Tumorigenicity as a clinical hurdle for pluripotent stem cell therapies.

Human pluripotent stem cells (PSCs) are a type of cell that can generate various types of tissues as well as copies of themselves (through self-renewal). Thus, these cells are a leading candidate for cell-based therapies, where they might be used to replace diseased or damaged tissue. In fact, recent advances have culminated in the first-in-human clinical trials of PSCs by Geron, Advanced Cell Technology, and the Kobe Center for Developmental Biology. These groups are testing PSCs for the treatment of spinal cord injury and macular degeneration (a cause of loss of vision). Despite the therapeutic promise of PSC, a crucial hurdle for their clinical use is their potential to form tumors when they are place in the body. In this Perspective, we present an overview of the mechanisms by which human PSC–based therapies may cause tumors, and we discuss current advances in addressing this challenge.