NANOG and neoplasm: We nextperformed an immunolabeling of the stem factor Nanog in the brain of thesexenografted mice and we showed that Nanog is expressed by small cell clusters, asalready described for several stem markers in human tumor tissues,44, 45 and issignificantly increased in the 3-Gy SCM group compared with the related control(Figure 6b and SupplementaryFigure 2).