Our results are not only consistent with previous findings that GLI1 phosphorylation at certain sites regulates its stability, localization, and transcriptional activity20–28, but also identify the Ser937/Ser941 phosphorylation as a determinant mechanism controlling SHH signaling as well as the incidence and severity of MBSHH and BCC. Here, GLI1 is linked to skin basal cell carcinoma.