We first assessed the role of FER on endosomal formation and observed that FER-iKD in growth factor depleted HNSCC PDO cells leads to a significant increase in EEA1 signal intensity and signal accumulation, indicative of impaired recycling due to an accumulation of early endosomal vesicles in both models (Supplemental Fig. 4). Here, FER is linked to head and neck squamous cell carcinoma.