Effects of proteasome inhibitors, antioxidants, cannabinoid receptor antagonists, and cannabinoid receptor knockdown on WIN-mediated downregulation of Sp proteins. SW480 cells were pre-treated with lactacystin (10 μM) or gliotoxin (3 μM) (A), DTT (1 mM) or GSH (5 mM) (B), AM251 (4 μM) and AM630 (5 μM) (C) for 45 min followed by treatment with 7.5 μM of WIN for 48 hr, and whole cell lysates were analyzed by western blots. (D) Cells were transfected with siRNAs against CB1 and CB2 receptors, followed by treatment with WIN for 48 hr, and whole cell lysates were analyzed by western blots. iLamin was used as a control oligonucleotide.