Ch55 inhibits squamous cell differentiation of rabbit tracheal epithelial cells by inhibiting type I transglutaminase activity (EC50 = 0.02 nM) and increasing cholesterol sulfate levels (EC50 = 0.03 nM). Ch55 also induce differentiation of embryonic carcinoma F9 cells and melanoma S91 cells (EC50s = 0.26 and 0.5 nM, respectively), and inhibits the induction of ornithine decarboxylase activity in 3T6 fibroblasts (EC50 = 1 nM).