A cohort of genes associated with embryonic stem (ES) cell behaviour, including 
NANOG, are expressed in a number of human cancers. They form an ES-like 
signature we first described in glioblastoma multiforme (GBM), a highly invasive 
and incurable brain tumour. We have also shown that HEDGEHOG-GLI (HH-GLI) 
signalling is required for GBM growth, stem cell expansion and the expression of 
this (ES)-like stemness signature. Here, we address the function of NANOG in 
human GBMs and its relationship with HH-GLI activity. We find that NANOG 
modulates gliomasphere clonogenicity, CD133(+) stem cell cell behavior and 
proliferation, and is regulated by HH-GLI signalling. However, GLI1 also 
requires NANOG activity forming a positive loop, which is negatively controlled 
by p53 and vice versa. NANOG is essential for GBM tumourigenicity in orthotopic 
xenografts and it is epistatic to HH-GLI activity. Our data establish NANOG as a 
novel HH-GLI mediator essential for GBMs. We propose that this function is 
conserved and that tumour growth and stem cell behaviour rely on the status of a 
functional GLI1-NANOG-p53 network.