HIF1A and neuroblastoma: Similar observations were demonstrated in human neuroblastoma cell line NB1691 where, as compared to normoxia, intermittent hypoxia (1% O2, 24 h hypoxia, 24 h reoxygenation, 1, 5, or 10 cycles) suppressed cell differentiation and enhanced neural crest-like and stem-like properties in a HIF-1α dependent manner [71].