Provided herein are recombinant expression vector systems for expression by stem cells that allow for selective elimination of stem cell-derived tumorigenic cells, while preserving stem cell-derived therapeutic cells. The systems provided herein provide a means by which modified stem cells can be safely transplanted into subjects. In exemplary embodiments, the system comprises at least two suicide genes, one of which is specifically inactivated in cells exhibiting the desired phenotype and one of which is activated when the cell comprising the recombinant expression vector system behaves similarly to or the same as a tumor cell.
