CD55 and neuroblastoma: CD55 might be regulated by HIF, as a HIF-functional binding site has been identified on the CD55 promoter.20 In addition, in NB, HIF-1α protein staining is related to hypoxic areas, whereas HIF-2α protein staining is extended to perivascular areas and is a sign of poor prognosis.21 To verify whether CD55 correlates with HIF-2α staining we hybridized the tissue microarray (TMA) with HIF-2α-specific antibody (Figure 1a).