In order to test if the function of CHP-1 in the EGFR signaling pathway is conserved in mammals, we inactivated the CHP-1 homolog CHORDC1 in human A431 epidermoid carcinoma cells, which express high levels of the wild-type EGFR and undergo a phenotypic switch in response to EGF stimulation (Ferretti et al., 2011; Van de Vijver et al., 1991). The gene discussed is CHP1; the disease is squamous cell carcinoma.