To investigate which epigenetic modifiers favor breast cancer growth, we used two custom pooled, barcode (BC)-coupled shRNA libraries composed of 1204 and 1192 shRNAs (hEpi1 and hEpi2, respectively), targeting 236 epigenetic regulators (118 in hEpi1 and 118 in hEpi2, see Materials and Methods for details) and four control genes (Luciferase - LUC, KIF11, PSMA1 and RPL30, Supplementary Table S1) that were successfully used in an in vivo RNAi screen in melanoma [1]. The gene discussed is PSMA1; the disease is breast cancer.