EGF and skin basal cell carcinoma: Since the high expression of EGF and EGFR seems to play a very important role in cSCC (Figure 1; Supplementary Figure S1E) (Canueto et al., 2017), we hypothesized that EGFR signaling may regulate GLI activity via the RAS/MEK/ERK axis like in BCC (Schnidar et al., 2009; Eberl et al., 2012).