Immunohistological antibody staining using anti-GLI1 C68H3 antibody from Cell Signaling, which has been described to work on skin tumor samples (Tanese et al., 2018), show that cSCC are either completely positive (3/10) or negative (4/10) for GLI1, whereas others show both GLI1-positive and GLI1-negative tumor areas (3/10) (Supplementary Figure S2C). Here, GLI1 is linked to skin squamous cell carcinoma.