Valproic acid sodium salt (VPA) was purchased from Sigma (St. Louis, MO). Antibodies to SSTR2 (Cat. No.: sc-11609), p21 (sc-756), p63 (sc-8343), histone 4 (H4, sc-10810), HDAC4 (sc-11418), acetylation of histone 4 (AcH4, sc-8660-R), HES1 (sc-25392) and β-actin (sc-1616-HRP) were purchased from Santa Cruz Biotechnology (Santa Cruz, CA), with Notch1 (Cat. No.: 4380) from Cell Signaling Technology (Danvers, MA). The plasmids are the kind gifts from Dr. Wu (University of Florida). The cytotoxic CPT-SST was synthesized in our laboratories 38 (link).