PTCH1 and breast cancer: In the transgenic MMTV-ErbB2 (HER2-positive) mouse model, ΔNp63 supports breast cancer stemness by inducing the elevation of the SHH signaling cascade, inducing the expression of Smoothened (SMO), Protein Patched Homolog 1 (PTCH1), and GLI Family Zinc Finger 2(GLI2) [77].