CD55 and neuroblastoma: HIF-2α protein overexpression was evaluated in normoxic conditions as we have previously shown HIF-2α stability in normoxic NB cells.22 In NB cells HIF-2α expression is sufficient to enhance stem features, whereas CD55, although described as a putative marker of cancer stem cells,19 has not influenced the stem-like properties of NB cells so far in vitro.