Stem cells have recently received a great deal of attention for their clinical and therapeutic potential to treat human disease and disorders. For instance, neural stem cells expressing a suicide gene which can concert prodrugs to their active metabolites may have great tropic and therapeutic potential for brain tumors, i.e., medulloblastoma and glioma. We are currently interested in therapeutic potential of these genetically engineered stem cells (GESTECs) to selectively target invasive tumors, i.e. ovarian, endometrial, breast, and lung cancer which can have a great impact on human and animal health. Thus, in this review we summarize the therapeutic potential of GESTEC, developed by us, and the putative mechanism(s) underlying their therapeutic and tropic potential in expressing suicide genes which can convert prodrugs to their active metabolites and in selectively targeting invasive tumors.