Stanford researchers separate tumor-causing stem cells from therapeutic ones

A major obstacle to widespread therapeutic use of human embryonic stem cells is this nasty tendency for a few of them to turn "Frankenstein" on us. Out of the tens of millions of pluripotent cells used in therapy, cells that have been "programmed" by scientists to become any type of specified adult tissue, a few go rogue and become dangerous tumors called teratomas when transplanted into patients. So, researchers at Stanford University, writing in the journal Nature Biotechnology, describe a method to get rid of the cells that can become teratomas before they are used in humans.

"The ability to do regenerative medicine requires the complete removal of tumor-forming cells from any culture that began with pluripotent cells," Stanford's Irving Weissman said in a release. "We've used a combination of antibodies to weed out the few undifferentiated cells that could be left in the 10 or 100 million differentiated cells that make up a therapeutic dose."

The researchers developed an antibody, which they called anti-SSEA-5, which they injected into mice. Some of the cells responded to the anti-SSEA-5 by forming rapidly growing teratomas. That, combined with two other antibodies, completely separated the cells that could form tumors from those that are safe to use in therapy. Weissman said the same technique could also be applied to induced pluripotent stem cells, which are derived from adult skin cells.

"Because even a single undifferentiated cell harbors the ability to become a teratoma, we sought to develop a way to remove these cells before transplantation," said research associate Micha Drukker, senior author of the research, in a news release.

- read the release from Stanford University Medical Center
- and the abstract in Nature Biotechnology