The growing number of victims of "stem cell tourism," the unregulated
transplantation of stem cells worldwide, has raised concerns about the safety of
stem cell transplantation. Although the
transplantation of differentiated rather than undifferentiated cells is common practice,
teratomas can still arise from the presence of residual undifferentiated stem cells at the time of transplant or from spontaneous mutations in differentiated cells. Because stem cell
therapies are often delivered into anatomically sensitive sites, even small
tumors can be clinically devastating, resulting in
blindness,
paralysis, cognitive abnormalities, and cardiovascular dysfunction. Surgical access to these sites may also be limited, leaving patients with few therapeutic options. Controlling stem cell misbehavior is, therefore, critical for the clinical translation of stem cell
therapy. External beam radiation offers an effective means of delivering targeted
therapy to decrease the
teratoma burden while minimizing injury to surrounding organs. Additionally, this method avoids genetic manipulation or viral transduction of stem cells-which are associated with additional clinical safety and efficacy concerns. Here, we describe a protocol to create pluripotent stem cell-derived
teratomas in mice and to apply external beam
radiation therapy to selectively ablate these
tumors in vivo.