Moreover, it has been shown that in A431 cells (epidermoid carcinoma cells that express EGFR) as well as HEK293 cells co-expressing GPCR kinase-2 and EGFR, EGFR activation by EGF led to a downregulation of the opioid receptor as a consequence of its interaction with G proteins, which activated GPCR kinases [91,104]. Here, EGFR is linked to squamous cell carcinoma.