FTH1 and osteosarcoma: We co-expressed nucleophosmin-1 (NPM1) fused to SspB (NPM1–mCherry–SspB), together with iLID fused to a multivalent (24-mer ferritin, FTH1) core and a nuclear localization signal (NLS–iLID–GFP–FTH1; GFP, green fluorescent protein; Fig. 2a), in human osteosarcoma (U2OS) cells.