ZFX and Familial prostate cancer: To gain insight into possible mechanisms by which ZFX might activate transcription, we used transient transfection with siRNA to knock down the levels of ZFX in C4-2B prostate cancer cells and identified 1271 genes whose expression decreased and 1249 genes whose expression increased upon reduction of ZFX levels in C4-2B cells (FDR <0.05, fold change >1.5) (Fig. 3B; Supplemental Table S4A).