GLI1 and skin basal cell carcinoma: On the other hand, immunohistochemistry analysis revealed that Gli1(S941A)+/+ skins had the extreme hyperplasia in the keratin 5 (K5)-expressing basal cell layer, slight thickness in the keratin 10 (K10)-expressing suprabasal terminally differentiating layer, and large amount of keratin 17 (K17)-expressing hyperproliferative cells (Fig. 3j, k), resembling human superficial BCC.