In the search for endocytic properties that may be exploited to predict responsiveness to gefitinib, Nishimura et al. [50] used confocal immunofluorescence microscopy to compare the endolysosomal distribution of fluorescent EGF-EGFR complexes in gefitinib-sensitive NSCLC PC9 cells expressing the D746–750 EGFR mutant and gefitinib-resistant QG56 cells expressing wtEGFR. Here, EGF is linked to non-small cell lung carcinoma.