NUCLEOLIN and neoplasm: Indeed, by using HB-19 and related multivalent Nucant pseudopeptides that present pentavalently or hexavalently the tripeptide Lysψ(CH2N)-Pro-Arg (Nucant 3, 6, 6L and 7) [43,44], we show that such surface nucleolin antagonists exert distinct inhibitory mechanisms depending on the malignant tumor cell type.