Mesenchymal stem cells, cancer challenges and new directions.

Therapeutic use of multipotent mesenchymal stromal stem cells (MSC) is a promising venue for a large number of degenerative diseases and cancer. Their availability from many different adult tissues, ease of expansion in culture, the ability to avoid immune rejection and their homing ability, are some of the properties of MSCs that make them a great resource for therapy. However, the challenges and risks for cell-based therapies are multifaceted. The blessing of cell culture expansion also comes with a burden. During in vitro expansion, stem cells experience a long replicative history and therefore, become subjected to damage from intracellular and extracellular influences. As previously shown cells that are manipulated to obtain an expanded replicative potential are prone to spontaneous transformation in culture. These manipulations help bypass the naturally built-in controls of the cell that govern the delicate balance between cell proliferation, senescence and carcinogenesis. Because of this, there is a risk for patients receiving stem cells that are in vitro expanded. Whether these cells are genetically engineered or harbouring xenogenic compounds, they cannot truly be considered "safe" unless the cells are closely monitored. In the present communication, we will focus on the therapeutic potential of the human mesenchymal stem cells (hMSC) with special focus on their use in cancer therapy. We will consider different mechanisms, by which stem cells can maintain telomeres and thereby the cell's ability to be expanded in vitro, and also focus on a new therapeutic venue that utilises hMSCs as delivery vehicles in innovative new cancer treatments.