Fig. 5. 441 induces internalization and degradation of HER2 clusters.

a Qualitative confocal microscopy studies in four different cell lines of different compounds 4 h posttreatment. Continuous membrane staining and retained membrane localization is seen for all mAbs and their combination, expect 441, which is clustered on the surface and internally in lysosomes. Human Fc regions are colored magenta, the lysosomal marker LAMP1 in green and DAPI as nuclear stain in blue. b Internalization and degradation were quantitatively resolved in a time-dependent manner using the recently developed SPIDA protocol³⁹ (mean plus error bar SD). 441 led to distinct internalization as early as after 1 h, and thereafter internal HER2 was continuously degraded. In contrast, the combination treatment of mAbs leads to a slow gradual decrease of surface HER2, consistent with recycling inhibition without prior intracellular accumulation. Source data are available in the Source Data file.