PTCH1 and neoplasm: Although maximal Rho activity required several exchange factors, Arhgef17, also known as Tumor Endothelial Marker 4, was the most significantly enriched at the protein level in mouse resistant BCC tumors with nuclear MRTF, generated from transgenic mouse model Ptch1+/−;K14-creER;p53fl/fl43 (Fig. 4e, f).