PTCH1 and skin basal cell carcinoma: On the other hand, genetic inhibition of the tumor suppressor Patched 1 (PTCH1) using Ptch1+/− mice or expression of mutant GLI family zinc-finger 2 (GLI2, also known as glioma-associated oncogene family zinc-finger 2) using Rosa26-LSL-rtTA; tetO-GLI2ΔN mice demonstrated a significant contribution of keratin 15 (KRT15), keratin 19 (KRT19) and leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5)-positive hair follicle stem cells in BCC development11–13.