo models of cancer may also affect the interaction MSC-tumor cells. In this review, we drive our focus into malignant brain tumors, particularly gliomas, one of the deadliest forms of cancer. Moreover, we look with some detail into different studies using MSCs as a treatment for brain tumors and compare them, highlighting the main deviations and similarities among them.