Epidermoid squamous carcinoma cell line A431 is known to express, on average, more EGFR than other cell lines of similar origin (~2 × 106 EGFR molecules per cell versus ~4 × 104 of HER2), and is highly sensitive to EGFR-targeted drugs [21, 41], but not sensitive to HER2-specific drug trastuzumab [42], Figure S5. Here, EGFR is linked to squamous cell carcinoma.