FER kinase governs invasive tumor growth through dynamic control of oncogenic growth factor receptor activity

EGFR antagonism using monoclonal antibodies remains the only approved and targeted first line treatment option for non-resectable head and neck squamous cell carcinoma (HNSCC), yielding a modest 13% response rate. While it is clear that alternative growth factor receptor (GFR) signals govern refractory behavior towards EGFR antagonism, it remains unknown which upstream mechanisms control subcellular GFR activation. Here, we show that FER, a non-receptor tyrosine kinase, controls invasive tumor growth through dynamic GFR activation and recycling. Using patient derived organoid (PDO) models HNSCC we demonstrate that FER is essential for invasive growth in collagen extracellular matrix (ECM) networks. We show that inactivation of FER impairs growth factor dependent phosphorylation of EGFR-Y1068 and MET-Y1234/5. Additionally, FER controls ligand dependent endocytic recycling, and endocytic velocity, implying multifactorial functional regulation of proximal receptors during HNSCC invasion. Loss of function experiments using either genetic intervention or a FER PROteolysis-TArgeting Chimera (PROTAC) strategy in PDO-based xenograft mouse models, demonstrate that FER is essential for invasive growth and metastasis of HNSCC. Finally, we demonstrate direct clinical relevance by showing that FER expression levels correlate with poor survival in HNSCC patients. In sum, we conclude that FER is a master regulator of HNSCC invasive growth and metastasis, and nominate FER as a prominent candidate for targeted clinical intervention in HNSCC patients. Overall design: Single-cell mRNA sequencing was performed on a tongue squamous cell carcinoma patient derived organoid line (T4), cultured in a collagen type-I (invasive) matrix in the absence (dox neg) or presence of doxycyline to induce a FER knockdown (dox pos).