As shown in Supplementary Fig. 4, the TfR1 antibody treatment caused a 67% decrease in the FITC fluorescence accumulation in BSA-Man-Ft-FITC@Lap-treated 4T1 cells under pH 6.5 (Supplementary Fig. 4a, b), validating our hypothesis that the Fn units could serve as tumor-targeted carriers for selective Lap delivery. The gene discussed is TFRC; the disease is neoplasm.