LAPTM4B and cancer: Fig. 3A shows the confocal images of DBT-2EEGIHGHHIISVG–treated HepG2 cancer cells at 0 °C. It is found that intense fluorescence signals are observed on the surface of the cancer cells, which is consistent with Zhang’s results15. This verifies that DBT-2EEGIHGHHIISVG specifically binds to LAPTM4B proteins on the membranes of HepG2 cancer cells. It is noted that by contrast, no detectable autofluorescence is observed from the cells without probe treatment under the same imaging condition (Supplementary Fig. S9).