HEK293T and PC-3 cells were lysed, proteins were extracted and western blotting was performed, as previously described (13 (link)). Equal amounts of cell lysates (15 µg) were fractionated by size on a 10% SDS-polyacrylamide gel (Beijing Solarbio Science & Technology Co., Ltd., Beijing, China) and transferred onto polyvinylidene fluoride membranes (EMD Millipore, Billerica, MA, USA). The membrane was blocked with tris-buffered saline-Tween with 5% non-fat milk at room temperature for 1 h. Samples were then incubated with antibodies against the following proteins: YY1 (CST-2185S; 1:2,000; Cell Signaling Technology, Inc., Danvers, MA, USA), CDK6 (D155263; 1:1,000; Sangon Biotech Co., Ltd., Shanghai, China) and β-actin (MABT825; 1:10,000; EMD Millipore) at 4°C overnight. Subsequently, horseradish peroxidase-labeled goat anti-rabbit (ab6721; 1:10,000; Abcam, Cambridge, MA, USA) and goat anti-mouse (ab6789; 1:10,000; Abcam) secondary polyclonal antibodies were added, respectively, followed by immobilon enhanced chemiluminescence (EMD Millipore).