Gutierrez-Aranda, Ramos-Mejia, Bueno et al. 1569 Figure 1. Human iPSCs form teratomas faster and with higher efﬁciency than hESCs regardless the site of injection. (A): Car- toon summarizing the experi- mental design. (B): Table summarizing the efﬁciency, la- tency, and histological analysis of the teratomas developed from both human ESCs and human iPSCs upon either subcutaneous or intratesticular transplantation. (C): Histological analysis of ter- atomas derived from both hESCs and iPSCs upon subcuta- neous or intratesticular trans- plantation reveal similar tissue composition. The presence of mesodermal tissues is deﬁned by teratoma sections containing car- tilage and positive for both smooth muscle actin and mela- nin. The presence of ectodermal tissues was scored as teratoma sections that stained positive for b-III tubulin and presence of neural rosettes. Endoderm was deﬁned as teratoma sections that stained positive for a-fetoprotein and pan-cytokeratin. The study was approved by the Andalusian and Spanish Embryo and Cellu- lar Reprogramming Ethical Institutional review Board. Ani- mal protocols were approved by the Local University Hospital Council On Animal Care and Experimentation. Abbreviations: ESCs, embryonic stem cells; iPSCs, reprogrammed/induced pluripotent stem cells. differentiation but also for cancer researchers developing in vivo models for germ cell tumors. c´ıa, by Proyectos de Investigacio´n en Salud PI-002 from Junta de Andaluc´ıa, and by the FIS (CP07/00065 and PI08171). ACKNOWLEDGMENTS We thank Prof. Paco Nogales at The Department of Pathology, University of Granada for his helpful assistance with diagnosis and histology. P.M.’s group is supported by: CICE (P08-CTS-3678 to P.M.) de la Junta de Andaluc´ıa; the FIS to P.M. (PI070026), to C.B. (CP07/0059), and to P.J.R. (CP09/0063); the MINICC to P.M. (PLE-2009-0111) and the Marie Curie IIF to V.R.-M. (PIIF- GA-2009-236430). J.L.G.-P.’s group is supported by ISCIII-CSJA (EMER07/056), by a Marie Curie IRG action (FP7-PEOPLE- 2007-4-3-IRG), by CICE (P09-CTS-4980) from Junta de Andalu- www.StemCells.com DISCLOSURE OF POTENTIAL CONFLICTS OF INTEREST The authors indicate no potential conﬂict of interest. REFERENCES 1 Bueno C, Catalina P, Melen GJ et al. Etoposide induces MLL rear- rangements and other chromosomal abnormalities in human embryonic stem cells. Carcinogenesis 2009;30:1628–1637.