The present invention relates to eukaryotic mammalian host cells comprising an artificial endosymbiont belonging to the class ±-Proteobacteria, wherein the host cell is selected from the group consisting of human cancer cells, inducible pluripotent stem (IPS) cells, hematopoietic stem cells, neural stem cells, epidermal neural crest stem cells, mammary stem cells, intestinal stem cells, mesenchymal stem cells, olfactory adult stem cells, testicular cells, and human cells found in the circulatory system.
