Figure 2. Celastrol-induced CIP2A degradation is mediated by the ubiquitin–proteasome pathway. (A, B) Effects of 50 ug/ml cycloheximide (CHX) alone or in combination with 5 μM celastrol on CIP2A expression were evaluated by western blotting in AGS and BGC-823 cells. (C, D) Western blotting analyzed CIP2A expression in AGS and BGC-823 cells preincubated with PS-341 (100 nM) and MG-132 (10 μM) for 2 h followed by treatment of celastrol (5 μM) for additional 6 h.