2.3. Protein Extraction and Western Blotting

Stably transfected MCF-7 and MDA-MB-231 cells or peptide-treated wild type MCF-7 and MDA-MB-231 cells were collected and lysed using an RIPA buffer. The BCA (Pierce kit #23225) method was used for protein quantitation of the whole cell lysates. The whole cell lysates were subjected to SDS-PAGE and Western blotting. Specific proteins were probed using anti-Sin3A (cat#sc-5299, Santa Cruz Biotechnology, Dallas, TX, USA), anti-RARα (cat# sc-515796), anti-RXRα (cat#sc-515929, Santa Cruz Biotechnology, Dallas, TX, USA) and anti-RARβ (cat# sc-56864 Santa Cruz Biotechnology, Dallas, TX, USA), followed by incubation with HR0 conjugated anti-mouse antibodies (cat# 7076, Cell Signaling technologies, Denvers, MA, USA). The bands were visualized by chemiluminescence.