Human umbilical cord blood mesenchymal stem cells (hUCB-MSCs) have the ability to self-renew and also can differentiate into a wide range of cell types. However, many clinicians and scientists fear that even these very useful cells might cause tumors.
To that end, Moon and colleagues from the Korean Institute of Toxicology have rigorously tested the tendency for hUBC-MSCs to cause tumors. They used a large battery of tests in living organisms and in culture. hUCB-MSCs were compared to MRC-5 and HeLa cells. MRC-5 cells are known to have no ability to cause tumors and HeLa cells have a robust ability to form tumors, and therefore, constitute negative and positive controls,
To evaluate the ability of cells to cause tumors, Moon and others examined the tendency of these cells to grow without being attached to a substratum. This is a hallmark of tumor cells and is called “anchorage-independent growth” (AIG). To assess AIG, the cells were grown in soft agar, which is a standard assay for AIG. hUCB-MSCs and MRC-5 cells formed few colonies in soft agar, but HeLa cells formed a greater number of larger colonies. This indicated that hUCB-MSCs and MRC-5 cells do not show AIG, a common trait of tumorigenic cells.
The next assay implanted these cells into live laboratory animals. hUCB-MSCs were implanted as a underneath the skin of BALB/c-nu mice (nasty creatures – they bite). All the mice implanted with hUCB-MSCs and NRC-5 cells showed any sign of tumors. Both gross and microscopic examination failed reveal any tumors. However, all mice transplanted with HeLa cells developed tumors that were clearly derived from the implanted cells.
These experiments, though somewhat mundane, rigorously demonstrate that hUCB-MSCs do not exhibit tumorigenic potential. This provides further evidence of these cells clinical applications.
The paper appeared in Toxicol Res. 2016 Jul;32(3):251-8. doi: 10.5487/TR.2016.32.3.251.